Final Year Project - Developing A Plastic Bottle Solar Collector

 

 

Title page

Developing a Plastic Bottle Flat-Plate Solar Collector

Nizamuddin Patel P15219444 BEng Mechanical Engineering July 2018

Supervisor: Dr Muyiwa Oyinlola Institute of Energy and Sustainable Development

PATENT PENDING

 

 

Abstract This report follows the research and development of a third-year mechanical engineering project from inception to completion. The project involved creating a solar thermal collector made from plastic bottles into an actual scale model for testing. A 3D CAD model is created and simulated before the creation of a physical model to ensure there is less waste of resources. The final outcome of this project is to analyse the results and see the performance of a plastic bottle solar thermal collector. The report begins by introducing the project area of a solar thermal collector in general terms and moves on to discuss basic techniques applied to this specific  project discussing the th e design and implementation of the model. It discusses the simulation process of the main parts of the model; the problems encountered and what has been done to solve these problems. Lastly, the report discusses the possibility of future work that can be applied to this project in order to maximise the performance of the plastic bottle solar thermal collector.

 

 

ENGD3000 –  Individual  Individual Project

Dedication Dedicated to the 767 million people who still live in extreme poverty and cannot afford to heat water for hygiene purposes.

 Nizamuddin Patel

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Acknowledgements I would firstly like to thank God for giving me strength and motivation to complete this study.

This dissertation would not have come into being without the guidance of my supervisor Dr Muyiwa Oyinlola. He has been very supportive and his feedback has greatly improved my work. His resources and sensors have been of great use and I also thank him for directing me to ebooks and online websites involved in the uses of solar thermal collectors; all of whom I have learned much from.

Paul Dean and Vijay from the De Montfort University Mechanical Lab have been of great help in the manufacture and setting up of my experiment, for which this report would not have had any concrete base for discussion.

My final and most important acknowledgements go to my family especially to my mother, who have been really supportive.

This project report should be cited as:

 Nizamuddin, P. (2018).  Developing a plastic bottle solar thermal flat plate collector . 2nd ed. Leicester, United Kingdom: Institute of Engineering and Sustainable Development, De Montfort University.

 Nizamuddin Patel

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Contents Title page.............................................................. .................................................................................... ............................................. ................................... ............i  Abstract ............................................. .................................................................... ............................................. ............................................. .............................. .......ii  Dedication ............................................. ................................................................... ............................................ ............................................. ......................... .. iii  Acknowledgements .......................................... ................................................................ ............................................ ..................................... ...............iv i v   

Table of figures ................................. ....................................................... ............................................. .............................................. .......................... ... viii Table of tables ....................................... ............................................................. ............................................ ............................................. .......................... ... ix  1.  Introduction ........................................... .................................................................. ............................................. ......................................... ...................1  1.1 

Background ........................................... ................................................................. ............................................ .................................. ............ 2 

1.2 

Aims ........................................... ................................................................. ............................................ ............................................. .......................2 

1.3 

Objectives .......................................... ................................................................ ............................................ ...................................... ................ 2 

2.  Literature Review ............................................. ................................................................... ............................................ .............................. ........ 3  2.1 

Initial design inspiration ..................................................... ............................................................................ ........................... .... 3 

2.2 

Materials to be used as solar radiation reflectors/heat r eflectors/heat retainers ....................4 

2.3 

Water piping pipi ng to be used in the solar collector coll ector ........................ ............................................... .......................5 

2.4 

Geometry of the solar collector .......................................... ................................................................. ........................... .... 6 

2.5 

The most common plastic pla stic bottle bo ttle used us ed in Nigeria .......................... .......................................... ................ 6 

2.6  Fundamentals of flat plate solar collectors including performance indicators. .......................................... ................................................................ ............................................ ............................................. ........................... .... 7  2.7  The need for hot water and the average volumetric flow rates of water in  Nigeria ........................................... .................................................................. ............................................. ............................................. .............................. ....... 7  3.  Methodology ......................................... ............................................................... ............................................. .......................................... ...................9  3.1 

Material ......................................... ............................................................... ............................................. .......................................... ...................9 

3.2 

Designs .......................................... ................................................................. ............................................. ....................................... .................11  

3.2.1 

Computed Aided Design drawings (CAD) ..................................... .......................................... ..... 12 

3.2.2 Thermal simulations ........................................... .................................................................. ....................................... ................13  3.2.3 Compression test .................................. ........................................................ ............................................. ................................ ......... 13  3.3 

Manufacture of solar so lar thermal collector ..................................................... ....................................................... .. 14 

3.4 

System description ........................................... .................................................................. ........................................... ....................16 

4.  Theoretical calculations ........................................... .................................................................. ........................................... ....................17  4.1 

Surface Area Calculation .............................. .................................................... ............................................. ......................... .. 17 

4.2 

Heat coefficient of fluid (h) ............................................. .................................................................... ............................ ..... 17 

4.3 

Heat flux equation (Qtop) ......................................... ............................................................... .................................... ..............18 

5.  Experiment ............................................ ................................................................... ............................................. ....................................... .................19  5.1 

Apparatus used .......................................... ................................................................ ............................................ ............................ ...... 19 

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Analysis of Experimental Results ...................................... ............................................................ ......................... ... 19 

6.  Discussion .......................................... ................................................................ ............................................ ........................................... .....................21  6.1 

Differences between calculated and experimental ex perimental results ........................... ........................... 21 

6.1.1 

Difference in heat coefficient of fluid flu id (h) ............................................ ............................................ 21 

6.1.2 

Difference in heat flux factor (Qtop) ............................................ ..................................................... ......... 22 

 

 

6.2 Effect on parameters when water input flow is adjusted ............................. ............................. 23 6.2.1  Flow at 6 L/m ................................. ....................................................... ............................................. ................................ ......... 23  6.2.2 

Flow at 4 L/m ................................. ....................................................... ............................................. ................................ ......... 24 

6.2.3 

Flow at 2L/m ................................................. ........................................................................ ....................................... ................26 

6.2.4  (Re).

Relationship between Nusselts number (Nu) and Reynolds number 27 

6.2.5 

Conclusion ............................................ .................................................................. ............................................ ......................... ... 29 

6.3 

Impact on collector parameter when a reflector is added ............................ ............................ 30 

6.3.1 

Solar thermal collector without cling film fi lm ............................. ........................................... .............. 30 

6.3.2 

Solar Thermal collector with cling c ling film fi lm ............................................. ............................................... .. 35 

6.3.3  6.3.4 

Comparison of collector with and without a reflector ......................... 40  Conclusion ............................................ .................................................................. ............................................ ......................... ... 46 

6.4 

Performance of thermal ther mal collector coll ector when fluid is throttled thr ottled ............................ ............................ 46 

6.5 

Reliability of the experiment ........................................... .................................................................. ............................ ..... 47 

6.5.1 

Errors .......................................... ................................................................ ............................................ .................................... .............. 47 

6.5.2 

How errors can be b e minimised minimi sed for next nex t time t ime ......................................... .........................................48 

7.  Conclusion ............................................ ................................................................... ............................................. ....................................... .................49   7.1 

Future work ........................................... ................................................................. ............................................ ................................ .......... 51 

7.1.1 

Replacing bottle air with water ........................................... ............................................................ .................51 

 

 

7.1.2 7.1.3 

Performance of solar thermal collector at times of no sunlight (night) 51 Rotating the solar collector collect or 90º anti-clockwise and re-run tests .......... 52 

7.1.4 

Can the bubble bub ble wrap replace repl ace the plastic pl astic bottle.................... bottle ..................................... .................52 

7.1.5 

Using a thinner hose pipe .......................... ................................................ ........................................... .....................52 

References ............................................. ................................................................... ............................................ ............................................. ......................... .. 53  Appendix ........................................... .................................................................. ............................................. ............................................. .............................. ....... I  8.  Appendix ............................................ .................................................................. ............................................ ............................................. ....................... I  8.1 

Calculations ........................................... ................................................................. ............................................ .................................. ............ I 

8.1.1 

Average temperature values .......................... ................................................ ......................................... ................... I 

8.1.2 

Mass flow rate .................................... .......................................................... ............................................. .............................. ....... I 

8.1.3 

Heat transfer of fluid (Qfluid) ........................................... .................................................................. ....................... I  

 Nizamuddin Patel

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ENGD3000 –  Individual  Individual Project 8.1.4 

Heat flux factor (Qtop) .................... .......................................... ............................................. .................................. ........... I 

8.1.5 

Heat coefficient co efficient of fluid flu id (h)................................................. (h)................................................................... .................. II 

8.1.6 

............................................................. .................. II   Collector efficiency factor (F’)  ...........................................

8.1.7 

Collector overall loss coefficient (U L) ............................................ .................................................. ...... II  

8.1.8 

Heat removal factor (FR ) .......................................... ................................................................. ............................ .....III  

 

 

Collector flow factor (F’’) ..................... 8.1.9 ........................................... ............................................. ......................... ..IV 8.1.10   Nusselt number (Nu) ............................................ ................................................................... ................................ .........IV 

8.1.11  8.2 

Reynolds number (Re) ............................................. .................................................................... ............................ .....IV 

Experimental data .................................................... ........................................................................... ..................................... .............. V 

8.2.1 

Water flow at 4L/m 4 L/m with cling film ........................................ ...................................................... .............. V 

8.2.2 

Flow at 4L/m without cling film ................................. ....................................................... ...................... VIII 

8.3 

Compression test data ................................... ......................................................... ............................................. ......................... ..XI 

Glossary ............................................. ................................................................... ............................................ ............................................. ......................... .. 12 

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Table of figures Figure 1: Most common configurations configu rations of water piping pipin g in a solar collector ............... 5  Figure 2: (on left) plastic plasti c bottle used in design of solar s olar water heater ........................ ........................ 10  Figure 3: CAD drawings showing the final proposed design of the thermal solar collector ............................................. .................................................................... ............................................. ............................................. ............................ ..... 12  Figure 4: Thermal analysis of CAD drawing drawin g ............................................ ............................................................. .................13  Figure 5: Compression test using Instron 3367 33 67 machine machi ne ........................................... ...........................................13  Figure 6: Solar thermal collector coll ector with sensors sen sors and halogen light on ......................... ......................... 14  Figure 7: Solar thermal collector without sensors............................. s ensors.................................................... ......................... .. 14  Figure 8: Solar thermal collector sensor placement .......................................... ................................................... ......... 15  Figure 9: Experimental calculations showing mass flow rate, Qwater, temperature change, heat transfer coefficient and a nd Nusselt number .................................. ............................................... ............. 19  Figure 10: Experimental values for q, Qtop, Ta, Heat removal factor....................... 20  Figure 11: Temperature Temper ature vs Time for flow 6L/m with cling cli ng film ............................... ............................... 23  Figure 12: Temperature Temp erature vs time for water flow at 4L/m with cling film ...................24  Figure 13: Experimental Ex perimental results result s from water flow at 2L/m 2 L/m with cling film ................26  (Left) Figure 14: visual representation of direction and reaction of fluid flow in relation to Reynolds number ............................................... ...................................................................... ....................................... ................28  Figure 15: Relationship between Nu, Re and mass flow flo w rate .................................... ....................................28  Figure 16: Experimental Ex perimental results resu lts from water wate r flow of 4L/m without a reflector .......... 30  Figure 17: Collector efficiency vs hear coefficient of fluid (h) for water flow of 4L/m without cling film ......................................... ............................................................... ............................................. ........................................ .................31  Figure 18: Heat removal factor vs heat coefficient of fluid for water flow at 4L/m without cling film ......................................... ............................................................... ............................................. ........................................ .................32  Figure 19: Heat removal factor vs mass flow rate for water flow at 4L/m without cling film ........................................... .................................................................. ............................................. ............................................. ............................ ..... 33  Figure 20: Flow factor vs Time at water flow at 4L/m without cling film ................34  Figure 21: Temperature Temper ature vs Time at water flow at 4L/m 4 L/m with cling film fi lm ................... ................... 35  Figure 22: Visual representation of solar radiation waves passing through a plastic  bottle ........................................... ................................................................. ............................................ ............................................ .................................... .............. 36  Figure 23: Collector efficiency vs heat coefficient of fluid at water flow of 4L/m with cling film .................................................. ........................................................................ ............................................ .................................... .............. 38  Figure 24: heat removal factor vs heat coefficient of fluid at water flow of 4L/m with cling film ........................................... .................................................................. ............................................. ............................................. ............................ ..... 38  Figure 25: Heat removal factor vs mass flow rate at water flow of 4L/m with cling film ............................................. ................................................................... ............................................ ............................................ .................................... .............. 39  Figure 26: Flow factor vs time for water flow at 4L/m with cling film fil m ..................... ..................... 39  Figure 27: Collector efficiency factor vs heat coefficient of fluid for experimental results with and an d without with out of o f cling cli ng film fi lm ................................. ....................................................... ....................................... .................43  Figure 28: Heat removal factor (FR) vs heat coefficient of fluid (h) between the collector with and an d without witho ut a reflector ....................................................... ........................................................................ .................44  Figure 29: Flow factor (F'') vs heat coefficient of fluid (h) between the collector with and without reflector ............................................ .................................................................. ............................................ ................................ .......... 45  Figure 30: Compression test of plastic bottle ............................................ ............................................................. .................XI  Figure 31: 31 : Compression Compr ession test of PVC pipe ............................................ ................................................................. .....................XI   Nizamuddin Patel

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Table of tables Table 1: Required amount amoun t of water needed for each sector ......................................... .........................................8  Table 2: Materials used us ed and their thei r purpose in the th e solar collector...................... collector ................................ .......... 11  Table 3: List of sensors used and their the ir description descr iption ........................................... .................................................... ......... 15  Table 4: Experimental results of temperatures from different segments at water flow of 4L/m without reflector ............................................ .................................................................. ............................................ ......................... ... 30  Table 5: Difference in temperature split in segments with water flow at 4L/m with cling film ........................................... .................................................................. ............................................. ............................................. ............................ ..... 36  Table 6: Temperature differences by segment between collector without cling film and with cling film .......................................................... ................................................................................ ........................................... .....................40  Table 7: Difference in water temperature between when a solar collector has a reflector and without ............................................ .................................................................. ............................................ ................................ .......... 41 

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1.  Introduction  Nigeria and indeed most developing develo ping countries, supplies sup plies of non-renewable energy or grid-connected electricity are either unreliable, unavailable or for most rural inhabitants too expensive. Over 70% of Nigerians live in semi-urban and rural areas; these people face the most challenges to produce hot water in their homes. Healthcare in Nigeria is said to be amongst the poorest in the world, which suggests that good hygiene is a challenge in the country. The main use of domestic hot water is for hygiene purposes such as washing, bathing and cooking. The traditional and most popular method in which Nigerians heat their water is by using firewood; however the ecological hazards associated with deforestation due to the continuous felling of trees is concerning as 3.6% of present forests and woodlands are being destroyed yearly, and only 10% of the reforestation rate is being conducted. The next alternative is coal, which is abundant in Nigeria but it has an incomplete combustion which produces toxic emissions like carbon monoxide and is suspected to be the main cause of respiratory diseases and conjunctivitis amongst women that cook daily with these fuels. Under these conditions, solar energy water heaters appear increasingly attractive as viable alternatives. This complicated situation is part of the inspiration of this project in which this dissertation aims to create an affordable solar thermal collector which will use renewable energy to heat water in order to raise the countries health hygiene and therefore creating a healthier workforce, which will evidently boost the country’s

economy.

 

 

ENGD3000 –  Individual  Individual Project

1.1 Background A solar thermal collector collects heat by absorbing solar radiation using sunlight. A typical flat plate collector consists of a metal box with a plastic cover (glazing) on top and dark coloured absorbers at the bottom. In between are tubes where water  passes. The space around the t he pipes tends to be isolated iso lated to minimise heat loss. These simple yet effective devices provide hot water to mainly residential buildings. This typical flat plate collector has been modified by Jose Alano to use cheap readily available materials such as plastic bottles. The concept remains the same and the temperature of the water should rise. 1.2 Aims This project aims to develop a plastic bottle solar thermal collector. This will be using Jose Alano’s design as a base and adjusting it to maximise its performance.

The solar collector I intend to produce will also be scaled down for it to be used for a single house instead of a complex of houses. For this project to be a success the design that is used, should use a low cost, readily available upcycled resources to create a plastic bottle solar water heater that will heat up water in line with the calculations. The project aims to develop a low cost solar thermal collector using easily accessible upcycled materials.

1.3 Objectives The main objectives of the study are:   To determine which materials will be suitable for the low cost solar thermal



heater   Compare and choose which type of solar collector piping is best for its



 purpose   To optimise the design of the solar collector to ensure it is easy to



manufacture.   To characterise the performance of the solar collector



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Literature Review 2.1 Initial design inspiration In order for anything to be designed, there has to be an inspiration of some sort. Some artists rely on nature, whilst others use life events or role models to shape their  product. In the case of this thi s report, Jose Alano’s design of a plastic bottle solar collector has been used as inspiration. Jose Alano is a retired mechanic who managed to build a plastic bottle flat plate solar collector in order to tackle waste in his home town of Tubarão, Brazil. He and his wife created a solar collector which  provides a power saving of up to 30% using 100 plastic pl astic bottles and 100 milk mi lk cartons,  but the real saving is the environment en vironment as there are now n ow 200 fewer pieces of waste going to landfill and less energy is being consumed from the grid. Alano’s design neither has any pumps or electricity to induce circulat ion, this is

 because the system is based on o n the principle of thermosiphon. the rmosiphon. The difference differenc e in water density is enough to cause a cyclic movement from the collector panel to the tank. This system is used in many commercial heaters sold in the UK for as much £6,000. More than 7,000 people are benefitting from this design in the Santa Catarina state of Brazil alone. To heat water for a shower for one person a 1m 2 panel would be enough. However to construct one the following materials will be needed:  2L plastic bottles (60), cartons (50), 100mm PVC pipe (70 cm), 20mm PVC pipe (11.7m), 90-degree 20 mm PVC elbows (4), 20mm PVC T-connectors (20), 20 mm PVC end caps (2), PVC glue,  black matt paint and roller, rolle r, sand paper, self-amalgamating self-amalgama ting tape, rubber hammer, saw, wood or other material for the support. 1  The exhausted list of materials and the manufacture of this could be too much hassle for most people and this is where the design can be improved. This has been highlighted in Section 1.3: Section 1.3: Objectives Objectives  and is one of the core goals of this report.

1

 “How to make a solar water heater from plastic bottles,” The Ecologist, 17 -Nov-2017. [Online]. Available: https://theecologist.org/2010/may/06/h https://theecologist.org/2010/may/06/how-make-solar-water-heater-plastic-bottles. ow-make-solar-water-heater-plastic-bottles.

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2.2 Materials to be used as solar radiation reflectors/heat retainers Solar radiation reflectors which are normally the glazing in commercial solar collectors serve the purpose of reflecting solar radiation already in the collector. This allows the solar radiation in the collector to concentrate and increase the solar energy thus leading to a warmer collector, which will warm the water pipes which in turn increases the water temperature change therefore, leading to a more efficient solar collector. Anderson Lenz evaluated three systems of solar thermal panels using low-cost materials- PVC lining, PET bottles and aluminium cans. The experiments were carried out in Paraná, Brazil. The data was collected over a period of 30 days in which the computer record data simultaneously from each system every hour  between 1000hrs and 1600hrs. 16 00hrs. The results from his findings found that the aluminium cans proved to have the maximum efficiency from the three materials with an efficiency of 41.6% and reaching temperatures up to 54.3 ℃. The second most efficient is PVC lining achieving up to 39.4% efficiency and finally the least efficient out of the three is PET bottles achieving 34.5%. Although aluminium was the most efficient it was the hardest and most injuring  prone material out of the three. t hree. Cuts to the skin can easily easil y occur as the material is sharp and this could lead to the spread of potentially harmful diseases such as HIV or aids. 2  Aluminium cans are the most efficient, but most hard to work with. As the solar collector is to be created using recycled material and manufactured using minimal skill and tools, to make the cans adapt to the collector design will be hard and dangerous. Recycled PVC lining is hard to locate in Abuja, which leads to the collector being made using PET bottles. PVC lining in the form of a bubble wrap will be added to the design of the plastic bottle flat plate collector and its results will  be analysed.

2

 LENZ, A.M., COLLE, G., DE SOUZA, S.N.M., PRIOR, M., CAMARGO NOGUEIRA, C.E., DOS SANTOS, R.F., FRIEDRISH, L. and SECCO, D., 2017. Evaluation of three systems of solar thermal  panel using low cost material, material, tested in Brazil.

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2.3 Water piping to be used in the solar collector Flat plate solar collectors require water to be passed through the device in order for the water to heat up. The most common way of water transportation is using pipes. The piping in the solar collector can be arranged in many ways to meet the consumer’s demand which could be from easy manufacture to maximum heating.

Figure 1 shows the most common configurations of water piping in solar collectors. The most efficient out of the four is the parallel tube method. This is  because water is less dense den se at higher temperatures when compared with lower temperatures. This forces the hot water to the top of the collector and therefore the water output has the hottest water.  Figure 1: Most configurations ations of water piping in a solar solar collector  collector 3  Most common configur

The parallel tube method has to be created using durable strong HDPE plastic. This  plastic is not easily easil y recycled as it is more expensive in comparison to other plastics. The manufacture of the parallel tube method is also hard as it has to be cut and joints to be placed, this requires tools, which makes the manufacturing process hard and long, as well as increasing the cost as fixtures have to be bought. The serpentine method is the second most efficient mode of transport. This form of  piping does not require any a ny fixtures as there is no cu cutting tting involved. It uses o one ne long  piece of PVC pipe, which is widely recycled in Nigeria. N igeria. 4  A. Allouhi has conducted an experiment between the two most efficient modes of water piping in solar collectors. He measures the technical feasibility between the flat plate (FP) and evacuated tube collectors (ETC) in Morocco. The experiment was conducted over a year. The findings found that the ETC on average produce 20% more heat transferred energy (Q) than the FP method. The FP method never produced more Q than the ETC method, neither in the winter periods nor the summer periods. 5 

3

 “Research Institute for Sustainable Energy,” SEE Information Portal - Resources - Wind

4 5 “Research

Institute for  Sustainable Energy,” SEE Information Porta l - Resources - Wind  “Solar domestic heating water systems in Morocco: An energy analysis,” Egyptian Journal of Medical Human Genetics

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2.4 Geometry of the solar collector In order to achieve the optimum performance from the solar collector, the size of the collector has to be considered during the design. This is so the collector is not too  powerful or not powerful enough eno ugh for the purpose.

A. Elhabishi published a report on his findings of the optimum geometry of a solar water heating system. The author compared the performance of a flat plate solar thermal collector between different geometrical configurations whilst keeping the surface area numerically identical. The experiment was conducted over two days, 7 hours per day. The findings of the report found that the best thermal efficiency affecting a flat plate solar collector was when a square collector was used.

2.5 The most common plastic bottle used in Nigeria 6

The most common plastic bottle has a direct correlation with the waste of bottles.   This is because as there is more supply of the same bottles, with the assumption that the same proportion of bottles are wasted, the more waste of the same bottle there is. Finding the most common plastic bottle will allow the results of the collector in this report be accurate as the same dimensions will be used. The Day live is one of the popular media outlets in Nigeria. The media outlet  published a news article claiming that Eva, a Nigerian bottli bottling ng company, is the market leader for bottled water in Nigeria in 2016. The company also manufactures almost identical dimensions for soft drink manufacturers such as coca cola. The dimensions of the bottle are: Height = 215mm Width = 60mm Volume/ capacity: 500ml7 

6

 F. Welle, "Twenty years of PET bottle to bottle recycling — An An overview," Resources, Conservation & Recycling, vol. 55, (11), pp. 865-875, 2011. 7  Editor, O. (2017). Eva Leads in Bottled Water Market . [online] THISDAYLIVE.

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2.6 Fundamentals of flat plate solar collectors including performance indicators. To measure the performance of the solar collector, a medium or an indicator is needed for the collector to be measured against. Duffie talks a lot about the fundamentals of a flat plate collector in her book, ‘Solar engineering in ther mal mal processes’. A flat plate collector diffuses solar radiation, does not require tracking of the sun and require little maintenance. A black absorber plate absorbs radiation and emits thermal radiation in all directions. The inner cover  placed above the plate reduced convection and an d radiation losses losse s to the atmosphere. The back of the plate has insulation to reduce conduction losses. Flat plate collectors are almost always placed in stationary positions facing the sun throughout the year. The main points raised is that a black body is the perfect absorber of radiation and emitter of thermal radiation. In dry and dusty climates the efficiency of the thermal collector drops by 8%, this should be taken into consideration when the calculations are worked out.  out.  There are various performance indicators such as the heat coefficient of fluid (h), heat transferred (Q), collector efficiency (F’), heat removal factor (FR), flow factor (F’’), Nusselts number (Nu) and Reynolds number (Re).8 

2.7 The need for hot water and the average volumetric flow rates of water in Nigeria This report highlights the challenges of producing hot water in Nigerian homes and some ideas on how to tackle this issue. Nigeria is blessed with an abundance of renewable energy resources such as solar, wind, biomass and small hydropower  potentials. The country countr y also lies within a high sunshine sunshi ne belt and has enormous so solar lar energy potentials. Average sunshine hours are estimated at 6 hours per day, and solar radiation is fairly well distributed. The study mainly concentrates on the needs of hot water in homes, hotels and hospitals. The study is based in the Kaduna Metropolis of  Nigeria, which is around 100 miles mi les north from Abuja. An efficient, rep representative resentative sample was used in order to gain the necessary information needed for the assessment and evaluation of the research and the survey had residence from a selection of domestic homes, hotels and hospitals.

8

 J. A. Duffie and W. A. Beckman, Solar Engineering of Thermal Processes. (Fourth;4. Aufl.;4; ed.) 2013.

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The general respondents for domestic homes were 70% adult males. The work status of the respondents are split between private and public sector employees and some are also unemployed. 65% of the respondents earn less than US$375 monthly, and they have varied academic qualifications. Most respondents (76%) live in the urban  part of Kaduna town and have an average home consisting consis ting of a man, a wife and four children, who live in a multi-tenant, non-self-contained compound. Table 1  1 shows the quantity of hot water required at homes, hotels and hospitals. The majority of domestic homes require 100 litres of water per day whereas hotels and hospitals require 2000 litres.

Homes Hotels Hospitals

% of majority sample 84 93 60

Litres requires per day 100 2000 2000

Table 1: Required amount of water needed for each sector

The study researched whether there is a significant advantage for using solar heaters over the existing methods (firewood, electricity gas etc.) in homes, hotels and hospitals. The results of this research have found a strong agreement between the responses from homes, hotels and hospitals, and it can be concluded that there is a significant advantage, especially financially. Half of homes recurrent expenditure on energy is used for heating water; meanwhile, 32% of hotels and 21% of hospitals spend their energy expenditure for the same purpose. The research has concluded that provision of solar heater for domestic purposes has a significant relationship with the cost reduction of heating water and that solar heater can drastically reduce the cost of heating water in our domestic homes, hotels and hospitals. In addition to that, it was discovered that there is a significant gain for using solar heater over the existing methods. The increase in cost for non-renewable energy creates an extra  burden on its citizens. citizens . Generally, the cost of producing the hot water prompted the need for cheaper sustainable energy devices such as solar water heaters. This need inspired Israel, which is now the world leader in the use of solar energy per capita, where 85% of the households today are using solar thermal systems. Nigeria has an abundant solar energy potential, perhaps more than Israel, which should motivate the Nigerians to  be inspired and compete with Israel in relation to uti utilising lising the free solar en energy ergy  provided daily. It is recommended reco mmended that Nigeria should aatt least utilise solar energ energy y for domestic purposes because of its cost advantage and flexibility in domestic usage (when compared with kerosene or firewood). The average flow rate of water in domestic homes is between 1.9 Litres per minute (L/m) to 5.7 (L/m).

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3.  Methodology A solar thermal collector (STC) was produced using upcycled, readily available materials. The solar thermal collector was installed in an indoor lab using artificial (halogen) light and variable water flow rates. Experiments were run numerous times with different flow rates and a transparent cover (cling film) with an average time of twenty minutes. The STC had six plastic bottle heat concentration zones where the water was heated the most. The STC had fresh water flowing into the system via a PVC pipe which was covered with plastic bottles. The pipe was heated using the artificial light which heated the water. The water then left the system and went into the drain. A data logging control system was created to log the data from the sensor which recorded the data every second. 3.1 Material From the literature review of Lenz’s report on solar thermal panels in Brazil, iitt is an

obvious choice to choose aluminium cans for the flat plate solar thermal collector. However, aluminium cans are not as available in developing countries compared with PET plastic bottles. Aluminium cans are also harder to work with, and they are easy to injure people as they’re sharp. The drawbacks outweigh the benefits for the

cans which makes using this material infeasible. The next highly efficient material according to Lenz’s study found it to be PVC. This again is not widely accessible. Although PET is the least efficient material out of the three materials, it is easily accessible and there is high waste of this material. PET bottles are also easier to work with. These features make it easy to be upcycled which meets the project aim of making a solar thermal collector using upcycled materials. From the literature review of Lenz’s project we can establish that an ordinar ordinary y 500ml

 plastic bottle will be best suitable. s uitable.

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Bottled water is the most purchased drink in Nigeria. The literature review of This Day live, shows that Eva is the market leader for bottled water in Nigeria. Eva manufactures different types and sizes of water, but from Le nz’s report, 500ml were showed to be optimum. As the aim of the project is to use ‘easily available’ bottles, the 500ml bottle from Eva’s portfolio of bottles will be used for this project. The

dimensions for this bottle is as follows: Height = 210mm Width = 65mm Volume/ capacity: 500ml

left) ft)  Figure 2: (on le lastic bottle used in design of solar water heater

There is a bottle sold in the UK with similar dimensions, which will be used. The  bottle is called, ‘Aqua Pura 500ml water bottle’ and can be seen in Figure 2. The

 bottle will be connected to t o each other using a black PVC pip pipe, e, this will allow it to attract solar radiation. The base which will be used to house the water bottles will use readily available insulation and reused foil to concentrate the solar radiation to the bottle. The literature review from Duffie and Lenz was used to aid in the design of the bottle. PVC pipe is the most widely recycled pipes in Nigeria 9. PVC is also able to withstand heats of up to 60℃10. This allows the pipe to not deteriorate in the hot climate of Nigeria, therefore polluting the water. Polyethylene foam is widely used as packaging for machinery in Africa, such as  protecting washing machines mach ines11. This leads to a high waste of foam which results in it  being recycled. This material will be b e used as insulation Bubble wrap is also very common in the packaging industry 12 which therefore leads to it being widely recycled. This will be used as a secondary collector. Aluminium foil is used mostly to keep food fresh. This is also very recyclable in  Nigeria13.

9

 A. Rajesh Ejiogu, "E-waste " E-waste economics: a Nigerian perspective," Management of Environmental Quality: An International Journal, vol. 24, (2), pp. 199-213, 2013. 10  N. A. Saad et al, "The Effect of Several Service and Weathering Parameters on Tensile Propertie s of PVC Pipe Materials," Materials Sciences and Applications, vol. 3, (11), pp. 784-792, 2012. 11  R. Goddard, Packaging Materials. Leatherhead: Pira, 1990 12 R. 13

Goddard, Packaging Materials. Leatherhead: Pira, 1990  B. Winder et al, "Food and drink packaging: who is complaining and who should be complaining," Applied Ergonomics, vol. 33, (5), pp. 433-438, 2002.

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Materials needed to create solar collector: Material used

Section of solar collector

Purpose of material

used for

PET plastic

Plastic bottle

To reflect solar radiation and increase bottle air temperature

PVC plastic

Hose pipe

To transport the flowing water around the collector

Polyethylene

Insulation of sides and edges

Stop heat loss from rear and

foam Aluminium foil

Bubble wrap

edges of solar collector In between plastic bottle and

To reflect solar radiation to the

insulation

 plastic bottles

Placed on top of entire

Secondary reflector of solar

collector

radiation

Table 2: Materials used and their purpose in the solar collector

3.2 Designs The design of the plastic bottle solar collector was pretty much shortlisted due to the extensive literature review conducted in this report. Much of the inspiration behind the design came from Jose Alanos design, and tweaks were made in order for the design to meet the objectives of this report. As mentioned in the literature review, the size of a solar collector for a one-person shower is 1m2. Using the literature review for A. Elhabishi’s paper, we can conclude the best geometry shape for the solar collector will be square shaped. To help get this square shape, a polyethylene foam will be used to provide support for the structure of the solar thermal bottles and it will also provide insulation to reduce heat loss from the rear of the collector. The water piping which would go best with the solar collector for the purpose of the target audience and the objective of the report would be the serpentine method. This is because it is easy to manufacture and does not need any tools to build. The piping needed for this has to be flexible and the material used is PVC, which is a great match.

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3.2.1 Computed Aided Design drawings (CAD) PTC Creo parametric 3.0 was used to aid in the design process. This will allow  problems to be addressed without any waste of resources res ources and time. CAD also calculates various variables this allows a reduction in errors from humans and also hand-drawn designs. As CAD files can be saved and tweaks are allowed, it saves time from creating the whole design again another advantage of using hand-drawn design. There are disadvantages of using CAD, albeit these are outweighed from the advantages above. Disadvantages include specialist expensive software which requires high performing computers, and skill and training to know how to use the software.

 Figure 3: CAD drawings showing showing the final final proposed proposed design of the thermal thermal solar collector collector

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3.2.2 Thermal simulations

 Figure 4: Thermal Thermal analysis analysis of CAD drawing  drawing  

Figure 4 shows the thermal analysis of the solar collector. The solar collector is almost immune to a temperature of 60℃. The plastics do not deteriorate and do not fail, this shows the materials chosen are fit for purpose.

3.2.3 Compression test Figure 5 shows an image of the compression test of the plastic bottle with a PVC pipe. The bottle with PVC  pipe can withstand a compression compressi on of 165N until the plastic bottle compresses and the compression machine touches the PVC pipe. The PVC pipe can take a further compression of just above 30,000 N (see appendix section 8.3) section 8.3).. The compression of the plastic bottle is not as impactful as the PVC pipe, but for the purpose of its use, both compressions are more than enough.

 Figure 5: Compression test using Instron Instron 3367 machine machine Compression test

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3.3 Manufacture of solar thermal collector The design shown in Figure 3 was created firstly by the bottom of the bottles being cut so the PVC pipe can exit the bottle; this was accomplished by using a manual knockout punch tool. After the holes were cut the PVC pipe was inserted into all the  bottles. A template of the bottles and the pipe was used to cut the 900mm x 900mm  polyethylene foam. This allowed allo wed only the necessary plasti plastics cs of the bottle being exposed to the sunlight and the rest being insulated to reduce heat loss. To further  preserve the solar radiation radiat ion from the sun foil was us used ed around the bottles, th this is allowed the solar radiation to be focused on the bottles therefore onto the PVC pipe. The bottles, PVC pipe and the insulating foam were integrated and the apparatus can  be seen in Figure in Figure 7. The 7. The sensors were then added as shown in Figure in  Figure 6, the 6, the list of sensors and the sensor ID can be seen in Table in  Table 3. The 3. The location of where the sensors were placed can be seen in Figure in Figure 8. 8.  

 Figure 7: Solar Solar thermal collector without without sensors sensors 

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 Figure 6: Solar Solar thermal collector collector with sensors sensors and halogen light on 

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Sensor

Description

-

Water flow rate

Water flow meter

(L/m) +

Surface heat (w)

0

T Inlet

1

T outlet

2

Tb1

4

T ba 1

5

Tp1

8

Tb2

9

T ba 2

10

Tp2

11 12

Tb3 T ba 3

13

Tp3

14

T back 1

15

T cling film surface

16

T ambient

17

T back 2

0

2 4 5

1 8 9

11

14

12

17

13

10

+ 15

 Figure 8: So Solar lar thermal collector collector sensor sensor placement  placement  

Table 3: List of sensors used and their description description

Table 3  3 key: T = Temperature ( )  b = exterior bottle surface surf ace  ba = internal bottle air  p = exterior pipe = Water flow direction

℃

Sensor 15 was used on top of the cling film during the cling film experiments, otherwise it was placed next to the  pyrometer Sensor 14 & 17 were placed behind the insulation Sensor 16 was placed in the shadow  behind the solar thermal collector

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3.4 System description Typical flat plate solar thermal collectors used in hot temperature climates consist of a

water storage tank, control unit, pump station and flat plate collectors. The STC

employed in this study was inclined at 53° equal to the local latitude of Abuja in  Nigeria. The solar collector used 13mm 1 3mm black PVC pipe throughout tthe he collector; a similar pipe was also used for the input of water from the main water supply as well as the output from the system to the drainage. The pipe external to the STC were uninsulated, whilst the pipes throughout the collector were insulated using various upcycled materials including plastic bottles and foam insulation, to reduce heat losses. The collector consisted of a row of 6 recycled plastic bottles, and had one circuit which was fed from one row of plastic bottles to another. The collector had a total collector plate (absorber) surface of 0.82m 2 and each row had an approximate area of 0.14m2. The water inlet had a manually controlled reduced bore ball valve, this allowed the volumetric flow to be changed. One end of the PVC pipe was connected to the valve whilst the other was connected to a brass hose connector which had a compression gland, this allowed a thermocouple to measure the fluid temperature (sensor 0). The water then travelled and heated inside the collector until it met another brass hose connector which had a compression gland, this measure the outlet fluid temperature (sensor 1). The water then travelled to a flow meter (sensor -) that measured the volumetric flow rate of the water. A PVC pipe was connected from the flow meter to the drain, which then ended the journey for the water.

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4.  Theoretical calculations The calculations evaluated in this study help assess the performance of the solar thermal collector. The theoretical energy performance indices are the heat coefficient of fluid (h) and the heat flux factor (Qtop). The equations below are given in the document cited at the bottom of this page as well as the references page.14  The given values from the book are given as: Thermal conductivity of water (k) = 0.591 W/mk 15  Constant heat flux (Nu) = 4.36

⋅

Cp of water = 4185.5 J/kg K  

The dimensions of the equipment being used: Insulation height = 950mm Bottle height (L) = 210mm Insulation length = 870mm Bottle width (B) = 65mm Insulation width = 80mm Entire pipe length = 4700mm

Uniform distance between bottle and edge of insulation = 100mm Heat flux (q) = 3400 w/m 2 

Pipe internal diameter = 13mm

4.1 Surface Area Calculation As (surface area) = π x D x L 

Key: As = Surface area As = π x 13mm x 4700mm  4700mm  D = Dh = Internal pipe diameter L = entire pipe length As = 0.19195 m 0.19195 m2  Q = rate of heat transfer h = coefficient of heat transfer 4.2 Heat coefficient of fluid (h)  Newton’s law of cooling is used to work out the forced  Ts = Temperature of surface Tf  =  = Temperature of fluid  Nu = Nusselt number number convection heat transfer coefficient. k = Thermal conductivity of water Q = hAs (Ts  –  –  T  Tf ) q = heat flux

As = 0.19195

   .×.  × h=   = .  = 198.212 W/m k

 Nu =

2

8 % collector loss from literature review from Duffie. John, therefore h = 182.355 W/m2k

14

 Oyinlola, M. (2016). Thermofluids- Heat transfer and fluid flow . [online] Blackboard VLE. Available at: https://vle.dmu.ac.uk/bbcswebdav/pid-3450527-dt-content-rid5695673_1/courses/ENGD2005_2017_Y/print%206-8.pdf [Accessed 20 Feb. 2018].  

15

 "Thermal Conductivity of common Materials and Gases", Engineeringtoolbox.com, 2018.  

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4.3 Heat flux equation (Qtop) Heat flux is the rate of heat transfer through a given surface, per unit surface. Q = q × A 16  A=L×B Height = 750mm Breath = 670mm Area = 0.75 × 0.67 = 0.5025 m 2  q = 3400 w/m2 Qtop = q × A = 3400 × 0.5025 = 1708.5 W

16

 J. A. Duffie and W. A. Beckman, Solar Engineering of Thermal Processes. (Fourth;4. Aufl.;4; ed.) 2013.

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5.  Experiment 5.1 Apparatus used   Thermocouples- for measuring temperature (refer to table 1)



  Flow meters- to measure the volumetric flow rate of water



  Heat flux sensor for measuring heat



  Pyrometer- Able to measure solar irradiance from a solid angle of 2π. 



  1000W halogen lights- to act as artificial sun



  Liquid flat plate collector 



5.2 Analysis of Experimental Results Using flow rate at 2 litres/minute with cling film as an example of how the calculations were found. The full table of results can be found in Figure in Figure 9. The 9. The collector performance indices include: Rate of heat transfer of fluid (Q fluid), heat flux (Qtop), heat coefficient of fluid (h), collector efficiency factor F’), collector overall loss coefficient (UL), heat removal factor (FR ), ), collector flow factor (F’’), Nusselts number (Nu) and Reynolds number (Re). The calculations on how the values in Figure in Figure 9 and were derived can be found in appendix section 8.1: section 8.1: Calculations.  Calculations. 

 Figure 9: Experimental calculations showing showing mass mass flow rate, Qwater, Qwater, temperature temperature change, change, heat transfer transfer Experimental calculations coefficient and Nusselt number

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 Figure 10: Experimental Heat removal factor factor Experimental values for q, Qtop, Ta, Heat

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6.  Discussion This chapter summarises the dissertation, discusses its findings and contributions,  points out limitations of the current work, and also outlines directions for f or future research. The interpretation of graphs have been drawn using MATLAB and Microsoft Excel to demonstrate the results in depth. However, still many extensions of this research deserver further consideration, which has been mentioned in the conclusion. This chapter is split into five sections. Section 6.1 Section 6.1  analyses the differences between the calculated and experimental results. Section 6.2 Section 6.2  presents  presents a discussion on how the  parameters are affected by b y a change in the volumetric volume tric flow. Section 6.3 Section 6.3 discusses how including a reflector on the collector affects parameters. Section 6.4 Section  6.4 highlights the performance of the thermal collector when a water flow valve is added. Section 6.5 mentions the reliability of the experiment. 6.1 Differences between calculated and experimental results To compare on how well the plastic bottle solar collector was designed and developed, the experimental results will be compared with the theoretical results. If the collector performed as designed, there should be no percentage error and the experimental value will equal the theoretical value. However, if the designed did not  perform as expected, a percentage percent age error will be calculated and the reasoning of this will be discussed in Section 6.5 Section 6.5 - Reliability of the experiment.  experiment.  

6.1.1 Difference in heat coefficient of fluid (h (h)) 2



section 4.2 : h = 182.355 W/m k   Theoretical value given in section 4.2 Experimental value given in section 8.1.5: section 8.1.5: h  h =  W/m2K     Difference: 34.682 W/m2K

 217.0412



  Percentage error: 19.02%



The experimental heat coefficient of fluid is 19% higher than the theoretical value, this shows that the plastic bottle solar collector is transferring heat at a quicker rate than what was predicted. This could be because the Nu value used to calculate the theoretical value is 4.36, and the experimental Nu is 4.77. Taking the Nu value into consideration and recalculating the theoretical figure gives a value of h as 216.85.

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Using the more realistic theoretical value, the percentage error has changed to   0.08%. This error could be due to various factors which are to be discussed later in

section 6.5. section  6.5.  

6.1.2 Difference in heat flux factor (Qtop) section 4.3 : Qtop = 1708.5 W   Theoretical value given in section 4.3



section 8.1.4 : Qtop = 1264.9 W   Experimental value given in section 8.1.4



  Difference: 443.6 W



  Percentage error: 25.96%



The experimental result for Qtop is 25% lower than expected. This could be due to the heat flux (q) not providing the right amount of heat to the collector. In section 4.3 section  4.3 a heat flux (q) reading of 3400 W was used to calculate Q top. During the experiment, the artificial light was producing a heat flux of 2517.24 W/m 2. This is 25.96% less than predicted, possibly due to there being inadequate lighting. The reduction in heat is exactly the same as the difference in the theoretical and experimental values, suggesting the reduction in heat being the sole purpose the results do not match. Other factors could have also led to the percentage error and these are discussed later in the report in Section 6.5 Section 6.5 - Reliability of the experiment.  experiment. 

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6.2 Effect on parameters when water input flow is adjusted From The literature review, (Ekechukwu. V. O, 2011), shows that the average flow rate  for a mains water supply in Kaduna, Nigeria is between 1.9 Litres per minute rate (L/m) to 5.7 (L/m). Kaduna is 100 miles away from Abuja, so the figures from the literature review will suffice. To ensure the quality of this report three experiments were ran to see the effect on flow rate and the increase in temperature, if any.

6.2.1 Flow at 6 L/m

 Figure 11: Temperature Temperature vs Time for flow 6L/m with cling film

Figure 11  11 shows the results from different sensors on a flowrate of 6 L/m, the water flow value was set to 6L/m but using the readings from the flow rate metre the actual flow rate was 5.79L/m; for the purpose of simplicity in the discussion a flow rate of 6 L/m will be used for the remainder of the report. Values before 12:55 are to be ignored for the discussion to allow the collector to settle into a stable state. Bottle wall had the highest temperature recorded at an average of 35 ℃, bottle air followed with an average of 33 ℃, followed by pipe at an average of 22.5℃, and the final two temperatures were from the water outlet and inlet at averages of 12℃ and 11℃, respectively. The difference in the water inlet and outlet temperatures is 1 ℃. This shows the solar thermal collector heats the water by 9% at a flow rate of 6L/m.

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6.2.2 Flow at 4 L/m Figure 12  12 shows the results from a water flow rate of 4L/m, the reading from the flow rate metre is recorded as 3.97L/m. For the purposes of simplicity, these results will be interpreted as 4L/m for the remainder of the report. It is clear to see that the  part with the highest temperature value is the Temperature vs  Figure 12: Temperature vs time for water water flow at 4L/m with with cling film 

 bottle air (average 47.5℃). This is

logically unusual as the surface (bottle wall) temperature is the hottest as it is in direct contact and the closest to the sun. However, these results are correct as the  purpose of the bottle is to concentrate, heat and ret retain ain the solar radiation waves which leads to an increase in heat. From the results, we can see that the plastic bottle has fulfilled its job in that the bottle air is hotter than any other part in the solar thermal collector. The second hottest part is the bottle wall (average 33℃), then the pipe (average 22.5℃), than the water outlet (average 12℃) and finally the water inlet (average 10.5℃). The temperatures of the bottle wall, pipe, water inlet and water outlet are  pretty stable when compare with the fluctuating fl uctuating bottle air ttemperature. emperature. The fluctuations could be due to human error where someone could’ve been meddling with the device. This point is reinforced as the line which is fairly linear until the fluctuation starts which leads the temperature of the bottle air to match the temperature of the bottle wall. Decreasing the flow rate by 33.3% increases the difference between the bottle wall and the bottle air by 600%. This small decrease in flow rate allows the houses in  Nizamuddin Patel

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Abuja which have less pressurised water to benefit from the water bottles getting hotter. However, the purpose of this report is not to increase the bottle air temperature, it is to increase the water outlet. Decreasing the flow rate allows the temperature differences between average water outlet and inlet to increase by 50%. This increase in temperature most likely occurs as the water spends more time in the collector, therefore, allowing it to be exposed to more hot areas which therefore leads to a temperature rise in the water. Figure 9  9 shows the results of the experiment, the Reynolds number for flow 4L/m is calculated as 5377, this figure suggests that the flow in the water was turbulent. As the flow is turbulent it further allows the water to stay in the collector longer as the water is not laminar this, therefore, allows the water to have a higher temperature as it is in the system for longer.

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6.2.3 Flow at 2L/m Figure 13  13 shows a graphical representations of the results gained from the experiment at a flow of 2 L/m. The reading from the flow rate metre is 1.99 L/m. For the  purpose of simplicity these results will interpreted as 2 L/m for the remainder of the report. The bottle air is the hottest part in the solar thermal collector with an average temperature of 35 ℃. The  bottle wall is the second hottest h ottest with an average temperat temperature ure of 33.5℃. Experimental results from water flow at 2L/m  Figure 13: Experimental 2L/m with cling film 

The pipe has an average temperature of 24.5℃. Water outlet has an average temperature of 15℃, and finally, the water inlet has the coolest temperature averaging out at 11℃. The difference between the bottle air and the bottle wall have decreased significantly when compared with the results of the water flow at 4 L/m. The difference between the wall and the air is 4.3%, whereas the water at a flow of 4 L/m has a difference of 30.5%. This begs the question is it really worth having plastic bottles as insulation or are they a waste of resources? (This is expanded in section 7.1.4: section 7.1.4: Future  Future work)  work)  The water difference between the water inlet and outlet is 4℃ (36.4% increase), this has increased from the water flow of 4 L/m by 22%. By decreasing the water flow by 50% the temperature of the water has heated up by more than 22%. The Reynolds number from Figure from Figure 9  9 is calculated as 2694 which allows the water to have a laminar flow. By taking into account the average ambient temperature of Abuja as 32℃ 17 the solar thermal collector could increase the water input (assuming the water temperature is the same as ambient temperature) by 36%,

17 M.

Abdulkareem, S. Al-Maiyah and M. Cook, "Remodelling façade design for improving daylighting and the thermal environment in Abuja's low-income housing," Renewable and Sustainable Energy Reviews, vol. 82, pp. 2820-2833, 2018.

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This is a significant change which could allow households to have water at 43.5 ℃. Water at this temperature will comfortably allow the user to hygienically wash the dishes or clothes. The water could be used for shower purposes too, however, this may be a cool shower as an average warm shower temperature is 45℃18  Comparing these results with a flow rate of 6 L/m, the difference signifies where the decrease of flow is 66.67% and the increase in temperature difference between water inlet and outlet is 27%. The drop in flow rate allows the water to flow from a turbulent flow to a laminar flow.

6.2.4 Relationship be between tween Nusselts nu number mber (Nu) an and d Rey Reynolds nolds number (Re). Reynolds number is used to determine if the flow of the water in the solar collector is turbulent, laminar and transitional. This helps as when the flow is turbulent, the water stays in the collector for longer, which allows the water to heat up a little more.  Nusselts number is a ratio of convective con vective to conductive conduct ive heat transfer. This is i s used to determine the amount of heat transfer of the piping which lies between the heat of the bottle air and the fluid. The factor between both of these figures is the flow rate of the water. The relationship between the mass flow rate (kg/s) of the water, Reynolds number (Re) and Nusselts number (Nu) can be seen in Figure in  Figure 15. There 15. There is a strong positive correlation between Re and mass flow rate, and it can be clearly advocated that when the mass flow rate increases so does the Reynolds number. The increase in mass flow rate makes the flow more turbulent, which in turn increases the time the water stays in the solar collector which will potentially increase the temperature of the water. After excluding the anomaly at 0.0319 kg/s (mass flow rate), flow rate vs Nu has a similar positive correlation however it is not as strong as Reynolds number. From this, it can be noted that when mass flow rate increases, so does the Nusselt number. As Nusselt number increases, the thermal conductivity decreases, this makes it more difficult for the solar collector to heat water and therefore affects the  performance of the collector. collect or.

18

 K. Toyosada, T. Otani and Y. Shimizu, "Water use patterns in Nigerian hotels: Modelling toilet and shower usage," Water (Switzerland), vol. 8, (3), pp. 85, 2016.

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Relaitionship between Nu, Re and mass flow rate 9 8 7 6 5

Turbulent flow 4 3

Transitional flow 2 1

Laminar flow

0 0

0.02

0.04

0.06

Mass flow rate (kg/s) Flow rate vs Nu

Flow rate vs Re (×10^3)

0.08

0.1

Linear (Flow rate vs NU) excluding e xcluding anomaly Linear (Flow rate vs Re (×10^3))

 Figure 15: Relationship Relationship between Nu, Nu, Re and mass flow flow rate

Re < 2000 = laminar flow

(Left) Figure 14: visual representation of direction and reaction of luid flow in relation to  Reynolds number  number  

2000 6l/h), as adjusting flow for something with less flow will not really benefit the user.

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ENGD3000 –  Individual  Individual Project

6.5 Reliability of the experiment There is no such thing as a perfect experiment28, and the experiment conducted during this report is not an anomaly. This section will highlight how reliable the data in the experiment is. A major part in the reliability is measuring how close the experimental and calculated results are.

6.5.1 Errors The difference in experimental value and theoretical value is analysed in section 6.1: section  6.1:   Differences between calculated and experimental results. Both results. Both values did not equal each with each other, this suggests that there are a few errors in the experiment. This section will analyse the different types of errors.   Manufacturer error: Almost all manufactured parts come with a

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manufacturer’s tolerance level. The tolerance of the thermocouples used was

± 5% each. 15 thermocouples were used which could lead to false data as the total tolerance for just the thermocouples are ± 75%.   Hysterical error: The thermocouples were not calibrated prior to the

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experiment and the same thermocouples were used in different experiments which could deteriorate the reliability of the thermocouples. This could impact the data achieved during the experiment.   After the experiments were conducted it was noted by a technician who was

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dismantling the solar collector that the water inlet thermocouple was not touching the water and was instead measuring the brass material. This could lead to a false reading, as the brass was in direct contact with the solar radiation which could lead to a warmer inlet temperature resulting in the collector performing less than it should have.   The ambient temperature which was recorded is not realistic as it was too

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low. A thermometer was placed next to the thermocouple and verified the false reading. The thermocouple was changed but the problem remained. This could be due to either the thermocouple programming or the programming of the software

28

 H. Petroski, Small Things T hings Considered: Why there is no Perfect P erfect Design. New York: Vintage Books, 2004.

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De Montfort University

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ENGD3000 –  Individual  Individual Project   The experiment was not conducted in a controlled environment. The location

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of the experiment was in a lab accessible by other students as well as staff. As people were entering and leaving the lab a slight draft was brought and this could lead to the thermocouples bringing an unreliable result. The room was also heated using the universities central heating system, which could impact the temperature of the water heating in the solar collector. The lighting in the room and the windows could also bring extra uncontrolled solar radiation which would be picked up by the pyrometer resulting in a higher heat flux reading.   The environment in which the tests were conducted was not realistic with the

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environment of that in Abuja, Nigeria. One of the differences is the ambient temperature. The ambient temperature in the lab was recorded as 17℃, whilst the ambient temperature in Nigeria is around 32 ℃. This could lead to a much higher difference in performance as the atmospheres are different.   The time frames of the experiments lasted 15 minutes and the heat flux was

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constant. This is unrealistic as a day of the solar collector lasts 24 hours and the heat flux changes throughout the day.

6.5.2 How err errors ors ca can n be minimised for next ttime ime Errors can be minimised in various ways, although cannot be eliminated fully.   An experimental measurement is reliable if the test is repeated several times

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and the same value is given. Various tests can also be used and the mean of the tests can be used to improve the reliability of single measurements.   To ensure that the same value is given every time, the control variables can

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 be fixed such as restricting restrict ing access to the lab or sswitching witching the room lights off off..   Use more accurate and calibrated equipment

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De Montfort University

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7.  Conclusion This chapter concludes the findings of the report and highlights areas of future work. This project is heavily reliant on the design and development of a plastic bottle solar thermal collector. The project used inspiration from a few existing plastic bottle solar collectors but the collector made during this project is unique and the first of its kind, in that it is used using 500ml water bottles and it is to provide warm water to one household only. The prototype made, which was used in the experiment, is as its name, just a prototype and there are still a lot of improvements to be made before an optimised plastic bottle solar collector is built and ready for the mass market. That  being said, the target audience aud ience for the collectors collector s are people who are in either ex extreme treme  poverty or relative poverty pover ty and they will be using rrecycled ecycled materials to manufacture man ufacture their own plastic bottle solar thermal collector. As mentioned in section 1.2, to count this project as a success, the collector is to be made using readily available, low-cost materials. Section 3.1 analyses the different materials used to create the solar collector. Using “readily available, low-cost” as a critical standard to compare the different material choices the materials were chosen as can be seen in Table 2. The selection of materials allows the first target of project success to be completed. The second objective of the project is to compare and choose the design of the solar collector piping. The chosen piping was the ‘serpentine’ method. This was chosen as

it did not require any additional cutting of the pipe, which led to a faster manufacturing time. As the target audience for the solar collector is people in either extreme poverty or significant relative poverty in hot third world countries, the serpentine method does not require any special skills or tools, which further reinforces the reason it was chosen. The third objective of the project is to optimise the design of the solar collector. This was explored in section 3.2, where the inspiration design by Jose Alano’s design was

adjusted and optimised to meet the project aims which is to create a renewable water heat source for one household of extreme poverty people. The chosen design was designed using CAD software. It then underwent simulation tests where it was tested for thermal stress as well as compressive tests. The design went back and forth various times during the testing stages until it managed to pass the rigorous tests.

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After the CAD stages, the flat plate solar collector was manufactured using recycled materials and data from the experiment were gained. As the design used the serpentine method for the water piping, the manufacture of the collector is very easy and does not require expert skills or specialist tools. The final objective of this report is to characterise the performance of the solar collector. The data of the experiment went through scrutiny of various factors such as the heat coefficient of fluid (h), heat transferred (Q), collector overall loss coefficient (UL), heat removal factor (FR), collector flow factor (F’’), collector

efficiency factor (F’) and other performance measures. The results of these and the discussion can be found in section 5.2 and section 6, respectively. The collector  performed its best when the flow rate rat e of water is at 2Litres/minute with a seco secondary ndary reflector (bubble wrap) placed on top of the collector. By introducing the secondary reflector to the design, the FR, F’ and F’’ figures increase i ncrease by at least 40 %. The

temperature of the air contained in the bottles increased by more than 350 %. The change in water temperature increases by more than 15 %. This suggests that by including a secondary reflector to the design greatly improves the performance, and therefore the efficiency of the solar collector. The secondary reflector used in this report is recycled bubble wrap which is readily available in Abuja, Nigeria. The difference in theoretical and experimental heat coefficient of fluid is 0.08 %, this is less than the tolerance rating of the thermocouples at ± 5% each according to their manufactures ratings. The difference in theoretical and experimental for the heat flux factor (Qtop) is 25.96%. This could be due to various factors mentioned in section 6.5: Reliability of the experiment. Overall, with the limited cost to the population of Abuja due to the fully recycled  plastic bottle flat plate plat e solar collector, the solar collector col lector performs pretty prett y much as calculated. Due to the very low cost in manufacturing this design, and high performance factors, in that th at it can heat water by more than 15%; the p project roject and the design of the solar collector is a successful one.

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De Montfort University

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7.1 Future work Whilst the dissertation has demonstrated the potential of a plastic bottle flat plate solar thermal collector by using upcycled materials, many opportunities for extending the scope of this dissertation remain. This section presents some of these directions.

7.1.1 Replacing bottle air with water Thermal conductivity is the property of a material to conduct heat. As the use of the  bottle air is to heat the PVC pipe, the higher highe r the thermal conductivi conductivity ty the better. The thermal conductivity of air is 0.0258 W/ mK, whereas the thermal conductivity of water is 0.6145 W/mK. Replacing the air in the water bottles with water may lead to the transfer of heat to speed up, which will, therefore, increase the fluid temperature. This experiment was not conducted as my colleague is currently researching this  phenomenon further and the report for the outcome outcom e is due in July 2018 on DMU library.

7.1.2 Performance of solar thermal collecto collectorr at ttimes imes of no sun sunlight light (night) The tests which have been conducted in this report all have active sunlight throughout the full time of the tests, this is a great way of seeing the effects of the solar thermal collector at its peak moments. Although it will be great to have sunlight throughout the day, the reality of an average day in Nigeria has a day and a night. To see the performance of the solar thermal collector during the night will help see if the water still heats up in the night; this is highly unlikely as there is very little solar radiation in the night. An area of research to look into for the users of solar radiation to gain from the vast amount of solar radiation during the night is to fill the bottle air with a low melting temperature wax, such as paraffin. The paraffin will melt during the day, and will slowly solidify when the temperature drops in the night. During the solidification  process, the temperature of o f the paraffin will be higher tthan han the atmospheric temperature and the solar thermal collector can utilise this. However, for the paraffin to melt the atmosphere temperature should be around 31 ℃. This area of research

can be explored further which will help to advance this design which will enable the users to utilise the solar collector after the sun has set.  Nizamuddin Patel

De Montfort University

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