Osmotic Power

Institute of Technology of Cambodia

Topic : Group 01 : Lecturer : Students :

Osmotic Power 𝐼4 GEE(EE) Eth Oudaya CHAN Hangthong CHEA Kimsairng CHHAY Lyheang CHHIN Piden

2015-2016

e20120029 e20120037 e20120055 e20120068

CONTENT List of figure ........................................................................................................................ ii

1. Introduction ..................................................................................................................... 1 1.1 Objective ......................................................................................................................... 1 1.2 History ............................................................................................................................ 1 2. Principle .......................................................................................................................... 2 3. Methods .......................................................................................................................... 3 3.1 Reversed electro dialysis ................................................................................................ 4 3.2 Pressure-retarded osmosis............................................................................................... 5 4. Location Design .............................................................................................................. 7 5. Component of Osmotic Power Prototype ....................................................................... 8 5.1 The pre-treatment equipment .......................................................................................... 8 5.2 Membrane Modules ........................................................................................................ 8 5.3 Turbine for power generation ......................................................................................... 9 5.4 Pressure Exchangers and booster pumps ........................................................................ 9 6. Working .......................................................................................................................... 10 7. Application ...................................................................................................................... 12 8. Influencing Factor ........................................................................................................... 13 9. Advantage and Disadvantage .......................................................................................... 14 10. Conclusion ..................................................................................................................... 14 11. References ...................................................................................................................... 16

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LIST OF FIGURES Figure 1: Statkraft in Norway………………………………………………………………2 Figure 2: Osmosis…………………………………………………………………………..3 Figure 3: The osmotic power concept………………………………………………………5 Figure 4: Location design…………………………………………………………………..6 Figure 5: Component Osmotic power Prototype…………………………………………...7 Figure 6a: Sea water pretreatment………………………………………………………….7 Figure 6b: Fresh water pretreatment………………………………………………………..7 Figure 7: Membrane modules……………………………………………………………....8 Figure 8: Turbine……………………………………………………………………………9 Figure 9: Pressure Exchanger ……………………………………………………………....9 Figure 10: Schematics of Pressure Exchanger…………………………………………….10 Figure 11: Osmotic power process………………………………………………………...11

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OSMOTIC POWER

1. INTRODUCTION Energy consumption is an important aspect in our day to day life. Energy consumption rate is increasing very rapidly every day. If this continues as such then the world will one day face storage of energy. So it’s time to look for more sources of energy rather than the non-renewable source of energy and reduce the rate of consumption of nonrenewable energy. There are forms of renewable energy source in the world. The abundant renewable energies include solar energy, tidal energy, wind energy, Geo thermal energy, etc. one of the most recent power generation techniques is osmotic power generation. Osmotic power or salinity gradient power is the energy available from the difference in the salt concentration between seawater and river water. Salinity gradient power is a specific renewable energy alternative that creates renewable and sustainable power by using naturally occurring process. 1.1 Objective 

Study about renewable energy

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Recycle renewable source to do useful work.

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The power that we get from this renewable energy

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Avoid using non-renewable source that affect to the environment

1.2 History The Statkraft osmotic power plant at Tofte, Norway, is the world's first osmotic power or salinity gradient power generation plant. The prototype, which is based on osmotic technology, was constructed and is owned by Statkraft. It is operated by SINTEF Energy Research, a research division of SINTEF Group. The prototype was opened on 24 November 2009 by the Crown Princess Mette-Marit of Norway. The prototype plant has a designed capacity to generate 10kW of electricity. The completely commercialized osmotic power plant will be ready by 2015.The plant generates renewable and emissions-free energy and thus contributes to eco-friendly power production.

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Fig 1: Statkraft in Norway

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2. PRINCIPLE The basic principle involved in osmotic power generation is OSMOSIS. Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semi permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Salinity gradient energy is based on using the resources of “osmotic pressure difference between fresh water and sea water”. All energy that is proposed to use salinity gradient technology relies on the evaporation to separate water from salt. Osmotic pressure is the "chemical potential of concentrated and dilute solutions of salt". When looking at relations between high osmotic pressure and low, solutions with higher concentrations of salt have higher pressure.

Fig 2: Osmosis

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3. METHODS Two practical methods for osmotic power generation are reverse electro dialysis (RED) and pressure-retarded osmosis. (PRO). 3.1

Reversed electro dialysis A method being developed and studied is reversed electro dialysis or reverse

dialysis, which is essentially the creation of a salt battery. This method was described by Weinstein and Leitz as “an array of alternating anion and cation exchange membranes can be used to generate electric power from the free energy of river and sea water.” The technology related to this type of power is still in its infant stages, even though the principle was discovered in the 1950s. Standards and a complete understanding of all the ways salinity gradients can be utilized are important goals to strive for in order make this clean energy source more viable in the future 3.2

Pressure-retarded osmosis One method to utilize salinity gradient energy is called pressure-retarded

osmosis. In this method, seawater is pumped into a pressure chamber that is at a pressure lower than the difference between the pressures of saline water and fresh water. Freshwater is also pumped into the pressure chamber through a membrane, which increase both the volume and pressure of the chamber. As the pressure differences are compensated, a turbine is spun creating energy. This method is being specifically studied by the Norwegian utility Statkraft, which has calculated that up to 25 TWh/yr would be available from this process in Norway. Statkraft has built the world's first prototype osmotic power plant on the Oslo fiord which was opened by Her Royal Highness Crown Princess Mette-Marit of Norway on November 24, 2009. It aims to produce enough electricity to light and heat a small town within five years by osmosis. At first it will produce a minuscule 4 kilowatts – enough to heat a large electric kettle, but by 2015 the target is 25 megawatts – the same as a small wind farm.

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Fig 3: The osmotic power concept 4. LOCATION DESIGN Several plant designs have been developed for PRO power generation. The illustration shows a typical plant located at sea level. Fresh water is taken from a river close to its outlet. Sea water is fed into the plant by underground pipes. The diluted water is pumped back into the estuary thus maintaining the flow of water in the river. Statkraft has been developing osmotic power since 1997, and most of the conceptual challenges have been identified. All the acquired technology is in use in the water treatment industry today. Statkraft has focused its efforts on membrane development and has achieved an increase in power generation from less than 0.1W/m2 to almost 3 W/m2. Commercial operation requires a membrane performance of 5W/m2.April 2007 1973: Loeb discovers osmotic power Sidney Loeb discovered pressure retarded osmosis (PRO), a new method for generating power. Due to inefficient membranes, no particular progress was made during the 1970s and 1980s 1973–1997: Introduction of reverse osmosis During the 1980s and 1990s a breakthrough was made regarding membranes for RO, and the membrane technology was successfully introduced in many industrial applications. 1997: Statkraft engages in osmotic power 5

Statkraft engages in osmotic power technology development with a view to achieving costeffective osmotic power production.2003: First operating pilot plant Statkraft builds the world’s first pilot plant for PRO. Operation of the pilot plant begins in June 2003.2006: World leader Today, Statkraft is the world leader in the development of PRO, and has made significant state-of-the art achievements during the last few years: • A Salinity Power project (1999–2004) financed by the European Commission resulted in the design and production of a semi-permeable membrane optimized for PRO. • A detailed survey of the environmental aspects related to construction and operation of an osmotic power plant has been made. • Cost estimates made by Statkraft show that osmotic power would be competitive at today’s energy price level.

Fig 4: Location design

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5. COMPONENT OSMOTIC POWER POTOTYPE

Fig 5: Component Osmotic power Prototype 5.1 The pre-treatment equipment

Fig 6a: Sea water pretreatment

Fig6b: Fresh water pretreatment

The incoming fresh water and sea water are purified by using these equipment before being fed into the plant.

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5.2 Membrane Modules: Thin membranes rolled membranes for osmosis

Fig 7: Membrane modules The membranes employed are mainly of two types of: (i)

Cellulose acetate membrane A cellulose acetate membrane was prepared as following: the casting solution

is cast on a glass plate and immersed in ice cold water after solvent evaporation. After solidification the membrane is annealed between 80° and 95°C. A typical casting solution, according to a GKSS patent, consists out of cellulose diacetate, cellulose triacetate, dioxane, acetone, acetic acid and methanol. This composition was kept, but due to changing the casting parameters, both in the lab and in pilot scale, the performance was improved. Casting parameters like casting speed, changes in the temperature of the coagulation bath and also the changes of the support material led to the improved performance. Starting with a membrane performance of approximately 0.5 W/m2, this type of membrane was improved to a performance of close to 1.3 W/m2. (ii)

TFC membrane TFC membranes are made by the interfacial polymerisation of

trimesoylchloride and m-phenylene diamine. Starting with a membrane performance of approximately 0.1 W/m2, this type of membrane was improved to a performance of close to 3.5 W/m2.

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5.3 Turbine for power generation

Fig 8: Turbine 5.4 Pressure Exchangers and booster pumps to provide inlet seawater with sufficient pressure

Fig 9: Pressure Exchanger

The PX energy recovery device uses the principle of positive displacement and isobaric chambers to achieve extremely efficient transfer of energy from a high pressure waste stream to low pressure incoming feed stream. Virtually no energy is lost in the transfer. One particularly efficient type of pressure exchanger is a rotary pressure exchanger. This device uses a cylindrical rotor with longitudinal ducts parallel to its rotational axis. The rotor spins inside a sleeve between two end covers. Pressure energy is transferred directly from the high pressure stream to the low pressure stream in the 9

ducts of the rotor. Some fluid that remains in the ducts serves as a barrier that inhibits mixing between the streams. This rotational action is similar to that of an old fashioned machine gun firing high pressure bullets and it is continuously refilled with new fluid cartridges. The ducts of the rotor charge and discharge as the pressure transfer process repeats itself.

Fig 10: Schematics of Pressure Exchanger 6 WORKING In the PRO process, water with no or low salt gradient is fed into the plant and filtered before entering the membrane modules using the pre-treatment equipment. Membrane modules could contain spiral wound or hollow fibre membranes. In the module, 80–90% of the water with low salt gradient is transferred by osmosis across the membrane into the pressurised salty water. The osmotic process increases the volumetric flow of high pressure water and is the key energy transfer in the power production process. This requires membranes with particularly high water flux and excellent salt retention properties. 10

Fig 11: Osmotic power process The illustration in figure shows salty water pumped from the sea and filtered before it is pressurised and fed into the membrane module. In the module it is diluted by the water received from the less salty side of the membrane. The volumetric feed of salty water is about twice that of the fresh water. The diluted and now brackish water from the membrane module is split in two flows. While 1/3 of the brackish water is fed though the turbine to generate power, 2/3 is returned and energy is recycled in the pressure exchanger to add pressure to the feed of salty water. Optimal operating pressures are in the range of 11–15 bars, equivalent to a water head of 100–145 metres in a hydropower plant, enabling the generation of 1 MW per m3 s fresh water. The fresh water feed operates at ambient pressure. Pre-treatment of the water will be necessary depending on the water qualities. In Norwegian water treatment plants, mechanical filtration down to 50 μm, in combination with a standard cleaning and maintenance cycle has been enough to sustain the membrane performance for 7–10 years.

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7 APPLICATION Seventy percent of the earth's surface is covered with water, 97 percent of which is saltwater. The revolutionary process of Pressure Retarded Osmosis (PRO) is created by mixing of seawater and freshwater and the resulting osmotic power serves as both a renewable and consistent source of electricity. While still the in the early stages, the best estimates of global production potential of osmotic power exceed 1,600 terawatt hours, or the equivalent of half of Europe’s entire energy demand. Osmotic power is the process of converting the pressure differential between water with high salinity and water with lower or no salinity into hydraulic pressure. This hydraulic pressure can be used to drive a turbine that produces electrical energy.

There are two primary methodologies for osmotic power:

A) Natural occurrence's globally where river water meets the sea OR. B) Bringing together two man made water sources from processing plants. Both methods are viable but one produces more power than the other method. Method A: Seawater averages 40 grams of salt/ liter + River Water provides less power than Method B: Brine (from desalination) averages 60 grams of salt/ liter + treated water. The higher the salinity, the more power can be generated.

7.1 Enormous potential The global potential is estimated to be 1,600-1,700 TWh – equivalent to 50% of EU’s total annual power generation today. In Norway alone, it would beable to generate 12 TWh per year –equivalent to around 10% of our total power consumption. Osmotic power can become an important contributor to the generation of clean, renewable energy.

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7.2 Environment-friendly energy

Around the world, rivers flow out into the sea in urban and industrial areas where it will be possible to construct osmotic power plants. A power plant the size of a football stadium could supply around 30,000 households with electricity. These power plants can be built underground, e.g. in the basement of an industrial building or under a park, minimizing their visual impact. Osmotic power plants produce renewable energy with no polluting discharges to the atmosphere or water. In coming years use of renewable energies and thus conserving energy has to be promoted hugely .Osmotic power generation is indeed a promising technique with immense potential worldwide.

8 INFLUENCING FACTORS 

The membrane system is the heart of the osmotic power generation process

Ideal FO membrane system High water flux Sufficient salt rejection Limited fouling Scalable for mass production To be fit in modules Reasonable cheap 

The volume of water entering: The more water that enters the system, the more power can be produced.

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Salinity gradient: The higher the gradient between salinity in the fresh- and saltwater, the more pressure will build up in the system.

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Purity of water: It is important that the fresh water and sea water is as clean as possible. Substances in the water may get captured within the membranes support structure or on the membrane surfaces, which will reduce the flow through the membrane causing reduction in power output. This phenomenon, which is called 13

fouling, is linked to the design of the system, to the characteristics of the membrane, and to the membrane element. 

Flow losses: Flow losses should be minimum.

9 ADVANTAGE AND DISADVANTAGE 9.1 Advantages 

The energy produced is clean and non-polluting.

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There is no carbon dioxide or any other by produce released, It produced no greenhouse gases or other wastes.

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It is renewable energy that will help reduce our reliance on the burning of fossil fuels.

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So the electricity supply is constant and efficient.

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Once you’re built it, the energy is free because it comes from the ocean’s power.

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It need no fuel.

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It produces electricity reliably.

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Not expensive to maintain.

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Offshore turbine and vertical-axis turbines are not ruinously expensive to build and do not have a large environmental impact.

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A plant is expected to be in production for 75 to 100 years.

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Uses an abundant, inexpensive fuel source (waste) to generate power.

9.2 Disadvantage 

You will need to find a way to connect the electricity to the grid.

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Pose same threat as large dams, altering the flow of saltwater in and out of estuaries, which changes the hydrology and salinity and possibly negatively affects the marine mammals that use the estuaries as their habitat.

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The average salinity inside the basin decreases, also affecting the ecosystem

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A barrage across an estuary is very expensive to build, and affects a very wide area the environment is changed for many miles upstream and downstream. Many birds rely on the tide uncovering the mud flats so that they can feed.

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Barrage systems require salt resistant parts and lots of maintenance.

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Effects on marine life during construction phases.

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Operation and control must be provided remotely and maintenances is complicated due to sea-basing of the generation facilities

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Expensive to construct

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Power is often generated when there is little demand for electricity.

10 CONCLUSION Osmotic power plants can be constructed anywhere freshwater flows out into the sea, provided that the salt concentration is sufficiently high. Unlike solar power and wind power, osmotic power plants are not affected by fluctuations in the weather and will produce continuous and predictable electricity. Most river outlets around the world represent a potential location for a plant, even though some rivers need more cleaning of the water than others.

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11 REFERENCES 1. Osmotic power — power production based on the osmotic pressure difference between waters with varying salt gradients Stein Erik Skilhagen*, Jon E. Dugstad, Rolf Jarle Aaberg Statkraft Development AS, Lilleakerveien 6, No-0216 Oslo, Norway

2. Membrane processes in energy supply for an osmotic power plant Karen Gerstandta, K.-V. Peinemanna*, Stein Erik Skilhagenb, Thor Thorsenc, Torleif Holtc

3. www.statkraft.com

4. Power Production based on Osmotic Pressure. Article; Waterpower XVI, July 2009. Authors: Øystein Skramesto Sandvik, Stein Erik Skilhgen, Werner Kofod Nielsen

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