PV System Design

Country

Per capita consumption (kwh/year)

USA

13467

China

2986

India

714

Currently Installed Generation Capacity

2,09,276.04 MW = 2x109X

Source of Power

Share in MW

Fossil Fuels

140206

Hydro-Large

39291

Renewable Sources

24998

Nuclear

4780

TOTAL

2,09,276

% share in Generation 12%

Fossil Fuels

2%

HydroLarge

19% 67%

Renewable Sources Nuclear

India's power generation capacity will need to scale up Presently it is 209 GW by 2030 it will be over 460 GW at 6% growth rate Source: CEA, Annual Report

Max Demand

140090 MW

Supply

125234 MW

Deficit

14856 MW

%age deficit

10.6

Reference=http://cea.nic.in/reports/yearly/lgbr_report.pdf

 Most parts of India receive good solar radiation 5-7 kWh/sq. m/day  Within 6 hours deserts receive more energy from the sun than humankind consumes within a year – Gerhard Knies  I = 6 kwh/m2/day or 250w/m2 Efficiency = 15% => Power Produced = 37.5 W/m2 i.e. 37.5 MW/KM2 i.e. 1 GW/25 KM2 =>Thar desert area is 2.28 Lac KM2 (0.28 Million KM2) So now you can imagine the potential!!!

 Mission aims to achieve grid tariff parity by 2022 through  Cost reduction  Research and development  Local manufacturing and supporting infrastructure

Application Segment Target for Phase

Cumulative Target

Cumulative Target

for Phase II

for Phase III

(2013-17)

(2017-22)

1,100 MW

4,000 MW

20,000 MW

200 MW

1,000 MW

2,000 MW

7 million sq.m.

15 million sq. m.

20 million sq. m.

I (2010-13)

Grid Solar Power

incl. Roof Top

Off. Grid Solar Applications (inc. Rural Solar Lights)

Solar Collectors

http://www.mnre.gov.in/solar-mission/jnnsm

 Solar capital of India with Asia’s largest solar park  More than 600 MW solar photovoltaic installations  Government launched special solar energy educational

 Programs to full fill increasing demand of technical experts  Creating employment of 45,000 People in renewable energy sector  Ambitious plan of generating 100,000 Million units of clean green energy annually

Best way to learn is looking at

 High Electric bills  Increasing electricity tariff rates  Frequent electricity cut off  No contribution in environment saving

What if we used other sources of energy to power our house !!!

Which are…  Free of cost (just requires initial investment)  Provides more reliability  Helps in contributing for saving environment

Lets see how we can work it out….

Advantages of solar energy –  Locally available  Free source of unlimited energy

If we want to power your house / this lecture hall by using solar power Then, 1) How will we proceed ? 2) What will be the system size and cost? 3) What other systems we will have to integrate ? 4) What will be the methodology of sizing of each equipment ? 5) What precautions we will have to take and how much the overall system will cost?

1. Solar radiation assessment

2. Site survey and estimating maximum available energy 3. Understanding Photovoltaic technology 4. Requirement analysis 5. Determine load, power and energy consumption 6. System concept development

7. PV array and battery selections 8. Charge controller and inverter selection

Install and Run Pvsyst on your laptops

energy received from sun on a unit area perpendicular to the rays of sun Radiation is inversely proportional to square of the distance

At the mean distance of sun and earth, rate at which energy is received from sun on unit area perpendicular to rays of sun is solar constant

Its value is 1367 W/m2 = Isc

Beam radiations (Direct ) Diffused radiations (Diffuse from sky + Reflected from ground) Global (Beam+Diffused)

Measuring solar radiations

Amount of solar radiation on an object will depend on 

Location



Day of year



Time of day



Inclination of the object



Orientation of object (w.r.t. North-south direction)

Here the Object is solar panel, but it is true of any object (For solar thermal also!)

*Only for easy visualization

Day of the year is characterized by an angle Called as Declination angle (δ)

Angle made by line joining center of the sun and the earth w.r.t to projection on equatorial plane (+23.45o to -23.45o)

Study the effect of day /season through fixed tilt with our Simulation software PVsyst

Time of the day Time is based on the rotation of the Earth with respect to the Sun

It is characterized by Hour angle (w) – It is angular measure of time w.r.t. solar noon (LAT), Since 360o corresponds to 24 hours 15o corresponds to 1 hour

W = 15 (12 - LAT ) Hour 15 angle degree per hour

With reference to solar noon

Local apparent time In hour

In order to find the beam energy falling on a surface having any orientation, it is necessary to convert the value of the beam flux coming from the direction of the sun to an equivalent value corresponding to the normal direction to the surface.

Equivalent flux falling normal to surface

Ib beam flux

Ibn

θ

I b  I b n cos 

Vertical

Normal to the plane

Solid lines are reference lines

β

θ

γ

South direction (horizontal plane)

θ is affected by five parameters - Latitude of location (φ) - Day of year (δ) - Time of the day (w) - Inclination of surface (β) - Orientation in horizontal plane (γ)

Angle of Sun rays on collector Incidence angle of rays on collector () (w.r.t. to collector normal)

cos   sin  (sin  cos   cos  cos  cos  sin  )  cos  (cos  cos  cos   sin  cos  sin  )  cos  sin  sin  sin  Where, Latitude (φ) Surface azimuth angle (γ) Hour angle (w) Surface slope (β) Declination angle (δ)

Optimum inclination for fixed collector For the power output to be maximum, the incident radiation must be perpendicular to the panel.

The inclination of the fixed collector (facing South) w.r.t. horizontal at noon time should be =0o, collector facing due south

cos   sin  sin(   )  cos  cos  cos(   ) At noon,

 0

For optimal radiations

 0

cos   cos(     )

      0     

    Under this condition at noon time Sun rays will be perpendicular to the collector

One need to estimate declination angle for a given day, when optimum inclination is to be estimated

Optimum Inclination over a Year The noon position of the sun is changes throughout the year What is optimum position of collector for whole year (we need to estimate average value of declination angle over year)

Average  is Zero over the year

Hence  = 

Declination (degree)

30 20 10 0 -10

0

50

100

150

200

-20 -30 Days of year

250

300

350

Azimuth orientation from PVsyst

Continuous tracking of sun will ensure that the sunrays are always perpendicular to the solar panel (tilt angle=β is changed to ensure that incident angle=ϴ = 0)

Axis tracking from PVsyst

Now you know what should be the orientation of solar panels to get maximum output from fixed collector

Actually Only 1/4th problem is solved

Lets see what are other 3 parts … We also need to look at 1. Energy requirement 2. What PV technology to choose , 3. Actual installation and Financial part

Requirement Analysis Daily load requirements ConstraintsCost and space constraints

Future load requirement

Customer concerns Seasonal load requirement

Type of load 24x7power requirement for critical loads

Prepare the load chart to analyze total energy consumption Type of Load

Rated Power (Watts)

No. of Loads

Total Rated Power (Watts)

Load Duty Factor (0-1)

Total Avg. Hour Power s of (Watts) use

Total Rated Power Consumption = Rated Power x No. of Loads Total Avg. Power = Total Rated Power x Load Duty Factor

Total Energy Consumption = Total Avg. Power x Hours of use

Total Energy Consumption (Watthours/Wh)

Load entry in PVsyst

Why do we need batteries.. 

Storing energy produced by the PV array during the day, and to supply it to electrical loads as needed



To operate the PV array near its maximum power point



To power electrical loads at stable voltages



To supply surge currents to electrical loads and inverters

Types of Battery  Nickel Cadmium  Lead Acid  Nickel Metal Hydride  Lithium Ion

Li-ion battery

Lead acid battery

Nickel Cadmium battery

Nickel metal hydride battery

Dominant Energy Storage medium is Lead-Acid batteries (Mostly used in off-grid systems)

Advantages Simple and cheap to make Low self discharge rate

Today, 98% of these batteries are recycled Capable of high discharge rates

Battery Sizing 1. Required Supply Wh = Load Wh * (No.of day of storage + 1) 2. Include Efficiency factors from name plate of battery Depth of Discharge (DOD) Battery efficiency factor (BEF) System AC efficiency (ACEF) {ACEF = Inverter Efficiency x AC Cable Loss Factor} Battery Wh = Supply Wh / (DOD*BEF*ACEF) Select Battery Voltage (VBAT) based on system voltage Small systems (3kWh) are > =48-120 VDC. Battery Ah = Battery Wh/VBAT Select nearest larger rating available

To be on the safe side

Battery pack Check available Battery unit voltage and Ah No. of Battery units in parallel = Battery Pack Ah / Battery Unit Ah No. of Battery units in series = Battery Pack Voltage/Battery unit voltage

Remarks –  Standard deep cycle lead acid battery voltage rating available is 12V  Standard battery Ah available is 120Ah, 150Ah, 180Ah etc.

 Example: 24V/350Ah Battery Pack

Battery specifications in PVsyst

Light energy  Electricity It is generated due to principle of photoelectric effect Let’s look at the process in some further detail:

• Photovoltaic energy is the direct conversion of light into electricity at the atomic level. • Some materials exhibit a property known as the photoelectric effect that causes them to absorb photons of light and release electrons. • When these free electrons are captured, an electric current results that can be used as electricity.

I total  I 0 (e

qV / kT

 1)  I L

Where IL is photo current (constant) IL = Isc

Shows Current (I) and Voltage (V) relation

Graphical representation

Characteristics and Efficiency I

Isc

Im



Pm X

Vm

Max. Cell Power Incident light Intensity

Vm I m  Pin Voc

V Material

Depends on

Temperature Efficiency

Uses

To compare solar cells To estimate actual output

1st Generation

2nd Generation

3rd Generation

• silicon waferbased photovoltaic,

• Thin-film deposits of semiconductors

• Multi-junction solar cells • Dyesensitized nanocrystalline Gratzel solar cells • Organic polymerbased photovoltaic • Thermo photovoltaic solar cells.

• Single-crystalline and multicrystalline wafers

• amorphous silicon, cadmium telluride, copper indium gallium diselenide or copper indium sulfide

1.00

0.80 Current (A)

Current (A)

1.00

0.60 0.40 0.20 0.00 0.00

0.60 0.40 0.20

0.20

0.40

0.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0.60

Voltage (V)

Voltage (V)

2.00

2.00

1.60

1.60

Current (A)

Current (A)

 Series connection adds the voltage,

0.80

1.20 0.80

 Parallel connection adds the currents

1.20 0.80

0.40

0.40

0.00 0.00

0.00 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40

0.20

0.40 Voltage (V)

0.60

Voltage (V)

PV Sizing 1. Load Wh = Daily energy requirements 2. Average daily peak sun hours (PSH) in design month for selected tilt and orientation of PV array. 3. System Efficiency Factor (SYSEF) SYSEF = Battery EF x PV EF x Cable EF x Charger EF x Inverter EF 4. PV Watts peak (Total Wp)= Load Wh/(PSH*SYSEF) 5. Select PV module voltage based on system voltage. (System voltage is integral multiple of PV module voltage) 6. Select module Wp and size based on available space. 7. No. of PV Modules = Total Wp/Module Wp 8. Use nearest larger number of modules

Off-grid System Loss Factors Factors

% Loss

PV Response to Insolation

2-4

PV Mismatch

1-3

PV Soiling

1-3

PV Thermal Loss

5-10

DC Cable Loss

1-2

MPPT Charge Controller

1-2

Battery

10-15

Inverter including Transformer

4-6

AC Cable Loss

0.5-1

Total System Loss

25-40

Design of PV Array 1.

Integral No. of modules in string = system voltage/module nominal voltage

2.

No. of strings in array = Total No. of modules/No. of modules in string

3.

Use nearest larger number of strings in an array.

4.

List No. of modules in array and Standard Testing Condition Wp rating of array.

PV MODULE Specifications in PVSYST

Something like a charge controller !!!

The additional advantage could be – Increased battery life Preventing reverse current

A charge controller limits the rate at which electric current is added to or drawn from electric batteries.

Types PWM (Pulse Width Modulation) - Helps to remove buildup on the plates in a battery extending a battery’s life. MPPT (Maximum Power Point Tracking) - Adjusts the output voltage level to get maximum power output

Why solar charge controller is required !!!

Increases battery life For battery Regulate power Charge controller

Preventing reverse current Optimize power output

Charge Controller Selection

1. Match controller nominal system voltage to PV system voltage 2. Controller input voltage rating >= 1.2 x array open circuit voltage 3. Max. charge current >= 1.25 x array max. power point current.

4. Nom. load current = Max. DC Load Power/System Voltage. 5. Controller output current rating >= 1.5 x nom. load current.

Charge control specifications in PVsyst

Shadow analysis in PVsyst

Choosing PV technology and mounting structure  PV technology c-Si/TF-governed by environment, space, cost etc.

 Mounting system Rooftop/Terrace mounted/Ground mounted PV array also determine orientation and tilt of PV array based on latitude and usage pattern.

Types of Mounting system 1. On-Roof Solar PV Panel Mounting Systems

On tilted roof

On flat roof

2. Building integrated photovoltaic (BIPV)

Photovoltaic facade on Scheidegger Building, near Bern, Switzerland.

BIPV Project - OLV hospital Aalst, Belgium

3. On open ground Photovoltaic mounting structure

4. Tracking photovoltaic mounting structure

4 steps to design PV system for your home 1.

Optimize tilt of solar panel

2.

Estimate power and energy output of the plant based on selected array and battery size and system efficiency factors.

3.

Review system design, sizing and costs.

4.

Implement design.

In the form of  Savings  Eco-friendly energy utilization  Reliable solutions

Let’s see how much I saved by implementing this new energy solution

Run simulation in PVsyst

Off-Grid Systems: Scope, Applications and Costs Sizing and system specification     

Typical Size - 1W to tens of kW Battery back up is essential for operation in monsoon and at night Long life and low maintenance Upgradability is often required Loads are combination of DC and AC

Applications  Remote housing  Water pumping  Telecom Costing  Module cost is 30-40% of system cost, battery cost is recurring and appliances cost is often included in system cost.  System cost is in the range of Rs. 1.25-1.5 Lakhs/kW

Solar PV system

Sine wave inverter

Mechanism continually changes current direction

Square wave

Induced to Sine wave

1. Stand alone inverter  Used in isolated systems where the inverter draws its DC energy from batteries charged by photovoltaic arrays.  Unlike grid tie inverters, stand-alone inverters use batteries for storage.

 These types of inverters are mostly used in residential buildings in remote locations which are devoid of the utility grid and is powered by renewable energy sources.

2. Grid tied inverter 

That converts direct current (DC) electricity into alternating current(AC) and feeds it into an existing electrical grid.



During a period of overproduction from the generating source, power is routed into the power grid, thereby being sold to the local power company.



During insufficient power production, it allows for power to be purchased from the power company



The grid tie inverter must synchronize its frequency with that of the grid (e.g. 50 or 60 Hz) using a local oscillator and limit the voltage to no higher than the grid voltage

SOLAR POWER CONDITIONING UNIT (PCU) is used as control system for grid tie inverter

S T A N D A L O N E

G R I D T I E D

Inverter Selection 

Match inverter DC input voltage to system voltage.



Match inverter AC output voltage to nom. load voltage.



Inverter output power rating 1.5 to 2 times (min. 1.2 times) max. load power to allow for future expansion.



Inverter nom. load current = Max. load power/Nom. output voltage

What is there for you in the box…

To conceptualize the system

Designing electric system for efficient power utilization

Development of Energy storage system

Implementation of energy efficient system

Product & Installation Design Opportunities Design& Manufacturing Maintenance Engineering

Research and Development

Project Development & Consultancy

Manufacturing

Construction and Installation

Operation and Maintenance

Marketing

• Semiconductor technology • Building integrated Photovoltaic • Customized project development • Project consultancy • System integration in solar PV • Low skill in module assembly • Third-party installers are not skilled • Grid integration of mega watt scale PV power projects • Trouble shooting of circuitry of appliances • Mechanical Maintenance • After sales-service, customer care • Techno-commercial analysis

With the Jawaharlal Nehru National Solar Mission (JNNSM) scheme of the Government of India, the installed capacity is estimated to reach 20 GW by the year 2022. This would create enormous employment opportunities in the country. Sector

Estimated Current employment

Estimated projected Employment 2017 2022

Solar PV On-Grid

4,000

39,000

1,52,000

Solar PV Off-Grid

72,000

1,40,000

2,25,000

Total

76,000

1,79,000

3,77,000

No Green House Gasses

Price Stability

Infinite Free Energy

Decentralized Power

Saving Livelihood

Better Job Opportunities

Solar lantern

Solar powered satellite

Solar fly pad

Overhead PV system

Solar PV shading

Solar car