Solar power plant for generation
1. Solar power-The scientific power parameters.
2. Need of Solar Energy
3. Available solar energy.
4. Capturing the solar energy- Concentrators.
5. Solar power generation(thermal).
6. Stirling Engine
7. Solar Power Generation voltaic.
8. Solar cell types
9. Maximum Power Point Tracking(MPPT)
10. Performance of Solar Power Plants.
11. Global short term and long term forecast.
12. India and the solar power
13. Engineering Challenges
(The scientific power parameters)
• The earth receives more energy from the Sun in just one
hour than the world's population uses in a whole year.
• The total solar energy flux intercepted by the earth on any
particular day = 4.2 X 1018 Watthours or 1.5 X 1022 Joules
(or 6.26 X 1020 Joules per hour ).
• This is equivalent to burning 360 billion tons of oil ( toe )
per day or 15 Billion toe per hour.
• In fact the world's total energy consumption of all forms in
the year 2000 was only 4.24 X 1020 Joules. In year 2005 it
was 10,537 Mtoe.
Need of Solar Energy
• Solar power generation has emerged as one of
the most rapidly growing renewable sources of
• Solar power generation has several advantages
over other forms of electricity generation:-
1. Reduced Dependence on Fossil Fuels.
2. Environmental Advantages.
3. Matching Peak Time Output with Peak Time
4. Modularity and Scalability.
5. Flexible Locations
Available solar energy
• Earth's cross sectional area is 127,400,000 km², the total Sun's power
intercepted by the Earth is 1.740×1017 Watts.
• But as it rotates, no energy is received during the night and the Sun's
energy is distributed across the Earth's entire surface area, most of
which is not normal to the Sun's rays for most of the day, so that the
average insolation is only 1/4th of the solar constant or about 342
Watts per square meter
• Thus the average power intercepted at any time by the earth's surface
is around 127.4 X 106 X 106 X 200 = 25.4 X 1015 Watts or 25,400
• Integrating this power over the whole year the total solar energy
received by the earth will be:
25,400 TW X 24 X 365 = 222,504,000 TeraWatthours(TWh)
Capturing Solar Energy
Solar energy can be captured in two forms, either as heat or as
• Thermal Systems
Thermal systems capture the Sun's heat energy (infra red radiation)
in some form of solar collector and use it to mostly to provide hot
water or for space heating, but the heat can also used to generate
electricity by heating the working fluid in heat engine which in turn
drives a generator.
• Photovoltaic Systems
Photovoltaic systems capture the sun's higher frequency radiation
(visible and ultra violet) in an array of semiconductor, photovoltaic
cells which convert the radiant energy directly into electricity.
Typical concentrators are constructed from parabolic mirrors which reflect
the Sun's parallel rays on to a single spot at the focus of the mirror.
1. Parabolic Dish
2. Parabolic Trough
3. Power Tower
An alternative concentrator arrangement is the Power Tower which uses a large array
of parabolic mirrors focused on a solar furnace mounted on the top of a tower.
Because of the long focal length, the mirrors are almost flat.
These are sun tracking mirrors which are used to reflect the sun onto the top of a
solar power tower.
Solar Power Generation (Thermal)
• A solar thermal power plant usually has a system of mirrors to concentrate
the sunlight on to an absorber, the absorbed energy then being used to
power a heat engine which in turn drives a rotary generator.
• In large scale systems, the heat engine is usually a turbine driven by steam
or other vaporous working fluid. In small scale systems the heat engine
may be a Stirling engine.
• A heat engine that operates by cyclic compression and
expansion of air or other gas (the working fluid) at different
• there is a net conversion of heat energy to mechanical work.
• The Stirling engine is noted for:-
high efficiency compared to steam engines
ability to use almost any heat source.
Electrical Energy Storage
• Batteries are normally used as a buffer to provide the necessary
storage to guarantee short term continuity of supply
• By storing surplus energy during the day for use during the night
and during periods of overcast skies.
• Unfortunately it is not practical to store the summer's surplus
energy for use during the winter
• Hence to overcome this Thermal Energy Storage is used.
Thermal Energy Storage
• The use of molten salts to provide the capture, storage and
release of solar energy has recently been demonstrated.
• The Solana concentrating solar thermal plant in Arizona which
uses molten salt storage can keep delivering power for six hours
Solar Power Generation (Voltaic)
Solar voltaic power generation is the direct conversion of solar
energy into electricity.
How Solar Cells Work
• A photon with sufficient energy impinges upon a semiconductor
• It can transfer enough energy to a electron to free it from the
bonds of the semiconductor's valence band
• Hence it is free to move and thus carry an electric current.
• The junction in a semiconductor diode provides the necessary
electric field to cause the current to flow in an external circuit
•The typical output voltage of a PV cell is between 0.5 and 0.6 Volts and the
energy conversion efficiency ranges from less than 10% to over 20%.
•An array of cells can therefore generate
200 Watts of electrical power per square metre when illuminated by solar
radiation of 1000 Watts per square metre.
The corresponding current density
Because of climatic conditions the intensity of the insolation rarely reaches
Solar Cell Types
Several types of solar cells have been developed with the aims of
reducing costs and improving efficiencies.
1. Crystalline Silicon Solar Cells
2. Amorphous Silicon Solar Cells
3. Thin Film Silicon Solar Cells
4. Organic PV Solar Cells
5. Multi Layer (Tandem) Solar Cells
6. Exotic Materials
7. Electrochemical Solar Cells - Dye Sensitised Solar Cells (DSSC
or Grätzel Cells)
Maximum Power Point Tracking (MPPT)
• Power source will deliver its maximum power to a load when load has
the same impedance as the internal impedance of the power
• Unfortunately, batteries are far from the ideal load for a solar array and
the mismatch results in major efficiency losses.
• In its simplest form, charging is carried out by connecting the PV array
directly across the battery.
• The battery however is a power source itself and presents an
opposing voltage to the PV array.
• This pulls the operating voltage of the array down to the voltage of
the discharged battery and this is far from the optimum operating
point of the array.
•The diagram shows the basic building blocks of a small stand-alone off-grid PV
power generating system.
• A grid connected system would not need the battery and MPPT power tracking
• They do however need alternative capacity to come on stream to carry the load
during the hours of darkness.
Performance of solar power plants
• The performance of solar power plants is best defined by the
Capacity Utilization Factor (CUF) , which is the ratio of the actual
electricity output from the plant, to the maximum possible output
during the year.
The following factors are considered key performance indicators:
1. Radiation at the site
2. Losses in PV systems
3. Temperature and climatic conditions
4. Design parameters of the plant
5. Inverter efficiency
6. Module Degradation due to aging
• Solar Photovoltaic is a key technology option to realize the
shift to a decarbonised energy supply.
• Globally, the solar PV grid connected capacity has increased
from 15.2 GW in 2008 to 56.3 GW in 2014 and was 72.1 GW at
the beginning of 2015.
• The growth trend is continuing and is likely to explode once
the grid parity is achieved.
Global Short term forecast
• The European Photovoltaic Industry Association(EPIA) expects the
fastest PV growth to continue in China, South-East Asia, Latin
America, the Middle-East, North Africa, and India.
• By 2018, worldwide capacity is projected to reach between 321
GW (low scenario) and 430 GW (high scenario). This corresponds to
a doubling or tripling of installed capacity within five years.
Global Long Term Forecast
• IEA's long-term scenario for 2050 describes worldwide solar
photovoltaics (PV) and solar thermal (CSP) capacity to reach
4,600 GW and 1,000 GW, respectively.
• In order to achieve IEA's projection, PV deployment of 124 GW and
investments of $225 billion are required annually (about three and
two times of current levels).
• Levelized cost of electricity (LCOE) generated by solar PV would
cost between 4 to 16 US-cents per kilowatt-hour by 2050 which
would be much more lower than even the parity levels.
India and the solar power
• The Indian government has launched Jawaharlal Nehru National Solar
Mission (JNNSM) with a target of achieving 20000 MW by 2022.
• The scheme also aims at strengthening indigenous manufacturing
capability, and achieving 15 million sq. meters solar thermal collector area
by 2017 and 20 million by 2022.
• One of the steps to achieve this will be to make solar heaters mandatory
by incorporating byelaws in the National Building Code. Deployment of 20
million solar lighting systems for rural areas by 2022 is also part of the
• At 750MW, Madhya Pradesh to get world’s largest solar
power plant by next year August.
• The expected cost of power production is pegged at Rs 5 per/unit which
would be lower than production costs in any solar project in the country,
including the one at Neemuch in MP and Mehsana and Patan in Gujarat.
• Current standard cells have a theoretical maximum efficiency of 31
percent because of the electronic properties of the silicon material. But
new materials, arranged in novel ways, have exceeded 40 percent
efficiency which need to be employed.
• Another idea for enhancing efficiency involves developments in
• To eliminate the storage problem, a possible solution could mimic the
biological capture of sunshine by photosynthesis in plants, which stores
the sun’s energy in the chemical bonds of molecules that can be used as
food. The plant’s way of using sunlight to produce food could be
duplicated by people to produce fuel.