Energy is one of the most fundamental needs of our universe. Energy has come to be known as a `strategic commodity’ and any uncertainty about its supply can threaten the functioning of the economy, particularly in developing countries. Solar energy is the core source of all energies on earth. It is the most readily, freely available, non-polluting and the most abundant renewable energy source.
The earth is approximately spherical in shape, about 1.27×104 km in diameter. The radiant energy from the sun covers the entire electromagnetic spectrum.
The atmospheric interference restricts this spectrum to 290 to 3000nm – which is called ‘solar radiation.’ The energy flux received from the sun outside the earth’s atmosphere is of nearly constant value – and is termed as the Solar Constant (Isc), its value is accepted as 1367 W/m2.
Approximately 162,000 Tera (1012) watt of solar energy reaches earth’s surface. The solar energy received by the earth is more than 15,000 times the world’s commercial energy consumption and over 100 times the world’s known coal, gas and lignite.
Meteorological Data (Analysis of radiation data)
India has an area of 35million Sq.Km, and its strategic geographical location enables it to have a long and sunny days (275 to 330 days) for most part of our country. Indian Meteorological Department (I.M.D.) is maintaining a network of radiation measuring stations in India. The hourly variation data for solar radiation shows the maximum insolation falls between 12 noon to 2PM (Red patches). The annual meteorological data shows that except north east part of India, all other regions receive more solar radiation annually.
Solar Photovoltaic (PV)
Photovoltaics (PV) is the direct method of converting sunlight (photons) into electricity through a device known as the ‘Solar Cell’. Many different solar cell technologies – such as mono-crystalline and poly-crystalline silicon, thin films such as amorphous silicon, cadmium telluride, copper indium gallium selenide and concentrator-based high-efficiency III-V, etc. are available in the market today.
The basic PV or solar cell typically produces only a small amount of power. To produce more power, solar cells (about 40) can be interconnected to form panels or modules. PV panel output range is from 3 to 330 Watts and efficiency of 11 to 15% at commercial level. If more power is needed, several panels can be installed on a building or at ground-level in a rack to form a PV array.
For large electric utility or industrial applications, hundreds of solar arrays are interconnected to form a large utility-scale PV system.
Rooftop Installation Requirements
The shadow-free area required for installation of a rooftop solar PV system is about 12 Sq. Mtrs per kW (kilowatt). This number includes provision for clearances between solar PV array rows. The solar panels may be installed on the roof of the building with a south facing, tilt angle that varies in Tamil Nadu from 11 to 13 degrees depending on the latitude of the location. Sufficient area shall be available for servicing the system. The minimum clearance required for cleaning and servicing of the panels is 0.6m from the parapet wall and in between rows of panels. In between the rows of solar panels sufficient gap needs to be provided to avoid the shading of a row by an adjacent row. The solar grid inverter shall be placed indoor in a safe and easily accessible place.
For 1MW of power 14,000Sq Mtrs (Rooftop) space area is required.
Capital Subsidy
Capital Subsidy by the Ministry of New and Renewable Energy (MNRE): The Ministry of New and Renewable Energy of the Government of India provides capital subsidies for solar PV systems subject to certain conditions. As of March 2014, the capital subsidy for rooftop solar PV systems was 30% of the benchmark cost or 30% of the actual cost, whichever is less. The up-to-date benchmark cost and capital subsidy terms and conditions may be checked on the website of MNRE (see: www.mnre.gov.in).
Solar PV Plant in Educational institution:
Statistics of School Education:-
We all witness the rapid rise in the number of schools in India, so there is a huge energy demand which is inevitable in these places. All schools depend upon conventional energy sources for electricity. The table below shows total number of schools in our country.
Energy Consumption in Schools
For example, the energy consumption in a school that comprises 20 class rooms +5 office rooms +5 rest rooms. The data shown above are just to depict the energy consumption in schools. Only the major loads are shown there.
Cost of Solar Project to Meet the above Energy Requirement
From the above table, it is roughly estimated that, the energy consumed per day is 91.5 units and the money spent annually towards electricity bill is 2.05 lakhs.
If we install solar PV to meet 91.5 units of energy a day, we need to spend approximately 12 lakhs INR (excluding subsidy). The payback period is roughly estimated as 5.7 years.
Need of the Hour – Switch to Solar Energy
The above data shows that schools spend more money towards energy than what they actually spend for books and class room aids.
Unfortunately most of the existing educational infrastructure of India is solely dependent on conventional energy.
But these days, we can see a tremendous decline in fossil fuel content, and in fact they are expensive and irregular. Using DG (during power outages) set and maintaining them are really expensive and can cause health hazard too.
Benefits of Institution by Installing Solar Plant in Their Premises:
- Most of the schools have spacious premises including terrace, which is ideal for rooftop solar installation (no need to spend money to buy extra spaces).
- Educational institutes and offices are operated in morning hours only, i.e, during sun shine hours
- Government subsidy of 30% towards solar plant installation
- Can reduce electricity bills
- Can generate revenue if they can add extra power to the grid as well
- Payback period in 5-6 years
- Long lasting – 20 to 25 years
- Can contribute a pollution free and heathy environment
- Demonstration and awareness creation to students
Types of Solar Plant
- Solar off Grid connection
Distributed/decentralised renewable power projects using solar energy are utilised directly and stored in BES (Battery energy storage) system.
Solar Grid Tie (on grid)
In grid-connected Solar Photo-Voltaic (PV) systems, solar energy is fed into the building loads that are connected to the grid through a service connection with surplus energy being fed into the grid and shortfall being drawn from the grid. Production of surplus energy may happen when solar energy produced exceeds the energy consumption of the building. This surplus is fed into the grid.
During the night, or when during the day energy demand in the building exceeds solar energy generation, energy is drawn from the grid. Grid-connected solar PV systems have no battery storage and will not work during grid outage.
For buildings with grid-connected solar PV systems, the service connection meter needs to be of the bidirectional type, whereby import kWh and export kWh are separately recorded.
Advantage of Grid Connected Solar Systems in School Premises
- The maximum power consumption of an educational institute take place during the daytime. So, Grid tie solar system which eliminates the use of batteries completely is the best option for such institutions
- Once net metering system is adopted, with the feed in tariff policy, user can earn money by selling the electricity generated by the plant.
- The cost of batteries can be avoided.
Limitation with Grid Tied Solar System
- The only drawback in adopting grid tied system is, if the grid goes off (for any reason), we cannot inject the generated power from the solar plant to the grid.
Anti-islanding
Anti-islanding protection is a way for the inverter to sense when there is a problem with the power grid, such as a power outage, and shut itself off to stop feeding power back to the grid.
This is because when problems arise with the power grid, it is assumed that workers will be dispatched to deal with the issue, and they want the power lines to be completely safe, and not have electricity flowing from all the nearby PV grid-tie systems.
Conclusion
Utilizing solar energy is definitely free, clean, safe, abundant, renewable, but the high initial investment, higher cost per unit of electricity, long-term payback and poor conversion efficiency are some major drawbacks that have held back this ideal energy source.
Two reasons contribute to this high cost, the need to use large amounts of expensive semiconductor material, and the low conversion efficiency. Scenarios show that solar energy will be, in the long term, the most important energy source, provided that the cost of photovoltaic modules is substantially decreased. The challenge is to reduce the total costs of a photovoltaic system.
But when we analyse solar PV cost for the past 5 years in the global market, there is a significant fall in theprice. As per NREL data, in 2011, the median reported installed price of residential and commercial PV systems was $6.13/W for systems of 10 kW or smaller, $5.62/W for systems of 10 –100 kW, and $4.87/W for systems larger than 100 kW. The capacity-weighted average reported installed price of utility scale PV systems (ground-mounted systems at least 2 MW in size) declined from $6.21/W during 2004–2008 to $3.42/W in 2011.
The drop in installed system prices has resulted from module and non-module cost reductions, but module costs have declined more quickly, thus heightening the PV industry’s recent emphasis on reducing non-module costs. It is reported that there is a fall of 6 to 7% in PV price every year. The above graph shows the decline of PV cost for a large scale PV installation in the global market.
As new technology emerges, there can be new way to reduce the cost of PV. The instability and health hazard issues of conventional energy sources in the power market led to the emergence of renewable energy sources. Solar energy generation will be the strong pillar, which can provide sustainable energy production, clean and healthy environment.
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