Solar power is attractive because it is abundant and offers a solution to fossil fuel emissions and global climate change. Earth receives solar energy at the rate of approximately 1,73,000 TW. This enormously exceeds both the current annual global energy consumption rate of about 15 TW, and any conceivable requirement in the future. India is both densely populated and has high solar insolation, providing an ideal combination for solar power in India. India is already a leader in wind power generation. In solar energy sector, some large projects have been proposed, and a 35,000 km² area of the Thar Desert has been set aside for solar power projects, sufficient to generate 700 to 2,100 GW.
In launching India’s National Action Plan on Climate Change on June 30, 2008, the Prime Minister of India, Dr. Manmohan Singh stated:
“Our vision is to make India’s economic development energy-efficient. Over a period of time, we must pioneer a graduated shift from economic activity based on fossil fuels to one based on non-fossil fuels and from reliance on non-renewable and depleting sources of energy to renewable sources of energy. In this strategy, the sun occupies centre-stage, as it should, being literally the original source of all energy. We will pool our scientific, technical and managerial talents, with sufficient financial resources, to develop solar energy as a source of abundant energy to power our economy and to transform the lives of our people. Our success in this endeavour will change the face of India. It would also enable India to help change the destinies of people around the world.”
The National Action Plan on Climate Change also points out: “India is a tropical country, where sunshine is available for longer hours per day and in great intensity. Solar energy, therefore, has great potential as future energy source. It also has the advantage of permitting the decentralized distribution of energy, thereby empowering people at the grassroots level”.
In July 2009, India unveiled a $19 billion plan, to produce 20 GW of solar power by 2020. On November 23, 2009, Dr. Farooq Abdullah, Union Minister for New and Renewable Energy in a statement in the Parliament said that “the Government has approved a new policy on development of solar energy in the country by launching of the Jawaharlal Nehru National Solar Mission”. The mission aims at development and deployment of solar energy technologies in the country to achieve parity with grid power tariff by 2022.
INDIA – POTENTIAL
In terms of all renewable energy, currently India is ranked fifth in the world with 15,691.4 MW grid-connected and 367.9 MW off-grid renewable energy based power capacity. India is among top 5 destinations worldwide for solar energy development as per Ernst & Young’s renewable energy attractiveness index.
With about 300 clear sunny days in a year, India’s theoretical solar power reception, just on its land area, is about 5 PWh/year (i.e. = 5 trillion kWh/yr ~ 600 TW). The daily average solar energy incident over India varies from 4 to 7 kWh/m2 with about 1500–2000 sunshine hours per year, depending upon location. This is far more than current total energy consumption. The India Energy Portal estimates that if 10% of the land were used for harnessing solar energy, the installed solar capacity would be at 8,000GW, or around fifty times the current total installed power capacity in the country. For example, even assuming 10% conversion efficiency for PV modules, it will still be thousand times greater than the likely electricity demand in India by the year 2015.
Daytime production peak coincides with peak electricity demand making solar ideal supplement to grid.
The main features of the National Solar Mission are:
- Make India a global leader in solar energy and the mission envisages an installed solar generation capacity of 20,000 MW by 2022, 1,00,000 MW by 2030 and of 2,00,000 MW by 2050.
- The total expected investment required for the 30-year period will run is from Rs. 85,000 crore to Rs. 105,000 crore.
- Between 2017 and 2020, the target is to achieve tariff parity with conventional grid power and achieve an installed capacity of 20 gigawatts (Gw) by 2020.
- 4-5GW of installed solar manufacturing capacity by 2017.
The Mission will be adopted in a 3-phase approach
Phase I: Remaining period of the 11th Plan and first year of the 12th Plan (up to 2012-13)
Phase II: The remaining 4 years of the 12th Plan (2013-17)
Phase III: The 13th Plan (2017-22) as Phase 3.
The target for phase I is to ramp up grid connected solar power generation to 1000MW and an additional 3000MW by the end of phase II through the mandatory use of the renewable purchase obligation by utilities backed with a preferential tariff. The mission also plans to promote programs for off-grid applications, reaching 1000 MW by 2017 and 2000 MW by 2022.
At the end of each plan, and mid-term during the 12th and 13th Plans, there will be an evaluation of progress, review of capacity and targets for subsequent phases, based on emerging cost and technology trends, both domestic and global. The aim would be to protect Government from subsidy exposure in case expected cost reduction does not materialize or is more rapid than expected.
Solar power has so far played an almost non-existent role in the Indian energy mix. The grid-connected capacity (all PV) in India now stands at 481.48 MW as of 31st January 2012 and of this January alone accounted for 291.60 MW capacity additions.
However, the market is set to grow significantly in the next ten years, driven mainly by rising power demand and prices for fossil fuels, the ambitious National Solar Mission (NSM), various state level initiatives, renewable energy quotas including solar energy quotas for utilities as well as by falling international technology costs. Encouraging the spread of solar power generation (both CSP and PV) and aiming for grid-parity (currently at around RS.5/kWh) by 2022 and parity with coal power generation (currently at around RS.4/kWh) by 2030, is a key element in India’s comprehensive, long term energy supply strategy. Keeping in view the solar annual insolation, solar power could therefore easily address India’s long-term power requirements. However, it has to be cost-competitive. As of December 2011, solar power generation in India costs around RS.10/kWh, or over 2.5 times as much as power from coal. Importantly, it is crucial that the industry receives the right policy support to ensure that projects are executed and performed up to the mark.
NATIONAL SOLAR MISSION
NTPC Vidyut Vyapar Nigam(NVVN) ,the nodal agency for implementing the first phase of JNNSM , received 418 applications against a requirement of 650 MW(500 MW Solar Thermal and 150 MW Solar PV) for Batch I. Out of this 343 applications were for solar PV and 55 for Solar Thermal. The interest was high in the investor community for solar PV as applications worth 1715 MW (343*5 MW) were received as against a total of 150 MW. 30 bidders were selected through reverse bidding and projects were allocated to companies that offered highest discount to base tariff rate of Rs. 17.91/kWh. Projects totaling 610 MW were awarded with 145 MW under solar PV and 470 MW under Solar Thermal. The winning bids for solar PV varied from Rs. 10.95/kWh to Rs. 12.76/kWh and for Solar Thermal it was Rs. 11.14/kWh in Phase I Batch I. Camelot Enterprises Private Ltd was the lowest bidder and other successful bidders included Mahindra Solar One, Azure Power, SunEdison Energy, Lanco Infratech. The project capacity under Batch I is 5 MW for solar PV and minimum 5 MW and maximum 100MW for Solar Thermal. By July 2011, negotiations were concluded, PPAs awarded and financial closure achieved for 34 projects.
Under batch II, the project size has been increased up to 20 MW and the base price for solar PV projects is Rs. 15.39/kWh. NTPC Vidyut Vyapar Nigam (NVVN) received 154 applications for 1915 MW of solar PV projects against a requirement of 350 MW. The results of the bidding for solar PV projects indicate that the grid parity for solar power may not be too far off. The winning bids varied from Rs. 7.49/kWh to Rs. 9.41/kWh. The average bid price for both batch I and II was Rs. 12.15/kWh. French project developer Solairedirect emerged as the lowest bidder and Green Infra Solar the highest bidder. The other successful bidders included companies like Welspun Solar, Azure Power, SunBorne Energy and Mahindra Solar One. Around 70% and 85% of the allocated capacity under Phase I Batch I and Phase I Batch II respectively is to be implemented in Rajasthan.
GUJARAT: Most Progressive state in Solar Installation
Gujarat is witnessing a large market for the resale of PPAs by developers who often took up projects with the intent to sell them at a higher price to international developers. This has increased the project development costs and is threatening to make many projects unviable. As a result, only a limited number of projects under the Gujarat solar policy are currently moving forward successfully. As of 31st December, 175 MW of the 968.5 MW worth of projects with signed PPAs have been commissioned. Many projects are finding it difficult to attain financial closure and are facing significant delays.
Land acquisition is proving to be a challenge for projects in Gujarat. There are a limited number of land-banks (large areas of land acquired and consolidated by the government for the use of developers), thereby pushing developers to purchase private land, which is usually a burdensome and slow process. Developers have to engage directly with multiple land owners, facing issues with prices, location, land transfer procedures and right-of-way, amongst others. With the increasing interest from developers, there is a nexus developing between brokers and land owners impacting the price of land in Gujarat. The limited availability is leading to multiple brokers offering the same pieces of land to different developers. Realizing this, the owners have started quoting higher prices for the land. The brokers in turn have begun promising them a higher price in order to secure their clientele. This is significantly escalating land prices for potential sites in the state.
The solar park at Charanka is meant to solve many of these problems. So far, however, land has only been demarcated. The majority of the area remains undeveloped. The solar park policy by the Gujarat Power Corporation Limited (GPCL) provides not more than 50 acres of land for a 10MW PV plant. While this is practicable for plants working with crystalline modules, it is a limitation for thin film plants, which typically require more land for a 10MW plant. Another challenge is that the park is required to provide under-ground transmission lines but the transmission utility in Gujarat, the Gujarat Energy Transmission Corporation Limited (GETCO), does not currently have the expertise to execute this. Such issues, while they will not necessarily derail the solar park, will create further delays for developers who are already facing challenges in meeting their deadlines. For this reason, Kiran Energy, with a 20MW project in the park, has secured a guarantee by the government against possible penalties for delays in executing their project.
HISTORICAL GROWTH OF THE SOLAR MARKET IN INDIA
The Rural Electrification Program of 2006 was the first step by the Indian Government in recognizing the importance of solar power. It gave guidelines for the implementation of off-grid solar applications. However, at this early stage, only 33.8MW (as on 14-2-2012) of capacity was installed through this policy. This primarily included solar lanterns, solar pumps, home lighting systems, street lighting systems and solar home systems. In 2007, as a next step, India introduced the Semiconductor Policy to encourage the electronic and IT industries. This included the Silicon and PV manufacturing industry as well. New manufacturers like Titan Energy Systems, Indo Solar Limited and KSK Surya Photovoltaic Venture Private Limited took advantage of the Special Incentive Scheme included in this policy and constructed plants for PV modules. This move helped the manufacturing industry to grow, but a majority of the production was still being exported. There were no PV projects being developed in India at that stage. There was also a need for a policy to incorporate solar power into the grid. The Generation Based Incentive (GBI) scheme, announced in January 2008 was the first step by the government to promote grid connected solar power plants. The scheme for the first time defined a feed-in tariff (FIT) for solar power (a maximum of Rs. 15/kWh). Since the generation cost of solar power was then still around Rs. 18/kWh, the tariff offered was unviable. Also, under the GBI scheme, a developer could not install more than 5MW of solar power in India, which limited the returns from scale. One of the main drawbacks of the GBI scheme was that it failed to incorporate the state utilities and the government in the project development, leaving problems like land acquisitions and grid availability unaddressed. As a result, despite the GBI scheme, installed capacity in India grew only marginally to 6MW by 2009. In June 2008, the Indian government announced the National Action Plan for Climate Change (NAPCC). A part of that plan was the National Solar Mission (NSM).
The NSM guidelines indicated that the government had improved on the shortcomings of the GBI scheme. It aimed to develop a solar industry, which was commercially driven and based on a strong domestic industry. The extra cost of generation of solar power was being borne by the federal government under the GBI scheme. Even before the NSM, Gujarat was the first state to come up with its own solar policy in January 2009. The Gujarat solar policy initiated a process of the states formulating their own policy frameworks independent of the federal guidelines. The renewable purchase obligations for state distribution companies, a demand-driven scheme, further accelerated the formulation of solar policies at the state level. These policies exist independent of each other as well as the NSM. One of the key novelties of the Gujarat policy was that it introduced the concept of solar parks. These parks offered a comprehensive solution to concerns over land acquisition, grid connectivity, and water availability, hence offering developers a project allocation packaged with the necessary infrastructure. Other states like Karnataka, Andhra Pradesh and Rajasthan have followed suit in developing solar power development programs. Rajasthan has implemented land banks as well to make land acquisition easier. As more states plan to meet their solar power obligations, new policies are expected to be offered, creating as very vibrant set of markets across the subcontinent.
India has a great potential to generate electricity from solar energy and the Country is on course to emerge as a solar energy hub. The techno-commercial potential of photovoltaics in India is enormous. With GDP growing in excess of 8%, the energy ‘gap’ between supply and demand will only widen. Solar PV is a renewable energy resource capable of bridging this ‘gap’.
Most parts of India have 300 – 330 sunny days in a year, which is equivalent to over 5000 trillion kWh per year – more than India’s total energy consumption per year.
Average solar incidence stands at a robust 4 – 7 kWh/sq.meter/day.
About 66 MW of aggregate capacity is installed for various applications comprising one million industrial PV systems – 80% of which is solar lanterns, home/street lighting systems and solar water pumps, etc.
The estimated potential envisaged by the Ministry for the solar PV programme, i.e. solar street/home lighting systems, solar lanterns is 20 MW/sq. kilometer.
The potential of the solar thermal sector in India also remains untapped. The Ministry proposes an addition of 500 MW during the phase 1 of JNNSM.
Establishing manufacturing units at Export Oriented Units, SEZs or under the SIPS programme presents a good opportunity for firms which can leverage India’s cost advantage to export solar modules at competitive prices to markets in Europe and the United States.
STATE SOLAR POLICIES
GUJARAT SOLAR POLICY (Solar Power Policy – 2009)
Gujarat is the first state to launch its own solar policy in 2009. The Gujarat solar policy was in place a year before the NSM was announced.
Operative Period: From the date of issuance to March 31, 2014
The initial target is to achieve 500 MW of installed capacity by the end of this period.
Gujarat Energy Development Agency (GEDA) and Gujarat Power Corporation Limited (GPCL) have been appointed as nodal agencies for the facilitation and implementation of the policy. Gujarat Solar Power Policy is the only policy, which has awarded projects with a fixed FiT, on a first-come-first serve basis. This has resulted in the allocation of a number of projects to in-experienced or unknown developers.
|Rs. 15/kWh for the first 12 years from the date of commissioning||Rs. 5/kWh for the remaining 13 years|
|Rs. 12/kWh for the first 12 years|
From the date of commissioningRs. 3/kWh for the remaining 13 year
This gives a levelized tariff of Rs. 13.30/kWh for PV and Rs.10.54/kWh for Solar Thermal over 25 years. There were no timelines or guarantees required from the developers by the government to sign PPAs after the allotment of projects. Although, some companies like Moser Baer signed PPAs as early as January 12th 2009, many awaited the formalization of the NSM as its draft policy indicated a more attractive tariff of Rs. 17.91/kWh for PV and Rs. 15.40/kWh for Solar Thermal. Until late 2009, many developers had not signed PPAs in Gujarat. After the NSM policy was formalized in December 2009, developers moved away from Gujarat towards the NSM. In the first phase of the Gujarat policy, only 396.5 MW worth of PPAs were signed out of 716 MW allotments, leading to a conversion rate of 55% (PPAs signed as a percentage of projects allotted).
The tremendous interest from developers for NSM led to the competitive bidding for projects and a subsequent fall in tariffs. The fall in the NSM tariff below the levelized tariff in Gujarat suddenly made the Gujarat policy very attractive again to developers. Further, a significantly higher feed-in-tariff in the first 12 years in Gujarat matches investor’s timelines, as they would look to cover the cost of debt during this period. To ensure developer commitment, Gujarat’s solar policy for the second phase has been amended to include a deposit that would be encashed, if the developers fail to sign the PPAs. Larger available project sizes and the relative ease of land acquisition has led to larger developers getting serious about the Gujarat policy and signing PPAs and starting the implementation of projects. This has led to an increase in the conversion rate from 55% to 95%, with 537 MW worth of PPAs signed for 565 MW of the projects allotted for solar PV projects. With an increase of over 44% in the number of PPAs signed, Gujarat has significantly improved the credibility of its solar program from the first to the second phase. As compared to the NSM, the Gujarat policy has longer timelines for the execution of the projects. At the same time, it has a stringent penalty mechanism for delays and intends to levy penalties on redundant projects. Delays in commissioning the projects can incur penalties of Rs. 10,000 a day per MW for the first 60 days and Rs. 15,000 thereafter. The enforcement of these penalties is yet to be decided on. An initial 48.5 MW of the first phase were required to be commissioned by December 31, 2010. However, a 5MW project by Lanco Infratech and a 1MW project by SunEdison were the only ones that have met their deadlines. Six projects, including a 10MW solar PV project by Zebasolar and projects by Azure Power and Dreisatz GmbH were delayed despite their initial commitment to start operations.
On December 29th 2010, India’s first solar park was inaugurated at Charanaka in Patan district of northern Gujarat. So far, land has been allotted in the solar park for projects worth 176MW to 16 companies from the first and second phases. The total capacity of the solar park is 500MW with 30,000 sq. m per MW land allotted to Solar Thermal and 20,000 sq. m per MW of land allotted to PV projects. The solar park has been financed with over Rs. 12 billion by financial institutions like the International Finance Corporation (IFC), the Asian Development Bank (ADB) and the Infrastructure Development Finance Corporation (IDFC). The park tackles land procurement, water availability and grid connectivity issues and offers a “single-window” clearance process. Sixteen companies, including SunEdison Energy India (25MW), Alex Astral Power (25MW), Roha Energy (25MW), GMR Gujarat Solar (25MW), Kiran Energy (20MW), Emami Cement (10MW) and Azure Power (5MW) have been allotted projects worth a total of 176MW in the park. They have all signed PPAs with the state government.
KARNATAKA SOLAR POLICY (Solar Policy 2011 – 16)
Karnataka, a south-western state of India, announced its solar policy on July 1, 2011. Under the solar policy 2011-16, the Karnataka Government proposes to promote solar power as part of renewable energy generation policy in the state.
Operative Period: July 1, 2011 to March 31, 2016.
It targets 350 MW worth of projects till 2016.
- 200 MW is to be developed for direct sale to the distribution companies in the state (40 MW to be added each year)
- 100 MW under REC Mechanism
- 50 MW for bundling of power with thermal power from outside the state at rates to be determined by the State Government subject to approval of KERC.
The minimum capacity of solar PV projects is 3 MW and maximum capacity of 10 MW, while for Solar Thermal the minimum is 5MW with no cap on maximum. The quantum of power to be procured by ESCOMs from solar resources under purchase obligation is 0.25% of the total consumption and the shortfall in procurement of solar energy by the ESCOMs can be made good by purchase of solar specific RECs. Though the state has come up with its own policy, it will continue to support programs like the NSM. The state has set a combined target of 126 MW of solar power to be developed by 2013-14 through NSM and its own solar policy.
The Karnataka Renewable Energy Development Limited (KREDL) is the nodal agency for the policy. As part of its solar policy, KREDL has called for bids for 80 MW worth of project and received 22 bids from potential developers. The winners are to be selected through reverse bidding process. Under the REC Scheme of MNRE, KREDL has received proposals to set up 350 MW worth of solar projects.
The policy also allows developers to inject power at 11KV and above, while under NSM, the requirement is 33KV and above. Developing 11KV substation at power plant is cheaper than a 33KV substation which requires high cost components, so this will bring down the project development cost for the developers.
RAJASTHAN SOLAR POLICY (Rajasthan Solar Energy Policy, 2011)
On April 19th 2011, Government of Rajasthan issued Rajasthan Solar Energy Policy, 2011 to promote solar energy in the state. The policy aims to help Rajasthan, develop as a global hub of solar power for 10000-12000 MW capacity over the next 10 to 12 years to meet energy requirements of Rajasthan and other states of India.
It targets a minimum of 550MW of grid connected solar power in Phase 1 (up to 2013).
- Projects will be awarded through a process of competitive bidding.
- PV projects will be worth 300MW, out of which 100MW are reserved for project developers and 200MW for panel manufacturers.
- The minimum and maximum sizes for PV projects are 5MW and 10MW.
- Module manufacturers that set up their manufacturing plant in Rajasthan can bid for either 10MW or 20MW worth of PV projects based on their manufacturing capacity.
- A further 50MW will be allocated for rooftop PV (1MW each) and other small solar power plants.
- The DISCOMS in Rajasthan will provide PPAs for the projects. In addition, projects worth 100MW (50MW PV and 50MW CSP) are targeted for bundled solar power. In such projects, the developer can sell conventional power and solar power in a ratio of 4:1 at the weighted average tariff to the distribution utilities in Rajasthan. Varied project sizes will attract small as well as large developers looking to invest in projects of different scale.
Rajasthan Renewable Energy Corporation Limited (RRECL) has been appointed as the nodal agency for single window clearance of projects. The benchmark tariffs offered according to the new tariff revision are Rs.10.12/kWh for PV and Rs. 12.08/kWh for Solar Thermal projects for 25 years.
Unlike the National Solar Mission, there is no domestic content requirement in the Rajasthan solar policy. The developer can choose any established and operational technology from India or abroad. The draft also gives clear parameters for setting up evacuation infrastructure from the plant to the nearest substation. This has been an issue between the distribution utility and developers in other solar policies. For solar PV and Solar Thermal projects, if the power plant lies within 15km of the nearest substation, the cost will be borne by the distribution company (DISCOM). For any length above 15km, the cost will be borne by the developer. For rooftop projects, the cost will be borne by the DISCOM but the developer will need to take permission from the DISCOM before finalizing the location of the project. The policy has taken up lessons from forerunners like the NSM and the Gujarat solar policy – it declined to have the 5MW limit on individual projects that made the NSM less attractive to large players but, unlike the Gujarat policy, it has placed fixed limits on overall capacity allocation. The policy also addresses the concerns of the developers, with regards to the allocation of land and water, availability of an evacuation network and the localized supply chain. Finding the right location and acquiring land is one of the major bottlenecks so far for projects in India. To solve this problem, the policy looks to create land banks from government land. Some of these land banks are situated near cities like Bikaner and Barmer. Under the policy, after the 25 years of the PPA, the developer can use the land for commercial purpose..
Solar Energy ——>>> Heated Water ——->>> Electricity
Solar thermal electricity technologies produce electric power by converting the sun’s energy into high-temperature heat using various mirror configurations, which is then channeled to an on-site power plant and used to make electricity through traditional heat-conversion technologies. The plant essentially consists of two parts; one that collects Solar energy and converts it to heat, and another that converts the heat energy to electricity.
TYPES OF HEAT COLLECTORS:
Evacuated Glass Collector - Evacuated-tube collector consists of parallel rows of glass tubes connected to a header pipe. Each tube has the air removed from it to eliminate heat loss through convection and radiation. Evacuated-tube collectors fall into two main groups.
Direct-flow evacuated-tube collectors - These consist of a group of glass tubes inside each of which is a flat or curved aluminium fin attached to a metal (usually copper) or glass absorber pipe. The fin is covered with a selective coating that absorbs solar radiation well but inhibits radiative heat loss. The heat transfer fluid is water and circulates through the pipes, one for inlet fluid and the other for outlet fluid.
Heat pipe evacuated-tube collectors - These consist of a metal (copper) heat pipe, to which is attached a black copper absorber plate, inside a vacuum-sealed solar tube. The heat pipe is hollow and the space inside, like that of the solar tube, is evacuated. The reason for evacuating the heat pipe, however, is not insulation but to promote a change of state of the liquid it contains. Inside the heat pipe is a small quantity of liquid, such as alcohol or purified water plus special additives. The vacuum enables the liquid to boil (i.e. turn from liquid to vapor) at a much lower temperature than it would at normal atmospheric pressure. When solar radiation falls on the surface of the absorber, the liquid within the heat tube quickly turns to hot vapor rises to the top of the pipe. Water, or glycol, flows through a manifold and picks up the heat, while the fluid in the heat pipe condenses and flows back down the tube for the process to be repeated.
Flat Plate Collector - Flat-plate collectors are the most common solar collectors for use in solar water-heating systems in homes and in solar space heating. A flat-plate collector basically consists of an insulated metal box with a glass or plastic cover (the glazing) and a dark-colored absorber plate. Solar radiation is absorbed by the absorber plate and transferred to a fluid that circulates through the collector in tubes. In an air-based collector the circulating fluid is air, whereas in a liquid-based collector it is usually water.
Flat-plate collectors heat the circulating fluid to a temperature considerably less than that of the boiling point of water and are best suited to applications where the demand temperature is 30-70°C (86-158°F) and/or for applications that require heat during the winter months.
Air-based collectors are typically used for heating buildings and drying crops. Liquid-based may be glazed or unglazed. Glazed liquid collectors are the commonest type of solar collector for providing domestic and commercial water and for heating indoor swimming pools. Unglazed collectors are often used for heating outdoor pools. A special type of unglazed collector called a perforated plate collector is used to preheat ventilation air for commercial buildings or, in some cases, for drying crops.
Flat collectors can be mounted in a variety of ways, depending on the type of building, application, and size of collector. Options include mounting on a roof, in the roof itself, or free-standing.
Solar Energy ——>>> Electricity
Solar Cell - A solar cell is a semiconductor device that transforms sunlight into electricity. Semiconductor material is placed between two electrodes. When sunshine reaches the cell, free negatively charged electrons are discharged from the material, enabling conversion to electricity. This is the so-called photovoltaic effect. In theory, a solar cell made from one semiconductor material only can convert about 30 percent of the solar radiation energy it is exposed to into electricity. Commercial cells today, depending on technology, typically have an efficiency of 5 -12 percent for thin films and 13 – 21 percent for crystalline silicon based cells.
Efficiencies up to 25 percent have been reached by the use of laboratory processes. By using multiple solar cells, efficiencies above 35 percent have been achieved.
Solar Photovoltaics - Photovoltaics has been derived from the combination of two words, Photo means Light and Voltaic means electricity. It is a technology that converts light directly into electricity. Photovoltaic material, most commonly utilizing highly-purified silicon, converts sunlight directly into electricity.
The photovoltaic effect is the basic physical process through which a PV cell converts sunlight into electricity. Sunlight is composed of photons, or particles of solar energy. These photons contain various amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons strike a PV cell, they may be reflected or absorbed, or they may pass right through. Only the absorbed photons generate electricity. When this happens, the energy of the photon is transferred to an electron in an atom of the cell (which is actually a semiconductor). With its newfound energy, the electron is able to escape from its normal position associated with that atom to become part of the current in an electrical circuit. By leaving this position, the electron causes a hole to form. Special electrical properties of the PV cell-a built-in electric field-provide the voltage needed to drive the current through an external load (such as a light bulb).
To induce the electric field within a PV cell, two separate semiconductors are sandwiched together. The p and n types of semiconductors correspond to positive and negative because of their abundance of holes or electrons (the extra electrons make an n type because an electron has a negative charge).Although both materials are electrically neutral, n-type silicon has excess electrons and p-type silicon has excess holes. Sandwiching these together creates a p/n junction at their interface, thereby creating an electric field. When the p-type and n-type semiconductors are sandwiched together, the excess electrons in the n-type material flow to the p-type, and the holes thereby vacated during this process flow to the n-type. (The concept of a hole moving is somewhat like looking at a bubble in a liquid. Although it’s the liquid that is actually moving, it’s easier to describe the motion of the bubble as it moves in the opposite direction.) Through this electron and hole flow, the two semiconductors act as a battery, creating an electric field at the surface where they meet (known as the junction). It’s this field that causes the electrons to jump from the semiconductor out toward the surface and make them available for the electrical circuit. At this same time, the holes move in the opposite direction, toward the positive surface, where they await incoming electrons.
Lack of electricity infrastructure is one of the main hurdles in the development of rural India. India’s grid system is considerably under-developed, with major sections of its populace still surviving off-grid. As of 2004 there are about 80,000 unelectrified villages in the country. Of these villages, 18,000 could not be electrified through extension of the conventional grid. A target for electrifying 5,000 such villages was fixed for the Tenth National Five Year Plan (2002–2007). As on 2004, more than 2,700 villages and hamlets had been electrified mainly using SPV systems. Developments on cheap solar technology are considered as a potential alternative that allows an electricity infrastructure comprising of a network of local-grid clusters with distributed electricity generation. That could allow bypassing, or at least relieving the need of installing expensive, and lossy, long-distance centralised power delivery systems and yet bring cheap electricity to the masses.3000 villages of Odissa will be lighted with Solar power by 2014.
CHALLENGES AND CONSTRAINTS
Per capita land availability is a scarce resource in India. Dedication of land area for exclusive installation of solar cells might have to compete with other necessities that require land. The amount of land required for utility-scale solar power plants — currently approximately 1 km² for every 20–60 megawatts (MW) generated could pose a strain on India’s available land resource. The architecture more suitable for most of India would be a highly distributed, individual rooftop power generation systems, all connected via a local grid. However, erecting such an infrastructure which doesn’t enjoy the economies of scale possible in mass utility-scale solar panel deployment — needs the market price of solar technology deployment to substantially decline so that it attracts the individual and average family size household consumer. That might be possible in the future, since PV is projected to continue its current cost reductions for the next decades and be able to compete with fossil fuel.
While the world has progressed substantially in production of basic silicon mono-crystalline photovoltaic cells, India has fallen short to achieve the worldwide momentum. India is now in 7th place worldwide in Solar Photovoltaic (PV) Cell production and 9th place in Solar Thermal Systems with nations like Japan, China, and the US currently ranked far ahead. Globally, solar is the fastest growing source of energy (though from a very small base) with an annual average growth of 35%, as seen during the past few years.
Some noted think-tanks recommend that India should adopt a policy of developing solar power as a dominant component of the renewable energy mix, since being a densely populated region in the sunny tropical belt, the subcontinent has the ideal combination of both high solar insolation and a big potential consumer base density. In one of the analyzed scenarios , while reining on its long-term carbon emissions without compromising its economic growth potential, India can make renewable resources like solar the backbone of its economy by 2050.
The government of India is promoting the use of solar energy through various strategies. In the latest budget for 2010-11, the government has announced an allocation of Rs.10 billion towards the Jawaharlal Nehru National Solar Mission and the establishment of a Clean Energy Fund. It’s an increase of Rs. 3.8 billion from the previous budget. Also budget has also encouraged private solar companies by reducing customs duty on solar panels by 5 percent and exempting excise duty on solar photovoltaic panels. This is expected to reduce the roof-top solar panel installation by 15- 20 percent. The budget also proposed a coal tax of USD 1 per metric ton on domestic and imported coal used for power generation.
Contributor: G. Vishnu (MBA-10 th Batch, NPTI, Faridabad)