Solar Photovoltaics as Energy Alternative in Rural India: Materials/Device Research and Challenges

Solar Photovoltaic technology becomes imperative for India due to the current growing energy demand, future scarcity of fossils fuels and increase in the environmental pollution due to the use of conventional energy resources in large quantities. India can switch from conventional to non-conventional energy sources easily being naturally blessed with the renewable energy resources. The renewable source in the form of solar energy can be used to generate the energy through Photovoltaic technology for both urban and rural areas in India.

The materials which are being explored as the main components of a solar photovoltaic device can be both inorganic and organic in nature. Currently, nanomaterials are also being explored for this technology to improve the overall efficiency of the device. In this paper the research based on the materials as well as devices will be presented and important aspects will be discussed. This paper will also present current status and challenges of the solar photovoltaic technology as an energy alternative in India with a special focus on the rural areas.

Around 1 billion people are deprived of electricity in their homes and around one third, such people live in India as per the literature. One of the Sustainable Development Goals of the United Nations includes “access to affordable, reliable, sustainable and modern energy for all” (United Nations, 2015). Moreover, the government in India as well has set a goal to achieve universal electrification for urban and rural households by 2020 (Press Trust of India, 2017).

It is observed that the consumption of electricity in India is being increased day by day. Moreover, most of the energy generation is done using the fossil fuels which includes coal or oil. According to the studies, only 33.9% of the electrical power generation is achieved by using the renewable energy sources whereas the rest share is with the fossil fuels. As power generation is the concerned for the world, from last 50 years there is significant growth in the usage of non-renewable sources. Furthermore, if the same rate is continued, there will be a possibility that the remaining oil and coal could be squeezed out. Also, power generation from the non-renewable resources causes many problems to the planet’s surface temperature and atmosphere. This is important that India has surplus amount of electricity which is generated but the country lacks proper infrastructure for supply of power to rural India.

It is important to mention that installation and maintenance of a power supply line from a grid to rural India may cost more to the government. However, renewable energies can be of best plan when it comes to rural India. Renewable energies such as solar energy or wind energy or hybrid systems can be used for power consumption in villages where it will discard the use of the supply line from the electricity supply boards.

IMPORTANCE OF SOLAR RADIATION

The amount of solar energy received by the Earth in 1 hr. is more than the yearly world energy consumption and interruption distribution is non-uniform. Solar energy can be directly or indirectly transformed into electricity by the resources of numerous techniques. Out of them, concentrated solar power with its many arrangements of solar photovoltaic (PV) with diversity of materials can harvest significant amount of electricity. PV cell is an electrical device that changes the energy of sunlight directly into the electricity by photovoltaic effect. There are many materials which are studied for solar PV applications. Different geometries of the solar cell devices are also studied to increase the overall quantum efficiency of the solar cell devices.

REQUIREMENTS TO SOLAR ENERGY FOR RURAL INDIA

The availability of Solar radiation is the key for establishing the solar power for use in rural India. It is well known that India is the 7th largest country in the world due to which it can be considered rich in solar profile due to its landmass of 2.9 million km. The average global horizontal irradiance of solar radiation is around 5.0 -5.5 KWh/m2/Day while the average direct normal irradiance is around 4.5-5.0 KWh/m2/Day in most of the Indian states. Moreover, this much of solar energy is sufficient to produce around 6,081,709 TWh/year, which puts India in the list of top five countries of the world [1]. After the analysis of all these figures, it is observed that there are many regions which receive solar radiation of more than 5 kWh/m2/Day and thus make these regions solar hotspots in India for the solar energy generation specifically for rural India. It is mentioned in one of the literatures report the Western Ghats, Eastern Ghats, Gangetic plains, Thar deserts, and Gujarat plains may be considered the solar hotspots in India which covers around 58% of the total land mass (~ 1.89 million kms of the total area) [2].

Land availability considered as an important parameter for utility-scale power generation referred to as solar land. A solar utility-scale solar power plant has large land use energy intensity as compared to fossil-based power plant [3]. For setting up a solar power plant of more than 20 MWac capacity around 7.9 Acres/MW of total land area is required [4]. Ample amount of wasteland is available in the India which can be used for installation and development of utility-scale solar power plant. Developing a utility-scale solar power plant on wasteland doesn’t create any environmental pressure on agricultural systems because wasteland is neither fit for residential purpose nor for any type of agriculture purpose. Sacristy of wasteland causing many problems to many Mediterranean countries. They are facing environmental pressure on their agricultural land due to ground-mounted photovoltaic installations. The National Remote Sensing Centre has analysed the land of India and by analyzing that at last it has been found that around 46.7 million hectares of wasteland are available in India. Aggregation of land may be an execution challenge, but we are not considering that as a limiting factor to calculate the theoretical potential. Moreover, India has a significant amount of wasteland available.

In India, the effect of external costs (installation time, fuel supply risk, water consumption, pollution and currency exchange rate) in solar power generation is minimum as compared to conventional power sources which are another advantage for solar power developers in setting up a large utility-scale power plant. The average cost of various types of electricity generation and to quantify some of the external costs. Some forms of power generation have very significant external costs to the community and the economy but solar power has more merits in comparison to other sources of power.

BASIC CONCEPT OF SOLAR CELL

In order to generate electricity, a solar cell works in several steps:

1. Photons strike the solar cell surface and are absorbed by a semiconducting material.

2. The absorbed photons create electron hole pairs that are either dissipated as heat or travel through the cell.

3. The construction and material properties of the solar cell, usually a p-n junction, permit the electrons and holes only to flow in one direction, thus creating direct current (DC).

4. Solar cells are arranged in arrays to create usable amounts of DC electricity.

5. An inverter can convert the power to alternating current (AC).

INORGANIC MATERIALS FOR SOLAR CELL APPLICATIONS

The solar energy can be converted into electrical energy by using the solar cell devices which are made up of semiconducting devices. There are numerous semiconducting materials available for the production of solar cells. Silicon semiconducting material has the maximum share in the photovoltaic industry till date instead of by being a costly material. Furthermore, comparatively little attention has been paid to low-cost, non-toxic, inorganic solar cell technologies (Musselman et al., 2010) [6]. A report in 2009 (Wadia et al., 2009) [7] had identified nine inorganic semiconductors that were identified as significant potential for electricity generation with material extraction costs less than crystalline silicon. The apparent advantages of low-temperature, atmospheric, solution-based synthesis in preference to the high cost of vacuum deposition methods have also been highlighted (Gutowski et al., 2009) [8]. Cu2O, in particular, is known to be easily synthesized from solutions at room temperature (Golden et al., 1996) [9]. Cu2O is a p-type semiconductor and is most commonly paired with ZnO as the n-type counterpart (Musselman et al., 2010); however, a significant range of other inorganic materials have been assessed in terms of potential solar cell electricity generation (Wadia et al., 2009). The potential electricity generated from various inorganic materials in terms of known reserves and annual production can be seen. Therefore, in many cases, a single year’s production of a material has the potential to meet global energy consumption. Similarly, the raw material cost in terms of US cents per Watt generated has also been assessed (Wadia et al., 2009).

Other than these materials, Copper Indium Gallium Diselenide (CIGS) and Copper Zinc Tin Sulphide (CZTS) materials are also explored as the absorber layer for the applications in thin film solar cells for developing the solar module. CdTe (Cadmium Telluride) also used for making a thin film but because of its toxic nature, it is avoided for commercial purposes.

SOLAR PV SYSTEM SIZING

1. Determination of power demand

The first and fore step in designing a PV system is the calculation of load consumption which is given below [10]:

1.1 Calculate total Watt-hour/day for each load

Total Watt-hours per day which is consumed by the loads is calculated by adding the Watt-hour that is needed for all loads.

1.2 Calculate total Watt-hour/day required from the PV system

To achieve the total Watt-hour/day from the PV system multiply the total load Watt-hour/day times 1.3 (the energy lost in the system).

2. Sizing of PV module system

Power generated by PV system depends on the different size of PV modules. The size of the PV module and climate of site location are the factors on which peak watt (Wp) produced (which is required to produce the power needed for loads) depends upon. “Panel generation factor” has to be considered which varies for different site locations. Calculations are as follows to determine the sizing of PV module:

2.1 Calculate the required Watt-peak rating for PV modules

Divide the total Watt-hour/day needed from the PV modules to get the total Watt-peak rating needed to run the loads.

2.2 Calculation for the number of PV panels

Divide the answer obtained in 2.1 by the rated output Watt-peak of the PV module. Increase any fractional part of result to the next higher full number which will be the number of PV modules required. Calculated results will depend on the number of PV panels being used. If the modules are installed more, than more efficiency if less then, less efficiency.

3. Sizing of Inverter

To supply AC power to the AC loads in the system an inverter is used. The input rating of the inverter should never be lower than the load. The voltage of inverter and battery must be same.

The size of the inverter must be large for stand-alone systems and should be 25-30% bigger than total Watts of load. In case of load type is motor then the size of inverter must be minimum 3 times the capacity of the load.

4. Sizing of Battery

Deep cycle battery type is usually recommended. Deep cycle battery is specifically designed to be discharged day after day for years. The battery should be large enough to store sufficient energy required for a day as well as for the night. Calculations for sizing of a battery are given:

1. Calculate total Watt-hours/day used by loads.

2. Divide the total Watt-hours/day used by 0.85 for battery loss.

3. Divide the answer obtained in item 4.2 by 0.6 for depth of discharge.

4. Divide the answer obtained in item 4.3 by the nominal battery voltage.

5. Multiply the answer obtained in item 4.4 with days of autonomy i.e. the number of days that you need system to operate when there is no power produced by PV panels.

To get the required Ampere-hour capacity of deep-cycle battery

Battery Capacity (Ah) =Total Watt-hours per day used by appliances x Days of autonomy

(0.85 x 0.6 x nominal battery voltage)

5. Sizing of Solar charge controller

The sizing of solar charge controller is to take the short circuit current (Isc) of the PV array, and multiply it by 1.3 times.

Solar charge controller rating = Total short circuit current of PV array x 1.3

CHALLENGES/BARRIERS FOR SOLAR SECTOR DEVELOPMENT

The two common barriers in the promotion of PV market in India are lack of research and development sector focussed on solar energy development and the fund’s availability. Also, the people awareness and the availability of technologies are other barriers which hold back the growth of the market. The following are some of the barriers in the flourished growth of PV technologies which is required to fulfil the demand of electricity in rural India.

1. Technological barriers

In Indian subcontinent the following points are important:

· The solar technology in India is comparatively new and so the risks associated with this technology is high.

· The evaluation and performance of technology, developed in other countries and used in India, is still unknown.

· The primary technological barrier is the lack of research and development and manufacturing facilities for setting up large scale power plant.

· Lack of awareness, poor quality, and lack of financial support is also one of the reasons for slow development in this direction.

However, India is trying to increase manufacturing, research and development facilities for the growth and development of solar power sector.

In the year 2016, India’s cell and module manufacturing capacity now stand at 1212 MW and 5620 MW respectively, whereas countries like USA, China, Germany, Malaysia etc. [11] are capable of multi-giga watt production according to the Ministry of New and Renewable Energy (MNRE). The average size of the Indian solar cell and module manufacturing unit is just about 86 MW and 69 MW respectively per annum as per the data released by the government. Therefore, right now India mostly depends on the foreign suppliers and foreign solar market to meet the solar PV requirement.

Other than the technological barriers, the following are some other barriers which are to be considered for the successful development and implementation of the solar power sector in India.

2. Policy and regulatory barriers

3. Financing barriers

4. Infrastructure barriers

CONCLUSION

In conclusion, it is worth to mention that India has also started its journey towards a sustainable future by using the available solar energy for electricity generation and distribution in rural and urban areas. The proliferation of PV technology into the market is crucial, especially when the market development is in the nascent stage and is dominated by the rural population. However, right now the motivational factors are not providing a boost to the growth of the solar utility market because of many factors such as poor infrastructure, lack of financing, insufficient technology etc. Nowadays, research based on different inorganic and organic solar cells materials is going on for the development of highly efficient solar cell device and solar module so as to electrify the rural part of India. Furthermore, many new programs have also been launched by the government which will definitely attract big solar power players from across the world to develop India as a hub for solar power projects. In this paper, the status of solar photovoltaics in India, materials required for solar cell and module development, calculation required for making the solar sector ready for use, current barriers and challenges are discussed.

REFERENCES

1. [bookmark: _Hlk536648425]U.S Department of Energy. Open data catalog; 2016. Available at: ?http://en.openei.org/doe-opendata/dataset/solar-resources-by-class-and-country/resource/3e72f32a-7de1-4e5d-a25a-76928769625f?. [Last accessed 24 September 2016].

2. Ramachandra TV, Jain Rishabh, Krishnadas Gautham. Hotspots of solar potential in India. Renew Sustain Energy Rev 2011;15.6:3178–86.

3. Murphy DJ, Horner RM, Clark CE. The impact of off-site land use energy intensity on the overall life cycle land use energy intensity for utility-scale solar electricity generation technologies. J Renew Sustain Energy 2015;7(3):033116.

4. Ong S, Campbell C, Denholm P, Margolis R, Heath G. Land-use requirements for solar power plants in the United States. National renewable energy laboratory, Office of Energy Efficiency & Renewable Energy; 2013 June. Report No.: NREL/TP-6A20-56290

Contract No.: DE-AC36-08GO28308.

5. Böer, K.W., 2016. Solar cells. Available at: http://www.chemistryexplained.com/Ru-Sp/Solar-Cells.html (accessed 03.09.16).

6. Musselman, Kevin P., Andreas Wisnet, Diana C. Iza, Holger C. Hesse, Christina Scheu, Judith L. MacManus?Driscoll, and Lukas Schmidt?Mende. ‘Strong efficiency improvements in ultra?low?cost inorganic nanowire solar cells.’ Advanced Materials 22, no. 35 (2010): E254-E258.

7. Wadia, Cyrus, A. Paul Alivisatos, and Daniel M. Kammen. ‘Materials availability expands the opportunity for large-scale photovoltaics deployment.’ Environmental science & technology 43.6 (2009): 2072-2077.

8. Gutowski, Timothy G., Matthew S. Branham, Jeffrey B. Dahmus, Alissa J. Jones, Alexandre Thiriez, and Dusan P. Sekulic. ‘Thermodynamic analysis of resources used in manufacturing processes.’ Environmental science & technology 43, no. 5 (2009): 1584-1590.

9. Golden, Teresa D., Mark G. Shumsky, Yanchun Zhou, Rachel A. VanderWerf, Robert A. Van Leeuwen, and Jay A. Switzer. ‘Electrochemical deposition of copper (I) oxide films.’ Chemistry of Materials 8, no. 10 (1996): 2499-2504.

10. Rathore, Pushpendra Kumar Singh, Shailendra Rathore, Rudra Pratap Singh, and Sugandha Agnihotri. ‘Solar power utility sector in india: Challenges and opportunities.’ Renewable and Sustainable Energy Reviews 81 (2018): 2703-2713.

11. Nampoothiri M. Resolve energy consultant. Solar in India breaches the 2 GWbarrier; Wind sector continues to stagnate; 2013 Oct. Available at: ?http://www.re-solve.in/perspectivesand-insights/solar-in-india-breachs-the-2-gw-barrierwind-sector-continues-to-stagnate/?. [Accessed 10 May 2016].

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