Energy is the primary need for human life. For living, we need cellular energy that we gather through various metabolic processes. The first form of this chemical energy, though, comes from photosynthesis taking place in green plants and algae. Even to carry out our day-to-day activities, we depend on various forms of energy. These energies primarily come from fossil fuels. Fossil fuels are formed by millions of years of geological processes. Since our consumption of these fuels is higher, it will be difficult to replenish fossil fuels during the life span of a human being. Apart from their dwindling resources, fossil fuels also cause severe environmental impacts due to burning. There is a growing push and adoption of renewable, cleaner alternate energy resources.
Capturing the Sun God’s Power
Ever since humans evolved on this planet, we have been looking at the sun as a divine superpower. All civilisations across continents have revered the sun and utilised its energy for lighting and heating purposes. The Greeks and Romans, for example, designed their homes to capture the sun’s warmth during the day, using materials like stone and glass to enhance this effect. The earliest documented use of a solar oven dates back to the 18th century. Swiss physicist Horace-Bénédict de Saussure built a solar hot box in 1767, which was essentially an insulated box with a glass cover to trap solar heat.
However scientific studies on utilising solar power started only during the 19th century. In 1839, French physicist Alexandre Edmond Becquerel discovered the photovoltaic effect, which describes the generation of an electric current when certain materials are exposed to light. This laid the foundation for modern solar cells. The first practical solar cell was constructed by Charles Fritts in 1883 using selenium and gold. It had an energy conversion efficiency of about 1%. In 1887, a significant scientific breakthrough occurred when Heinrich Hertz, a German scientist, made a pioneering discovery of the photoelectric phenomenon. As a result of these developments, a pioneering solar cell was devised by Aleksandr Stoletov, a prominent Russian scientist, utilising the principles of the photoelectric effect.
Following the elucidation of the photovoltaic effect and the photoelectric effect, researchers worldwide persisted in their endeavours to develop solar cell models and designs. However, none of these endeavours yielded commercially feasible outcomes. The 1950s marked a significant turning point in the field of solar energy as physicists at Bell Laboratories in New Jersey, United States, recognised the superior efficiency of semiconducting materials, particularly silicon, compared to selenium. This discovery paved the way for the development of the first commercially viable solar cell, which achieved an energy conversion rate of 6 per cent. The main people credited with the development of the initial silicon solar cell were Daryl Chapin, Calvin Fuller, and Gerald Pearson of Bell Labs.
Structure of Solar Cell
A solar cell, also known as a photovoltaic cell, is a semiconductor device that converts sunlight into electrical energy. It has a specific structure that allows it to harness the energy of photons from sunlight. Here’s a basic outline of the structure of a typical silicon-based solar cell:
1. Top Contact/Grid Electrode (Front Surface): The top layer of the solar cell is a metal grid or a transparent conducting oxide (TCO) layer. This grid or layer allows sunlight to pass through and reach the semiconductor material while also providing electrical contact to collect the generated electrons.
2. Antireflection Coating (Optional): Some solar cells have an antireflection coating on the front surface. This coating helps reduce the reflection of sunlight, allowing more photons to be absorbed by the cell.
3. Emitter Layer: Beneath the top contact, there is an emitter layer. This layer is typically made of a thin layer of a different semiconductor material (such as boron-doped silicon). It helps create an electric field within the cell and assists in the separation of electrons and holes.
4. Base Layer (P-N Junction): Below the emitter layer, there is the base layer. It is made of a different type of semiconductor material (often phosphorous-doped silicon) and forms a junction with the emitter layer. This is called the P-N junction. It’s a critical part of the solar cell where electron-hole pairs are generated.
5. Back Surface Field (Optional): Some solar cells have an additional layer at the back surface, called the back surface field. It is designed to further improve the collection of electrons.
6. Back Contact (Back Surface): The back contact is usually a metal layer that covers the entire back surface of the solar cell. It provides a path for the electrons to be collected and sent out of the cell.
7. Anti-Reflective Coating (Back Surface, Optional): Similar to the front surface, some solar cells may have an antireflection coating on the back surface as well.
8. Encapsulation (Front and Back): Solar cells are typically encapsulated to protect them from environmental factors like moisture, dust, and physical damage. This encapsulation is done using materials like glass and special polymers.
It is important to note that there are different types of solar cells (e.g., monocrystalline, polycrystalline, thin-film), and their internal structures may vary. However, the basic principles of generating electricity from sunlight through the photovoltaic effect remain the same. The arrangement and characteristics of the layers may be tailored to optimise performance for specific applications or to make use of different semiconductor materials.
Solar Energy in India
India possesses a significant capacity for harnessing solar energy. The country’s annual incident energy amounts to around 5,000 trillion kilowatt-hours (kWh), with the majority of regions receiving a daily average of 4-7 kWh per square metre. The potential for scalability of solar photovoltaic power in India is substantial. India’s interest in solar energy began in the 1970s, largely in response to the global oil crises during that decade. This led to the establishment of the Department of Non-Conventional Energy Sources (DNES) in 1982, which later became the Ministry of New and Renewable Energy (MNRE).
Central Electronics Limited, a government-owned enterprise, developed and produced the country’s first solar photovoltaic cell in 1977 and the first solar photovoltaic panel in 1978 as well as the installation and commissioning of India’s first solar power plant in 1992. Subsequently, in the 1990s, numerous other companies entered the solar manufacturing sector. This included two state-owned entities, BEL and BHEL, which also manufactured solar cells primarily for space applications. Additionally, Tata BP Solar, a private joint venture, focused on addressing the emerging terrestrial solar applications. During the 2000s, there was notable growth in the solar sector with the emergence of many other companies including Moser Baer, Indosolar, and Websol.
The government of India initiated various schemes for promoting solar energy. The National Solar Mission was initiated by India in 2010, aiming to achieve a solar power capacity of 20 GW by 2020. However, in 2015, this target was revised and extended to 100 GW by 2022. The rate of solar installations had significant growth inside the country throughout the 2010 decade. As of 2021, the installed capacity of solar photovoltaic (PV) systems in India amounted to 49 gigawatts (GW). As a result, India has achieved a prominent position among the top five nations globally in terms of both yearly deployment and cumulative deployment.
In the year 2020, the government of India declared a commendable objective pertaining to renewable energy, aiming to achieve a capacity of 450 gigawatts (GW) by the year 2030. It is anticipated that a significant portion, ranging from 280 to 300 GW, will be derived from solar energy sources. During the 2021 United Nations Climate Change Conference, commonly known as COP-26, our Prime Minister Narendra Modi made a declaration regarding India’s energy goals, stating that the country aims to achieve a capacity of 500 GW of renewable energy sources by the year 2030, while also striving for carbon neutrality by the year 2070.
Grassroots Applications of Solar Power
These technological developments have resulted in significant social and economic benefits for society. The advances in solar energy production have helped people in remote areas, where there is a lack of proper electric infrastructure. Even in remote forest areas, villagers and forest officials can enjoy the benefits of solar power in lighting their spaces and running appliances like radio or television sets. The biggest beneficiaries are the women folk of the community. Previously, they were using Kerosene or firewood for lighting and cooking purposes. Apart from the physical strains, the smoke emanated from it causes respiratory illness in many women. Appliances working using solar power like solar lanterns, solar cookers, and solar water heating systems have made life easy for these people. The public sector company, Indian Oil’s novel Indoor Solar Cooking System called the ‘Surya Nutan’, can cook enough for a family of four during the day and night using the daily captured sunlight. The device is capable of harnessing solar energy and transforming it into heat using a specifically engineered heating component. It then proceeds to store this thermal energy within a scientifically validated thermal battery, which can then be utilised for indoor cooking purposes. Even though we have developed every appliance that works with solar power, from calculators to aircraft, it has not received the acceptance from the public as it should have. The primary reason is the high cost involved with technology compared to other cheaper technologies available today. Many groups are working on technologies that can be made affordable to the common man. A Shimla-based NGO, Himalayan Research Group (HRG), has developed low-cost solar water heaters for people in the hills.
Our farmers have to rely on the energy from the grid or diesel generators to run the pump when they are pumping water for irrigation, which causes enormous delays and economic strain. They would benefit tremendously from having access to an efficient watering system like the Solar Water Pump. It does this by guaranteeing that their fields have a steady and unending supply of water, which in turn boosts crop production. The Ministry of New and Renewable Energy (MNRE) has initiated the PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan) Scheme to facilitate the installation of subsidised solar pumps and distributed solar power plants across the nation. More than 3.5 million farmers across India will benefit from this effort, which is one of the largest clean energy distribution programmes ever undertaken anywhere in the world.
But in future, when we meet a situation where currently available technologies become inoperational, we will not have any other alternative, but to use solar technologies. Solar is the energy for the future. The development in the field is so exhaustive that scientists have developed solar cars, planes and space crafts, thereby reducing our dependence on fossil fuels. Even in spacecraft of our Chandrayaan-3 and Aditya-L1 missions, solar panels have been installed.
Solar Energy Production in India
India has emerged as a global leader in solar energy production, having developed technology to harness solar energy to the maximum in every available free space. We have been successful in operating our airports on solar power. Cochin International Airport in Kerala is the world’s first fully solar-powered airport; many others have followed suit. India’s largest floating solar power project having a capacity of 100MW was commissioned in Ramagundam, Telangana, on July 1, 2022. The historic city of Sanchi in Madhya Pradesh was declared the first solar city in the country on 7September 2023, generating 3 MW of electricity.
Furthermore, the solar energy industry in India has emerged as a significant contributor to the capacity of power generation connected to the grid, in line with the government’s commitment to achieving sustainable economic development. The incorporation of this element has become an essential aspect in effectively addressing the energy needs of the nation and ensuring the stability and reliability of its energy supply. This has resulted in an overall improvement in living conditions and the establishment of economic prospects at the local level.
As a global leader in solar technologies, the country’s Prime Minister Narendra Modi has initiated the ‘One Sun, One World, One Grid’ concept that envisions the development of a connected grid infrastructure that spans different continents, allowing for the efficient sharing and distribution of solar power across the world. The goal is to optimise the utilisation of solar resources, enhance energy security, and reduce greenhouse gas emissions on a global scale. He introduced this concept during the first assembly of the International Solar Alliance (ISA) held in New Delhi in October 2018. The International Solar Alliance is an intergovernmental organisation co-founded by India and France, aimed at promoting solar energy and increasing cooperation among solar-rich countries. It is important to note that ‘One Sun, One World, One Grid’ is a visionary concept that faces various technical, logistical, and geopolitical challenges. Implementing such a global grid would require extensive coordination, investment, and the development of advanced grid management technologies. However, if successful, it could revolutionise the way renewable energy is harnessed and distributed on a worldwide scale. We cannot rely on fossil fuels for a longer period, as they will soon exhaust. Even today, the cost of fossil fuels has become so high that it has become unaffordable for the common man. We need to shift to cleaner, greener alternative sources of energy like solar, hydrogen, etc. Being a country located in the tropics, India has the advantage of reaping solar energy to the maximum and can effectively provide continuous electricity at a cheaper cost in every corner of the country.
*The writer is a science communicator and an adjunct faculty at the National Institute of Advanced Studies, Bangalore. He can be reached at bijudharmapalan@gmail.com
