RENEWABLE ENERGY

1. Context

2. Why use Renewable energy

• Today we primarily use fossil fuels to heat and power our homes and fuel our cars. 
• It’s convenient to use coal, oil, and natural gas for meeting our energy needs, but we have a limited supply of these fuels on Earth. 
• We’re using them much more rapidly than they are being created. Eventually, they will run out. 
• And because of safety concerns and waste disposal problems, the United States will retire much of its nuclear capacity by 2020. 
• In the meantime, the nation’s energy needs are expected to grow by 33 per cent during the next 20 years. 
• Renewable energy can help fill the gap
• Even if we had an unlimited supply of fossil fuels, using renewable energy is better for the environment. 
• We often call renewable energy technologies “clean” or “green” because they produce few if any pollutants. 
• Burning fossil fuels, however, sends greenhouse gases into the atmosphere, trapping the sun’s heat and contributing to global warming. 
• Climate scientists generally agree that the Earth’s average temperature has risen in the past century. 
• If this trend continues, sea levels will rise, and scientists predict that floods, heat waves, droughts, and other extreme weather conditions could occur more often. 
• Other pollutants are released into the air, soil, and water when fossil fuels are burned. 
• These pollutants take a dramatic toll on the environment—and humans. 
• Air pollution contributes to diseases like asthma. 
• Acid rain from sulfur dioxide and nitrogen oxides harms plants and fish. Nitrogen oxides also contribute to smog.
• Renewable energy will also help us develop energy independence and security. 
• Replacing some of our petroleum with fuels made from plant matter, for example, could save money and strengthen our energy security. 
• Renewable energy is plentiful, and the technologies are improving all the time. 
• There are many ways to use renewable energy. 
• Most of us already use renewable energy in our daily lives.

2.1.Hydropower 

• Hydropower is our most mature and largest source of renewable power, producing about 10 per cent of the nation’s electricity. 
• Existing hydropower capacity is about 77,000 megawatts (MW). Hydropower plants convert the energy in flowing water into electricity. 
• The most common form of hydropower uses a dam on a river to retain a large reservoir of water. Water is released through turbines to generate power.
•  “Run of the river” systems, however, divert water from the river and direct it through a pipeline to a turbine. 
• Hydropower plants produce no air emissions but can affect water quality and wildlife habitats. 

2.2.Bioenergy 

• Bioenergy is the energy derived from biomass (organic matter), such as plants. If you’ve ever burned wood in a fireplace or campfire, you’ve used bioenergy. 
• But we don’t get all of our biomass resources directly from trees or other plants. 
• Many industries, such as those involved in construction or the processing of agricultural products, can create large quantities of unused or residual biomass, which can serve as a bioenergy source. 

2.3.Geothermal Energy 

• The Earth’s core, 4,000 miles below the surface, can reach temperatures of 9000° F. 
• This heat—geothermal energy—flows outward from the core, heating the surrounding area, which can form underground reservoirs of hot water and steam. 
• These reservoirs can be tapped for a variety of uses, such as to generate electricity or heat buildings. 
• By using geothermal heat pumps (GHPs), we can even take advantage of the shallow ground’s stable temperature for heating and cooling buildings. 

2.4.Solar Energy 

• Solar technologies tap directly into the infinite power of the sun and use that energy to produce heat, light, and power.

2.5. Wind Energy 

• For hundreds of years, people have used windmills to harness the wind’s energy. 
• Today’s wind turbines, which operate differently from windmills, are a much more efficient technology. 
• Wind turbine technology may look simple: the wind spins turbine blades around a central hub; the hub is connected to a shaft, which powers a generator to make electricity. 
• However, turbines are highly sophisticated power systems that capture the wind’s energy using new blade designs or airfoils. 
• Modern, mechanical drive systems, combined with advanced generators, convert that energy into electricity. 
• Wind turbines that provide electricity to the utility grid range in size from 50 kW to 6 
• Wind energy has been the fastest growing source of energy since 1990.

2.6.Ocean Energy 

• The ocean can produce two types of energy: thermal energy from the sun’s heat, and mechanical energy from the tides and waves. 
• Ocean thermal energy can be used for many applications, including electricity generation. 
• Electricity conversion systems use either the warm surface water or boil the seawater to turn a turbine, which activates a generator. 
• The electricity conversion of both tidal and wave energy usually involves mechanical devices. 
• A dam is typically used to convert tidal energy into electricity by forcing the water through turbines and activating a generator. 
• Meanwhile, wave energy uses mechanical power to directly activate a generator or to transfer to a working fluid, water, or air, which then drives a turbine/generator.

2.7.Hydrogen 

• Hydrogen is high in energy, yet its use as a fuel produces water as the only emission. 
• Hydrogen is the universe’s most abundant element and also its simplest. 
• A hydrogen atom consists of only one proton and one electron. 
• Despite its abundance and simplicity, it doesn’t occur naturally as a gas on the Earth. 
• Today, industry produces more than 4 trillion cubic feet of hydrogen annually. 
• Most of this hydrogen is produced through a process called reforming, which involves the application of heat to separate hydrogen from carbon. Researchers are developing highly efficient, advanced reformers to produce hydrogen from natural gas for what’s called Proton Exchange Membrane fuel cells.

3. Steps were taken by the government to promote Renewable energy

The Indian renewable energy sector is the fourth most attractive renewable energy market in the world. India was ranked fourth in wind power, fifth in solar power and fourth in renewable power installed capacity, as of 2020.

3.1.Distribution of prominent renewable energy Hubs

• Rajasthan
• Gujarat
• Andhra Pradesh
• Karnataka
• Telangana
• Tamil Nadu

3.2.Steps taken

• Permitting Foreign Direct Investment (FDI) up to 100 per cent under the automatic route,
• Waiver of Inter-State Transmission System (ISTS) charges for inter-state sale of solar and wind power for projects to be commissioned by 30th June 2025,
• Declaration of trajectory for Renewable Purchase Obligation (RPO) up to the year 2022,
• Setting up of Ultra Mega Renewable Energy Parks to provide land and transmission to RE developers on a plug-and-play basis,
• Schemes such as Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan (PM-KUSUM), Solar Rooftop Phase II, 12000 MW CPSU Scheme Phase II, etc,
• Laying of new transmission lines and creating new sub-station capacity under the Green Energy Corridor Scheme for evacuation of renewable power,
• Setting up of Project Development Cell for attracting and facilitating investments,
• Standard Bidding Guidelines for tariff-based competitive bidding process for procurement of Power from Grid Connected Solar PV and Wind Projects.

• Deployment of large-scale renewable energy (RE) has the potential to create numerous employment opportunities in rural India in the coming decades. By 2030, it is projected that the clean-energy sectors could provide jobs for around one million individuals in the country.
• However, the expansion of RE may have significant impacts on communities reliant on the land, involving changes in land use, modifications to ecosystems, shifts in livelihoods, and overall effects on land productivity.
• As India progresses in scaling up RE, striking a balance between these interests may result in project commissioning delays, contributing to a waning interest among developers in RE tenders.
• In 2020, wind developers, facing setbacks such as delays in land allocation, sought to terminate power-purchase agreements for approximately 565 MW wind capacity signed with the Solar Energy Corporation of India (SECI), prompting a decline in developers' enthusiasm for RE projects. Commissioning delays not only pose substantial financial risks but also jeopardize the reputation of RE developers.
• In the pursuit of responsible RE deployment and the enhancement of communities in and around project sites, many developers actively support local development activities and community-led programs through corporate social responsibility (CSR) initiatives.
• As an illustration, Tata Power Solar has established integrated vocational training programs for women and youth in multiple project sites.
• Given the pivotal role of project developers in interacting with communities during land acquisition, construction, and operational phases, they play a crucial role in driving responsible practices. Additionally, regulators and investors prioritize assessing the responsible practices of new projects.
• To encourage all developers to contribute to the rapidly growing RE ecosystem and promote responsible practices, two essential prerequisites need to be addressed

SOLAR ENERGY SYSTEMS

 

 

 

1. Context

 

Solar power is the fastest-growing renewable energy technology in the world. Between 2024 and 2030, solar capacity added is expected to account for 80% of the growth in renewable power globally, the International Energy Agency’s ‘Renewables 2024’ report stated 

 

2. Electricity generation

 

• Electricity can primarily be generated through two key methods. The first is electromagnetic induction, a principle discovered by Michael Faraday in 1821, which became commercially applicable around 1890. Even today, this method remains central to most of the world's electricity generation.
• The second approach involves photovoltaic (PV) technology, which relies on semiconductor materials like elemental silicon to convert sunlight directly into electricity. The photovoltaic effect was first observed by Alexander Becquerel in 1839.
• However, it wasn't until 1954 that a functional and efficient solar cell was developed at Bell Laboratories by Chapin, Fuller, and Pearson using doped silicon.
• This achievement was made possible thanks to two pivotal scientific contributions: Albert Einstein’s Nobel Prize-winning explanation of the photoelectric effect, and Jan Czochralski’s method for producing single-crystal silicon, which remains the foundation for most PV cells today.
• Unlike PV systems that feed regulated, taxable electricity into national power grids, technologies such as solar water heaters, solar air heaters, and solar-based cooling systems usually operate independently.
• For example, solar cooling uses an absorption refrigeration process that can cool interiors to as low as 19°C even when the ambient temperature hits 40°C. These standalone technologies are similar to PV panels used in off-grid regions, typically for purposes like charging batteries and powering basic lighting systems.
• Globally, solar insolation—the measure of solar energy received—varies significantly by region. Though solar energy is plentiful, it is scattered over wide areas, making it less concentrated.
• To harness it effectively, various focusing technologies such as parabolic troughs, Fresnel lenses, and other solar concentrators are employed for tasks ranging from cooking and water desalination to thermal heating and electricity production

 

3. How does sunlight generate power?

 

• Photovoltaic (PV) cells are typically composed of semiconducting materials like elemental silicon. Unlike metals such as copper, which are Ohmic conductors (their electrical resistance increases with temperature), silicon behaves as a non-Ohmic material. At room temperature, silicon is a poor conductor, but its conductivity improves as it gets warmer.
• From a quantum mechanical perspective, electrical conduction occurs when electrons occupy a higher energy level known as the conduction band, where they can move freely, similar to how water flows in the ocean. Electrons that remain in the valence band, a lower-energy state, are immobile and do not contribute to electrical current.
• To move an electron from the valence band to the conduction band, energy must be supplied. This energy can come from thermal excitation (increased atomic motion at higher temperatures) or from other energy sources such as light.
• Light, depending on the experiment, behaves either as a wave or as individual energy packets called photons. When photons strike electrons in the valence band, they can transfer energy to the electrons, allowing them to rise to the conduction band—if the photon’s energy matches or exceeds the required energy gap.
• This energy gap, known as the band gap and measured in electron volts (eV), must be matched precisely by the photon’s energy for the transition to occur. If a photon has more energy than necessary, the excess is converted to heat, which not only leads to energy loss but can also cause electrons to escape.
• Besides the energy requirement, there's also a symmetry condition for these transitions, though it plays a lesser role in this context. Due to these constraints, silicon-based PV cells cannot utilize the entire solar spectrum efficiently—around 50.4% of the sunlight is unusable. About 20.2% of photons lack sufficient energy to initiate the transition, while 30.2% carry excess energy that’s lost as heat.
• Other semiconducting materials like gallium arsenide, cadmium telluride, and copper indium selenide can absorb different parts of the solar spectrum more effectively. However, their widespread use is restricted by challenges such as limited availability, environmental hazards, and handling complexities

 

4. Silicon Solar Cells

 

 

• In silicon-based photovoltaic (PV) cells, trace amounts of phosphorus and boron are intentionally introduced to create regions that either have an excess of electrons or a shortage of them (known as "holes").
• This results in the formation of a p-n junction, where the difference in electrical charge establishes an electric field. When sunlight hits the surface, this setup acts like a battery, generating an electric potential that drives current.
• When an external circuit is connected, electrons travel from the negatively charged side through the load toward the positively charged side, completing the circuit. This process can continue as long as the cell is exposed to light.
• However, even within the 49.6% of the solar spectrum that is usable, several energy losses still occur. For example, PV cells often heat up to 30–40°C above the surrounding temperature, and this radiative heat loss accounts for around 7% of energy loss.
• An additional 10% loss is caused by differences in the mobility of positive and negative charges, a phenomenon known as the saturation effect, which reduces the generated voltage over time.
• These factors contribute to a theoretical efficiency ceiling of 33.7% for single-junction silicon PV cells, a value known as the Shockley-Queisser limit. Moreover, practical inefficiencies such as non-uniform sunlight exposure and manufacturing inconsistencies between cells (which cause differences in open-circuit voltage) also reduce performance.
• When real-world losses like converting DC to AC and managing peak power output are considered, the actual efficiency of silicon-based crystalline PV cells averages about 25% in laboratory settings, while the best commercial models achieve roughly 20% efficiency. By comparison, natural photosynthesis captures only 3–6% of the sunlight it receives

 

5. What can solar energy and cannot do?

 

• Because natural silicon reflects a significant amount of light, photovoltaic (PV) cells are coated with a transparent anti-reflective layer, typically made from tin oxide or silicon nitride, which also gives them their distinctive blue hue.
• Unlike biological photosystems, which assemble proteins using minimal energy at ambient temperatures, PV technology demands high energy inputs during manufacturing.
• The production of PV cells starts with the Czochralski process, which purifies elemental silicon to about 99% purity by melting and slowly forming it into single-crystal ingots. When these ingots are sliced into thin wafers, roughly 20% of the material is lost as silicon dust.
• Due to the high costs associated with single-crystal silicon, alternative techniques have been developed — for instance, ribbon technology avoids sawing losses, while amorphous silicon cells are more economical. Their natural structural imperfections can be corrected by adding hydrogen, improving performance.
• To capture a wider range of the solar spectrum, multijunction amorphous silicon cells have been engineered. These can theoretically reach efficiencies as high as 42%, though real-world performance typically peaks around 24%. PV technologies are broadly grouped into three generations:

1. First-generation uses thick crystalline wafers (~200 µm),

2. Second-generation relies on thin-film wafers (1–10 µm), and

3. Third-generation includes advanced designs like multijunction tandem cells and quantum dots, which can generate more charge carriers per photon, potentially surpassing the Shockley–Queisser efficiency limit.

 

• The cost of PV-generated electricity has declined sharply—from $4–5 per watt in 2010 to about $2.8 per watt in 2023 (and as low as $1.27 per watt for utility-scale systems), nearly achieving the U.S. SunShot Initiative’s goal of $1 per watt. Breaking down system costs:

• Modules account for 38%,

• Inverters and other electronics for 8%,

• Wiring and mounting contribute 22%, and

• The remaining 33% is spent on balance-of-system (BoS) costs, including labour, permits, administrative expenses, and profit margins.

• Since single-crystal silicon cells are close to their theoretical peak, future cost reductions are most likely in the BoS components. In terms of durability, PV systems lose efficiency at a rate of about 0.5% per year, with most modules lasting 20 to 25 years.
• Interestingly, although tropical and desert climates receive higher solar irradiance, PV modules perform more efficiently in cool, clear conditions due to reduced thermal losses. This makes it challenging for low- and middle-income countries — many of which lie in tropical zones — to fully leverage PV systems, especially given infrastructural limitations and climatic constraints.
• Additionally, air pollution can block 2–11% of solar radiation, and dust accumulation (soiling) can cause an extra 3–4% loss annually.
• Cleaning solar panels is both risky and water-intensive, since the panels become electrically active under sunlight. In densely populated urban areas, PV systems may also intensify the urban heat island effect by trapping heat.
• While other solar technologies can offer some complementary benefits, the extent to which PV systems alone can support a fully carbon-neutral energy future remains a topic of active scientific debate

 

6. Government supported schemes

 

Jawaharlal Nehru National Solar Mission (JNNSM) – 2010

• Launched under the National Action Plan on Climate Change (NAPCC).

• Aimed to establish India as a global leader in solar energy.

• Target revised to 100 GW of solar capacity by 2022 (out of 175 GW total renewable energy target).

• Focus on both grid-connected and off-grid solar power systems.

PM-KUSUM (Pradhan Mantri Kisan Urja Suraksha evam Utthaan Mahabhiyan) – 2019

• Promotes the use of solar energy in the agriculture sector.

• Three components:

  • Component A: Solar power plants (up to 2 MW) on barren land.

  • Component B: Standalone solar-powered agricultural pumps.

  • Component C: Solarisation of existing grid-connected pumps

 

 

 

For Prelims: General issues on Environmental ecology, Bio-diversity & climate change For Mains: GS-III: Conservation, environmental pollution and degradation, environmental impact assessment.

 

Previous Year Questions   1.Consider the following statements: (2016) The International Solar Alliance was launched at the United Nations Climate Change Conference in 2015. The Alliance includes all the member countries of the United Nations. Which of the statements given above is/are correct? (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2 Answer (a)   Statement 1 is correct. The International Solar Alliance (ISA) was launched at the United Nations Climate Change Conference (COP21) in 2015 in Paris. Statement 2 is incorrect. Initially, the ISA was intended for solar-rich countries lying fully or partially between the Tropics of Cancer and Capricorn. However, in subsequent years, the membership was expanded to include all UN member countries

 

Source: Indianexpress