Understanding Solar Energy and Exploring its Types and Applications
Renewables are all the craze nowadays, globally every country wants to shift to renewables to reduce their dependence on fossil fuels as well as to create an independent sustainable energy source. Solar Energy is one of the leading solutions for the renewable transition. Let’s look at what it is -
Energy From the Sun
Basically, Solar energy is as straightforward as its name implies: it is the energy harnessed from the Sun's radiation. The sun emits an enormous amount of solar energy onto Earth, and according to NASA, about 44 quadrillion watts of power to be exact. As a comparison, a large electric power plant produces about 1 billion watts of power. It would take 44 million such power plants to equal the energy coming from the Sun.
But, not all of the Sun’s energy that enters Earth’s atmosphere makes it to the surface. The atmosphere reflects some of the incoming solar energy back to space immediately and absorbs still more energy before it can reach the surface.
The energy that reaches the Earth's surface can be harnessed in two forms: electricity and heat. To better understand how this works, let's explore how we generate both heat and electricity from solar energy.
Solar Photovoltaics (Solar PV)
Photovoltaics (often shortened as PV) gets its name from the process of converting light (photons) to electricity (voltage), which is called the photovoltaic effect. In solar PV, we see a photovoltaic cell, commonly called a solar cell, which is a nonmechanical device that converts sunlight directly into electricity.
A PV cell is made of semiconductor material, when the semiconductor is exposed to light, it absorbs the light’s energy and transfers it to negatively charged particles in the material called electrons. This extra energy allows the electrons to flow through the material as an electrical current. Silicon is, by far, the most common semiconductor material used in solar cells.
Source: EIA
Solar Thermal
Have you ever noticed the solar water heaters on top of some houses? That's an example of solar thermal technology in action.
Solar thermal energy is a form of renewable energy that uses sunlight to generate heat. Instead of converting sunlight directly into electricity, as photovoltaics does, solar thermal harnesses the sun's energy to heat a fluid called and then uses that heat to generate electricity or provide heat for industrial or domestic applications.
The process begins with the capture of solar radiation by solar collectors. Collectors are classified into three types: flat plate, evacuated tube, and concentrated, but they all share the same objective: to capture the sun's energy and use it to heat a fluid circulating through them, such as water or thermal oil. Solar water heating and Concentrated Solar Power (CSP) are the two common solar thermal technologies.
Concentrated Solar Power (CSP)
CSP technologies use mirrors to reflect and concentrate sunlight onto receivers that collect the solar energy and convert it to heat. The thermal energy can then be used to produce electricity via a steam turbine or heat engine driving a generator. It can also be used in a variety of industrial applications, like water desalination, enhanced oil recovery, food processing, chemical production, and mineral processing.
Source: US DOE
Solar PV is the most common application for large scale as well as residential solar applications, so let’s understand in more depth on how the system works.
The photovoltaic (PV) cell is the fundamental component of a PV system. These cells are electrically linked together and housed in a sealed, weather-resistant panel, often referred to as a module. PV panels come in various sizes and capacities, with their electricity output increasing based on the number of cells they contain or the total surface area of the panel. The average efficiency of a solar panel, that is the rate at which a solar panel converts sunlight into usable energy is around 22%.
Multiple PV panels can be connected together to form a PV array, which can consist of just a couple of panels or several hundred. The total electricity generation capacity of a PV array depends on the number of panels it includes.
PV arrays must be mounted on a stable, durable structure, called mounting structures, these support the array and withstand wind, rain, hail, and corrosion over decades. These structures tilt the PV array at a fixed angle determined by the local latitude, orientation of the structure, and electrical load requirements. To maximize annual energy production, panels are typically oriented to face directly south in the northern hemisphere (or directly north in the southern hemisphere), at an angle that optimizes both performance and cost-effectiveness.
Now, PV cells generate Direct Current (DC) electricity, the DC current from the modules can be used to charge batteries, which can help power the system when it is night and the panels are not producing electricity. But the batteries can store only a fixed amount of energy, when the solar PV system is running it is continuously producing electricity which can sometimes over charge the batteries. Charge Controllers help to mitigate this issue, it controls the flow of energy from the solar panel to the battery and back, ensuring the power doesn’t exceed the load that the battery can handle.
If the system is connected to the grid, a solar charge controller is not needed. That’s because the grid system will store any excess energy.
But nearly all electricity supplied to our homes or businesses run on Alternating Current (AC). Here is where devices called inverters come into play, they convert the DC electricity from the solar panels/batteries into AC electricity.
All the components of the system are connected through wiring –
Array Wiring connects individual solar panels in series or parallel to create an array. The wiring configuration determines the system's voltage and current. The direct current (DC) from the solar panels/batteries is carried through wiring to the inverter, where it is converted into alternating current (AC) for use in homes or businesses.
After the electricity is converted to AC, it is routed through wiring to power appliances or, in grid-connected systems, to feed excess electricity back into the utility grid. Additional wiring is used for proper grounding of the system, ensuring safety and protection from electrical faults.
Now, lets take a look at some applications of Solar PV Systems
1. Residential Solar Power Systems: Homeowners can install solar panels on their roofs to generate electricity for their own use, reducing reliance on the grid and lowering electricity bills. This type of installation can either be connected to the grid (grid-tied) or be part of an off-grid system with energy storage (batteries) for homes in remote areas.
2. Commercial and Industrial Solar Power Systems: Many businesses install solar panels on the roofs of their buildings to take advantage of unused space while offsetting their electricity costs. Large businesses or industrial complexes with expansive land may install ground-mounted solar arrays, often as part of their commitment to corporate sustainability or to generate power for their operations.
3. Utility-Scale Solar Power Plants: These plants are typically, is a large solar energy system designed to generate electricity on a commercial scale, typically owned and operated by utility companies or power providers and are located in regions with ample sunlight and open space. The electricity generated by the solar panels is fed into the grid, where it is then distributed to consumers, including homes and businesses.
Challenges of Solar Energy
1. Intermittency and Reliability: Solar energy production is dependent on sunlight, which is intermittent. It does not generate power at night or during cloudy or rainy days. This variability can create challenges for ensuring a constant and reliable power supply, particularly in areas where sunlight is less predictable.
2. Space: Solar panels require large amounts of space to generate significant amounts of electricity. This can be a limitation in densely populated areas or places where land is scarce or expensive.
3. Efficiency: Although solar panels of todays are capable of providing an efficiency upwards of 20%, it is still lower than traditional thermal power plant which offer efficiency of around 40%.
4. Environmental Impact: The manufacturing process of solar panels requires raw materials such as silicon, metals, and chemicals, and it generates emissions and waste. The mining of these materials can also lead to environmental degradation. Advances in recycling technologies are helping to recover valuable materials like silicon and rare earth metals from old panels, reducing the need for new mining.
5. Cost & Pay back Period: The upfront cost of installing solar panels and associated infrastructure can be a significant barrier to adoption, particularly for residential systems. Although solar energy can save money over the long term by reducing electricity bills, the payback period, the time it takes for the savings to equal the initial investment, can still be several years.
Solar Energy in India
National Institute of Solar Energy (NISE) has assessed the country’s solar potential of about 748 GW assuming 3% of the waste land area to be covered by Solar PV modules. Solar energy has taken a central place in India’s National Action Plan on Climate Change with National Solar Mission (NSM) as one of the key Missions.
Recently, Shri Prashant Kumar Singh, Secretary of the Ministry of New and Renewable Energy, emphasized that a significant portion of growth in renewable energy (RE) will stem from the solar sector. Initiatives like PM Surya Ghar and PM KUSUM are driving substantial demand, supported by rapid advancements in manufacturing capabilities.
PM Surya Ghar: Muft Bijli Yojana, aims to increase the share of solar rooftop capacity and empower residential households to generate their own electricity. The scheme has an outlay of Rs 75,021 crore and is to be implemented till FY 2026-27. The scheme provides for a subsidy of 60% of the solar unit cost for systems up to 2kW capacity and 40 percent of additional system cost for systems between 2 to 3kW capacity. The subsidy has been capped at 3kW capacity. At current benchmark prices, this will mean Rs 30,000 subsidy for 1kW system, Rs 60,000 for 2kW systems and Rs 78,000 for 3kW systems or higher.
PM-KUSUM is aimed at ensuring energy security for farmers in India, along with honouring India’s commitment to increase the share of installed capacity of electric power from non-fossil-fuel sources to 40% by 2030 as part of Intended Nationally Determined Contributions (INDCs). Click here to know more.
These scheme along with other initiatives has helped India’s Solar capacity to surged from a mere 2.6 GW in 2014 to an impressive 91 GW today, with projections indicating it could reach close to 300 GW by 2030. Solar module manufacturing, which stood at 2 GW in 2014, has surged to 60 GW and is expected to surpass 100 GW by 2030.