How Is Solar Energy A Source Of Electricity?
Solar energy refers to the light and heat that comes from the sun that can be captured and converted into electricity. Solar cells or photovoltaic (PV) cells convert sunlight into direct current electricity using semiconducting materials like silicon (the same material used in computer chips).
When sunlight strikes the semiconductor in a solar cell, electrons are knocked loose and flow out of the material as electricity. The electricity generated by a solar cell can be used directly to power equipment or charge batteries, or it can be fed into the electric grid to offset power that would otherwise be supplied by conventional power plants (energysage.com [1]). Therefore, solar energy offers a renewable and sustainable way to generate electricity with minimal environmental impact.
[1] https://www.energysage.com/solar/solar-energy-storage/how-does-solar-work/
How Solar Panels Work
Solar panels work through the photovoltaic effect, which allows solar panels to convert sunlight into electricity. When photons from sunlight hit the solar panel, they knock electrons free from the atoms of the semi-conductor material used in solar cells. The loose electrons flow and generate an electric current.
The most common semi-conductor material used in solar panels is silicon. Silicon atoms are arranged in a crystal structure, with each silicon atom sharing electrons with four of its neighbors. Knocking an electron loose allows it to flow freely. The flow of these electrons from the solar energy is what creates electricity.
Solar cells are specially treated strips of this semi-conductor material that generate electricity. Many solar cells together make up a solar panel. The silicon solar cell was first invented in 1954 by scientists at Bell Labs. Since then, solar panel technology has continued improving in efficiency and lowering costs.
When sunlight, made up of photons, hits the solar panel surface, electrons are knocked loose from the atoms of the silicon semi-conductor material. The electrons flow from the solar cells into metal conductors. This flow of electrons is captured and generated as direct current electricity. Inverters then convert the DC into alternating current (AC), which is the form of electricity used in homes and grids.
In summary, solar panels can generate electricity from sunlight through the photovoltaic effect. When photons hit the semiconductor material, electrons are set loose to flow as electric current.
Types of Solar Panels
The most common types of solar panels can be divided into silicon and thin-film solar panels.
Silicon solar panels make up around 90% of the solar panel market. They are made from silicon cells and the two main types are monocrystalline and polycrystalline solar panels. Monocrystalline solar panels are made from a single cylindrical silicon crystal, making them more efficient with average module efficiency around 15-20%. Polycrystalline solar panels are made from multiple silicon crystals fused together, so they tend to be slightly less efficient than monocrystalline, with average efficiency around 13-16% [1].
Thin-film solar panels are made by depositing photovoltaic material onto substrates like glass or plastic. They are less efficient than crystalline silicon panels, averaging around 7-13% efficiency. However, they can be easier to manufacture at a lower cost. The most common thin-film materials are cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and amorphous silicon (a-Si) [2].
When comparing efficiency, monocrystalline silicon solar panels tend to be the most efficient while thin-film panels are generally the least efficient. However, real-world performance depends on installation factors too. The type of solar panel chosen for a system needs to balance efficiency, cost, and the requirements of the specific site.
Solar Installations
Solar panels can be installed in a variety of ways to generate electricity. Some of the most common installations include rooftop solar panels, solar farms, and community solar projects.
Rooftop solar panels are installed on the roofs of homes and businesses. They allow property owners to generate their own electricity and offset their energy usage. Rooftop solar is popular in residential areas as well as on large commercial buildings. The panels are mounted on racks that are attached to the roof and angled to maximize sun exposure.
Solar farms, also known as utility-scale solar, consist of ground-mounted solar panel arrays over large plots of land. Solar farms can cover hundreds of acres and generate massive amounts of electricity that is fed into the electric grid. According to the Office of Energy Efficiency & Renewable Energy, utility-scale solar accounts for over 60% of total solar capacity in the United States (Source).
Community solar allows households and businesses to share the benefits of solar power even if they can’t install panels on their own properties. Community solar farms feed electricity directly into the grid. Customers subscribe to portions of the farm and receive credits that reduce their electricity bills.
Storing Solar Energy
One of the biggest challenges of solar energy is that it is only available when the sun is shining. Therefore, most solar power systems need a way to store the energy for use when the sun is not out. There are several methods for storing solar energy:
Batteries
Batteries are the most common way to store solar energy. The most popular types of batteries used are lithium-ion batteries, lead-acid batteries, and flow batteries. Batteries can store solar energy captured during the daytime for use at night. They allow solar energy to be used on demand, even when the sun is not shining [1].
Pumped Hydro Storage
Pumped hydro storage works by using excess solar electricity to pump water uphill into a reservoir. When power is needed, the water is released back down through hydroelectric turbines to generate electricity. This is currently the largest-capacity form of grid energy storage [2].
Thermal Energy Storage
Thermal storage systems use excess solar heat to warm up materials like molten salt. The stored heat can be used to generate electricity on demand, even when the sun isn’t shining. This allows solar thermal power plants to provide electricity day and night.
Transmitting Solar Electricity
Solar electricity can be transmitted in a few different ways depending on the scale of the solar installation and whether it is connected to the main electrical grid or not.
For large, utility-scale solar farms, the electricity generated is connected to the main power grid. This allows the solar electricity to be distributed across the existing electrical infrastructure to homes and businesses connected to the grid. While there are some transmission losses of around 3% per 1000 km traveled, transmitting solar electricity through power lines is feasible and economical over long distances (source).
On a smaller scale, solar electricity can be used to power microgrids or mini-grids that serve a localized collection of users. These operate independently from the main grid but allow solar power to be shared efficiently within a community, campus, or group of buildings.
Off-grid solar systems are not connected to any external electrical infrastructure. The solar electricity generated is stored locally in batteries and used to directly power the loads within the off-grid home or facility.
So whether connected to the larger grid or operating as a self-contained system, solar electricity can be effectively transmitted to where it is needed through electrical infrastructure or storage.
Cost of Solar
The cost of solar power has declined significantly over the past decade, making it more affordable and accessible. The main costs for a residential solar system include the solar modules, inverter, racking and electrical components. Prices for solar panels have dropped around 90% since 2009, with average module prices now around $0.20 per watt.
In addition to equipment costs, there are soft costs like installation labor, permitting fees and customer acquisition. These soft costs can account for over 50% of the total price of an installed solar system. Efforts to streamline processes and reduce red tape have helped lower soft costs.
There are also federal and state financial incentives like tax credits and rebates that lower the net cost of going solar. The federal Investment Tax Credit provides a 26% tax credit for systems installed in 2022, which will drop to 22% in 2023. Many states and utilities offer additional rebates and incentives.
With declining solar equipment prices and available incentives, the payback period for a residential solar system now averages around 6-8 years in many parts of the U.S. This makes solar energy a financially viable long-term investment for homeowners.
Source: https://understandsolar.com/solar-energy-vs-coal/
Solar Energy Adoption
The adoption of solar energy has increased rapidly over the past decade, led by countries like China, the United States, Japan, and Germany. China is the global leader in total installed solar capacity, accounting for over 30% of worldwide solar installations as of 2019 [1]. The growth in China has been driven by strong policy support like feed-in tariffs, power purchase agreements, and renewable energy targets.
The United States has also experienced major growth in solar, with over 100 gigawatts of solar capacity installed as of 2021. Federal tax credits have played a key role in boosting U.S. solar adoption. Many individual states have also implemented renewable portfolio standards that require utilities to procure a certain percentage of electricity from renewable sources like solar.
Globally, solar energy capacity is projected to continue its rapid growth in the coming decades. The International Energy Agency predicts global solar capacity will reach over 5,500 gigawatts by 2040, a fivefold increase from 2020 levels. This growth will be supported by improving technology and declining costs, as well as favorable government policies.
Environmental Impact
Solar energy has a much lower environmental impact compared to traditional fossil fuels like coal and natural gas. According to a report by the Climate Reality Project, solar energy generates 95-97% fewer air pollutants than coal power plants for every unit of energy produced. Solar panels require essentially no water to generate electricity, while fossil fuel power plants are a major consumer of water resources.
In terms of carbon emissions, solar energy emits up to 4.3 times less CO2 per kilowatt-hour (kWh) compared to coal. Widespread adoption of solar power can help significantly reduce greenhouse gas emissions and mitigate climate change. According to the Solar Energy Industries Association, the solar energy currently installed in the U.S. offsets over 80 million metric tons of CO2 annually, equivalent to taking over 17 million cars off the road.
Future of Solar
The future looks bright for solar energy. As technology improves, solar panels are becoming more efficient and cost-effective. Some key innovations that will shape the future of solar include:
Improving solar cell efficiency – Companies are developing new materials and techniques to improve the amount of sunlight that can be converted into electricity. Perovskites are emerging as a promising material that could achieve over 25% efficiency. Researchers are also working on improving manufacturing processes to reduce waste.
Thin and flexible solar panels – New solar panels are being made thinner, lighter and more flexible so they can be installed in more places. Flexible solar panels could be applied to curved surfaces like car roofs or wrapped around poles. Thin solar shingles are being developed to integrate directly into roofs.
Solar forecasting – Accurately forecasting energy production from solar panels will help better integrate solar into the grid. New algorithms use weather modeling and irradiance data to predict power output.
Floating solar arrays – Installing floating solar panel systems on bodies of water avoids taking up valuable land. The water also cools the panels, improving their efficiency.
The International Renewable Energy Agency predicts solar photovoltaic power capacity will reach over 8,500 gigawatts globally by 2050, with some experts believing it could grow even faster. With continuing innovations and falling prices, solar energy has a very bright outlook to become a major electricity source worldwide.
Sources:
Renewable Energy, International Renewable Energy Agency
