Solar-Energy Systems – The Heart of a Solar-Energy System
Solar-energy systems produce electricity using sunlight. These systems can be grid-tied, off-grid, or with battery backup. They use photovoltaic cells to convert direct current (DC) sunlight into alternating current electricity.
Concentrating solar power systems use mirrors and tracking systems to focus a large area of sunlight onto a working fluid. The hot fluid then generates electricity or fuels another process.
A photovoltaic power station
A photovoltaic power station is a large solar installation that supplies electricity to the grid. It converts the sunlight into electricity using a system of PV cells made from semiconductor materials, which absorb particles of light and release electrons to create electricity. The electricity is then fed into a transformer, which increases its intensity and voltage so it can be transported along transmission lines.
The energy output of a PV plant is dependent on a number of factors, including the equipment used and the system configuration. The primary energy input is global light irradiance in the plane of the solar panels, which includes both direct and diffused radiation. The performance of a PV system also depends on the soiling and organic matter on the solar panel surface, which can reduce its efficiency.
Moreover, PV solar systems are extremely sensitive to shading, which causes the solar cells to lose power. Even a small portion of a cell or a module in parallel can cause the current to fall dramatically, as it can’t flow through the shaded area. The electrical output of a PV system can decrease as much as 10% per year, depending on the type of panels used.
The solar panels in a PV power station are connected to a control box that produces alternating current electricity. Then, the alternating current is led to a cabinet that transforms it into direct current (DC). Finally, the DC is sent through an inverter, which molds it into a continuous electric current. This is then transformed into a medium voltage by a transformer. It is then transported through transmission lines to consumption centers.
Concentrating solar power
Concentrating solar power (CSP) uses mirrors to focus sunlight into a receiver, which converts the sunlight to heat. This heat drives a heat engine connected to an electrical power generator to generate solar-panel electricity. CSP can be combined with thermal energy storage to produce constant (baseload) electricity.
There are three main types of CSP: trough, dish/engine, and tower. NREL’s Technical Summaries page provides detailed information about each of these technologies, including their environmental impacts and system costs.
Trough systems use sun-tracking mirrors, called heliostats, to focus sunlight on a receiver at the top of a central tower. This heats a heat transfer fluid, which then boils water to generate steam. The steam turns a conventional turbine-generator to produce electricity. The National Renewable Energy Laboratory maintains a global database of trough deployments.
The dish/engine technology uses a field of reflecting mirrors to concentrate sunlight on a central receiver. The heat from the concentrated sunlight is used to provide thermal energy or to drive a thermochemical reactor to produce electricity. It can also be used to produce desalinated water, or for industrial process heating and cooling. Many dish/engine plants do not include any thermal energy storage, although the 5 MW Kimberlina plant in Australia and the Solar Two and Ivanpah solar power plants both included a few hours of thermal energy storage.
Photovoltaic cells
Photovoltaic cells are small semiconductors that convert solar energy into electricity. They are the heart of a solar system and have an efficiency that is constantly improving. They are mainly made from silicon, which is extracted from silica (sand). The crystalline version makes up 95% of today’s PV market.
Sunlight strikes the front of a solar cell and ionizes the semiconductor material, causing outer electrons to break free of their atomic bonds. The electrons flow from the positive layer of the semiconductor to the negative one, creating an electric current that can be harvested by metal contacts on the cell’s front and back surfaces.
When a solar cell is fully exposed to sunlight at Standard Test Conditions, it produces an average of 1 kWp per square metre of area per year. This energy is enough to power many household appliances and can be stored in a battery for use at night, or fed into the grid.
To increase efficiency, the semiconductor material in a photovoltaic cell is “doped”. This involves adding other elements to the silicon that doesn’t chemically react with it. Gallium, for example, helps prevent the oxygen from bonding with boron in the silicon and reduces degradation over time, which is responsible for the current drop that decreases a solar cell’s efficiency. Other methods, such as multi-junction cells, are also helping to increase efficiency.
Solar panels
The solar energy industry is booming and is poised to grow even more with innovations in quantum physics and nanotechnology. This technology will increase the efficiency of solar panels and reduce electricity costs. Moreover, it will also make our environment better. Solar power is an excellent option for consumers looking to reduce their energy bills and make a positive impact on the environment.
Photovoltaic (PV) systems convert solar radiation into electricity through a combination of PV cells and an inverter. These systems are usually mounted on rooftops or in ground-mounted solar farms. They can produce a large low speed car amount of electricity and can be grid-connected or standalone. The productivity of a solar power system depends on the amount of sunlight it receives, which varies throughout the day and year. Moreover, it depends on geographical variations, such as latitude and climate.
Solar panels are made of silicon, which is a natural material found on Earth. It is abundantly available, and it is the second most common element on the planet. In fact, one ton of sand produces as much electricity as burning 500,000 tons of coal.
There are several different types of solar panel, but crystalline silicon (c-Si) is the most popular in the US and the world. There are also thin-film amorphous silica, copper indium gallium selenide, and cadmium telluride panels.
