Learn About Solar Energy: Solar Power Plants Role As a Power Generator

Learn About Solar Energy: Solar Power Plants Role As a Power Generator

Posted 08.09.2012 in Articles by Jess

At its core, the sun burns at about 27 million degrees Fahrenheit. Without it, Earth could not possibly support life. It only makes sense that we would find some way to harness that energy and use it to produce electricity. It's the perfect energy source because the sun shines every day (unless of course it's cloudy). Solar power is becoming ever more popular as a growing number of people are installing solar panels at their homes and businesses. But solar power is more than just the big panels we see on buildings, it's also captured through a few other ways as well. 

Everyone every day experiences solar energy as long as long as the sun is hitting them. Solar energy is the sun's ray, or solar radiation that reach the Earth and can be converted into other forms of energy such as heat or electricity. It can be used to heat water, spaces, and fluids. It's converted into energy in two ways. The first is by using photovoltaic (PV devices) or "solar cells" and the second by solar/thermal electric power plants. There are 11 in California, 1 in Arizona and 1 in Nevada.

Solar thermal plants use the sun's rays to heat a fluid to an extremely high temperature and then it's circulated through pipes so it can transfer its heat to water to produce steam. Once steam is produced, it's converted into mechanical energy in a turbine and into electricity by a conventional generator coupled to the turbine. It works essentially the same as generation from fossil fuels except that instead of using steam produced from the combustion of fossil fuels, the steam is produced by the heat collected from sunlight. There are three main types of solar power systems: 1. Parabolic trough (most common type), 2. Solar dish, and 3. Solar Power Tower.

The parabolic trough is used in the largest solar power facility in the world in the Mojave Desert at Kramer Junction, California. It's operated since the 1980s and accounts for the majority of solar electricity produced by the electricity power sector today. A parabolic trough collector has a long parabolic-shaped reflector that focuses on the sun's rays on a receiver pipe located at the focus of the parabola. The collector tilts with the sun as the sun moves from east to west during the day to ensure that the sun is continuously focused on the receiver. 

Its parabolic shape allows the trough to focus the sun at 30 to 100 times its normal intensity on the receiver pipe that's located along the focal line of the trough achieving operating temperatures over 750 degrees Fahrenheit. The "solar field" has many parallel rows of solar parabolic trough collectors aligned on a north-south horizontal axis. A working (heat transfer) liquid is heated as it circulates through the receiver pipes and returns to a series of "heat exchangers" at a central location. The fluid then circulates through the pipes so it can transfer its heat to water to generate high-pressure superheated steam. The steam is then fed to a conventional steam turbine and generator to produce electricity. When the hot fluid passes through the heat exchangers, it cools down, and is then recirculated through the solar field to heat up again. This kind of plant is designed to operate at full power using solar energy alone, given sufficient amounts. However, all parabolic trough power plants can use fossil fuel combustion to compensate for the lack of solar energy, say on a cloudy day. 

A solar dish system uses concentrating solar collectors that track the sun, so they always point at it. Its concentration ratio is much higher than a solar trough's - typically over 2,000 with a working fluid temperature over 1380 degrees Fahrenheitmounted. The power-generating equipment used with a solar dish can be mounted at the focal point of the dish, making it well suited for remote operators. The engine in a solar dish system converts heat to mechanical power by compressing the working fluid when it is cold, heating the compressed working fluid, and then expanding the fluid through a turbine or with a piston to produce work. The engine is coupled to an electric generator to convert the mechanical power to electrical power. 

A solar power tower, or central receiver, generates electricity from sunlight by focusing concentrated solar energy to a tower-mounted heat exchanger. This system uses hundreds of thousands of flat, sun-tracking mirrors called heliostats to reflect and concentrate the sun's energy onto a central receiver tower. The energy can be concentrated as much as 1500 times that of the energy coming in from the sun. Energy losses from thermal-energy transport are minimized because solar energy is being directly transferred by reflection from the heliostats to a single receiver rather than being moved through a transfer medium to one central location, as with parabolic troughs. Compared to parabolic trough technology, these power towers are in the early stages of development.

The main benefits of solar energy systems is that they do not produce air pollutants or carbon dioxide. When solar panels are located on buildings they have minimal impact on the environment. While there are many benefits to solar energy, it also has its limitations. The amount of sunlight that arrives at the Earth's surface is not constant. It varies depending on the location, time of day, time of year and weather conditions. Because the sun doesn't deliver that much energy to any one place at any one time, a large surface area is required to collect the energy at a useful rate. 

As we move into the future, our energy consumption increases and our natural resources are dwindling. Solar energy will play a vital role in our quest to generate a sufficient amount of energy to fuel our electricity needs.  



image (CC) Packfill  

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