The solar steam turbine is another method of solar power generation that involves heating water using thermal energy derived from the sun. This method is currently being used in large-scale electricity plants.
However, smaller home steam turbines are on the horizon that will have the potential to do more than simply supply electrical power. You'll want to be watching for them when they come on the market! Read further to find out why.
Steam turbine generators have been in service for generations. Most often, water is heated by burning fossil fuels such as coal, oil, or natural gas. Once the water is heated and turns to steam, it can power a turbine, and the spinning turbine can be used to generate electricity.
Michael Faraday (1791-1867), the celebrated English physicist, made the discovery that electricity is generated when a wire coil is rotated near a strong magnet.
The effect formed the basis for numerous applications that use a generator to produce electrical power. It's the same electromagnetic principle that's at work in a spinning turbine.
Steam produced from solar heated water can power the blades of a turbine while producing much less pollution than methods of steam production dependent on fossil fuels.
The obstacle to overcome with a solar steam turbine is getting the water hot enough to vaporize.
We are all familiar with the typical solar power hot water heater that employs solar thermal panels mounted on a roof. The water is heated by thermal energy from the sun and then passed from the panels down a series of pipes into the home's hot water storage tanks.
The problem with such a basic solar energy capture system is there's only a fixed amount of bright sunlight available in any given location. Also, the total sunlight received will vary depending on cloud cover, moisture, airborne dust, and other factors. We simply cannot control the energy output of the sun.
We can, however, control "how" the sun's energy is used and applied by making a collector system that's more efficient. By using a parabolic mirror method consisting of "parabolic troughs," solar heating collectors can raise water temperatures to around 428°F (220°C), compared to the boiling temperature of water at 212°F (100°C).
A large parabolic solar dish or mirror that's shaped roughly like a section of a sphere can focus the rays of the sun to a point. The quality and shape of the mirror determine the sharpness of focus and the geometry.
Whereas a circular parabola focuses to a single point, a cylindrical parabola (trough) focuses to a line. The line shape serves to concentrate the thermal energy received into a smaller area making it possible to raise the water temperature much higher using the same energy.
For instance, the Solar Energy Generating Systems (SEGS) 150 MW solar power plant at Kramer Junction in California's Mojave Desert is one of nine similar power plants in the area. The system uses parabolic trough solar thermal technology to generate 90% of its electrical output from sunlight. The remaining 10% of its output is generated using natural gas when the sun's energy is insufficient to meet an increase in demand.
Sunlight reflecting off the half-pipe-shaped glass panels (94% reflective) is focussed along a tube filled with synthetic oil positioned above the panels, heating it to over 400°C (750°F). The transfer tube can be clearly seen in the closeup photo below. Heat is transferred from the oil to boil water and drive the Rankine cycle steam turbine to generate electricity.
Since a basic principle of the physics of heat is applied, the water temperature and pressure are high, making the conversion efficiency of the solar device correspondingly high.
Therefore, it is possible to make solar power generation devices with an efficiency rating as high as 40%. Typical home solar power panels range from approximately 10% to 15% efficiency in comparison.
The production of solar electricity has now become commonplace, and homeowners can enjoy the advantages of solar energy simply by installing photovoltaic (PV) solar panels on the roof or mounting them nearby on the ground to generate their own homemade electricity. But, specialized solar thermal panels that deliver concentrated electrical power could offer a powerful alternative.
Large-scale solar steam turbines are presently beyond the reach of the average homeowner; however, through advances in steam turbine design, a compact version of such a device might be possible for residential use. A home steam turbine powered by the sun's energy could theoretically supply heat, hot water, and electricity for the home.
Even now, some businesses are starting to experiment with steam turbines powered by the sun's energy, as the cost of fossil fuels continues to rise making the solar technology cost-efficient in the long-term. Watch for affordable home steam turbines to become a reality soon.
And soon, with increased government funding and a greater public awareness of the benefits of solar powered energy, compact turbine driven solar power plants could supply a sizable portion of a community's electrical needs.
Compact solar steam turbines are the future. Watch for them coming to the marketplace soon!
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Photo credits in order of appearance: Michael Faraday by Newington Butts (Public Domain),
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