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| General Electric's hybrid power plant |
ScienceDaily, November 3, 2011
Hybrid cars,
powered by a mixture of gas and electricity, have become a practical way to
"go green" on the roads. Now researchers at Tel Aviv University are
applying the term "hybrid" to power plants as well.
Most power plants,
explains Prof. Avi Kribus of TAU's School of Mechanical Engineering and its
innovative new Renewable Energy Center, create power using fuel. And solar
thermal power plants -- which use high temperatures and pressure generated by
sunlight to produce turbine movement -- are currently the industry's
environmentally-friendly alternative. But it's an expensive option, especially
when it comes to equipment made from expensive metals and the solar
high-accuracy concentrator technology used to harvest solar energy.
Now, a new
technology Prof. Kribus has developed combines the use of conventional fuel
with the lower pressures and temperatures of steam produced by solar power,
allowing plants to be hybrid, replacing 25 to 50 percent of their fuel use with
green energy. His method, which will be reported in a future issue of the Solar
Energy Journal, presents a potentially
cost-effective and realistic way to integrate solar technology into today's
power plants.
Taking down the
temperature for savings
In a solar thermal
power plant, sunlight is harvested to create hot high-pressure steam,
approximately 400 to 500 degrees centigrade. This solar-produced steam is then
used to rotate the turbines that generate electricity.
Though the
environmental benefits over traditional power plants are undeniable, Prof.
Kribus cautions that it is somewhat unrealistic economically for the current
industry. "It's complex solar technology," he explains. The materials
alone, which include pipes made from expensive metals designed to handle high
pressures and temperatures, as well as fields of large mirrors needed to
harvest and concentrate enough light, make the venture too costly to be widely
implemented.
Instead, with his
graduate student Maya Livshits, Prof. Kribus is developing an alternative
technology, called a steam-injection gas turbine. "We combine a gas
turbine, which works on hot air and not steam, and inject the solar-produced
steam into the process," he explains. "We still need to burn fuel to
heat the air, but we add steam from low-temperature solar energy, approximately
200 degrees centigrade." This hybrid cycle is not only highly efficient in
terms of energy production, but the lowered pressure and heat requirements
allow the solar part of the technology to use more cost-effective materials,
such as common metals and low-cost solar collectors.
A bridge to
green energy
The hybrid fuel and
solar power system may not be entirely green, says Prof. Kribus, but it does
offer a more realistic option for the short and medium term. Electricity from
solar thermal power plants currently costs twice as much as electricity from
traditional power plants, he notes. If this doesn't change, the technology may
never be widely adopted. The researchers hope that a hybrid plant will have a
comparable cost to a fuel-based power plant, making the option of replacing a
large fraction of fuel with solar energy competitive and viable.
The
researchers are starting a collaboration with a university in India to develop
this method in more detail, and are looking for corporate partnerships that are
willing to put hybrid technology into use. It's a stepping stone that will help
introduce solar energy into the industry in an accessible and affordable way,
Prof. Kribus says.
Story Source:
The above story is reprinted from materials provided by American Friends of Tel Aviv University.Note: Materials may be edited for content and length. For further information, please contact the source cited above.
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