Renewable Energy Technology Assessments - Kauai Island Utility ...

Kaua’i Island Utility Cooperative
Renewable Energy Technology Assessments
3.0 Renewable Energy Technology
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heat transfer fluid to steam, which is subsequently used to power a turbine. A thermal
storage tank can be used to store hot heat transfer fluid, providing thermal energy storage.
By using thermal storage or by combining the solar system with a fossil-fired system (a
hybrid solar/fossil system), a solar thermal plant can provide dispatchable electric power.
Solar thermal technologies may be combined with co-utilization of fossil fuels or energy
storage to provide a dependable dispatchable resource.
Solar chimneys do not generate power using a thermal heat cycle as the other
three technologies do. Instead, they generate and collect hot air in a large greenhouse.
Located in the center of the greenhouse is a tall chimney. As the air in the greenhouse is
heated by the sun, it rises and enters the chimney. The natural draft produces a wind
current, which rotates a collection of air turbines in the current. The first commercial
solar chimney is currently under development in Australia.
Applications
The larger solar thermal technologies (parabolic trough, central receiver and solar
chimney) are currently not economically competitive with other central station generation
options (such as natural gas combined cycle). Parabolic dish engine systems are small
and modular and can be placed at load sites, thereby directly offsetting retail electricity
purchases. However, these systems are still under development and have not been used
in commercial applications.
Figure 3-17. Parabolic Dish Receiver (Source: Stirling Energy Systems).
21 March 2005 3-64 Black & Veatch