Power from the sun
Sonal Patel - POWERMAG
- October 1, 2009
Another combination of technologies being used for renewable efficiency. Will it be a winner? --Ed.
Since Robert Stirling invented the Stirling engine
in 1816, it has been used in an array of specialized applications. That trend continues today. Its compatibility with clean energy sources is becoming apparent: It is an external combustion engine that can utilize almost any heat source, it encloses a fixed amount of a gaseous working fluid, and it doesn’t require any water — unlike a steam engine.
Power from the Sun
A good example is Phoenix-based Stirling Energy Systems’ (SES) newly designed solar power collection dishes that were unveiled at Sandia National Laboratories this July. Called SunCatchers, these dishes are the next-generation model of SES’s original system. With a high rate of production and cost reduction, they will be used in commercial-scale deployments starting in 2010.
The modular concentrated solar thermal (CSP) SunCatcher uses precision mirrors attached to a parabolic dish to focus the sun’s rays onto a receiver, or heat exchanger, which heats the engine’s working fluid, in this case hydrogen, and rejects heat at ambient conditions. As the gas heats and cools, the working fluid’s pressure rises and falls. This change in pressure drives the piston inside the engine, producing mechanical power, which in turn drives a generator and makes electricity.
The improved design stems from a collaboration between Sandia’s CSP team and SES. The new SunCatcher is about 5,000 pounds lighter than the original, is round instead of rectangular to allow for more efficient use of steel, has improved optics, and consists of 60% fewer engine parts (Figure 2). The revised design also has fewer mirrors — 40 instead of 80 — and the reflective mirrors are formed into a parabolic shape using stamped sheet metal similar to the hood of a car.... [Read More]