Stiring-Cycle Engine Power By Solar Energy

Weird. a company called Stirling Energy Systems and their plans to build a huge power station based upon a Stirling solar array. And when I say huge, I mean 20,000 collectors spread over 4,500 acres. Unfathomably massive.

Each solar dish measures 37 feet across and is computer-controlled to track the sun. The thermal energy is focused on a collector which heats liquid hydrogen in a closed loop, just like the toy Stirling engine shown below. The engine's pistons drive an electric generator, and voila -- affordably electricity without pollution. They estimate a 1,000 MW array will be able to generate electricity at an incredibly affordable six cents per kWh.

Talk about a huge comeback for this classic technology.

A Depiction of a Dish Stirling On Sun

What is a Stirling Engine?

On September 27, 1816, Robert Stirling applied for a patent for his Economiser at the Chancery in Edinburgh, Scotland. By trade, Robert Stirling was actually a minister in the Church of Scotland and he continued to give services until he was eighty-six years old. But, in his spare time, he built heat engines in his home workshop. Lord Kelvin used one of the working models during some of his university classes.

In 1850 the simple and elegant dynamics of the engine were first explained by Professor McQuorne Rankine. Approximately one hundred years later, the term "Stirling engine" was coined by Rolf Meijer in order to describe all types of closed cycle regenerative gas engines.

Today, Stirling engines are used in some very specialized applications, like in submarines or auxiliary power generators, where quiet operation is important. Stirling engines are unique heat engines because their theoretical efficiency is nearly equal to their theoretical maximum efficiency, known as the Carnot Cycle efficiency. Stirling engines are powered by the expansion of a gas when heated, followed by the compression of the gas when cooled. The Stirling engine contains a fixed amount of gas which is transferred back and forth between a "cold" and and a "hot" end. The "displacer piston" moves the gas between the two ends and the "power piston " changes the internal volume as the gas expands and contracts.

The gasses used inside a Stirling engine never leave the engine. There are no exhaust valves that vent high-pressure gasses, as in a gasoline or diesel engine, and there are no explosions taking place. Because of this, Stirling engines are very quiet. The Stirling cycle uses an external heat source, which could be anything from gasoline to solar energy to the heat produced by decaying plants. No combustion takes place inside the cylinders of the engine.

The SES Solar Dish Stirling technology is well beyond the research and development stage, with more than 20 years of recorded operating history. The equipment is well characterized with over 25,000 hours of on-sun time. Since 1984, the Company's solar dish Stirling equipment has held the world's efficiency record for converting solar energy into grid-quality electricity. SES has teamed with the U.S. Department of Energy and Sun-Labs (NREL and Sandia National Laboratories) to endurance test and commercialize the SES solar Stirling system.