What Happened when Solar Met the Reverend Stirling

We often spend so much time trying to develop new technologies that we forget about the old ones. Sometimes it pays to take a look back and have a good look what we’ve done and where we’ve come from. After all, a little reflection may well provide the answer we’ve been looking for.

Deep in the Kalahari Desert, the Swedish have been doing just that, creating a new energy system that could revolutionise the way we look at solar power. It looks like a James Bond set but the twin disks erected under the heat of the sun could be set to revolutionise the solar power industry if the makers can find a way to produce the technology commercially.

The groundwork for this latest innovation was set way back in the early 19th Century by a scientist and clergyman who invented an alternative to the then popular steam engine.

The Reverend Robert Stirling

Robert Stirling was born in Perthshire in 1790 and became a minister after studying divinity at the University of Edinburgh. Like many people of the time, he was also interested in science and liked to invent things. Stirling patented what he called the heat economiser which was a process for improving fuel efficiency in industrial processes. Whilst it didn’t catch on at the time, this idea has recently been resurrected by an innovative research and development team who are keen to evolve our use of the sun’s potential away from simple solar panels.

The Stirling engine is essentially a closed-cycle regenerative heat engine that uses a piston to create electricity and was notable at the time because it was much more efficient than the popular steam engine. The only problem was that the high heats needed and the materials available at the time meant that the Stirling engine wasn’t a viable proposition until recently when it was used in submarine technology in the late 1990s. The man, Gunnar Larsson, who helped develop that technology brought it to the world of renewable energy in 2008 when Ripasso was initially formed.

Ripasso and the Stirling Engine

Swedish company Ripasso think they are close to making a commercial version of their new energy producing technology. It combines the heat of the sun with a version of the Stirling engine to produce electricity. In the Kalahari Desert there are two 100 square metre light reflecting dishes that concentrate the sun’s light into a single hot point that is used to drive a zero emission Stirling engine. The constant heating and cooling of the gas inside the engine moves a piston and creates the electricity that could, potentially, provide power to thousands of homes.

Despite trouble with finding the financing for the 4 year project, things are well on course for the company who are hoping to revolutionise the way we use the sun to produce energy. Whilst current photovoltaic cells have a maximum efficiency of 23% in most solar farms and home installations, the Ripasso invention looks to be converting 34% of the sun’s energy into electricity.

There have been recent studies by a UK company that show that a single Ripasso disk can generate around 75 megawatts annually which is enough to power 24 homes. Most researchers have admitted that the technology looks strong but the problem is, as always, how you convert it for commercial use. A 100 metre square disk is not a small thing and installation will come at significant initial costs, far in excess of solar panel technology we have at the moment which is coming down in price.

Whether it will ever by suitable on a smaller scale for micro generation, expect to see more of this new technology in the future though as further developments come on line.

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