PV (photovoltaic) panels that produce electricity come to mind, or solar thermal systems that give bath-loads of hot water for anyone who has installed them.
Then there's concentrated solar power, of which there's a nice photo and description from wikipedia here. Basically these are huge rows of curved (parabolic) mirrors that reflect sunlight to a static tank of water or oil throughout the day. The heat generated creates steam to drive a turbine to make electricity.
I thought that was as far as we had gone with solar systems, until I came across this radically different concept they call the Sun-Pulse. Invented by the German physicist and inventor, Jurgen Kleinwachter, it has been built and tested in Tamera since 2008. So, here's how it works:
- solar energy in the form of sunlight is collected in pipes erected on a structure (in their case a greenhouse but it could be flat panels on a roof, or a series of parabolic mirrors beaming the light at a centralised tank, just like in the concentrated solar power system);
- vegetable oil is the selected medium to be heated because it has a boiling point far higher than water, so it can be heated to over 150 degrees C or higher (can't remember exactly, doesn't matter right now).
- the veg oil is allowed to circulate around a Stirling Engine. OK this in itself is a wonderful invention and concept all by itself - invented in 1813 by a Scotsman! Basically it's an engine that runs on the temperature difference between two points. There are two pistons that are driven up and down as gas is expanded when heat is applied to the "hot end" of the engine. Cold water is pumped to the cold end to maintain the temperature difference. The pistons move and drive a flywheel, which can be connected to a generator to make electricity, or a pump to move water, or a tank to hold compressed air, and so on. Again wikipedia has the basics here.
Now, the beauty of this system we visited in Tamera was its simplicity despite the complex design and mechanics. We were shown around by Douglas Baillie and Janos Valder, both seriously competent scientist-technicians in their own right. Douglas comes with a PHD in physics from Heriot Watt University in Scotland, which speaks for itself.
|Douglas beside the stirling engine. The insulated pipes carry the hot oil to and from the stirling engine. The|
circular fly wheel on the right is rotated as the engine runs.
|Nikita, right, researching for his essay...|
|Inside the greenhouse Douglas explains how the "Fresnel" mirrors direct sunlight to the copper|
pipes that carry the oil.
|Janos, standing beside the Sun-Pulse Water engine / pump - built with a few spare parts|
bits of motorbike, some old metal and sticky back reflective foil.