That Two-faced Sun!
17/03/2008
Over 100 years ago our good friend C.A. Parsons, of whom we wrote earlier, stated “The three basic sources of energy are the heat of the sun, tidal energy due to the moon and the heat of the earth”. All other energies are spin-offs from these three.
The energy reaching the earth from the sun is so vast it is beyond human understanding. This energy owes its existence to nuclear fusion within the sun. This activity produces radiation; some of it good some of it bad.
Fortunately, most of the radiation stays behind in the sun with mainly ‘good radiation’ coming our way. The greatest energy radiated from the sun is held within the sunshine we enjoy but it includes those harmful, penetrating, ultra- violet rays as well as those medically useful infra red rays. Any means by which we can capture this energy is useful, as long as it can be done economically.
An attempt was made in the 1970s when the construction of the worlds first large-scale solar power unit was completed in Europe. This consisted of 7,000 square metres of mirrors, sited around a 50metres high tower, which supported a large round water tank. The reflected heat of the sun on the water tank produced enough steam to drive a generator capable of supplying energy for 500 two bar electric fires. Now, thirty years later in Australia, there is a project only just completed, where the plant is capable of supplying enough energy for about 100,000 households1
Picture this amazing scene. A tall, round chimney, 1000 metres high (about 20 Nelson Columns on top of each other, or roughly three times the height of the Eiffel Tower), with a diameter of about 70metres. Attached around the base is a greenhouse type structure, with a sloping translucent roof.
This makes a sunshine collection area having a diameter of about 7 kilometres.(4.5 miles) Air inside this structure, becomes heated by the sun to about 35 degrees C higher than the outside air temperature. This hot air rises to the roof of the greenhouse and flows through 32 small turbines into the chimney. The chimney provides a good continuous up-draught which is achieved because of the colder air hanging about at its top.. Air, flowing through the turbines, supplies sufficient energy for them to drive electric generators. The electrical output is linked to the New South Wales Electric
System for the use of 100.000 households or industries. It is a sobering thought that by using a coal or oil-fired plant for these same
households/industries does result in about 900,000 tons of carbon pollutants being released into the atmosphere every year.
The floor of the greenhouse holds thermal storage material. This heats up during the day and gives up its heat after sundown, releasing its stored energy. Calculations have yet to be proved but it is hoped this stored heat will maintain the electricity during the hours of darkness.
The cost? The capital cost and maintenance of such a tower is very large, of course, but the sun freely gives the energy and the electricity produced is free of pollutants. No figures for comparison are available yet but there are plans to build four more towers across Australia.
We have already come a long way from shovelling coal into a furnace in order to produce electricity, amidst clouds of black polluting smoke. The next two decades should see the biggest change in electricity production in over a century, with the energy derived from the sun, vying with the wind, waves and geothermal for supremacy.
As early as 1975 satellite technology was suggested, by a CEGB research team. A satellite some 20 miles in orbit could accept the sun’s radiant energy. This energy could be converted within the satellite to microwave energy and beamed to earth. This microwave energy could be used as either heat or electrical energy. There is, no doubt, that this project is feasible but, at present, the capital cost would be enormous.
Where will nuclear power be in all this? This is an interesting subject for our later discussion …..Watch this space!