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design for a sustainable future

< Energy efficiency in manufacturing
27.01.2010 20:47 Age: 6 yrs
Category: energy

Solar Collectors

Every year the sun delivers 15,000 times more energy to the earth than is consumed by the human population. Short to midterm a lot of the solar energy is locked up in land surface, plant material and bodies of water. Solar collectors allow us to copy the principles of nature and to generate hot water for our homes.   

Solar collectors transform solar radiation into heat and transfer the heat into water, solar fluid or air. The solar heat can be used for heating water for bathrooms, kitchens, swimming pools or heating the house.

At the heart of a solar collector is an absorber, which is normally  made of several narrow metal strips painted black. The black paint absorbs the short wave solar radiation, the absorber heats up and transmits the accumulated solar energy in the form of longwave heat rays to a fluid inside the absorber.

Basic absorbers are often used in outdoor swimming pools. The water is pumped through the absorber and water temperatures up to 20°C higher than outside temperatures can be achieved.

Glazed collectors achieve higher temperatures. In flat plate collectors absorber plates are connected to a pipe work system and fitted into a well insulated housing with a glass cover. A heat transfer medium such as a water-glycol mixture, to protect against frost, is pumped through the pipe work. This medium then gives off the heat to the water you can use in your bathroom, kitchen or central heating. Flat plate collectors can achieve temperatures of about 50°C and efficiencies of up to 60%.

Vacuum tube collectors offer improved efficiency and higher temperatures. They are made from evacuated glass tubes containing absorber strips. The vacuum provides ideal thermal separation and keeps convection heat losses at a minimum. Vacuum tube collectors can achieve temperatures of up to 70°C above the outside temperature and they are suitable to support your heating.

When using renewable energy systems, make sure that you introduce energy efficiency measures such as insulation first. This will prevent you from over sizing your systems and save on investment as well as running costs.          

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