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Introduction of solar hot water
Posted at 1:56 AM on 4/13/2008
Hot water is required for many purposes and the sun can be used effectively, efficiently and economically to provide this heat. The warming effect of solar radiation is obvious and it is well known that a container of cold water, left exposed to the sun will be raised in temperature. Solar water heating systems are designed to make convenient use of this phenomenon.
Solar water heaters generally employ a solar collector and a storage tank. The solar water heating collector is by far the most widespread solar energy conversion device and there are several millions in use around the world. There are many simple designs of collectors and water heating systems. Construction and manufacture is easily achievable in most developing countries.
The energy required to raise the temperature of a substance is a physical property known as the specific heat of the particular substance. The specific heat of water is 4.2J/g/ oC, i.e. 4.2 joules of energy are required to raise the temperature of one gram of water by one degree centigrade. Using larger and more familiar units:
Energy required (kJ) = 4.2 x volume (litres) x temperature rise (oC)
Thus, in order to consider energy sources for water heating, the parameters that must be known are the volume of water required in a given time period (hour, day), the temperature of the 'cold' water, and the required delivery temperature. Hot water may be used for a variety of purposes, but as an example, domestic use is considerable. Here usage varies widely; in industrialised countries an average of around 50 litres per person per day is normal, in developing countries the more wealthy inhabitants may use this amount or more, while the poor may not use hot water at all.
Tips£ºsolar water heater solar lighting solar panel
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