I was going to call this article "solar heating in the home" but then I realized that I would be perpetuating the myth that heating is a primary use for solar energy and so I changed my mind. The reason solar energy is not hugely useful for heating the home is common sense really. In the winter, when you need your heating on, the sun is lower in the sky and there are fewer daylight hours. In the other seasons when solar energy would be more effective you do not need it. At best, solar heating can support your central heating a little in colder climates whilst in places such as Australia and California it can be worthwhile, but then it's not needed so often.
A number of technologies have been developed to make use of solar radiation. Some of these make direct use of solar energy for lighting and heating etc., while others produce electricity. They are:
- Solar thermal energy collection systems which generate electricity through mirrors and a system of tubes filled with fluid.
Solar thermal collectors which are used to produce heat.
Photovoltaic panels which generate electricity direct from sunlight. However, they generate DC current, which if you want to use it in the home, has to be converted to AC This would require a very big surface area to meet the needs of just one home which is why solar panels are rarely used for domestic Heating. However, in a sunny climate, you can produce enough power to run a 100W light bulb from one square meter of solar panel.
Solar hot water panels which are often used in the home to heat water.
Solar Panel Efficiency
Although solar panels are used all year round they are only efficient when they receive direct sunshine. They produce very little power in cloudy conditions or in the shade. However, it is the light that produces electricity. Heat actually interferees with electricity production so solar panels used in very hot climates are less efficient than those used in sunny but cold climates. When the panel's temperature is above 50 degree centigrade its efficiency will decrease. Also, at different times of the day, as the sun angle to the panel varies, the amount of energy produced is different. Usually it is better if the panel is inclined but on cloudy days horizontal mounted panels are more efficient. Most energy is generated when the panel is pointed directly towards the sun.
The use of solar power has fallen in and out of favor since the 1970's depending on the potential savings when compared with other energy costs. The equipment needed nowdays is 90% cheaper than it was thirty years ago and homes with solar roof tiles can often generate more electricity than is needed at certain times of day. Depending where you are in the world this execess energy can sometimes be sold to local electricity companies.
In Japan and the USA, billions has been spent on developing Photovoltaic systems and Germany has now joined in the research. As is often the case with renewable energy systems, the initial costs of setting up solar energy for the home is quite expensive. However, savings on electricity bills in the long term should make up for this and as time passes, the costs are falling making it more widespread.