One of the biggest uses of electricity, gas and oil is the heating of water in the home, and in offices, schools and hospitals etc. Solar water heating is a very simple and efficient way to grab energy from the sun and use it. Solar water heaters concentrate diffused solar radiation into thermal energy.
A solar water system consists of a solar collector and a storage tank. The solar colector is usually a flat rectangular box (1 sqm per person in the household) mounted on the roof so that it faces South (for northern hemisphere dwellers). The box has a transparent cover made of strong glass or plastic through which the sun’s rays enter. Inside the solar collector a thin copper pipe snakes up and down and left and right across the box. Behind the copper pipe is reflective foil and then insulation so that the suns energy does not escape. Water or anti-freeze is pumped through the copper pipe and is heated by the sun’s energy. The hot liquid is then pumped through a coil of pipe in a standard hot water storage tank/boiler. When cold water enters the tank it is pre-heated by the coil and so less energy is required to heat up the tank of water to a usable temperature by the boiler. Most systems work well even when the ambient temperature is well below zero and can save 20% off your water heating bill even in the depths of winter.
A typical system, for example 4sqm of collectors for a household will lead to savings of two-thirds on previous water heating bills and is environmentally friendly.
Another type of system which is becoming more common thanks to its increased efficiency is an Evacuated Tube Solar Water Heater. This is made up of an array of evacuated double glass-walled tubes which each have a space in the centre containing a copper heat tube. Around 93% of solar energy hitting the tube is absorbed and used to heat water; the remaining 7% is reflected. Thanks to this high efficiency prices for these systems start from just 30 pence per Watt of energy required.
Pictured above is a DIY Solar Water Heater. Find out how to Make Your Own Solar Water Heater here.