Solar Water Heating

Typical solar roof water heating systems consist of 6 to 12m²of SOLAR ROOFING >. A 6m²solar slate system will cost around £1300-£1900 plus installation (the final price depending on what cylinder is specified). The output from this will be around 3000kWh/year, saving £175 of electricity, or £140 LPG, or £125 of oil, or £85 of gas at today's prices.

The size of the solar system should be related to the building size and the number of occupants. Properly sized domestic systems generally require 1.5 - 2m² of solar roof per person, and water storage of around 25 - 50 litres per m² of roof.

Systems will integrate with all commonly used heating systems, and cylinders may be vented or pressurised to suit. Combi boilers can be used as long as they are able to take solar preheated water – contact the manufacturer about this.

System Designs
A number of different system designs can be employed, depending on the existing plumbing and what boilers or stoves are installed in the building. Two common system designs are shown below:

Systems using a new solar hot water cylinder:

System boiler backup: A new larger twin coil cylinder is fitted to replace the existing single coil one, with the solar collector heating the whole cylinder from the bottom, and the boiler topping up the temperature in the upper section when required.
Combination boiler backup: A solar pre-heat cylinder is installed, feeding a solar compatible combination boiler or instantaneous water heater, which tops up the water temperature when required.
Systems which retain the existing hot water cylinder:
Retro-fit heat exchanger coil: A heat exchanger is retrofitted into the existing hot water cylinder by removing the immersion heater. No change to existing plumbing is required.
Second cylinder: A new cylinder is installed, with the solar roof indirectly heating new cylinder and another heat source indirectly heating existing cylinder. The cold feed is to the solar preheat cylinder, and hot water is taken from the second cylinder. This system needs either a three way valve to select water from the solar cylinder or the existing cylinder, controlled by the solar pump station, or a pump to transfer heat between the cylinders.