Solar Heating System
How Does Solar Heating Work?
Unlike Solar PV Panels, solar heating systems do not convert sunlight to electricity, they collect radiation from the sun to be used for the purposes of heating.
There are many types of solar heating systems available but the solar collectors come in two main types. Flat Plate, where water passes through a plate, is heated and returned to the cylinder. The other is Evacuated Tubes that have a copper conductor on the inside filled with fluid. As it heats up, the fluid rises to the top of the tube, transferring heat to the water in the cylinder.
Types of Solar Heating Systems
Solar Heating Systems available include Direct or Open Loop that circulates potable water through the collectors. (Potable water is water that is safe for humans to consume or use). Unfortunately, Direct systems are not suitable for use in extreme weather conditions or hard water areas, as they can be prone to freeze or overheat and collect scale easier than some of the other versions available. Indirect or Closed Loop systems separate the potable water from the Heat Transfer Fluid (HTF). The HTF heats up in the panels, is transferred to the heat exchanger where heat is then transferred to the potable water.
There are Passive systems which circulate water or HTF via convection or pipes driven by heat. In contrast, Active systems use one or more pumps to circulate water and heating fluids around the system.
An Integrated Collector Storage (ICS) system or Batch Heater uses a tank that doubles as storage and a solar collector. Similar to an ICS is a Convection Heat Storage (CHS) system, except the storage tank and collector are separate and driven by convection.
In Active Indirect systems, pressurised anti-freeze or glycol is mixed with water to prevent damage from freezing. One type of Indirect system is called Drainback. It almost always uses pure water as its HTF which is driven by pump through the collector. If the pump is switched off, the HTF drains back into a special reservoir, preventing damage from freezing or overheating.
Domestic boilers, even the most efficient condensing models are rarely suitable for use with solar panels, as they are designed to take cold mains pressured water and not hot or warm water at lower pressures like that produced by solar heating systems. So it’s nearly always the case that they do have to be replaced. Accumulator hot water tanks are used in solar systems where the panels store heat in the water.
What Conditions Does Solar Heating
The UK climate being what it is people often wonder if solar heating will work. Even sunlight diffused by cloud produces enough energy to provide about 60% of the hot water requirements of the average UK home. This means that even in winter water heating costs can be reduced by around 20%. So there is quite enough sunlight in the UK to make solar heating a very viable choice.
Apart from providing a large percentage of hot water for the home, solar heating systems can run radiators to heat space. In fact, they are especially suited for use in the increasingly popular under- floor heating systems.
There are a number of grants available to help with the cost of installing domestic solar heating systems. There are local grants like the Solar for London programme providing discounts on solar heating components. Providing the installation is done by an approved installer these grants can be worth up to £1500. Your system installer should be able to inform you of any grants available in your local area.
On a national level, the government’s Low Carbon Buildings programme could cover up to £400 of the cost of a new domestic solar heating system and in Scotland grants of 30% of the system price up to £4,000 is available. To qualify you do have to demonstrate that you have taken necessary measures to ensure you aren’t wasting energy anywhere else in the home. You must already have loft and cavity wall insulation in place and be using low energy bulbs and room thermostat/ timers to control your central heating use.