This is a standard system that is fitted in the majority of homes. It consists of a
hot water cylinder that is fed by a header tank, usually in the loft, and is
vented to the same tank. The water pressure that is achieved is equal to the
head of water provided by the header tank. The cylinder usually has two
means of being heated, a heat transfer coil linked to the house central heating
boiler and/or an emersion coil. In these systems it is usually preferable to
replace the cylinder with a new cylinder that has two heat transfer coils, one
for the solar system and one for the boiler (an emersion coil can also be fitted
as a back-up). A closed solar circuit is created that pumps a mix of water and
glycol through the panels, gaining heat as it does so, and then through the
heat transfer coil in the cylinder. The solar heat transfer coil is usually placed at
the base of the cylinder, where the water is coolest, as this offers the greatest
efficiency for the solar system. A dedicated controller constantly monitors the
temperatures through the system and determines whether at any time there is
sufficient energy gain possible to justify switching on the pump.

 

This type of system is becoming increasingly popular in the UK as it is a simple means to obtain mains pressure hot water without the use of a pressurised cylinder. It actually reverses the normal process whereby the boiler heats the water that is to be sent through the taps for our use, this water being stored
in the cylinder until required. In this system heat from the boiler and/or solar circuits is stored in a vented cylinder, called a thermal store, and is transferred to the water destined for the taps via a heat exchanging coil at the top of the thermal store. The water from the cold mains passes through this heat
exchanger before entering the hot water tap circuit in the house; the water in the thermal store never enters the taps. This system is very flexible and is capable of being integrated with low temperature heating systems such as underfloor heating.

 

 

 

 

Many combi boilers are incompatible with solar heating and special consideration has to be given to these situations. The problem arises where the boiler cannot accept pre-heated water. If pre-heated water can be
accepted then the system can be simply designed by introducing a thermal store to capture the solar energy and pre-heating the water before it reaches the combi boiler by passing it through a heat exchanger in the thermal store.

If this is not possible then a common solution is as indicated in this diagram. This involves a thermal store to capture the solar energy, through which water passes to gain heat. This hot water then reaches a divert valve that is controlled by the solar controller. If the water is hot enough for use in the
house then the valve directs the water straight into the taps, bypassing the combi boiler. If the water is not enough then the valve closes forcing the water to be drawn from the combi boiler.

 

 

If you have a swimming pool then most solar systems for the house can be integrated with a solar system for the swimming pool. Heating swimming pools can represent a massive energy cost and solar heating is a perfect solution,providing maximum energy when you need it most and extending the operating period of the
pool. Importantly the incremental cost of incorporating the house hot water into the system is minimal giving rise to significant cost savings.

Furthermore, the enlarged solar panel system provides greatly enhanced winter performance for the house when the pool is not being used. The system in most cases is relatively straightforward. The pool is heated by passing the pool water, via the filtration circuit, through a heat exchanger linked to the solar circuit. The control panel can be programmed to provided maximum hot water to the house and switch the circuit to the pool when this has been satisfied.