Accumulator hot water tanks

Put simply an accumulator tank is a large, well insulated, hot water tank, and forms the heart of your home heating and hot water system. An Accumulator tank (or heat store) accumulates (or stores) heat as the name suggests. Accumulators are used extensively in solar systems where the solar panels store heat in the large body of water, which then provides you with hot water during the times when the sun is not out.

You can also heat your house using heat stored in the accumulator tank. You might run radiators or perhaps underfloor heating from your tank: underfloor heating is ideal for use with accumulators because of the low loop temperatures.
The accumulator also lets you link up different heating systems, most notably it lets you link in a stove with a backboiler. A woodburning stove with a backboiler is the perfect companion for solar thermal panels because in summer when you wouldn't dream of lighting your stove the panels provide your hot water and you don't need the heating. In the winter the stove is lit and providing hot water and heating, and the solar panel is contributing a little by raising the temperature of the water at the bottom of the tank (to around 30-40 degrees or so in my tank ) - every little helps.

You can of course plug in just about anything else to the the accumulator tank: another stove, a conventional boiler for backup, electric heating elements (again as a backup source of heat), ground or airsource heat pumps, etc. The accumulator tank is the central point in your heating and hot water system - all your heat sources connect to it and all your heating is taken from it.

One of the big tricks of accumulator tanks is to improve and maintain good stratification (just follow the link in to find out what this is all about). Put very simply the idea is to keep the water at the top of the tank hot, and the water at the bottom of the tank cool, with as little mixing as possible between the two layers.

A wood stove will work best when burning quite hard - wood likes a good supply of air to the firebox. But burning your stove hard can mean your house getting too hot. The other advantage of using an accumulator tank in conjunction with a relatively large boiler stove is that it lets you batch burn: you fill up the stove and burn it relatively hard and it heats up (or charges) the accumulator tank. You now have hot water which you can use as needed. Of course this can also let you use a larger stove than you might have before which lets you use longer logs (less time spent processing and moving your wood) and lets you burn the stove less often.

Accumulator tanks are of course ideal for use with log gasifiyers - these are high output, semi-automatic log boilers which would normally live in an outbuilding. They have very large fireboxes and so you load and fire them up a lot less than a traditional boiler stove, which means more time putting your feet up.