Best of both worlds - combining wood stoves and solar panels for reliable heat
We often face dilemmas and trade-offs in choosing the right green energy solution for our homes. Aesthetically a log burning stove can be one of the most pleasing centre-pieces of a home, but is all that chopping and stoking going to happen 365 days a year, particularly in the Summer? Solar thermal panels on the other hand are great for those clear bright days but will not provide all your heating needs alone. Using oil or gas is a useful back-up of course, but we really want to break our dependence on high carbon and expensive fossil fuels as much as we can.
One approach is to combine the best aspects of all these heating systems is to feed their heat into a single store of energy that can supply our needs as and when is required.
To do this requires a special hot water cylinder at the heart of the system - conventional cylinders are not appropriate. A special thermal store cylinder is a large tank, usually around 1,000l capacity (280l is an average domestic hot water tank). These large tanks allow a good storage of energy with very hot water accumulating at the top more efficiently than smaller ones. The cylinders are vented which allows for pressure release should a lively stove make the water too hot in the system.
The thermal store has a number of hollow coils inside it which allow hot water to pass through transferring the heat to the water in the tank. These coils can be plumbed into multiple heating sources such as a log burning stove, biomass boiler, solar thermal panel, heat pump, gas or oil boiler. Thermal stores can even come supplied with an internal electric immersion heater as a further back-up option.
The thermal cylinder store usually sits above the stove in the house and as close as is practical given the need for the storage space required.
Once the heat is stored in the tank, there are options for using it in different ways too. A conventional radiator circuit can be piped into the system as can underfloor heating if required. Water from the tank is pumped around these circuits returning to be reheated then pumped around again.
For your hot taps and mixer showers, cold water from the mains is heated for use as required by passing through a heat exchanger at the top of the tank, giving you hot water on demand.
For the stove, most older properties have a fireplace available that can be revealed if blocked up, with chimneys re-lined if necessary prior to installation. A back boiler on a stove feeding the heat up to the store will of course take that heat away from the room, so care has to be taken to select a stove of the right output to heat both the area it sits in and to keep your store topped up.
Log burning stoves are more efficient when burning hot and with a thermal store in place you can save a lot of that heat for when you need it most, rather than opening the windows! While there are no government incentives for log stoves, adding solar thermal panels could also attract the government's Renewable Heat Incentive (RHI) payments and will of course give you free heat energy on those sunny days.
With thanks to GEN user - rensus for providing information for this article.