Well finally the government have announced the levels of support for their plan to encourage non gas using households to adopt sustainable heating systems – the Renewable Heat Initiative. It may be of interest to woodland owners in two ways: firstly you have a very cheap source of sustainable fuel, and the Government is keen to encourage and subsidise that use. We have two clients who have been stimulated to manage their woods for that reason. But even if you are not in the market for a new heating system, the RHI is stimulating demand for woodfuel and increasing the value of your trees as a standing crop, making future management more profitable. The RHI is complicated, so start off with a look at the Energy Saving Trust website. It will take a while to work out how much grant support you are likely to get.
If you are thinking about changing your heating system, it is a great time to consider low carbon options. For an average system you are looking at receiving RHI payments of around £7500 over a ten year period plus capital grants for the initial installation. You will have to fill in lots of forms and questionnaires once it is all working. All of the equipment must be approved by the Micro Generation Certification Scheme (MCS) and the installer must also be approved in order to qualify, so bear in mind that all this accreditation has a cost.
If you own a woodland you should start by working out the sustainable volume of timber that you would be able to harvest each year. (A single hectare (2.4 acres) of Oak coppice can produce between 4 and 8 cubic metres of timber per year if regularly managed). If you are relying on wood for all your heating needs you may need 8 or 9 cubic metres each year to heat a larger property, so make sure you have enough. You will also need sufficient dry storage for this volume of logs, and to be able to harvest sufficient timber two years before you will need to burn it. If you are having trouble with any of these preliminaries, you may need to modify your plans. Wood pellet boilers are an increasingly popular alternative, as they are fully automated and you can buy in pellets whenever you choose.
You could build your renewable heating system around a wood burning stove with a back boiler to heat water. Very few of these log boiler stoves are certified by MCS but the Broseley eVolution 26 has recently qualified (see above) and therefore can be used as part of an RHI scheme. This stove claims to be 78% efficient and has a thermostat so it does not overheat the room, automatically diverting heat to the back boiler instead.
For a more automated system you could consider a Gasification Boiler which burns logs in a controlled firebox at up to 90% efficiency with all the heat going to the hot water system. Gasification boilers have a large firebox which you burn rapidly to maximise efficiency and reduce emissions and ash. Not so pretty so it would need to go in a back room with good access to the log store.
You will need a large thermal store or storage tank to store all the hot water from the Gasification Boiler. Thermal Storage tanks are large pressurised vessels that can carry on supplying hot water to your house and the heating system, long after the fire in your gasification boiler has burnt out. The thermal storage tank is at the heart of your heating system. This is where energy can be stored from your stove, your solar thermal panel or ground heat source, all contributing to your renewable heating system in different ways. Getting this right is very important indeed and should be central to your investment decision. (Thermal stores are BIG. With a minimum 300 litres, plus 10” insulation, it might not fit into your bathroom. It may even be too heavy to go upstairs.)
With a large attenuation tank you may only need to fire up the gasification boiler every 2 or 3 days. The plumbing is fairly complex but if you are having it fitted with a new boiler you will only be paying 5% VAT.
You could consider making your own chips to fuel a wood chip boiler, providing that you have somewhere to store them and can move them around. Wood chip boilers tend to be larger than wood pellet boilers (25 KW and upwards) so may be too large for many houses, but will give you a fully automated system. Chips need to be consistent in size and moisture content, so you would need to have a regular supply of suitable material coming from your woodland. Softwood thinnings are ideal, or any broadleaf coppice wood would be fine. The key is make sure the wood is dry before you chip it. You can hire in a chipper for the day, with or without an operative.
It may be far more cost effective to upgrade your existing wood burning stove as new designs are much more efficient (many now run at over 70% efficiency) which will mean much more heat for much less wood. If you fit thermostatic controls on your existing radiators, you can reduce your oil or electricity consumption significantly. The wood burner will act as a space heater, so your heating system will only work in the rooms where the radiated heat cannot get to.
Whatever you do, it is certainly true that insulating and draught-proofing your house should always come first. The RHI is now linked to the Governments “Green Deal” so you may need to undertake an audit of your energy use before you start.