Biomass domestic heating

We don't have mains gas & are also considering options for a new heating system Bruce.

The BM boilers that only burn pellets appear good,
but consider fuel security.
If you have a pellet manufacturer nearby you should be OK.
But if you have a problem with a local supplier & have to get pellets delivered from afar (say the local source goes bust) the biomass boiler can cost as much, or even more to run then oil!

Multi-fuel biomass boilers can be good if you've a cheap/plentiful source of wood.
But I understand they aren't as efficient as the pellets.
Ground source heat pumps work well, but to retro' fit in a house is very expensive.
For best results the heating needs to be underfloor, or big radiators.
For these you also need land to bury the pipes, or pay the extra for a bore hole.

Air source heat pumps are an interesting option IMHO.
Not expensive to buy or complex to fit, but can be quite noisy.
The other drawback is you need a way to move the warm air around your home,
or leave all the internal doors open.

We still (after two years of cogitating) haven't decided what to do.

Bruce

I have knowledge of controlling Biomass boilers in a commercial environment.

The following points may also be applicable to domestic use.

Biomass boilers are used in conjunction with a gas or oil boiler. Say 60%/40% output. Biomass boilers are most efficient when working at maximum output. They are used during times of high heat demand along with the gas/oil boiler if required. During low demand the gas boiler alone is used.

Domestic hot water is generated by other means. Gas water heater or electric.

Check if storing the fuel in the cellar is a fire hazard. Speak to your insurance company.


Ground source heat pumps and solar heating are classed as low grade heating. Ideal for UFH, but additional heat generators are required during high demand periods. Ground source heat pumps are used for generating Domestic hot water, but also require additional heat generators.

Bruce,

What is your power supply like?
If your area is prone to power cuts, then a heat pump only solution could leave you freezing.
Although IO use a pellet fire at home, a very small generator/inverter can keep this running should power be cut.

Sorry to add to your confusion, but was an important consideration for my own house.
Pete

Thanks all.

I'm looking into the storage and supply issues, lots of local log suppliers but storing and filling with logs is less convenient than bagged pellets-although may be cheaper.

Domestic systems can be 'standalone' not requiring a supplementary gas/oil boiler but do need a hot water system for summer. I get the impression small scale installations area a fairly new and developing area.

Solar, wind and ground source heat pumps are not options for the main house, we are looking at air source heat pumps for the 'extension' which is actually a seperate building and could therefore have such a system 'designed-in'.

We have open fires and a log burner in the house too, although our electricity supply is fairly reliable we won't freeze if it goes off!

Bruce

Hi Bruce
I spoke to our boiler man recently about this[ he installs oil condensing boilers and does it as a hobby as he is a semi-retired engineer: a real enthusiast]He has looked into this and explained the potential pitfalls with wood pellet systems: firstly getting the right size; not many producers in UK and they don't adhere to a single standard, which means you may only be able to rely on a limited number of suppliers. Secondly, you need a large storage area and it needs to be kept dry [I am sure you are aware of this with your experience of wood burning stoves: well seasoned wood is vastly more efficient when it comes to heat output]. The carbon footprint argument looks a little shaky with wood chip when one considers the transport costs [ie more delivery trips for equivalent output with oil]. And wood chip burners are not cheap either. Have you thought about an oil condenser?: not ideal, but very efficient when compared with gas and other forms of heating.
Simon

quote:

Originally posted by Simon Douglass:
Hi Bruce
I spoke to our boiler man recently about this[ he installs oil condensing boilers................... Have you thought about an oil condenser?: not ideal, but very efficient when compared with gas and other forms of heating.
Simon

Thanks. That is the default option at the moment. We do have space for an oil storage tank.

I've also discovered that pellets from some companies apparently have a distinct smell. That would be an issue as the cellar is not really a cellar but a multi-purpose room with a bedroom next door!

(We live in eccentric house)

Bruce

bruce

I dont know how much space you have but with regards the oil tank , there are more regulations surrounding the tank than the actual boiler , i would get an "oftec registered installer " qualified in tank installations to give you siting advice .

Air Exchange and Ground Source heat pumps can provide full domestic heating and hot water, but they are best used in combination with underfloor heating, as they are most efficient when they raise the temperature of the underfloor heating water to about 30/35 deg C rather than the 55/60 deg C that is used in domestic water radiators.

Also, depending on the heating requirements of your house (ie how many kW), you may well require a 3 phase 400v supply to run the pump, as they have high start up loads. This can be expensive as the network provider will have to install a transformer and separate supply. Provided you have a sufficient length of in-ground heat collector pipes, you can run them all year. Typically ( depending on soil type and wetness-damp aids heat conduction) you will probably need to install 2 or 3 300m sets of pipes. if you do not have that amount of land , bore holes for vertical pipes are the alternative, but again they are generally more expensive.

Air Exchange pumps are slightly less efficient than GSHP but require no land or pipes and can even extract heat at temperatures as low as minus 15 deg C. They can be installed internally, provided you have a basement with an air intake, but you should check the SPL levels at 1m , 5m and greater.

Government grants for installing heat pumps are a joke, currently £1200 for a GSHP.

Heat pumps also mean you are reliant on electricity from the grid (albeit using much less than other heating methods) for your heating and there are concerns for electricity grid supply in winters in the next few years, as old coal fired power stations and nuclear come off-stream and limited new generating capacity is added.

Nonetheless, we are going ahead with a 17kW GSHP, supplemented by ( we hope) by 5 KWP of solar PV.

Modern wood burning stoves are cheap, very efficient and have low Co2 emissions, provided you have access to a plentiful supply of logs.
They can be a good supplement to cover the eventuality of an extended power outage.

Good luck with your choice.