Biomass boiler questions

[openspaceman]

5 ton of wood a month would be a hell of alot cheaper than want the parants are paying for gas at the moment.

If there is such a boiler than would burn anything it would be good, i can get an endless suply of arb waste wood chips.

 

I pay about 4p/kWhr(t) for gas and the boiler works close to 90% efficient.

 

5 tonne of wood at 40% mc wwb dumping flue gas at 160C will have a net calorific value of about 14MWhr(t). Boiler efficiency will be largely dependent on excess air which with wettish wood is likely to be high. I'd not expect much better than 70%.

 

On that basis useable heat into the building with wood at £20/tonne is ~1p/kWhr(t) and doing the same with gas would cost £435 if my maths is correct, that's more than my annual gas bill but I do burn a couple of tonne of wood too. The firm I do some work for sell woodchip delivered in at ~30quid/tonne but chipping costs over £10/tonne so I'm sure they would let it go at this.

 

The difficulty I see is a boiler that will take chogs from arb work, firstly they won't dry (hence my 40mc figure) secondly the gasifying boilers I dealt with wanted straight cord or cut firewood. There are issues with the gas evolution from slowly cooked large lumps of wood.

 

Wood chip stoker costs seem largely fixed in that they will work with 25-150kW boilers but the cost benefit is best at 150kW.

 

The only stoker I have seen built into a boiler that will also handle large logs doesn't seem to be the cleanest burning, I own one and wish I had the energy and money to modify it. The Kobs I worked on would not adapt at all and of course they would no longer be compliant in their type approval.

 

My old boss does still have a Veto head that could have a firebox and boiler built around it to accommodate large logs, it would be an interesting project.

[Wallnutt]

If anyone is on mains gas biomass really is a non starter cost wise, if you use oil or bottled gas it might stack up, but it is important to remember that these wood boilers require a lot of effort to keep filled with fuel, regular servicing is essential and the govt payments require a lot of hoops to jump through before they spill the money.

[Stereo]

We are looking at a small scale (20-30kw) gasifying boiler for our house which is not massive. Yes, there is work involved but for me that's a lifestyle choice anyway. Not sure I would make the same choice when I'm 70 though. I don't believe maintenence of the smaller setups to be much more than a gas combi.

 

I think you are correct if you make the assumption that you would be buying in seasoned wood. But, if you can produce your own fuel and it's just time (I class this as excersize myself so it saves on Gym fees) and you can qualify for some kind of RHI then I think it's a winner. Maybe only while the RHI runs but maybe in 20 years time PV will have come on and our appliances will be much more efficient?

[Marko]

If Fracking for gas doesn't take off then one of the 'easy' options may be tapering off the menu quickly. Around here Red diesel went through the 80p barrier for the first time last week so it is a quickly changing equation to wrestle with.

 

I think the ability to have a degree of energy self sufficiency will be enviable and wood heat will always be a way to convert your time into a worthwhile cash equivalent should you so wish. For me the exercise is a welcome bonus.

[Tom D]

So if i build an office next to my house and plumb it into my rayburn system can I get paid?

[Stereo]

I don't think a Rayburn qualifies for RHI payments. I know our Esse doesn't which is a similar device. I think you need a dedicated wood, chip or pellet boiler like and Eco Angus or similar.

[Robert_S]

So if i build an office next to my house and plumb it into my rayburn system can I get paid?

 

haha you beat me to it tom i was about to run a pipe to the garage and collect my money