Wood pellet boilers

[Bayliss]

I'm taking full advantage of the experts on this forum and this question concerns the whys and wherefors of the new fangled wood pellet boilers. Presently our oil boiler seems in reasonable working order but its in an terrible location, the dining room :roll: why the previous owner had it installed there!! So in an year or two I want to replace and relocate, the boiler is for hot water and heating to our little cottage. Any views/considerations on the new boilers please.

 

[worms]

I am told it is wise to check your source of pellets carefully (bagged versus blown, delivered versus collect) as this can have a major bearing on the economics.

Since you are thinking a couple of years off, keep your eye on the renewable heat incentive http://www.decc.gov.uk/en/content/c...olicy/renewable_heat/incentive/incentive.aspx as the government may pay you for the privilege of running the system (there may also be something on this in tomorrow's budget).

 

[Flyfisher]

I briefly looked into wood-pellet boilers a couple of years ago and concluded that they were really intended for very large/light-industrial/agricultural premises. I agree with worms about being careful to look into pellet sources/packaging and also the optimum storage volume. Wood is a fairly low-density energy source and the systems I read about seemed to recommend quite large storage hoppers to accomodate bulk deliveries - hence the light-industrial/agricultural 'feel' the such systems. Plus, all the enquiry emails I sent did not receive any replies - my conclusion was that they were not interested in domestic systems.

But there's a lot going on in this area and things may have changed in a couple of years, so I might be out of date.

The dining room is certainly an odd place to choose to install an oil-boiler!

 

[AMc]

I investigated wood pellets - there are a couple of issues
1 - The installed cost is substantially higher than a conventional oil boiler. This is true for almost all 'alternative' systems.
2 - You need high quality pellets and the price of these varies with the cost of oil as a substantial part of their cost is transportation. So as oil dwindles and prices rise so does your cost.
3 - You need a large space for storage. I was told that to be ecologically and economically viable you want a single delivery of fuel per year (which makes sense given 2). For my house that would have meant a 2m cubed space with a pair of corkscrew lines to feed from the hopper to the boiler. Alternatively you can load manually, but that is less attractive to most of us and you still need a lot of dry storage.

You should also look at log boilers which burn logs not pellets at high temperatures to heat a thermal store (big water tank) then the thermal store drives the system. Again they need manual loading and they require quality wood but logs are generally easier to come by.

You can also use wood burners with back boilers to do similar things and there are a number of other alternatives to oil boilers.

If you are near mains gas then this remains the most cost effective and ecologically viable solution for now but if you're rural then that's out of the question.

We went with an Air Source Heat Pump in the end which has been a bit painful and I continue to find ways in which it is less environmentally friendly than I expected.
In retrospect I would have spent more to get a bore hole ground source heat pump, but that boat has sailed.

The most cost effective thing you can do is take measures to reduce your heating demand with draftproofing and insulation while taking account of vapour permeability (a.k.a. breathability).

You can get a lot more information from http://www.greenbuildingforum.co.uk. It costs £5 to join now, but I believe you can still browse for nothing. If you're thinking of spending £1000's on a new heating system then the £5 is well worth it for the impartial advice.

Start by finding out the capacity of your current boiler so you can get some prices on alternatives with a similar power output.

 

[skier-hughes]

I also looked into this and gave up. The boiler would be large, it needs it's own flue... lucky for me I could get it up a chimney from the fuel store room, but when I wanted a log boiler they got expensive and very expensive to have auto feed and then the logs needed to be pretty uniform in size, so I couldn't find a way of having some form of automation whilst using my own logs and scrap wood.

I've just 2 weeks ago had a wood burner with boiler installed in the lounge, replacing an old existing wood burner with no boiler. This is coupled to a 900 litre water buffer tank and this gives us heating in the morning without having to worry if the fire will stay alight all night.
50 solar tubes gives us srping summer and autumn hot water and also on some of the bright days we've had already has contributed to the heating.

Our oil fired rayburn which used to supply hot water and heating (didn't wasn't powerful enough) is still connected up as well, so we can enjoy the wonderful rayburn cooking experience.

The benefit of wood burner in the house is that we don't have to go outside in the rain, snow, freezing cold to stoke it, and as we work from home we are around and about to keep chucking a log or two on.

If you want more info like sizings, makes etc let me know.

Graham

 

[Penners]

We went with an Air Source Heat Pump...... I continue to find ways in which it is less environmentally friendly than I expected.

AMc - could you expand on that statement a bit, please? I'd be interested to know why you feel this about the device.

 

[AMc]

We went with an Air Source Heat Pump...... I continue to find ways in which it is less environmentally friendly than I expected.

AMc - could you expand on that statement a bit, please? I'd be interested to know why you feel this about the device.

The initial installation was too small because the heat loss calculations weren't accurate and no one noted that the boiler being replaced was rated at at 19kW-35kW so the 16kW ASHP couldn't be enough for a larger house even with much better insulation.

The 16kW unit is rated at +5C and actually only puts out 12kW at 0C so when demand was highest it was totally out of it's depth. Running at higher flow temperatures than expected and using the direct electric backups to try and deal with the undersizing lowered the efficiency significantly and my power bill is frightening. The lady on the phone the other day told me not to worry until I confirmed she was a decimal place out in comparing her estimate to my actual reading

Subsequently we've fitted a second 16kW unit which has tamed that excess, but I've just discovered that there is a background load of 24kWh a day in leaving both pumps on and idle - that's more than my total power consumption per day for effectively nothing. As one ASHP is designed to run my hot water AND it controls the immersion in my tank, I can't just turn it off - but turning it on and off requires a 6/7 hour wait between turning on the power and it being ready to run a bit like when you move a fridge which isn't going to be easy to automate.

Finally when the horror of all this was going on I did the sums and discovered at 50p a litre for oil vs. 14.1p per unit of electricity (peak) the ASHP would need to run at an efficiency of 3:1 before it could compete on cost with oil - I reckon my single one managed about 2-2.5:1 this winter. My electricity costs are tied to oil prices (even though I use 100% renewable electricity from Good Energy). If I were able to run it on Economy 7 with a buffer tank I'd be better off, but again I was told this wasn't necessary so I didn't fit one and now I can neither afford one nor have the space to fit one - which would have been possible at the planning stage.

A ground source heat pump would have been more expensive, but the higher running costs of the ASHP this winter have already eroded that cost difference and unless the dual system is more effective next winter it may have been a false economy even with the massive cost of boreholes. I'm now technically "carbon neutral" which is a nice place to be, but my bills are so big it's not quite as comfortable as it should be

I would recommend anyone looking into ASHP also considers GSHP despite the difference in initial cost. Insist you talk to an existing customer with the same system. Ask long hard questions about heat output at +5C, +2C, 0C, -2C and -5C and a binding statement about power consumption outside heating periods as this seems like an inexcusable design flaw to me.

In short I believe that ASHP is an entirely viable technology but there are better and worse designed systems and I didn't ask enough questions before I agreed to the system I fitted. In a smaller house or one with the ability to be more effectively insulated then I suspect many of these problems would be less of an issue.

 

[JohnB]

Something that concerns me with all these systems is that they need mains electricity to run, unless you have your own big wind turbine. There's the possibility of power cuts in the foreseeable future, and no electricity means no heating. A simple, but efficient, wood stove with gravity fed radiators, or at least a low powered pump than could be run from a battery, might be a safer idea. In view of the uncertainty surrounding future energy supplies, I would look at having several heat sources, rather than putting all my eggs in one basket.

When I was in the renewable energy industry a few years ago, we installed several log boilers, that were relatively cheap and simple. We had a bad, and expensive, experience with a certain make of pellet boilers. When I left we were looking at a high quality pellet system that I was impressed with, but it's complex and unusable without mains electricity. I also worry about long term maintenance costs, and obtaining parts in the future, as they are currently not mass market products. You can't fix them with a hammer and a bit of string in an emergency.

Several years ago, pellet supply was a problem, and as far as I know, it's not much better now. After we removed one of the pellet boilers we had trouble with from the customers house, it was installed in my house, where it was ok, but not brilliant. In the end it got thrown out when it wouldn't work with a new load of pellets. It later turned out that it was a faulty batch of pellets, although how some little cylinders of wood fuel can be "faulty" to the extent that a biomass boiler can't handle them I never really understood.

For a modern house, or an old one of no great historical interest, I'd say insulate, insulate and insulate some more. Then use several simple, but efficient, technologies for heating, so you're not dependent on one form of energy. I appreciate it's not so easy in a house of historical interest though.

 

[Penners]

I'm now technically "carbon neutral" which is a nice place to be, but my bills are so big it's not quite as comfortable as it should be

Many thanks for that comprehensive explanation.

I have to say that "...not quite as comfortable..." sounds a dramatic understatement. Your saga is really rather a horror story. In particular I was pretty shocked to hear that there's:

a background load of 24kWh a day in leaving both pumps on and idle

On the basis of your experience, however nice a place carbon neutrality may be, I can't see many people wanting to go there via your route. A great shame.

 

[Flyfisher]

Thanks for that AMc; it's good to hear first-hand experiences, even if it's not always good news. Your economics were interesting. I'd already concluded that a heat pump couldn't compete with gas but I thought they might have the edge over oil - but I'm out of date with oil prices since we got rid of our old Rayburn, although I know they've gone down since the last time we bought some.

I guess the biggest problem with all heat pumps is that they run on electricity, which is a secondary energy source. Thus, while they may be 300% efficient in terms of the power they consume, a large part of that efficiency is lost in generating the electricity in the first place. Take into account all the technology and energy involved with manufacturing power stations and heat pumps and it might be more efficient to just burn the coal itself in an a multi-fuel stove.

I'm now technically "carbon neutral" which is a nice place to be, but my bills are so big it's not quite as comfortable as it should be

I'm afraid I disagree with the carbon neutral point. It can't be so simple as just signing up with a renewable electricity supplier. Imagine if the entire country decided to go "carbon neutral" in that way. I'm not arguing that renewable suppliers are not a good thing, but the reality is that the electricity you draw from the grid is mainly generated from coal and nuclear power.

 

[AMc]

Something that concerns me with all these systems is that they need mains electricity to run, unless you have your own big wind turbine.

Even with a big wind turbine you'd need a battery backup and to be off grid. All feed in connections must cut out in the event of a grid failure to prevent maintenance engineers getting electrocuted making repairs.

Our old oil boiler had electric ignition and a pump, as did the gas boiler in the house before. It's really no greater a problem to run a heat pump on mains. We get regular power cuts but never long enough to be an issue, not as long as the 5 days we waited without heat when we ran out of oil last year! I have 2 woodburning stoves for backup.

a background load of 24kWh a day in leaving both pumps on and idle

Not all ASHP have this issue. IMHO its a flaw in the design of this particular model which uses an electric heater to prevent the compressor lubricant being compromised by liquid refrigerant. Other systems drain the compressor so it can be powered off properly.
It's a serious problem with the current accreditation schemes that power usage generating heat is measured but standby costs are ignored. IMHO the systems should be assessed on both.

I'm now technically "carbon neutral" which is a nice place to be, but my bills are so big it's not quite as comfortable as it should be

I'm afraid I disagree with the carbon neutral point. It can't be so simple as just signing up with a renewable electricity supplier.

I knew someone would, hence why I said "technically" not "actually" . Some 'green' tariffs include fossil fuels in their allowable mix, last time I looked http://www.goodenergy.co.uk were the only ones promising to match consumed watt for renewable watt. Every watt I use is replaced with a renewable one bought on the long term electricity market. The power bought at any one instant will be produced by whoever is providing the lowest prices to the grid. That's is why you see the ridiculous sight of wind turbines standing idle on windy days because the spot price doesn't cover the cost of starting them up (you have to power the turbine to get the blades moving).

I pay a premium for renewable energy which drives the market to invest. If the demand outstrips the supply then the price will go up, improving the economic return on investment in renewable production and stimulating more capacity. I can't see any more direct way to influence the energy mix.

Imagine if the entire country decided to go "carbon neutral" in that way.

At the moment very few people are prepared to pay the extra pence a day that this option costs so I don't see this as a serious problem. If everybody did move to 100% renewable tariffs then in the short term prices would sky rocket, the industry would stop accepting new customers onto those tariffs until more capacity was installed & there would be a gold rush of investment in renewable energy. I don't have any problem with that.

On the basis of your experience, however nice a place carbon neutrality may be, I can't see many people wanting to go there via your route. A great shame.

My experience is not typical. My house is very large and not very efficient in modern terms. I haven't insulated the walls in the main house (as I didn't want to destroy the remaining original features. We rebuilt a Victorian vinery as living space, even with the best glazing I could get this room is not very efficient.
If when we looked at this house I knew what I know now I wouldn't have bought it full stop.
If I'd known what I know now about heating and power consumption I would have kept the vinery separated from the main house and heated it solely with the woodburner when we wanted to use it but there is no point in worrying about what could have been.

In the end I was sold a solution and I should have bought one - which was my own inexperience and no one else's fault.

[Edited to change misattributed quote]

 

[Flyfisher]

Fair point about being "technically" carbon neutral; you've obviously thought a lot about the whole matter. I mentioned it because I know two people who really do believe they are carbon neutral simply by buying their electricity from a 'renewable-only' supplier. I agree it's a way of influencing the market but, from the figures I've seen, British Gas invest far more money into renewables than these far smaller 'renewable-only' suppliers. This is not really surprising as there is clearly no long-term business future in fossil fuels so all such companies are busily reinventing themselves as 'energy companies' and they know they have to invest heavily to secure their long-term future. Meanwhile, economics dictates that fossil fuels are still the cheapest energy sources. No doubt that will gradually change.

That last quote was Penners' by the way, although I agree with the sentiment.

 

[Bayliss]

Thank you for all the information, seems matters have an fair way to go before I commit to an new boiler.

 

[AMc]

Flyfisher - Sorry for putting words in your mouth, I've edited the post.
My thinking is an electric heating system can be greened but an oil one can't. My big glass folly meant I had to use a heat pump or wood to meet Building Regs and I was talked out of the wood by cost of installation, storage and the price of pellets.

The energy companies are investing in renewables partly because it makes good sense in dwindling supplies of fossil fuels and partly because they're forced to by regulation. I take your point about BG spending more money, but they have proportionately more customers and more money too. My decision was to make a commitment, though it was easier to do when my electric bill was 16kWh a day than 160kWh in January!

 

[Penners]

a large part of that efficiency is lost in generating the electricity in the first place

Absolutely right. And the widely-heralded Nissan Leaf, billed as the world's first mass-market electric car, actually runs on coal.

However, I do take AMc's point that electricity can be greened, whereas oil can't. So, if renewable generation is pursued relentlessly, then any electrically-powered device will become steadily more environmentally friendly.

 

[Flyfisher]

Yes, I also agree about electricity. I can't imagine us ever being able to do without it, whatever energy sources become available in the future.

The electric car thing is interesting and I wonder how they will impact the existing electricity supply models. I've already read things about charging points being "intelligent" and connected to the internet so that the charging demand can be controlled and, in the event of shortages, even being switched off completely in order to avoid power cuts. But I can't see it being popular not knowing the cost of an overnight charge or even finding that there was no overnight charging because cold weather increased domestic heating demands and the car remains 'flat' the following day. More positively, I've also read that such vehicles might be able to be used to store electricity, releasing it back to the grid in times of very high demand. They would act as a huge, distributed battery. There are certainly some interesting ideas out there so who knows how things will evolve.

 

[philpjuk100]

A bit on the east mids telly news tonight.It had a bit on the east midlands airport which hopes to be carbon neutral by 2012.They have had 27 100 metre boreholes drilled for heat pump at a cost of six million £,they have planted 26 hectares of willow on the airport to supply 280 tonnes of pellets a year for a pellet boiler,they have built four 31.5 metre wind turbines(I suppose if the wind drops they can just back a jet up against them!) and have rainwater loos and bio methane airport buses(I do not think they have anything to do with the loos!)There must be money to be made from running airports!.I suppose they will soon have the aircraft running on used chip oil! phil.

 

[FamilyWiggs]

A bit on the east mids telly news tonight.It had a bit on the east midlands airport which hopes to be carbon neutral by 2012.

Presumably this doesn't include the aviation-fuel burning jet planes!

 

[JohnB]

A bit on the east mids telly news tonight.It had a bit on the east midlands airport which hopes to be carbon neutral by 2012.

If this was the type of aircraft that used it that might be possible :evil:

 

[Flyfisher]

I wonder how many years they'll need to break even on that little investment - it's expensive going green!

The willow figures were interesting though; 26 hectares for 280 tons of wood pellets per year. I make that 4.2 tons per acre per year, which seems like an awful lot. Perhaps I should plant an acre of willow and revisit a scheme I read about where you join a syndicate that owns a harvesting/pelleting machine and they come round and crop your plantation every four years and share the pellets among other syndicate members to even out the four-year rotation. Still need lots of storage space though. Hmm.

As for there being money in airports, I guess that must be true although I do wonder about the economics of air travel sometimes. We have to go to Austria later this year for a week and assumed driving would be the cheapest option for three of us: about 900 miles, 15 hours of driving, possibly an overnight stay on the way (I'm not as young as I used to be!). At about 450 miles per tank of fuel, we'd need a minimum of four tankfuls of diesel, say £300. Pretty good for three people, I thought, although I didn't relish the actual driving.

Then, out of curiosity, I checked for flights - £145 for all of us, return, and less than 2 hours flying. Add a couple hours at the airport and that's about a quarter of the time and half the price compared to driving. Crazy or what?