Break even

ed110220

Smiley_Dan wrote: »

I'm not sure that's entirely true. The grid has losses. Not sure how much though.

Nice work on your insulation.

Thanks! I've been doing the insulation DIY and at the same time as general renovations so it hasn't cost too much extra (not like, say, having external wall insulation done commercially). You can see a bit more about it here if you like: http://bisfhouse.com/internal-insulation-project-of-bisf-bedroom-by-ed/

Zeupater has confirmed what I had suspected about PV generation being used preferentially locally. Of course the carbon savings are only rough, as the amount of PV electricity generated will depend on your location, orientation, shading etc. And the carbon intensity of grid electricity is only an average and PV won't displace all forms of generation equally. It will mainly displace gas (moderately 'dirty'), perhaps some coal (very 'dirty'), but not generally nuclear or renewables ('clean'). Still, some rough calculations are useful I think.

Ed

MFW_ASAP

silverwhistle wrote: »

On the heating front I haven't yet had the central heating on this year due to the new wood-burner. All free wood, of course, although I admit I've bought some briquettes for emergencies and to avoid faff when aged parent visits.

Wood burners were being classed as being 'green' for a while because their fuel is renewable, if it is sourced from sustainable managed forests. They are also 'carbon neutral', however there are real concerns about the amount of pollution they emit and the damage they cause to air quality, especially when it affects asthma sufferers.

Smiley_Dan

And don't get us started on "kiln dried" logs!

zeupater

MFW_ASAP wrote: »

Wood burners were being classed as being 'green' for a while because their fuel is renewable, if it is sourced from sustainable managed forests. They are also 'carbon neutral', however there are real concerns about the amount of pollution they emit and the damage they cause to air quality, especially when it affects asthma sufferers ....

Hi

Agree, our fuel is all hardwood grown on estate managed ancient woodland a couple of miles away, sourced from a sawmill built a couple of centuries ago - delivered direct and tipped onto the drive ... that just about covers the 'renewable part' ...

Regarding the particulates .... that's really a yes, no & maybe position ... Does combustion result in particulates?, yes ... Are all particulates the same ?, no ... What types of particulates have the most effect on health ?, from what I've read over the years it probably ones which are water insoluble ... How do particulate levels compare between various combustion sources (hydrocarbon etc), what are the particles and what is the relative long-term effect on health?

Now, considering the stoves themselves - would all stoves create the same particles when burning the same type of fuel ... well the answer to this is yes if the owner hasn't got a clue about efficient burning, but when you get to understand the process - no. Whether you've got an inefficient open fire or the most efficient stove possible, if you don't burn at a high temperature you'll get smoke & if you burn wood which isn't fully seasoned it'll have too high a moisture content and you'll get even more smoke, not only that. you'll get relatively little heat ...

Smoke is really a mix of unburned fuel in particulate form and steam, mixed further with a number of combustion by-product gasses - mainly carbon-monoxide and carbon-dioxide. The less efficient the burn, the more particles and the higher the mix of CO to CO2 (at high temperatures toxic carbon-monoxide itself burns with a blue flame, creating carbon-dioxide) ...

Enclosing the combustion in a chamber allows better control of the combustion products and oxygen from the air, as well as containing the heat produced and restricting the exhaust product flow rate. Wood combustion itself is a process of the surface of a solid boiling away as a mixture of volatiles and particles, if the temperature is high enough they'll ignite (change chemical composition & release energy, normally through oxidation), if not they'll go straight up the chimney, a complete waste of the money spent on fuel .... this really explains why a burner is more efficient than a fire and why high combustion temperatures are necessary ...

So, is there a difference in the way that different burners operate ? ... well yes. Externally most would see little difference, however there is a huge range in efficiencies which depend on the design of the combustion process. Looking at the figure in the referenced post you'll see 'Uncertified' & 'EPC certified' stoves (US standard). Uncertified stoves are pretty basic, probably low end (cheap) and definitely low efficiency. Certified stoves are tested to a standard which effectively allows them to be classified as 'clean burn' .. this is usually achieved by introducing pre-heated air into the combustion chamber so as not to cool the combustion process ...

Burning at really high temperatures creates little smoke, and therefore few particulates ... at the moment (sunny ... ) the only evidence that our fire is working is a heat haze distortion visible when looking at the shadow of the chimney - no smoke or steam at all, and it's been like that from about 20-30minutes after it was lit this morning ... Every so often we probably annoy the neighbours (both the two legged ones next door and the four legged ones which actually do neigh in the field behind!) with a cloud of steamy smoke for a few minutes when first lighting the fire, but apart from that there's even very little 'sweet fire aroma' outside ...

HTH
Z

silverwhistle

I took some readings today as I'm expecting a bill any day and wanted an idea of what it'd be. I had new meters put in 16 months ago and in that time I've imported 1448 kwh of electricity and 5500 kwh (approx. based on current conversion rate) of gas. My gas bill for the 12 months ending in March should be a lot less as the wood burner went in in August, so I'd hope a fair bit less than 4000 for the year.

The only problem with sourcing free wood is keeping ahead of the game, so this weekend's contribution for next winter is the prunings from my neighbours _massive_ Bramley. Saves it going to landfill.. I was offered a useful bit a few days ago but realised it was Elder: so that will be going for chipping!