kWh/tonne output

It all depends on the boiler, the moisture and where the meter is in the system.

im about 2300 for straw and 2400 for big logs but that’s after boiler inefficiencies and for one, after it’s come out of the tank.

these are batch boilers though, chip will no doubt be more efficient?

its interesting seeing the sales spec for some boilers quoting 3500 for logs, i wonder what is actually achievable in realith
 

mountfarm

Member
It all depends on the boiler, the moisture and where the meter is in the system.

im about 2300 for straw and 2400 for big logs but that’s after boiler inefficiencies and for one, after it’s come out of the tank.

these are batch boilers though, chip will no doubt be more efficient?

its interesting seeing the sales spec for some boilers quoting 3500 for logs, i wonder what is actually achievable in realith

I’m getting some conflicting view on this. Any info from online searches such as this link


Seem to suggest wheat straw around 4000kwh/t and wood chips 4800kwh/t yet in the real world it’s more like 2200kwh/t and 3000kwh/t retrospectively from what I’m being told. We’re looking to install a boiler and these differences alter fuel costs significantly.
 
Others will be along to tell me my figures are a bit low but if you are doing costings on a new boiler I’d work off my output figures then you may get a nice surprise.

anything which starts with a 4 is I suspect utter rubbish!
 

rollestonpark

Member
Arable Farmer
Location
Burton on trent
Here is a page with lots of fuels from Reka Boilers:
But of course these assume, that you get all the heat from the fuel.
There will be loses directly to the environment from the sides of the boiler etc, up the flue, heat loss in pipework etc.
So it's going to depend on how clean/efficient the boiler is, and the loses in the pipework etc.
Maybe 20/25% loss ? Not sure really.
Also wetness of the fuel will play a big part in loses.
 

farmerm

Member
Location
Shropshire
I’m getting some conflicting view on this. Any info from online searches such as this link


Seem to suggest wheat straw around 4000kwh/t and wood chips 4800kwh/t yet in the real world it’s more like 2200kwh/t and 3000kwh/t retrospectively from what I’m being told. We’re looking to install a boiler and these differences alter fuel costs significantly.
If you measure wheat straw in a bomb calorimeter it would have a calorific value of 14.4GJ which would equate to 4000kwt... however your biomass boiler is not a zero (or close to zero) loss combustion chamber. If your burner is 75% efficient 1000kwt of your 4000kwt escapes up the chimney and though heat radiating out of the boiler. Whatever efficiency you are told your boiler is, it probably is not, such numbers will be best efficiency, a boiler finely tuned for the test and before soot and clinker build up. I would certainly err towards Doining it for the Kids numbers, being pleasantly surprised is more better on the soul than bitter disappointment.
 
Average over the last 5 years is 3430, quite surprised, I thought it would be more. Mind that the boiler works it out from the feed auger, so not a real per tonne as the density will vary quite a bit.

Our figures for heat delivered to buildings via district heating pipe were reliably 75% of heat generated. (changed the metering recently)
 
Average over the last 5 years is 3430, quite surprised, I thought it would be more. Mind that the boiler works it out from the feed auger, so not a real per tonne as the density will vary quite a bit.

Our figures for heat delivered to buildings via district heating pipe were reliably 75% of heat generated. (changed the metering recently)

is this for wood or straw?

what does your RHI heat meter say though, not the boiler?

im Guessing your boiler is automated, what make please?

3430 sounds an awful lot!
 
is this for wood or straw?

what does your RHI heat meter say though, not the boiler?

im Guessing your boiler is automated, what make please?

3430 sounds an awful lot!
Sorry for the vague post, we have a 90kW Eta chip boiler. Under our previous metering arrangement, the two meters inside the serviced properties, added together were 75% of the production meter in the boilerhouse .
3.4 kW Hours per kg, 3430 per tonne.
This is calculated from the boiler kg burnt figure and the boiler production meter.The boiler works off the feed screw, so is really calculating a volume which of course depends on the density of the chips. Generally I work off 3 cu m per tonne and the whole lot seems to tally on my spreadsheet over the year. We chip on the farm, so no weigh bridge involved.
 
Interesting. It seems high to me but I’ve little experience in chip boilers.

what I’d know is our DHS pumps water over 200m underground including a pop up in to a garage and the temp doesn’t drop by one degree from one end to the other.

interested to hear other thoughts.
 
Interesting. It seems high to me but I’ve little experience in chip boilers.

what I’d know is our DHS pumps water over 200m underground including a pop up in to a garage and the temp doesn’t drop by one degree from one end to the other.

interested to hear other thoughts.

Our system shuts the flow right down by monitoring the return temperature, when that drops, the valve opens and flow picks up, so we do see a drop, but its part of the plan.

The Flow temp is also regulated (can't remember the current set value) but the hot water is blended with return water to protect the pipe from degrading

The figures I was given for. heat loss when contemplating the whole idea was 25 watts per metre. That translated into what we understand is £6 per metre per year. I was horrified at first but even the electricity board have losses, its just a question of whether its a significant proportion of the total transmission.
 

555

Member
Location
Cambridge
With straw we are seeing an average of around 3300kw/T as measured at the heatmeter. This is across 50 boilers all of 1mw and above. They have a continuous demand. Average moisture is 19% , I would prefer this to be lower at around the 15-16% mark. We are seeing upto 15% variances of kw per T across the country , with East Anglia producing the most kwT at 3600kw and down to 3000 kwT further north. This is also in line with moisture content of the bale.
 

mountfarm

Member
With straw we are seeing an average of around 3300kw/T as measured at the heatmeter. This is across 50 boilers all of 1mw and above. They have a continuous demand. Average moisture is 19% , I would prefer this to be lower at around the 15-16% mark. We are seeing upto 15% variances of kw per T across the country , with East Anglia producing the most kwT at 3600kw and down to 3000 kwT further north. This is also in line with moisture content of the bale.

That’s interesting thank you. So basically the higher the moisture content the less kWh/t received?
 

555

Member
Location
Cambridge
Correct , In theory , not accounting for boiler efficiency etc a Tonne of wheat straw at 15% gives 3900kw , at 20% it gives 3600 , at 25% 3400kw. So simply put for every 5% about 10% loss in Kw. Or every Tonne of straw at 15% has around 150lts if water.
 

SFI - What % were you taking out of production?

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Red Tractor drops launch of green farming scheme amid anger from farmers

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As reported in Independent


quote: “Red Tractor has confirmed it is dropping plans to launch its green farming assurance standard in April“

read the TFF thread here: https://thefarmingforum.co.uk/index.php?threads/gfc-was-to-go-ahead-now-not-going-ahead.405234/
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