Given the overall efficiency is only 92% which is poor for a modern boiler it would be fair to assume that it's the generating part which is pulling it down in the absence of any actual figures.
But with your record on quoting efficiency it's not surprising you think it is over 90% efficient when producing electricity.
Maxie, what does vbg mean? Is this your new secret name?
You must eff off as you are a total idiotic Jocko plantpot.
Forgetting Drivel's understanding of things, where MicroCHP units deliver is in reducing CO2, given that grid-sourced electricity is assumed to have a CO2/kW figure of just over twice that for mains gas (0.422 v. 0.194). The test cases we were sent when I was writing SAP software assumed a heat:power ratio of 2:1, which may or may not realistic, but assuming this and a heat load of 20kW
Gas boiler 92%: 20 x 0.194 x 100/92 = 4.22kg CO2
CHP 90% 2:1 20 x 100/60 = 33.33kW input 33.33 x 0.194 x = 6.47kg CO2 for heating electricity generated = 10kW CO2 saving from displayed = 10 x 0.422 = 4.22 Net CO2 = 6.47 - 4.22 = 2.25 - 47% reduction
The docs I have read (a while back now) did emphasise that unlike modulating gas boiler systems, Micro CHP is very sensitive to correct sizing as you need the load to keep it running for long periods.
Note it's 2330 Melbourne time so my arithmetic is not guaranteed!
In message , Doctor Drivel writes
If I told youi I'd have to kill you
... and that would be uk.d-i-y's main source of entertainment gone
You must eff off as you are a total idiotic Jocko plantpot.
Which is much superior to yours.
These units are 1.1kW max, just using waste heat.
That's what I imagine to be a big failing. Considering a house I've done detailed heatloss calculations for, 3 bedroom, semi or end-terrace, built 1909 (9" brick walls), only insulation added since built was double glazing (before April 2002) and 4" loft insulation, i.e. probably below average insulation for UK housing stock. Calculated heat loss at -3C is 11kW. (Based on subsequent experience running the system, I suspect this was an over-estimate. At a more typical temperature of 5C, heat loss is barely 7kW, which is what the boiler will modulate down to. There's nowhere near enough wasted energy to run a waste energy generator at this level. The only time the boiler runs at 25kW (where it could run a stirling enging) is for about a minute when it's first switched if the radiators are stone cold.
My God!!!! You are a secret agent Maxie. Fantastic!!!!
..James Bond, oh yes you are ..Maxie drives a big flash car ..He has guns inside the light ..He shoots the Ruskies to our delight
..A suave man to no avail ..shaken not stired he has his brown ale
They were meant to be combis, where they run at full belt when the taps are on.
So how long do you keep your hot water running? (For the purpose of this question, you can discount any burst pipework;-)
Like I said, useless.
About a minute? Look again.
It is "seasonal" performance that matters. In summer they will still be producing electricity (combi or not) and pumping that into the grid, which will be used by local consumers with less line losses and hence higher efficiencies.
First thing in the morning when the combis are at full belt in heating before modulating down, and also full belt in DHW, is also the time when there is also high electricity demand. The peak usgage of both coincides. microCHP will level off the peaks of electricity demand. microCHP makes sense in new housing estates. If millions are installed then they will make a significant impact. It is clear not so many new power stations would be built, and probably eliminate the nuclear option.
You need to think it through.
The example you give is precisely where it makes no sense. If you size it for DHW it will be grossly oversized for heating; if you size it for space heating you then need something else for DHW.
A (non-micro) CHP plant possibly makes sense where you have an extended need for heat and power, e.g. a municipal swimming pool.
It really makes you wonder about dribbles claims to be a heating engineer...
My guess is maintenance and repair costs would well exceed any saving in electricity.
Read and understand what I wrote.
Eff off as you a total plantpot.
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