Combined Heat and Power

[Dave]

CHP (eg whispergen) looks like an attractive idea, has anyone done any research on it? Is it a technology that's ready for "prime time"?

Dave S

[Ian Stirling]

Me, I'd like an option to run as a generator in a power cut (obviously supplying a seperate circuit). If I had one, I'd probably make it do that, but it would be nice to have it as a stated option.

Have problems with power cuts lasting from 1-24 hours, which this would fix, at the cost of probably having to run the hot tap to dump waste heat. It'd certainly be cheaper to run compared to a petrol generator.

[IMM]

Do a Google on MicroGen. Similar product, but better, but not out just yet.

[Ed Sirett]

When this was discussed last time, IIRC, the general concensus was that if you needed to generate your own electricity (perhaps because of remoteness from the mains or poor reliability of supply) then this might be the way forward if you are starting from scratch, otherwise it's really too unproven.

[Ian Stirling]

The thing is designed normally to run more or less constantly. It's inherently going to be more reliable than a cheap generator especially one not rigorously maintained.

Combining a boiler upgrade (non-condensing - condensing) with an upgrade that allows (with the addition of a UPS) a 1Kw backup generator that is quiet, needs no seperate fuel storage, starts easily, provides heat when electricity fails, and does not generate noxious fumes and has cheap fuel could be a good plus.

[Ian Stirling]

Why do you think it's better?

[OldScrawn]

Because microgen is going for 50 Hz directly? No inverter losses.

[IMM]

I looked at the both of them a while back. MicroGen is really a boiler with a Stirling engines/generator (hermetically sealed like a fridge compressor). The Whispergen is really for boats. The Whispergen does not produce enough power to be useful enough. OK in a superinsulated house with full solar collectors providing the heating and most of DHW storing energy in a large water thermal store and you extract waste heat from the Whispergen too, with ultra low energy appliances and lighting, maybe then the Whispergen would suit a normal house.

The Microgen is primarily suited to flatten the peaks of grid power usage as it feeds back into the grid power not being used.

[Nick Finnigan]

Yes, but the thing is designed to run more or less constantly.

In the summer, even 3kW of heat is more than is needed. In winter, a continuous 6-8 kW could be enough, but many people would not like the idea of continuous running whilst there is nobody in the house, nor of running out of hot water.

[Tom]

Years ago, Fiat made a domestic CHP unit (20Kw?)based on one of their car engines.I think it was in the 1970s, they probably discontinued it as there wasn't much interest then. Tom

[IMM]

Based on the 127 engine running on natural gas. A few were fitted in Energy Park in Milton Keynes.

[Ian Stirling]

Why isn't the Whispergen exactly the same thing?

I could find no power output figures for the Whispergen.

[Ian Stirling]

Which can be well under 10%, with little problems. It's not hard to imagine that the constraint of having to go for

50Hz may cause more inefficiency.

[IMM]

No. Microgen is and looks like a condensing boiler, (with a difference)

Look at:

did have figures on their web site. Also another web site had them, the company that was marketing it in the UK.

[Ian Stirling]

I may not have been clear.

This is not to produce power all the time, that would be at best marginally profitable, if at all.

It's to run one low-power circuit that would be connected to the input of a moderately large UPS which runs an emergency circuit (low-power lights, boiler, computers (most of which will automatically shutdown), fridges, ...)

Over the past 5 years, I'd guess power has been off for a total of 120 hours, in perhaps 20 seperate cuts, not to mention a hundred or so

5-60 second ones.

I have doubts that it'll improve dramatically.

[sylva]

Yes this was the Totem, produced for Calor. IIRC there was only one at the exhibition houses at Milton Keynes and it supplied 4 houses.

Longevity was an issue with this engine.

The whispergen with its "conventional" stirling should be good for

20,000 hours (just over 2 years constant running), who knows for the free piston "bouncing" unit in the microgen. In ac forms I think both depend on a grid intertie, the whispergen in dc plus battery plus inverter is used islanded in remote sites. Capital cost is still a big issue and I still wonder if a Honda on lpg with 1/4 the life may be more economic, especially if the proportion of heat demand were lower.

AJH

[IMM]

As with anything made by FIAT. These days, with fully synthetic oils longevity would not be a problem. Then having a conventional crank two stroke...

[Dave Liquorice]

With a grid supply that shakey I'd be gathering information from a UPS capable of logging and using it to beat the suplier about the head with.

We live in one of the remotest parts of England at 1400' fed by overhead line probably all the way from the power station. It's certainly overhead to the 125kV/33kV substation 25 miles away and that line rises to 2000' over the fells. Our power is stable and reliable.

In the last 5 years I doubt that there has been more than 5 cuts lasting >1hr and a perhaps double that number of 1s cuts when the auto-recloser detects a surge/fault and operates.

[Nick Finnigan]

Yes, but you are also suggesting it as a 'boiler upgrade', when many people would find it unsuitable for that.

(Specs at

and ac.html including a dodgy cost justification for UK houses).

[Steve Firth]

Yes I have.

No, it's bloody useless. It may (just) make sense on a boat but the Whispergen and the other Stirling engine generators produce insufficient energy to make much sense as a standalone installation. It may (just) make sense if installed to supply excess energy back to the Grid but at those times of day you proabably don't want the heat generation anyway.

I have a house which is remote from mains electricity, alsthough I do have a mains connection to the house, I haven't got around to paying for it to be connected to the consumer unit. At present I make do with a

2.4kVA generator, some UPSs and that's it. I'm investigating using wind generators since the house is an exposed location and I can fairly well guarantee a strong wind in the morning and evening each day. A windgen with the same output as the Whispergen can be had for about 1/4 to 1/8th the price. The only thing that put me off is the noise.

I was considering backing up the wind generator with PV panels. Also CHP from an LPG genrator may help me to get the best out of the generator particularly if I run it from a bulk gas supply.