Question: Gas to electricity generators

tunnel

captainhindsight wrote: »

So it does, couldn't see it on the mcs website though. Probably doesn't mean much, mcs don't tend to update there site very often

I doubt it would be on there just yet as the boiler is due for launch in January next year, interesting that they're hoping to bring out a combi boiler that does the same, hence for the moment why I'm just keeping an eye on it(no separate water tank here)

Johnandabby

tunnel wrote: »

I doubt it would be on there just yet as the boiler is due for launch in January next year, interesting that they're hoping to bring out a combi boiler that does the same, hence for the moment why I'm just keeping an eye on it(no separate water tank here)

They're unlikely to bring out a combi version, as they won't get a sufficient period of heating to get stable electricity generation - heating a hot water cylinder helps provide this each day. That's the main issue I've had with the Baxi Ecogen, it only works in a poorly insulated house where there's a large enough and consistent heat demand - in a lot of new or well insulated houses the boiler only comes on intermittently, which doesn't work with the electricity generation aspect.

captainhindsight_2

Johnandabby wrote: »

They're unlikely to bring out a combi version, as they won't get a sufficient period of heating to get stable electricity generation - heating a hot water cylinder helps provide this each day. That's the main issue I've had with the Baxi Ecogen, it only works in a poorly insulated house where there's a large enough and consistent heat demand - in a lot of new or well insulated houses the boiler only comes on intermittently, which doesn't work with the electricity generation aspect.

This is a problem with chp you need somewhere to dump the heat.

(Smily Dan no comments.... Lol. )

Martyn1981

captainhindsight wrote: »

T
(Smily Dan no comments.... Lol. )

I don't understand your repeated comments about Smiley Dan ..... he seems to me to be correct!

If you re-read the OP you'll see that they acknowledge the existence of CHP boilers, but specifically ask if there are electricity generators that use gas without being boilers aka standalone.

If you read the first response, you'll see that Zeup answered the question as he mentioned methane fuel cells which do this, but has also pointed out the loss of efficiency when the heat 'benefit' is not used.

Mart.

captainhindsight_2

Martyn1981 wrote: »

I don't understand your repeated comments about Smiley Dan ..... he seems to me to be correct!

If you re-read the OP you'll see that they acknowledge the existence of CHP boilers, but specifically ask if there are electricity generators that use gas without being boilers aka standalone.

If you read the first response, you'll see that Zeup answered the question as he mentioned methane fuel cells which do this, but has also pointed out the loss of efficiency when the heat 'benefit' is not used.

Mart.

A chp is not a boiler it is a electricity generator and the bi product is heat , he was wrong.

Smiley_Dan

captainhindsight wrote: »

Yes a boiler that produces electricity, and qualifies for fit payments. Most boilers don't do that...

Erm... I'm not having a go, I'm just saying the OP's VERY FIRST sentence said "I see that there are boilers that incorporate gas to electricity generators.". So I think he realises there's such a thing as Micro CHP boilers.

TBH I wasn't aware of your distinction of something that produces heat as a bi-product. But Baxi seem to think it's a condensing boiler too: http://www.baxi.co.uk/documents/ecogen-user-instructions.pdf

Re-reading their website in the light of CH's comments I suppose it is a bit unambiguous. How many kW heat output do these things have? Are they enough for normal domestic situations?

Anyway...

Sterlingtimes

Thank you, all posters. So a generator using cheap gas to generate more expensive electricity may make sense despite the inefficiencies introduced, but the problem would be feeding it all back to the Grid without compensation. Is that right?

The boiler matter is a different issue. It strikes me that the intermittent nature of the fire up of a domestic boiler produces electricity on a start stop basis that may not conincide with electricity demand from within the home.

lstar337

Sterlingtimes wrote: »

Thank you, all posters. So a generator using cheap gas to generate more expensive electricity may make sense despite the inefficiencies introduced, but the problem would be feeding it all back to the Grid without compensation. Is that right?

The boiler matter is a different issue. It strikes me that the intermittent nature of the fire up of a domestic boiler produces electricity on a start stop basis that may not conincide with electricity demand from within the home.

I'm guessing it makes little sense in a well insulated home as the boiler will not be on enough. I live in an A rated house and the heating is only on for 1 hour a day to maintain a constant 21c in main living room and 18c throughout the rest. 1 hour a day of electric just wouldn't make sense for me.

In a poorly insulated house where the boiler will be running longer I can see a use. Even only generating 1kW it will be taking care of all of the boilers usage plus some of the base line usage.

Not sure it will pay for itself in anything but a poorly insulated house with a lot of heating requirement.

zeupater

captainhindsight wrote: »

A chp is not a boiler it is a electricity generator and the bi product is heat , he was wrong.

Hi

I take it that the above didn't relate to Mart's note about my post (#2) because it's right.

Now for Smiley Dan's comment "Erm... that's a boiler." .... considering that the OPs original question was "I see that there are boilers that incorporate gas to electricity generators. Why cannot we not buy domestic standalone gas to electricity generators? ", I'd tend to agree, it's a boiler because that's the primary function - heating, albeit with a little bit of co-generation thrown in ... it certainly isn't a standalone generator.

As it stands, the only technology that looks to fit the requirement is fuel cell, some of which claim to have a roughly 50/50 split heat to electricity with a combined 90%+ fuel energy recovery whatever the operating duty, so ~45% electricity generation efficiency on gas purchased if the heat cannot be utilised.

HTH
Z

zeupater

tunnel wrote: »

I'm keeping an eye on this one
What better to compliment my solar than a boiler that generates leccy in the dark cold winter months when the boiler is always on

Hi tunnel

Have a good read of the specs and have a look at the technology explanation ...

What you effectively get is a 18kW boiler which can generate 1kW of electricity at full bore .... the boiler can modulate down to 6.8kW, however there is no performance curve (as mentioned in a previous thread).

Electricity is described as being generated through a scroll expander ... the rate of expansion will obviously depend on various factors, but taking the 'system' as being of fixed dimensions you effectively have a turbine which is being driven by the temperature of the combustion process, so something like a wind turbine ... if the flow rate is halved then the power available for the turbine to capture is reduced to 1/8 (0.5x0.5x0.5), therefore 125W (1000/8) ...

Okay then .... let's look at an average property having an annual gas heating demand (space & DHW) of 16500kWh. If the full demand is serviced at full bore with no heat waste, we get an operating time of 892Hrs (16500/18.5) thus producing less than 900(892x1) kWh of electricity ... nowhere near the 2000kWh in the tech specs ... so, with the full heat requirement met, the additional 1100kWh(2000-900) of electricity would need to be generated with 100% heat loss, at 92% efficiency, therefore we get 20.1kWh(18.5/1/0.92) of gas burned to generate 1kWh of electricity .... take gas at 4p/kWh, you're paying over 80p/kWh to top your FiT income up to 2000kWh worth of income/year ... (but where does all that heat get dumped ?)

Now, what happens if, when in use, the boiler averages 50% duty, then the annual 16500kWh is delivered over 1790Hrs(16500/(18.5/2)) ... that's an average 4.9Hrs/day(1790/365)- all year. Without a performance curve or further technical details, lets assume 1/8 electricity, therefore a lower end estimate of 112kWh/year (892/8) ...

Starting to get the picture ? ... deemed FiT ? .. no wonder, if it was metered there'd be some really upset consumers ...

Shall we look at summer ? .... guess at 5kWh.t/day DHW ... say 30 minutes of generation/day - ramping down from 18.5kW to minimum ... so 500Wh/day maximum, realistically less .... time it to best effect, using it all and it might save you £15/year over the summer and earn about 6p/day in FiT payments ...

Now, what is the cost of one of these, ermmmm .... boilers ??? - and considering the variables, I wonder what the breakeven point would be ?

Food for thought ...

HTH
Z