Why doesn't the UK have combined heat and power generators like Denmark?

[Dave2002]

I've been thinking about the effectiveness and costs of heating. We mostly use gas for heating, but in a newly built conservatory we have electric underfloor heating and also an air conditioning unit which functions as an air source heat pump in the winter.

For heating it seems to me that gas has to be the best. Simple electric heating, such as our underfloor heating, or heating via radiators or storage heaters requires the power station to generate electricity, which is known to be less than 50% efficient, and then there are distribution losses, which reduce the efficiency further. Probably for each unit of gas or similar fossil fuel burnt at the power station, we are getting the equivalent of burning 0.3 units in our home. In the UK a large amount of energy in the form of heat is simply dumped into the atmosphere. In Denmark the overall efficiency of energy production is improved by using the heat from power stations for space heating in nearby urban locations, and I believe they have some of the most efficient power stations in the world.

Our domestic situation changes somewhat when we consider using the air source heat pump. As measured, it seems to have a factor of between 2.5 and 3 re electricity input versus heat output. 2kW of electricity in produces close to 6kW of heat out. Thus using the heat pump may overall from our point of view not be significantly worse than burning gas, though would still cost more. However, there would still be a significant amount of heat generated "on our behalf" at the power station for each unit of heat we consume using the heat pump.

Of course the UK seems to want to have an "out of sight, out of mind" to electricity generation, and this also promulgates the view that electricity is clean. Clearly it is rather clean at the point of use, but at the generating plant it may be anything but. It's not totally unreasonable. Switch transport and other energy consuming systems in cities to electricity, and the local environment is improved. On the other hand, the environment in some other part of the country may be worsened as a result.

[An_Inspector_Calls]

McKay has a very good chapter on heating in his book Sustainable Energy without the hot air. The book is available free on line:

http://www.withouthotair.com/

The chapter on smarter heating is the one you want (chapter 21).

This explains why CHP may not be the best approach to solving our heating needs. Incidentally, Denmark's CHP operations illustrates McKay's point about the difficulty of blending the energy calls on CHP to optimise efficiency - when we need heat might not be the time when we want electricity. Denmark is largely an agricultural economy and the CHPs end up being use as process heat generators during the day and electricity generators at night, seldom both together. (In fact, there's little the Danes have got right about electricity generation. With all their wind they end up exporting subsidy to Norway/Germany when there's an excess of wind power, and then importing Norway's hydro power at European prices when there's no wind. Not surprisingly, they have the highest electricity prices in Europe).

I seem to be doing exactly what McKay advocates. I have a ground source heat pump (we're not on the gas grid), it works very well indeed, and I've nearly completed lagging the external walls of the house with 90 mm of insulating board. McKay also makes the case for air source heat pumps. I've no experience of these but friends in NZ swear by them. The only thing that would put me off those would be noise levels, but maybe the modern versions are quieter.

[Oldcrofter]

Here's the pro argument in easy-to-follow language:

http://www.greenpeace.org.uk/climate/solutions/combined-heat-and-power-chp

"In Denmark district heating covers more than 60% of space heating and water heating. In 2007, 80.5% of this heat was produced by combined heat and power plants. Heat recovered from waste incineration accounted for 20.4% of the total Danish district heat production." (Wiki)


And here's a short presentation (seems to be silent ?) of how combined heat & power generation works :

http://www.youtube.com/watch?v=dRqqUCLjmqE

[ahinton]

McKay has a very good chapter on heating in his book Sustainable Energy without the hot air. The book is available free on line:

http://www.withouthotair.com/

The chapter on smarter heating is the one you want (chapter 21).

This explains why CHP may not be the best approach to solving our heating needs. Incidentally, Denmark's CHP operations illustrates McKay's point about the difficulty of blending the energy calls on CHP to optimise efficiency - when we need heat might not be the time when we want electricity. Denmark is largely an agricultural economy and the CHPs end up being use as process heat generators during the day and electricity generators at night, seldom both together. (In fact, there's little the Danes have got right about electricity generation. With all their wind they end up exporting subsidy to Norway/Germany when there's an excess of wind power, and then importing Norway's hydro power at European prices when there's no wind. Not surprisingly, they have the highest electricity prices in Europe).

I seem to be doing exactly what McKay advocates. I have a ground source heat pump (we're not on the gas grid), it works very well indeed, and I've nearly completed lagging the external walls of the house with 90 mm of insulating board. McKay also makes the case for air source heat pumps. I've no experience of these but friends in NZ swear by them. The only thing that would put me off those would be noise levels, but maybe the modern versions are quieter.

They are indeed quieter than they used to be but careful siting can also help reduce the effect of the noise problem to a point. They're good news but they are quite electricity hungry, though.

[Oldcrofter]

Alternatively, Dave2002, you could try one of these in your conservatory

http://www.youtube.com/watch?feature=endscreen&v=FyJdojJJSFY&NR=1

[Resurrection Man]

Interesting post. A little bit of quick digging produced this chart http://www.mpoweruk.com/energy_efficiency.htm

I haven't had time to dive into the provenance if the website to see what particular spin they are putting on things...(see what I did there? Having only recently learned how hypocritical the Guardian is, especially vis a vis tax avoidance, I now am very sceptical of anything I see or read...not before time, too). You are pretty much on the mark I'd say with your gas efficiency of 30%...the chart claims 40% efficiency for gas turbines less 10% for distribution losses. Or is that 10% off of 30%...anyway, right ballpark. I was very surprised at the relative inefficiency of nuclear fission power generation but that might be down to a fundamental law of physics (Carnot's Efficiency Law) although surely that would apply to coal and oil turbines as much as for nuclear.

Wind power is way down there...yet another good reason not to build the things on land.

You are correct re Denmark and CHP...they are at the theoretical maximum according to this report

http://www.google.co.uk/url?sa=t&rct...2UypjF2E9qmDUQ

And then again it's not all hunky-dory.

http://www.telegraph.co.uk/news/worl...evolution.html

But to ask the question why not the UK then there are many other factors that have to be brought into mind....size of country, population density, topology, etc that possibly makes the UK not as viable.

[Resurrection Man]

McKay has a very good chapter on heating in his book Sustainable Energy without the hot air. The book is available free on line:

http://www.withouthotair.com/

The chapter on smarter heating is the one you want (chapter 21).

This explains why CHP may not be the best approach to solving our heating needs. Incidentally, Denmark's CHP operations illustrates McKay's point about the difficulty of blending the energy calls on CHP to optimise efficiency - when we need heat might not be the time when we want electricity. Denmark is largely an agricultural economy and the CHPs end up being use as process heat generators during the day and electricity generators at night, seldom both together. (In fact, there's little the Danes have got right about electricity generation. With all their wind they end up exporting subsidy to Norway/Germany when there's an excess of wind power, and then importing Norway's hydro power at European prices when there's no wind. Not surprisingly, they have the highest electricity prices in Europe).

I seem to be doing exactly what McKay advocates. I have a ground source heat pump (we're not on the gas grid), it works very well indeed, and I've nearly completed lagging the external walls of the house with 90 mm of insulating board. McKay also makes the case for air source heat pumps. I've no experience of these but friends in NZ swear by them. The only thing that would put me off those would be noise levels, but maybe the modern versions are quieter.

What did you do at your window reveals after the 90mm board was added? Do you have any figures on cost etc as we're interested in this.

[Dave2002]

They are indeed quieter than they used to be but careful siting can also help reduce the effect of the noise problem to a point. They're good news but they are quite electricity hungry, though.

The noise from the external fan system is higher than I'd hoped for. It may be posible to put something around it to reduce the noise, but it's quite disappointing. Re electricity consumption, I think this really is due to the amount of heat required. As far as I can see our unit behaves like a 5kW fan heater, while the consumption is around 2 kW or lower.

It's unfair to say that they are power hungry if they are required to put out a lot of heat.

For comparison if you drive to and from work and use (say) one gallon of petrol that's equivalent to around 40 kWh. Many people don't think much about how much petrol they're using, though more are becoming conscious of costs nowadays. Most of us have little feel for how natural gas costs and energy output and efficiency compare with electricity or petrol.

At this time of year trying to kep a conservatory warm is pretty much a losing battle, though on sunny days it does become comfortable either with no heating or minimal heating.

The underfloor heating feels like a complete waste of effort for this time of year. It soaks up energy (4-5kW) for minimal effect on comfort and temperature. Some people claim that these act like a heat store (salesmen!!!! **) but although there is some storage effect, the heat loss is so great that it is a very wasteful and expensive way of heating. The reason why we didn't have a water based system is that we had a bad experience with a leak in our heating system, which was very expensive and time consuming to deal with. Fortunately the insurance covered most of the financial peoblems, but it did put me off circulating water systems.

** I dislike most salesmen. They have no interest at all in considering running costs and efficiency. Smug *****. They sell stuff and move on .... leaving buyers with expensive problems.

[An_Inspector_Calls]

RM
The windows remain in their original position so they're now 90 mm (+10 mm skim) in from the brick/block outer surface. The reveals were stripped to blockwork and then lagged with 20 mm external insulation plus 10 mm skim. Every effort was made to kill thermal bridging points.

Cost: a lot! On heat savings alone the payback period would be about 20 years. But that's if electricity/fuel prices stay the same and they won't: given our previous and current energy policies, they'll increase. The payback gets longer, of course, if you gone and installed a heat pump first! However, in our case there are other factors which make the project more attractive:
(a) choose a skim that requires no painting. That's a big saving in our case because I no longer fancy going up ladders, and contract painters would probably require scaffolding for certain parts of the house, and
(b) parts of the old rendering were buggered anyway, probably as a result of global warming causing four bad winters in a row.

As another unexpected plus, although the house is no warmer it's feels much more comfortable. I put this down to the inside temperature being very even. You even feel comfortable if you lower the temperatue slightly!

The heat pump is now running on a sniff of electricity, and our consumption is less than an average of 13 kWh/day (204 m^2 floor area).

I'm not very impressed with your reference to mpoweruk. Gas burning to produce electricity can now be >= 60 % efficient.http://www.powerengineeringint.com/a...y-barrier.html.

[Resurrection Man]

RM
The windows remain in their original position so they're now 90 mm (+10 mm skim) in from the brick/block outer surface. The reveals were stripped to blockwork and then lagged with 20 mm external insulation plus 10 mm skim. Every effort was made to kill thermal bridging points.

Cost: a lot! On heat savings alone the payback period would be about 20 years. But that's if electricity/fuel prices stay the same and they won't: given our previous and current energy policies, they'll increase. The payback gets longer, of course, if you gone and installed a heat pump first! However, in our case there are other factors which make the project more attractive:
(a) choose a skim that requires no painting. That's a big saving in our case because I no longer fancy going up ladders, and contract painters would probably require scaffolding for certain parts of the house, and
(b) parts of the old rendering were buggered anyway, probably as a result of global warming causing four bad winters in a row.

As another unexpected plus, although the house is no warmer it's feels much more comfortable. I put this down to the inside temperature being very even. You even feel comfortable if you lower the temperatue slightly!

The heat pump is now running on a sniff of electricity, and our consumption is less than an average of 13 kWh/day (204 m^2 floor area).

I'm not very impressed with your reference to mpoweruk. Gas burning to produce electricity can now be >= 60 % efficient.http://www.powerengineeringint.com/a...y-barrier.html.

Thanks for the info.

Re the mpoweruk link....wasn't meant to be definitive by any stretch of the imagination. However, your link refers to futures to a certain extent. How many gas turbine generation plants out there are at 60%? I suggest a very small number compared to the more normal 40%.

[Dave2002]

The heat pump is now running on a sniff of electricity, and our consumption is less than an average of 13 kWh/day (204 m^2 floor area).

Is that 13 kWh/day total, including all other consumption, or only heating? Is any other form of heating used (regularly)? [We use gas and electricity. I recall you have no gas supply, and I don't expect you're using oil or other fuels.]

Our total floor area, excluding the garage is perhaps comparable to yours. I am thinking of putting insulation boards into the garage, which has walls which back onto the internal house walls.

[An_Inspector_Calls]

Is that 13 kWh/day total, including all other consumption, or only heating? Is any other form of heating used (regularly)? [We use gas and electricity. I recall you have no gas supply, and I don't expect you're using oil or other fuels.]

Our total floor area, excluding the garage is perhaps comparable to yours. I am thinking of putting insulation boards into the garage, which has walls which back onto the internal house walls.

There's no other heating of any significance. We do have a wood-burning stove and an open fire but these are only lit on feast days in the winter and use wood which we get from our very smallholding. The heat usage figure includes space heating and all our hot water all from the heat pump.

[Dave2002]

That's about 4760 kWh/year. You should be able to get at least 50% of that from a 4 kW PV array, though the opportunities to get government subsidies have been dwindling fast. Current cost maybe £8k. Of course in the winter supply would not match demand, and the situation might reverse in the summer. An 8kW array might be £12-14k now, and arguably could do well in the summer - e.g. drive fridges, washing machines etc. not so good in the winter.

[An_Inspector_Calls]

Yes, that's correct, just under 5MWh/annum. A PV array wouldn't be much use for this load because most of it occurs during winter. Besides, I think PV arrays are very ugly and I'm loath to spoil a good slate roof. A windmill might be more to the point, but again, no thanks, I'd rather not have the noise. For an old house, I'm happy with where we are. I can always act smug with any greenies I chance upon and if Ed Davey does the RHI then I'll forsake my ethical stance on robbing Peter to pay Paul, take the money, and bore people to death at dinner parties with my tales of how much susbidy I'm claiming as revenge for all their crap about PV arrays!

[Dave2002]

Yes, that's correct, just under 5MWh/annum. A PV array wouldn't be much use for this load because most of it occurs during winter. Besides, I think PV arrays are very ugly and I'm loath to spoil a good slate roof. A windmill might be more to the point, but again, no thanks, I'd rather not have the noise. For an old house, I'm happy with where we are. I can always act smug with any greenies I chance upon and if Ed Davey does the RHI then I'll forsake my ethical stance on robbing Peter to pay Paul, take the money, and bore people to death at dinner parties with my tales of how much susbidy I'm claiming as revenge for all their crap about PV arrays!

Re PVs - agree most of the time in the winter you'd have to pull power from the grid. If you view the grid as a storage system then it could work for you - averaged over the year. PVs installed without subsidy or FiTs will take a long time to break even - if they ever do, without low installatiion costs. A 4kW array needs to be under £6k to be in with a chance.

if your house is old and attractive then not wanting to spoil the roof with PVs makes sense. There are sometimes other solutions, such as putting them on sheds or garages, or in valley roof areas.

Re windmills, they're not much good unless your locatiion is favourable and you might need to install one at least 30 metres up get reasonable results - see http://www.greenspec.co.uk/small-wind-turbines.php which is quite good apart from the epelling of "rotor". The noise could be a pain if installed too close to your house.

I don't see how you'll be able to get any money from the Renewable Heat Initiative. These schemes do not usually work retroactively, so as you've already intstalled a heat pump system, I don't see Ed Davey paying you for a replacement system. http://www.decc.gov.uk/en/content/cm...incentive.aspx