Green Building Forum - District Heating Myths

District Heating Myths

tony — Thu, 22 Sep 2011 12:43:29 +0100

District heating systems which are common in some other countries can prove cheaper to run than the combined cost of a comparable number of individual systems. However as heat losses of the houses are fixed no energy can possibly be saved. The efficiency of the individual modern boilers prevalent in the UK are now sufficiently high to make centralised systems uncompetitive in pure energy terms though on running cost only grounds they may compete.

There are unfortunately the distribution losses to consider. These will always be high as insulating the pipes can only reduce the heat wasted not eliminate it. Then there are the high infrastructure costs to deal with not to mention the disruptive nature of the work needed to link existing homes together. This last aspect makes it a non starter for me.

To suggest that district heating of uninsulated homes could work out more energy efficient than the use of insulation .. well have lost out minds!!!

District Heating Myths

JSHarris — Thu, 22 Sep 2011 12:54:12 +0100

The only scenario where I think large scale district heating makes sense is one where there is an abundance of geothermal or waste heat from some other essential process (power generation, perhaps).

In all other cases, as you rightly point out, the distribution losses outweigh the increased efficiency that might be possible from the larger heat generation source.

The other exception to this general principle might be local CHP systems, using a single CHP unit to run a few homes clustered tightly together.

District Heating Myths

bella — Thu, 22 Sep 2011 12:57:31 +0100

What about the Drake Landing Solar Community in Canada?

District Heating Myths

jamesingram — Thu, 22 Sep 2011 13:32:58 +0100

I believe district heating and CHP of well insulated urban flats/homes is common in Scandinavia
If you're looking for a solution to energy efficent building they seem a good few years ahead of us.

Though the CSH road map seem to be heading there fine.

District Heating Myths

JSHarris — Thu, 22 Sep 2011 13:53:26 +0100

I guess this depends on what is meant by "district heating" and also whether or not efficiency is factored in.

The Drake Landing Solar Community is using renewable energy collectively, but is it as efficient as each house having its own seasonal thermal store? I'm pretty sure it's not, but the economics of sharing a seasonal thermal store amongst a tightly integrated community may have outweighed the slightly lower overall efficiency.

If we look at tightly packed urban environments (flats and apartments within a common building envelope, for example) then centralised heating seems to make sense. I'm not sure that this really falls into what we usually mean by "district heating" though; certainly I think of it as district wide systems, like the distributed steam systems that were commonplace in some big US cities (and often the source of the steam emanating from manholes that we still see in some old films).

District Heating Myths

SteamyTea — Thu, 22 Sep 2011 14:08:27 +0100

Human behaviour can also effect energy use. In Moscow it is not uncommon to see flats with windows open in the winter.
If most of us had a 'fixed fee' for heating would we use less. Seems there is some evidence that fitting water meters reduces individual households use. What would happen if we had a fixed fee for motoring, say Â£50 a week for as much fuel as we like?
Not saying that you cannot meter individual use on a shared system, but it does to to build in waste and inefficiency.

District Heating Myths

djh — Thu, 22 Sep 2011 14:09:16 +0100

Posted By: tony: "To suggest that district heating of uninsulated homes could work out more energy efficient than the use of insulation .. well have lost out minds!!!"

I take it you're commenting on the article in Green Building magazine, which in turn refers to this article - http://www.orchardpartners.co.uk/Docs/HarnessThisHeat.pdf - and I guess you haven't read it.

The article refers specifically to waste heat collected from power stations, which starts from a base of zero cost and zero extra CO2, because the waste heat is already there. Of course there are distribution costs, but the case is by no means as clearcut as you might think.

There's one especially eye-catching proposal in Orchard's article:

'Claus Hojlund Rasmussen, who has designed
a number of the largest heat transmission systems
in Denmark, has done a back-of-an-envelope
calculation for a pipeline to serve London
with heat from Sizewell nuclear power station
128km along the coast in Suffolk. A 2m diameter
line would carry 2200MW of heat, leaving
the power station at 95ÂºC and arriving in
London at 95.1ÂºC after picking up pump energy
as heat from the pipe friction. Offset against
this heat would be the pump load at 54MW and
the heat loss of 30MW. The CO2 footprint for
this heat (assuming the electricity for pumping
came from coal-fired power) would be 0.026kg
CO2/kWh. Whether the cost of the line would be
economic is another matter.'

It makes an interesting read.

District Heating Myths

SteamyTea — Thu, 22 Sep 2011 14:16:25 +0100

I have not read it, but did it mention local losses. These are akin to stepdown transformers and smaller cabling in towns. The electrical grid looses most of its energy here not in the bulk transmission lines.

District Heating Myths

JSHarris — Thu, 22 Sep 2011 14:23:28 +0100

The figures for pumping hot water from Sizewell look encouraging. The next logical step would be to create a planning rule that says that any new power station has to be bang in the centre of a community large enough to use all the waste heat.................

District Heating Myths

SteamyTea — Thu, 22 Sep 2011 14:34:46 +0100

Posted By: JSHarrisThe next logical step would be to create a planning rule that says that any new power station has to be bang in the centre of a community large enough to use all the waste heat.................

Each housing estate must be forced to have a local energy from waste incinerator, it just has to be carbon neutral as it is local. Is that why the Green Party like district heating so much. I think they should try the first one in Brighton, be nice view from the Pavilion.
If they put in in the local school yard, next to the mobile mast, the locals can admire it next time they cast a vote

District Heating Myths

renewablejohn — Thu, 22 Sep 2011 14:38:45 +0100

Posted By: JSHarrisThe figures for pumping hot water from Sizewell look encouraging. The next logical step would be to create a planning rule that says that any new power station has to be bang in the centre of a community large enough to use all the waste heat.................http://1.2.3.10/bmi/www.greenbuildingforum.co.uk/forum114/extensions/Vanillacons/smilies/standard/devil.gif" alt="" title="" >

Nothing wrong with that and while your at it the minimum electrical efficiency should be 40% and overall efficiency 80%. Start with all towns with population in excess of 100k.

District Heating Myths

orangemannot — Thu, 22 Sep 2011 16:35:43 +0100

Erm
If the water arrives .1 degree C hotter than it left the power station
How is there a 30MW heat loss
scratches head?

District Heating Myths

JSHarris — Thu, 22 Sep 2011 16:49:59 +0100

Posted By: orangemannotErm
If the water arrives .1 degree C hotter than it left the power station
How is there a 30MW heat loss
scratches head?

Because there is an additional power input of 54MW to drive the pumps. The total power input is therefore 30MW greater than the total power output.

District Heating Myths

djh — Fri, 23 Sep 2011 14:14:44 +0100

Posted By: SteamyTeaI have not read it, but did it mention local losses.

Yes, but his point is that since the cost of the heat is zero (since its waste heat) there's no cost for the losses either in this case. Its not quite so simple when he works through it of course, but he does take losses into account.

District Heating Myths

converse — Wed, 22 Feb 2012 16:26:12 +0000

So on a new small development, why wouldn't it be cheaper to install one big boiler, with one gas connection, and then ship the output as hot water to say 9 terraced houses? This approach would also be easier to integrate with solar, surely.

The alternative is 9 lots of gas connections at about Â£6k each, and 9 boiler installations.

In other words, why connect gas when you could connect metered hot water instead?

District Heating Myths

SteamyTea — Wed, 22 Feb 2012 17:01:06 +0000

Posted By: converseSo on a new small development, why wouldn't it be cheaper to install one big boiler

It is down to how the energy is stored. With Gas it can be stored happily in a tank until needed, unless there is a leak, the losses are zero.
Store heat, and even if there is no use it will be loosing energy by the second, the hotter it is compared to the surroundings the greater the losses.

It is a balance between the efficiency of individual boilers and the efficiencies of heat storage. That is before you get into the piping costs, individual metering, over use (if you want a hot shower and there is no hot water you are stuc,k regardless of what you are willing to pay).

District Heating Myths

converse — Wed, 22 Feb 2012 17:29:36 +0000

But if you're going to have any hot water storage at all, surely it's better to have one big communal store rather than one small store? It's easier to insulate, and easier to integrate with feeds from other energy sources that way.

Or are you saying have no hot water storage and instead use multiple combi boilers close to the point of use? I'm talking about a small scale development here BTW, not introducing a ditrict wide heat main. Conceptually, it seems no different to delivering hot water to a hotel, which is largely done with a single boiler, no?

District Heating Myths

fostertom — Wed, 22 Feb 2012 17:35:46 +0000

Posted By: tonyas heat losses of the houses are fixed no energy can possibly be saved

Not so -

instead of the power station generating its heat and throwing 65% of it away
plus the individual houses generating their own heat,

with district heating the power station generates same heat as before but throws only 30% (say) of it away
the individual houses don't generate any heat
but instead use the 35% of power station heat that was formerly thrown away.

So all the heat previously generated by the houses is saved - not created - the houses are heated 'free'
(without even needing insulation measures - that's a saving to be set against the district heating infrastructure cost).

In theory.

District Heating Myths

SteamyTea — Wed, 22 Feb 2012 18:32:13 +0000

Posted By: converseBut if you're going to have any hot water storage at all, surely it's better to have one big communal store rather than one small store?

Yes this is true, but not always in practice, go see how warm your airing cupboard is compared to your house. You have to take pipe losses into account. They increase the surface area of the store significantly. Then there are thermal losses when the water in the pipe is static, or how long do you run the tap until it is the right temperature. JSHarris has done a thread on this for his new house.

Not having storage is often considered more effective, and does seem to make sense, though without seeing hard data it is hard to really tell (not that we want facts to get in the way).

It really does come down to modelling as there is not a 'one size fits all' solution. Decide what you think will work, draw it up so you know the sizes of everything i.e. boiler size and run times, store size, pipe runs, recirculation or not and then run a simulation comparing it against a combo and an individual domestic storage system.
It is the only way.

District Heating Myths

tony — Wed, 22 Feb 2012 19:12:12 +0000

When you disagree with me about it not being possible to save any energy as the heat losses from individual houses are fixed

Note that sending in extra energy in the form of heat is cheating!!

District Heating Myths

Brianwilson — Wed, 22 Feb 2012 20:39:07 +0000

With good quality district heating a fundamental consideration is do not place all your eggs in one basket. At least two boiler systems are needed to cover failure and scheduled maintenance. Placing EFW plant in conurbation creates air pollution impact problems exacerbated by poor UK regs.

District Heating Myths

Seret — Fri, 24 Feb 2012 08:52:26 +0000

Well, local authorities need a way to get rid of their waste, and incinerating it on their doorstep is an attractive option instead of trucking it miles and miles away. The problem is that even when we do build an EFW plant with CHP we still don't connect it up to the local district heating (just take SelCHP in South London). So the district heating scheme less than a mile away carries on burning fuel to heat the council's enormous blocks of flats, and SelCHP blows all it's waste heat into the atmosphere. Perhaps it should change it's name to SelactuallynotCHPatall.

I'm told the problem is that the local authorities don't view their waste as a resource, and aren't interested in spending money to access that resource. Clearly something's very wrong with a system that mandates installing the CHP gear, and then doesn't enable its' use.

EDIT: Actually, after a quick Google it looks like Southwark are finally laying the pipework to sort it out in the next couple of years. Only took them about 20 years then.

District Heating Myths

Joiner — Fri, 24 Feb 2012 09:09:26 +0000

Seret +1

District Heating Myths

HalcyonRichard — Fri, 24 Feb 2012 09:52:34 +0000

Hi,
Is it the initial capital cost that the council/companies think about and not the long term savings ? Does anyone know what the capital cost per house is to install the pipes/monitoring in a typical district CHP.

Regards Richard

District Heating Myths

Joiner — Fri, 24 Feb 2012 10:07:43 +0000

http://news.bbc.co.uk/1/hi/england/shropshire/7598156.stm

The development featured on a Countryfile programme a couple of years ago. But a lot of silence since then!

Shropshire Council, despite still showing the scheme as a flagship enterprise on their web site, either removed or reduced their subsidy to the scheme some time ago, although I'm not sure what the current state of play is on that score. (I'll try and find out.)

District Heating Myths

Joiner — Fri, 24 Feb 2012 10:27:40 +0000

Just got off the phone with a guy at Shropshire Council. The Ludlow plant is still going at full capacity. What stopped was the shipping-in of waste from what would have been other District Council areas before the county went unitary, for the simple reason that the cost couldn't be justified when there were alternative schemes running alongside it that didn't have the costs, like allowing food waste to be included with garden waste and sent for composting, and in other areas where food waste simply couldn't be treated as anything other than waste and sent to landfill.

That's a simplistic explanation, the details were such that I couldn't relate them here without going on for a whole page. Nuff said that whilst everyone was paying the same council tax, not everyone was able to get the same service.

But, yes, the Ludlow scheme is still operating and proved the soundness of the idea. And other schemes have been rolled out across the UK (planned for Wales) on the basis of the success of that pilot scheme in Ludlow.

(Oh, and the scheme cost the council nothing, having received government money to build and run it.)

District Heating Myths

Joiner — Sat, 03 Mar 2012 10:23:13 +0000

Found the article at last!

http://www.shropshirestar.com/news/2010/09/16/shropshire-food-waste-collection-too-expensive-for-councillors/

District Heating Myths

WillInAberdeen — Sun, 04 Mar 2012 09:12:59 +0000

http://www.aberdeenheatandpower.co.uk/

"Aberdeen Heat & Power Ltd is a â€˜not for profitâ€™ company that was set up by Aberdeen City Council in 2002 to develop and operate district heating and CHP (Combined Heat & Power) schemes in their area. The scheme .. supplies around 1200 flats in multi story blocks and 8 public buildings. Carbon emissions from these buildings have reduced by 45% and typical fuel costs to tenants have been reduced by 50% over the previous heating system. "

District Heating Myths

tony — Sun, 04 Mar 2012 09:54:08 +0000

how do you define carbon emissions? belting out CO2 (and pollutants) from a chimney and calling it zero is not right and do the health costs get added into the cost side?

I like the idea of reduced cost but would prefer to see reduced energy use.

District Heating Myths

Joiner — Sun, 04 Mar 2012 10:04:05 +0000

Can't see any details of emissions, Tony, so why put it down before the facts are known?

Any more info to allow an informed opinion to be expressed, Will?