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!!!

What about the Drake Landing Solar Community in Canada?

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).

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 95ºC and arriving in
London at 95.1ºC 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.

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.................

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.

<blockquote><cite>Posted By: orangemannot</cite>Erm
If the water arrives .1 degree C hotter than it left the power station
How is there a 30MW heat loss
scratches head?</blockquote>

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.

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 £6k each, and 9 boiler installations.

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

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?

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.

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.

Seret +1

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.)

Found the article at last!

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

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.