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"ban gas in new homes"
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kenneal - lagger
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Joined: 20 Sep 2006
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Location: Newbury, Berkshire

PostPosted: Fri Mar 15, 2019 3:49 pm    Post subject: Reply with quote

The main saving on a district heating system is the removal of the requirement for a separate boiler in each house and the cost of supplying the energy source to it.
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adam2
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Joined: 02 Jul 2007
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Location: North Somerset

PostPosted: Fri Mar 15, 2019 4:16 pm    Post subject: Reply with quote

stumuz1 wrote:
Is there any milage in district heating?

It has long bothered me that most boilers take cold water from the ground and heat it up in the house.

Wouldn't be more efficient to take water from the ground to a covered reservoir (first increase in temp) then throw the renewables at it (second increase in temp) then finally top up what heat is required at the efficient boiler in the house?

Should make a considerable saving on emissions.


In general no.
Most of the demand on a domestic boiler is for space heating via hot water radiators. The boiler is thus heating water returned from the radiators at about 50 to 70 degrees.
Indirect hot water systems are somewhat similar in that the return from the coil and back into the boiler is usually at least warm.

On demand water heating via combi boiler does start with cold water, and in theory this could be pre-heated by alternative means, but it is doubtful if the savings would justify the costs and complications.

District heating schemes do exist but are generally hated by the users who are generally convinced that they represent poor value for money.
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stumuz1



Joined: 07 Jun 2016
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Location: Anglesey

PostPosted: Fri Mar 15, 2019 6:35 pm    Post subject: Reply with quote

Thanks Adam
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kenneal - lagger
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PostPosted: Fri Mar 15, 2019 7:35 pm    Post subject: Reply with quote

District heating systems run in conjunction with heat producing industrial processes would be a good idea even if heat pumps or wood chip boilers were used to boost/maintain the temperature of the system.

There is no reason why a properly run DHS should give a different level of service to a home boiler system. As long as the temperature in the distribution network is maintained the customer should not notice any difference to a home boiler supply.

I've been looking at a DHS to provide the winter hot water in the ecovillage that I am designing. The houses will only need a few kWs each so fitting a boiler in each house would be a waste of money. It would be powered by the waste heat from generators and a commercial wood burning boiler. Any heating could be supplied by a wood burning cooker.
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adam2
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PostPosted: Fri Mar 15, 2019 8:02 pm    Post subject: Reply with quote

Whilst district heating has its merits, a number of factors conspire to make it less attractive than in the past.

Firstly, if new homes are built to the standards being suggested, then the heating demand will be so low as to render district heating no longer worthwhile.

Secondly, from where is the heat to be obtained ? Few modern industrial processes produce enough waste heat and at a high enough temperature to be worthwhile.
Modern power stations produce waste heat at very low temperatures, Possibly worthwhile for heated glasshouses, a heated swimming pool, or low temperature evaporators to produce drinking water from seawater.
But too low for domestic heating.
And of course electricity production is increasingly from renewables, so a gas burning power station that is shut down in high winds and of limited use for heating.

Finally, costs. Most users of existing district heating schemes feel that it should be free, or at the very worst based on an "ability to pay basis" rather than on an "amount used basis"
Most such schemes use large modern gas boilers in a central location, and are probably no more efficient than a domestic boiler, less so after losses in distribution of the hot water.
Centrally produced heating that is free or included in the rent or service charge does not encourage prudent or moderate use.
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vtsnowedin



Joined: 07 Jan 2011
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Location: New England ,Chelsea Vermont

PostPosted: Fri Mar 15, 2019 8:02 pm    Post subject: Reply with quote

Is there such a thing as a hot water meter that records both volume and temperature delivered so that hot water could be billed by the MBTUs? It wouldn't be too popular in a household full of teenage women but would settle who owes what on the fuel bill.
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adam2
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PostPosted: Fri Mar 15, 2019 8:10 pm    Post subject: Reply with quote

vtsnowedin wrote:
Is there such a thing as a hot water meter that records both volume and temperature delivered so that hot water could be billed by the MBTUs? It wouldn't be too popular in a household full of teenage women but would settle who owes what on the fuel bill.


Yes, I have installed many of them in shared office buildings. They have a poor record of accuracy and reliability if compared to gas or electricity meters.
They consist of a flow meter and two temperature sensors, one for the flow and one for the return (for space heating or large domestic hot water systems) or a single temperature meter for small scale domestic hot water.

Also used to meter chilled water for central air conditioning.

Almost every tenant in an office building thus served is convinced that they are paying a grossly excessive amount for what they get.
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vtsnowedin



Joined: 07 Jan 2011
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Location: New England ,Chelsea Vermont

PostPosted: Fri Mar 15, 2019 8:25 pm    Post subject: Reply with quote

adam2 wrote:


Almost every tenant in an office building thus served is convinced that they are paying a grossly excessive amount for what they get.

Probably a reflection on human nature more then a accurate assessment of the meters reliability.
Some stores here have a procedure when paying by debit or credit card where the machine asks you if the price is OK? If you think it is $20 too much and hit no you go back to square one and have to start over. I've pointed out to the young whippersnapper clerks that to my seasoned mind every price today is way too high and is definitely not OK ,and they should not keep bringing it up. They seldom get my point. Wink
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