ground source heat pumps

Yes, that answers the question asked - "how much energy per day?"

However, a more useful calculation would be the *rate* of extracting energy (i.e. power) in kW. Have you worked that out?

Yes it does work out the same

Bob

But only if you do extract the water cool it and put it back surely?

Can't you have a closed loop system, like that of a ground source heat pump, dangling in the river with the water naturally flowing past it? I guess you'd need some form of grid/channel to keep it clear of weed/branches etc which the EA might then consider "abstraction"... B-(

Unfortunately the pumped concept falls at several hurdles.

More than 4.84kW is needed. Although river Lea water is *warm* (largely sourced from effluent treatment plants upstream) 5deg.C seems a realistic figure considering prolonged adverse winter weather.

The EA website gives abstraction charges of 15 to 28ukp per 1000m3 and trade effluent discharges are charged on anything exceeding 10m3 per day so it looks as if the project is doomed!

However, by cleaning out an existing drain paralleling the river bank, I can probably create a flow which would improve the performance of the slinky version. I am beginning to think that gas is best!

regards

This idiot built his own house and put single glazing in. He hasn't a clue. Sad but true.

You never use actual water from a river in a heatpump..its merely a heat exchanger.

I guess you'd need some form of grid/channel to keep it

Not even that. You simply throw some coils 9figurateviely speaking) in te river bottom. and let them silt up and over.

Grund or water source heatpumps extract so little over such a large area that perfect conductivity is not an issue.

The working fluid in the primary will exit the heatpump at probably -5C or so. Its merely necessary to get it more or less up to +5C. Then the pump will boost the secondary temperatures to about +30 - +40C and chill the primary.

Have you calculated exactly what you need to maintain 19C on a cold winter day? As well as heat from the river you can also collect a bit more from the pipe run from house to river, plus additional insulation may sometimes be an option, plus other heat sources.

Do you actually know the winter river temp? It might be better.

NT

Which 200m2 are you heating, at the floor or at the ceiling or somewhere in between?

MBQ

Don't forget that your calculated total heat requirement doesn't have to all come from one source. Yer average a working PC/monitor chucks out 100W or so, humans another couple of hundred watts each just sat still...

considering

I suspect it probably is the north sea surface temperature in mid winter doesn't get down to 5C, 8C is sort of average. It's about 15C ATM... With the river being fed "warm" effluent as well...

And is the absolute temperature all that important? We are dealing with a heat pump. It'll move the heat provided there is a positive delta T between the incoming circulated loop and the water. Obviously efficiency drops off at small delta Ts and if you freeze the water around the slinky. That's where the design is critical have a big enough area over which to extract the heat such that it doesn't freeze or the delta T get too small.

If this is from a river, how fast does it flow, is there a fall across the land?

It might be better to put a turbine in, generate electricity and use that.

He needs a heat exchanger. Pump water from river into heat exchanger. Pump water from heat pump into other side of heat exchanger. Sorted.

If they allow you too, which I doubt they will.

If the building is square, its about 14 meters square.

If its say 3 metres high, the total area external to the world is

say 400 square meters in all.

I've ignored the floor here. If you feel its important add another 200 and make it to 600 sq meters worst case. That will just about cover the 'long thin' building. Presumably UFH is in the frame with a heat pump, so teh floor will be well insulated..

No with a U value of about 1 for reasonable insulation, that's about

However by my reckoning the average person in an office is around 200W of human heat, PCs etc and lighting and about 20 people minimum will be in that office, so its likely to only need around 9KW. Worst case. With about 3:1 upscale on the heat pump, about 3Kw electricity with a good ground source pump.

An idea, but to get a few 10's of kW of electricity you need a good head and a hefty flow. IIRC 3kW of lecky needs a 20m head and 20l/sec flow, if that is available it could drive the heatpump of course...

There is absolutely no doubt that in terms of energy input versus useful house heating out, a heatpump is the no. 1 technology.

The only problems are cost of installation and the heat exchanger.

And of course where the energy comes from, BUT with a heat pump in a typical situation providing about 3:1 uplift in terms of heat output to electrical input, it means that even a 30% efficient power station matches a 90% efficient boiler.

If the electricity is at least partially carbon free (nuclear) then its also a huge carbon reducer.

Likewise, with UFH in winter, you can use off peak electricity when the outside temps are coldest, to get the house up to temperature - a temperature it may well keep (if well insulated and reasonably massive) for the whole day.

I would 100% use it in a new build, if adequate land area or pond volume is available, but its a bitch to retrofit. Air source might work in a small flat installation in urban environments where temperatures are constantly high because of heat leakage from buildings, but its crap in rural locations.

No. Ask me next January. I was using 5deg.C as a starting point to enable ball park figure calculations. 4.8kW is way too low. The hope was to use a *green* heat source as a planning lure. The project requires a change of use consent for agricultural buildings in the green belt.

Maybe.

Quite. I expect the EA will come up with some unaffordable abstract/discharge fees and the project reverts to the multiple slinky model.

regards

In message , "dennis@home" writes

No. uk.business.agriculture kindly did some sums and came up with about

If you use a leat, you fall into the abstraction/discharge pit.

regards

Payback and CO2 reduction isn't huge if it is only displacing natural gas.

All the conversion work here is planned for under floor heating.

regards

Floor. Unfortunately the existing layout leads to rather a lot of external wall:-)

regards