My second post emphasised how important it is to understand how the heat pump “magics” heat from nowhere. It is a bit abstract but, hey, it works! Of course the bigger message was that big heat pumps behave differently from little-uns. The project shown in the link above delivers heat at 90°C from a fjord with a delivery ratio (or COP) of over 3.0. We get 3 x the heat out as electricity goes in...’cos the rest is sucked out the fjord.
So my third blog post got me thinking about that and I realised my foundation analogy had to be ”Four Weddings and a Funeral”: a classic Hugh Grant "rom-com" where he meanders through life missing a golden opportunity whilst everyone else strikes the “love jackpot” (apart from the poor bloke who dies).
Big hair, big shoulder pads it even had the big classic smoozy song sung in this case by Wet Wet Wet: “Love is All Around”.
Wet Wet Wet
Sorry to disappoint that it isn’t terribly complex. However let’s put some numbers on it...
The River Thames has a flow rate of approx 200m3/s and is rarely below 5°C. Taking even just a tiny portion of this say 5% and cooling it by 2 degrees would deliver 84MW of heat to the heat pump which in turn would deliver 1.5x this, as heat at anywhere from 60°C to 90°C depending how well the buildings and network were designed > 120MW. Enough to heat all of Westminster and every council tower block in London I suspect...from 5% of the Thames. The key observation back from blog#2 is that this needed be constrained at 45°C like the little ickle heatpumps in Kingston Upon Thames (that also happen to be filled with HFC...but that’s another story).
Or what about a sewage treatment plant with only 2000 l/s flow at 10°C being discharged into the river? Yup, cool it down by 10 degrees and you have another 84MW of heat...
Or what about a power station? Well they each dump more heat than electricity produced so they have typically 1GW of waste heat.
On a lesser scale, what about big bore holes? I don’t mean little holes with plastic pipe that struggle to lift 10kW out the ground, but proper Yorkie-bar-esque open loops. London and much of the country sits atop a moving puddle of aquifers. We don’t get anything like as much as from a river but even 20 l/s from one borehole cooled by 7° is close to 600kW extracted and therefore around 900kW delivered heat at over 70°C.
There are other sources such as air source but as much as they have some merit on a small scale, we’re going to struggle to get hundreds of kW from these when it is really cold and still deliver at high enough temperatures.
Heat is all around
It’s got to be ABBA.