Wet Wet Wet

Published by Brian Coyle on

wet window

So blog#1 observed our society’s fascination with burning stuff like Cavemen to produce heat. In reality big heatpumps like this one:

can deliver heat from numerous sources up to 90C and still be more cost effective than gas………..and qualify for the RHI. www.tinyurl.com/large-gshp shows how an entire University could be heated with heat from a river.

Blog#2 emphasised how important it is to understand how the heatpump “magics” heat from no-where. It is a bit abstract but hey it works! Of course the bigger message was that big heatpumps behave differently from little-uns. The project shown in the link above delivers heat at 90C 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 blog#3 got me thinking about that and I realised my foundation analogy had to be ”4 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 WetWetWet “Love is All around”.

So how how on earth is that having anything to do with big heatpumps. Well aside from being massively simple and easy to join in with (ala karaoke) melodic cheese-pop, it’s really simple. Wet Wet Wet is all we are looking for with big heatpumps. And that really is “all around”. Water. If it ain’t frozen you can easily take heat out it.

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 5C. Taking even just a tiny portion of this  say 5% and cooling it by 2 degrees would deliver 84MW of heat to the heatpump which in turn would deliver 1.5x this as heat at anywhere from 60C to 90C 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 45C 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 10C being discharged into the river. Yup. Cool it down by 10 degrees and you have another 84MW of heat………

Of what about a power station? Well they each dump more heat than electricity produced so they have typically 1GW of waste heat.

Hey even the London Underground pumps out 30 million litres of water a day worth >22MW of 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 degrees is close to 600kW extracted and therefore around 900kW delivered heat at over 70C.

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.

So to prevent going on as long as Martii Pellow and the Wets did (15 weeks I recall at number 1 and 37 weeks in the top 75), LOVEISALLAROUND let’s just assume that heat is all around us…..and so the feeling grows…….quick pass me the karaoke mic and let’s shout it out that heat doesn’t need fire, heatpumps work best when big and sources of heat are plentiful. Now what about next times inspiration. (don’t worry it isn’t Bryan Adams and Kevin Costner)

It’s got to be ABBA…………………

Categories: SRE Blog