Installed in a day? Surely not, unless it's Bodgit & Scarper running the contract. There's way too much to do to most systems to be able to complete an installation in a single day
Heat pumps
- Thread starter Fallout
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I was shocked
If they use green electric, heat pumps are good emissions-wise. But if the electric is from gas (or oil) the efficiency of conversion to electric is similar to the COP of the heat pump, so little if any benefit.
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No, that is a false equivalence.
In 2021 the UK CCGT fleet achieved 49.9% efficiency (below design efficiency because of other factors we won't go into here).
If we use a very easy to achieve COP of 3, which means that for each unit of electrical energy consumed, the heat pump will produce 3 units of heat energy. But since the CCGT plant is only 49.9% efficient, you could say that to generate that one unit of electrical energy, you had to use roughly 2 units of gas energy.
So, effectively, those 2 units of gas energy are producing 3 units of heat energy when run through the heat pump.
On the other hand, burning gas in a boiler at home with an, amazing really, efficiency of 90% means that for every unit of gas energy you use, you get 0.9 units of heat energy.
So, in this example, the heat pump is effectively turning 2 units of gas energy into 3 units of heat, while the home boiler is turning 1 unit of gas energy into 0.9 units of heat.
Therefore, despite the power plant's less-than-perfect efficiency, the heat pump still uses the energy more efficiently than the home gas boiler.
Would usual be an S plan to heat pump installation. Installed in a day. Between 3 plumbers
I don't know where you get 49.9% from, sounds very high to me, and excerpt from Wiki below.
"The energy efficiency of a conventional thermal power station is defined as saleable energy produced as a percent of the heating value of the fuel consumed. A simple cycle gas turbine achieves energy conversion efficiencies from 20 to 35%.[3] Typical coal-based power plants operating at steam pressures of 170 bar and 570 °C run at efficiency of 35 to 38%,[4] with state-of-the-art fossil fuel plants at 46% efficiency.[5] Combined-cycle systems can reach higher values. As with all heat engines, their efficiency is limited, and governed by the laws of thermodynamics."
I don't know what state-of-the-art means in this context, but I wouldn't mind betting it doesn't apply to most electric generated in UK. Then there are transmission losses.
I believe modern boilers are more like 93% efficient (haven't looked up figures lately) but there's nothing amazing about it. Burning fuel in a boiler to produce heat is completely different from producing shaft power hence electricity. It's the 38% from the latter that's impressive!
And at first glance you seem to be comparing 2 units of energy into a power station with 1 into a boiler.
Taking generation efficiency 35% including transmission losses and COP 3, 1 unit of energy gives 0.35*3 = 1.05 from a heat pump, vs perhaps 0.93 from a boiler. Good for the planet if the electric is green, but with fossil fuel not much in it.
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Half a day to properly flush an existing system only leaves you half a day to replace radiators & valves, upgrade & alter pipework, replace cylinder, fill, test & commission
Can imagine they aren't flushing
I looked on that site but can't find anything about generation efficiency. Would you mind pointing me to the relevant place? If 49.9% is the figure, fair enough, but it seems high to me.
Given the UK climate domestic heat pump installs should really be targeting a COP of 5. 3 would be a woeful design and/or install these days.
Everyone needs to keep in mind that the technology is not static and a COP of 3 in 2010 would have been seen alot, but these days things have moved on.
The UK is in a ridiculous situation where our housing stock is bad and simultaneously we didn't bother to fit condensing boilers properly. Your average install is at least 30 years behind the times. MANY people still think 80C flow temps, S-plan and 30kwh combi in a 3 bed is "ok".
Its so bad that manufactures remove modulation control from UK products because its "too complicated" for installers.
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OK thanks
I wouldn't have a combi anyway, but not mainly because of efficiency
I haven't heard of that, I didn't know it was possible, though I've never had a modulating boiler. On here, posters often urge the need for high turndown, but I'm not convinced it makes a noticeable difference.
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