Soldato
- Joined
- 21 Sep 2020
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- 3,371
Along with battery storage.
Heat pumps vs Gas boiler ?
- Thread starter jonneymendoza
- Start date
All adds up right but good luck using solar panels in god old british weather lol
Soldato
Totally overcast, still seeing 253.3 W/m2 solar irradiance hitting the panels.
Probably an argument to just put on more panels and skip the heat pump cost then. Plus you can sell some back to the grid when it makes sense
Soldato
- Joined
- 19 Jan 2006
- Posts
- 4,531
Indeed! Also a complete myth that solar panels need heat to perform.
And do what with it, power an electric boiler @ 1:1 efficiency?
Yes. Why not. It’s a viable option when you consider the investment costs and ability to have no electric costs going forward rather than still buying electricity from the grid. Maybe 3x more solar is a better option than a heat pump. All green and silent with the benefit of selling excess back to the grid.
There is no right answer but options to consider. You cant charge a car with a Heat pump either
There is no right answer but options to consider. You cant charge a car with a Heat pump either
Close to 100% efficient but not quite.
So roughly what usable wattage do you get per panel on an average day?
I'm thinking of starting with 2 panels.
Soldato
Immersion heaters are **** though. They have poor controls and a tiny surface area. Electric boilers are almost 100% efficient.
I love these heat pump threads. One thing everyone should bear in mind is that heat pumps typically only supply water up to about 55C. Most heating systems in the UK need 80C.
You don't actually need heating this time of year though. I haven't used my heating in two months or more.
Soldato
Heat pump also does the water.
Don
Eh? My ASHP can supply more than 55C (I think my Target flow temperature is set to 60C).
Also why would my heating system need 80C?
Soldato
Well yes and no, all devices that heat on demand right now apart from heat pumps/ac type units are all in effect 1:1 devices, immersions, instant boil taps, showers etc etc
An immersion is 100% efficient as is a kettle, an electric shower etc
My immersion is like 3kwh (its a backup) it could be with the correct cable and switches 20kwh.
Same with a kettle they are 3kwh since thats the max they can pull from a socket, Ive seen instant hot water heaters that are 6kwh, and as I said a shower is in effect no different its just a heating element.
You don't need to have poor controls thats just whats installed typically. You could have very sophisticated controls if you wanted them, the heating element just has an on off switch (make contact to allow energy to flow), what chooses when to do that and to what extent etc is completely irrelevant to the fact that anything that heats water directly at 1:1 is going to be expensive to run!
Soldato
Soldato
They can, but not very efficiently. 60C is more likely the limit. But if you could drop that to, say, 35C flow, your COP would jump up enormously. Not that 35C is practical, but weather compensation at least allows you to have a variable flow temperature and therefore a variable COP (SCOP).
Old heating systems were often designed for 80/60C because there wasn't enough heat transfer, so flow temperature was high. It's just that techonology has massively improved so flow tempreatures have reduced. Also, if you have 80C stored water then you don't need to worry about legionnaires. But, a lot of modern systems don't have stored hot water and generate it on demand (like a combie boiler) so you don't need to pasteurise your stored hot water.
Your immersion heater may be 100% efficiency in heat generation, but not in heat transfer. No way will you get your 3 kWh of heat out of it unless you've spent time fixing it.
If the flow rate is too high then there may not be enough heat transfer. So you may be heating your water up to 70C to heat the water in your cylinder, but if the water moves too quickly through the coil, it may leave the vessel at 68C for example. That's deeply inefficient. Or, the temperature in the cylinder is equal to the temperature in the coil (i.e. you've reached your set point temperature) bt the heater still pushes water through unecessarily.
Whats a 3kWh heater?
Efficiency is conversion of energy to its use(heat), it's not about heat transfer. Not sure what you are on about with pumping, an immersion heater simply sits, immersed, in water within the tank. Im confused about what you are talking about to be honest if we are talking about a hot water tank with stored hot water. Its not an inline heater.
Efficiency is conversion of energy to its use(heat), it's not about heat transfer. Not sure what you are on about with pumping, an immersion heater simply sits, immersed, in water within the tank. Im confused about what you are talking about to be honest if we are talking about a hot water tank with stored hot water. Its not an inline heater.
Soldato
Not my specialist subject, but I found this video interesting.
Particularly where he's talking about outside temperature and the effectiveness of the heating system.
Particularly where he's talking about outside temperature and the effectiveness of the heating system.