Discussion ... ASHP(Air/Air) with Solar pv ....

Reed_Richards

deantrina said:

expecting PV to power ASHP & expecting costs of approx £30/ M electric . Just had smart meter fitted ( 1 week ago) & its saying im using £13/day on electric ie: £390/Month . ...

I presume you mean an air to water heat pump although this thread is about air to air?  But I could be wrong because if you recently had an air to water heat pump fitted and you wanted to claim the Renewable Heat Incentive then you should have had another electricity meter fitted which monitors just the power consumption of your heat pump so you should have known how much electricity it was using as soon as it was up and running.
As @matelodave showed in graphic detail, the output from your solar panels is in antiphase with the electricity requirements of your heat pump so in summer the PV should power the heat pump with electricity to spare and in winter the PV won't generate nearly enough electricity.
I have used 3760 kWh since 10th December 2020, over 50 kWh per day in the coldest weather.  It is heating a 4 bedroom bungalow occupied just by my partner and myself (so not too much hot water usage).  The hot water tank is maintained at 50 C and the radiators were sized for 50 C flow and 45 C return.  Target room temperature is 21 C in the evenings with set-back at night and 20 C during daylight.
In the last week my greatest electricity consumption in a day was 36.5 kWh but I have been running with a target output water flow temperature of 40 C (instead of the 50 C default) which means that the transition from 20 C to 21 C takes over 3 hours to achieve.    

matelodave

Although I said my annual average consumption for the whole house is around 7200kwh, some 5000kwh are used between November and March and only 2200kwh in the other seven months. Although you need to keep an eye out to optimise your consumption it has to be taken into context with the whole year rather than just in a short period in the middle of winter.

Have a shufti through this thread to get some thoughts on heatpumps (lots more than on here and focussed on Air-Water rather than Air-Air) - https://forums.moneysavingexpert.com/discussion/1464827/updated-air-source-heat-pumps-air-con-full-info-guide-is-it-cheaper-to-run-than-mains-gas#latest

Setting them up and using them to their best advantage is a bit of a black art and can involve a fair bit of tweaking so it's worthwhile getting a thorough understanding of how they work

You may also find that a trawl through this might give you a better understanding of solar generation (the installation is in Kent and is around 3kwp. There's about ten years worth of info). Look at the monthly and annual generation pages to get a feel of what you are likely to achieve - http://solar-panels-review.321web.co.uk/index.php.

Hopefully it wont disappoint you too much but you'll see that its your annual yield rather than a short period in winter that's important and so you've got to tray an maximise your solar consumption in the summer rather than hoping that its going to help your heating in the winter.

deantrina

Reed_R - Apologies if this is in the wrong forum but as it sounds like you guys understand my question i will be cheeky & carry on ,my system is air to water (will hunt out correct forum next) , thanks for above .

deantrina

Matelodave: 
I've got an 11kw heatpump which runs most of the time (we are at home all day) and we got through around 1400kwh in January and 1050kwh in February (this was a bit more than usual because it's been colder than usual - 1150 & 960) but around the sort of consumption that I'd expect for this time of year. (MINE IS NOW SAYING 641KW USED FROM 25TH FEB - 6TH MAR IE: 71KW/DAY DOUBLE WHAT YOU FEB USAGE IS )
In fact this is what my consumption has been over the past ten years. You can see how this January has used a lot more than most previous years. I haven't added Feb yet but it was around 1050kwh. My annual average is around 7200kwh
This is how a solar array would perform where I live in the East of England (the predictions are for a 1kwhp array, so multiply it by whatever size you've got )but you see that it doesn't do much to help run a heatpump until March or April and it drops off around October. (MY PV INFO SHOWS 2.56KWP SYSTEM ,8 EURENER 320w  PANELS & SOUTH FACING). 

APPRECIATE YOUR FEEDBACK / COMEMNTS .
PS - HAD INSTALLATION COMAPNY BACK YESTERDAY & HE SAID BILLS ARE WAY TO HIGH & THINKS IT COULD BE DUE TO THE PUMP BEING TO SMALL SO IS WORKING TO HARD . HE IS SUGGESTING TO HES COMPANY THE PUMP IS UNGRADED TO A 14KW ECODAN ZUBADAN , IF THAT HELPS .

Reed_Richards

I am sceptical about the pump upgrade.  If your heat pump is not powerful enough the main symptoms should be that your house is too cold in cold weather and very slow to heat after the heating is off or set-back.  It won't cost you more in electricity, you'll just be a bit cold sometimes.  But perhaps you overrode the default settings when your house was too cold and did not change it back later which is why you are now using more electricity than expected.  You should have an MCS certificate which says what flow temperature your heat pump is designed to provide.  What does your MCS certificate say?  Is that what you are actually using?  

You should also have a detailed evaluation of the heat loss and radiator requirements for each room and your hot water heating requirement.  The easiest way to use a lot more electricity than was expected is to use a lot more hot water than was anticipated; the evaluation should give your anticipated usage so check if that seems correct.              

matelodave

I'd second that - an oversized heatpump will just short cycle you need enough flow and heat emitters to dissipate the heat that it's producing so I'd be inclined to turn down the flow temperature and just let it run longer. I turned mine down until it was not quite enough and then just increased it by a degree every couple of days until I was satisfied

An analogy is like driving a car. take it steady and you get better MPG than if you drive at high speed or in short bursts, it might take a bit longer to complete the journey but the fuel savings can be quite dramatic. I can get 60mpg at a constant 50mph but it drops to only around 40mpg when driven at 80mph (it's even worse with a caravan in tow). I tend to drive at the speed limit  (as 50 on the motorway is boring) so get an average of around 48-50mpg.

ASavvyBuyer

Decarbonization options for households in the European Union in 2050.

The analysis finds that air-source heat pumps are the most cost-effective residential heating technology in 2050 and are at least 50% lower cost than the hydrogen-only technologies. In a sensitivity analysis, we find that even if natural gas costs were 50% lower or renewable electricity prices were 50% higher in 2050 compared to our central assumptions, heat pumps would still be more cost-effective than hydrogen boilers or fuel cells.

matelodave

You have to take into account what their "central assumptions" are predicting for 30 years hence. Did you read the whole paper or are just quoting the headline in typical Daily Mail fashion

It appears that by just reading that bald statement, they could be predicting that the price of gas is going to be extremely high and  leccy will be everso cheap but even then they can't make a case for hydrogen or fuel cells.

Just my take on a headline rather than reading through it all. 

ASavvyBuyer

matelodave said:

You have to take into account what their "central assumptions" are predicting for 30 years hence. Did you read the whole paper or are just quoting the headline in typical Daily Mail fashion

It appears that by just reading that bald statement, they could be predicting that the price of gas is going to be extremely high and  leccy will be everso cheap but even then they can't make a case for hydrogen or fuel cells.

Just my take on a headline rather than reading through it all. 

I could not see the "actual" figures they were using, but apparently they were based on other studies predicting the future prices of energy. Those figures may be in the reference documents.

I understand that is why they did the "sensitivity" analysis to see what the results would be if those predictions were 50% out.

matelodave

so its really just a pointless attention seeking headline with no substance. Not sure why you posted it