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

My wall mounted aircon unit uses about 1.2/3kWh per hour. I would consider swapping it for an updated version as with all technologies they're advancing very quickly.

Maybe its also time for me to look at getting around to purchasing a Wattson to compliment things as most of these systems are plug and play types. At least then I wouldn't be using any more power than I was generating.

They're probably going to be a better option than oil fired heaters. At least these units will use 1kWh and turn it into 3-4kWh of heat. I can honestly say I haven't looked into portable units so probably should do a little more research(skulks off to do a bit more net nerding)

@ Zeup and Tunnel, many thanks for the info and comments from the other thread. TBH, I was a little shocked that my slightly odd idea was considered even remotely rational, not that that has stopped me before (PV @ WNW!!!!!!).

So to keep things contained, here's what I pondered:

Martyn1981 wrote: »

So it seems my idea is very, very marginal, and that is to kill two birds with one stone. Get the luxury of AC, with 'free' leccy (or approx 3.3p kWh leccy) and also get top up heating in the marginal months Mch/Apr & Sept/Oct, when external temp should/might give a COP of 3, heating demand will be low, and 'free' leccy (PV) should be available (lowest Oct 227kWhs - highest Apr 509kWhs).

I currently support my marginal heating with leccy heating of between 240W to 640W in those months, to keep the chill off 2 rooms, either between GCH heating, or instead of on sunny days as solar gain heats up the house. So the thought of possibly tripling the efficiency is interesting, but I'm sceptical of whether that COP is achievable, and whether a split system, even one supplying 2 rooms, would have enough effect on the house in general.

Also the cost would have to be nearer £1k and that might be asking too much (way too much?).

But if possible, and saves around £60 to £80pa, plus provides more efficient heating, and provides some AC luxury, then it might be worth me nerding this a little further before giving it up as a bad idea. Hmmmm!

Mart.

T - your link:

http://ecoairdirect.com/split-air-conditioning/bravo-non-inverter/inverter-air-conditioning-12000btu-bravo-inverter-eco1216sd.html

is pretty much what I was considering. Thanks very much for the link, I didn't realise how possible this actually was.

Ideally need a compressor that will run 2 units, but luckily they would be two rooms above/below each other, so roughly same pipe run. Also, having experienced what a small amount of heating can do in marginal/shoulder months, I'm reasonably confident that 3+kW's of heating (or indeed cooling) would have a noticeable effect.

Zeup, I'm a pretty positive person, and willing to give things a go, but feel a little sceptical about the COP figures I've read. Is a COP of 3+ for temps of 7C+ reasonable? I really don't know much about this at all, only at toe dipping stage so far.

Following on from COP - another thought, that has led me here, is that a COP of 3 (or more) 'balances' leccy v's gas costs. So whilst I would expect some or all leccy from PV, it would not be a disaster if I failed to keep an eye on pesky clouds etc. Ok, not a disaster on running costs, but still a disaster in duplication of heating systems, but that gets balanced out by having AC as a luxury, and definitely 'free' leccy.

Lastly, whilst this is only a personal issue, I have approx 700kWh's of PV to spare (export about 2,800, get paid for 2,100) so no guilt felt, if that is turned into 2,000+kWh's of heat.

2nd last. Shortly after mentioning this a week or so back, the Jeremy Vine show ran a piece on AC. Didn't catch much of it as I was transistioning (gyming, showering, cycling) but little snippets all mentioned 'efficient heating as a bonus'.

So, whose going to jump first, and get some quotes for an installed system - should we wait till December when the companies are quiet?

Mart.

zeupater wrote: »

. As can be seen, there are plenty of days in March/April/Sept/Oct when daytime max temperatures of 10C-15C should be lifting the COP above the 7C standardardised performance test.

For modern top-of-the-line heatpumps - there is little difference between 15/7/0C.
The heat output goes down somewhat, but the efficiency stays over around 5.

I question the sense of using a low-efficiency heatpump - while they may be around half the price, they use lots more electricity for a given heat output.

zeupater wrote: »

Hi Mart

My thoughts on this are based on only running the HP when there is sufficient power being generated by the pv system in Spring & Autumn ... that really means that the ambient temperature whilst operating should be considerably higher than 7C.

A secondary consideration which would influence the COP would be the house's interior temperature, however, it's likely that anyone interested in a pv/HP combination wouldn't be looking to achieve tropical indoor temperatures ...

HTH
Z

Hiya, 100% spot on what I had in mind. To try to keep the house heat above 18C (ideally 19 to 20C) when temps outside are probably 10C to 15C during the day (PV window).

Tried to dip a second toe in, not so easy. Just had a chat with a company about 1/2 mile away, really helpful, but when they asked the application and I said 1 or 2 rooms in the house, they said they don't do domestic installs anymore as people's expectations are too high.

He said I (we?) were pretty spot on, with expectations for a small system, perhaps 4 months questionable/too cold if GCH available, 4 months very suitable, and 4 months no heating needed but AC a nice luxury. But still didn't want to know. Has given me another company details, and waiting for call back from a third, but they did say that they are busy and priority to commercial jobs at the moment - which was pretty honest of them.

Critically, I need to know what those £400/£500 internet supply only prices turn into, when they look around the house and start sucking air through their teeth!

Another question, you know we were talking about boiler efficiencies for DHW of around 80%, what would that be for heating as some losses (pipework, boiler) would still be beneficial. So would 90% be a fair figure when comparing gas to leccy? Taking that a step further, if a COP of 3.6 could be achieved, would that mean 1kWh of leccy replacing 4kWhs of gas (4*90%), or am I not understanding this correctly?

Cheers.

Mart.