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

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  • zeupater
    zeupater Posts: 5,357 Forumite
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    Hi

    Raining, Dull and currently 14C outside (9.3C low overnight) .... is it really summer ? .... Anyway, best conditions for a 'single room' test for the heat-pump so far, so .....

    Baseload, TV, laptop etc being covered by PV, plus steady background heating to one room (closed off) which is currently 21.6C (and rising) and we're using .... (wait for it) ... 300W most of the time, occasionally peaking at 430/480W as appliances & pumps cycle ....

    Since starting writing this it's brightened up a little ... currently generating 624W, of which a total of 1150W is going into the house as self-consumption, which still leaves >50% (324W) of generation as being exported ..... (isn't logic wonderful ;))

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • Martyn1981
    Martyn1981 Posts: 14,840 Forumite
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    zeupater wrote: »
    currently generating 624W, of which a total of 1150W is going into the house as self-consumption, which still leaves >50% (324W) of generation as being exported ..... (isn't logic wonderful ;))

    HTH
    Z

    Reminds me of a friendly discussion in New Scientist, which was rubbishing the over unity claims of some 'miracle' devices that claim to produce more than 100% of the energy input, often appearing on the internet.

    However, they did note that heat pumps could, technically be classed as 300%, 400% etc efficient ....... technically! But they were careful to differentiate between producing energy, and relocating energy.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW). Two A2A units for cleaner heating.

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • ASavvyBuyer
    ASavvyBuyer Posts: 1,737 Forumite
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    edited 10 September 2016 at 11:57AM
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    Martyn1981 wrote: »
    Hiya Z, loads of questions, so thanks for all the data so far, but I'll limit my start to - what is a short tube-run?

    My preferred location for the two units would be approx 3m apart, plus a ceiling to floor drop of about 2m more?

    I'd hope to position the outside unit under my PV canopy on the ESE wall. That way it should get some shading during the summer (cooling), but some direct sunlight in the shoulder months (heating).

    May I ask what unit you went for so I can start revising some specs, and get back into this.

    Thanks.

    Mart.

    Hi Z

    From reading through your posts about using a heat pump/air conditioner for heating during the shoulder months, it has also got me interested in looking into whether it would be economical to invest in the same to make better use of any spare power from our solar panels.

    I see that you went for a model from the Toshiba Daiseikai 8 range; which model was it?

    I understand it does not need planning permission as it is permitted development; but did you need to get Building Regs approval?

    Also, what was the approximate cost, including installation?

    Many thanks for the inspiration.
  • Martyn1981
    Martyn1981 Posts: 14,840 Forumite
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    Last week I filled a folder with local web-sites, and will have another crack at this, when temps drop and hopefully the A/C guys get quiet.

    Last time, nobody was really interested, no calls back, but this time round I've noticed that most of the web-sites are 'selling' the idea of a unit for conservatories (heat in the winter, cooling in the summer) whilst avoiding the cost of extending the plumbing. Since the idea on here is basically the same as they are promoting, I can't see how they can't be interested this time.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW). Two A2A units for cleaner heating.

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • zeupater
    zeupater Posts: 5,357 Forumite
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    edited 10 September 2016 at 11:22PM
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    Hi Z

    From reading through your posts about using a heat pump/air conditioner for heating during the shoulder months, it has also got me interested in looking into whether it would be economical to invest in the same to make better use of any spare power from our solar panels.

    I see that you went for a model from the Toshiba Daiseikai 8 range; which model was it?

    I understand it does not need planning permission as it is permitted development; but did you need to get Building Regs approval?

    Also, what was the approximate cost, including installation?

    Many thanks for the inspiration.
    Hi

    With the ambient temperature being in the low/mid teens (C) today the system's actually been ticking away nicely. It's currently 22.7C in the main sitting/living areas and 12.0C outside, so as long as we keep on topping-up the thermal mass it looks like the system will perform as expected ....

    On the economics side, as previously mentioned - the system might pay for itself (comparison is to burning log supplies which cost us similar/less than typical gas) if temperatures in the house were maintained at previous years' levels, but we'll almost certainly be tweaking the average house temperature up a little - it's human nature. It sounds silly, but it's totally logical to expect comfort levels to rise whilst heat provision costs fall so some may want to measure the economics on heat provision - however, I'm minded to play fair and just consider the reduction in fuel purchases as 'comfort' needs a pretty subjective approach.

    After looking into various manufacturer offerings it became apparent that the Daiseikai 8 range became the obvious benchmark for comparison when combining with a domestic-scale pv system for shoulder month usage. The system both needs to be able to provide a reasonable amount of heat when necessary (initial raising of room temperature) and then operate at a very low background level so as to operate around/below the poor levels of pv generation on cloudy days. Having had experience in using pv in conjunction with a small oil-filled radiator(400/800/1100W) to provide some shoulder-month heat for a number of years it's really obvious that expecting to do so at even the lowest level (400W) is often pretty ambitious, so the decision's pretty easy ... the lower the continuous power operating level, the better ... it's also useful to note that with most manufacturers, the smallest unit in the range normally achieves the highest COP (efficiency) ...

    Taking the above into account, a spec started to formulate starting with limiting power consumption, then efficiency followed by performance operating range (high/low) and controllability ... and of course, cost - but we still kept bouncing back to the Toshiba units .... so, for us, in a choice between the 10, 12, or 16 models the smallest model provides the best functional fit with 4kWp of PV at the time of year that we want to use it and for what we want to use it for, although the cost differential to the larger models is almost proportionally insignificant .... so ours is the Daiseikai 8 model RAS-10G2KVP-E ...

    Costs ? ... well, our installation would be as simple as it could possibly get (effectively ground floor through wall with power within a few inches) but we still had a number of silly prices (which have been mentioned in other threads) and a few reasonable/local(ish) ones which clustered between £1400 & £1500 (Incl 5% VAT) then a couple from further afield came in around £1320, but for me the distance raises potential support issues on a relatively low-value installation ... in the end a local company (probably the largest in the area) not only price-matched, but bettered by a fair(ish) margin and included higher spec trunking etc ...

    Since our installation, as a result of the unelected interfering bureaucrats from Brussels having little to do other than meddle with our national affairs and waste vast sums of money, the UK's tax position on energy saving products was due to have been changed by now with the reduced 5% VAT rate removed, but this seems to have been held back in the last budget due to back-bencher pressure linked to the referendum (heads down, don't cause unnecessary upset type of pressure!), but this will be needed to be checked regularly for at least the next couple of years .... so I'd guess that a good price incl VAT at the full 20% would be sub £1450, and with VAT at the lower rate of 5% around £1270(ish), depending on complexity ....

    As for building control, our system connected as a simple fused spur off the existing ring and a socket was already there, so it's pretty simple on that front ... what you would need for BC compliance on your installation depends on location and what's available, but your installer should be able to handle any requirements. There are some restrictions on heat-pumps relative to boundaries etc as well as a limit on the number of units before planning consent is required, but again, your installer should be able to advise ....

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
  • ASavvyBuyer
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    Many thanks Z for the very comprehensive reply. From doing a quick calculation, it looks like it would take over 10 years of gas savings; with the amount we normally use per year halved, to to cover the cost. Therefore, might not be justifiable on a purely financial basis.
    However, still like the idea of getting "free" heat from surpplus electric generation; and as you say, there is the extra "comfort" to consider.
    We also used a low power (500 watt) oil filled radiator last winter when there was enough being generated and use a low power fan to blow warm air in from our conservatory on sunny winter days.
    Once again; many thanks.
  • ASavvyBuyer
    ASavvyBuyer Posts: 1,737 Forumite
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    edited 14 September 2016 at 4:25PM
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    Following the above I contacted a few local companies to get estimates for the cost of supplying and installing the same unit (Toshiba Daiseikai 8 model RAS-10G2KVP-E). Unfortunately, figures so far are about £1,800 !
    A couple of other makes/models have been suggested that work out quite a bit cheaper, but have a slightly lower spec. Panasonic RE9 fully installed for just over £1k and Toshiba Mirai for about £1,250. Both have SCOP for heating of at least 4 and have minimum settings using below 250watts. Still doing further research to see what is possible and whether it is viable.

    However, I have been working out some figures for running costs/gas savings. Not sure if the logic is right here, so would welcome your thoughts.
    Currently, our gas supplier charges us 2.35p per kWh. Electricity is 10.91p per kWh. Therefore, our electricity is 4.64 times more expensive than gas. However, efficiency of gas boiler is likely to be about 80% and gas fire about 50%. Therefore, when using the gas boiler we need to use 5kWh for the equivalent of 4kWh of electric heating. For the gas fire the difference would be 2kWh of gas for every 1kWh of electric heating.
    If we were using an air conditioner with a SCOP of 4 or above for heating, it appears that it would be cheaper than using gas for the equivalent amount of heat produced (multiplying 1kW of electricity to produce 4kW of heat) even if we had to pay for all the electricity consumed. However, by using any spare power from the solar panels; it would make it cheaper or even free. Is there something wrong in the calculations/logic?
  • Martyn1981
    Martyn1981 Posts: 14,840 Forumite
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    I think your logic looks right, I've been working on similar.

    The other benefit I see, is not having to worry so much about matching the oil rad to generation. If the HP is working out roughly the same as gas, then worst case scenario it's breaking even, so on a cloudy day when generation is bouncing a bit, the HP will still be fine whether some or all of the leccy is coming from the PV.

    For myself, with shallow E/W PV I don't expect to use it much at all in the very worst months, but for yourself and others, you may want to consider the reduced COP during the colder months in your calcs, or at least be more careful not to run it when spare generation is too low.

    Mart.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW). Two A2A units for cleaner heating.

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • tunnel
    tunnel Posts: 2,588 Forumite
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    However, by using any spare power from the solar panels; it would make it cheaper or even free. Is there something wrong in the calculations/logic?
    Your missing one major point.....how much is a good nights sleep worth when we get a heatwave(uncommon I know)?
    There's been a good few days this year I've had the aircon on all day(for free) and had to get under the duvet at night to keep warm while all the neighbours have their windows wide open trying to keep cool...for me...that's priceless
    2 kWp SEbE , 2kWp SSW & 2.5kWp NWbW.....in sunny North Derbyshire17.7kWh Givenergy battery added(for the power hungry kids)
  • zeupater
    zeupater Posts: 5,357 Forumite
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    Following the above I contacted a few local companies to get estimates for the cost of supplying and installing the same unit (Toshiba Daiseikai 8 model RAS-10G2KVP-E). Unfortunately, figures so far are about £1,800 ! ....
    Hi

    Keep at it, they'll either move their price or you can always go elsewhere! .... you know what it can cost and they obviously do too, but it's your money in your pocket so if they want to get their hands on it they'll need to be realistic on their installation costs ...

    Is the £1800 before VAT, based on 20% VAT or at the reduced 5% rate? .... when looking into systems I was amazed at the (supposed) lack of awareness of the existence of the domestic energy saving 5% rate, so always ask and don't assume .... anyway, research, ask questions and then research more ... if you're talking on the telephone and have a simple installation with power nearby (like ours) let them know that it's simple or they'll load any 'estimated' costs to cover themselves. Never take any notice of an 'estimate', you'll need a firm quote - get them around, explain what you want in terms of equipment and the necessary performance related to pv generation and that it's not really worth you proceeding if the price is above £x .... also, don't discount the guys who quoted £1800 either - just get them around to look at how easy the job is then negotiate ...

    HTH
    Z
    "We are what we repeatedly do, excellence then is not an act, but a habit. " ...... Aristotle
    B)
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