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James_N
Rank 6
August 12, 2021

Solar PV panels, iboost (PV diverter) and an air source heat pump (ASHP) is it cost effective?

  • August 12, 2021
  • 14 replies
  • 4064 views

Hi all,

 

Just starting the process of getting solar installed (ie getting quotes). I’m sure i will have more questions on this to come, but here is my first.

There is a product called iboost that takes excess electricity you are creating from PV, which is going back into the grid, and uses it / some of it to create hot water via the immersion.

The question is, as I now have a ASHP, is this of any use? My thinking on this is that if I had 2kWh of ‘spare’electricity from PV, then via the immersion I get roughly 2kWh of heat. But (assuming a HW COP of 2) it would only take 1kWh of electric to do the same via the heat pump. That leaves 1kWh spare which I might get paid 5p for, or at least someone else can use as green energy.

The only thing I can think is that the ASHP is only heating up to 50 degrees. The immersion could push that up to say 65 degrees. This has two benefits i think. 1) the legionella setting does this every 7 days, so I might be able to turn that off (maybe) and be using PV to power it. 2) if the water is 65 degrees then it would take longer to cool down to need reheating, therefore saving using the heat pump.

 

Overall not convinced the iboost is of value with a heat pump, but would value a more informed view

Any other general tips on ASHP plus Solar?

 

Thanks

 

James

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    Transparent
    Rank 20
    Transparent
    Rank 20
    September 7, 2021

    I’ve spent 5-mins this morning to find the following three parts on Amazon UK. So this will give others an idea of likely costs and how readily available these items are:

     

     

    A ‘stack’ of 16 such Lithium cells would have a capacity  of 13.4kWh - the same as a Tesla Powerwall, but with much greater lifetime due to the cell chemistry.

    Save energy... recycle electrons!
      Tim_OVO
      OVO Staff
      Tim_OVO
      OVO Forum Legend
      September 8, 2021

      @Heatherd I’m tagging you in this thread as you may be well placed to advise. Without giving too much away, there’s some similar tech involved here...

      Carbon neutral - we need a community to get there! My green tech: Aclara SGM 1411-B smart meter, Chameleon IHD6
      H
      Newcomer
      Heatherd
      Newcomer
      September 9, 2021

      I have 16 panels on my roof enphase invertors under each one. they in turn provide electric to the house. then store in 4 enphase batteries. I also have an ASHP-diakin altherma. this supplements the heating at 50% so far. I do not have a heat store for my water with immersion in it. I use the boiler for that. My gas bill in the summer is low. bills are 30% below a house same size as mine. 

       

      ASHP does not perform as well as i would like but after 5 years it is getting better. 75% eco will be set at next service to try and get a better savings. but it will use 1kw for every 3.5kw it produces. thus only set at 50%eco.

        Transparent
        Rank 20
        Transparent
        Rank 20
        September 9, 2021

        Thanks @Heatherd - that COP of 3.5 from an Air-source Heat pump is extraordinarily high. Participants on the current OVO-led Zero Carbon Heating Trial are struggling to get anywhere near 3.

        Our current understanding is that COP readings above 3 are usually only attainable by Ground-source Heat pumps.

        Save energy... recycle electrons!
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