Please help – what renewable heating system would you choose? Snowdon farm dilema

The work on Hafod y llan farm on Snowdon is now moving a pace. This demonstration farm is adding an energy string to its bow.  Paul is managing the efficiency work and  the 10kw PV  is within a couple of weeks of going in. New LED lighting has been ordered. The deposit has been paid on the 640kw hydro turbine. The 15kw hydro is getting ready to go in. The farmhouse is about to get an overhaul. £5000 quote had been received for new secondary glazing. We have been looking at external insulation. Heat recovery units in the bathrooms and kitchen, induction cooker, smart metering and so on. Then we get to the heating system for the large ish 1950’s farmhouse. We have had to slow down and take our time to think this through. The initial dash for air to air heat pumps has had to be looked at because of the higher than expected costs, which when we look at the quote actually makes sense because of the complex use of the building and its general layout. What next and what to consider?

Hafod y Llan farm-house. Otherwise known as Arwyn’s home

One of the objectives for this work is that it has to be value for money, reliable, practical and replicable. One test is would a farmer visiting the farm consider adopting our approach. It’s all too easy chucking money at these things as we have seen at ‘exemplar’ projects but this approach is not replicable to most of us (we don’t have ‘that’ luxury on this project!)

Options being considered

Air to air heat pumps located around the building and heating different zones. Benefit – cost per unit, control-ability and speed of install. Against – cumulatively its is quite expensive. No RHi payments to help with the capital cost, fear that the cooling mode (or air conditioning will be used)

Biomass system – either small pellet or a batch boiling log system. Benefit – can be bolted on to the existing heating system, RHi payments to offset the cost, low operating cost for log system Against – can be very expensive if you got for all the options (auto feed, dishing and full automation) log system involved a lot of wood handling. Pellet can track oil cost increases (takes energy to make and move) they can also take up a bit for room esp. with the biomass store

Ground source heat pump using the field behind the building – Benefit – automated switch on system. RHi payments to help with capital cost, use electricity generated on site Against – quite expensive per KW to install, heat profile (slow release system. The farm manager may be out for most of the day and may not benefit) will need to change the radiators because of the lower flow temperatures (also air to water heat pump, solar thermal, short wave infrared to consider)

something different – using the 15kw of waste heat from the large hydro generator and using an air to water heat pump and moving this hot water to the farm-house. But the hydro will only be generating for 60% of the year and only has a 40% load factor. I personally like this idea but the system has to be replicable in this demonstration farm.

The most important thing to consider is the victim or should we say the person left with the heating system after ‘we’ the clever people have left. We have to make sure that Arwyn the farm manager is able to use this system and that it works for his life style. eg during lambing and the long cold nights and irregular hours the last thing you want to do when you get home is to shift quite a few kilos of logs or empty and ash pan. The client is king on the decision –

let us know what you think? PS Paul and i are going through the same dilemma with our own homes!

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8 Responses to Please help – what renewable heating system would you choose? Snowdon farm dilema

  1. Mike says:

    If you’ve got surplus electricity from the hydro then it sounds like a heat pump is the way to go over biomas. but if the hydro is down at the coldest times then you’ll need a backup, so an alternative that works all year round may be better.
    If you do look at biomass you could consider a CHP option to make even more power, Stirling generators are fairly new to CHP and very efficient too. and would make an ideal showcase.

    A bore hole heat pump can be more effective than a surface ground source especially if you are in a geothermal area (I don’t think Snowdon is though) or an are that suffers from deep frosts.

    as an aside why fear the air-con cooling? if its purely powered by the solar (in hot weather) or hydro there is no argument against a little luxury, being green doesn’t mean living under a rock.

    • Keith Jones says:

      agree we have surplus but not all year. cold dry clear feb when you need the heat menas its grid electricity. one other thing with heat pumps is the type of heat. if you want it efficient its a slow release system rather than the traditional pulsing (morning and evening) and with only one farm manager living in the house who is often out tending the flock or in the office. a lot of of that heat will simply leak out of the house (no mater how hard we hit it with insulation) but my brain still thinks heat pump because even if we cant use the hydro all of the time – we can use it most of the time. But then again it will be down to Arwyn – what does he want as i feel it will be much of a much ness and much better than the £400 a month on oil in winter!!! plus all that lovely carbon it was emitting! thanks for the comment – gets us thinking which is what its all about!

    • Keith Jones says:

      on the air con side. its just the fact that it will be consuming energy. a wasted Kw is a wasted kw no mater how its generated. in terms of cooling i would rather work on shading, insulation and ventilation. air con in Snowdonia is am just wrong. thanks again for getting us thinking

  2. Tim says:

    I think that the answer to your question is entirely dependent on how effective the secondary glazing and additional insulation might be? The appropriate heating system will ultimately depend on how much you can reduce the overall heat loss from the farm house. If the secondary glazing, loft and external insulation is minimal then, I would advise a biomass system as you will need to maintain the high water temperatures to keep the radiators working. If the insulation is quite effective then I would suggest a ground source or air to water heat pump. A heat pump is more efficient when it operates at lower temperatures so if you can reduce the heat loss from the farm house sufficiently then it may be possible to continue using the existing radiators at the lower supply temperature. I also like the idea of using waste heat from the turbine house, however as you say, the intermittence of the turbine would make it difficult to predict the effectiveness of that system.

    Off an oil boiler the existing radiators probably use water at a 80/70 supply/return temperature which is equivalent to a 1.13 radiator output at nominal conditions. At 55/45 the same radiator will deliver 0.46 of its total capacity at nominal conditions. The maximum water temperatures supplied by a heat pump would reduce the existing radiator output to only 40% of their original capacity. The price to replace the existing radiators with a set of new low temperature radiators (including lock shield/TRV fittings) plus labour to install might cost around £350 – £450 per kW. If the building requires 10 kW to keep the house warm on the colder days of winter, then one will need to budget around £4000 to replace the radiators in addition to the cost of the heat pump.

    Alternatively, one could offset the additional cost of replacing the radiators with additional external insulation. Assuming that 40mm of external wall board costs £11 per m2 (inc VAT) then offsetting the cost of replacing the radiators will buy an additional 400m2 of insulation (assuming the house is already getting external insulation then the cost of labour can be excluded). If this additional insulation can reduce the overall building heat loss by enough (60% or more), then a heat pump can simply be dropped in to the existing system. Not an impossible target but it would require some careful thought, planning and detailing. Passivhaus retrofits commonly achieve over a 90% reduction. I would also recommend a small wood burner in the living area in addition to the heat pump system as one can never beat the aesthetics of a fire. One drawback of a heat pump system is that many people expect radiators to be hot and therefore assume the heat pump is not working as they never get past warm.

    With regards on whether to go with a air source or ground source heat pump I would chalk it down entirely to the cost between the two. Air source heat pumps these days can guarantee their output down to -15 or even -20C however they would be quite inefficient at these temperatures. The energy savings trust field trial found the mean system coefficient of performance (sCOP) of an air source heat pump was about 1.8 and for a ground source 2.3. If the additional 30% energy saving can justify the additional cost of a ground source system, then go for it. The best performing ground source system had a sCOP of 3.4 and the best performing air source system had a sCOP of 2.2, I would imagine you would reach these targets!

    • Keith Jones says:

      thanks for the full suggestion. I have installed 30 biomass and 28 heat pumps and agree fully. On the EST report i know it was more down to how they were used and installed. we are trialling three high temp CO2 heat humps and are really pleased with the operating costs. on the radiators we have used Dimplex and Jaga and agree with the costs you state. but have had good results with simple triple rads. we are looking towards 75 – 100mm of external. my other issue with the house is that the occupancy will be really low and so a slow release system might not be suited to how the house is used. I am erring on the side of simple biomass – good experience with the latest stripped back windhager, froling, okofen and so on and the costs are not that astronomical. it now comes down to the user and what does he want to become the victim of. thank you so much for the comment – it makes us think which is what we wanted!

  3. Eli says:

    Heat pump, hands down. Why are you leaning towards the biomass?

    • Keith Jones says:

      thanks for this – distribution system which is sized for much higher temp and flow rates, peak load heating because its a large house with low occupancy, old fabric which would need a lot of spending to bring it up to a level where you would get decent COP’s. Cost for the desired performance.

  4. Pingback: Hafod y Llan farm house – looks like we have a heating strategy | National Trust Going Green

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