Heating: thermal stores, ASHPs, solar thermal, oh my!

Smiley_Dan

thenudeone wrote: »

Several "high temperature" ASHPs are available (eg Daiken Altherma HT) [...]

If you install before March 2014, HT pumps are still eligible for RHI at a legacy SPF of 2.5. After then, they won't be eligible.

Would that be because they use more electricity?

Smiley_Dan

Martyn1981 wrote: »

[...]I note in this discussion (link attached below) about mixing inputs, a thermal store is also mentioned and this paragraph referencing radiators (as opposed to UFH):

http://www.navitron.org.uk/forum/index.php/topic,21137.0.html

"Ideally you need a buffer tank to separate all the flows, you may get away with a low loss header. This way you can keep the existing rads and depending upon outside temp run then at 35-40-45-50 as required if 50 isn't coping then swap over to the LPG. (With a buffer tank you'd run the rads at Δt10 and the heat pump at Δt5)"

An excellent resource, thanks.

thenudeone

Smiley_Dan wrote: »

Would that be because they use more electricity?

A heat pump extracts heat from the air, ground or water and transfers it to water for heating, by the same technology that extracts heat from food placed in a fridge or freezer and outputs it as waste heat at the back of the appliance.

The energy used by a heat pump is used for pumping and compression. A well-designed and specified heat pump system might provide 3-4 units of heat for 1 unit of energy used, but that would probably be in a heating system designed for using lower temperature heating water.

A heat pump becomes less "efficient" as the temperature increase required becomes higher. A home designed for a heat pump heating system may use water that's only 45-50C, well below typical gas heating system temperatures.

AFAIK, current HT heat pumps can't meet the minimum standard for performance (to receive RHI) which will apply to any installation from April 2014. They can still be installed after then, but they won't get RHI, although the exact terms of RHI still aren't known. I expect that manufacturers will do a bit of tweaking and introduce models which just meet the standard to get RHI but still create high(er) water temperatures which will work okay with standard heating systems and radiators.

Once introduced in April 2014, the RHI payment will apply to any eligible installation since April 2009. It would be unfair to apply 2014 performance standards to early adopters and exclude them from RHI when, at the time of installation, they appeared to be eligible.

Smiley_Dan

thenudeone wrote: »

AFAIK, current HT heat pumps can't meet the minimum standard for performance (to receive RHI) which will apply to any installation from April 2014. They can still be installed after then, but they won't get RHI, although the exact terms of RHI still aren't known. I expect that manufacturers will do a bit of tweaking and introduce models which just meet the standard to get RHI but still create high(er) water temperatures which will work okay with standard heating systems and radiators.

Once introduced in April 2014, the RHI payment will apply to any eligible installation since April 2009. It would be unfair to apply 2014 performance standards to early adopters and exclude them from RHI when, at the time of installation, they appeared to be eligible.

But RHIs *are* available for heat pumps in theory, right? http://www.energysavingtrust.org.uk/Generating-energy/Getting-money-back/Renewable-Heat-Incentive-RHI

Are you saying that the current ones on the market won't actually qualify?

Smiley_Dan

On the cost viability of biomass long term I've just seen this on the Navitron forums, a quote from the Department of Energy and Climate Change's domestic RHI:

88. To be eligible for and continue to receive RHI support for a biomass system, fuel needs to be sourced from a supplier registered on an approved supplier list. Such a list will be set up ahead of the launch of the scheme and will be the same one that is being established for the non-domestic RHI scheme

89. RHI recipients will have to make an annual declaration that they are using only approved fuel from an approved supplier, and keep receipts as evidence for future audits.

http://www.navitron.org.uk/forum/index.php/topic,21033.0.html

I think I'm completely turned off the idea of biomass now.

Are governments specialists in wrecking markets or something?

[Deleted User]

thenudeone wrote: »

A heat pump extracts heat from the air, ground or water and transfers it to water for heating, by the same technology that extracts heat from food placed in a fridge or freezer and outputs it as waste heat at the back of the appliance.

The energy used by a heat pump is used for pumping and compression. A well-designed and specified heat pump system might provide 3-4 units of heat for 1 unit of energy used, but that would probably be in a heating system designed for using lower temperature heating water.

A heat pump becomes less "efficient" as the temperature increase required becomes higher. A home designed for a heat pump heating system may use water that's only 45-50C, well below typical gas heating system temperatures.

Yup getting the heat curve right is key. In the recent sub zero temps in Scotland our ASHP is pumping water to the Dimplex SmartRads at 38c. Very low compared to traditional CH but does the job. Wife would not be happy if it did not

[Deleted User]

we have a house with a thermal store but it is a simple one and built into the house. The downstairs floor is a thermal store as is the whole wall behind the pellet stove. Why be complicated? retrofits are massively expensive and how long would it take to get the cost back? Good insulation is key to money saving and don`t expect miracles from pv and solar thermal, our house has both (eco house). No gas here and yearly electricity costs <£420 and pellets < £260 pa. The house is so energy efficient that this is our total energy cost. We get about £1100 in fit payments. The stove and solar panels will both qualify for rhi but we won`t be bothering

The house is always at a very comfortable temperature, we have mechanical ventilation so there is airflow too

I don`t believe that pellet supply will run out but we are getting older anyway and will be finding it harder to move the pellet bags in, I expect, 10 years. The house will then easily adapt to becoming all electric with an electric boiler and a nice wall hung flame fire. All this talk of energy saving and diversion of energy is just a sticking plaster and insulation should to be tackled first

edit: 4 bed detached, large open area downstairs ie living/dining kitchen, modules of rooms in addition ie snug, study, warm practical utility room at heart of house. 2 of us retired and home all day. Moderate price house not a designer house. Two floors. House uses the sun ie solar shading with balcony in summer and sun comes in during the winter months

EricMears

Smiley_Dan wrote: »

On the cost viability of biomass long term I've just seen this on the Navitron forums, a quote from the Department of Energy and Climate Change's domestic RHI:

89. RHI recipients will have to make an annual declaration that they are using only approved fuel from an approved supplier, and keep receipts as evidence for future audits.

http://www.navitron.org.uk/forum/index.php/topic,21033.0.html

I think I'm completely turned off the idea of biomass now.

Are governments specialists in wrecking markets or something?

Insane isn't it ! I use some biomass to heat my 'Heatbank' - but it's fallen trees, prunings & scrap timber that costs me nothing. That rule prevents me from claiming anything from the RHI scheme ! (unless of course I manage to register as an approved supplier and charge myself megabucks for the stuff )

Obviously I don't need any help from the RHI scheme to collect my free fuel but there may well be lots of people who would like to buy in fuel but can't afford the prices that those government suppliers will be charging.

Martyn1981

Smiley_Dan wrote: »

On the cost viability of biomass long term I've just seen this on the Navitron forums, a quote from the Department of Energy and Climate Change's domestic RHI:

http://www.navitron.org.uk/forum/index.php/topic,21033.0.html

I think I'm completely turned off the idea of biomass now.

Are governments specialists in wrecking markets or something?

There's nothing (it appears) that the govt can't make more complicated ...... or unclear!

Have you spotted this thread on Navitron, discussing the higher temp ASHP:

http://www.navitron.org.uk/forum/index.php/topic,21458.0/topicseen.html

As mentioned earlier, may be one to watch, amongst others. Possible suggestion, since house is new (to you) and PV will be new too. Perhaps spend the next year studying consumption of oil and leccy, and generation of PV. Also get a feel for ASHP's and real performance figures. Try to insulate and draft proof as much as is possible (assuming it's needed .... it's always needed). And in a year or so's time hopefully everything will fall into place.

Being a hopeless optimist, it's possible that you may find that consumption is low enough to warrant sticking with what you've got, if it's in good nick. Best of luck.

Mart.

thenudeone

Smiley_Dan wrote: »

Are you saying that the current ones on the market won't actually qualify?

HIGH TEMPERATURE heat pumps currently on the market won't be eligible for RHI if installed after 1st April 2014, because they can't meet the minimum SPF (seasonal performance factor) required.

A "normal" heat pump (operating with much lower heating water temperatures) will be, as long as it has a high enough SPF, but they need a very good insulation and possibly new (larger) radiators to heat an older house effectively.