Wednesday, 12 February 2014

Domestic RHI Regulations Laid Before Parliament
58 Pages of Pure Reading Pleasure
The Regulations for the domestic RHI were laid in parliament yesterday, a significant step towards the imminent launch of the scheme. 

You can read them here:

As a result, some remaining points of clarification for solar thermal on the scheme have now been made public:
  • Solar for space heating / indoor swimming pools are not eligible, in fact solar DHW is not eligible if it is combined with space heating or swimming pool heating.

  • Air heating  (transpired) solar panels are not eligible.

  • The regulations refer to version 1.0 of the MCS deeming calculation (MCS024) and not the most recent version 1.1, this means that the MCS standard is immediately out of synch with the RHI and it omits the Incidence Angle Modifier from the deeming method, putting evacuated tube collectors at a disadvantage.

I suspect that the solar industry might be most aggrieved by the fact that a solar system that heats an indoor swimming pool is ineligible.  Setting aside the politics of envy, swimming pools are an ideal application for solar heating, the low temperature of the pool meaning that panels operate at higher efficiency than when preparing domestic hot water alone. 

Under the rules published yesterday, if a solar system is installed to prioritise domestic hot water with a divert to a pool once the hot water is satisfied, then the renewable heat for the domestic hot water is also ineligible.  This creates a perverse incentive to install the solar system as two separate systems, one for the pool and one for the hot water.

A simple way to deal with a complex system such as this would be to allow the owner to opt to meter heat rather than deeming it.

The scheme is not set in stone and there will be opportunities to amend it over time.  However, if the Department of Energy and Climate Change (DECC) is going to expend resources to do so, then the industry is going to have to build a strong case to support the argument that any prospective change is worth the cost and trouble. 

Should any of these omissions from the scheme concern us?  What do you think? 


  1. In addition to simple DHW systems, we also install the occasional pool heating system and supply and install solar thermal stores which are designed to supply hot water and heating support. These use an oversized solar array designed to supplement the space heating requirement outside the summer months.
    A solar thermal system producing that is used to supplement domestic space, or pool, heating will make the solar system more efficient and do far more to reduce the use of heat that will otherwise be provided from fossil fuel resources, yet the RHI does not support it and will therefore discourage investment in and development of this type of system.
    We were told that any solar thermal system installed after July 09 would be eligible for the RHI, this is apparently now not the case. All our systems since July 09 have been registered on the OFGEM register in readiness for the solar thermal RHI. We have already had customers asking why the system is registered as producing a figure that is much less than that suggested by the original design estimate.
    Although they have invested in a system to maximise their use of solar heat and minimise their use of fossil fuel, it now looks as though we have to tell them that the Governmment has back tracked and not only will they not get the promised RHI for the space heating contribution, but they will not get it for their hot water use either!
    Another half-baked support mechanism.

  2. Hi Stuart
    Now back in office. Looked at the legislation, and so far as I can see the scetion on solar thermal simply refers to;
    a) is designed and installed to provide heating solely to a single eligible property and solely for an eligible purpose using liquid as a medium for delivering that heat;
    (b) meets the requirements set out in whichever of the standards for solar thermal plants
    specified in paragraph 1(5)(a) and (b)
    It does not say anything about how the heat should be used, and does not specify hot water only. Can you tell me why space heating is not permitted with the heat?
    John Thomason

    1. Check out the definition of "Eligible Purpose" in the definitions section:

      “eligible purpose” means, in relation to heat generated by—
      (a) a biomass plant or heat pump, the purpose of space heating, or both space heating and
      domestic hot water heating, for an eligible property; or
      (b) a solar thermal plant, the purpose of domestic hot water heating for an eligible property;

  3. Ok, you are right, did not look that deep into 60 pages..but one more question. Where does it say that if you use the heat for hot water AND space heating, then the installation is not eliglible?

    1. Combine your excerpt with mine

      "Designed and installed to provide energy .... Solely for an eligible purpose". Eligible purpose = DHW, solely means a system that can only provide DHW...

  4. So once again we are been dictated too by those with little knowledge of this industry, why can't solar be part of the RHI when supporting space heating, if it is reducing fossil fuel use, then it should be eligible for RHI