Volume 19 No.3
Winter 2009

Insider viewpoint from Chris Laughton

During the summer, the Department of Energy and Climate Change (DECC) released an unusually-titled 155 page study called ‘The UK Supply Curve for Renewable Heat’. The purpose of the study was to reveal how much renewable heat could be achievable under different scenarios and at what cost. Its intention was to form a basis for the forthcoming Renewable Heat Initiative (RHI) which will support such technologies. Inside these pages was some bad news for the solar heating industry, as this technology was scored at the highest cost over other heat renewables such as heat pumps, biomass and biogas. The scenario used in calculating the cost assumed that by 2020 around 10% of the UK’s future heat will come from renewables. It also assumed taxpayer’s support of at least £2bn/year through subsidies.

The reason solar heating did so badly in the analysis initially caused some head scratching. A mysterious ‘load factor’ was used as part of the calculations, which had historically been used to analyse wind farms to indicate their actual energy production in relation to the theoretical possible if they turned every hour of the year. The answer in this case is about 25% but for solar heating it was shown as low as 5%. This needed pause for thought because, unlike wind, the likes of pre-heating domestic hot water (DHW) only works sensibly by storing up the heat during the day which can then be used at will. Most other forms of heat production can get away without storage for peak loads.

This method of analysis meant that biomass was always going to be a winner as it can easily peak enough heat to keep up with any building requirements day or night in any season. Solar, however, is always limited to delivering around 0.5 kW per square metre of roof at midday and that’s not enough to keep up with even a modest shower which needs around 8 kW. Of course, if you store solar heat up over a summer day you’ll have plenty of showers, but that was not counted when using load factors. So at a value exceeding £150/MWh, solar heating didn’t even make it on to some of the ‘curves’ in the study because it was too expensive. This was especially emphasised when some technologies like biomass actually scored far better with a negative cost.

With a bit of further prodding, DECC statisticians finally accepted that comparing wind to solar load factors was not a sensible idea. Indeed, where referring to stored heat the load factor will not provide any useful information and instead results such as system efficiency would be more useful. What a pity the study’s authors hadn’t checked this before publication. That said, this on its own would not have saved solar heating from occupying the more expensive end of renewable heating. The unfortunate fact is that just heating half your hot water from the sun is small beans compared to the energy needed to space heat an older house. Heat pumps and biomass on the other hand can provide all the required energy and therefore scored better.

A further twist in the government’s convoluted support for renewables came recently, also through DECC, this time via the much maligned Microgeneration Certification Scheme (MCS). This has brought back to the fore a long-smouldering conflict with the Department for Communities and Local Government (DCLG). Both departments are seeking to regulate heating equipment in buildings but with slightly different remits. The MCS, for example, aims for a “substantial contribution to cutting the UK’s dependency on fossil fuels and carbon dioxide emissions”; whereas DCLG aims for “Reasonable provision [...] for the conservation of fuel and power in dwellings by limiting the heat loss from hot water pipes [...] for space heating, from hot water vessels and providing space heating and hot water systems which are energy-efficient” through the building regulations.

Inevitably when two departments’ aims are close as this they are going to tread on each other’s toes. By rights, DCLG got there first with the publication of the Domestic Heating Compliance Guide in April 2006, which covered some of the basic renewable heat technologies including solar, heat pumps and wood fuel. The MCS scheme was slower off the mark, with the first drafts of its documents covering the same topics coming out in 2007. An uneasy truce lay between the departments until recently when the MCS scheme published a new document version for solar water heating. This declared that certain methods of storing heat that were not automatically deemed to comply with the building regulations by DCLG were now all-of-a-sudden permitted under the MCS scheme. Unbelievably, the MCS scheme had not obtained prior written agreement from DCLG on this variance, hence leaving installers caught between a rock and a hard place. No joined-up government thinking here!

The general technical matter raised is indeed a controversial one. Vested commercial interests have been arguing around the point to allow a householder’s interaction with heating equipment, such as altering thermostats or timers, to be counted as equal for energy savings compared to if they had fitted, say, a gas condensing boiler or dedicated storage volume for solar heating. Of course, any householder can already get a reward for playing with their heating timer and thermostat. It will give them a reduction on their fuel bill. Indeed, this is the cheapest way for anyone to reduce their carbon dioxide emissions; a fact notably omitted from the aforementioned DECC Supply Curves study. So perhaps this reveals that the government is now changing its strategy and will give up on expensive renewable technological solutions? Instead I can only presume it intends to fund us all to limit ourselves to one bath or shower a week and otherwise wear woolly jumpers whilst in our homes. This way, the government gets to look like it is doing something about climate change and we get more money in our pockets. I just wonder if it couldn’t achieve those aims by a levy on fuel bills rather than complex renewable subsidy schemes that can only be accessed by those already wealthy and knowledgeable enough to do so.