Friday 16 November 2012

Thoughts on the RHI Domestic Consultation

The Next Big Thing?
Image: Viridian Solar
Yesterday the Solar Trade Association (STA) released its draft consultation response to the Renewable Heat Incentive domestic consultation to its membership for comment.

For anyone thinking of responding to the STA or directly to DECC, here are some things to mull over:
1.       Solar – grant or tariff

The consultation definitely leaves the door open on changing the support for solar thermal from a 7-year tariff to an upfront grant.  While the choice may seem blindingly obvious – customers would prefer a grant every time – it’s worth pausing to consider what might happen if solar thermal is treated separately to other technologies.
If solar is in a separate grant scheme, even if “branded” RHI, then it would be much, much easier for politicians to tinker with.  The recent history of solar grants (Clearskies and Low Carbon Building Programme) indicates that the temptation to continuously “improve” the system may be too great to ignore.  Even if you believe that the team setting up the RHI has the best of intentions (and I do), the nature of government is that there’ll be different people running it before too long.

For this reason, the STA is currently consulting on a hybrid – a combination of an upfront grant against cost of the cylinder upgrade and a solar thermal tariff for 7 years just like the rest of the RHI technologies.  There is a logic behind this, as the cylinder upgrade as part of a solar thermal installation results in energy savings that are not given credit in the RHI impact assessment, see my earlier blog article on the subject.

2.       Scope for Cost Reductions

The STA has estimated potential cost reductions of 35% if the solar thermal industry can achieve economies of scale (imagining a market of 150k installs/year, an increase of 5-fold from today's estimated 30k). 

The nature of solar thermal equipment is that much of the cost is fixed by the price of global commodities.  Unlike solar PV, where the main component cost is for a material that has no other bulk uses (silicon wafer),  these commodities are materials like aluminium, copper, and glass which have many other uses.  Changes in the solar market are unlikely to influence the price of these materials.

For this reason, the STA is proposing that the majority of cost reductions could come from efficiencies gained in installation rather than price reductions in materials.  It is easy to focus on the actual process of installation and to wonder whether this can be sufficiently squeezed, but that is to ignore other business efficiencies that would emerge as solar thermal graduates from cottage industry status.
Imagine a solar installation business that increases in turnover by 500% over a number of years.  Would it need 5x more people in the office, or would specialisation allow people to do business processes more efficiently?  Could it have staff which did nothing but surveying?  Would these people have to travel less distance between appointments?  How about marketing?  How much more effective would be each pound spent advertising the business when the potential market is so much larger?
Fundamentally, you have to ask the question, why should UK plc invest in solar thermal?  What’s the end goal?  Unless the RHI helps solar thermal unlock installations at lower cost so that it doesn’t need subsidy in future as energy prices increase then why bother?

Friday 9 November 2012

Heat Losses from Hot Water Cylinders

the solarblogger roots around in the nation’s airing cupboards
Tucked away in a cupboard, perhaps behind a pile of towels and bed linen, out of sight and out of mind.  The domestic hot water cylinder often escapes our attention, but it has a big role to play in the energy efficiency of our homes. 
Modern cylinders have a thick jacket of polyurethane foam insulation around the outside to reduce heat losses, but the connecting pipes can be just as important.  These provide a path for heat to escape from the cylinder.  To appreciate this fact you just have to touch them to feel how hot they can be, and how far from the cylinder connection they can conduct the heat.

Even in modern houses built to higher energy efficiency levels it is common to find a hot water cylinder installed without any insulation on the connecting pipe-work. The image (left) was taken at a visit to an eco-exemplar show home this year.  The home has a host of energy efficiency measures such as solar water heating, solar PV, and mechanical ventilation with heat recovery.  The only pipes in the cylinder cupboard with insulation on them are those to the solar panel. 
Presumably the plumbers had so impressed themselves with the job they’d done on covering the copper pipes with silver paint that they didn’t want to hide the beautiful craftsmanship. 
You can also see on the cylinder that the secondary return fitting is unused (just below the grey thermostat on the right hand side of the picture).  Instead of being closed off with a plug a short length of pipe is sticking out with a soldered end fitting.  This creates a completely unnecessary conducting rod to remove heat from the cylinder and transfer it to the surrounding air.
Did the energy assessors tick the box that said that all visible pipe-work was insulated?  I’d bet money that they did.  This is a failure of compliance as well as a brilliant illustration of a lack of awareness from installers. 

If a new build eco-showcase can look like this, what hope for millions of existing homes around the country, and how much impact this can have on their energy performance?

Show me the money

Research from the Energy Saving Trust demonstrates just how significant the heat losses from poorly performing hot water cylinders can be.

Heat Losses from Domestic Hot Water Cylinders

Source: Energy Saving Trust, In-situ monitoring of efficiencies of condensing boilers, June 2009

During the heating season, these cylinder heat losses are warming the house and reducing the space heating load.  For new homes with ever higher levels of insulation the heating season is becoming shorter and shorter, but for most homes you can safely assume it lasts half of the year.  So the other half of the annual loss is wasted energy, and this is shown in the last line of the table.

To put these numbers in context, the energy to heat the water demand for a four-person household is around 2,140kWh/year.  The average cylinder losses in the study add half again to the hot water load, the worst performing cylinders in the study double it.
Of course, it’s impossible to reduce the losses to zero, but what might be achievable?

Well, hot water cylinder manufacturers test and declare the heat losses from their cylinders. When you take this figure and adjust it for the fact that the cylinder doesn’t spend all day at 60C you find that a typical 210 litre modern cylinder loses around 355kWh/year, so that’s only 178kWh/year of wasted energy taking the heating season into account.  Conclusion: a modern, well-insulated cylinder saves 750kWh/year compared to  the average found in the study.
Most solar installations involve the replacement of a hot water cylinder and with upcoming changes to the MCS installation standard for solar thermal, the solar thermal installer will have to ensure that all pipes and fittings are well-insulated (not just the solar ones). 

The energy savings that come from improving the hot water cylinder as part of a solar heating installation are not acknowleged in the MCS energy estimate and do not count as renewable heat for the forthcoming Renewable Heat Incentive, but they are real and they are significant.

Sunday 4 November 2012

Who's Installing Solar PV?

In recent months I've heard a number of people saying of the solar PV market in the UK that "the domestic market is dead" and "commercial installations are where it's at".   Do the statistics support this?  Let's have a look.

The two pie charts in the graphic below shows the proportion of PV  installed under the Feed in Tariff (FIT) by the size of the installation.  It covers two six month periods, October 2011 to March 2012 and April 2012 to September 2012.  The second period is post-April, after which the government had largely set in place its measures to slow down what was rapidly becoming an unaffordable incentive scheme.  The earlier period spans three peaks caused by the race to complete installations before successive "improvements" to the scheme came into force. 
Chart showing how the solar PV market has developed in the last 12 months in the UK
As the tariff levels have reduced, the savings from own-use of the electricity generated become a more and more important proportion of the financial return. That's because if you use a unit of electricity generated you save around 12-15 pence, if you export it you get 4.5 pence.

Commercial buildings tend to use most of their electricity during the daytime - powering computers, industrial processes, lighting and air-conditioning - at least five days of the week, and sometimes seven. This matches periods of maximum PV generation very well.

By contrast, domestic properties tend to use electricity in the evening, so less of the electricity generated is is used in the building and the financial rewards are likely to be smaller. Installations in the size range of 10 to 100 kWp tend to be commercial scale installations on factory roofs, farm buildings, offices and schools, and this segment of the market has increased its share of the total. It hasn't grown, but it has shrunk much less than other sectors.

However, this increase in share hasn't been at the expense of  domestic scale installations, which have held steady at around 70% of the market and still represent the lion's share of installations by kWp as well as by number of installtions. Instead, installations in the 100-5000 kWp range now take less share of new registrations under the FIT.

So, in answer to the question, do the statistics support these views, the answer is both yes, and no.  Commercial-scale installations have definitely become a more significant part of the total, and are likely to continue to do so as electricity prices rise and tariff levels decline, but the domestic installation market is far from unimportant.