Here comes the sun: a field trial of solar water heating systems by the Energy Saving Trust.
Solar industry news, comment and analysis by Solartwin.
There are plenty of good things about this new report as well as some concerns. But first, before both the praise and the damnation, here is the EST’s summary of its key findings.
1. Solar water heating systems have the potential to work well in the UK and the Republic of Ireland when installed properly and controlled adequately by the user.
2. Well-installed and properly used systems provide around 60 per cent of a household’s hot water. EST also found examples where systems were not properly configured or used, and where the contribution from solar was as low as 9 per cent. The median solar fraction across all systems was 39 per cent.
3. Householders in the trial were happy with their solar water heating systems: 84 per cent were “satisfied” with their system, and over 50 per cent were “very satisfied”.
4. There was little difference between the total solar energy yield of those installations that used flat-plate solar collectors and those that used evacuated-tube solar collectors.
5. The way householders use their solar water heating system is critical in achieving the best results from solar water heating systems. Better advice to users on how to control their solar water heating systems (in terms of volume of hot water use, timing of back-up heating and hot water use, and temperatures required) is essential.
6. Where mains electricity provided power to the pumps and controllers of systems in the trial, the amount of energy used was generally small (at 5%) compared with the overall heat delivered.
7. EST observed insufficient insulation installed on some hot water storage cylinders and pipes. This significantly reduced the proportion of hot water their solar water heating systems provided.
8. Industry standards should be reviewed to ensure they reflect the findings of the trial and the need for better advice to customers.
9. Solar water heating systems can achieve savings on energy bills. Based on the results of the trial, typical savings from a well-installed and properly used system are £55/year when replacing gas and £80/year when replacing electric immersion heating; however, savings will vary from user to user.
10. A well-installed and properly used solar water heating system is likely to provide carbon savings. The typical CO2 savings are 230kg/year when replacing gas and 510kg/year when replacing electric immersion heating.
Three key energy measurements were made over the one year study were used to establish the performance. These were:
- The heat energy delivered by the collector to the water
- The heat energy delivered by the back-up heat source to the water
- The mains electrical energy (if any) used to operate the pump and control system
While installing monitoring equipment, at some sites the EST discovered a number of problems, including:
- Malfunctioning air vents on the solar collectors (We have simply designed away the need for air vents at the collectors.)
- Glycol leaks from solar collector circuits (We don’t use glcol. We use water.)
- Inadequate or absent insulation (Insulation is a issue which may be common to all systems.)
- Pump flow rates set too high (This applies to mains pumps only. High flow rates waste electrical energy and pollute the atmosphere excessively with CO2. Our pumps are variable speed PV Pumps, so inherently they don’t risk any of these problems.)
Many of these issues should now be addressed by the Microgeneration Certification Scheme (MCS), which did not exist when the systems under study were installed.
Now for the pithy comment…
Good things about the EST Solar Thermal Field Trials Report 2011 “Here Comes The Sun”
Diversity was studied and recognised. This fact alone is a major step forward for the UK solar thermal industry which has struggled with a market limiting :”old solar is the gold standard” minsdet for years. In fact 88 domestic sites were selected to participate in the study and had monitoring equipment installed. Of these sites, the study included products from different manufacturers:
- 54 flat-plate systems and 34 evacuated-tube systems
- Freeze-tolerant and crackeable systems.
- Retrofits to existing cylinders and new cylinders, twin-coil or multiple cylinders
- Pressurised or open-vented systems
- Thermal stores
- Direct or indirect solar collectors
- Mains power and PV powered pumps
- Combined heat pump and solar water heating systems
Our approaches above are shown in bold.
The importance of installations and operation. Insulation losses were identified as a major issue, as was timing of backup heating.
Mythbusting. This report vaporises a plethora of false claims about money savings and carbon savings relating to solar heating. One prominent past claim by its only solar panel manufacturer sponsor, Worcester Bosch, (part of a huge multinational solar and boiler company which is apparently unregulated by UK’s renewables energy regulator, the REAL Code!) that payback can be less than ten years, does not seem to stack up any more.
Mythbusting about evacuated tubes. There was found to be no difference in the amount of energy produced by flat-plate solar collector systems and evacuated-tube systems. The median for flat-plate collectors was 1,156kWh per year and the median for evacuated-tubes 1,140kWh per year. That evacuated-tubes were more efficient per square metre was reconfirmed: presumably an important point for people who live in buildings with tiny roofs, such as garden sheds.
Hard data on the energy benefits of solar water heating. In general, the solar water heating systems in the trial performed well, producing a median output of 1,140kWh (of thermal energy) per year. This equates to around 39 per cent of a household’s hot water demand. Astonishingly the EST report did not deduct the pump energy requirement in order to get its net energy benefit, which is obviously a more useful and truthful figure. The net energy benefit figure is presumably 1085 kWh pa.
Commonsense reconfirmed on how to boost the energy benefits of solar heating. Unsurprisingly, the amount of energy saved increased the more hot water was used. And generally, dwellings with more occupants used more hot water and so they achieved greater benefits from their solar water heating systems.
Commonsense reconfirmed again. In the trial, a number of householders used electric showers, which heat water themselves rather than using the solar-heated water, and so this reduced overall hot water use. Under these conditions, the maximum benefit of having a solar water heating system obviously cannot be achieved.
Cold truths as well. The CO2 saving benefits of installing solar thermal systems are is the roughly the same as you would get from draught-proofing round all the doors, windows and skirting boards in a gas heated or electrically heated home.
Hard data for users of solar heating where mains gas is “displaced” by the sun. The money savings were £55 per year. The CO2 Savings were typically 230 kg per year. This CO2 saving ties in closely with the previous work funded by DTI nearly a decade ago.
Hard data for users of solar heating where mains electricity is “displaced” by the sun. The money savings were £80 per year, which is over 50% higher than for gas. The CO2 Savings were typically 520 kg per year. This CO2 is more than double the equivalent saving for gas, this is because electricity is far more “carbon intensive” per unit of energy. It is generated and delivered at only about 40% efficiency, often from mains gas. Hence the higher figure for CO2 savings for mains electric users.
Parasitics are falling. The report says that mains powered pumps incur a 5% energy clawback. This is great news for the solar thermal industry, because the earlier DTI report showed the figure was more like 7% and a past EST study even showed 8%. Mains pumped solar water heating systems pollute CO2 during heir operation and unfortunately for the environment, in a typical solar thermal installation, each one percent of parasitics is equivalent to 2-3% of carbon clawback, which along with antifreeze replacement, is the Achilles’ heel of old solar. Why are parasitics falling? Probably because some solar thermal technologies use low power or variable speed “modulating” pumps. Incidentally, Solartwin’s parasitics are zero, the best of all, because we use onsite-generated PV electricity to power our pumps every time.
Concerns about the EST Solar Thermal Field Trials Report 2011 “Here Comes The Sun”
Data gaps. There is no helpful data for users of solar heating where fuels such as oil or coal or biomass are “displaced” by the sun. People who live off the gas grid will be disappointed at this omission of both the potential money savings and the likely carbon savings potential of solar thermal.
Spin and unjustified market-shaping. It contains some subtle but important greenwash. It claims to be impartial, yet it is sponsored by Worcester Bosch, who hold the Vice Chairmanship of the Solar Trade Asssociation which has massive vested interests in concealment:
Concealment. NOT disclosing to the public the net energy benefit of solar, which would be a more honest way to, for example, compare systems. Instead the report gave figures for the gross thermal benefit, which is higher in mains umped systems.
(Consequently solar heating consumers will mistakenly make buying decisions based on gross energy rather than net energy, which is a more sensible thing to so. This concealment disadvantages suppliers like us.)
Concealment. NOT disclosing to the public the extent that their mains pumped solar water heating systsms all pollute CO2 during their operation. We suspect that in most of their installations, at least 10% of their carbon benefits are negated at the power station chimney. Surely pollution associated with using environmental technology should be discussed? There are numerous illustrations of solar water heating panels, but not even one of them is PV pumped, even though we offered photos to EST.
(Consequently solar heating consumers are not made properly aware of significant operational pollution impacts when they make buying decisions about this supposedly environmental technology, solar heating. They need to be told clearly how to eliminate these impacts by using PV pumping. Nor will they know what PV pumped solar thermal even looks like. Most have a small PV panel attached. They are easy to spot. These two concealments disadvantage suppliers like us.)
Concealment. NOT using the word Legionella regarding the safety of stored water in solar water heating systems. The report delivers this cover-up. This matter is so important that I have had a “you are on your won. Barry” phone call from Neil Scofield, Worcester Bosch’s Head of Sustainability following me raising the Legionella safety issue with Which/ Magazine and the solar water heating industry’s successful pulling of their article on the subject of solar and legionella in 2010.
(Consequently consumers, by being kept in the dark on what to even ask suppliers about when it comes to legionella safety, will make bad buying decisions: choosing higher risk solar thermal systems over those which intrinsically have less. This concealment disadvantages suppliers like us.)
Concealment. NOT debating properly and disclosing to the public the very real maintenance costs associated with solar water heating. Water hardness control, valve, pump and antifreeze replacement cycles were not even mentioned in this report, which is supposed to help consumers. There is an industry wall of silence on this important issue of maintenance costs.
(Consequently consumers, by being kept in the dark on what to even ask suppliers about, will make bad buying decisions: choosing high maintenance solar thermal systems over those which require less. This concealment disadvantages suppliers like us.)
Myth consolidation. It is interesting to know that well-installed and properly used solar water heating systems provided around 60 per cent of a household’s hot water and that the median figure was 39%. However how useful is this “solar fraction” figure really? It’s a bit of a red herring. You can boost the figure to 100% simply by having no backup heating at all and putting up with cold showers on gloomy days (and elevated Legionella risks). Funnyfunny that solar fraction was reported without this explanation while % operational carbon clawback was not.
(So UK’s unfortunate solar thermal consumers will mistakenly believe that solar fraction is important, when it is not really that important at all.)
Lack of vision. The report could have called for Life Cycle Analysis, which would have forced suppliers to publish “years to carbon and energy breakeven” data. Sadly it did not. Ours breaks even on energy in 2 years.
(Publishing LCA would allow consumers to choose greener products, such as ours.)
Overclaiming. The Energy Saving Trust say that it is “committed to providing impartial and realistic advice to industry and to consumers, helping people to save energy and reduce carbon emissions.” In the context of reducing carbon emissions as far as it can, why does it not state in the report, the percentage carbon clawback of old solar? EST have the data, but they sat on it.
(Consequently solar heating consumers will mistakenly make buying decisions based on the tosh referred to above which is validated by the ST badge. This means consumers will get a raw deal and it disadvantages suppliers like us.)
Conclusion. Here comes the sun. But draw some strategic clouds over it please…
In all, this report is another crummy solar thermal industry fudge. Transparency, consumers, safety and the environment play second fiddle to the imperatives of zebigboyz.
My colleagues and I are apparently meant to be grateful for the appearance of this eviscerated market limiting junk. Ha! This report was supposed to be our funeral song. Old solar Stooges such as The Solar Trade Association’s Top Technical Writer, Stuart Elmes, who gets the first named credit in the report, could easily have abused their position of trust, as past solar stooges have tended to do, to insert killer clauses against innovations, such as ours. I wonder why he did not get to spike our business this time? Sue us, Sleazy Stuart Elmes: you KNOW that what I write is true!
Written and published by -
Genfit - 0844 567 9032