Peckham Power: the real thing… solar hot water notes

 Peckham Power: the real thing… solar hot water

Wednesday 12 May 6.30pm

Present: David Byrne, Josephine, Clyde Watson, Jack Kelly, Benedict O’Looney, Lukasz Gruszczynski (and toddler!), Gill, Yvonne Killen, Anna Plodowski, (Eileen Conn attended very briefly)

Starting note

Broadly speaking, there are two types of solar hot water systems, “direct” and “indirect” systems.

In a direct system, the water that is heated in the solar thermal panel flows directly into the hot water system and is used directly as hot water.

In an indirect system, the water, with anti-freeze in it, is heated in the solar thermal panel in a separate circuit that heats a heat exchanger coil isolated from but giving heat to the hot water in the tank, and that tank water then goes to the taps.

Direct systems are no longer approved due to health implications for Legionaire’s disease (the Legionella bacterium isn’t killed in such systems).

Take Home Messages

After-sales support and regular maintenance checks were identified as at least helpful if not essential by all those who had already pioneered solar thermal hot water systems. The current lack of basic after-sales customer service was noted with considerable concern. “These are sales companies, not customer-service companies.”

Solar thermal hot water does not function in exactly the same way as conventional central heating systems, and therefore the size and type of system installed needs to take into account not only peak demand, but also the most common type of hot water demand [i.e. median demand], as well as future technical developments which may need to be included in the building at a later date, such as air source heat pumps.

Gill

“Here in East Dulwich, I have two panels of 4 square metres using a flat panel system, not evacuated tubes. The supplier of the panels was Solar Works, and they were purchased in 2003 using grants from London Borough of Southwark (£500), and Solar for London (£500). LBS insisted that only one type of solar thermal panel could be purchased using their grant so I did not have a range of products to choose from.

“My husband spends a large part of the year living in Spain for business and he already has solar thermal panels there which work fine, so we’ve been very disappointed with our experience here in the UK in which we’ve had several problems.

“The system cost £1,400 for the 2 solar thermal panels (2m²), and £2,300 for scaffolding and labour.

“The system worked fine for the first two years, but since then, there have been several problems. The first indication I had of a problem was when a stain appeared on the ceiling. This turned out to be due to the expansion tank for the hot water overflowing, with hot water overflowing out through the expansion pipe that sticks out through the sofit. Hot water was flowing onto the flowers in the garden and killing them, as well as the overflow running onto the ceiling and staining it. I therefore had to pay for a bigger expansion tank to be installed.

 

“Last year, the pressure in the solar hot water system kept on going down, I looked in the manual and followed all the instructions but the pressure still kept on going down, so I finally wrote the company a letter and explained that the system was not responding as in the manual.

 

“The company then inspected the system and identified a leak in what had been a frozen pipe, with the leak probably in the connecting tube between the four panels.”

 

Gill doesn’t want to pay the £165 for the repairs, and wasn’t happy abut the lack of regular servicing of her system which she felt meant that developing problems were identified early on.

 

Questions were asked about what sort of solar thermal system it was that Gill had – a direct system (in which the water heated in the panels flows directly into the mains hot water system and is used by the household for heating and washing directly) or an indirect system (in which the water heated in the panels flows into a coil that heats another water heating cylinder, with the water in the second system being heated by the first). Gill wasn’t sure, but those present looking at the manual she brought, thought that she had an indirect system.

 

A key aspect of Gill’s problem seemed to be that various members of her household need to be away often, especially over the summer, but when she is around she wants hot water for up to 8 people, so she has very variable demand for hot water throughout the year. There are long periods when the hot water created by the solar thermal panels is not being used at a fast enough rate because there aren’t 8 people in the house but only two or three. Thus the water in the system gets extremely hot, causing overflows in the expansion pipes (these overflows are designed to to allow for expansion of water volume with increasing temperature so that circuits do not burst).

 

There was some discussion as to whether Gill’s system had been “overspecified” for her needs, and that a smaller system might not have been more suited to the variable demands of her household, even though this would have meant that when all 8 members of the household were present, a smaller system could not have met the hot water demand. It was noted that solar thermal hot water systems do not function exactly like a central heating system, supplying hot water on demand, and that an important part of the wider adoption of solar thermal hot water included learning how best to get solar hot water systems to function for different household’s requirements. This required recognition of the ways in which solar thermal hot water differs from current central heating hot water systems.

 

An additional problem that Gill experienced was that a workman drilled a hole in her roof when installing the solar panels back in 2003.

 

Clyde Watson reported that Which? Magazine in March or April 2010 produced a report about solar thermal panels for hot water, which highlighted the way in which some companies were charging excessively high prices for installation.

 

Benedict O’Looney

 

Benedict spoke about the experiences he and his mum had had with her system in a rural setting east of Ashford, in Kent.

 

Technically, the solar panel is really nice (Ritter evacuated tubes). “A really nice bit of German kit.”

 

Benedict’s mother signed the contract with the salesman when Benedict was away, in response to a knock on her door. 4 days later, the company then phoned and asked “Did you feel pressurised by the salesman when he visited?”. In response to saying that she had, the company immediately reduced the price by £1,000 (to about £4,000) – raising the suspicion that their system and installation was overpriced to start off with… (The company was Simplee Solar.)

 

There have been no problems with the plumbing or any leaks, which is good. However, the system has proved really perplexing to run! It has 3 inputs into the hot water cylinder, from:

1. the boiler

2. the indirect solar system

3. the electric immersion heater

 

This system has too many heat inputs so “the water is as hot as from an Icelandic volcano”!!! Since Benedict is an architect and used to making technical drawings, and has spent 3 years watching, on many occasions, the demonstration CD that came with the installation, he has slowly been able to build up a picture of how the system actually works, and on the basis of that, work out which valve to turn off the excess heat inputs. It now works OK, but not everyone has a relative with the technical skills to deduce how the system works and which valve needs turning off… Everyone noted with concern the lack of ongoing, post-sales, customer support.

 

The Ritter system includes a holiday switch so that excess hot water is not produced when people go away. Since it’s an evacuated tube system, water is being heated if it’s sunny regardless of the outside temperature. (Flat panels are also heated but to a lesser extent) The system produces enough hot water for personal washing and washing the dishes, and includes a digital LCD display that shows cumulative data about the water temperatures that have been produced.

 

Josephine asked if the reason for the excessive additional heating was to ensure the temperature of at least 60° Celsius was reached sufficiently often to destroy the Legionnaire’s bacterium. Benedict reported that the system’s manual stated that that temperature had to be reached at least once a day, when there was no further possibility of solar gain. (In most systems this heating has to be done manually in the evening after the Sun has gone down if indicators show that 60 Degrees has not been reached, usually by just turning the boiler hot water on)

 

Josephine

 

Her system is a bespoke 2 panel system made by a skilled heating engineer friend out of copper tubes, holding between 11 and 12 litres of water, for a household of 6.5 people (6 adults and one young child) in Peckham. A cycling counter on the system records how many times the water has cycled. (This went mad once when they were away on holiday, and cycled round 4,000 times!).

 

It’s a direct system (i.e. in which they use the heated water themselves in their own mains hot water system), and has broken twice:

 

1. when they noticed the gutter overflowing, they realised that the system had frozen causing a leak. (Because the water in the panels in this type of system i.e. a direct system, is used in the taps, no anti-freeze can be added.)

2. when water came flowing down through the ceiling, they realised they had another leak

 

Their heating engineer friend is to repair the panel and modify the frost protection system before the beginning of June.

 

Originally, the system reverse ran, so that if the outside temperature was very low, hot water was pumped into the panels on the roof to prevent water freezing in the panels which would cause burst pipes and thus leaks, but this system malfunctioned. [It was also noted that whilst this was a workable solution in principle, it required heating of the water by the central heating system boiler, which unfortunately increases the environmental impact of the system.] The solution now is that if the outside temperature is cold, water from the panels is all emptied into the grey water storage tank in the loft (it holds 40 gallons) so that the water is not wasted, and the panels are then empty of water and thus not vulnerable to leaks caused by the bursting frozen pipes.

 

J and family are now considering installing air source heat pumps. These take heat from the air through a refrigerant, which is then used to heat the internal hot water system. (At the time of the meeting, grants were available for air source heat pumps. Since then the coalition government has announced that grants for domestic renewables have been withdrawn.) In principle, a solar thermal system for hot water should be very compatible with air source heat pumps (although you may need to install bigger radiators for air source heat pump systems in order to maintain space heating capacity. The air source heat pump takes the place of the boiler, with the central heating system plumbing staying in place.

In order to install an air source heat pump system, they considered whether they needed a bigger hot water tank [i.e. for both the solar hot water and the hot water from the air source heat pumps. Unfortunately, the hot water tanks available were not suitable, because too much of the heating needed to come from gas, rather than solar.

 

Even in the winter, J P-B’s household does get some hot water from their 2 panels. During the summer they get around 14 cycles of 12 litres a day ie 168 Ltrs per day, but in the winter, if the sun is out, they get 1 or 2 cycles a day. One way to get the best from the system in the winter is to use the water at a lower temperature e.g. 50° Celsius and use that, thereby getting two cycles at a lower temperature, rather than just one at a very high temperature.

 

Points made in general discussion

 

It’s important to have service costs factored in to the overall cost.

 

Similarly, it’s not a good idea to have a system “over-specified” i.e. check what capacity of hot water you really need and don’t buy panels for more than that. Solar thermal hot water does not work on demand as does a central heating system.

 

A user group would be very helpful to learn how to understand the manuals and how to get the best out of the system (assuming that solar thermal hot water installers don’t smarten up their act and start providing decent customer after-sales care).

 

It would be very useful to have a list of solar thermal friendly plumbers to put on the Peckham Power website. Nick Cotton was mentioned by one of the “Peckham Pioneers” as a solar thermal trained plumber – details to be exchanged by attendees after the event.

 

Evacuated tube panels are still dependent on the orientation to the sun, whereas flat panels can be used in a wider range of angles relative to the sun, and can also be used vertically.

 

A further meeting at which a solar thermal engineer could advice the three “Peckham Pioneers” on their difficulties with their systems would be very much appreciated.

 

Advice from Yvonne Killen (local resident who also works for Creative Energy Networks who are contracted to provide advice for the Energy Saving Trust): Funding for solar thermal panels from the Renewable Heat Incentive scheme; this scheme has not yet been approved but should be going live next year, and will pay those who have installations that generate heat, including hot water, a fee for doing so. There will need to be generalisations made about the per therm payment (because it is difficult to measure exactly how much heat is being produced, unlike electricity production). However, it will be necessary to have used a credited (i.e. officially recognised) installer of solar thermal panels in order to claim payments under the Renewable Heat Incentive. The range of technologies that should be covered by the Renewable Heat Incentive includes air source heat pumps, ground source heat pumps and solar thermal panels for hot water.

 

Yvonne also reminded people that in order to get grants for solar thermal or other renewables technologies, you must meet the minimum insulation standards first. [See note above about withdrawal of domestic grants for renewables technologies installation by the coalition government on a date after this meeting.]