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Solar Panels

August 2007

In an attempt to become just a little bit more energy efficient we decided that one of the first improvements we would make to the house would be the installation of solar panels for hot water. Our existing tank was rather old, small and required the use of a very noisy pump to provide water to the newly finished ensuite. It was also not ideal for use with solar panels and was in the wrong place so it was a good time to relocate our hot water supply to provide the shortest distance to the solar panel and the household taps.

An unvented system would also remove the need for any electric pumps so we invited John from Sustainable Technology Ltd to come around and look at our setup in detail. Due to the design of York Cottage there is very little in the way of flat roof space. He advised that the only real location that we could mount solar panels was above the conservatory underneath the back bedroom window. Unfortunately that area faces west-southwest and is in shade from the new bedroom roof until midday so the new system would only be about 50% efficient. However, this location would mean we could move the tank to within a few metres of the solar panel, and directly above the mains inlet in the kitchen below. Even if the tank only got a small amount of heat from the sun we would still benefit from a new unvented tank in a better location and as the old tank was mainly heated via electricity anyway (oil during the winter) we wouldn't be any worse off.

Before John could begin the work we had to prepare the area for the new tank. We ripped out the old cupboard in the back bedroom and stripped off the plasterboard on the walls and ceiling in that area so that we could replace the thin bit of insulation with the new (and pricey) Kingspan. We insulated all the eaves with Rockwool while we were there. We then put up new plasterboard, put in some temporary plumbing and provide a spur for the control equipment. As usual, things weren't quite as simple as they should have been. All of the electrics in the back bedroom were already spurs so we had to take the new ring main that had been put into the new bedroom and extend it into the back bedroom. While doing all this cabling we also put in a television coax and a network cable.

The New Tank

We were finally ready for John to come back and begin the work. He turned up with the tank and began to work. We chose (with John's advice) a 190 litre Santon unvented cylinder fitted with two immersions. The quality and neatness of his pipework was very impressive.

The Solar Panels

We were originally going to have two solar plates rather than the tubes but because the space was so tight we had to change our plans to an Apricus 30 tube system just before John started the installation. Unfortunately his supplier did not send him enough tubes so he drove half way across the country to obtain the parts rather that let the job run over the 5 days he had allotted for it.

The system was commissioned at the end of August and within 2 days we had a full tank of 60 degree water. We have been amazed at how quiet and simple the system is and how well it works. During September the system continued to provide all of our hot water needs, however as the days got shorter during October we noticed a drop in the water tempurature and had to get the immersion heater wired into a timer to heat over night. This was due to the location of the panels but because of the layout of the roof there really was no alternative. If the panel was south facing then I believe it would provide most of our hot water needs throughout the year.

The whole system cost £4,300 including all parts and installation although a £400 government grant helped reduce the price for us. A large portion of this cost was the new tank which now provides us with mains pressure hot water, giving us the best shower we've ever had. It is difficult to say how long it will take before the electricity this system saves will pay for the initial cost, maybe 8-10 years, but we do think it was well worth the expenditure.

Being quite competent at DIY I have often had a relatively low opinion of general tradesmen we have hired in the past and have often felt that their workmanship simply doesn't match the care that you put into your own work. However, John is obviously very passionate about his craft and I often saw him admiring his work. He took great pride in every aspect of this job and if he wasn't happy with anything he would do it again rather than "make-do". If you ever consider installing solar panel technology I would recommend that you talk to John. We can not recommend him highly enough!

August 2008

Update: After exactly one year the system has provided 1400 KWh of hot water, 300 more than John had estimated.

July 2009

Still running without any intervention at all however we had a 3 day powercut and realised that the limitation of the system is that without power to run the pump hot water runs out. Realistically though such a long powercut is very rare. We did call John who is always happy to offer advice and help and he said that the only problem with having a 12v pump powered by a solar panel is that the 12v controllers available are very low end. As we intend to eventually have solar panels installed with a battery bank backup it isn't worth going to the expense of changing things.