The Bridport Renewable Energy Group (BREG) helped Treewise Toddlers in Symondsbury to get a DIY Solar Water Heater.

Nature of Project
The purpose of the project was to provide warm water for health and hygiene reasons, alongside the activities which take place in Willy Tuck’s Orchard, Symondsbury. A key one of these was the Treewise Toddlers playgroup who were based in a permanent yurt in the orchard, and whose activities involved both mud and food. The scope was later expanded to include separate hand washing facilities in support of the composting toilet.

The design of the solar water heater drew heavily from the booklet published by the Centre for Alternative Technology: Solar Water Heating a DIY Guide by Paul Trimby. Costs were kept to a minimum by maximising the use of recycled material, and adopting a DIY approach.

The site is considered difficult as it is on a North facing slope, is shaded by orchard trees and experiences heavy frost in Winter. This led to careful choice of position, and timely draining down and refilling (not always achieved!).

The project started with the Mark 1 solar panel based on the use of old central heating radiators, glass from a double glazed french window, scrap timber and a recycled hot water cylinder. Some of the construction work was carried out by a CooS student (Children out of School). The finished unit was rather ungainly (see photo) and some adverse comments were heard about its impact on the Area of Outstanding Beauty in which it was situated.

Unfortunately (or fortunately depending on your disposition) within a year the steel radiators had rusted through and system drained itself. This was not altogether a disappointment, as the large volume of water within the radiators had meant that they were slow to warm, particularly in intermittent sunlight. They are also very heavy.

The replacement Mark 2 model addressed these issues by taking a more elegant form (see photo), and by turning to a ‘clip fin’ design. The clip fins are those used as for spreading heat in underfloor heating systems, and are available from BES Ltd. All pipework is in copper, and although more expensive, corrosion is eliminated. The system is also quick to heat up, and from temperature measurements about twice as efficient as that based on radiators.

The heating in both models made use of the thermosyphon principle – hot water rises. The Mark 1 was indirect ie with a coil in the cylinder, and unfortunately antifreeze had not been included and so the system suffered rust. In the Mark 2 system, direct heating has been employed – there is no coil and the heat is fed directly to the cylinder contents. The cylinder itself is a standard domestic vertical unit laid on its side to reduce the overall height. The framework and cladding is in Western Red Cedar available Barnaby Gower at Toller Porcorum. It has natural resistance to decay and has avoided the use of preservatives.

Community Involvement
Bridport Renewable Energy Group carried out the project with support from Treewise Cooperative, CooS, Dan Williams, Honiton recycling centre, Bridport South Street recycling centre, Barnaby Gower, and many individuals. BREG were at the time an unconstituted community group run by volunteers.

This story was provided by Sustainable Dorset, the website for DA21: