How Spiral Sun Solar Showers Work
The Solar Shower Tent
The solar collectors used by the showers are of the passive type i.e. the water is heated directly by sunshine. Collectors of this type, of various different designs, have been around many years. For simply heating water they are far more efficient than the flat glassy plate types that make electricity (known as PV or photovoltaic panels or collectors).
In Spiral Sun Solar Showers the passive solar collectors are in the form of spirals of black plastic pipe. The colour black is used in all passive collectors because it efficiently absorbs all the sunlight’s energy and converts it into heat. This heat is passed onto the water inside the spirals of pipe and so heats it up.
The spiral solar collectors are housed inside the solar collector tent. Six are on the floor of the tent in a ring around the inside shower cubicle
These all feed up to a seventh spiral which forms the ceiling of the inner shower cubicle
The outer cover of the solar shower tent is made of clear polythene and so the whole tent acts as a small greenhouse. This traps and concentrates the power of the sunshine making the solar collectors more effective (as well as warming up the inside cubicle). The inside cubicle privacy curtain is made from opaque material and is hung from the outer edge of the upper spiral.
Each solar collector tent contains nearly 400m of black collector pipe.
The Service Trailer and Water Tanks
The Solar Shower Rig (of 2 or 4 units) relies on a service trailer and reserve water tanks.
Service Trailer and Water Tanks (behind trailer)
The large cylinder at the front of the trailer is the wood fired boiler. The box at the back of the trailer contains a battery pack and plumbing control system. The small cargo hold between the boiler and back box is for carrying the shower heads when on the move and firewood storage when on site.
Back Box housing the Battery Pack, Plumbing Control System and Pumps
Water from the site supply is first used to fill the reserve water tanks. From here it is pumped direct to the showers when running solar. For boiler operation a tank of hot water is made first, then this is pumped to the showers. The hot water tank can be topped up continuously if necessary.
A queue in seriously un-sunny weather, needing all day boiler operation. Kendal Calling 2010
Waste Water
Waste water collects in the blue polythene liners under the shower floors. These can be seen in the shot above showing the solar collectors. From here it gravity drains to a sump box in the ground. The sump box contains a marine bilge pump activated by a float switch. When the sump box fills up enough to activate the float switch the pump kicks in and the waste water is pumped away (up to 300m) to a collection/disposal point. There is a sump box for each pair of Units (2 Shower Tents + 2 Outside Cubicles).
Latest Developments – Timers
Up to now users have been able to shower free of time constraints. Whilst we take it as a compliment that people wish to have extended showers, it does put a strain on our ability to provide sufficient hot water and cubicles for everyone that would like to use them. Consequently we are developing timers. No mean feat for equipment that must function reliably in all weather conditions. We have opted for a system based on a 12 volt motorised valve controlled by a micro processor and switched by in infra red key fob similar to those used on car locks. An audible 2 minute warning will be given before the hot water switches off. Cold water will remain available at all times.
In practice we shall probably switch the timers off in the afternoons when we’re not so busy, allowing extended showers for those that enjoy them.
