Found the filtration system we want - Ionclean by Parkinson using an Amp Dolphin Ioniser negating the need for large amounts of chlorine. This will be combined with a solar heating system and solar powered pump. This system can be designed in England by a company called Fieldway. Avoiding chlorine is our top priority - it is a toxic gas and was used by the Germans in the 1st World War. It makes your eyes sting, if you breathe in too much your lungs suffer. It corrodes metals and rots clothing. The greatest concentration of the gas in a pool is on the surface of the water which is where you breathe if you are swimming. Imagine a professional training 5 hours a day - you won't be surprised to learn that the Americans have used Ag/Cu ionisation in their training pools for years. Children with any tendency to ashthma should keep clear of chorinated pools. Some American research has shown that cancer of the bowel can be attributed to chlorine. In the West most people drink it in their water intake. This is at too low a level to do you any harm but it tastes horrid, hence bottled water and the use of carbon water filters.
In a hot climate the chlorine in a pool soon diminishes due to 'out-gassing' so you need to measure it constantly and top it up. Sometimes the chlorine is made by using a salt generator. The name is misleading. They use salt (sodium chloride) to generate Chlorine.
The best alternative, without spending a fortune is silver/copper ionisation. Positively charged ions of silver disable the deleterious bacteria (negatively charged) while the copper causes the algae to flocculate into bunches which get removed by a sand filter through which they would normally pass unscathed.
Here endeth the lesson for today.