My panels work best for the heating of swimming pools of between 20,000 and 50,000 litres, with a reasonable quality pool cover fitted to limit over night heat loss and the use of one panel for every 5,000 litres of pool water.
Each panel raises the temperature of the water flowing through it by 3 - 4°C at a flow rate of 5 litres per minute. This is with the swimming pool water temperature at under 25°C, and the outside air temperature also at under 25°C.
The panel lies flat on a roof or in a garden, has an aperture area of 0.9 M2 and has a plastic dome cover design incorporating a concave/convex feature to maximise sunray intake at all times of the day. Virtually the whole panel and tubing is made from plastic making it cheap to produce. The Patent has now been approved.
Over an 8 hour period each panel will produce 2,400 litres of 3 - 4°C warmer water which is fed back into the pool. My theory is that it is better to feed back a large volume of warm water rather than a small quantity of hot water back into the pool.
For a 30,000 litre pool, up to 6 panels would be used heating up to 14,400 litres of pool water, or basically half of the pool volume per day will have flowed through the panels and returned back to the pool. The amount of panels used would depend on the location and what pool temperature is required by the individual. The amount of panels installed could be added to at a later date if required.
My suggestion of using 1 panel (approx 1m2) per 5000 litres of pool water and circulating the water for 8 hours per day is based on maintaining the pool temperature at a minimum of 28°C in the winter months, in a climate such as this in Lanzarote. For probably 4 – 6 months of the year this can be achieved by using a good quality pool cover alone, or by having some form of gas or electric heating system on for just a few hours per day. As my system is fully sealed and insulated against the elements it is not affected by the cold wind chill factor in the winter months so will work efficiently all year round.
My system would be 100% solar as no extra electricity would be used due to the existing circulatory pool pump being used to circulate the water through the panels.
Over 5 days or so the pool gradually increases in temperature, at around 1°C per day, and providing the pool cover is fitted overnight, a percentage, although relatively small, of the heat will be retained.
I have heated my pool to over 38°C, which is obviously far too hot, for no extra cost other than the price and fitting of the panels. The panels will also be very cheap to manufacture and easy to install as they lie flat on the ground or on a roof. On a flat roof they are invisible from ground level.
I have only used basic existing formulas to calculate efficiencies and power output of the panels, so if the maths don`t add up I apologise. All of the figures stated are arrived at by my own testing. My calculations suggest that each panel is capable of producing over 1.2kw per metre squared with an efficiency rate of 70% with an outside ambient temperature of under 25°C.
I am in the process of doing some final tweaking and testing, which should improve the performance even more, and should have some more accurate figures and a short video available shortly.
It would be nice to get an experts view on my theories.
I agree with you that a small temperature increase of good flow rate is the way to go.
I'm wondering why your unit is so deep as I imagine only the coils that I see on the top are active ?