Swimming Pools are an ideal application for the use of Solar Thermal Heating. As your pool will be typically used in the summer, the power that can be obtained from the sun's radiation is at it's maximum.
Typically swimming pools are expensive to heat due to the vast volumes of water involved and the latent heat properties of water. Once your pool is up to temperature you can switch off your boiler and rely on the solar collectors to maintain the water temperature in your pool.