Vacosol are ultra high-performance solar panels for producing very hot water, even when the sunlight is only measuring a low intensity. These two reasons are what make Vacosol the panel of choice for solar heating systems. They cannot however be used in drainback systems. They must only be used as part of a pressurised system with an expansion vessel. This type of solar panel uses double-walled evacuated borosilicate tubes measuring 47 mm in diameter and 1.5 m long.
