Joule Acapella tube kits are a high performance solar tube systems. The tubes are designed to be mounted on-roof over the roof tiles. The tubes have an alcohol liquid inside the glass tube. The alcohol transfers its heat into the system fluid through a copper bulb at the top of the tube. The heat in the solar fluid then moves down the solar pipework into the coil in the cylinder. The Acapella tube systems tend to produce more hot water compared with standard flat panels due to the increased insulation of the vacuum and the lower boiling point of the alcohol. The increased performance must be closely matched against the hot water load of the property. If the additional hot water is not being consumed by the property and there is not a suitably designed heat dump the system will over stagnate and possibly air lock.