Abstract: A system for converting potential energy into heat including a tower configured to contain a fluid and to permit the formation of a substantially nitrogen-free combustion chamber defined by the tower and the surface of the fluid in the tower and at a pressure less than ambient, a first tower outlet in fluid communication with a first fuel valve configured to regulate a flow of the fluid out of the tower, an oxygen source in fluid communication with an oxygen valve in fluid communication with an oxygen inlet in fluid communication with the tower, a source of combustible fuel including hydrogen in fluid communication with a fuel valve in fluid communication with a fuel inlet in fluid communication with the tower, and an ignition source positioned so that it resides within the combustion chamber and is configured to initiate a reaction between oxygen and fuel.