Domestic combined heat and power unit
A DCHP unit with a Stirling engine ( 1 ), a burner ( 3 ) and a supplementary burner ( 11 ). Water is heated by exhaust gas from the Stirling engine and from the supplementary burner. If a sensor ( 18 ) detects that the water temperature has risen indicating that there is insufficient demand for the heat in the exhaust gas, a fan ( 15 ), ( 20 ) which normally provides the flow of air to the supplementary burner is operated without firing the burner to generate a flow of cool air to cool the water.
1. A domestic combined heat and power unit comprising a Stirling engine having a burner to input heat energy into the engine head to drive a reciprocating member, the reciprocating member producing electrical power output via an alternator; a heat exchanger in which fluid receives heat from exhaust gases from the burner; A supplementary heater to heat the fluid in the heat exchanger; and a fan to generate a hot gas stream from the supplementary heater through the heat exchanger; characterised by a controller which detects when the heat generated by the Stirling engine exceeds a predetermined demand and operates the fan without operating the supplementary heater to generate an unheated air stream through the heat exchanger.
2. A unit according to claim 1 , wherein the fan additionally generates a flow of air to the Stirling engine burner and a splitter valve is provided to control the amount of air fed to the Stirling engine burner and supplementary heater.
3. A unit according to claim 1 , wherein a second fan provides an air flow to the Stirling engine burner.
4. A unit according to claim 1 , wherein the controller is part of a control system for the engine.