Efficiency of MicroCHP systems under transient operation

More and more mini and micro cogenerationsystems appear on the market of residentialheating appliances and home owners have todecide weather such a system is an option fortheir building or not.One of the key questions that has to beanswered prior to the decision to invest in acombined heat and power (CHP) system is theeconomic situation and connected to this is theperformance of the system.The goal of this contribution is to work out therelation between the heat and electricity outputof a micro CHP system and its efficiency. Theapproach towards this is to analyse data derivedby test bench experiments and a field measuringcampaign.First results show a significant influence of thedaily heat demand on the CHP efficiency. Forthe systems tested on the test rig, a simplelinear approach led to a very good correlationbetween electrical and thermal efficiency andheat output of the CHP unit.This approach does not work for the Stirlingsystems of the field-test because Stirling engineand auxiliary burner are integrated into onesingle heating appliance and could not bemeasured separately.Next steps will be to improve the regression curvesby adding further parameters and analysingmeasured data with high timely resolution.