The market for domestic, micro-scale combined heat and power systems is expanding rapidly worldwide. The current small- and micro CHP offering is generally based on the established and proven technology of Stirling or internal combustion (IC) engines. Stirling engine systems are hindered by poor electrical efficiencies at small scale. (Current commercially available systems have around 12% efficiency at 1 kW output power.) Internal combustion engines can provide much better efficiencies (above 20% at 1 kW electrical power output), but suffer from noise and vibration, in addition to higher emissions levels. Both these systems further suffer from high manufacturing costs, resulting in long payback periods even with governmental incentives.
The proposed system provides a radically new concept for small- and micro-scale combined heat and power generation, based around an external combustion, reciprocating Joule cycle (RJC) system. The RJC engine has been studied by a number of researchers with very promising results, however the energy converter in previous systems has been based on conventional, crankshaft engine technology, unable to provide the required conversion efficiency.
In order to realise the full potential of the RJC engine, the proposed system uses a double-acting free-piston engine power converter with high operational flexibility and extremely low mechanical losses. Both reports from other authors and studies done at Newcastle University have suggested that efficiencies higher than those of current IC engine system can be obtained while maintaining the advantages of a mechanically simple system. Due to the external combustion, fuel flexibility and emissions levels will be very low and comparable to those of current Stirling engine systems.
Through the use of an efficient thermodynamic cycle and low engine frictional losses, the free piston CHP concept can achieve a fuel economy superior to that of conventional technologies, improving the viability of micro-scale CHP system technology and giving significantly reduced CO2 emissions.
First proof of concept prototypes have been developed and the second generation prototype will be completed later this year (2012). We are now looking for potential investment and commercial collaborators/partners to assist taking the proof of concept closer to commercialisation. This technology can be used for a number of applications and specifically could be an alternative to conventional boiler or to any stationary CHP systems. Taking advantage of government energy incentives a payback time of three years or less is potentially achievable.
Intellectual Property Status
This technology is protected by patent applications currently being examined at national levels.
Title: Heat Engine (micro CHP)
Europe: patent application no. 10714669.8
United States: patent application no. 13/263,153
China: patent application no. 201080015873.X
Other related patent applications
Title: Free-piston internal combustion engine
PCT: publication no. WO2011144926
UK: patent application no. GB1008319.4
Title: Combustion ignition free-piston internal combustion (HCCI)
UK: patent application no. GB1120106.8 (app date: 22 Nov 2011)
Dr Jayshree Johnstone, Science, Agriculture & Engineering Enterprise Team, Research and Enterprise Services, Second Floor, Devonshire Building, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK