External Heat Engine mCHP

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Building sector accounts for more than 60% of total energy consumption in the world, while the share of domestic buildings is about 20-40%. The energy consumed is mostly utilised for heating, cooling and ventilation purposes, contributing massively to fossil fuels consumption and thus CO2 emissions. Combined heat and power (CHP) systems generate electricity and harness the heat by-product for heating of buildings. Currently CHP systems deliver a combined efficiency of up to 80%, residential and small business bills can be reduced by 20-40%, and carbon production can be reduced by 30%. They also offer fuel flexibility, and being an independent system, reduce demand on centralised power supply and distribution systems. The current roadmap for UK CHP implementation will, by 2030, yield primary energy savings of 85-86TWh/a with a savings of 10-14Mt/a. The mCHP market is currently served by Stirling, ICE, and ORC systems, all of which have significant issues that limit wide mCHP installations. The proposed ECHP system will lead to significant energy savings (greater than 40%), CO2 emissions reduction and will be approximately 30% more efficient than current mCHP systems due to unique geometry and control system applied to the highly efficient Ericsson cycle. The ECHP will use Helium, eliminating the need for HFCs. Being an external heat engine allows the use of a variety of fuels from gas, petrol, diesel, biogas, biomass, etc. The small size and silent, vibration free operation allows renovating existing building stock where the system could be installed in constrained boiler spaces. If successful, the entirely new class of mCHP will be ideally suited for new and existing UK buildings and have: (a) high efficiency; (b) low maintenance; (c) silent and low vibration; (d) HFC free; (e) compact design; (f) implementation of a simple, consumer friendly GUI interface allowing optimal system control; and (g) use external heat source, allowing a wide variety of fuels. The proposed ECHP system is expected to have the following technical advantages: a system incorporating optimised compressor and expander geometry to approach isothermal operation, computer control of individual rotor motor-generators to optimise cycle efficiency and quicker start to operation times, system integration of combustion chamber, expander, recuperator, and compressor for maximum efficiency, and an optimized control algorithm with GUI control to create a mCHP suitable for demonstration of the theory and research development. Research will begin with description of the theoretical concept in relation to the ideal Ericsson cycle. System components will be modelled, to include various geometries. Using developed computer analysis programs and CFD, rotor design, porting, and recuperator component designs will be optimised as individual components then as an integrated system. Computer simulation models will be used to predict the thermal and electrical performance of the ECHP system. This process will perform an optimisation study of the system by taking into account the influence of different parameters of the ECHP system and power output efficiency. Changes to the parameters and components will be evaluated as required. Only when the feasibility of the system is proven, components will be fabricated and electronic control hardware/software will be developed. The components and then the complete systems will be evaluated. A lab scale 3kW ECHP will be fabricated and evaluated. The outputs of this research will validate the theoretical modelling, significantly increase the body of knowledge of external heat engines and determine the technical feasibility of the proposed concept which aims to surpass current systems efficiencies and approach Carnot efficiency.