Ericsson Cycle Heat Engine

About

Summary A revolutionary Ericsson cycle heat engine was developed through an Innovate UK Energy Catalyst R3 Feasibility Study. This proof of concept showed what is possible for the system as a heat pump and external heat engine. The system is now being developed as a micro-Combined Heat and Power system in as part of a three-year development program. The unique geometry and dynamics of the system will allow a new level of performance in heat pump applications such as both mobile and fixed refrigeration, coolers, and air -conditioning. As an external heat engine, applications include low grade waste heat, mCHP, mCSP, and generators. The unique geometry with an unsurpassed heat exchange are to volume ratio allow compression and expansion to approach isothermal heat exchange. The simple system has only four moving parts with motor-generators directly driving the rotors. This arrangement eliminates mechanical drive elements and allow full control over the cycle, allowing a greatly increased operating range. Project Status The one-year Innovate UK project came to an end in November 2016 with the most basic of systems confirming the feasibility of the concept. The concept is to first be developed as an external heat engine version as a mCHP system being developed. This 3-year EPSRC project will continue development to include extensive thermodynamic modeling of the system and rotor dynamics. While this system is aimed at mCHP parameters, the same system will be used to demonstrate capabilities as a low-grade waste heat to power system. Concurrent development as a heat pump system is being coordinated at this time, allowing the system to be demonstrated as a small fixed refrigeration system with applications for small commercial units and mobile refrigeration systems. This development will also include motor-generator system optimized for this application, increasing efficiency and greatly reducing the end product cost of the system. Description The Ericsson cycle, in its ideal form, achieves Carnot efficiency, the higher physically possible of a machine/system. While the Ericsson system was developed in the 1800’s, few examples have been made since the cycle requires the complication of valves. The systems that were made proved superior, yet steam turbine and then internal combustion engines became prominent – although much less efficient. The Stirling cycle system was developed about the same time as the Ericsson, and has seen examples throughout the years. It is similar to the Ericsson in that, in the ideal form, can achieve Carnot efficiency and is a closed cycle system, using benign fluids such as nitrogen, or H2, He. Most important, the cycles are reversible, meaning they can operate as heat pumps and as external heat engines. Unfortunately, the Stirling systems include many technical issues and require high cost materials, making their efficiency and commercial success very much less than the ideal potential and unviable for most markets. The developed Ericsson system uses two pair of rotors, creating a valve-less system of compressor and expander, connected by a simple counter flow heat exchanger. This system overcomes all of the pitfalls of the Stirling concept and development shows will be about 30% more efficient than current system. Being a reversible cycle, the system will be applicable to