1. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment Advanced Cycles and Replacement Working Fluids in Heat Pumps John McMullan Energy Research Centre University of Ulster Thematic Group 3 Contract JOE3-CT95-0009 Enerbuild Participant No. 49 Project Acronym AHP-NH3

2. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment THE HEAT-PUMP Vapour compression cycle Absorption cycle

3. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment BACKGROUND CFCs have already been banned under the Montreal Protocol HCFCs are scheduled for removal between now and 2010-15 HFCs are substitutes, but only as mixtures and only on an interim basis. They are under threat because of global warming Natural refrigerants (CO2, ammonia, propane/butane) offer an alternative route, but CO2 involves very high pressures Tc = 31 C, Pc = 73.8 bar Ammonia is flammable, toxic, corrosive, and pressures are high for heat pump applications (however, see later) Hydrocarbons are very flammable, but otherwise very good Refrigerant mixtures introduce lubrication and fluid separation problems

4. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment OBJECTIVES To develop the use of refrigerant mixtures in buildings and in industry at higher temperatures To determine the properties of mixture working fluids To consider the application of Lorenz cycles To develop the ammonia-water resorption cycle To develop a smart control to adjust mixture composition to match the operating conditions Both synthetic and natural refrigerants are considered. In buildings, the aim is to achieve high seasonal performance. In industrial food and drying processes, the aim is to develop equipment for operation at application temperatures up to 120 o C

5. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment LORENZ CYCLE

6. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment PROGRESS IN REFRIGERANT MIXTURES Interaction of refrigerant mixtures and lubricants quantified Smart controller principle established (see later) Property calculations established and verified Lorenz cycle possibilities evaluated using R407C – especially, plan developed for implementation in a food processing plant Project has led to a CRAFT contract on R410A and underfloor heating Further proposals to UK EPSRC on smart control, and on viability of renewable energy driven heat pump systems

7. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment AMMONIA-WATER RESORPTION CYCLE

8. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment AMMONIA-WATER RESORPTION CYCLE This has interesting possibilities as the heat of solution is added to the latent heat of evaporation and the compressor work before passing to the condenser (resorber) The work has demonstrated that the system works, that the compressor can tolerate the corrosive ammonia-water mixture and that good COPs can be achieved. The test bed has been used to raise low pressure steam for extended periods of time The plant has the potential to provide low temperature heat with very large coefficients of performance

9. Energy Environment & Sustainable Development Thematic Network on Energy in the Built Environment CONCLUSION The project has demonstrated problems and opportunities in the use of new heat pump cycles and working fluids It has demonstrated the principle of a method for adjusting mixture compositions to the needed values – either for operation or for system maintenance It has led to further proposals which are a step nearer the market place It has opened up collaboration opportunities (e.g. through CRAFT) It has developed a mass of detailed and necessary information for the proper implementation of heat pumps in buildings and industrial applications.