Modelling, experimentation and simulation of a reversible HP/ORC unit to get a Positive Energy Building Olivier Dumont, Carolina Carmo, Sylvain Quoilin and Vincent Lemort Thermodynamics laboratory, University of Liege, Allée de la decouverte, 17 (B 49), 4000 Liege (Belgium), contact : olivier. dumont@ulg. ac. be ABSTRACT EXPERIMENTAL RESULTS This paper presents an innovative building comprising a heat pump connected to a solar roof and a geothermal heat exchanger. This unit is able to invert its cycle and operate as an Organic Rankine Cycle (ORC). The solar roof is producing large amount of heat throughout the year. This allows covering the building annual heating needs and, furthermore, electricity is produced thanks to the surplus of heat in a so-called HP/ORC reversible unit. This paper focus on these three main points: sizing, experimentation and simulation of the reversible unit. First, an optimal sizing of the components and fluid R 134 a shows promising performance with a net electrical energy produced over one year reaching 4030 k. Wh. Following that, a prototype has been built and has proven the feasibility of the technology. Finally, a simulation code xchanger, the building, the ground heat thermal energy storage, thesolarroofandthereversible. HP/ORC unit is developed and allows to perform a that this technology leads to a Positive Energy Building. • Experimental investigation of the HP/ORC prototype with refrigerant R 134 a. • Proof of the feasibility of such a reversible unit with encouraging performance. • First scroll unit used as an expander and as a compressor in the same application. Mode ORC HP Parameter Theoretical point Evaporation pressure [bar] 33 Condensation pressure [bar] 7 Electrical power [k. W] 5. 9 Global efficiency [%] 7. 5 Expander isentropic efficiency [%] 68 Evaporator pressure [bar] 5 Condensation pressure [bar] 17 Electrical power [k. W] 4 COP [-] 4. 25 Compressor Isentropic efficiency [%] 69 Experimentation 32 10. 3 3. 7 4. 2 58 5. 7 17. 3 3. 8 4. 21 76 Comparison of theoretical nominal point and experimentation ANNUAL SIMULATIONS CONCEPT • Innovative system with a reversible heat pump that can work as an ORC is connected to a solar roof (120 m 2) and a geothermal exchanger (300 m long) • Direct heating mode : Building heating needs covered by the solar roof. • ORC mode: Generation of electricity with the surplus heat generated by the roof. Heat from the roof evaporates the refrigerant that generates electricity in the expander. Then the refrigerant is condensed thanks to a geothermal hose before going into the pump and starts the cycle again. • HP mode: Used when wheater conditions do not allow using direct heating. Heat from the roof evaporates the refrigerant before going in the compressor. Then it is condensed and it releases its heat in thermal heat storage trough the condenser. After that, the refrigerant goes into the expansion valve and starts the cycle again. • Annual simulations with Modelica/Dymola coupled with Thermocycle/ Cool. Prop • Annual simulation of the optimal sized unit over a whole year (time step = 900 s) with sub-models: building, ground heat exchanger, thermal energy storage, solar roof and reversible HP/ORC unit. • Inputs : occupant behavior & meteorological conditions • Control strategy optimizing the electrical production while covering heat demand Output Ancillaries consumption Heat pump consumption Gross electrical production Net electrical production Heating requirements (heat) Annual energy [k. Wh] 1491 812 2970 667 4403 Direct heating (heat) 1394 Performance in the basic study case (Denmark, single family house, 500 L storage) • Positive Energy Building: Net electrical production while covering heat demand. • 30% decrease of heat pump consumption thanks to the Direct Heating mode. • Optimum location around Torino. Hydraulic scheme of the unit : 3 operating modes SIZING • Optimization of heat exchanger size, expander size, working fluid (R 134 a) and pump. • Net yearly electrical power generation is optimized over its whole operating range instead of just nominal sizing operating conditions. Simulated performance with 5 typical European climates CONCLUSIONS • Innovative reversible HP/ORC system, allowing both heat and electricity production • Modeling allow evaluation of yearly performance Proof of theoretical interest. • Encouraging experimentation results Proof of technical feasibility. • Assessment of annnual performance with different inputs and parameters Open source paper orbi. ulg. ac. be Monthly performance of the reversible unit University of Liege – October 2015 Dumont O, Carmo C, Quoilin S, Lemort V Applied thermodynamic laboratory aerospatial et mechanical department, Sart Tilman B-4000 LIEGE Contact : olivier. dumont@ulg. ac. be
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