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09:00   New applications: Domestic CHP
Chair: Dr. John Harinck
20 mins
Kuanrong Qiu, Erik Horsteinson, Skip Hayden
Abstract: Micro-combined heat and power (micro-CHP) is an effective approach to achieving high energy efficiency for buildings. Rising energy costs, volatile fuel prices, electricity blackouts and increasing environmental concerns have accelerated acceptance of the micro-CHP concept. Micro-CHP is particularly attractive for areas with a long heating season and remote communities where connection to the grid is not cost-effective. Micro-CHP appliances are beginning to emerge. In this paper, a prototype organic Rankine cycle (ORC)-based micro-CHP system was investigated for use in residential buildings. The ORC uses an organic fluid as the cycle working medium. Its advantages include clean and automatic operation, low maintenance, enhanced part-load characteristics and long lifetime. The micro-CHP system provides not only its function of electricity generation, but also space heating and hot water production for an individual dwelling on site. The ORC studied in this work consists of a gas combustion chamber, evaporator, scroll expander, condenser, organic fuild pump and a regenerator. The ORC produces shaft power that runs a generator in the integrated micro-CHP system. Besides, the shaft power may directly drive the compressor of a cooling system. This method could find applications in certain situations. The experimental micro-CHP unit has an electric power capacity of 1.2 kW and can rapidly start up and shotdown. The integration of this micro-CHP unit with a home heating system was explored as well. An overall system efficiency of 90% could be achieved. The values of such an integrated system provided to the consumer would be both the heating system reliability and a reduction in electric power consumption. Thermodynamic calculations of the ORC were made to determine the systems’ performance under various conditions. Overall power outputs and energy conversion efficiencies have been obtained using the established model.
20 mins
James Freeman, Klaus Hellgardt, Christos Markides
Abstract: Small-scale solar thermal technologies for cogeneration of heat and power present the possibility of a versatile and cost-effective alternative to photovoltaics for the domestic market. Optimization of system performance is essential in order to extract the maximum work potential in locations of low solar resource such as the UK and northern Europe. A model is presented of an indirectly heated solar organic Rankine cycle system for the production of electricity and hot water; along with the results of initial performance simulations in which the flow-rates for the solar collector and ORC working fluid circuits are fixed at constant values. An optimization of the solar collector flow and return temperatures is conducted in order to maximize exergy production from the collector for a given incident solar irradiance value. Improvements are then made to the system model by introducing variable speed control of the collector and working fluid flow rates in order to track the optimum flow and return temperatures to the collector. Annual electrical output from the cycle is found to increase by 8% relative to the fixed flow rate model.
20 mins
Tomasz Z. Kaczmarczyk, Eugeniusz Ihnatowicz, Sebastian Bykuć, Grzegorz Zywica, Zbigniew Kozanecki
Abstract: In order to meet the directives and the trends indicated by the European Union concerning the systems using renewable energy sources, in the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences in Gdańsk, the idea of constructing a domestic micro power plant appeared. The first investigation of the ORC system was conducted with the use of an expansion valve simulating an expander (microturbine). In the next step, we constructed our own micro steam turbine for the domestic ORC system. The heating cycle has two heat sources that can work independently or in series. The first one is a multi-fuel boiler and the other heat source is a prototypical electric flow heater. The prototypical electric flow heater is designed to heat non-conductive fluids (thermal oil) to the temperature of about 250oC with a low power flow density and the power of 2x24 kW. The prototypical boiler enables combustion of gas fuel (town gas or gas from biomass gasification) or solid fuel in the form of biomass (pellets). The nominal boiler power in biomass combustion (pallets) is around 40 kW. The cooling system of the ORC installation performs two tasks. First, it enables cooling of the thermal oil coming to the evaporator and hence increases the range of adjustment of oil temperature. The other important task of the cooling system is quick cooling of the working medium (HFE 7100) vapour in the condenser (plate exchanger), in a way to obtain the liquid of the temperature of 65oC at the inlet of the circulating pump of the working medium. Four circulation pumps using HFE 7100 as the working fluid were analysed. Namely two commercial pumps (peripheral and gear pumps) and two prototypical pumps of our design (a pitot tube pump and a vortex pump). The ORC system cooperates with a high-speed four-stage radial microturbine whose parameters are as follows: nominal power of 3 kW, nominal rotational speed of 23 800 rpm and isentropic efficiency of about 84%. The turbine shaft is integrated with an electric energy generator and encased in a sealed housing. Given the air-tight construction and the high rotational speed, aerostatic gas bearings powered by a low-boiling medium vapour were used. The microturbine is equipped with a control and measurement system which assures good functioning of the device as well as reception and conditioning of electric energy. The paper presents the results of the experimental investigations of a regenerative ORC system using two heat sources (a multi-fuel boiler and an electric thermal oil heater), equipped with a microturbine and an expansion valve. Acknowledgements The work presented in the paper has been funded from a National Project POIG.01.01.02-00-016/08 Model agroenergy complexes as an example of distributed cogeneration based on local renewable energy sources.