Testing a 50kW ORC at Different Heating and Cooling Source Conditions to Map the Performance Characteristics 2013-01-1649
In 2007 the electrical power consumption of 180 rural Alaska villages was 370,000 MW-h, generated using isolated diesel gensets. From a stationary diesel engine considerable amount of heat energy at an elevated temperature is released into the atmosphere from engine jacket liquid and exhaust gases. In rural Alaska, due to the infrastructure, economic impact and needs of the villages, many of village gensets may not be appropriate for applying heat recovery for the purposes other than electrical power generation. Other appropriate types of heat recovery applications in Alaska may include desalination, refrigeration, and district heating. Also due to the varying sizes and electrical loads of most of the diesel gensets (from 100 kw to 1 MW); small-sized heat recovery power systems (80 kW or less) are preferred instead of industrial scale systems. In typical village diesel genset application most likely waste heat source could be the hot liquid from engine jacket and/or from exhaust-to-liquid heat exchanger. In the present work performance test was conducted on a 50 kW ORC power unit under different heating and cooling conditions. The experimental setup consists of heat source loop, heat sink loop, electrical system and instrumentation (for data collection) for testing the ORC power unit. The ORC power unit was tested for hot water supply (heat source) temperatures varying from 68.3°C (155°F) to 107.2°C (225°F) and flow rate varying from 27.2 m₃/hr (120 gpm) to 68.1 m₃/hr (300 gpm); cold water supply (heat sink) temperatures of 10°C (50°F) and 20°C (68°F) and flow rate varying from 27.2 m₃/hr (120 gpm) to 45.4 m₃/hr (200 gpm). The performance test results will be used to make performance maps for ORC system which are in form of system characteristic plots for efficiency, operating power output, parasitic pump power consumption, etc., with respect to different heating and cooling conditions. The data can be used in predicting long-term electrical power generation, efficiency, fuel savings, economic benefit (i.e., payback period) for a given heating and electrical load patterns. In addition emissions and CO₂ (GHG) reductions can also be estimated based on ORC electrical energy generation and fuel savings. If the ORC power unit is to be installed to recover waste heat from village diesel engines, it should be noted that power unit performance varies due to electrical load pattern, heat energy pattern, environmental conditions (e.g., for cooling source), infrastructure availability from village to village. The performance maps also provide power plant personnel with information that may be used in heat distribution for different heating and cooling conditions to optimize the benefit obtainable from diesel power plant waste heat. Different waste heat distribution applications may include heating, power, refrigeration, etc. With the help of village power plant data an example is given in this paper for predicting the electrical power generation, efficiency, economic benefit, etc., using the developed performance maps.