The United States Department of Energy (DOE) has worked with partners from the gas heating and cooling industry and the power generation industry to improve energy efficiency using advanced absorption technologies, to eliminate chlorofluorocarbons (CFCs) and hyrochlorofluorocarbons (HCFCs), to reduce global warming through more efficient use of primary energy, and to reduce electric peak demand due to air conditioning loads. Key activities include ammonia-based residential and light commercial gas absorption heat pumps and chillers, advanced "hi-cool" heat pump technology, water-based large commercial chillers, and integrated energy systems that match heat driven absorption technology with power generation. Opportunities for further advancements in absorption technologies exist, particularly for expanding integration of energy systems through combined cooling, heating and power applications achieving energy efficiency approaching 80%.

This paper documents the development and validation of predictive algorithms for modeling the microturbine in a building combined cooling, heating and power (BCHP) system. The mathematical model developed in this study is based on a 30-kW natural gas-fired microturbine; however, it can be extended to encompass a microturbine of any capacity and fuel-type. Both experimental and theoretical data are being used to model the BCHP system consisting of a combined microturbine and heat-recovery components and to determine ways to improve the overall BCHP system efficiency. The purpose of this paper is to outline the basis for the development of the BCHP model and to report on progress that has been made in regards to modeling microturbine operation with thermal recovery. The basic steps being used to develop the modular structure of the BCHP system mathematical model are described, and the model developed to date has been validated by experimental data. The first step has been the mathematical modeling of the natural gas-fired microturbine. The process involved developing the thermodynamic equations that describe the polytropic processes of compression and expansion in the compressor and turbine, respectively, and developing the heat balance and mechanical energy balance equations. A linear analysis method was used to derive the equations that relate the change in the microturbine exhaust backpressure to the change in its output power and efficiency. The mathematical model was applied to the baseline performance data collected on the 30-kW natural gas-fired microturbine unit under steady-state conditions at various loads (10 to 30 kW or one-third to full output power settings, in 5 kW increments) and at various exhaust backpressures (2.7x10 to 1.7x10 atm). Under these modes of operation, the basic operating parameters (temperatures, pressures, flows, voltages, currents, etc.) and the output power of the microturbine were measured, and its energy efficiency was calculated. Without any external backpressure applied to the microturbine exhaust (damper fully open), the average measured power output ranged from 10.0 to 27.8 kW. The microturbine efficiency averaged from 18.0% to 23.0% for the one-third to full output power demand settings. With maximum externally applied backpressure (1.70x10 atm), the model shows that the output power losses (decrease in power output) due to backpressure range from 3.5% for full output to 5.5% for one-third power (lowest value of ~3% occurs at 25 kW), while the efficiency losses (decrease in efficiency) range from 2.5 to 4% (lowest value of ~2.0% occurs at 25 kW), correspondingly. The internal energy losses were calculated to be approximately 30% of the total power produced.

The United States Department of Energy (DOE) is working with partners from the gas treating and cooling industry to improve energy efficiency using advanced absorption technologies to eliminate chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), to reduce global warming through more efficient combustion of natural gas, and to impact electric peak demand of air conditioning. To assist industry in developing these gas heating and cooling absorption technologies, the US DOE sponsors the Thermally Activated Heat Pump Program. It is divided into five key activities, addressing: residential gas absorption heat pumps; large commercial chillers; advanced absorption fluids; computer-aided design; and advanced “Hi-Cool” heat pumps

The U.S. Department of Energy (DOE) is working with partners from the gas heating and cooling industry and the power generation industry to improve energy efficiency using advanced absorption technologies, to eliminate chlorofluorocarbons and hydrochlorofluorocarbons, to reduce global warming through more efficient use of primary energy, and to reduce electric peak demand resulting from air conditioning loads. To assist industry in developing these gas heating and cooling absorption technologies, DOE sponsors the Thermally Activated Technologies Program. Key activities include ammonia-based residential and light commercial gas absorption heat pumps and chillers, advanced "hi-cool" heat pump technology, water-based large commercial chillers, and integrated energy systems that match heat driven absorption technology with power generation. Opportunities for further advancements in absorption technologies exist, particularly for expanding integration of energy systems through combined heating, cooling, and power applications achieving energy efficiency approaching 80%.