Experimental and Theoretical Study of Microturbine-Based BCHP System
On-site and near-site distributed power generation (DG), as part of a Buildings Cooling, Heating and Power (BCHP) system, brings both electricity and waste heat from the DG sources closer to the end user's electric and thermal loads. Consequently, the waste heat can be used as input power for heat-activated air conditioners, chillers, and desiccant dehumidification systems; to generate steam for space heating; or to provide hot water for laundry, kitchen, cleaning services and/or rest rooms. By making use of what is normally waste heat, BCHP systems meet a building's electrical and thermal loads with a lower input of fossil fuel, yielding resource efficiencies of 40 to 70% or more. To ensure the success of BCHP systems, interactions of a DG system-such as a microturbine and thermal heat recovery units under steady-state modes of operation with various exhaust back pressures-must be considered. This article studies the performance and emissions of a 30-kW microturbine over a range of design and off-design conditions in steady-state operating mode with various back pressures. In parallel with the experimental part of the project, a BCHP mathematical model was developed describing basic thermodynamic and hydraulic processes in the system, heat and material balances, and the relationship of the balances. to the system configuration. The model can determine the efficiency of energy conversion both for an individual microturbine unit and for the entire BCHP system for various system configurations and external loads. Based on actual data Tom a 30-kW microturbine, linear analysis was used to obtain an analytical relationship between the changes in the thermodynamic and hydraulic parameters of the system. The actual data show that, when the backpressure at the microturbine exhaust outlet is increased to the maximum of 7 in. WC (0.017 atm), the microturbine's useful power output decreases by from 3.5 % at a full power setting of 30 kW to 5.5 % at a one-third power setting (10 k w), while the efficiency of the unit decreases from 2.5 to 4.0%, accordingly. Tests on the microturbine were conducted at the Cooling, Heating, and Power Laboratory set up at the Oak Ridge National Laboratory's Buildings Technology Center. Data were collected from the microturbine at power demand settings of 30 kW (full load) to 10 kW in 5-kW increments. For each power demand setting, data measurements were taken over an entire range of microturbine exhaust back pressures. The parameters measured were engine speed, ambient air temperature, air temperature at the microturbine inlet, gas temperature at the turbine outlet, exhaust gas temperature, throttle pressure loss, flow rate of natural gas, and composition of combustion products. The mathematical model provided gas temperature before the turbine, compression rate, and air flow rate, which were determined based on the measured data The results of these early tests and the computer-based simulation model are in very close agreement.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- US Department of Energy (US)
- DOE Contract Number:
- AC05-00OR22725
- OSTI ID:
- 786334
- Report Number(s):
- P01-111290; TRN: US200203%%82
- Resource Relation:
- Conference: 2001 ASME International Congress and Exposition, New York, NY (US), 11/11/2001--11/16/2001; Other Information: PBD: 12 Jul 2001
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
29 ENERGY PLANNING
POLICY AND ECONOMY
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
AIR CONDITIONERS
AIR FLOW
COMBUSTION PRODUCTS
ENERGY CONVERSION
FLOW RATE
FOSSIL FUELS
HEAT RECOVERY
MATERIAL BALANCE
MATHEMATICAL MODELS
NATURAL GAS
POWER DEMAND
POWER GENERATION
SPACE HEATING
WASTE HEAT