APPLICATION OF TURBOMACHINERY IN SOLAR-ASSISTED RANKINE COOLING SYSTEMS
This report presents the results of a preliminary study concerning the use of high speed turbomachinery in a solar-assisted Rankine cooling cycle. The use of Rankine cycles in solar powered cooling of buildings involves a solar collector to provide energy to heat and vaporize a working fluid. Energy is extracted from this vapor in an expansion engine that is used to drive an air conditioning vapor compressor. In a typical Rankine cycle, the maximum temperature at the inlet to the expander is limited to the temperature of the fluid leaving the solar collector. Because of the relatively low temperature capability associated with inexpensive collectors the efficiency of the Rankine cycle is generally low. This low efficiency results in low coefficient of performance values for the solar powered cooling system. In an effort to improve Rankine cycle efficiency, a solar-assisted approach was presented in NSF report RA-N-75-012, by Dr. Henry Curran. In this approach solar energy vaporizes the working fluid at a low temperature using solar collectors; the vapor is subsequently superheated to a higher temperature using fossil fuel, thereby allowing the potential of much improved Rankine cycle efficiency as compared to a typical cycle. Water was selected as the working fluid to avoid problems associated with chemical stability of organic fluids at high values of expander inlet temperature. A maximum steam temperature of 1100 F was suggested to achieve Rankine cycle efficiencies on the order of 25%. The solar-assisted Rankine cycle was shown by Dr. Curran to offer a substantial cost advantage over conventional absorption machinery. Key elements in achieving this performance improvement are the efficiency of the Rankine cycle vapor expander and the performance of the vapor cycle. In Dr. Curran's study, an expander efficiency of 82% and an air conditioning COP{sub vc} of 4.0 was assumed. Additionally, no losses were included for drive efficiency, implying a direct drive between the vapor expander and the air conditioning compressor. The intent of the present study was to identify the performance potential of practical turbine expanders and vapor compressors, and provide preliminary definition of the hardware. The remainder of this report presents the results obtained during this study.
- Research Organization:
- Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
- Sponsoring Organization:
- Environmental Energy Technologies Division
- DOE Contract Number:
- AC02-05CH11231
- OSTI ID:
- 993486
- Report Number(s):
- LBL-6852
- Country of Publication:
- United States
- Language:
- English
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