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Solar Powered Refrigeration SystemA solar powered vapor compression refrigeration system is made practicable with thermal storage and novel control techniques. In one embodiment, the refrigeration system includes a photovoltaic panel, a variable speed compressor, an insulated enclosure, and a thermal reservoir. The photovoltaic (PV) panel converts sunlight into DC (direct current) electrical power. The DC electrical power drives a compressor that circulates refrigerant through a vapor compression refrigeration loop to extract heat from the insulated enclosure. The thermal reservoir is situated inside the insulated enclosure and includes a phase change material. As heat is extracted from the insulated enclosure, the phase change material is frozen, and thereafter is able to act as a heat sink to maintain the temperature of the insulated enclosure in the absence of sunlight. The conversion of solar power into stored thermal energy is optimized by a compressor control method that effectively maximizes the compressor's usage of available energy. A capacitor is provided to smooth the power voltage and to provide additional current during compressor start-up. A controller monitors the rate of change of the smoothed power voltage to determine if the compressor is operating below or above the available power maximum, and adjusts the compressor speed accordingly. In this manner, the compressor operation is adjusted to convert substantially all available solar power into stored thermal energy.
Document ID
20020089464
Acquisition Source
Johnson Space Center
Document Type
Other - Patent
External Source(s)
MSC-22970-3
Authors
Michael K Ewert
(Johnson Space Center Houston, United States)
David J Bergeron, III
(Johnson Space Center Houston, United States)
Date Acquired
August 20, 2013
Publication Date
September 24, 2002
Subject Category
Solid-State Physics
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.
Patent
US-Patent-6,453,693
Patent Application
US-Patent-Appl-SN-838680
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