This PVRI power system operates a GPS local location correction transmitter in a northern Minnesota mine to increase the precision of GPS equipment operating in the mine. In addition to power for the GPS receiver/transmitter, the PV power system also provides a warm environment for the equipment. The equipment must be maintained above 10°F even in the winter when temperatures are below -40°F. This is accomplished by using a vaccine refrigerator housing as the combination battery/electronics enclosure and using all available excess power to heat the batteries in the winter. The system has operated without problem for 10 years.