A new type of nonsalt solar pond was investigated by held testing. The roof of the solar pond was formed using a transparent double him. Three kinds of tests were carried out under the following conditions: (1) insulating pellets were packed between the layers of the transparent double film of the roof at sunset; (2) the water surface of the pond was insulated using only the two transparent films; (3) the water surface of the pond was covered by the double film with the top surface blackened on which solar energy can be collected, while pond water was circulated using a solar cell powered submerged water pump. The warm water stored in the solar pond by the above methods was utilized as a heat source for a gas engine powered heat pump used to heat a greenhouse. In this report, the results of the field tests on the above solar ponds and greenhouse heating system are discussed. Also the utility of a combination plant using a solar pond and underground borehole storage system is evaluated. Important conclusions on performance are as follows: (1) collection efficiencies of these solar ponds become 9-54% corresponding to the weather conditions and pond temperatures; (2) maximum temperature of the pond water under weather conditions at Osaka is about 80 degrees C; (3) the solar pond can be effectively utilized for heating a greenhouse; (4) the combination plant using the solar pond and the underground storage layer can store heat of 1119 MJ m(-2) yr(-1).