Solar water heaters for a simple hot water supply system create excess thermal energy in the hot summer season. To utilize this excess energy, solar air conditioning is proposed. By testing the performance of a set of solar thermal collectors consisting of vacuum insulated glass tubes, this study investigates the year-round feasibility of the collectors for desiccant cooling system in northern part of Japan. The test finds that the maximum temperature at the outlet of the collectors exceeds 70 deg. C from June to October, the level that is adequate for the desiccant cooling system. However in winter season, it also finds that lower amount of solar radiation provides lower heat gain thus the efficiency of the collector come down and solar heating system may not work.