A unique high-temperature thermal energy oil and rock storage system is utilized for a commercial office building solar heating and cooling system. Over 1880 m (20,250 ft ) of trough-type concentrating collectors track the sun's elevation and supply solar energy at fluid temperatures up to l76C (350F). The solar system provides over 80% of the annual cooling enengy, 50% of the annual heating energy, and 100% of the domestic hot water for the eight-story 9,290 m² (100,000 ft ²) office building located in Minneapolis, Minnesota. The system was dedicated and began operation in November 1978.