Cone Rock Bed Thermal Energy

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Brief Description: This invention relates to a thermal energy storage facility in the form of a rock bed cone that is efficient and inexpensive compared to previous rock bed storage facilities. Target Market: Concentrating solar power plants Combined cycle power plants Thermal energy producers Solar heat and drying applications Industrial and commercial energy efficiency Value Proposition/Benefits: The thermal energy storage facility allows stored thermal energy to be recovered during periods of low energy production, for example, at night or during cloudy weather in the case of concentrated solar power plants. Furthermore, the system is designed for extreme low total cost as the construction and maintenance costs are minimal and the materials can be sourced locally. Thermal expansion and contraction causing the “ratcheting effect” does not impact the performance of the system. Unique Characteristics: Simple construction Low cost Easy maintenance, particularly in comparison with alternative thermal energy storage systems. Technical Description: The innovation is a type of thermal energy storage system which can be used to store solar thermal energy captured by a concentrating power plant. The energy absorbing material used in this thermal energy storage system is rock (granite, dolerite or gneiss). The rock particles are packed in a large pile and allowed to settle undisturbed at the natural angle of repose forming a cone-like structure. A hollow steel or concrete shaft at the centre of the rock bed is used as an air inlet/outlet to the thermal energy storage system. The shaft is divided into two sections. The top section has a solid wall and the bottom section is perforated. The perforated portion allows the air to pass from the central shaft to the rock bed. In this way heated air can be passed through the shaft and into the base of the rock bed from where it radiates outwards heating the surrounding rock particles. Reversing the direction of air flow into the shaft allows the thermal energy to be recovered from the heated rock particles. Innovation Status: A provisional patent application has been filed (SA 2014/03555).