Development of space heating and domestic hot water systems with compact thermal energy storage. Compact thermal energy storage: Material development for System Integration

Long-term, compact thermal energy storage (TES) is essential to the development of cost-effective solar and passive building-integrated space heating systems and may enhance the annual technical and economic performance of solar domestic hot water (DHW) systems. Systems should provide high energy storage density, charge and discharge temperatures that match the heat source used for charging and the intended load, adequate charge/discharge power, and employ storage materials that are stable over many cycles, non-toxic, environmentally safe. Moreover, these systems must compete effectively in the marketplace and therefore should provide an economic benefit compared to conventional heating and DHW systems, which have traditionally relied on sensible water storage. The IEA joint Task/Annex 42/24 brings together experts in materials development and systems integration to develop advanced materials and systems for the compact storage of thermal energy. Working Group WB2 addresses applications of compact thermal energy storage for space heating and hot water (20 to 100 oC). The activities in this working group are aimed at guiding materials development, within the limitations of these two applications, and at development of systems that use compact storage medium with the goals of improved technical and economic performance compared to traditional approaches. Because solar assisted heating of buildings is the main focus of the SHC IEA, this topic is addressed by many of the contributors to this report. However, because there are many relevant applications for TES, the working group activities encompass other applications including systems for passive building integrated climate control. The primary activities of the working group include: election of candidate materials and system configurations; assessment of the technical performance of systems through laboratory tests of components and systems, case studies, modeling, and/or field studies; assessment of the economic performance through modeling and evaluation of market potential. This report summarizes the contributions of the working group over the period from February 2009 through December 2012. The focus is on the development of system concepts (item 1 from the list above) and technical evaluation of proposed systems and the storage components of these systems through predictive modeling and laboratory testing.