Thermal Energy Storage

See how thermal energy storage allows CSP plants to continue to provide electricity to the grid even at times when the resource (the sun) is not available, such as cloud transients or at night. The ability to incorporate Thermal Energy Storage (TES) systems is a key differentiator between Concentrating Solar Power (CSP) and intermittent forms of renewable energy, such as wind and Photovoltaics (PV). Watch a video or Learn about our partnership with the California Energy Commission
Figure 1: IR image of lab-scale TES system during discharge
Amey Barde Kaiyuan Jin Mitchell Shinn Karthik Nithyanandam Richard Wirz

The bundled TES is designed to demonstrate the performance of sulfur based thermal energy storage system operating in the temperature range of 200-600 C to store at least 5kWh thermal energy. The bundled TES design is based on the shell and tube heat exchanger, with sulfur tubes enclosed in a rectangular shell. 10 sulfur tubes are installed that results in a total storage capacity up to 8 kWh. Total 21 baffles are installed that provide tortuous path for air and enhance heat transfer between air and sulfur.

Amey Barde Mitchell Shinn Richard Wirz

The single element test is an important step towards design and fabrication of a test facility for the demonstration of solar thermal energy storage technology using sulfur as a thermal storage material. It provides a controlled environment to investigate the performance of thermal storage fluid, based on the thermal storage capacity and the charging-discharging rate. The single element test serves to achieve two important objectives.

    Amey Barde Mitchell Shinn Richard Wirz

    Pressure-temperature characteristics of sulfur are investigated in sealed containers up to 600 degrees C. The analysis provides crucial information regarding the maximum system pressure during thermal charging and discharging of the system. The sulfur container is designed based on the maximum system pressure for safe and effective containment sulfur over a long period of operation. During this analysis, effect of sulfur loading fraction on the system pressure is studied. The loading fraction of the sulfur is defined in Figure 4 below.

    Numerical heat transfer analysis of sulfur TES at component and system level
    Karthik Nithyanandam Amey Barde Richard Wirz

    Sulfur promises low storage cost, high temperature stability, and high charge and discharge performance since it operates in the liquid-vapor regime at the temperatures of interest relevant to many important applications, such as combined heat and power (CHP) plants and concentrating solar power (CSP) plants with advanced power cycle systems. The present work investigates the thermal performance of elemental sulfur stored isochorically inside the pipes of a shell-and-tube thermal battery configuration with heat transfer fluid flowing over the storage pipes through the shell.

    Louis Tse Adrienne Lavine Karthik Nithyanandam Richard Wirz

    The goal of this task is to develop a tool for monitoring the performance of the developed TES system in operation with micro-CSP, parabolic troughs, and solar power towers. An in-house thermodynamic system/cost model informed by theoretical and numerical analysis of sulfur species equilibria is developed to estimate the cost and exergy efficiency of MacroTES for different CSP applications. The system model is designed to simulate the overall thermal energy system using sub-models for the solar field, thermal storage, and generation.

    Experimental setup for material compatibility analysis
    Gabriela Bran-Anleu Richard Wirz

    The goals of the Material Compatibility Analysis task are to: (1) test the compatibility of primary tank materials with elemental sulfur; and (2) identify potential linings (if necessary) for tank materials. Three different alloys with potential application for containment of sulfur as an energy storage fluid, namely Stainless Steel 304, Stainless Steel 316, and Inconel 600, were studied. All alloys were thermally cycled to maximum temperatures of 500 °C and 600 °C, and kept at that temperatures for a prolonged period of time.

    Ben Furst Richard Wirz Adrienne Lavine Reza Baghaei Lakeh

    Thermal Energy Storage (TES) is utilized throughout industry and is considered an enabling technology for solar thermal power plants. Current state of the art TES systems rely on sensible heat storage in solids or liquids, and latent heat storage in the solid/liquid phase change. Preliminary studies indicate that other thermodynamic regimes that have been unexploited, such as the two-phase liquid/vapor regime and the supercritical regime, may also have beneficial TES characteristics. The goal of this effort is to characterize the TES potential of these regimes, and evaluate their utility.

    Louis Tse Adrienne Lavine Richard Wirz

    This study outlines a methodology for modeling and optimizing multi-phase thermal energy storage systems for solar thermal power plant (STPP) operation by incorporating energy and exergy analyses to a TES system employing a storage medium that can undergo multi-phase operation during the charging and discharging period.