(313h) Greenhouse Gases for Heat Transfer Fluids in Ultra-High Temperature Thermal Energy Storage

The use of ultra-high temperature (>1000°C) thermal energy storage (TES) would facilitate better heat management in energy intensive processes. When implemented with concentrated solar power, TES can also reduce intermittency that is experienced with renewable sources. At these high temperatures, radiation becomes an important mode of heat transfer. To take advantage of this effect, greenhouse gases, carbon dioxide (CO₂) and steam (H₂O), were investigated as potential heat transfer fluids (HTFs) in TES for their ability to absorb radiation compared to nitrogen (N₂). To investigate this, a novel experimental setup with a moving thermocouple was designed to measure temperatures of CO₂, H₂O, and N₂ as the gases are heated up through a tube to 1400°C. The moving thermocouple allows for temperature measurements at any height as the gas is heated. Experimental results are modeled and validated using the discrete ordinates method with gray and non-gray gas absorption coefficients to quantify the significance of radiation. This presentation will include a description of the unique well-insulated experimental apparatus having three 1-foot long heated zones, experimental results, and thermal modeling for heating CO₂, H₂O, N₂, and mixtures. The use of greenhouse gases as HTFs for ultra-high temperature TES have the potential to enhance heat transfer when radiation is significant.