Reclaimed Coal Ash as Low-Cost TES Material

One of the fundamental needs of power generation from solar resources is the ability to store thermal energy for periods when solar radiation is limited, either due to cloud passage or nighttime. The thermal energy storage media itself can be a significant cost driver for the overall system and therefore levelized cost of energy. We will address the need for an improved thermal energy storage material by using reclaimed coal ash which provides better thermal performance and lower cost compared to existing materials, which will benefit the DOE by reducing installation costs for concentrated solar power plants. Concentrated solar power generation requires economies of scale to compete on energy cost with photovoltaics, with feasible minimum size in the 50-100 MW range. Large, localized sites can cause grid disruptions if power drops off suddenly, meaning that viable concentrated solar power plants need some form of thermal energy storage to operate smoothly and increase electrical production (capacity factor) enough to compete with photovoltaics. Thermal storage also increases the utility of solar power because it allows concentrated solar power plants to produce electricity during valuable, grid-protecting peak usage periods (evening), and not just during mid-day. Future concentrated solar power plants need a thermal energy storage media that has high specific heat capacity and low cost, while absorbing solar energy readily and limiting energy loss due to emissions in the infrared spectrum. The objective of the Phase I program is to demonstrate a heat storage method using reclaimed coal ash. The approach of the Phase I program is to develop a reclaimed coal ash mixture that meets target thermal and physical properties, then test it as part of a fluidized bed heat transfer and storage system. During Phase I, we will perform processing, grading, and testing of landfilled coal ash to achieve desirable thermal energy storage properties. We will also perform fluidized bed heat exchange testing to assess the performance and charge/discharge capabilities of the reclaimed coal ash. The commercial applications of this technology include present and future concentrated solar power plants in the US and internationally. It will provide additional benefit to power companies and coal plant operators by reducing the costs of coal ash disposal and maintaining coal ash landfills.