Wednesday, February 22, 2017

Thermal Energy Storage

Thermal energy storage (TES) is achieved with greatly differing technologies that collectively accommodate a wide range of needs. It allows excess thermal energy to be collected for later use, hours, days or many months later, at individual building, multi-user building, district, town, or even regional scale depending on the specific technology. As examples: energy demand can be balanced between daytime and nighttime; summer heat from solar collectors can be stored inter-seasonally for use in winter; and cold obtained from winter air can be provided for summer air conditioning. Storage media include: water or ice-slush tanks ranging from small to massive, masses of native earth or bedrock accessed with heat exchangers in clusters of small-diameter boreholes (sometimes quite deep); deep aquifers contained between impermeable strata; shallow, lined pits filled with gravel and water and top-insulated; and eutectic, phase-change materials.

Other sources of thermal energy for storage include heat or cold produced with heat pumps from off-peak, lower cost electric power, a practice called peak shaving; heat from combined heat and power (CHP) power plants; heat produced by renewable electrical energy that exceeds grid demand and waste heat from industrial processes. Heat storage, both seasonal and short term, is considered an important means for cheaply balancing high shares of variable renewable electricity production and integration of electricity and heating sectors in energy systems almost or completely fed by renewable energy.

Approaches to Thermal Energy Storage

Footnote on Endothermic/exothermic chemical reaction text

“Storing energy in molecular bonds is being investigated. Energy densities equivalent to lithium-ion batteries have been achieved.”

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