Nobel laureate brings in Brayton physics for inexpensive renewable energy storage

If renewable energy generation, especially from intermittent sources, will impactfully provide energy and serve to alleviate greenhouse gas emissions, the attendant storage challenges, especially cost, need to be addressed. Moreover, storage technologies, such as batteries and underground caverns for compressed air and hydrogen (e.g. for wind), also have chemical limitations and safety risks. In the Journal of Renewable and Sustainable Energy, Nobel prize-winning physicist Robert B. Laughlin offers a detailed, cost-effective design for storing renewable energy that is safe and technologically feasible.

Used for hydroelectricity, water, pumped uphill, stores energy. Laughlin describes a similar process of transferring heat from a cold to hotter place, and he derives his design from Brayton engine physics, with its constant pressure heat transfers. Current state of the art turbines would be adapted to move the captured energy through the system with heat stored in a salt (NaNO3/KNO3) fluid. The salt fluid can contain and release much energy, is cost effective, and is in fact currently used in the solar industry. Unlike hydroelectricity, not much land is needed.

Charting the system’s thermodynamics, Laughlin underscores the Brayton system’s effectively minimizing entropy, which bears greatly on a system’s cost. Also, steel – which Laughlin says energy scientists should understand more – plays a key role. Using a quality alloy in the system significantly forestalls the “creep” in which thermal stresses weaken the structure, increasing replacement costs.

Laughlin says researchers need to appreciate that technical questions are not overriding but rather cost is the fundamental challenge for renewable energy storage. The entropy-budget, too, is central for effectiveness and cost. However, Laughlin emphasizes his paper accentuates that the renewable energy storage problem is solvable and does not require breakthrough physics, just investment and attentive engineering.

Source: “Pumped thermal grid storage with heat exchange,” by Robert B. Laughlin, Journal of Renewable and Sustainable Energy (2017). The article can be accessed at https://doi.org/10.1063/1.4994054 .