Techno-economic analysis of metal-hydride energy storage to enable year-round load-shifting for residential heat pumps

• Published in: Energy and buildings Vol. 256; p. 111700
• Main Authors: Krane, Patrick, Ziviani, Davide, Braun, James E., Jain, Neera, Marconnet, Amy
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01-02-2022; Elsevier BV
• Subjects: Air conditioning; Cooling; Cooling loads; Cooling systems; Cost analysis; Cost control; Cost reduction; Economic analysis; Electric rates; Electrical loads; Energy costs; Energy storage; Heat exchangers; Heat pumps; Heating; Heating systems; Load shifting; Metal Hydrides; Metals; Operating costs; Payback periods; Phase change materials; Residential areas; Residential buildings; Residential energy; Residential HVAC systems; Systems design; Thermal energy; Thermal Energy Storage; Time of use electricity pricing; Year-round Energy Storage; Thermal Energy Storage; Year-round Energy Storage; Residential HVAC systems; Metal Hydrides
• ISSN: 0378-7788; 1872-6178
• DOI: 10.1016/j.enbuild.2021.111700

•Metal hydrides show potential for year-round energy storage with residential HVAC.•Hydride storage can shift both heating and cooling loads away from on-peak hours.•Using hydride storage results in higher cost savings in winter than in summer.•Hydride storage has a long payback period even for favorable TOU rates.•Long payback periods are due to high initial cost and hydrogen compression costs.
Thermal energy storage (TES), such as ice storage, is often used with air conditioning systems to shift cooling loads away from peak hours, reducing operating costs if time-of-use electricity rates are available. Phase change materials (PCMs) have been investigated for energy storage with heating systems; however, a single PCM cannot be used for storage with both cooling and heating since PCMs have fixed phase-change temperatures. Thermochemical energy storage with metal hydrides can be used for this purpose since the reaction used to store energy depends on both temperature and pressure, allowing for variable-temperature storage. In this paper, we propose a novel TES system design using metal hydrides coupled to a heat pump for residential heating and cooling and present a system model. The model is used to analyze system performance and predict cost savings for year-round use in a residential building. This system is shown to be capable of shifting heating and cooling loads, but only achieves cost savings of $13/year at existing utility rates. The payback period of the system exceeds 35 years across a range of rates more favorable to energy storage, primarily due to the high cost of metal hydrides. Potential improvements to the system are discussed.