Techno-economic analysis of the Li-ion batteries and reversible fuel cells as energy-storage systems used in green and energy-efficient buildings

Green buildings have become broadly adopted in commercial and residential sectors with the objective of minimizing environmental impacts through reductions in energy usage and water usage and, to a lesser extent, minimizing environmental disturbances from the building site. In this paper, we develop and discuss a techno-economic model for a green commercial building that is 100% powered by a photovoltaic (PV) system in stand-alone configuration. A medium-sized office building in El Paso, TX was modelled to rely on a photovoltaic system to supply all of its electricity needs either directly from the PV system or through an energy-storage system (ESS) using Li-ion batteries (LIBs) or reversible fuel cells (RFCs). Cost results show that a 400-kW PV system can generate electricity at a cost of 2.21 cents/kWh in El Paso, TX and the average levelized cost of energy storage (LCOS) using 450-kW RFC is ~31.3 cents/kWh, while this could reach as low as 25.5 cents/kWh using a small LIB ESS. While the RFC provides the flexibility required to meet building-energy demand, LIBs may not be able to meet building needs unless the storage size is increased substantially, which in turn incurs more energy-storage cost, making LIBs less favourable from an economic perspective. Sensitivity analysis revealed that capital cost, discount rate and expected system lifetime play key roles in shaping the LCOS in both systems.