In response to changes in electrical demand from increased adoption of electric vehicles (EVs) and on-site generation, utilities are evaluating multiple options for managing dynamic loads, including greater use of time-of-use pricing, demand charges, variable generation curtailment, and energy storage. Behind-the-meter storage (BTMS) is of particular interest because it has the potential to provide both operational benefits for utilities and cost savings or resilience benefits for utility customers. Additionally, energy storage can allow for greater use of renewable energy generation, maximizing the sustainability benefits of these investments. However, limited information is available about how to effectively combine different BTMS technologies, such as stationary batteries and thermal energy storage, to minimize costs for system owners. Optimizing the design of BTMS systems can increase the degree to which building energy efficiency, batteries, thermal energy storage, and solar energy can have positive sustainability impacts.

With funding from the Vehicle, Building, and Solar Energy Technology Offices at the U.S. Department of Energy, the authors are conducting a BTMS analysis that focuses on determining optimal system designs and energy flows for thermal and electrochemical storage for sites with on-site solar photovoltaic (PV) generation and EV charging. The team is examining viability of BTMS with various climates, building types, and utility rate structures. The analysis includes a retail big-box grocery store, a commercial office building, a fleet vehicle depot and operations facility, a multifamily residential building, and an electric vehicle charging station. To enable this analysis, the team is developing a tool, named EnStore, that integrates three existing modeling applications into a single simulation platform. 

EnStore allows the team to examine how optimal energy storage designs depend on site-specific details, such as building operation and EV schedules. This will also allow the team to incorporate battery degradation models, vary supervisory control algorithms for charging/discharging of storage systems, and assess how thermal energy storage can complement a stationary battery by shifting or reshaping electrical loads from space conditioning equipment. 

The analysis captures key performance characteristics of both existing and novel energy storage technologies. These include new batteries designed specifically for stationary applications, which have different requirements and density constraints than vehicular applications, as well as new thermal energy storage technologies with innovative materials or components.  By integrating high-fidelity models of diverse technologies, the team is evaluating the sensitivity of results to various inputs, including weather data, building models, EV load profiles, electricity rate tariff information, and system cost information for the stationary battery, solar PV, and thermal energy storage systems. 

The team will present the principles behind the integrated EnStore modeling framework and progress on the development of key EnStore features and inputs, such as high-resolution EV load profiles. Once complete, EnStore will enable the team to evaluate how BTMS can enable greater sustainability by increasing operational flexibility, resilience, cost savings, and use of renewable energy.


Behind the Meter Storage for Electric Vehicle Charging, Electrochemical and Thermal Energy Storage, and Solar Photovoltaic

Division / Sponsor:
Advanced Energy Systems Division (AESD) & Solar Energy Division (SED)

Paper Proceedings: https://asmedigitalcollection.asme.org/ES/ES2020/volume/83631

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