Can storage reduce electricity consumption? A general equation for the grid-wide efficiency impact of using cooling thermal energy storage for load shifting

Abstract

This study estimates changes in grid-wide, energy consumption caused by load shifting via cooling thermal energy storage (CTES) in the building sector. It develops a general equation for relating generator fleet fuel consumption to building cooling demand as a function of ambient temperature, relative humidity, transmission and distribution current, and baseline power plant efficiency. The results present a graphical sensitivity analysis that can be used to estimate how shifting load from cooling demand to cooling storage could affect overall, grid-wide, energy consumption. In particular, because power plants, air conditioners and transmission systems all have higher efficiencies at cooler ambient temperatures, it is possible to identify operating conditions such that CTES increases system efficiency rather than decreasing it as is typical for conventional storage approaches. A case study of the Dallas-Fort Worth metro area in Texas, USA shows that using CTES to shift daytime cooling load to nighttime cooling storage can reduce annual, system-wide, primary fuel consumption by 17.6 MWh for each MWh of installed CTES capacity. The study concludes that, under the right circumstances, cooling thermal energy storage can reduce grid-wide energy consumption, challenging the perception of energy storage as a net energy consumer.

Opaque Envelopes: Pathway to Building Energy Efficiency and Demand Flexibility: Key to a Low-Carbon, Sustainable Future

“…Opaque-envelope-integrated thermal and/or moisture storage has the potential to offer multiple benefits in buildings. Thermal storage 15 can shift the timing of heating and/or cooling energy demand, improve thermal comfort by reducing the magnitude of temperature swings, and in some cases, offset energy use by recharging using nighttime air or solar heat gain and reduce the size or extent of space-conditioning equipment [61]. The annual energy savings potential of thermal storage varies widely as a function of climate (including available ambient recharging opportunities), storage system configuration (including the system size and switching temperature), building characteristics (including interior set points, internal heat loads, building size, and facade to interior volume ratio), and other factors.…”

“…If the HVAC system is used for charg-ing, thermal storage could boost the efficiency of the HVAC system. The effective round-trip efficiency of thermal storage might result in a net increase or decrease in total energy use compared to a system without storage depending on the building and equipment configuration and the local climate [61]. Coordinated HVAC and storage system design will be needed to maximize potential net energy savings from adding thermal or moisture storage when relying heavily on the HVAC system for charging.…”

A Decentralized Local Flexibility Market Considering the Uncertainty of Demand

“…However, for longer periods, temperatures may be affected, in which case payback power can be required [56,57]. It should be noted that the coefficient of performance (COP) of thermal storage-based appliances can be affected largely by the payback conditions, especially by the time variable element, which is the payback hour [58,59]. In addition to the common household loads, electric vehicles (EVs) have been gaining attention as potential source of flexibility.…”

Managing Power Demand from Air Conditioning Benefits Solar PV in India Scenarios for 2040

“…There are various CTES technologies with various performance characteristics and costs that can shift AC demand, including mechanical precooling the building thermal mass [36][37][38][39], chilled water or ice storage technologies [40][41][42][43], and phase change material such as hydrated salts [44]. Traditionally, AC demand flexibility measures have been exploited to shift AC demand to off-peak periods when electricity rates are low.…”