Reducing a semiarid city’s peak electrical demand using distributed cold thermal energy storage

Abstract

Several changes to the world’s electrical power systems and grids threaten to require massive infrastructure investment and cost to power utilities, especially increasing population and electrical energy demands, especially peak summertime air conditioning demands, and mismatches between timing of supply and demand due to increases in renewable energy and/or large demands from new technologies. Existing power grid systems are generally under-utilized with low load factors during most times of day and year, but demand strains capacity during peak hours. Brownouts and other grid failures are projected to become more common as peak demands approach grid capacities, with negative economic and public health consequences resulting. Meanwhile a financial barrier exists for the financing of grid improvements, because utility revenues are proportional to total power sales, whereas utility costs are driven largely by capital and maintenance for the fixed infrastructure.An alternative to active demand management or electrical energy storage is to shift thermal demands to off-peak hours, allowing the utility’s power grid to meet much larger total demands using a fixed capacity. Thermal energy storage is a mature, energy-efficient, and possibly cost-effective technology that can be applied to buildings of all sizes, and is particularly well-suited to shift afternoon peak cooling demands to off-peak hours in hot summertime months. This simple technology, if distributed widely, can make a dramatic impact on power grid load factors in hot cities.This paper utilizes a utility-scale model of the Phoenix metropolitan area to simulate the air conditioning portion of the electrical demand during a summertime heat wave. The electrical demand by air conditioning during peak hours is incrementally shifted to off-peak hours using distributed thermal storage technology. The aggregated thermal storage capacity and operating hours required to reduce the peak load by incremental fractions are established, along with the size of the gross electrical energy cost savings potentially realized by electrical power consumers during heat wave events, at current electricity prices.