Load shift happens
Adam Dicken of Phase Change Materials Products talks about load-shifting strategies and thermal energy storage for saving energy and reducing operational costs in cold stores.
C
old stores and refrigerated warehouses consume considerable amounts of energy. Within these facilities, 60-70% of the electrical energy is used solely for refrigeration. Therefore, there is a major incentive to reduce this energy demand leading to improved environmental and economic performance. By adopting the appropriate strategy and techniques it is possible to achieve energy savings of 30-40%, which would directly translate into a more economically competitive and effi cient facility. The core principle of many of these strategies is avoiding high electricity day-peak rates. This is achieved by shifting a proportion of the peak cooling capacity into off -peak periods, commonly known as load-shifting.
The benefi t of shifting cooling capacity into the night-
time off -peak is twofold. First, it is possible to gain access to cheaper electricity rates, and second, the refrigeration equipment will operate in lower ambient temperature conditions, leading to further savings thanks to an improved COP.
Load-shifting uses thermal energy storage (TES) as a way to bridge the gap between energy availability and energy usage. It can be further divided into two main areas, one where the sensible heat is used and the other where latent heat is used.
Latent heat TES uses phase change materials (PCM). These materials store and release at a given temperature during the freezing and melting process. When these materials freeze, they release large amounts of energy in the form of latent heat. Conversely, when these materials are melted, an equal amount of energy is absorbed and stored by the PCM. This entire process is thermal and not chemical, meaning that these materials can be cycled countless times without any decrease in performance.
Pre-cooling or the overcooling of a cold store shifts an amount of the peak-day refrigeration load into the off - peak hours ahead of the demand. This option is a predictive measure and risks the overcooling of produce, which can have serious consequences depending on the nature of the stored goods.
A key benefi t of this strategy is that pre-cooling can be achieved without the need of any additional installations,
36 May 2019
www.acr-news.com
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