Quantifying flexibility of load aggregations: impact of communication constraints on reserve capacity

Abstract

Due to the increased use of variable renewable energy sources, more capacity for reserves is required. Non-generating resources such as thermostatically controlled loads (TCLs) can arbitrage energy prices and provide reserves due to their thermal energy storage capacity. The quantity of reserves depends not only on the aggregate power capacity, but also on information and communication technology, exogenous parameters, and system operator requirements. Specifically, the practical limitations origin from (i) communication constraints, (ii) ambient temperature, and (iii) the dispatch time of the activation signal. This study explores the impact of these parameters on the amount of reserves that an aggregator of TCLs can provide to the system operator based on centralised control of a TCL population. A decision support tool is proposed that can be used by aggregators to decide on maximum dispatchable reserve bids. The method can accommodate the specific control algorithm and TCL population of an aggregator and is based on offline computation. It constitutes a powerful reserve bid library to be used when optimisation tools become computationally intractable due to the increased number of decentralised flexible loads.