Abstract
The average daily benefit to cost ratio of a building energy storage system is mainly constrained by the battery lifetime. This paper aims to minimize the average daily cost of a hybrid energy storage system (HESS) (comprised of a battery and supercapacitor) by optimizing the battery capacity. A novel optimization model is proposed with the objective to find the minimum average daily investment cost of the HESS. The objective function has two parts: (1) the investment cost formula for the battery is derived as a function of the battery capacity, which has an interdependence with the minimum state of charge (SOC) and the maximum discharge current; (2) the investment cost formula for the supercapacitor is also established as a function of battery capacity by matching the maximum battery power with that of the supercapacitor. Case studies demonstrate several ways to increase the average daily benefit to cost ratio: (1) adopting a suitable control strategy to avoid capacity saturation; (2) reducing the battery SOC to increase the threshold for the maximum discharge current (MDC) saturation; and (3) increasing MDC to raise the threshold for the SOC saturation. Results show that the average daily benefit to cost ratio is doubled compared to previous work.
Highlights
At present, energy consumed at the domestic building level is one of the major forms of global energy consumption [1]
In [15], using two groups of batteries to meet the demand instead of one battery is preferable, considering that the physical size and installation cost of energy storage systems are strictly limited in domestic building, only one battery is considered in this paper
To the best knowledge of the authors, this paper presents the first study to optimize the daily average daily benefit to cost ratio of hybrid energy storage system (HESS) accounting for the three key factors: state of charge (SOC), maximum discharge current and HESS capacity
Summary
Energy consumed at the domestic building level is one of the major forms of global energy consumption [1]. In [15], using two groups of batteries to meet the demand instead of one battery is preferable, considering that the physical size and installation cost of energy storage systems are strictly limited in domestic building, only one battery is considered in this paper. The main contributions of this paper are: (1) three key factors (SOC, discharge current and HESS capacity) are comprehensively considered for the optimization; (2) the main novelty is formulating all parameters in terms of the battery capacity for a given SOC and discharge current, by doing which an optimal operating region can be defined which is shown in Section 5; (3) using this approach the average daily benefit to cost ratio of the HESS is shown, in an example case study multi-energy system, to significantly increase by a factor of two compared to the previous work [1].
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