At its core an Energy Storage System (ESS) is comprised of three major components each bearing equal importance. The battery which is the energy container; the Power Conversion System (PCS) or inverter which interfaces the DC battery system to the AC power system; and the Power Plant Controller (PPC) which governs, monitors and executes the intended functions of the energy storage application.
Although we have no choice but to accept that the battery is the consumable component, the balance of system of an ESS should not be regarded as such. While heavy emphasis is typically placed on the choice of battery technology, it is important to understand that poor selection of the other two core components can severely impact the performance, lifetime and return on investment of the ESS. In this article we will seek to shed some light on the importance of the PCS and the PPC.
The Power Conversion System (inverter)
The PCS can be subjected to brutal utilization as it may be expected to handle varying power levels in both directions 24 hours per day. The stresses imparted on the PCS can easily make it the weakest link.
When procuring a PCS, system owners should select power conversion technology that is designed for high reliability and availability, and up to three decades of service life. It is also essential that the equipment can be operator maintained, tracked, and managed. The PCS should be designed with grid support functionality and should facilitate upgrades as the energy ecosystem advances.
Owners and operators should favor flexible and easily transportable architectures that can be repurposed as needs evolve. Most importantly, they should choose suppliers that will stick around for the long haul.
The Power Plant Controller
Many are of the opinion that an energy storage control system is not difficult to implement. This outlook is based on assumptions that the hardware can be assembled from off-the-shelf components, and that there is an abundance of skilled software programmers to create algorithms. Energy storage is a critical power application and as such controlling it is by no means a trivial task.
Some argue that since ESS controls is a new technology sector, there are no real industry experts or veterans. On the contrary, those with experience in critical industrial and power systems controls are indeed the experts who can utilize equipment and best practices from those applications to create solid energy storage control platforms. It is imperative that control system providers have the means and experience to address important factors such as redundancy and cybersecurity.
All considered, system owners should select the ESS control provider based on demonstrated success and experience in related critical power control systems and industrial automation. They should also consider the longevity and staying power of the provider they choose.
The bottom line is that the PCS and Plant Controller are just as important to the ESS as is the battery. A poor choice of one or both of these two core components can result in an unprofitable and dysfunctional ESS that will be fraught with recurring repair and replacement costs.
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