Project Drawdown – Centralized Energy Storage for Residential Communities

Project Drawdown proposes centralized energy storage operated by the community for the benefit of local residential consumers/prosumers. This article compares the sizing of two control types to smooth DWEC farm production: uncoordinated (a) and centrally coordinated (b).

Electricity, thermal, aging and life cycle costs have been considered. The centralized scheduling approach needs a smaller capacity, but the power fluctuations at each device output increase significantly.

Size

The purpose of this paper is to propose a simple and practical load-based methodology for determining the appropriate capacity of Centralized BESS in residential communities with rooftop Solar PV to operate as Virtual Power Plant (VPP) for electrical network reliability improvement by alleviating Enegy?Shocks (EnS). This is achieved by first presenting the procedures of energy consumption and peak demand profiling per residential community. Based on the profiles, the centralized BESS capacity is determined by selecting the proper management parameters EMin, t and a using a simple sensitivity analysis. The battery state-of-charge (SoC) is also taken into consideration. Finally, the appropriate capacity is derived in terms of kilowatt-hour per month, depending on the mean, 75% and maximum energy consumption per community. The results show that the proposed centralized controller significantly improves the voltage stability of the electrical grid.

Control

Several studies have been performed to invest in storage technologies, such as supercapacitors [3], flywheels [5] or even Superconducting Magnetic Energy Storage (SMES) in order to smooth Direct Wave Energy Converter (DWEC) farm production and allow grid integration. However, there are few studies that justify the need of such a system technically and economically. In addition, few study the impact of these systems on the energy cost. This is the objective of this study, which is to determine if and when it is possible to minimize energy storage Centralized Energy Storage System costs by centralizing management. This is done by optimizing the sizing and management of an ESS with a rule-based energy management approach, considering power, State of Energy, thermal, aging and cost models.

Two configuration methods are compared: distributed, applied on the excitation DC link of each DWEC unit and centralized, which is applied on the exit bus of the wind farm. It is shown that, if the energy storage technology and wind farm scale meet requirements, a centralized control can save between 7% and 37% of the total energy costs.

Performance

The performance of energy storage systems at building-cluster level can be significantly improved by regulating the power charging/discharging rate via optimal control. For this purpose, an existing control system which is able to optimize the charging/discharging rates of each energy storage system in the same community has been extended and applied for the optimization of building-level energy storage systems. The results show that this control can enhance the total energy efficiency and power self-consumption of the buildings by up to 29%, and reduce their daily operational costs.

The impact of centralized coordination on consumers’ annual electricity costs and savings is also investigated. We find that the impact increases with the level of variable renewable capacity in the electricity system and inversely related to the level of flexible supply resources. Moreover, the benefits of EES to the electricity system increase with the capacity of aggregated storage for balancing variations.

The performance of an ESS can be optimized by choosing its size and management strategy carefully. The sizing process is optimized for each size to minimize its aging speed and the flicker threshold, whereas the management approach depends on the State of Energy of the storage system to maximize its lifetime value.

Life Cycle

The growing need to reduce greenhouse gas emissions and the depletion of fossil fuels stimulate the development of various energy storage technologies, such as electrochemical batteries, pumped hydropower storage, and compressed air. The sustainability of these technologies has to be assessed from an economic and environmental point of view, as well as from the exergetic perspective.

To this end, a life cycle assessment (LCA) of the proposed system is conducted for several climatic conditions and building types. It Centralized Energy Storage System compares the proposed system with various conventional energy generation in terms of the economic cost, freshwater consumption, and air emissions impacts (i.e., acidification, eutrophication, ecotoxicity, global warming) for a 50-year period. The resulting results show that the CSP plant is superior in all aspects compared to conventional power generation. The impact of the molten salts is the main cause of this result. To reduce their impact, the origin of the salts is considered. The conclusion is that the salts can be obtained from mining operations with lower impact than those derived from synthetization.

Another issue relating to the LCA is how to size and manage centralized energy storage systems. This is important because a centrally coordinated operation of distributed energy storage systems leads to higher benefits for consumers, prosumers, and the community at large through aggregation. These benefits include resiliency, grid stabilization, peak electricity price declines, increase in the value of PV and wind installations, and reduced transmission infrastructure costs.