Publications

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Forward operating base (FOB) microgrids typically use diesel generators with discrete logic control to supply power. However, emerging energy storage systems can be added as spinning reserves and to increase the PV hosting capacity of microgrids to significantly reduce diesel consumption if resources are controlled appropriately. Discrete logic controllers use if/else statements to determine resource dispatch based on inputs such as net load and generator run times but do not account for the capabilities of energy storage systems explicitly. Optimal dispatch controllers could improve upon this architecture by optimizing dispatch based on forecasts of load and generation. However, optimal dispatch controllers are far less intuitive, require more processing power, and the level of potential improvement is unclear.This work seeks to address three points with regards to FOB microgrid operations. Firstly, the impact of energy storage systems on the adoption of solar generation in microgrids is discussed. Secondly, logic is added to the typical discrete controller decision tree to account for energy storage resources. Lastly, fuel savings with energy storage and solar generation using the new discrete control logic and optimal dispatch are compared based on load data measured from a real FOB. The results of these analyses show the potential impact of energy storage on fuel consumption in FOBs and gives guidance as to the appropriate control architecture for management of integrated resource microgrids.

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Battery energy storage systems are often controlled through an energy management system (EMS), which may not have access to detailed models developed by battery manu-facturers. The EMS contains a model of the battery system's performance capabilities that enables it to optimize charge and discharge decisions. In this paper, we develop a process for the EMS to calculate and improve the accuracy of its control model using the operational data produced by the battery system. This process checks for data salience and quality, identifies candidate parameters, and then calculates their accuracy. The process then updates its model of the battery based on the candidate parameters and their accuracy. We use a charge reservoir model with a first order equivalent circuit to represent the battery and a flexible open-circuit-voltage function. The process is applied to one year of operational data from two lithium-ion batteries in a battery system located in Sterling, MA USA. Results show that the process quickly learns the optimal model parameters and significantly reduces modeling uncertainty. Applying this process to an EMS can improve control performance and enable risk-averse control by accounting for variations in capacity and efficiency.

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The Energy Surety Design Methodology (ESDM) provides a systematic approach for engineers and researchers to create a preliminary electric grid design, thus establishing a means to preserve and quickly restore customer-specified critical loads. Over a decade ago, Sandia National Laboratories (Sandia) defined Energy Surety for applications with energy systems to include elements of reliability, security, safety, cost, and environmental impact. Since then, Sandia has employed design concepts of energy surety for over 20 military installations and their interaction with utility systems, including the Smart Power Infrastructure Demonstration for Energy Reliability and Security (SPIDERS) Joint Capability Technology Demonstration (JCTD) project. In recent years, resilience has also been added as a key element of energy surety. This methodology document includes both process recommendations and technical guidance, with references to useful tools and analytic approaches at each step of the process.

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The potential benefits from energy storage deployment are highly location dependent. In market areas, remuneration is largely based on market products and prices. In a vertically integrated utility, the benefits are often monetized through cost savings. This paper quantifies the potential benefits of using an energy storage system to provide spinning reserve within the Cordova Electric Cooperative (CEC) grid. The CEC is a small rural electrical cooperative in Cordova, Alaska. Energy storage is being considered to provide spinning reserve. The cost saving is realized through reduced fossil fuel consumption and run time on the diesel generators. In this paper, the cost savings are used to determine the benefit-to-cost ratio for various energy storage configurations. Additional potential benefits of energy storage for the CEC are also presented.

This paper investigates the suitability of sizing the electrical export cable based on the rating of the contributing WECs within a farm. These investigations have produced a new methodology to evaluate the probabilities associated with peak power values on an annual basis. It has been shown that the peaks in pneumatic power production will follow an exponential probability function for a linear model. A methodology to combine all the individual probability functions into an annual view has been demonstrated on pneumatic power production by a Backward Bent Duct Buoy (BBDB). These investigations have also resulted in a highly simplified and perfunctory model of installed cable cost as a function of voltage and conductor cross-section. This work solidifies the need to determine electrical export cable rating based on expected energy delivery as opposed to device rating as small decreases in energy delivery can result in cost savings.

This paper presents a review of the main electrical components that are expected to be present in marine renewable energy arrays. The review is put in context by appraising the current needs of the industry and identifying the key components required in both device and array-scale developments. For each component, electrical, mechanical and cost considerations are discussed; with quantitative data collected during the review made freely available for use by the community via an open access online repository. This data collection updates previous research and addresses gaps specific to emerging offshore technologies, such as marine and floating wind, and provides a comprehensive resource for the techno-economic assessment of offshore energy arrays.

This report is a follow on to a previous study performed by Sandia National Labs and Alaska Center for Energy and Power which investigated the use of an energy storage system (ESS) providing spinning reserve within the Cordova Electric Cooperative (CEC) grid. The study provided the savings using the ESS as spinning reserve through reduced fossil fuel consumption and runtime on the diesel generators. In this report, the saving values are used from the previous study to determine the benefit-to- cost ratio for various ratings of ESS performing spinning reserve and quantifying other applications that are applicable to CEC.

The community of Cordova, Alaska currently uses diesel and run-of-river hydro generation for its electricity needs. In the past, 60% of the Cordova summer load was supplied by the run-of-river generation. The majority of the time, the load was supplied only by the run-of-river generation. The bulk of generated electricity is delivered to Cordova's industrial fish processing plants and to other industrial loads. With the expansion of Cordova's fishing industry, the run-of-river generation is less often able to supply 100% of the load demand. When the run-of-river generation is not able to supply 100% of the load demand it has to be supplemented by diesel generation. There are also many times when the load demand is low and the available run-of-river generation has to be curtailed by spilling water which could be stored in an energy storage system. Sandia National Laboratories and Alaska Center for Energy and Power collaborated to evaluate how an energy storage system can be used to capture the spilled water and how it can economically and technically benefit Cordova during the fishing season and other times throughout the year. Results from this study are summarized in this report. 3

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