2:00pm - 2:20pm
Optimal Use of Grid-Connected Energy Storage to Reduce Human Health Impacts
NC State University, United States of America
Grid-connected energy storage can perform a wide variety of applications, yielding potential benefits to power system operations and system-wide costs. Current applications for energy storage, however, do not explicitly consider the potential to reduce adverse human health impacts from power generation. In this study, by taking advantage of energy storage’s ability to shift both the time and location of power sector emissions based on their charging and discharging strategies, we propose a method that enables energy storage to cost-effectively reduce human health impacts from the power sector. To do this, we simulate the air quality change due to the hourly emission from electricity generation and determine the hourly health damage cost associated with humans’ exposure air pollutants for each electricity generating unit by applying the concentration-response function and the Value of a Statistical Life. We then internalize these health damage costs in the power plant dispatch decisions, re-optimizing the unit commitment and economic dispatch model in light of these costs.
Two factors, energy storage and health damage cost, are introduced to the traditional unit commitment and economic dispatch model, and our preliminary results show that both of them can contribute to a health impact reduction: a reduction in human health impacts is achieved through changes in the commitment and dispatch of existing generators in the absence of energy storage; energy storage allows further reducing health damages when costs are internalized by adding more flexibility to the system. With higher energy storage capacity in the grid, a greater health damage reduction can be realized. Through our modeled system, we are able to demonstrate cases when energy storage can reduce up to 20% of the health impacts caused by SO2 emitted from power plants when the system is operated to minimize the health damage cost. Benefits of this magnitude, however, would not typically be realized on the basis of economic optimization alone, even when monetizing health externalities. It is worth noting that it is calculated based on the relative risk (RR) value of SO2 and the result is very sensitive to RR value. This result provides the motivation to apply this method to reduce the health impacts of PM2.5 which has a much higher RR value than SO2 but more sophisticated air quality model to simulate the change of PM2.5 concentration will be needed.
2:20pm - 2:40pm
The Potential Environmental and Economic Benefits of Energy Storage Systems in North Carolina
North Carolina State University, United States of America
Energy storage is rapidly emerging as a viable alternative to provide several grid services. The retirement of coal generation and rapid deployment of solar photovoltaics makes North Carolina a potentially attractive location for energy storage adoption. With a wide consortium of stakeholders and support from the North Carolina General Assembly, a team of researchers investigated the costs and benefits of energy storage adoption in the state under a range of future scenarios. Within this study, we examined the role of storage to fulfill two services: bulk energy time shifting and peak capacity deferral.
Using Tools for Energy Model Optimization and Analysis (Temoa), an energy system optimization model, we developed scenarios for the future of the grid in the Carolinas with optimal generation expansion and economic dispatch. Scenarios conducted include a high natural gas price, accelerated electric vehicle adoption, and an expanded renewable portfolio standard, among others.
Our research found that some site-specific storage technologies such as pumped hydroelectric storage and compressed air energy storage are already cost-effective in some cases. Using 2019 costs, lithium-ion (Li-ion) batteries are cost-effective for only a few services, such as frequency regulation and behind-the-meter applications to reduce demand charges. Because Li-ion battery costs are decreasing so rapidly, we ran scenarios with projected 2030 battery costs. By 2030, Li-ion batteries can be used cost-effectively for frequency regulation, bulk energy time shifting and peak capacity deferral, coincident peak shaving in the commercial and industrial sector, and improving distribution reliability. Currently, only 1 MW of battery storage and 185 MW of pumped hydro storage are currently integrated into the NC electric grid. Our study found that even 5 GW of storage could be cost-effective by 2030.
The environmental impact of energy storage is driven by the round-trip efficiency as well as the emissions profile of the generators used to charge the battery and those displaced when the battery is discharged. We analyzed the impact of storage on carbon dioxide emissions in two scenarios: the base scenario and the expanded renewable energy portfolio standard scenario. In our analysis, natural gas combustion turbines represent the largest share of displaced generation, while charging is driven by solar generation that would have otherwise been curtailed. The net impact of this activity is a reduction of power sector emissions ranging from 0.2% to 9.3%. The ability to charge with curtailed solar is a result of high solar penetration levels (both now and in 2030). This translates to increased benefits of Li-ion battery systems of 10 – 40 $/kW-year under a $50/ton carbon tax.
2:40pm - 3:00pm
Green principles for responsible battery management and strategies to maximize battery service lifetime
University of Michigan, United States of America
Vehicle electrification is expanding worldwide and has the potential to reduce greenhouse gas emissions (GHGs) from the transportation sector. Batteries are a key component of energy storage systems for electric vehicles (EVs), and their integration into EVs can lead to a wide range of possible environmental outcomes. These outcomes depend on factors such as powertrain type, electricity source, charging patterns, and end-of-life management. Given the complexities of battery systems, a framework is needed to systematically evaluate environmental impacts across battery system life cycle stages, from material extraction and production to use in the EV, through the battery’s end-of-life. We have developed a set of ten principles to provide practical guidance, metrics, and methods to accelerate environmental improvement of mobile battery applications and facilitate constructive dialogue among designers, suppliers, original equipment manufacturers, and end-of-life managers. The goal of these principles, which should be implemented as a set, is to enhance stewardship and sustainable life cycle management by guiding design, material choice, deployment (including operation and maintenance), and infrastructure planning of battery systems in mobile applications. These principles are applicable to emerging battery technologies (e.g., lithium-ion), and can also enhance the stewardship of existing (e.g., lead-acid) batteries. Case study examples are used to demonstrate the implementation of the principles and highlight the trade-offs between them.
One of the most important principles is Principle #6: Design and operate battery systems to maximize service life and limit degradation. We expand Principle #6 to provide guidance and strategies that promote battery health and lifetime extension to promote sustainable and responsible battery management. The goal is to provide practical guidance, metrics, and methods for battery designers, suppliers, EV and electronics manufacturers, users, and material recovery and recycling organizations to accelerate environmental improvements of battery systems in electronics and vehicles.
3:00pm - 3:20pm
Sustainable end-of-life management of electric vehicle Li-ion batteries to maximize resource efficiency
Purdue University, United States of America
U.S. demand for lithium-ion batteries is expected to be $US 30-40 billion by the year 2025. A new generation of hybrid and electric vehicles will drive this growth. Meanwhile, the lifetime of batteries on electric vehicles is about 5-10 years. As the demand for Li-ion batteries increases, so too will the disposal of spent batteries in the solid waste stream. A conservative assumption is that by the year 2035, the US will be disposing of 30,000 tons of Li-ion batteries per year. It is imperative to develop a means to divert these batteries from the solid waste stream and recover the critical materials from the spent batteries to meet the growing future demand. To maximize economic benefits and resource efficiency, it is highly desired to have an integrated end-of-life (EOL) management approach for spent Li-ion batteries to enable reuse, re-manufacturing, and recycling. Current industry procedures of electric vehicle battery re-manufacturers deal primarily with replacing modules under warranty for major automotive companies like Nissan and General Motors. Single-cell replacement is a field that has not been explored in detail.
In this project, a 48 V module from a Chevrolet Volt plug-in hybrid electric vehicle (PHEV) battery was disassembled and the cells were used as a case study. The objectives of this study were to:
1) Develop a working knowledge of the mechanical disassembly process of an EV module, and characterize the performance of battery cells. The determination of cell parameters such as battery capacity, state of health, and state of charge were then compared to their original values to separate faulty cells from healthy cells.
2) Investigate the assembly of good cells for a second-life application. With end-of-life electric vehicle batteries usually at 70-80% of their original capacity, they can be reused for other applications that require less power.
3) Recycle critical materials from the faulty cells. Cobalt and lithium can be obtained from the cathode of cells in battery packs through chemical separation and methods such as bio-leaching. This will decrease the pressure on the continued mining of these elements as future demand increases.
With these goals in mind, researchers developed a small-scale process flow diagram based on work done. Challenges associated with dismantlement and cathode material separation were identified, as well as areas for optimization. Several potential second-life applications such as back-up batteries for small electrical tools, energy storage packs to supplement grid supply, and battery packs for the micro-mobility industry (e-scooters, etc.) are being explored.
To conclude, the used battery packs from electric vehicles still have value embedded in them, and critical materials can be recovered, recycled, and reused. Depending on the state of health of an individual cell, the cell can be reused by assembling it with like cells to make a new battery for second-life applications.
Future work will include the development of a semi-automatic procedure for battery dismantlement on an industrial scale. The use of vision systems, rotating index tables, and automatic guided vehicles are being explored in collaboration with Oak Ridge National Lab, in an attempt to develop a standard disassembly process for various types of electric vehicle battery packs. Single-cell replacement will also be investigated.
This research is supported by the Critical Materials Institute, an energy innovation hub under the U.S. Department of Energy, whose mission is to assure supply chains of materials critical to clean energy technologies — enabling innovation in U.S. manufacturing and enhancing U.S. energy security.