MODELING COMPRESSED AIR ENERGY STORAGE FOR RELIABILITY STUDIES OF SUSTAINABLE POWER SYSTEMS

Environmental concerns arising from the conventional generating sources have resulted in extensive growth of renewable energy sources (RES) such as wind and solar. The inherent variability and uncertainty of RES introduce major concerns in power system planning and operation to maintain an acceptable level of supply reliability and system efficiency. Energy storage systems (ESS) are considered as a potential option to mitigate the challenges associated with large scale RES integration. Bulk-scale ESS such as compressed air energy storage (CAES) are expected to take a prominent role in the future sustainable power system with high penetration of RES. This thesis investigates the reliability benefits of CAES in a wind integrated power system. The reliability contribution of a CAES depends on the operating strategy as well as the technical characteristics. The operating strategy of a CAES is dependent on the number of factors such as the existing market structure, objective of the owner and the intended application. Such factors need to be accurately accounted while developing a reliability model for CAES. This work develops a novel reliability assessment framework for a power system consisting of wind and CAES. The component reliability model of CAES is also developed and incorporated in the overall framework. The applications of CAES to seasonally and diurnally time shift energy are explored. The reliability benefit of CAES, as well as the capacity value increment of wind due to CAES, are quantified. The environmental benefits of CAES from its support to wind power and the financial benefits for a CAES from the existing electricity markets are evaluated. The impact of CAES operation on its potential benefits is analyzed. Furthermore, appropriate models and methodologies are developed in this work in order to quantify to the overall societal benefits of CAES considering the reliability impact, economic aspects, and environmental objectives. The feasible applications of CAES in wind integrated power systems are formulated and the potential benefits of CAES are assessed. The assessment of CAES benefits provide insights to utilities and policy makers in formulating effective policies and regulatory structures that can attract ESS participation, sustain the growth of RES and ensure acceptable supply reliability. In general, the models and analyses in the work can be valuable for stakeholders regarding cost effective and reliable transition of power system towards sustainable solutions

Economic evaluation of battery storage systems bidding on day-ahead and automatic frequency restoration reserves markets

In future electricity systems, not only electricity generation but also frequency stabilization must be provided by low-carbon technologies. Battery systems are a promising solution to fill this gap. However, uncertainties regarding their revenue potential may hinder investments. Therefore, we apply the agent-based electricity market model AMIRIS to simulate a day-ahead market and an automatic frequency restoration reserves market. Demonstrating the model setup, we chose a scenario with high shares of renewable energies. First, we back-test our model with historic market data from Germany in 2019. The simulation results mean day-ahead prices of 39.20 EUR/MWh are close to the historic ones of 38.70 EUR/MWh. Second, we model both markets in a scenario for 2030. The simulated day-ahead market prices are higher on average than observed today, although, we find around 550 h/yr in which the load is fully covered by renewable energies. The variance in simulated prices is slightly higher compared to historic values. Bids on the reserve capacity market are derived from opportunity costs of not participating in the day-ahead market. This results in prices of up to 45 EUR/MW for positive reserve while the prices for negative reserve are 0 EUR/MW. Finally, we evaluate revenue potentials of battery storages. Compared to 2019, we see an improved economic potential and increased importance of the day-ahead market. High power battery storages perform best whereas improvements in round-trip efficiency only marginally improve revenues. Although demonstrated for Germany, the presented modular approach can be adapted to international markets enabling comprehensive battery storage assessments

Reliability Studies of Distribution Systems Integrated with Energy Storage

The integration of distributed generations (DGs) - renewable DGs, in particular- into distribution networks is gradually increasing, driven by environmental concerns and technological advancements. However, the intermittency and the variability of these resources adversely affect the optimal operation and reliability of the power distribution system. Energy storage systems (ESSs) are perceived as potential solutions to address system reliability issues and to enhance renewable energy utilization. The reliability contribution of the ESS depends on the ownership of these resources, market structure, and the regulatory framework. This along with the technical characteristics and the component unavailability of ESS significantly affect the reliability value of ESS to an active distribution system. It is, therefore, necessary to develop methodologies to conduct the reliability assessment of ESS integrated modern distribution systems incorporating above-mentioned factors. This thesis presents a novel reliability model of ESS that incorporates different scenarios of ownership, market/regulatory structures, and the ESS technical and failure characteristics. A new methodology to integrate the developed ESS reliability model with the intermittent DGs and the time-dependent loads is also presented. The reliability value of ESS in distribution grid capacity enhancement, effective utilization of renewable energy, mitigations of outages, and managing the financial risk of utilities under quality regulations are quantified. The methodologies introduced in this thesis will be useful to assess the market mechanism, policy and regulatory implications regarding ESS in future distribution system planning and operation. Another important aspect of a modern distribution system is the increased reliability needs of customers, especially with the growing use of sensitive process/equipment. The financial losses of customers due to industrial process disruption or malfunction of these equipment because of short duration (voltage sag and momentary interruption) and long duration (sustained interruption) reliability events could be substantial. It is, therefore, necessary to consider these short duration reliability events in the reliability studies. This thesis introduces a novel approach for the integrated modeling of the short and long duration reliability events caused by the random failures. Furthermore, the active management of distribution systems with ESS, DG, and microgrid has the potential to mitigate different reliability events. Appropriate models are needed to explore their contribution and to assist the utilities and system planners in reliability based system upgrades. New probabilistic models are developed in this thesis to assess the role of ESS together with DG and microgrid in mitigating the adverse impact of different reliability events. The developed methodologies can easily incorporate the complex protection settings, alternate supplies configurations, and the presence of distributed energy resources/microgrids in the context of modern distribution systems. The ongoing changes in modern distribution systems are creating an enormous paradigm shift in infrastructure planning, grid operations, utility business models, and regulatory policies. In this context, the proposed methodologies and the research findings presented in this thesis should be useful to devise the appropriate market mechanisms and regulatory policies and to carry out the system upgrades considering the reliability needs of customers in modern distribution systems