🔋Energy Storage Technologies Unit 13 – Energy Storage System Design & Optimization

Fundamentals of Energy Storage

• Energy storage involves capturing energy produced at one time for use at a later time
• Enables decoupling of energy supply and demand, allowing for more efficient and flexible energy systems
• Plays a crucial role in integrating renewable energy sources (wind, solar) into the grid by mitigating their intermittency
• Helps improve grid stability, reliability, and power quality by providing ancillary services (frequency regulation, voltage support)
• Facilitates peak shaving and load shifting, reducing the need for expensive peaking power plants and lowering energy costs
• Enhances energy security by providing backup power during outages and emergencies
• Supports the electrification of transportation by enabling the deployment of electric vehicles (EVs) and charging infrastructure

Types of Energy Storage Systems

• Mechanical storage systems store energy in the form of kinetic or potential energy
  • Pumped hydro storage (PHS) uses two water reservoirs at different elevations to store and release energy
  • Compressed air energy storage (CAES) stores energy by compressing air in underground caverns or tanks
  • Flywheels store energy in the form of rotational kinetic energy using a spinning mass
• Electrochemical storage systems convert chemical energy into electrical energy and vice versa
  • Batteries, including lead-acid, lithium-ion, and flow batteries, store energy in chemical form
  • Supercapacitors store energy in an electric field between two electrodes
• Thermal storage systems store energy as heat or cold for later use
  • Sensible heat storage uses materials (water, molten salts) to store thermal energy
  • Latent heat storage exploits phase change materials (PCMs) to store and release heat
• Chemical storage systems store energy in the form of chemical bonds
  • Hydrogen storage uses electrolysis to convert electricity into hydrogen, which can be stored and later converted back to electricity using fuel cells
  • Synthetic fuels (methane, methanol) can be produced using excess renewable energy and stored for later use
• Electrical storage systems store energy directly in an electric field or magnetic field
  • Superconducting magnetic energy storage (SMES) stores energy in a magnetic field created by a superconducting coil
  • Capacitors store energy in an electric field between two conductive plates

Energy Storage System Components

• Power conversion system (PCS) converts electrical energy between AC and DC and controls the flow of power between the storage system and the grid
  • Inverters convert DC power from the storage system to AC power for the grid
  • Rectifiers convert AC power from the grid to DC power for charging the storage system
• Storage medium is the material or device that actually stores the energy (batteries, flywheels, compressed air, etc.)
• Balance of plant (BOP) includes all the auxiliary components necessary for the operation of the storage system
  • Cooling systems maintain optimal operating temperatures for the storage medium and power electronics
  • Fire suppression systems protect against thermal runaway and other safety hazards
  • Monitoring and control systems ensure safe and efficient operation of the storage system
• Grid interconnection equipment connects the storage system to the electrical grid
  • Transformers step up or down the voltage between the storage system and the grid
  • Switchgear and protection devices ensure safe and reliable operation of the interconnected system
• Energy management system (EMS) optimizes the operation of the storage system based on various factors (energy prices, grid conditions, user preferences)
  • Forecasting algorithms predict future energy supply, demand, and prices
  • Optimization algorithms determine the optimal charging and discharging schedule for the storage system

Design Principles and Considerations

• Identify the primary application and use case for the energy storage system (peak shaving, frequency regulation, renewable integration, etc.)
• Determine the required power and energy capacity based on the application and desired performance
• Consider the response time and ramp rate requirements for the intended application
• Evaluate the round-trip efficiency of the storage technology and its impact on system economics
• Assess the cycle life and calendar life of the storage medium and its effect on long-term performance and costs
• Analyze the environmental conditions (temperature, humidity) and their influence on system design and performance
• Ensure the system design complies with relevant safety standards and regulations (fire codes, electrical codes)
• Consider the scalability and modularity of the system design for future expansion or adaptation to changing requirements
• Evaluate the capital and operating costs of the system and its economic viability for the intended application

Modeling and Simulation Techniques

• Physics-based models capture the fundamental physical processes governing the behavior of the storage system
  • Electrochemical models describe the charge transfer and mass transport processes in batteries
  • Thermodynamic models capture the heat transfer and phase change processes in thermal storage systems
• Empirical models use experimental data to develop mathematical relationships between input and output variables
  • Equivalent circuit models represent batteries as a combination of resistors, capacitors, and voltage sources
  • Performance curves relate the output power or efficiency of a storage system to its operating conditions
• Data-driven models leverage machine learning techniques to learn patterns and relationships from historical data
  • Artificial neural networks (ANNs) can predict the performance and degradation of storage systems based on past operating data
  • Support vector machines (SVMs) can classify and predict the health state of storage components
• Hybrid models combine physics-based, empirical, and data-driven approaches to leverage their respective strengths
• Model validation and calibration ensure that the models accurately represent the real-world behavior of the storage system
  • Experimental data is used to validate and refine the model parameters
  • Sensitivity analysis identifies the most influential parameters and their impact on model performance

Optimization Strategies

• Objective functions define the goal of the optimization problem, such as minimizing costs, maximizing revenue, or improving system performance
• Decision variables represent the controllable parameters that can be adjusted to optimize the system (charging/discharging power, storage capacity, etc.)
• Constraints specify the limitations and requirements that the optimal solution must satisfy
  • Power and energy capacity constraints ensure that the storage system operates within its physical limits
  • Ramp rate constraints limit the rate at which the storage system can change its output power
  • State of charge (SOC) constraints maintain the storage medium within a safe and efficient operating range
• Optimization algorithms search the solution space to find the optimal values for the decision variables
  • Linear programming (LP) is used when the objective function and constraints are linear
  • Nonlinear programming (NLP) handles optimization problems with nonlinear objective functions or constraints
  • Dynamic programming (DP) optimizes multi-stage decision problems by breaking them down into smaller subproblems
  • Heuristic and metaheuristic algorithms (genetic algorithms, particle swarm optimization) can find near-optimal solutions for complex and high-dimensional problems
• Sensitivity analysis investigates the impact of variations in input parameters on the optimal solution
  • Identifies the most critical parameters and their influence on system performance and economics
  • Helps assess the robustness and reliability of the optimal solution under uncertainty

Performance Metrics and Evaluation

• Power and energy density quantify the amount of power and energy that can be stored per unit volume or mass
  • Gravimetric density measures the power or energy per unit mass (W/kg, Wh/kg)
  • Volumetric density measures the power or energy per unit volume (W/L, Wh/L)
• Round-trip efficiency represents the ratio of energy output to energy input over a complete charge-discharge cycle
  • Accounts for energy losses during the conversion and storage processes
  • Higher round-trip efficiency indicates better energy utilization and lower operating costs
• Cycle life refers to the number of charge-discharge cycles a storage system can undergo before its capacity or performance degrades to a specified level
  • Depth of discharge (DOD) affects cycle life, with shallower DOD generally resulting in longer cycle life
  • Calendar life represents the expected lifespan of the storage system under normal operating conditions
• Response time and ramp rate characterize the speed at which the storage system can respond to changes in power demand
  • Response time measures the delay between a power request and the actual power output
  • Ramp rate indicates the maximum rate of change in power output per unit time (MW/min)
• Reliability and availability assess the ability of the storage system to perform its intended function over its lifetime
  • Reliability is the probability that the system will operate without failure under specified conditions
  • Availability is the percentage of time the system is ready to operate when called upon
• Levelized cost of storage (LCOS) represents the average cost per unit of energy delivered over the lifetime of the storage system
  • Accounts for capital costs, operating costs, and round-trip efficiency
  • Allows for economic comparison between different storage technologies and configurations

Real-World Applications and Case Studies

• Renewable energy integration: Energy storage systems are used to smooth the variable output of wind and solar power plants
  • Kahuku Wind Farm (Hawaii) uses a 15 MW/10 MWh battery storage system to regulate the output of a 30 MW wind farm
  • Hornsdale Power Reserve (Australia) is a 100 MW/129 MWh lithium-ion battery that provides frequency regulation and reserve capacity for the grid
• Peak shaving and load shifting: Energy storage systems are used to reduce peak demand and shift energy consumption to off-peak hours
  • Irvine Smart Grid Demonstration (California) uses a 2 MW/500 kWh advanced battery system for peak shaving and load shifting
  • Orkney Storage Park (Scotland) employs a 2 MW/500 kWh lithium-ion battery to store excess renewable energy and release it during peak demand periods
• Frequency regulation and ancillary services: Energy storage systems provide fast-responding services to maintain grid stability and power quality
  • Laurel Mountain Wind Farm (West Virginia) uses a 32 MW/8 MWh lithium-ion battery to provide frequency regulation and ramp rate control
  • Pillar Mountain Wind Project (Alaska) employs a 1 MW/1 MWh flywheel system to provide frequency regulation and voltage support
• Microgrids and off-grid applications: Energy storage systems enable the deployment of microgrids and off-grid energy systems
  • Alcatraz Island Microgrid (California) uses a 1.5 MW/3 MWh lead-acid battery to provide power for the island's facilities
  • Marble Bar and Nullagine Power Stations (Australia) use a combination of solar PV, diesel generators, and battery storage to provide reliable off-grid power to remote communities
• Transportation and electric vehicles: Energy storage systems are critical for the electrification of transportation and the deployment of charging infrastructure
  • Tesla Supercharger network uses battery storage systems to provide fast charging for electric vehicles
  • Hybrid and electric buses in various cities (Shenzhen, London) use battery storage systems to reduce emissions and improve efficiency