Energy Storage Technologies

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

Energy storage systems are crucial for modern power grids, enabling efficient use of renewable energy and improving grid stability. They capture energy for later use, allowing for peak shaving, load shifting, and backup power during outages. These systems play a key role in integrating intermittent renewables and supporting electric vehicle infrastructure. Various types of energy storage exist, including mechanical, electrochemical, thermal, chemical, and electrical systems. Each type has unique characteristics and applications. Key components include power conversion systems, storage media, balance of plant equipment, grid interconnection gear, and energy management systems. Design considerations involve capacity, efficiency, and environmental factors.

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


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© 2024 Fiveable Inc. All rights reserved.
AP® and SAT® are trademarks registered by the College Board, which is not affiliated with, and does not endorse this website.