Lecture 9 – Demand Side Management and Storage Flashcards
Due to what issues is energy storage needed?
- Generation issues
- Consumption issues
- Grid issues
What comes under generation issues?
• Intermittent generator output is stochastic and hardly controllable
• Ramping constraints for conventional generators
What comes under consumption issues?
• Varies with time
• Hardly controllable
What comes under grid issues?
• Line capacity is constrained
• Regional differences in generation and consumption patterns induces mismatches
What is energy storage used for?
To stabilise the system
What is energy arbitrage driven by?
- Driven by individual economic rationale
- buy and store electric energy at low prices (e.g., night, generation peaks)
- sell electric energy at price peaks
What is arbitrage potential mainly driven by?
- price spread
- storage round-trip efficiency
What is the reduction of curtailment of renewables driven by?
- Driven by system interest to maximize usage of renewable generation
• Avoid shedding of intermittent generation
• Most relevant for wind generation which is mostly uncorrelated with load
What is a challenge in pursuing the reduction of curtailment of renewables?
Regulatory separation of generation and system operation complicates pursuing this storage objective
Why is frequency regulation important?
- Sudden increases and drops in load need to be compensated to maintain frequency stability
- Large frequency deviations can destroy generator equipment – frequency stability is vital
How is frequency regulation with energy storage carried out?
• Stand-by generation capacity from storage can inject power
• Demand drop can be compensated by storing energy
what are the different parameters that need to be taken into account when analysing a storage system?
Consumer parameters
Market parameters
Storage system parameters
What are the various storage types from low capacity to high (x-axis)?
Fly wheels
Batteries
CAES
PHS
H2
SNG (methane)
What efficiency degrees combine to make the over efficiency degree?
Rectifier efficacy
Storage charging efficieny
Storage self-discharge
Inverter efficiency
What are the most impactful storage parameters?
• Storageefficiency
• Storagecosts
• Expected number of charge cycles
What are the advantages of EVs (electric vehicles)?
- No local emissions, suitable for populous urban regions
- Mobility without CO2 emission in the case of CO2 neutral generation
- Very quiet because of electric engine
- High energy efficiency with about 70% in the case of grid charging (without energy recuperation)
- Minimal energy consumption when standing still
- Net buffering of peak current and usage as auxiliary power unit possible
- Low variable operating costs
What are the disadvantages of EVs (electric vehicles)?
- Low range by minor energy storage density of the battery
- High production/purchase costs of the battery
- Durability of the battery lower than vehicle lifetime at current state of the art
- Higher vehicle weight caused by high weight of the battery
- Long charge time of the battery (infrastructure)
- Temperature dependence of the drivability and the durability of the battery
- Missing standards (grid connection)
What is a future challenge in relation to EVs and what is a possible solution?
- EVs are poised to require on average more than 5% of electricity demand in 2030 in Europe.
- Reduction of charging during peak load periods through “managed charging” by controlling charging time, duration, and intensity with vehicle-to-grid (V2G) technology as an enabler.
What is the cost composition of charging infrastructure dependent on?
− the offered charging power (single and cumulated)
− the local grid condition
− cabling effort
What are the advantages of integrating EV & building the smart grid?
▪ EV as storage technology
▪ Net buffering of peak current and usage as auxiliary power unit possible (depends on pricing mechanism)
▪ Ability to provide backup and balancing power → Enables a better integration of renewables
▪ Expansion of smart grids can provide infrastructure for recharging EVs
What are the disadvantages of integrating EV & building the smart grid?
▪ Charging EV ́s at peak load times can foster grid congestions
▪ EV consumes as much as a 3 person household
▪ Long charging times → for fast charging, DC is needed → high investment costs
▪ Standardization needed
What are some challenges for EVs in relation to mobility Patterns and Grid Integration?
• Even during working days over 95% of the vehicles are parked more than 12 h/day
• In rush-hours only about 12% of the vehicle fleet is in operation
→Low capacity factor for driving
• Potential additional Peaks if charging is not coordinated
• High Voltage DC Charging enables shorter charging times, but requires additional equipment
What is the vehicle to grid concept?
- Vehicle to Grid (V2G) is a concept first which considers Electric Vehicles (FC, Battery, PHEVs) as a source for the power system
- Idle vehicles can provide backup and balancing power, since most of the vehicles are parked during the day
What features are necessary for V2G?
− Grid connection with high power capability
− Control or logical connection with grid operator or correspondent intermediary
− Control Infrastructure (and metering) on board of the vehicle
