Lecture 9 – Demand Side Management and Storage

Question 1

Due to what issues is energy storage needed?

Answer 1

• Generation issues
• Consumption issues
• Grid issues

Question 2

What comes under generation issues?

Answer 2

• Intermittent generator output is stochastic and hardly controllable
• Ramping constraints for conventional generators

Question 3

What comes under consumption issues?

Answer 3

• Varies with time
• Hardly controllable

Question 4

What comes under grid issues?

Answer 4

• Line capacity is constrained
• Regional differences in generation and consumption patterns induces mismatches

Question 5

What is energy storage used for?

Answer 5

To stabilise the system

Question 6

What is energy arbitrage driven by?

Answer 6

• Driven by individual economic rationale
• buy and store electric energy at low prices (e.g., night, generation peaks)
• sell electric energy at price peaks

Question 7

What is arbitrage potential mainly driven by?

Answer 7

• price spread
• storage round-trip efficiency

Question 8

What is the reduction of curtailment of renewables driven by?

Answer 8

• 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

Question 9

What is a challenge in pursuing the reduction of curtailment of renewables?

Answer 9

Regulatory separation of generation and system operation complicates pursuing this storage objective

Question 10

Why is frequency regulation important?

Answer 10

• 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

Question 11

How is frequency regulation with energy storage carried out?

Answer 11

• Stand-by generation capacity from storage can inject power
• Demand drop can be compensated by storing energy

Question 12

what are the different parameters that need to be taken into account when analysing a storage system?

Answer 12

Consumer parameters
Market parameters
Storage system parameters

Question 13

What are the various storage types from low capacity to high (x-axis)?

Answer 13

Fly wheels
Batteries
CAES
PHS
H2
SNG (methane)

Question 14

What efficiency degrees combine to make the over efficiency degree?

Answer 14

Rectifier efficacy
Storage charging efficieny
Storage self-discharge
Inverter efficiency

Question 15

What are the most impactful storage parameters?

Answer 15

• Storageefficiency
• Storagecosts
• Expected number of charge cycles

Question 16

What are the advantages of EVs (electric vehicles)?

Answer 16

• 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

Question 17

What are the disadvantages of EVs (electric vehicles)?

Answer 17

• 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)

Question 18

What is a future challenge in relation to EVs and what is a possible solution?

Answer 18

• 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.

Question 19

What is the cost composition of charging infrastructure dependent on?

Answer 19

− the offered charging power (single and cumulated)
− the local grid condition
− cabling effort

Question 20

What are the advantages of integrating EV & building the smart grid?

Answer 20

▪ 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

Question 21

What are the disadvantages of integrating EV & building the smart grid?

Answer 21

▪ 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

Question 22

What are some challenges for EVs in relation to mobility Patterns and Grid Integration?

Answer 22

• 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

Question 23

What is the vehicle to grid concept?

Answer 23

• 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

Question 24

What features are necessary for V2G?

Answer 24

− 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

Question 25

What in comparison to normal generators allows EVs to participate in balancing energy markets?

Answer 25

Battery characteristics of fast discharge

Question 26

What prevents V2G from providing medium and base load energy?

Answer 26

• High costs and low total storage capacity prevent V2G from providing medium and base load energy
• Regulation and Spinning Reserves are more profitable for fast responding fleets of EVs participating in V2G