Chapter 14 - Alternatives to batteries Flashcards
What problem are we trying to solve with energy storage?
- Production and demand variations
- Time scale, power, geographical scale
- Mobility
- Willingness to pay (what is the competition?)
- Synergies (simultaneous business cases)
- Pathways (shared technology drives)
How can energy storage help solar?
Solar has production variations on different scales:
- Yearly cycle (summer vs. winter)
- Weather variation (long spells of rain)
- Daily cycle (night vs. day)
- Hourly variation
- Minute variation (sudden overcast)
How can energy storage help wind power?
Wind has no predictable daily cycle.
During winter there can be blocking high pressures
Europe is not a sufficient area to average out variations.
What are the current trends for consumption?
Towards more power, less energy.
Heat pump, induction, point heater, rapdid charging of EV
What is the criteria for successful energy storage systems?
- Power/energy ratio
- Energy cost / kW
- Energy cost / kWh
- Lifetime (cycle life + calendar life)
- Maturity (and future potential?)
- Energy efficiency
- Self discharge
- Limitations of resources/locations
- Suitability for multiple value propositions
- Suitable for all customer groups
- Pathway for market development (e.g. consumer electronics, mobility)
What alternatives to batteries do we have for energy storage?
- Pumped hydro
- Compressed air
- Flywheel
- Superconducting magnetic energy storage
- Super capacitor
- Thermal energy storage
- Hydrogen energy storage
What are the different alternative battery technologies to Li-ion?
- Lead acid
- NaS-batteries
- ZEBRA-batteries
- NiCd-batteries
- Vanadium redox flow batteries
- ZnBr-batteries
What are the pros and cons of pumped hydro?
Pros:
- Mature technology - accounts for 99% of storage capacity worldwide today
- Cheap energy storage (1-20 $ / kWh)
- Negligible self-discharge
Cons:
- High price per power (1128 $ / kW)
- Future development limited by suitable sites
- Not amazing efficiency (~70-80%)
What are the pros and cons of compressed air energy storage?
Pros:
- Can be relatively cheap (2-120 $ / kWh)
- Negligible self-discharge
Cons:
- Cost dependent on storage material
- Natural cites are limited
- Low volumetric density
- Poor efficiency
What are the pros and cons of flywheel energy storage?
Pros:
- Very little maintenance
- Mature
Cons:
- Expensive
- High self discharge
How does a flywheel energy storage work?
It stores electrical energy as kinetic energy in rotation. Magnetic bearing and vacuum minimizes the friction, but still quite a lot of self-discharge.
How does compressed air energy storage work?
Compress ambient air with low-demand electricity, store it underground and run it through a gas turbine to produce electricity during peak demand.
How does a superconducting magnetic energy storage work?
Stores electrical energy in an electric current that does not decay due to superconduction. Requires cooling.
What are the pros and cons of superconducting magnetic energy storage?
Pros:
- Current does not decay
- Can be completely discharged
- Has working capacity installed somewhere in the world
Cons:
- Very high price (1000 - 10000 $ / kWh)
- Requires cooling
How does a supercapacitor work?
Stores electric energy in electric field between two electrodes in liquid or porous dielectric.
What are the pros and cons of supercapacitors?
Pros:
- High discharge rate
- Long lifetimes
Cons:
- High self-discharge
- Expensive
- Voltage changes with charge
How does thermal energy storage work?
Stores electricity as heat
What are the pros and cons of thermal energy storage?
Pros:
- Cheap (3-60 $ / kWh)
Cons:
- Poor electricity-to-electricity solutions
- Low efficiency (60%)
How does hydrogen energy storage work?
Chemical storage in hydrogen gas. Either from gas reforming or electrolysis. Either burned in turbines or run through a fuel cell to utilise energy.
What are the pros and cons of hydrogen energy storage?
Pros:
- Mature storage technologies (compressed in tanks, liquiefied or as metal hydrides
- Potentially cheap
Cons:
- Poor efficiency
What are the pros and cons of a lead acid battery?
Pros:
- Most developed battery technology
Cons:
- Little potential for cost reduction (200 - 400 $ / kWh)
- Short cycle-life - limited potential for energy management
What are the pros and cons of a NiCd-battery?
Pros:
- Mature technology
Cons:
- Toxicity of components
- Little probability of future development
What are the pros and cons of NiMH-batteries?
Pro:
- Mature technology
- High rate capability
- Robust
- Safe
- Suitable for high temperature applications
Cons:
- Lower energy density than Li-ion
- Self-discharge potentially high
What are the pros and cons of NaS-batteries?
Pros:
- No self-discharge?
Cons:
- Requires high operating tempearture
What are the pros and cons of the ZEBRA-battery?
Pros:
- Any?
Cons:
- Considerable self-discharge
What is a flow battery?
A flow battery is a battery where the electro-active components are stored externally in tanks and pumped along the electrodes. Can scale the power and energy density as needed.
What is the pros and cons of vanadium redox flow batteries?
Pros:
- Most mature flow battery
- No self-discharge during stoppage.
- Potential for cost reduction
Cons:
- Cross-transport of vanadium ions across the membrane when active
What are ZnBr-batteries?
Hybrid flow batteries. High energy density, long lifetime and discharge time and large variations in module size. Cost projected to drop rapidly.
How does hydrogen storage capacity compare to battery storage capacity?
Much larger. 1000 Wh / kg for combined hydrogen tank and fuel cell.
Batteries are approaching high 200s.
In what areas are the willingness to pay for hydrogen storage the highest?
H2 as fuel for fuel cell EVs. Other areas, such as for electricity generation, adding to NG-mix, much lower. As feedstock for industry slightly higher again, but not enough to drive massive volumes.
When does cost of electrolysers saturate?
At > 500 Nm^3 / h
When does the cost of liquefaction plant for hydrogen saturate?
At > 5000 Nm^3 / h
Comparing batteries and hydrogen, when does it make sense to use fuel cells + H2 storage and when does it make sense to use batteries? Why?
Fuel cells: For many hours / cycles, but not many cycles
Batteries: When being used for many many cycles
Because the efficiency of batteries are much higher, and over time that will result in savings.
What are the big differences between PEM and SOFC?
PEM:
- Low temperature operation (< 80 C)
- Flexible operation (15 min ramp time)
- 50% efficiency
- Preffered option in cars
- Only hydrogen
SOFC:
- High temperatures (> 800 C)
- Requires stable operation (4 hour ramp time)
- EFficiency up to 60%
- Multiple fuels possible
What are the different storage options for hydrogen from most to least expensive?
- Metal hydride storage
- Compoosite tank
- Glass fibre tank
- Steel tank
- Liquid hydrogen
- Underground storage
In which areas are biofuels the most attractive option for transport?
- Low engine cost (for now…)
- Low tank cost
- High volumetric density
In which areas is hydrogen the preferred option for transport?
- Zero local emissions (with batteries)
- Resource availability
- Gravimetric density
In which areas are batteries the preferred option for transport?
- Energy efficiency
- Zero local emissions (with hydrogen)
- Eventually low engine cost.
How does biofuel cost develop with volume?
In increases due to limited resources. Many bio products have higher value than fuels.
