ENERGY STORAGE
and new energy carriers
T.U. Eindhoven, October 8, 2009
Why storage?
Fluctuations in DEMAND
Fluctuations in SUPPLY
Peak shaving (better efficiency, costs)
Mobile storage: automotive
Fluctuations in DEMAND (1)
Example 1
Electricity:
National
power grid
Fluctuations in DEMAND (2)
Example 2
Typical
domestic
heating
demand
Fluctuations in SUPPLY (1)
Example 1
Solar Energy
flux
(Netherlands)
Intermezzo: Rules of thumb
1 L of oil, gasoline; 1 m3 nat. gas ≈ 40 MJ
≈ 10 kWhth
100 W continuous ≈ ¼ L of oil / day
Solar energy flux (NL) ≈ 100 W /m2hor
Fluctuations in SUPPLY (2)
Example 2
Wind Energy
fluctuations
How to store?
Distinguish
- Heat (long / short term)
- Electricity (large / small scale / mobile)
- Mechanical energy
NOTE:
Efficient conversion electric ↔ mechanical
1. Storing Heat
Simple solution: water (specific heat!)
Short term (day): easy
cf. solar boiler
Long term (year): difficult
Note: ‘RC’ = Rthermal × heat capacity
→ Large volume required
Long-term heat storage in water
Assume 1000 m3 natural gas equiv. = 35 000 MJ
Ignore heat losses (perfect insulation)
Assume water 85 oC to 35 oC → ∆T = 50 K
So 1 m3 holds 50 × 4,2 MJ ≈ 200 MJ
→Needed 175 m3 (swimming pool!)
CONCLUSION: Large Units + Heat pumps…→
Paleiskwartier Winter
Paleiskwartier Zomer
Smart alternatives needed!
Example……
Thermochemical Heat Storage
AB + Heat ↔ A + B
2. Storing electricity
a. LARGE scale
Use conversion Electr. ↔ Mechanical
Example
Artificial lake (‘plan Lievense’): A=12 km2; h=55-70m
∆h= 15 m
mgh = (2 ×1011 kg)(10 ms-2)(50m)
= 1 × 1014 J
= 3 × 107 kWh
1000 MW during 30h (or 20h if efficiency = 2/3)
Substutute for storage: International
electricity exchange
Example: NorNed
Power cable Feda (No) – Eemshaven (NL)
- Submarine, 580 km
- Maximum power 700 MW
Alternative: Use nature
Example:
Hydroelectric Power
Station Vianden (Lux):
1100 MW,
74% overall efficiency
2. Storing electricity
b. Small scale
Batteries and capacitors
Lead battery: 40 Ah×12 V ≈ 0,5 kWh
NiMH battery
Li-ion battery
Li-ion polymer battery
(LiPo)
Supercapacitor
expected:
≈0,03 kWh/kg
≈0,06 ,,
≈0,15 ,,
≈0,20 ,,
≈0,005 ,,
≈0,02 ,,
Capacitors and Batteries
(from: Physics Today, December 2008)
Capacitors for Power….........Batteries for Energy
If storage were no issue….
a Dutch home could be Energy-neutral!
Heat: needed 1000 m3/y of natural gas
Solar supply: 100 m3/y of natural gas per m2
So 10-20 m2
needed
Electricity: needed 400 W average
Solar supply: 100 W/m2
× 15% efficiency = 15 W/m2
So 400/15 m2 = 30 m2 needed
Rules of thumb
1 L of oil, gasoline; 1 m3 nat. gas ≈ 40 MJ
≈ 10 kWhth
100 W continuous ≈ ¼ L of oil / day
Solar energy flux (NL) ≈ 100 W /m2hor
YOUR car electric?
Power for driving ≈ 15 kW
Energy for driving 7 hours ≈ 100 kWh
YOUR car electric?
Power for driving ≈ 15 kW
Energy for driving 7 hours ≈ 100 kWh
Charging?
Charge from standard outlet: 3,5 kW
Charging time ≈ 4 × driving time (!)
….and Hydrogen?
Not ideal for mobile storage: Boiling point 20,4 K
Liquid: Heat of vaporisation small → boil-off inevitable
Gas: compress→ bulky /or heavy (Not ideal gas)
Metal hydrides: as yet heavy
Hydrogen car….so far
CONCLUSION
Nothing beats the comfort of fossil fuel
When driving, nothing beats a tank full of
gasoline,
So…..
…we better make them last!