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Solar Hydrogen
The Value of Saving Sunshine for a Rainy Day
PHIL GRÜNEWALD
The mother of all sustainable energy
SUN
WIDELY DISTRIBUTEDFREE AT POINT OF USEPLENTIFUL 125W m-2 500 kW per person (UK)
10% efficiency and 2% of land mass
1 kW per person
bar tidal, geothermal and nuclear
Heat Wind Hydro Biomass Fossil
EMBODIED TIME / CONVERSIONSEMBODIED TIME / CONVERSIONS
The mother of all sustainable energy
(bar tidal, geothermal and nuclear)
Heat Wind Hydro Biomass Fossil
The mother of all sustainable energy
Photons
Direct conversion of photon energyAlready reality with PV +
-
-
A sustainable energy vector
HYDROGEN
CARBON : HYDROGENDEVELOPMENT
•ABUNDANTLY AVAILABLE (WATER)
•STORABLE •GAS•LIQUID•HYDRIDE
•EFFICIENT CONVERSION (FUEL CELL)
Conversion technologies
1. Thermal• 2500 K, 0.05 bar for 25% H2
2. Thermo-Chemical-Cycles• Oxidise/Reduce Metal
3. Photo-Biological• Grow algae and extract H2
+-
Electrolyser
PV
4. Photo-Electro-Chemical• Combines Photovoltaic and Electrolyser
Conversion technologies
+-
4. Photo-Electro-Chemical• Combines Photovoltaic and Electrolyser
Conversion technologies
PV + Electrolyser
4. Photo-Electro-Chemical• Combines Photovoltaic and Electrolyser
PEC device
PEC device
H2
e-
Q
hν
e-
Q
Heat as by-
product
Heat as by-
product
1.229V to split water
1.229V to split water
External assistance
External assistance
ExternalLoad ?
ExternalLoad ?
Heat aids Process (?)
Heat aids Process (?)
Poly-generation
Conversion technologies
PEC device
• Suitable for small scale applications
Centralised Decentralised
INFRASTRUCTURELARGE INVESTMENTSUPPLY DEMAND –
CATCH22
SMALL SCALE BUILD UPSCALABLEDEMONSTRATION PROJECTS
- +++
--
Infrastructure
But does it make economic sense ?
SUN HYDROGEN ECONOMICS
1. How to model a PEC device?2. Which parameters matter?3. What configuration is best?4. How does PEC compare to alternatives?
OBJECTIVES
The trouble with the sun• Irradiation not on demand• Poor temporal correlation with demand• PV / solar thermal don’t displace generation capacity
???Can H2 storage
help?
Irrad
iatio
n
Dem
and
24h 24h
The trouble with (average) humans
24h
kWh
5min
-1
Data: Courtesy of Adam Hawkes24h
30 days of one month 1 day (high and low res.)
Temporal resolutionThe drawback of limited ramping and finite power rating is only revealed with high temporal resolution data!
The drawback of limited ramping and finite power rating is only revealed with high temporal resolution data!
18%
8%
ModelModel
ThermalDemandProfile
PowerDemandProfile
IrradiationProfile
η el.η th.η H2
…
η el.η th.η H2
…
Input Data Parameters
Gen
erati
on H2 – el
£ kW-1
…
H2 – el
£ kW-1
…
Conv
ersi
on η charge
£ Wh-1
…
η charge
£ Wh-1
…Stor
age
Commercial
El. RateFITGas priceIRR
…
El. RateFITGas priceIRR
…
NPV
Mod
el s
truc
ture
ThermalThermal H2H2 Electr.Electr.
Available Demand
DemandStorageStorage
Fuel CellFuel Cell
Unmet
Available Demand
Demand
Excess Unmet
Output
StorageStorage
ElectrolyserElectrolyser
Gas boilerGas boiler Feed inFeed in GridGrid
20%
15%
10%0, 5%
Net
Pre
sent
Val
ue [£
]
H2 conversion efficiency
Thermal conversion efficiency
Conversion Efficiency
PRELIMINARY RESULTS - EXAMPLE
How does a PEC device compare to- PV- PV + electroyser- Solar Thermal
THE BIG QUESTION…
Installation cost [£ kW-1]
NPV
[£ k
W-1
]
Optimum Storage Capacity
H2 Storage [kWh]
Thermal Storage Capacity [kWh]
0 kWh
10 kWh
20-40 kWh
Net
Pre
sent
Val
ue [£
]
PRELIMINARY RESULTS - EXAMPLES
To get meaningful model outputs we need good input data- More detailed analysis of storage parameters- Understand PEC efficiency trade offs
FUTURE WORK
1. How to model the performance of a PEC device?2. Which parameters matter?3. What configuration is best?4. How does PEC compare to alternatives?
OBJECTIVES
CONCLUSION
Model produces meaningful results• NPV with respect to base case• Comparison with solar technologies• Automated processing with 2 control variables• Good data available for demand and generation
But• Many parameters are not well understood
