Solar Hydrogen The Value of Saving Sunshine for a Rainy Day PHIL GRÜNEWALD

The mother of all sustainable energy SUN WIDELY DISTRIBUTED FREE AT POINT OF USE PLENTIFUL 125W m -2  500 kW per person (UK) 10% efficiency and 2% of land mass 1 kW per person

bar tidal, geothermal and nuclear HeatWindHydroBiomassFossil EMBODIED TIME / CONVERSIONS The mother of all sustainable energy

(bar tidal, geothermal and nuclear) HeatWindHydroBiomassFossil The mother of all sustainable energy Photons Direct conversion of photon energy Already reality with PV R UNNING C OST. + T ECHNOLOGY C OST. I NTERMITTENCY. - -

A sustainable energy vector HYDROGEN CARBON : HYDROGEN DEVELOPMENT ABUNDANTLY AVAILABLE (WATER) STORABLE GAS LIQUID HYDRIDE EFFICIENT CONVERSION (FUEL CELL)

Conversion technologies 1.Thermal 2500 K, 0.05 bar for 25% H 2 2.Thermo-Chemical-Cycles Oxidise/Reduce Metal 3.Photo-Biological Grow algae and extract H 2

+ - 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 H2H2 e-e- Q hν e-e- Q Heat as by- product Heat as by- product 1.229V to split water 1.229V to split water External assistance External assistance External Load ? External Load ? Heat aids Process (?) Heat aids Process (?) Poly-generation Conversion technologies PEC device Suitable for small scale applications

CentralisedDecentralised INFRASTRUCTURE LARGE INVESTMENT SUPPLY DEMAND – CATCH22 SMALL SCALE BUILD UP SCALABLE DEMONSTRATION 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 H 2 storage help? Irradiation Demand 24h

The trouble with (average) humans 24h kWh 5min -1 Data: Courtesy of Adam Hawkes 24h 30 days of one month1 day (high and low res.)

Temporal resolution The drawback of limited ramping and finite power rating is only revealed with high temporal resolution data! 18% 8%

Model Thermal Demand Profile Power Demand Profile Irradiation Profile η el. η th. η H 2 … η el. η th. η H 2 … Input DataParameters Generation H 2 – el £ kW -1 … H 2 – el £ kW -1 … Conversion η charge £ Wh -1 … η charge £ Wh -1 … Storage Commercial El. Rate FIT Gas price IRR … El. Rate FIT Gas price IRR … NPV

Model structure Thermal H2H2 H2H2 Electr. AvailableDemand Storage Fuel Cell Unmet AvailableDemand ExcessUnmet Output Storage Electrolyser Gas boiler Feed in Grid

20% 15% 10% 0, 5% Net Present Value [£] H 2 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 [£ kW -1 ]

Optimum Storage Capacity H 2 Storage [kWh] Thermal Storage Capacity [kWh] 0 kWh 10 kWh kWh Net Present Value [£] 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