Re-envisioning a sustainable hydrogen energy economy

Re-envisioning envisioning a sustainable 

hydrogen energy economy 

Assoc. Professor John Andrews 

School of Aerospace, Mechanical and Manufacturing Engineering, 

RMIT University 

24 November 2010 

Presentation to Engineering for Low Carbon Future, 

Dept of Engineering, University of Cambridge 

Email: john.andrews@rmit.edu.au

Topics for today 

• A new vision for a Sustainable Hydrogen Economy 

• The hydrogen skeptics, David MacKay and Steven Chu 

• Our work at RMIT University on Renewable Energy 

Hydrogen Systems 

• Questions and discussion

The hydrogen economy - origins 

“The phrase ‘A Hydrogen Economy’ arose for the first 

time in a discussion between Bockris and Triner of the 

General-Motors Technical Centre, 3 February 

1970.They had been discussing (along with others in a 

Group) the various fuels which could replace polluting 

gasoline in transportation and had come to the 

conclusion that hydrogen would be the eventual fuel for 

all types of transports. The discussion went to other 

applications of hydrogen in providing energy to 

households and industry, and it was suggested that we 

might live finally in what could be called ‘A Hydrogen 

Society’. The phrase ‘A Hydrogen Economy’ was then 

used later in the same conversation”. 

(Bockris 1975:18, Energy: The Solar Hydrogen Alternative) 

RMIT University©2010 SAMME 3

H2 economy

A solar-hydrogen system at the local scale: 

What about a solar-hydrogen houseboat on the Cam 

Energy services 

needed: 

• Motive power 

• Lighting 

• TV, radio, 

other electric 

appliances 

• Water heating 

• Space heating

Solar hydrogen Combined 

Heat and Power (CHP) 

System 

PV ARRAY 

Efficiencies: 

• PV array (13 – 20%, but CPV now 

30-40%) 

• PEM electrolyser (>90%) 

• Storage (pressurise with 

electrolyser, >95%) 

• PEM fuel cell (50 – 60%) 

• Elect-H2-elect roundtrip: ~50% 

• CHP system (in terms of use of H2 

energy): 70-80% 

Hydrogen 

Heat Exchanger 

Slide 6

500 W PEM fuel cell CHP experimental rig 

• Utilising the heat from the 

fuel cell as well the electricity 

can increase the cell’s 

overall energy efficiency from 

~30-55% for electricity 

generation only, to ~60-80% 

for heat and power 

generation 

See Shabani, Andrews and Watkins 

(2010); Shabani and Andrews (2011)

Solar-hydrogen system for a houseboat 

• Houseboat 19 m x 1.8 m, cover 25% area with PV panels 

• 1.3 kW peak PV capacity 

• Cambridge solar radiation 1050 kWh/m 2 /y 

• Assume 30% electricity demand met directly, 70% via H2 and fuel cell 

• Could then supply continuously just over 2 kWh/d throughout year 

• 3.2 kg H2 store needed. If current best metal hydride: mass 260 kg, vol 260 L 

• Use fuel cell heat for water heating. Would need other fuel for space heat 

• Enough electricity for frugal on-board living. 

• Would need more PV (or an aerogenerator) and larger H2 storage if H2 used 

for motive power via electric motor too. 

Slide 8

The original vision of a hydrogen economy: 

• Conceived at a time when the primary concern was running out of oil 

and natural gas (Limits to Growth type arguments) 

• Impact of rising levels of carbon dioxide in atmosphere on climate had 

been only dimly realised 

• Large-scale hydrogen production by electrolysis of fresh or sea water 

using large solar power stations located in hot remote parts of the 

world (most notably the desert regions of North Africa, Saudi Arabia, 

and Australia), or nuclear fission reactors. 

• Hydrogen transmitted to distant population centres by very long 

pipelines for consumption in all sectors of the economy 

• (later) production of hydrogen from natural gas and coal too 


Drivers towards a H2E 

Source: NREL 2005

Renewable paths to hydrogen 

>2000 K 

Source: NREL 2005

Where does hydrogen fit in a global sustainable energy 

strategy 

ENERGY 

EFFICIENCY 

NUCLEAR 

POWER 

ELECTRICITY 

RENEWABLES 

HYDROGEN 

+ 

C 

C 

S 

NATURAL 

GAS 

COAL

Recent ‘sustainable’ energy scenario based on hydrogen 

• HyWays, 2007, Roadmap EU Research Project (Integrated Project) 

(http://www.hyways.de/index.htmls) (Figs below from Doll and Wietschel, 2008) 

Energy for H2 production: 

• Nuclear dominant (31%) 

• Natural gas (steam reforming) (26%) 

• Coal (integrated gasification combined cycle) 

(14%) 

• Renewables (27%) 

Nuclear ( 

In max H2 scenario, 

transport emissions more 

than 60% lower than 2000 

levels by 2050

Costs of producing hydrogen from renewables 

• Solar PV – PEM electrolyser (Melbourne insolation) 

• PV 8000 US$/kW; Electrolyser 1500 US$/kWe: 22 US$/kg 

≡ 3.2 US$/L petrol (current petrol price in Australia US$1.2/L) 

• PV 2000 US$/kW; Electrolyser 1000 US$/kWe: 

≡ 7 m/s) – H2 

production cost should be lower than for PV

Studies are showing H2 for transport can 

play major role in reducing emissions and 

dependence on oil by 2050. 

But a major portion of the H2 required is 

assumed to be produced using nuclear 

power and to a lesser extent fossil fuels. 

Can we construct a Sustainable Hydrogen 

Economy on just energy efficiency plus 

renewables

Key differences between the original hydrogen economy 

(HE) and the sustainable hydrogen economy (SHE) 

• SHE set firmly in the context of zero greenhouse gas emission economy in 

terms of both the production of hydrogen from renewables and consumption, 

rather than just response to depleting fossil fuels 

• SHE involves decentralised distributed production of hydrogen from a wide 

variety of renewables and feedstocks, rather than centralised production from 

mainly solar and wind energy (and possibly nuclear), and very long distance 

transmission of hydrogen via pipelines, as in HE 

• In SHE, hydrogen and electricity play complementary roles as energy vectors, 

and hydrogen and batteries complementary roles as energy stores, in the 

transport, industrial, commercial and residential sectors. 

• SHE focuses exclusively on renewables, coupled with an equally strong 

emphasis on energy efficiency and demand management 

• In ideal SHE form, no hydrogen from fossil fuels, whether steam reforming of 

natural gas, or integrated gasification combined cycle coal-conversion with 

carbon capture and storage 


Seven principles underlying the SHE vision: 

1. A hierarchy of sustainable hydrogen production, storage and distribution 

centres relying on local renewable energy sources 

2. Hydrogen production from a range of renewables and feedstocks, without 

dependence on nuclear fission power or carbon capture and storage 

3. Minimising the hydrogen pipeline distribution network by distributed 

production of hydrogen, and complementary use of hydrogen and electricity 

as energy vectors 

4. Recognition of the complementary roles of hydrogen and battery storage 

across a range of transport vehicles and transport services 

5. Use of hydrogen for longer-duration energy storage on centralised grids 

relying extensively on renewable energy inputs 

6. Employment of bulk hydrogen storage as strategic energy reserve to 

guarantee national and global energy security in a world relying increasingly 

on renewable energy 

7. Concentration of hydrogen refuelling for most transport modes at a relatively 

small number of strategic locations. 


1. Hierarchy of sustainable hydrogen centres relying on 

local renewables 


Sustainable hydrogen centre 

hierarchy diagram - Legend 


Coastal Hydrogen Centre (CHC) 


H 2 

Electrolyser 

Fuel Cell 

Power 

Station 

Vehicle 

Fuelling 

Stations 

LH2 

Plant 

Electricity 

Hydrogen 



• Similar to OHC but land based 

• Locate close to major cities and energy-intensive industrial areas 

• Could employ either sea water or fresh water electrolysis 

• Hydrogen from natural gas could supplement renewables supply in 

short term 

• Bulk storage of hydrogen gas underground in depleted natural gas or 

oil reservoirs, excavated rock caverns, solution-mined salt caverns, or 

aquifers (cf. Foh et al. (1979), Taylor et al. (1986); ICI Teeside, UK) 

• Local pipeline transmission of hydrogen to fuelling stations for 

transport applications – road, rail, sea and air 

• Hydrogen fed to fuel cell power stations for inputting electricity into 

main grid when primary renewables insufficient 

• Excess grid electricity fed to electrolysers to produce hydrogen 


Inland Hydrogen Centre (CHC) 

Inland Hydrogen Centre (IHC) 

H 2 

Electrolyser 

Fuel Cell 

Power 

Station 

Vehicle 

Fuelling 

Stations 

LH2 

Plant 

Electricity 

Hydrogen 


Inland Hydrogen Centre (IHC) 

• Distributed throughout the populated regions of a country, particularly 

near major inland cities, regional towns and industrial facilities 

• Hydrogen produced from local solar and wind power by electrolysis of 

fresh water, by photolysis of fresh water (if proven viable), from 

regional biomass resources, or excess grid electricity 

• Hydrogen from natural gas could supplement renewables supply in 

short term 

• Medium-scale bulk storage in nearby hydrogen storage facilities 

• Hydrogen supplied via local distribution network to: 

– road and rail transport 

– medium-scale fuel-cell power plants to supply local back-up electricity to 

the centralised grid to ensure continuous supply with minimal transmission 

losses 


Complementary roles of hydrogen and battery storage 

across a range of transport vehicles and services 

• Hydrogen can provide long-term storage, without significant losses 

(just like fossil fuels) 

• Batteries have superior roundtrip energy efficiency (electricity to 

electricity) for shorter duration storage 

• Batteries allow energy recovery via regenerative braking 

• Hydrogen has superior gravimetric and volumetric energy densities 

and hence gives greater travel range 

• Only hydrogen likely to be suitable for medium and long-distance 

road, rail and sea transport 

• Liquid hydrogen most suitable non-petroleum substitute fuel for jet 

and other aircraft 


Hydrogen FC and battery systems: basic on-board 

components 

HYDROGEN 

IN 

H2 STORAGE 

H2 

FUEL CELL 

ELECTRICITY 

OUT 

O2 FROM 

AIR 

ELECTRICITY 

IN 

ELECTRICITY 

OUT 

BATTERY BANK



Storage material and system 

Gravimetric: 

• US DoE target 2015 for H storage material: 1.08, system 0.35 kWe/kg (3x) 

• MH achieved: material 0.47, system 0.25 kWe/kg (~2x) 

• CH achieved: material 0.65, system 0.29 kWe/kg (~2x) 

Volumetric: 

• US DoE target 2015 for H storage material: 0.79, system 0.31 kWe/L (~2.5x) 

• MH achieved: material 0.47, system 0.25 kWe/kg (just under 2x) 

• CH achieved: material 0.51, system 0.26 kWe/kg (~2x) 

• All these energy densities assume FC efficiency of 0.5 


Honda FCX Clarity hydrogen car 

•Honda and and Nissan planning commercial 

production of HFC cars by 2015 

•Toyota planning HFC car for $50 000 by 2015 

Source: http://world.honda.com/news/2008/4080702FCX-Clarity/ 2 July 2008 


Specifications of Honda FCX Clarity 

Power train 

Number of occupants 4 

Motor 

Fuel cell stack 

Max. output 

Max. torque 

Type 

Type 

Max. output 

100kW 

256N·m 

AC synchronous electric motor 

(permanent magnet) 

PEMFC 

(Proton Exchange Membrane Fuel Cell) 

100kW 

Lithium ion battery Voltage 288V 

Fuel 

Type 

Storage 

Tank capacity 

Dimensions (L × W × H) 

Vehicle weight 

Maximum speed 

Energy storage 

Compressed hydrogen 

Pressurized hydrogen tank 

(35MPa) 

171 liters 

4,835 × 1,845 × 1,470mm 

1,635kg 

160km/ h 

Lithium ion battery 

Source: http://world.honda.com/news/2008/4080702FCX-Clarity/ 2 July 2008 


Towards sustainable transport 

Horses (and feed!) for courses! 

• Supportive mode shifts to achieve sustainability 

• Appropriate fuels and storage technology by transport service 


Transport service Sustainable transport shifts Technology Primary energy source 

Urban short trip (

Hydrogen for longer-duration energy storage on 

centralised grids relying extensively on renewables 

Main options: 

• Batteries 

• Supercapacitors 

• Thermal storage, particularly for night-time supply with solar-thermal power 

– good for short-term storage, not for longer term (weeks to six months) 

• Geothermal power stations 

– can supply continuous power but total resource limited and far from cities 

• Biomass 

– Useful but limited power from waste incineration and CHP 

• Large-scale grid covering vast geographical area with distributed renewables 

– complementarity over time of variable inputs reduces need for energy 

storage 

– Still seasonal variation, long-distance power transmission 

– Some guaranteed energy supply still required 

HENCE SOME HYDROGEN STORAGE AND FC POWER INPUT NEEDED 


Seasonal variation in wind power 

Max 11 knots, min 8 knots 

Power proportional to v 3 

Max power is 2.6 x min power, so major seasonal variation 

Source: Bureau of Meteorology, UK 


Seasonal variation of wave power - UK 

Source: Graham Sinden, “Wave and tidal power: resource, grid and integration”, Environmental 

Change Institute, University of Oxford

Seasonal variation of wave power - Australia 

Source: J. Fry, 2010, Ocean waves, energy and the southern Australian coast, M Eng 

(Sustainable Energy) thesis (RMIT University, Melbourne)

Bulk hydrogen storage as strategic energy reserve to 

guarantee national and global energy 

• Need for strategic energy reserve with 100% reliability to meet 

demand in periods of low availability of renewables, and during major 

breakdowns or catastrophes (such as volcanic eruptions, cyclones, 

bushfires, floods, or droughts, or wars or terrorist attacks) 

• Bulk hydrogen storages as integral parts of offshore, coastal and 

inland hydrogen centres can meet this need: 

– role akin to fossil fuels today, except that hydrogen can be 

regularly replenished using the earth’s renewable energy income 


The hydrogen skeptics 1: 

David McKay, Sustainable Energy without the Hot Air (2009) 

• “...hydrogen is a hyped-up bandwagon... Hydrogen is not a miraculous source 

of energy; it’s just an energy carrier, like a rechargeable battery. And it is a 

rather inefficient energy carrier, with a whole bunch of practical defects” 

• “where is the energy to come from to make the hydrogen 

• “...converting energy to and from hydrogen can only be done inefficiently – at 

least with today’s technology” 


The H-skeptics 1: David McKay 

Counter arguments 

• Indeed hydrogen is an energy carrier, but with some unique advantages: 

– Higher gravimetric and volumetric energy densities than batteries allows 

vehicle ranges near to today’s petrol and diesel, with short recharge time 

– Fuel for long-distance trucks, jets, ships, trains (where too costly to 

electrify) 

– Can provide longterm seasonal storage on grids in distributed manner at 

roundtrip efficiencies of ~50%, and strategic bulk energy reserve 

• Make hydrogen from renewables, and then a zero emission fuel 

• Use of millions of battery electric vehicles as switchable load on grid to cope 

with variable input from renewables is of questionable viability 

• Arguably battery electric vehicles as the solution is a hyped up bandwagon. 

Better to have complementary use of hydrogen and batteries

The hydrogen skeptics 2: 

Steven Chu, US Secretary of State for Energy 

"Right now, the way we get hydrogen primarily is from reforming gas. That's not an ideal 

source of hydrogen...The other problem is, if it's for transportation, we don't have a 

good storage mechanism yet. What else The fuel cells aren't there yet, and the 

distribution infrastructure isn't there yet. In order to get significant deployment, you 

need four significant technological breakthroughs. If you need four miracles, that's 

unlikely. Saints only need three miracles." Interview with The MIT Technology Review, 

May 2009 

Counter arguments: 

• Make hydrogen from a range of renewables in distributed way 

• Compressed H2 gas at 350 bar already meets US storage targets and is practical. In 

future metal hydrides, chemical hydrides, or carbon based hydrogen storages likely to 

replace compressed gas 

• Fuel call cars, buses, tractors do exist and are functioning well. Indeed further work 

needed to reduce costs, lower mass, extend membrane electrode assembly lifetimes 

• Distributed H2 production and copnsumption minimises distribution infrastructure costs, 

but obviously to substitute substantially for petroleum fuels major investment will be 

needed 


SHE is a promising vision, but advantages need proving. 

Next steps: 

• Apply this vision to specific countries or groupings of nations by 

conducting detailed energy-economic-environmental modelling to 

quantify the key characteristics of SHE in particular contexts: 

– follow-up to US National Hydrogen Association’s (2009) study The Energy 

Evolution; rerun HyWays with modified SHE inputs; develop another 

Mackay-type scenario for UK – Plan H 

– is energy efficiency plus renewables enough 

– e.g. would need to increase electricity generation by over 

100% to produce enough H2 to substitute for all petrol and 

diesel used for transport in Australia 

• Conduct evaluation of overall economic, environmental and social 

benefits of SHE compared with alternative scenarios. 


SOLAR AND WIND HYDROGEN SYSTEMS FOR 

REMOTE OR OTHER STANDALONE POWER SUPPLY

Grand goal 

• Autonomous, zero-emission and economically -competitive systems for 

production of hydrogen by electrolysis from solar and wind energy sources, 

and utilisation for electricity and heat supply in remote or other standalone 

applications 

• Application areas: 

– Remote area power supply (high demand in Australia and 

internationally) 

– Households, farms, indigenous communities, villages, small towns 

– Remote telecommunications, meteorological, other monitoring stations 

– Island power supply 

– Mining, mineral processing, agricultural, industrial facilities far from grid 

– Zero-emission option for rural electrification in developing countries 

– Plus houseboats on the Cam! 

Slide 43

The main components of the hydrogen subsystem: 

1. Proton Exchange Membrane (PEM) electrolyser

The reversible electrolysis – fuel cell reaction used in PEM cells 

But in practice different catalysts needed on O-side to get good 

performance in both modes

Storage

Solid state storage 

Metal hydrides: M + H 2 

MH 2 

Forward: increase pressure, remove heat 

Backward: decrease pressure, add heat 

Mg, Li, Al, Bo, Na, La, Ni…

A large-scale metal hydride storage (European Hydrogen 

and Fuel Cell Platform, 2007)

Unitised Regenerative Fuel Cells (URFCs)

Water in 

Power from 

solar/wind/other source 

Hydrogen 

Storage 

H 2 

O 2 

Charge cycle 

URFC 

Charge cycle 

Discharge cycle 

Discharge cycle 

O 2 

Oxygen 

Storage 

Power out 

Water out 

A schematic of a unitised regenerative fuel cell system (URFC) 

Slide 51

E 

▲ 

Oxygen side 

Anode 

Hydrogen side 

2e – 

Cathode 

▼ 

M 

O 

D 

E 

½O 2 

H 2 O 

nH 2 O 

2H + 

2e – H 2 

H 2 O 

F 

C 

½O 2 

2H + 

M 

O 

D 

E 

H 2 O 

Cathode 

▲ 2e – 

Oxygen side 

H 2 

Anode 

2e – ▼ 

Hydrogen side 

Load 

URFC design with oxygen and hydrogen electrodes remaining the same (but cathode and anode interchanging) on change 

between modes 

Slide 52

New theoretical model of URFC 

• Covers both electrolyser (E) and fuel cell (FC) mode operation 

• Based on Butler-Volmer equations for both hydrogen and 

oxygen electrodes 

• Additional terms based on logistic function to incorporate 

saturation effects at high current densities in both modes 

• Includes impacts on cell potential of membrane proton 

conductivity, internal resistance, and electrical conductivity of 

endplates and gas diffusion backing layers 

Slide 53

Slide 54 

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j 

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Oxygen electrode 

Hydrogen electrode 

Use same 

equations for both 

modes by 

changing signs of 

overpotentials (η O 

and η H ) and hence 

current densities 

between modes

URFC model outputs - 2 

• Fitting modelled V-I curves to experimental curves 

• Finding best values for exchange current densities and charge transfer coefficients for both electrodes, and saturation current 

densities in E and FC modes 

2.5 

Voltage, [V] 

2 

1.5 

1 

0.5 

O 

α = 0.4400 

H 

α = 0.8174 

O 

j 

O = 4.77x10 -9 A/cm 2 

H 

j 

O = 7.02x10 -4 A/cm 2 

sat 

j 

E = 0.2 A/cm 2 

sat 

j 

FC = 0.165 A/cm 2 

E ‐ mode ‐ Theoretical model curve 

FC ‐ mode ‐ Theoretical model curve 

E ‐ mode ‐ Experimental curve 

0 

‐0.15 ‐0.10 ‐0.05 0.00 0.05 0.10 0.15 0.20 

FC ‐ mode ‐ Experimental curve 

C urrent Density, [A/c m 2 ] 

URFC cell constructed at RMIT: active membrane area 5 cm2; catalysts 

- 4 mg/cm2 Pt black on H side and 4 mg/cm2 Pt black on O-side 

Slide 55

URFCs: main technical challenges 

• Design of bifunctional oxygen electrodes 

• Increasing roundtrip energy efficiency 

• Extending lifetime 

• Stack design 

• URFC energy storage system design 

• Lowering unit costs 

Slide 56

Optimal coupling of photovoltaic panels with PEM 

electrolysers in solar/wind hydrogen systems for 

remote power supply

Conventional and direct coupling of PV array and 

electrolyser 

PV Array 

DC-DC 

Converter/MPPT 

Electrolyser 

Conventional coupling of PV-PEM electrolyser 

Direct coupling of PV-PEM electrolyser

V – I characteristic of PV panel and maximum power 

point (MPP) curve 

Current, I (am p) 

5 

4 

3 

2 

1 

0 

G=1000 W/m 2 

900 

700 

500 

300 

100 

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 

Voltage, V (volt) 

MPP 

Simulated I-V characteristics curve of BP 275 (75 W) solar panel showing 

maximum power point (MPP) line 

Slide 59

PEM electrolyser characteristics 

5 

Current, I (amp) 

4 

3 

2 

1 

0 

5 6 7 8 9 10 11 12 13 14 

Voltage, V (volt) 

Experimental I-V characteristics curve of StaXX7 (50 W) PEM 

electrolyser 

Slide 60

PV-electrolyser matching 

MPP 

Electrolyser 

Current, I 

Voltage, V 

Matching of maximum power point line of a PV module with currentvoltage 

characteristic curve of a PEM electrolyser by changing the seriesparallel 

stacking configuration in both the PV module and electrolyser 

Slide 61

Series—parallel stacking of PV panels and PEM 

electrolysers 

PV array 

Electrolyser bank 

Slide 62

Optimum coupling combination 

• 4 PV modules in series—5 electrolyser stacks in series 

• Calculated total energy loss over a full year is only 5.3%, or about 20.5 kWh, 

compared to perfect maximum power point matching 

• Potential annual hydrogen production from this combination is about 7.8 kg 

• Unit cost of hydrogen production for this combination is about $22/kg (~0.56 

$/kWh) when PV and electrolyser capital costs are $8000/kW and $1500/kW 

respectively 

Slide 63

Direct coupling of RMIT 2.4 kW PV array with CSIRO 2 

kW PEM electrolyser 

2.4 kW roof mounted 

PV array at RMIT 

Bundoora East 

2 kW PEM Electrolyser (Oreion( 

Alpha 1) 

Slide 64

Hydrogen lab and safety system 

Slide 65

RMIT fuel cell truck project 

1/14 scale radio controlled truck model 

30 W PEM fuel cell from 

FuelCellStore

Conclusion 

• Hydrogen has a key role to play in a sustainable energy economy based mainly on 

energy efficiency and renewables 

• H2 not popular in some countries currently (e.g USA, Australia and UK) 

• But when oil prices begin to rise again and supply constraints come into play, interest in 

hydrogen will be resurgent. 

• Sustainable energy strategies and the enabling technologies 

provide some great challenges and opportunities for today’s 

undergraduate and postgraduate students 

Acknowledgement: 

Thanks to Adrian Caltabiano for drafting SHE and Sankey diagrams

Re-envisioning a sustainable hydrogen energy economy

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