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René Bañares-Alcántara and Richard Nayak-Luke

The role of ‘green’ ammonia in decarbonising energy

Department of Engineering Science Decarbonising UK Energy workshop 4-6 October, 2017 The Royal Society

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© R Banares-Alcantara

Renewable Energy and Energy Storage

Increased Renewable Energy (RE) penetration requires additional

flexibility.

Energy Storage (ES) can provide it.

• how much energy storage is needed? (capacity)

• for how long we need to store the energy? (duration)

We propose:

use of ammonia (NH3) as a long-duration energy storage vector

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We have developed a methodology to determine the distribution of

short- vs. long-duration Energy Storage (ES) technologies.

The SDI (Storage Duration Index) is a metric that quantifies the

required storage duration and magnitude.

INPUT: Location (RE sources), RE mix, RE penetration

{{ ES losses, ES round-trip efficiency,

demand side management, curtailment }}

The SDI can be the basis to select, size and cost ES technologies.

© R Banares-Alcantara

Storage duration studies

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Lerwick (Shetland Islands): RES supply: 100 MW average ;

50% wind, 50% solar ; 100% RES penetration

ES technology 1 ES technology 2

ES technology 3

Different energy density, CAPEX, round-trip efficiency, losses, etc. © R Banares-Alcantara

Storage Duration Index (SDI)

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Energy Storage technologies

• which ES technologies?

© R Banares-Alcantara

• capacity / duration / cost

• consideration of complete life-cycle, i.e.

harvest / storage / transportation / energy recovery

• energy density

• discharge time / round-trip efficiency

• flexibility: e.g. for power generation and transport systems

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© R Banares-Alcantara

Energy Storage technologies – selection criteria

Y-Values

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Coal

29,900 GWh

14.3 GW

Natural gas

47,100 GWh

32.1+ GW

1 year

1 month

1 week

1 day

1 hour

1 min

1 sec

100 ms

1 kWh 1 MWh 1 GWh 1 TWh Storage

capacity

Release

time

Pumped

Hydro

27.6 GWh

2.90 GW

Batteries

2.34x10-2 GWh

0.0239 GW

Flywheel*

5.56x10-3 GWh

0.400 GW

Storage technologies

Mechanical

Electro-chemical

Chemical

Note: + CCGT (30.9 GW) and

OCGT (1.2 GW)

* EFDA JET Fusion flywheel

Source: presentation by N Olson (NH3 Fuel Association), Rotterdam, May 2017.

Adapted from Hydrogenius Technologies. Nuclear and Oil neglected due to data availability

Estimates from Wilson (2010), MacKay (2008), BEIS DUKES (2016), REA (2010)

© R Banares-Alcantara

Current energy storage technologies

Y-Values

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Chemical

1 year

1 month

1 week

1 day

1 hour

1 min

1 sec

100 ms

1 kWh 1 MWh 1 GWh 1 TWh

Pumped Hydro

Batteries

Flywheel

Storage technologies

Mechanical

Electro-chemical

Chemical

Electrical

Superconducting coil

Capacitor

Redox-flow

Lead-acid

Lithium-ion

Compressed air

Hydrogen

Ammonia

Storage

capacity

Release

time

Source: presentation by N Olson (NH3 Fuel Association), Rotterdam, May 2017.

Adapted from Hydrogenius Technologies. © R Banares-Alcantara

Available energy storage technologies

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NH3

Source: J.R. Bartels, “A Feasibility Study of Implementing an Ammonia Economy”, MSc Thesis, Iowa State

University (2008) © R Banares-Alcantara

H2 vs NH3 costs of production, transportation

and storage

Cos

t [U

SD

/kg

H2]

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Ammonia (NH3) as an Energy Storage option

© R Banares-Alcantara

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Technological characteristics

Current NH3 worldwide production is ~180 MT/y (increasing 50% by 2050)

and represents a market of > 100 bn£/y

Chemical characteristics

Lower Heating Value = 14,100 MJ/m3 (vs. H2: 8,400 or gasoline: 29,800)

Boiling points:

(similar to C3H8)

Stable chemical w/ high H content (x1.3 more H than liquid H2 per unit vol)

(Relatively) safe: non-explosive, narrow flammability range, easy to detect

Ammonia Hydrogen

1 bar 33.3oC 1 bar 253oC

10 bar 20oC 350 bar 20oC

existing infrastructure

easy to transport & store

unlimited storage time

safe

© R Banares-Alcantara

Some information about ammonia (NH3)

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• renewable energy storage medium

as a fuel, NH3 can be used in

• Fuel cells

catalysed decomposition to H2 at > 500oC; also electro- or photochemical;

NH3 poisons PEM fuel cells

• Combustion

- Gas Turbines

can be cracked before combustion for NH3/H2 mix

- ICE engines

can be mixed in NH3-gasoline dual fuel, e.g. see http://nh3car.com

as a commodity,

• fertilisers (biodegradable; consumes 88% of NH3 worldwide production)

• refrigerant

© R Banares-Alcantara

End-use flexibility of NH3

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Haber-Bosch process:

• from H2 and N2

• P = 150 – 250 bar

• T = 300 – 500 oC

• conversion = 15 – 25%

• capacity: 1 – 500 kT/yr

• catalysts: Fe–based and Ru–based

– Fe: not the most active but robust to impurities

– Ru: an order of magnitude more active, but sensitive to impurities

– potential for other modified transition metals, e.g. Co-Mo-N

• Future technologies: obtain NH3 directly from H2O and N2

© R Banares-Alcantara

Current NH3 production process

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• 95% of the H2 produced globally comes from fossil fuels, e.g. through

the Steam Reforming of methane (natural gas)

• currently, to produce NH3

o 1.8% of global fossil fuels consumption

o 420 MT/yr of CO2 are emitted ( 1.3% of global CO2 emissions)

• it is possible to avoid ~90% of the CO2 from SMR at a cost of 74

USD/T (Source: IEA GHG Technical Report 2017-2)

© R Banares-Alcantara

…but H2 for NH3 is produced from natural gas

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‘Green’ ammonia with existing technology

© R Banares-Alcantara

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‘Green’ ammonia can be produced with existing technology from water

(electrolysis) and air (cryogenic separation):

• cheap and readily available raw materials (water + air); natural gas

represents about 75% of production costs

• “green” end products when recovering stored energy (N2 and water;

or N2 and H2)

Source: Morgan, 2013 © R Banares-Alcantara

Energy storage and ‘green’ NH3

Electrolysers,

93.5%

Other,

6.5%

ASU,

0.7%

MVC,

0.3% HB loop,

5.5%

Power

Electrolysers,

65%

Other,

14% ASU,

6%

MVC,

5%

HB loop,

21%

Storage,

3%

CAPEX

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“Thanks to the recent cost reductions of solar and wind

technologies, ammonia production in large-scale plants based

on electrolysis of water can compete with ammonia production

based on natural gas, in areas with world-best combined solar

and wind resources.”

“Only detailed, specific studies with hourly output of solar and

wind can help optimise the respective capacities of solar, wind

and electrolysers, the design of the NH3 plant, and the means

to prevent undesirable disruptions in the synthesis loop.”

Cédric Philibert, Senior Analyst

Renewable Energy Division, IEA

16 May 2017

https://www.iea.org/media/news/2017/FertilizermanufacturingRenewables_1605.pdf

© R Banares-Alcantara

Wind Power

profile

Power from

NH3

H2 production

N2 production

NH3 production

air

H2

N2

NH3 water

Demand

profile

NH3

storage

Energy Storage System (ESS)

surplus

electricity

electricity

electricity NH3

MVC

H2

storage

1. Techno-economic assessment (EngSci)

2. Thermo-catalytic review (Chemistry)

3. Market analysis (Smith School)

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© R Banares-Alcantara

Islanded NH3-based energy storage system

(2015)

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Given a geographical location, i.e. set of RE intermittent profiles, estimate:

• optimal solar/wind/grid supply mix

• size of ESS components

• LCOA (Levelised Cost of Ammonia)

Production cost variables:

• LCOE (Levelised Cost of Electricity)

• electroliser CAPEX per kW of rated power

Production process variables:

• RE sources ratio

• minimum power consumption of ASU/HB process (plant size)

• maximum ramping rate of ASU/HB process [MWh/hr]

Note: the ramping bottleneck is the Haber-Bosch catalysts due to sintering.

© R Banares-Alcantara

Five key variables w/ significant impact on LCOA

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Note: In other locations the LCOE for renewable electricity is currently

significantly cheaper (in Saudi Arabia solar photovoltaic has dropped

to as low as 13.4* GBP/MWh)

2025/30 estimate using

with all five key variables

588 GBP/T

* Masdar and Electricite de France SA’s bid for 300 MW Sakaka project

Source: Bloomberg Markets 3rd October 2017 © R Banares-Alcantara

LCOA sensitivity to LCOE

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Being built at Rutherford Appleton Laboratory, near Oxford

Source: Ian Wilkinson, Siemens.

Siemens 0.3 MW

proof-of-concept plant

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‘Green’ ammonia with future technology

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Reactors with:

- reacting fluid, i.e.

- solid catalyst phase A, e.g. Fe- or Ru-based catalyst pellets

- solid absorption/adsorption phase B, e.g. MgCl2 particles

could drive equilibrium to the right, thus achieving higher conversions.

3H2 N2 2NH3

~100% conversion

Mark Gowers (2016)

© R Banares-Alcantara

Multifunctional reactors

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Produce NH3 directly from H2O and N2 (reduction of energy requirements, CO2

generation and CAPEX)

• electrochemical or photochemical route

– reported synthesis rates in the order of 10–9 mol s–1 cm–2,

at least two orders of magnitude lower than required by industry

– need electro- or photocatalysts with better activity, selectivity and stability

• chemical looping

a) metal to metal nitride

b) hydrolysis of metal nitride to NH3 + metal oxide

c) reduction of metal oxide to metal

this step requires 1800 K (2300 K in some sources)

© R Banares-Alcantara

Future technologies for NH3 production

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Conclusions

© R Banares-Alcantara

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• energy storage is key to Renewable Energy (wind/solar) penetration

• short-duration storage (batteries) is necessary but not enough, long-duration

storage is also needed

• ‘green’ ammonia is a clean option for long-duration ES

• we have developed a model that, for a given location, estimates

o ratio of wind/solar PV

o size of ‘green’ ammonia production plant

o operation of plant (ramping rates)

that minimise LCOA.

• it has becoming possible to produce ‘green’ ammonia with existing

technology that is commercially competitive, i.e.

o potential business game-changer

o up to a 420 MT/y CO2 reduction

© R Banares-Alcantara

Conclusions

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Thank you