Geological Energy Storage Mark Wilkinson Geo Sciences University

Geological Energy Storage Mark Wilkinson Geo. Sciences, University of Edinburgh

Why store energy? • Renewables: match supply - demand • Economics – cheap in summer • Energy security Drivers • Volatile oil / gas / energy prices • North Sea fields old / depleted • C-emissions reduction

Why store energy? Daily: batteries; smart use of electric devices e. g. fridges Annual: only geology can match the scale

Energy storage: the old-fashioned way Wikipedia: Captain-tucker www. bbc. co. uk/news/uk-scotland-edinburgh-east-fife-29500069

Existing storage >30 large caverns in use in UK Image: BGS. AC. UK

Porous Rock Storage • CH 4 and H 2: ‘Cushion gas’ – expensive • Good subsurface knowledge • Confirmed integrity • Confining structure e. g. dome -> Use depleted gas reservoir

Rough Gas Storage Facility http: //watt-logic. com/2016/09/12/rough-outage/ 2. 7 km deep; c. 30 wells; 3. 3 billion m 3; 9 days UK supply

(Depleting) Natural Gas Fields Rough G. S. F. 150 km http: //pubs. usgs. gov/bul/b 2211. html

Rotliegend Sandstone, Permian, nr Inverness

Salt (halite) seals – no porosity and self-seal if fractured! http: //www. amusingplanet. com/2015/11/the-realmonte-salt-mine-in-sicily. html

H 2 Present day… Source: Hydrogen Guide, ARUP

https: //www. engineering-airliquide. com/steam-methane-reforming-hydrogen-production The future? ‘Green’ H 2 = electrolysis of water ‘Blue’ H 2 = shift reaction from fossil Fuel cells / turbines -> electricity Fuel for cars? fuel (+CCS) = steam methane Gas network for heating? reforming (image)

H 2 storage in porous rock Important slide – most people have NO idea what the subsurface is like! 1 mm

Compare seasonal hydrogen store with similar natural gas one - Working gas volume? (STORED ENERGY) - Deliverability? (POWER) - Potential problems e. g. leakage, biological activity - Use the Rough Gas Storage Facility parameters

Leakage (as gas) and diffusion - Direct leakage of gas could be neglected in a natural gas reservoir if integrity is preserved - Dissolution + diffusion in underlying aquifer + cap rock = 0. 05% H 2 after 12 months (Amid et al, 2016).

Possible reactions with rocks Experiments, expose sandstone core to H 2 (Henkel et al. (2014): • increase in surface area dissolution of carbonate minerals (photomicrographs do not show textures) • micro-CT images does show dissolution? • no control samples (i. e. without H 2), • brine saturated with CO 2, which is not realistic for H 2 storage Model reaction (Amid et al. , 2016, Phreeqc software): Sandstones with clay – no reaction Fe-oxides – no reaction Sulphides: almost to complete conversion =>elemental sulphur and sulphides, could include H 2 S, p. H dependant

Hydrogen would react with carbonate minerals Limited by accumulation of Ca 2+

Hydrogen could also react with dissolved CO 2, to complete conversion, through the Sabatier reaction, CO 2 + 4 H 2 → CH 4 + 2 H 2 O CO 2 can be supplied from: gas phase, dissolved in water, (depending on p. H) dissolution of carbonates (limited by Ca accumulation? ) Makes CH 4 – not a big problem? AND: will ‘quickly’ run out of CO 2?

Biological activity 120 °C 80 °C 40 °C Thermophilic Bacteria / Archaea Hyperthermophilic Bacteria / Archaea ! Microorganisms utilize CO 2 & sulphur compounds - consume hydrogen

Biological activity – findings for the Sabatier reaction - Monod Equation: most conversion of residual CO 2 occurs in first storage cycle. - Hence, losses in the first year only - Worst case scenario 3. 7% of hydrogen lost - Methane by-product probably not much concern? (1 example of town gas H 2 -> methane, Smigan et al. , 1990)

Energy Storage Capacity vs Methane - Larger molar volume -> less H 2 stored than methane - Better flow characteristics -> greater Working Gas Capacity to total volume - Heat value of hydrogen lower than methane -> effective energy storage of 42% of natural gas

2500 GWh 5700 GWh 8700 GWh 11000 GWh Pf = delivery pressure

Hydrogen: Working capacity = 12. 6 TWh 100 GWh/day Natural gas: Working capacity = 30. 2 TWh 250 GWh/day

Hy. Under Project – H 2 Storage Comparison http: //hyunder. eu/publications/

The hydrogen future? Air storage CO 2 storage H 2 storage http: //homework. uoregon. edu/ pub/class/350/out 350/hyd. html

H 2 in the Midland Valley of Scotland Hydrogen storage in porous geological formations – onshore play opportunities in the Midland Valley (Scotland, UK) Heinemann et al. , in press, International Journal of Hydrogen Energy True scale!

Image: Wikipedia Public perception

Hy. Stor. Por Project • Approx 1. 4 M GBP, start Oct 2019, 3 years • Uo. E, SAMS, Imp College – Hydrogen reactivity – Petrophysics – Flow simulation – Public perception – Communication and outreach Hydrogen Day Wed 18 March https: //blogs. ed. ac. uk/hystorpor/

Compressed Air Energy Storage Huntorf, nr Bremen, Germany ‘Conventional’ 60 % output = compression 3 times ‘conventional’ output

CAES – porous rock

Pittsfield (Illinois)CAES test-site

WELL CAES model (OGS radial model, air production phase)

‘Saline Aquifers’ – very large 160 % of the UK’s electricity consumption for January and 18 February of 2017 with a round -trip energy efficiency of 54 - 59 %. Source: Inter-seasonal compressed air energy storage using saline aquifers, Mouli-Castillo et al. (2019)

AMID, MIGNARD and WILKINSON (2016) Seasonal storage of hydrogen in a depleted natural gas reservoir International Journal of Hydrogen Energy, 41, 5549 – 5558 Niklas Heinemann, Matt booth, Stuart Haszeldine, Mark Wilkinson, Jonathan Scafidi and Katriona Edlmann Hydrogen storage in porous geological formations - Onshore play opportunities in the Midland Valley (Scotland, UK) International Journal of Hydrogen Energy. 43, 20861 - 20874. Julien Mouli-Castillo, Mark Wilkinson, Dimitri Mignard, Christopher Mc. Dermott, R. Stuart Haszeldine and Zoe K. Shipton Inter-seasonal compressed-air energy storage using saline aquifers Nature Energy, 4, 131– 139. Any questions?

References / reading • • • Ganzer et al. , 2013. The H 2 STORE project - Experimental and numerical simulation approach to investigate processes in underground H 2 reservoir storage. 75 th EAGE Conference & Exhibition, SPE EUROPEC. H 2 STORE (completed 2015): https: //www. gfzpotsdam. de/en/section/cgs/projects/completed-projects/h 2 store/ Henkel, et al. , 2017. Laboratory Experiments for Safe Underground Hydrogen/Energy Storage in Depleted Natural Gas Reservoirs. 4 th Sustainable Earth Sciences Conference (EAGE). Hy. INTEGER Project: Investigations on the integrity of wells and technical components exposed to highly corrosive conditions in geological hydrogen underground reservoirs https: //www. hyinteger. com/english/ Smigan et al. , 1990, Methanogenic bacteria as a key factor involved in changes of town gas stored in an underground reservoir. FEMS Microbiol Lett ; 73(3): 221 -2. Yekta et al. , 2018. Determination of Hydrogen–Water Relative Permeability and Capillary Pressure in Sandstone: Application to Underground Hydrogen Injection in Sedimentary Formations. Transport in Porous Media 122, 1– 24.