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Energy storage, Thermal energy storage (TES)

Ron ZevenhovenÅbo Akademi University

Thermal and Flow Engineering Laboratory / Värme- och strömningstekniktel. 3223 ; [email protected]

Advanced Process Thermodynamicscourse # 424520.0 (5 sp) v. 2017

ÅA 424520

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4.1 Energy storage

Energy storage - motivationsSeveral reasons motivate the storage of energy, either as heat, cold, or electricity:

– Supplies of energy are in many cases intermittent: supply / demand mismatch

– Increased efficiency of energy use must be part of the future’s energy distribution and use methods

– Improved materials based on nanotechnology (for example) allow for more advanced energy-related applications

– Linked to renewable energy phase-in & fossil energyphase-out

• less emissions to the atmosphere and other environmental impactbut (!) not necessarily water-use-efficient.

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Energy storage – options 1/2 To be distinguished: storage of energy as physical

exergy, and storage as chemical exergy (fuels, batteries)

This gives the following main options:1. Storing energy as chemical

exergy electricity in batteries (chemical potential) or using heat or power to produce fuel (e.g. H2, ethanol) or reduced oxides (Si, Zn), including ”solar fuels”


Picture: http://www.intechopen.com/books/application-of-solar-energy/fuel-production-using-concentrated-solar-energy

Energy storage – options 2/2 This gives the following main options:

2. Storing energy as physical exergy:• Potential energy storage (e.g. pumped hydropower)• Compression/expansion of gas (e.g. compressed air storage)• Thermal storage as sensible heat: specific heat × Δ temperature• Thermal storage as latent heat: heat of vaporisation, condensation

Important are, besides (of course) energy storage density(ESD), (J/kg or J/m3):– Reversibility (i.e. repeatability), speed of charge/discharge, and

stability (e.g. battery life, melt/solidify/melt/solidify ....... stability)– Size and weight– Complexity and of course costs (capex, opex)


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ES supply or demand management


Source: SS13

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Mechanical energy storage: hydro


Pictures: DR02

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Mechanical energy storage: air


Pictures: DR02

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Chemical energy: hydrogen, methane


Source: SS13

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Chemical energy: hydrogen storage


Source: SS13

Investment costsgaseous storage

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Chemical energy: ammonia


Source: SS13

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Chemical energy: batteries


Source: SS13

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Secondary batteries: comparison


Source: SS13

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Na-S


Source: SS13

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Li-air batteries


Source: SS13

Aqueous (fast) – but water is consumed:

Non-aqueous (as in Figure):

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ES technologies and costs


Source: SS13

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Thermal energy storage: water


Picture: DR02

~ 2200 kJ/kg

~ 4,2×ΔT kJ/kg

~ 330 kJ/kg

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Nanomaterials for TES


TES applications:- Building heating / cooling

e.g. PCM materials- Electronics- Automotive, IC engine- Solar collectors

Source: DR02

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4.2 Thermal energy storage: heat

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General TES stages & types


Diurnal: hours – a daySeasonal: weeks - months

Source: DR02

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Solar energy driven TES


Rock-bed/ solar TES

Solar storage tanks: (a) Direct link to collector;

(b) Sensible TES with heat exchanger; (c) Thomason’s technique with both

water and stone as storage media

Source: DR02

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Thermal stratification TES


Types and configurations ofstorage tanksHX = heat exchangerHTF = heat transfer fluid

Source: DR02

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Aquifer TES (ATES)

Heat pump + ATES

Source: DR02

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Solar ponds


(see also course part 2b, and ÅA course New Energy Technologies)Source: DR02

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Evacuated solar collector TES


(see also course part 2b, and ÅA course New Energy Technologies)Source: DR02

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Phase change materials (PCMs)


Source: http://www.climatetechwiki.org/technology/jiqweb-pcm-0

TES materials, capacity, temperature


Source: SS13

TCM (or TCS) = thermochemical storage ; PCM = phase change material

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Phase change materials (PCMs)


Source: DR02

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PCMs physical properties 1/2


......continues on next pageSource: DR02

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PCMs physical properties 2/2


Source: DR02

See also: Pielichosewka and Piliechwoski,Progr. Mat. Sci. 65 (2014) 67-123

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MgCO3 (from large-scale CO2

mineralisation) and TES

See also PCT/US97/15577:

2

MgCO3 + xH2O MgCO3.xH2O + heat

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4.3 Thermal energy storage for buildings & integration with heat pumps

(incl. R&D @ ÅA)

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Solar TES with a heat pump


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Water sorption on/with a salt


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TE storage density with sorption


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TE seasonal storage: open / closed


TES: hydrated magnesium carbonates


Source:EZ17a,b

@ ÅA


TES: hydrated magnesium carbonates

Source:EZ17b ”The process” = MgCO3 + xH2O = MgCO3·xH2O + heat

@ ÅA

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4.4 Thermal energy storage: cold

(see also ÅA course 424519.0 Refrigeration / Kylteknik #8)


Cold thermal energy storage (CTES)

Night-time off-peak (cheaper) energycan be stored (batteries) for day-timepeak use for air conditioning

Cooling capacity can be stored as coldor frozen water, or other materials such as glycol and eutectic salt + water systems

Also special phase transitionmaterials (PCMs) were developed

Note also that with loweroutside (night-time) temperatures, cooling and freezing processes are more efficient!

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PCMs: see http://www.teappcm.com/ (Accessed April 2017)

Chilled water vs. ice banks


Source: S?

Dependson ΔT

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Ice bank with plastic-filled balls

↑ An ice CTES system has 18x more capacity per kg than a water CTES system

Example of an ice TES system →atmosperic ice ball (single tank) system

Pictures: DR02

Partial storage vs. full storage


refrigerationdemand

Pictures: S?


Sources A-KLL13: H H Al-Kayiem, S C Lin and A Lukmon. Review on Nanomaterials for

Thermal Energy Storage Technologies. Nanoscience & Nanotechnology - Asia, 2013, 3, 60-71

DR02: Dinçer, I, Rosen, M A, Thermal energy storage, Wiley & Sons (2002) DR10: ibid., 2nd edition (2010), available (for ÅA students) via

ALMA http://ezproxy.abo.fi/login?url=http://site.ebrary.com/lib/abo/Doc?id=10419102

ESA: Energy storage association http://energystorage.org/ EZ17a: Erlund, R., Zevenhoven, R. “Thermal storage of (solar) energy by

sorption of water in magnesium (hydro)carbonates” Int. J. of Thermodynamics – accepted / in press (2017)

EZ17b: Erlund, R., Zevenhoven, R. “Hydration of magnesium carbonate in a thermal energy storage process and its heating application design” ECOS’2017, July 2- 6, 2017, San Diego (CA) USA - paper 182

S??: Refrigeration technology, Siemens Building technologies (year?) section 7 https://www.downloads.siemens.com/download-center/Download.aspx?pos=download&fct=getasset&id1=8359

SS13: Stolten, D., Scherer, V. Transition to Renewable Energy Systems, Wiley-VCH (2013) Part V: Storage = Chapters 27-33

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