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Thermal Energy Storage : Methods and MaterialsThermal Energy Storage : Methods and Materials
Dr. P. MuthukumarAssociate Professor
Department of Mechanical EngineeringIndian Institute of Technology Guwahati
Guwahati 781039 INDIAGuwahati - 781039, INDIAEmail: [email protected] 1
About IITGLocated in the Gateway ofLocated in the Gateway of North – Eastern Part of India
Started 1995, established during 2005.
Beautiful campus among other IITS. Located on the river bank on Brahmaputra. Campus is surrounded by many Hills and Lakes. y
Campus size about 700 acr.
8 Engg and 4 Science Departments
About 6000 students, 300 faculty and 500 supporting
IIT M
faculty and 500 supporting staffs
Over million migratory bi d ild t t
2
birds, wild cats, etc.
Dept. of Mechanical Engineering, Indian Institute of Technology Guwahati
3
Dept. of Mechanical Engineering, Indian Institute of Technology Guwahati
Out line of Presentation
TES concepts and methods
Types TES techniques
Steam accumulatorSteam accumulator
Reversible chemical heat storage (Metal hydride based thermal energy storage)
World wide status of TES systemsWorld wide status of TES systems
Proposed TES system for Solar PAN IIT
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Dept. of Mechanical Engineering, Indian Institute of Technology Guwahati
Thermal Storage Systems
Thermal energy storage (TES) systems correct the mismatch between the supply and demand of energy.
Types : Sensible, Latent and Reversible Chemical Storage
BenefitsBenefits
Increase system reliability: To reduce the peaks of energy generation
Increase generation capacity: The excess generation availableduring low demand periods can be used to charge a TES in order toincrease the effective generation capacity during high demandincrease the effective generation capacity during high-demandperiods. The result is a higher load factor for the plants, helping togenerate energy in a stable way.
Reduction of costs of generation: Seasonal demands can bematched with the help of TES systems that operate synergistically.
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Sensible Heat Storage Materials Essential requirements
o High thermal capacity (ρCp)o High melting point (large operating temperature)o High melting point (large operating temperature)o High thermal conductivityo Stability
L to Low cost
Commonly used sensible storage materials (Solid)Storage medium Operating
temperature, °CHeat capacity, kJ/kg-K
[k]
y g ( )
Reinforced concrete 400 0.85 [1.5]NaCl (solid) 500 0.85 [7]Cast iron 400 0.56 [37]Cast steel 700 0.6 [40]Silica fire bricks 700 1.00 [1.5]Magnesia fire bricks 1200 1.15 [5]
Low costHigh thermal conductivity and volumetric storage capacity
Molten Salts (Sensible liquid Heat Storage Materials)
Best: 60% NaNO3 + 40% KNO3Solar Salt : Freezing point 220°C
Source: Hoshi et al., Solar EnergySolar Energy 79; 332-339, 2005.
A t H t t f fl id f l t t t to Acts as Heat transfer fluid from solar concentrator to steam generator and also heat storage medium
o Heat storage : Active storage
Latent Heat Storage Materials
Requirements# High heat of fusion # High thermal conductivity #Low cost
MgCl2/KCl/NaCl; KOH; KNO3; KNO3/KCl; NaNO3
Suffer from low thermal conductivityKNO3; KNO3/KCl; NaNO3
Yet to be exploredy
Integration of graphite enhance k up to 10 W/mK.
Source: Hoshi et al., Solar Energy 79; 332-339, 2005.
Features: High energy density ; Temperature ranges are flexible, Optimal utilization of the storage materials
Proposed phase change materials (PCM) forcascade heat storage in the temperature range up to380°C are NaNO3, KNO3/ KNO3, KOH and MgCl2 isproposedproposed.
A schematic of the cascade latent heat storage9
A schematic of the cascade latent heat storage
Techniques of Thermal Storage
Active Heat storage : C f fo Characterized by forced convection heat transfer.
o Heat storage medium circulates in the solar fieldo High heat transfer rate, more effectiveo But, high cost; freezing in solar panels
Direct Active storage : Heat transfer fluid itself serves asDirect Active storage : Heat transfer fluid itself serves as storage (Hot and cold tank)
Indirect Active storage : Heat transfer fluid which isIndirect Active storage : Heat transfer fluid which is circulated in the solar panel is different from the one used in storage. i.e. heat transfer fluid transfer heat to secondary fluid which acts as storagefluid, which acts as storage
Passive Heat Storage : Storage medium is fixed. Heat transfer fl id th h t di l d i h i dfluid passes through storage medium only during charging and discharging time. e.g. solid storage and PCM.
Direct active Two –Tanks Thermal Storage Systemo Hot and cold fluids are stored separately
o Freezing of salt (120-220°C)o Auxiliary heater is required
to maintain the temperature
o No additional heat exchangero Fast heat transfer
~450°C
~450°C
60% NaNO3 + 40% KNO3 above freezing during night time and adverse weather conditions
Schematic of Solar Thermal Power Plant with direct active two –tanks thermal storage system (Solar Tres, Sevilla; source: Gil et al. (2010), Renewable and Sustainable Energy Reviews 14; 31-35.)
Active indirect single tank thermal storage system
o Hot and cold fluids are stored in the same tanko Hot and cold fluids are stored in the same tanko Hot and cold fluids are separated because of the stratification effecto Controlled charging and discharging are necessary to maintain the stratificationo Filler material such as quartzite and silica sand used to help thermocline
12Gil et al. (2010), Renewable and Sustainable Energy Reviews 14; 31-35
STEAM ACCUMULATORSSteam accumulators are specially suited to meet the requirements for p y qbuffer storage in solar steam systems, providing saturated steam at pressures up to 100 bar.
Direct steam generation (DSG) inparabolic troughts with integrated steam
DSG with integrated steamaccumulator also used ash t
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parabolic troughts with integrated steamaccumulator (Direct heat storage) phase separator
W.D. Steinmann and M.Eck, Solar Energy 80 (2006) 1277–1282
During the discharge there is a
STEAM ACCUMULATORS
Steam accumulators provide saturated steam. If superheated steam is needed, a
d t t t b
During the discharge there is adrop in the pressure of the steam. To avoid this, the integration ofPCM into the storage vessel tosecond storage system must be
connected to the exit of the steam accumulator
PCM into the storage vessel to replace partly the liquid water
Saturated Steam
St l t ith i t t d14
Steam accumulator with integrated latent heat storage material
Steam accumulator and sensible storage material
W.D. Steinmann and M.Eck, Solar Energy 80 (2006) 1277–1282
Ammonia-based solar thermochemical energy storage system
2NH3 + Heat → N2 +3H2 (Charging mode)N 3H 2NH H (Di h i d )
Operating temperature: 500–860°COperating pressure : 10 25 Mpa
N2 +3H2→ 2NH3 + Heat (Discharging mode)
15H. Kreetz and K. Lovegrove, Solar Energy Vol. 73, No. 3, pp. 187–194, 2002
Operating pressure : 10-25 Mpa
Reversible Chemical Heat Storage: Metal Hydride • Intermetallic compounds formed alloying of different metals by• Intermetallic compounds formed alloying of different metals by
ball milling or melting.Absorption (Exothermic)Absorption (Exothermic)
Desorption (Endothermic)2Intermetallic H Metal Hydride Heat+ → +
15-75 Desorption (Endothermic)2Intermetallic H Metal Hydride Heat+ ← + kJ/mole H2
Ab ti i
Metal Hydride ApplicationsH d St
Absorption Desorption
Hydrogen StorageHydrogen Compressor RefrigeratorH t
H2
Heat pumpThermal Energy StorageHeat transformer Heat Heat
Heat driven mass transfer phenomenon
Metal Hydride Based Heat Storage
o High storage capacity up to 2.2 MJ/kg of hydrideo No thermal insulationo No thermal insulationo Long term storageo Easy regeneration
H t ho High exergy efficiency Heat exchange
MH Reactor
Alloy ΔH
V
V1
Pd
P
y(kJ/mol. H2)
Mg+2% 74 V2Pr
Ps
H Supply
Mg+2% Ni
-74
MgNi -64.88
17
H2 SupplyMg -74.46
Schematic of a Metal Hydride Reactor
18
Test Setup of Heat Storage Device
Effect of supply pressure on the amount of heat stored
430 bar
3
J/kg
)
25 bar
Mg + 30%MmNi4Ta = 150 ˚Cm = 280 g
stor
ed (k
J
20 bar
15 bar2
t of h
eat s
10 bar
1
Am
ount
00 5 10 15 20
20
0 5 10 15 20Time (min)
Effect of supply pressure on thermal energy storage coefficient
0.8
C)
0.7
cien
t (TE
SC
0 5
0.6
T 150 oCage
coef
fic
0.4
0.5 Ta = 150 oCTa = 140 oCTa = 130 oCTa = 120 oCne
rgy
stor
a
0.3
0 Ta 120 C
Mg + 30%MmNi4m = 280 g
Ther
mal
en
0.20 5 10 15 20 25 30 35 40
T
21
0 5 10 15 20 25 30 35 40Supply pressure (bar)
Schematic of a Pre industrialPre-industrial Sacle Metal Hydride ReactorHydride Reactorfor Heat Storage A li iApplication
22
3
3.5
4
350
400
450
wt%
)
C)20 bar
Ps
Effect of supply pressureon hydrogen storagecapacity and average bed2
2.5
3
200
250
300
age
capa
city
(w
empe
ratu
re(°
20 bar
10 bar15 bar
temperature (Ta = 250°C)
0 5
1
1.5
100
150
200
Hyd
ogen
stor
a
vera
ge b
ed te
Mg2NiT = 250°C
10 bar15 bar
0
0.5
0 200 400 600 800 1000 1200 1400 1600
Absorption time (s)
0
50H Av
Hydrogen storage capacityAverage bed temperature
Ta 250 Cma = 0.375 kg
Carried out at IIT Madras, 2004
3
3.5
4
350
400
450
e(°C
)
t%)
10 bar15 barPs=20 bar
Absorption time (s)
2
2.5
3
200
250
300
d te
mpe
ratu
re
ge c
apac
ity (w
t
10 bar15 barPs=20 bar
Effect of supply pressureon hydrogen storagecapacity and average bed
0.5
1
1.5
50
100
150
Ave
rage
bed
Hyd
ogen
stor
ag
Mg2NiTa = 300°Cm 0 375 kg
Hydrogen storage capacityAverage bed temperature
10 bartemperature (Ta = 300°C)
(Muthukumar et al., J. Alloys and C )
00 200 400 600 800 1000 1200 1400 1600 1800
Absorption time(s)
0
50H ma = 0.375 kg Compd., 452, 2008)
Effects of heat release temperature and supply pressure on heat stored (Qr)
1.2
1.4
1.6
oy)
pressure on heat stored (Qr)
0.70.80.9
loy)
0 4
0.6
0.8
1
1.2
r (M
J/kg
of a
llo
2 bar3 bar4 bar
mr = 1.5Th = 650 KTa = 298 K
0 20.30.40.50.6
(MJ/
kg o
f all
2 bar3 bar4 bar
mr = 1.5Th = 650 KTa = 298 K
0
0.2
0.4
510 520 530 540 550 560 570 580 590 600
Heat release temperature (K)
Qr
00.10.2
510 520 530 540 550 560 570 580 590 600
Qr (
Qr vs Tr for Mg2+%Ni at different supply pressures
Heat release temperature (K)
Qr vs Tr for MgNi at different supply pressures
Heat release temperature (K)
0 81
1.21.41.6
g of
allo
y)
2 bar
00.20.40.60.8
Qr (
MJ/
kg 3 bar4 bar
mr = 1.5Th = 650 KTa = 298 K
24Qr Vs Tr for Mg at different supply pressures
0500 520 540 560 580 600
Heat release temperature (K)
Comparison of performances at 3 bar supply pressure
14161820
y/cy
cle)
2
2.5
lloy)
468
101214
oles
/kg
of a
lloy
MgMg + 2% Ni mr = 1.5
T = 650 K 0 5
1
1.5
(MJ/
kg o
f a MgMg2%NiMgNi
mr = 1.5Th = 650 KTa = 298 KPS = 3 bar
024
500 520 540 560 580 600
Heat release temperature (K)
N (m
o
MgNiTh = 650 KTa = 298 KPS = 3 bar 0
0.5
500 520 540 560 580 600
Heat release temperature (K)
Qin
PS 3 bar
No Of hydrogen moles transferred Vs Tr Heat input Vs heat release temperature
Heat release temperature (K)
1 41.6
y)
0.60.8
11.21.4
J/kg
of a
lloy
MgMg+2%Ni
mr = 1.5T 650 K
00.20.4
500 520 540 560 580 600
Qr (
M Mg+2%NiMg2Ni
Th = 650 KTa = 298 KPS = 3 bar
25Heat release vs Heat release temperature
Heat release temperature (K)
Operating temperature ranges of different metal hydrides
Material Usable temperature range (oC )
Mg±Ni/Mg2NiH4 250±350g g2 4
Mg/MgH2+2 wt% Ni 290±420
Mg/MgH2 350±450Mg/MgH2 350±450
Mg/MgH2+10 wt% Fe 350±450
Mg±Fe/Mg FeH 450±550Mg±Fe/Mg2FeH6 450±550
Mg±Co/Mg2CoH5 450±550
26
Storage characterictics of different metal hydrides
Properties Mg/MgH2+2 wt%Ni
Mg/ MgH2
Mg-Fe/ Mg2FeH6
Mg-Co/Mg6CoH1
Mg-Co/Mg2CoH5
metal hydrides
1Enthalpy, kJ/mol 74 74 77.2 89 76Filling Density,
g/cm30.8 0.8 1.22 1.1 1.1
g/cm3
Capacity, wt% 6 5 5 3.5 3.5Energy to weight,
kJ/kg2257 1837 1817 1472 1260
kJ/kgEnergy to volume,
kJ/dm31806 1469 2217 1527 1386
Storage properties of Mg; (25–40) µm,
Temperature (oC) Absorption Desorption S pressure (bar) pressure (bar)
403 19.71 19.68422 27 74 27 54
Source:Bogdanovic et al., J Alloys and Compo nds 282
27
422 27.74 27.54441 39.16 38.85461 54.24 53.76
Compounds ,282; 84-92, 1999.
Country Location Plant Features/Technology
Operational solar thermal power station in the worldy
capacitygy
AppliedUSA Mojave Desert
California354 parabolic trough
Spain Sevilla 150 parabolic troughSpain Sevilla 150 parabolic troughSpain Granada 100 parabolic troughUSA Boulder City, Nevada 64 parabolic troughSpain Puertollano, Ciudad
R l50 parabolic trough
RealSpain Badajoz 50 parabolic troughSpain Torre de Miguel
Sesmero (Badajoz)50 parabolic trough
Spain Alvarado (Badajoz) 50 parabolic troughSpain Sevilla 20 solar power towerIran Yazd 17 parabolic troughSpain Sevilla 11 solar power towerSpain Sevilla 11 solar power towerUSA Bakersfield, California 5 fresnel reflectorUSA Lancaster, California 5 solar power towerItaly near Siracusa, Sicily 5 parabolic troughAustralia New South Wales 2 fresnel reflectorAustralia New South Wales 2 fresnel reflectorUSA Peoria, Arizona 1.5 dish stirlingGermany Jülich 1.5 solar power towerSpain Murcia 1.4 fresnel reflectorUSA R d R k A i 1 b li t h
28
USA Red Rock Arizona 1 parabolic troughUSA Hawaii 2 parabolic troughIran Shiraz 0.25 CSP
940.65
Summary of different thermal storage technologies and materials used in the solar power plant (Trough plant)
Storage concept
Experiences/projects
Year Thermalcapacity(MWhth)
Totalcapacity(MWe)
Operating temperature (°C)
HTF TES media
(MWhth) (MWe) re ( C)
Passive system LS3-SSPS-PSA, Spain
2004 0.48 n.a. n.a. Mineral Oil
High-temperature concretee concrete
Active Indirect system (Two-Tanks)
ANDASOL I-SENER/Cobra, Guadix, Spain
2008 1010 n.a. 384–291 Steam Molten salts (60% NaNO3 + 1010 50 560–260
880 382 296 40% KNO3) 880 n.a. 382–296
Active Indirect system (Two-T k )
ANDASOL II-SENER/Cobra, G di S i
2009 n.a. n.a. n.a. Steam Molten salts
Tanks) Guadix, SpainActive Indirect system (Two-Tanks)
EXTRESOL I-SENER/Cobra
2010 (12 h) 50 n.a. Synthetic Oil
Molten salts
Tanks) n.a. SOLANA,
Phoenix, AR, USA 2011 n.a. 280 n.a. n.a. n.a.
Source: Medrano et al., Renewable and Sustainable Energy Reviews 14; 56-72, 2010.
Summary of different thermal storage technologies and materials used in the solar power plant (Central receiver plant)
Active Indirect system (Two-Tanks)
CESA I-PSA, Spain
1983 7 12 340–220 Steam Molten salts 1982 n.a. 1 n.a. Steam Molten salts
(nitrate) 12 520 Steam (100 bar) Molten saltsTanks) 12 520 Steam (100 bar) Molten salts
Active Indirect system (Two-
CERS-SSPS PSA, Spain
1981 2.7 0.5 n.a. Molten salt (liquid sodium)
Molten salt (sodium)
Tanks) Active Direct system (Two-Tanks)
THEMIS, Targasonne, France
1982 40 2.5 450–250 Molten salt (High technology)
Molten salt (High technology)Tanks) France technology)
Active Direct system (Direct steam generation)
PS10-Abengoa, Sevilla, Spain
2007 15(50 min)
11 n.a. Steam Steam–ceramic
generation) Active Direct system (Direct steam
PS20-Abengoa, Sevilla, Spain
2007 n.a. 20 n.a. Steam Steam–ceramic
generation) Active Direct system (Two-Tanks)
SOLAR TRES-PSA, Spain
2002–2007
588(16 h)
17 565–288 Molten salts (NaNO3 + KNO3)
Molten salts (NaNO3 + KNO )
30
Tanks) Spain(SENER)
KNO3)
Source: Medrano et al., Renewable and Sustainable Energy Reviews 14; 56-72, 2010.
Solar PAN IIT : Research Proposal
Schematic of proposed 1 MW Solar Thermal Power Plant
Objectives of Heat Storage
To ensure continuous generation of stream for 8 hrs with 95% reliability and to extend the possibility of steam generation during night time
Proposed Heat Storage Capacity
Technique Capacity App. Cost (USD)
Steam Accumulator 14 GJ 4,20,000
Sensible Heat Storage 1 GJ 1,20,000
Latent Heat Storage 1 GJ 1,80,000
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Proposed Thermal Energy Storage Systems
o It is proposed to store the excess energy absorbed during theday time in the form of high pressure water up to 80 bar. Theapproximate capacity of high pressure steam storage vessel isapproximate capacity of high pressure steam storage vessel is150 m3 and the estimated amount of heat stored in the form ofhigh pressure water is about 14 GJ.
o Heat generated from the parabolic solar collector is first stored inthe form of sensible heat in the temperature range up to 350-500°C Thi t d l i l d t t500°C. This storage module is also used to generate superheated steam.
o It is also proposed to store 1 GJ heat in the form of latent heatusing phase change materials (PCM) of temperature range up to400°C. Cascade latent heat storage consists of NaNO3, KNO3/g 3, 3KNO3, KOH and MgCl2 is proposed. The use of a cascade ofmultiple phase change materials (PCM) shall ensure the optimalutilization of the storage material
33
utilization of the storage material.
o Application of metal hydrides as heat storage will be also tested.
Thanks for your kind attention
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