Phase-change material

A sodium acetate heating pad. When the sodium acetate solution crystallises, it becomes warm.

A video showing a „heating pad“ in action

A phase-change material (PCM) is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa; thus, PCMs are classified as latent heat storage (LHS) units.

Characteristics and classification

Latent heat storage can be achieved through liquid–>solid, solid–>liquid, solid–>gas and liquid–>gas phase changes. However, only solid–>liquid and liquid–>solid phase changes are practical for PCMs. Although liquid–gas transitions have a higher heat of transformation than solid–liquid transitions, liquid->gas phase changes are impractical for thermal storage because large volumes or high pressures are required to store the materials in their gas phase. Solid–solid phase changes are typically very slow and have a relatively low heat of transformation.

Initially, solid–liquid PCMs behave like sensible heat storage (SHS) materials; their temperature rises as they absorb heat. Unlike conventional SHS materials, however, when PCMs reach the temperature at which they change phase (their melting temperature) they absorb large amounts of heat at an almost constant temperature. The PCM continues to absorb heat without a significant rise in temperature until all the material is transformed to the liquid phase. When the ambient temperature around a liquid material falls, the PCM solidifies, releasing its stored latent heat. A large number of PCMs are available in any required temperature range from −5 up to 190 °C.^[1] Within the human comfort range between 20–30 °C, some PCMs are very effective. They store 5 to 14 times more heat per unit volume than conventional storage materials such as water, masonry or rock.^[2]

Organic PCMs

Paraffin (C_nH_2n+2), carbohydrate and lipid derived. ^[3][4][5]

• Advantages
  • Freeze without much undercooling
  • Ability to melt congruently
  • Self nucleating properties
  • Compatibility with conventional material of construction
  • No segregation
  • Chemically stable
  • High heat of fusion
  • Safe and non-reactive
  • Recyclable
  • Carbohydrate and lipid based PCMs can be produced from renewable sources
• Disadvantages
  • Low thermal conductivity in their solid state. High heat transfer rates are required during the freezing cycle
  • Volumetric latent heat storage capacity can be low
  • Flammable. This can be partially alleviated by specialist containment
  • To obtain reliable phase change points, most manufacturers use technical grade paraffins which are essentially paraffin mixture(s) and are completely refined of oil, resulting in high costs

Inorganic

Salt hydrates (M_nH₂O)^[6]

• Advantages
  • High volumetric latent heat storage capacity
  • Availability and low cost
  • Sharp melting point
  • High thermal conductivity
  • High heat of fusion
  • Non-flammable
• Disadvantages
  • Change of volume is very high
  • Super cooling is major problem in solid–liquid transition
  • Nucleating agents are needed and they often become inoperative after repeated cycling

Eutectics

c-inorganic, inorganic-inorganic compounds

• Advantages
  • Eutectics have sharp melting point similar to pure substance
  • Volumetric storage density is slightly above organic compounds
  • Extra water principle can be used to avoid phase change dedragation, involveing dissolving the anhydrous salt during melting to result in a thickening of the liquid material so that it melts to a gel form
• Disadvantages
  • Only limited data is available on thermo-physical properties as the use of these materials are relatively new to thermal storage application

Hygroscopic materials

Many natural building materials are hygroscopic, that is they can absorb (water condenses) and release water (water evaporates). The process is thus:

• Condensation (gas to liquid) ΔH<0; enthalpy decreases (exothermic process) gives off heat.
• Vaporization (liquid to gas) ΔH>0; enthalpy increases (endothermic process) absorbs heat (or cools).

Whilst this process liberates a small quantity of energy, large surfaces area allows significant (1–2 °C) heating or cooling in buildings. The corresponding materials are wool insulation, earth/clay render finishes,.

Selection criteria

Thermodynamic properties. The phase change material should possess:^[7]

• Melting temperature in the desired operating temperature range
• High latent heat of fusion per unit volume
• High specific heat, high density and high thermal conductivity
• Small volume changes on phase transformation and small vapor pressure at operating temperatures to reduce the containment problem
• Congruent melting
• Kinetic properties
• High nucleation rate to avoid supercooling of the liquid phase
• High rate of crystal growth, so that the system can meet demands of heat recovery from the storage system
• Chemical properties
• Chemical stability
• Complete reversible freeze/melt cycle
• No degradation after a large number of freeze/melt cycle
• Non-corrosiveness, non-toxic, non-flammable and non-explosive materials
• Economic properties
• Low cost
• Availability

Thermophysical properties

Common PCMs

Material	Organic PCM	Melting point ^oC	Heat of fusion kJ·kg^−1	Heat of fusion MJ·m^−3	Specific heat, cp solid kJ·kg^−1·K^−1	Specific heat, cp liquid kJ·kg^−1·K^−1	Density, ρ solid kg·m^−3	Density, ρ liquid kg·m^−3	Thermal conductivity, k solid W·m^−1·K^−1	VHC solid kJ·m^−3·K^−1	VHC liquid kJ·m^−3·K^−1	Thermal effusivity, e solid J·m^−2·K^−1·s^−1/2	Cost USD·kg^−1
Water	No	0	333.6	319.8	2.05	4.186	917	1,000	1.6[8]-2.22[9]	1,880	4,186	1,890	0.003125[10]
Sodium sulfate (Na2SO4·10H2O)	No	32.4	252										0.05 [11]
NaCl·Na2SO4·10H2O	No	18	286										0.05 [11]
Lauric acid	Yes[12][13]	44.2[14]	211.6	197.7	1.76	2.27	1,007	862		1,772	1,957		1.6 [15][16]
TME(63%w/w)+H2O(37%w/w)	Yes[12][13]	29.8	218.0	240.9	2.75	3.58	1,120	1,090		3,080	3,902
Mn(NO3)2·6H2O+MnCl2·4H2O(4%w/w)	No[17][18]	15–25	125.9	221.8	2.34	2.78	1,795	1,728		4,200	4,804
Na2SiO3·5H2O	No[17][18]	72.20	267.0	364.5	3.83	4.57	1,450	1,280	0.103−0.128[19]	5,554	5,850	801	8.04[20]
Aluminium	No	660.32	396.9	1,007.2	0.8969		2,700	2,375	237[21][22]	2,422	?	23,960	2.04626[23]
Copper	No	1,084.62	208.7	1,769.5	0.3846		8,940	8,020	401[24]	3,438	?	37,130	6.81256[25]
Gold	No	1,064.18	63.72	1,166.3	0.129		19,300	17,310	318[26]	2,491		28,140	34,297.8[25]
Iron	No	1,538	247.3	1,836.6	0.4495		7,874	6,980	80.4[27]	3,539		16,870	0.3248[28]
Lead	No	327.46	23.02	253.2	0.1286		11,340	10,660	35.3[29]	1,459		7,180	2.1151[25]
Lithium	No	180.54	432.2	226.0	3.5816		534	512	84.8[30]	1,913		12,740	62.2164[31]
Silver	No	961.78	104.6	1,035.8	0.235		10,490	9,320	429[32]	2,465		32,520	492.524[25]
Titanium	No	1,668	295.6	1,273.5	0.5235		4,506	4,110	21.9[33]	2,359		7,190	8.0469[34]
Zinc	No	419.53	112.0	767.5	0.3896		7,140	6,570	116[35]	2,782		17,960	2.15735[25]
${\displaystyle {\ce {NaNO3}}}$	No	310	174										[36]
${\displaystyle {\ce {NaNO2}}}$	No	282	212										[36]
NaOH	No	318	158										[36]
${\displaystyle {\ce {KNO3}}}$	No	337	116										[36]
KOH	No	360	167										[36]
NaOH/${\displaystyle {\ce {Na2CO3}}}$ (7.2%)	No	283	340										[36]
NaCl(26.8%)/NaOH	No	370	370										[36]
NaCl/KCL(32.4%)/LiCl(32.8%)	No	346	281										[36]
NaCl(5.7%) / ${\displaystyle {\ce {NaNO3}}}$ (85.5%) / ${\displaystyle {\ce {Na2SO4}}}$	No	287	176										[36]
NaCl / ${\displaystyle {\ce {NaNO3}}}$ (5.0%)	No	284	171										[36]
NaCl(5.0%)/ ${\displaystyle {\ce {NaNO3}}}$	No	282	212										[36]
NaCl(42.5%)/KCl(20.5)/${\displaystyle {\ce {MgCl2}}}$	No	385-393	410										[36]
${\displaystyle {\ce {KNO3(10\%)/NaNO3}}}$	No	290	170										[36]
${\displaystyle {\ce {KNO3}}}$/KCl(4.5%)	No	320	150										[36]
${\displaystyle {\ce {KNO3}}}$/KBr(4.7%)/KCl(7.3%)	No	342	140										[36]
Paraffin 14-Carbons [37]	Yes	5.5	228
Paraffin 15-Carbons [37]	Yes	10	205
Paraffin 16-Carbons [37]	Yes	16.7	237.1
Paraffin 17-Carbons [37]	Yes	21.7	213
Paraffin 18-Carbons [37]	Yes	28	244
Paraffin 19-Carbons [37]	Yes	32	222
Paraffin 20-Carbons [37]	Yes	36.7	246
Paraffin 21-Carbons [37]	Yes	40.2	200
Paraffin 22-Carbons [37]	Yes	44	249
Paraffin 23-Carbons [37]	Yes	47.5	232
Paraffin 24-Carbons [37]	Yes	50.6	255
Paraffin 25-Carbons [37]	Yes	49.4	238
Paraffin 26-Carbons [37]	Yes	56.3	256
Paraffin 27-Carbons [37]	Yes	58.8	236
Paraffin 28-Carbons [37]	Yes	61.6	253
Paraffin 29-Carbons [37]	Yes	63.4	240
Paraffin 30-Carbons [37]	Yes	65.4	251
Paraffin 31-Carbons [37]	Yes	68	242
Paraffin 32-Carbons [37]	Yes	69.5	170
Paraffin 33-Carbons [37]	Yes	73.9	268
Paraffin 34-Carbons [37]	Yes	75.9	269
Formic acid [37]	Yes	7.8	247
Caprilic acid [37]	Yes	16.3	149
Glycerin [37]	Yes	17.9	198.7
p-Lattic acid [37]	Yes	26	184
Methyl palmitate [37]	Yes	29	205
Camphenilone [37]	Yes	39	205
Docasyl bromide [37]	Yes	40	201
Caprylone [37]	Yes	40	259
Phenol [37]	Yes	41	120
Heptadecanone [37]	Yes	41	201
1-Cyclohexylooctadecane [37]	Yes	41	218
4-Heptadacanone [37]	Yes	41	197
p-Joluidine [37]	Yes	43.3	167
Cyanamide [37]	Yes	44	209
Methyl eicosanate [37]	Yes	45	230
3-Heptadecanone [37]	Yes	48	218
2-Heptadecanone [37]	Yes	48	218
Hydrocinnamic acid [37]	Yes	48	118
Cetyl acid [37]	Yes	49.3	141
α-Nepthylamine [37]	Yes	59	93
Camphene [37]	Yes	50	238
O-Nitroaniline [37]	Yes	50	93
9-Heptadecanone [37]	Yes	51	213
Thymol [37]	Yes	51.5	115
Methyl behenate [37]	Yes	52	234
Diphenyl amine [37]	Yes	52.9	107
p-Dichlorobenzene [37]	Yes	53.1	121
Oxolate [37]	Yes	54.3	178
Hypophosphoric acid [37]	Yes	55	213
O-Xylene dichloride [37]	Yes	55	121
β-Chloroacetic acid [37]	Yes	56	147
Chloroacetic acid [37]	Yes	56	130
Nitro napthalene [37]	Yes	56.7	103
Trimyristin [37]	Yes	33	201
Heptaudecanoic acid [37]	Yes	60.6	189
α-Chloroacetic acid [37]	Yes	61.2	130
Bees wax [37]	Yes	61.8	177
Glyolic acid [37]	Yes	63	109
Glycolic acid [37]	Yes	63	109
p-Bromophenol [37]	Yes	63.5	86
Azobenzene [37]	Yes	67.1	121
Acrylic acid [37]	Yes	68	115
Dinto toluent (2,4) [37]	Yes	70	111
Phenylacetic acid [37]	Yes	76.7	102
Thiosinamine [37]	Yes	77	140
Bromcamphor [37]	Yes	77	174
Durene [37]	Yes	79.3	156
Methly brombenzoate [37]	Yes	81	126
Alpha napthol [37]	Yes	96	163
Glautaric acid [37]	Yes	97.5	156
p-Xylene dichloride [37]	Yes	100	138.7
Catechol [37]	Yes	104.3	207
Quinone [37]	Yes	115	171
Actanilide [37]	Yes	118.9	222
Succinic anhydride [37]	Yes	119	204
Benzoic acid [37]	Yes	121.7	142.8
Stibene [37]	Yes	124	167
Benzamide [37]	Yes	127.2	169.4
Acetic acid [37]	Yes	16.7	184
Polyethylene glycol 600 [37]	Yes	20	146
Capric acid [37]	Yes	36	152
Eladic acid [37]	Yes	47	218
Pentadecanoic acid [37]	Yes	52.5	178
Tristearin [37]	Yes	56	191
Myristic acid [37]	Yes	58	199
Palmatic acid [37]	Yes	55	163
Stearic acid [37]	Yes	69.4	199
Acetamide [37]	Yes	81	241
Methyl fumarate [37]	Yes	102	242

Volumetric heat capacity (VHC) J·m⁻³·K⁻¹

${\displaystyle \mathrm {VHC} =\rho c_{p}}$

Thermal inertia (I) = Thermal effusivity (e) J·m⁻²·K⁻¹·s^−1/2

${\displaystyle I={\sqrt {k\rho c_{p}}}=e={(k\rho c_{p})}^{\frac {1}{2}}}$

Commercially available PCMs near room temperature

Material	Supplier	Type	Form	Melting temperature, Tm ^oC	Melting temperature, Tm ^oF	Latent heat of fusion, L kJ/kg	Density, ρ kg/m^3	Liquid Thermal conductivity, k W/m·K	Solid Thermal conductivity, k W/m·K	Specific heat, cp kJ/kg·K
18 C⁰ Infinite R Energy Sheet	Insolcorp[38]	Inorganic	Macro-encapsulated	18	64.4	200	1540	0.54	1.09	3.14
21 C⁰ Infinite R Energy Sheet	Insolcorp[38]	Inorganic	Macro-encapsulated	21	69.8	200	1540	0.54	1.09	3.14
23 C⁰ Infinite R Energy Sheet	Insolcorp[38]	Inorganic	Macro-encapsulated	23	73.4	200	1540	0.54	1.09	3.14
25 C⁰ Infinite R Energy Sheet	Insolcorp[38]	Inorganic	Macro-encapsulated	25	77	200	1540	0.54	1.09	3.14
29 C⁰ Infinite R Energy Sheet	Insolcorp[38]	Inorganic	Macro-encapsulated	29	84.2	200	1540	0.54	1.09	3.14
savE [39] HS 33N[40]	Pluss[41]	Inorganic	Bulk	-30	-22	224	1425
savE HS 26N[42]	Pluss	Inorganic	Bulk	-24	-11.2	222	1200			3.6
savE HS 23N[43]	Pluss	Inorganic	Bulk	-20	-4	210	1140	0.7	4.9	3.4
savE HS 18N[44]	Pluss	Inorganic	Bulk	-18	-0.4	242	1095	0.44
savE HS 15N[45]	Pluss	Inorganic	Bulk	-15	5	280	1070	0.53	5.26	3.4
savE HS 10N[46]	Pluss	Inorganic	Bulk	-10	14	230	1125	0.60	4.25	0.96
savE HS 7N[47]	Pluss	Inorganic	Bulk	-6	21.2	230	1120	0.55	1.76	3.2
savE Frost/HS 01[48]	Pluss	Inorganic	Bulk	1	33.8	290	1010	0.55	2.2	3.9
savE OM 03[49]	Pluss	Organic	Bulk	3.5	38.3	240	835	0.146	0.22	3
savE FS 03[50]	Pluss	Organic	Bulk	3.6	38.48	214			0.16
savE OM 05[51]	Pluss	Organic	Bulk	5.5	41.9	130	845	0.135	0.3	2.37
savE FS 05[52]	Pluss	Organic	Bulk	5.9	42.62	110			0.134
savE OM 08[53]	Pluss	Organic	Bulk	9	48.2	220	1050	0.168	0.235	3.1
savE OM 11[54]	Pluss	Organic	Bulk	9.5	49.1	240	1060	0.118	0.235
savE OM 21[55]	Pluss	Organic	Bulk	21	69.8	250	924	0.14	0.21	2.6
savE FS 21[56]	Pluss	Organic	Bulk	21	69.8	130			0.3
savE HS 21[57]	Pluss	Inorganic	Bulk	22	71.6	185	1400	0.59	0.82	3.4
savE HS 22[58]	Pluss	Inorganic	Bulk	23	73.4	185	1540	0.56	1.13	3.04
savE HS 24[59]	Pluss	Inorganic	Bulk	25	77	185	1510	0.55	1.05	2.3
savE HS 29[60]	Pluss	Inorganic	Bulk	29	84.2	190	1530	0.382	0.478	2.3
savE OM 29[61]	Pluss	Organic	Bulk	29	84.2	229	870	0.172	0.293	3.9
savE FS 29[62]	Pluss	Organic	Bulk	29	84.2	189			0.45
savE OM 30[63]	Pluss	Organic	Bulk	31	87.8	200	878	0.123	0.185	2.6
savE FS 30[64]	Pluss	Organic	Bulk	31	87.8	170			0.496
savE OM 32[65]	Pluss	Organic	Bulk	32	89.6	200	870	0.145	0.219
savE HS 34[66]	Pluss	Inorganic	Bulk	35	95	150	1850	0.47	0.5	2.4
savE OM 35[67]	Pluss	Organic	Bulk	37	98.6	197	870	0.16	0.2
savE OM 37[68]	Pluss	Organic	Bulk	37	98.6	210	860	0.13	0.16
savE OM 46[69]	Pluss	Organic	Bulk	46	114.8	250	880	0.1	0.2
savE OM 48[70]	Pluss	Organic	Bulk	48	118.4	275	875	0.12	0.2
savE OM 50[71]	Pluss	Organic	Bulk	50.3	122.54	250	850	0.14	0.21	3.05
savE OM 55[72]	Pluss	Organic	Bulk	55	131	210	840	0.1	0.16	3.05
savE OM 65[73]	Pluss	Organic	Bulk	67	152.6	183	924	0.33	0.19	2.38
savE FSM 65[74]	Pluss	Organic	Bulk	67	152.6	150	845		0.25
savE HS 89[75]	Pluss	Inorganic	Bulk	87	188.6	180	1630
PureTemp -37	PureTemp [76]	Organic	Bulk	-37	-35	147	880			1.39
PureTemp -23	PureTemp	Organic	Bulk	-23	-9	145	860			2.11
PureTemp -21	PureTemp	Organic	Bulk	-21	-6	240	1060			1.83
PureTemp -17	PureTemp	Organic	Bulk	-17	1	145	860			1.74
PureTemp -15	PureTemp	Organic	Bulk	-15	5	286	1030			1.84
PureTemp -12	PureTemp	Organic	Bulk	-12	10	168	870			1.86
PureTemp -5	PureTemp	Organic	Bulk	-5	23	150	860			1.66
PureTemp 1	PureTemp	Organic	Bulk	1	34	300	1000			2.32
PureTemp 4	PureTemp	Organic	Bulk	4	39	195	880			2.44
PureTemp 6	PureTemp	Organic	Bulk	6	43	170	860			1.56
PureTemp 8	PureTemp	Organic	Bulk	8	46	180	860			1.85
PureTemp 12	PureTemp	Organic	Bulk	12	54	185	860			1.76
PureTemp 15	PureTemp	Organic	Bulk	15	59	165	860			2.25
PureTemp 18	PureTemp	Organic	Bulk	18	64	189	860			1.47
PureTemp 20	PureTemp	Organic	Bulk	20	68	180	860			2.59
PureTemp 23	PureTemp	Organic	Bulk	23	73	203	830			1.84
PureTemp 24	PureTemp	Organic	Bulk	24	75	185	860			2.85
PureTemp 25	PureTemp	Organic	Bulk	25	77	185	860			1.99
PureTemp 27	PureTemp	Organic	Bulk	27	81	200	860			2.46
PureTemp 28	PureTemp	Organic	Bulk	29	84	205	860			2.34
PureTemp 29	PureTemp	Organic	Bulk	29	84	189	850			1.77
PureTemp 33	PureTemp	Organic	Bulk	33	91	185	850			2.34
PureTemp 35	PureTemp	Organic	Bulk	35	95	180	850			2.44
PureTemp 37	PureTemp	Organic	Bulk	38	100	222	840			2.21
PureTemp 48	PureTemp	Organic	Bulk	52	126	245	820			2.1
PureTemp 53	PureTemp	Organic	Bulk	53	127	225	990			2.36
PureTemp 58	PureTemp	Organic	Bulk	58	136	237	810			2.47
PureTemp 60	PureTemp	Organic	Bulk	61	142	230	870			2.04
PureTemp 63	PureTemp	Organic	Bulk	63	145	199	840			1.99
PureTemp 68	PureTemp	Organic	Bulk	68	154	198	870			1.85
PureTemp 103	PureTemp	Organic	Bulk	103	217	157	1220			2.09
PureTemp 151	PureTemp	Organic	Bulk	151	304	170	1360			2.06
Astorstat HA 17	Honey well [77]	Organic	Bulk	21.7	71
Astorstat HA 18	Honey well	Organic	Bulk	27.2	81
RT26	Rubitherm GmbH [78]	Organic	Bulk	24	75	232
RT27	Rubitherm GmbH	Organic	Bulk	28	82	206
Climsel C -21	Climator [79]	Inorganic	Bulk	-21	-6	288	1300		0.6	3.6
Climsel C -18	Climator	Inorganic	Bulk	-18	0	288	1300		0.6	3.6
Climsel C 7	Climator	Inorganic	Bulk	7	45	126	1400		0.6	3.6
Climsel C 10	Climator	Inorganic	Bulk	10.5	51	126	1400		0.6	3.6
Climsel C 21	Climator	Inorganic	Bulk	21	70	112	1380		0.6	3.6
Climsel C24	Climator	Inorganic	Bulk	24	75	151.3	1380		0.6	3.6
Climsel C28	Climator	Inorganic	Bulk	28	82	162.3	1420		0.6	3.6
Climsel C32	Climator	Inorganic	Bulk	32	90	162.3	1420		0.6	3.6
Climsel C48	Climator	Inorganic	Bulk	48	118	180	1360		0.6	3.6
Climsel C58	Climator	Inorganic	Bulk	58	136	288.5	1460		0.6	1.89
Climsel C70	Climator	Inorganic	Bulk	70	158	282.9	1400		0.6	3.6
STL27	Mitsubishi Chemicals [80]	Inorganic	Bulk	27	81	213
S27	Cristopia [81]	Inorganic	Bulk	27	81	207
TH 29	TEAP [82]	Inorganic	Bulk	29	84	188
RT 20	Rubitherm GmbH	Organic	Bulk	22	72	172
Climsel C23	Climator	Inorganic	Bulk	23	73	148			32
RT 26	Rubitherm GmbH	Organic	Bulk	25	77	131
STL 27	Mitsubishi Chemicals	Inorganic	Bulk	27	81	213
RT 30	Rubitherm GmbH	Organic	Bulk	28	82	206
RT 32	Rubitherm GmbH	Organic	Bulk	21	70	130
DS 5000	Micronal [83]		Micro-encapsulated	26	79	45
DS 5007	Micronal		Micro-encapsulated	23	73	41
DS 5030	Micronal		Micro-encapsulated	21	70	37
DS 5001	Micronal		Micro-encapsulated	26	79	110
DS 5008	Micronal		Micro-encapsulated	23	73	100
DS 5029	Micronal		Micro-encapsulated	21	70	90
RT -9 HC	Rubitherm GmbH	Organic	Bulk	-9	16	260
RT -4	Rubitherm GmbH	Organic	Bulk	-4	25	179
RT 0	Rubitherm GmbH	Organic	Bulk	0	32	225
RT 2 HC	Rubitherm GmbH	Organic	Bulk	2	36	205
RT 3	Rubitherm GmbH	Organic	Bulk	3	37	198
RT 3 HC	Rubitherm GmbH	Organic	Bulk	3	37	250
RT 4	Rubitherm GmbH	Organic	Bulk	4	39	182
RT 5	Rubitherm GmbH	Organic	Bulk	5	41	180
RT 5 HC	Rubitherm GmbH	Organic	Bulk	5	41	240
RT 6	Rubitherm GmbH	Organic	Bulk	6	43	175
RT 8	Rubitherm GmbH	Organic	Bulk	8	46	180
RT 9	Rubitherm GmbH	Organic	Bulk	9	48	160
RT 10	Rubitherm GmbH	Organic	Bulk	10	50	150
RT 10 HC	Rubitherm GmbH	Organic	Bulk	10	50	195
RT 11 HC	Rubitherm GmbH	Organic	Bulk	11	52	190
RT 12	Rubitherm GmbH	Organic	Bulk	12	54	150
RT 15	Rubitherm GmbH	Organic	Bulk	15	59	140
RT 18 HC	Rubitherm GmbH	Organic	Bulk	18	64	250
RT 21	Rubitherm GmbH	Organic	Bulk	21	70	160
RT 21 HC	Rubitherm GmbH	Organic	Bulk	21	70	190
RT 22 HC	Rubitherm GmbH	Organic	Bulk	22	72	200
RT 24	Rubitherm GmbH	Organic	Bulk	24	75	150
RT 25	Rubitherm GmbH	Organic	Bulk	25	77	148
RT 25 HC	Rubitherm GmbH	Organic	Bulk	25	77	230
RT 27	Rubitherm GmbH	Organic	Bulk	27	81	179
RT 28 HC	Rubitherm GmbH	Organic	Bulk	28	82	245
RT 31	Rubitherm GmbH	Organic	Bulk	31	88	170
RT 35	Rubitherm GmbH	Organic	Bulk	35	95	170
RT 35 HC	Rubitherm GmbH	Organic	Bulk	35	95	240
RT 42	Rubitherm GmbH	Organic	Bulk	42	108	174
RT 44 HC	Rubitherm GmbH	Organic	Bulk	44	111	255
RT 47	Rubitherm GmbH	Organic	Bulk	47	117	170
RT 50	Rubitherm GmbH	Organic	Bulk	50	122	168
RT 52	Rubitherm GmbH	Organic	Bulk	52	126	173
RT 55	Rubitherm GmbH	Organic	Bulk	55	131	172
RT 58	Rubitherm GmbH	Organic	Bulk	58	136	160
RT 60	Rubitherm GmbH	Organic	Bulk	60	140	144
RT 62	Rubitherm GmbH	Organic	Bulk	62	144	146
RT 65	Rubitherm GmbH	Organic	Bulk	65	149	152
RT 70 HC	Rubitherm GmbH	Organic	Bulk	70	158	230
RT 80 HC	Rubitherm GmbH	Organic	Bulk	79	174	240
RT 82	Rubitherm GmbH	Organic	Bulk	82	180	176
RT 90 HC	Rubitherm GmbH	Organic	Bulk	90	194	200
S117	PlusICE [84]	Inorganic	Bulk	117	243	160	1450		0.7	2.61
S89	PlusICE	Inorganic	Bulk	89	192	151	1550		0.67	2.48
S83	PlusICE	Inorganic	Bulk	83	181	141	1600		0.62	2.31
S72	PlusICE	Inorganic	Bulk	72	162	127	1666		0.58	2.13
S70	PlusICE	Inorganic	Bulk	70	158	110	1680		0.57	2.1
S58	PlusICE	Inorganic	Bulk	58	136	145	1505		0.69	2.55
S50	PlusICE	Inorganic	Bulk	50	122	100	1601		0.43	1.59
S46	PlusICE	Inorganic	Bulk	46	115	210	1587		0.45	2.41
S44	PlusICE	Inorganic	Bulk	44	111	100	1584		0.43	1.61
S34	PlusICE	Inorganic	Bulk	34	93	115	2100		0.52	2.1
S32	PlusICE	Inorganic	Bulk	32	90	200	1460		0.51	1.91
S30	PlusICE	Inorganic	Bulk	30	86	190	1304		0.48	1.9
S27	PlusICE	Inorganic	Bulk	27	81	183	1530		0.54	2.2
S25	PlusICE	Inorganic	Bulk	25	77	180	1530		0.54	2.2
S23	PlusICE	Inorganic	Bulk	23	73	175	1530		0.54	2.2
S21	PlusICE	Inorganic	Bulk	22	72	170	1530		0.54	2.2
S19	PlusICE	Inorganic	Bulk	19	66	160	1520		0.43	1.9
S17	PlusICE	Inorganic	Bulk	17	63	160	1525		0.43	1.9
S15	PlusICE	Inorganic	Bulk	15	59	160	1510		0.43	1.9
S13	PlusICE	Inorganic	Bulk	13	55	160	1515		0.43	1.9
S10	PlusICE	Inorganic	Bulk	10	50	155	1470		0.43	1.9
S8	PlusICE	Inorganic	Bulk	8	46	150	1475		0.44	1.9
S7	PlusICE	Inorganic	Bulk	7	45	150	1700		0.4	1.85
A164	PlusICE	Organic	Bulk	164	327	290	1500			2.42
A155	PlusICE	Organic	Bulk	155	311	100	900		0.23	2.2
A144	PlusICE	Organic	Bulk	144	291	115	880		0.23	2.2
A133	PlusICE	Organic	Bulk	133	271	126	880		0.23	2.2
A118	PlusICE	Organic	Bulk	118	244	340	1450			2.7
A95	PlusICE	Organic	Bulk	95	203	205	900		0.22	2.2
A82	PlusICE	Organic	Bulk	82	180	155	850		0.22	2.21
A70	PlusICE	Organic	Bulk	70	158	173	890		0.23	2.2
A62	PlusICE	Organic	Bulk	62	144	145	910		0.22	2.2
A60H	PlusICE	Organic	Bulk	60	140	212	800		0.18	2.15
A60H	PlusICE	Organic	Bulk	60	140	145	910		0.22	2.22
A58H	PlusICE	Organic	Bulk	58	136	243	820		0.18	2.85
A58	PlusICE	Organic	Bulk	58	136	132	910		0.22	2.22
A55	PlusICE	Organic	Bulk	55	131	135	905		0.22	2.22
A53H	PlusICE	Organic	Bulk	53	127	166	810		0.18	2.02
A53H	PlusICE	Organic	Bulk	53	127	130	910		0.22	2.22
A52	PlusICE	Organic	Bulk	52	126	222	810		0.18	2.15
A50	PlusICE	Organic	Bulk	50	122	218	810		0.18	2.15
A48	PlusICE	Organic	Bulk	48	118	234	810		0.18	2.85
A46	PlusICE	Organic	Bulk	46	115	155	910		0.22	2.22
A44	PlusICE	Organic	Bulk	44	111	242	805		0.18	2.15
A43	PlusICE	Organic	Bulk	43	109	165	780		0.18	2.37
A42	PlusICE	Organic	Bulk	42	108	105	905		0.21	2.22
A40	PlusICE	Organic	Bulk	40	104	230	810		0.18	2.43
A39	PlusICE	Organic	Bulk	39	102	105	900		0.22	2.22
A37	PlusICE	Organic	Bulk	37	99	235	810		0.18	2.85
A36	PlusICE	Organic	Bulk	36	97	217	790		0.18	2.37
A32	PlusICE	Organic	Bulk	32	90	130	845		0.21	2.2
A29	PlusICE	Organic	Bulk	29	84	225	810		0.18	2.15
A28	PlusICE	Organic	Bulk	28	82	155	789		0.21	2.22
A26	PlusICE	Organic	Bulk	26	79	150	790		0.21	2.22
A25H	PlusICE	Organic	Bulk	25	77	226	810		0.18	2.15
A25	PlusICE	Organic	Bulk	25	77	150	785		0.18	2.26
A24	PlusICE	Organic	Bulk	24	75	145	790		0.18	2.22
A23	PlusICE	Organic	Bulk	23	73	145	785		0.18	2.22
A22H	PlusICE	Organic	Bulk	22	72	216	820		0.18	2.85
A22	PlusICE	Organic	Bulk	22	72	145	785		0.18	2.22
A17	PlusICE	Organic	Bulk	17	63	150	785		0.18	2.22
A16	PlusICE	Organic	Bulk	16	61	213	760		0.18	2.37
A15	PlusICE	Organic	Bulk	15	59	130	790		0.18	2.26
A9	PlusICE	Organic	Bulk	9	48	140	775		0.21	2.16
A8	PlusICE	Organic	Bulk	8	46	150	773		0.21	2.16
A6	PlusICE	Organic	Bulk	6	43	150	770		0.21	2.17
A4	PlusICE	Organic	Bulk	4	39	200	766		0.21	2.18
A3	PlusICE	Organic	Bulk	3	37	200	765		0.21	2.2
A2	PlusICE	Organic	Bulk	2	36	200	765		0.21	2.2
E0	PlusICE	Eutectic	Bulk	0	32	332	1000		0.58	4.19
E-2	PlusICE	Eutectic	Bulk	-2	28	306	1070		0.58	3.8
E-3	PlusICE	Eutectic	Bulk	-3.7	25	312	1060		0.6	3.84
E-6	PlusICE	Eutectic	Bulk	-6	21	275	1110		0.56	3.83
E-10	PlusICE	Eutectic	Bulk	-10	14	286	1140		0.56	3.33
E-11	PlusICE	Eutectic	Bulk	-11.6	11	301	1090		0.57	3.55
E-12	PlusICE	Eutectic	Bulk	-12.3	10	250	1110		0.56	3.47
E-14	PlusICE	Eutectic	Bulk	-14.8	5	243	1220		0.53	3.51
E-15	PlusICE	Eutectic	Bulk	-15	5	303	1060		0.53	3.87
E-19	PlusICE	Eutectic	Bulk	-18.7	-2	282	1125		0.58	3.29
E-21	PlusICE	Eutectic	Bulk	-20.6	-5	263	1240		0.51	3.13
E-22	PlusICE	Eutectic	Bulk	-22	-8	234	1180		0.57	3.34
E-26	PlusICE	Eutectic	Bulk	-26	-15	260	1250		0.58	3.67
E-29	PlusICE	Eutectic	Bulk	-29	-20	222	1420		0.64	3.69
E-32	PlusICE	Eutectic	Bulk	-32	-26	243	1290		0.56	2.95
E-34	PlusICE	Eutectic	Bulk	-33.6	-28	240	1205		0.54	3.05
E-37	PlusICE	Eutectic	Bulk	-36.5	-34	213	1500		0.54	3.15
E-50	PlusICE	Eutectic	Bulk	-49.8	-58	218	1325		0.56	3.28
E-75	PlusICE	Eutectic	Bulk	-75	-103	102	902		0.17	2.43
E-78	PlusICE	Eutectic	Bulk	-78	-108	115	880		0.14	1.96
E-90	PlusICE	Eutectic	Bulk	-90	-130	90	786		0.14	2.56
E-114	PlusICE	Eutectic	Bulk	-114	-173	107	782		0.17	2.39
PCM-HS26N	SAVENRG [85]	Inorganic	Bulk	-26	-15	205	1200
PCM-HS23N	SAVENRG	Inorganic	Bulk	-23	-9	200	1180
PCM-HS10N	SAVENRG	Inorganic	Bulk	-10	14	220	1100
PCM-HS07N	SAVENRG	Inorganic	Bulk	-7	19	230	1120
PCM-HS01P	SAVENRG	Inorganic	Bulk	0	32	290	1010
PCM-OM05P	SAVENRG	Organic	Bulk	5	41	198	770
PCM-0M06P	SAVENRG	Organic	Bulk	5.5	42	260	735
PCM-0M08P	SAVENRG	Organic	Bulk	8	46	190	1050
PCM-0M11P	SAVENRG	Organic	Bulk	11	52	260	1060
PCM-0M21P	SAVENRG	Organic	Bulk	21	70	120	1050
PCM-H22P	SAVENRG	Inorganic	Bulk	22	72	185	1540
PCM-HS24P	SAVENRG	Inorganic	Bulk	24	75	185	1540
PCM-HS29P	SAVENRG	Inorganic	Bulk	29	84	190	1550
PCM-OM32P	SAVENRG	Organic	Bulk	32	90	235	870
PCM-OM35P	SAVENRG	Organic	Bulk	35	95	197	870
PCM-HS34P	SAVENRG	Inorganic	Bulk	34	93	150	1850
PCM-OM37P	SAVENRG	Organic	Bulk	37	99	218	880
PCM-OM46P	SAVENRG	Organic	Bulk	46	115	245	860
PCM-OM48P	SAVENRG	Organic	Bulk	48	118	255	980
PCM-OM53P	SAVENRG	Organic	Bulk	53	127	192	860
PCM-OM65P	SAVENRG	Organic	Bulk	65	149	210	840
PCM-HS89P	SAVENRG	Inorganic	Bulk	89	192	180	1540
MPCM -30	Microtek [86]	Organic	Micro-encapsulated	-30	-22	145
MPCM -30D	Microtek	Organic	Micro-encapsulated	-30	-22	145
MPCM -10	Microtek	Organic	Micro-encapsulated	-9.5	15	155
MPCM -10D	Microtek	Organic	Micro-encapsulated	-9.5	15	155
MPCM 6	Microtek	Organic	Micro-encapsulated	6	43	162
MPCM 6D	Microtek	Organic	Micro-encapsulated	6	43	162
MPCM 18	Microtek	Organic	Micro-encapsulated	18	64	168
MPCM 18D	Microtek	Organic	Micro-encapsulated	18	64	168
MPCM 28	Microtek	Organic	Micro-encapsulated	28	82	187.5
MPCM 28D	Microtek	Organic	Micro-encapsulated	28	82	187.5
MPCM28D-IR	Microtek	Organic	Micro-encapsulated	56	133	170
MPCM 37	Microtek	Organic	Micro-encapsulated	37	99	195
MPCM 37D	Microtek	Organic	Micro-encapsulated	37	99	195
MPCM 43D	Microtek	Organic	Micro-encapsulated	43	109	195
MPCM 56D	Microtek	Organic	Micro-encapsulated	56	133	170
Latest 29 T	TEAP	Inorganic	Bulk	28	82	175	1490		1	2
Latest 25 T	TEAP	Inorganic	Bulk	24	75	175	1490		1	2
Latest 20 T	TEAP	Inorganic	Bulk	19	66	175	1490		1	2
Latest 18 T	TEAP	Inorganic	Bulk	17	63	175	1490		1	2
CrodaTherm™ 5	Croda International Plc [87]	Organic	Bulk	5	41	191
CrodaTherm™ 6.5	Croda International Plc	Organic	Bulk	6.8	44	184
CrodaTherm™ 15	Croda International Plc	Organic	Bulk	15	59	177
CrodaTherm™ 21	Croda International Plc	Organic	Bulk	21	70	176
CrodaTherm™ 29	Croda International Plc	Organic	Bulk	29	84	207
CrodaTherm™ 53	Croda International Plc	Organic	Bulk	53	127	226

The above dataset is also available as an Excel spreadsheet from UCLA Engineering

Technology, development and encapsulation

The most commonly used PCMs are salt hydrates, fatty acids and esters, and various paraffins (such as octadecane). Recently also ionic liquids were investigated as novel PCMs.

As most of the organic solutions are water-free, they can be exposed to air, but all salt based PCM solutions must be encapsulated to prevent water evaporation or uptake. Both types offer certain advantages and disadvantages and if they are correctly applied some of the disadvantages becomes an advantage for certain applications.

They have been used since the late 19th century as a medium for the thermal storage applications. They have been used in such diverse applications as refrigerated transportation^[88] for rail^[89] and road applications^[90] and their physical properties are, therefore, well known.

Unlike the ice storage system, however, the PCM systems can be used with any conventional water chiller both for a new or alternatively retrofit application. The positive temperature phase change allows centrifugal and absorption chillers as well as the conventional reciprocating and screw chiller systems or even lower ambient conditions utilizing a cooling tower or dry cooler for charging the TES system.

The temperature range offered by the PCM technology provides a new horizon for the building services and refrigeration engineers regarding medium and high temperature energy storage applications. The scope of this thermal energy application is wide ranging of solar heating, hot water, heating rejection, i.e. cooling tower and dry cooler circuitry thermal energy storage applications.

Since PCMs transform between solid–liquid in thermal cycling, encapsulation^[91] naturally become the obvious storage choice.

• Encapsulation of PCMs
  • Macro-encapsulation: Early development of macro-encapsulation with large volume containment failed due to the poor thermal conductivity of most PCMs. PCMs tend to solidify at the edges of the containers preventing effective heat transfer.
  • Micro-encapsulation: Micro-encapsulation on the other hand showed no such problem. It allows the PCMs to be incorporated into construction materials, such as concrete, easily and economically. Micro-encapsulated PCMs also provide a portable heat storage system. By coating a microscopic sized PCM with a protective coating, the particles can be suspended within a continuous phase such as water. This system can be considered a phase change slurry (PCS).
  • Molecular-encapsulation is another technology, developed by Dupont de Nemours that allows a very high concentration of PCM within a polymer compound. It allows storage capacity up to 515 kJ/m² for a 5 mm board (103 MJ/m³). Molecular-encapsulation allows drilling and cutting through the material without any PCM leakage.

As phase change materials perform best in small containers, therefore they are usually divided in cells. The cells are shallow to reduce static head – based on the principle of shallow container geometry. The packaging material should conduct heat well; and it should be durable enough to withstand frequent changes in the storage material's volume as phase changes occur. It should also restrict the passage of water through the walls, so the materials will not dry out (or water-out, if the material is hygroscopic). Packaging must also resist leakage and corrosion. Common packaging materials showing chemical compatibility with room temperature PCMs include stainless steel, polypropylene and polyolefin.

Thermal composites

Thermal-composites is a term given to combinations of phase change materials (PCMs) and other (usually solid) structures. A simple example is a copper-mesh immersed in a paraffin-wax. The copper-mesh within parraffin-wax can be considered a composite material, dubbed a thermal-composite. Such hybrid materials are created to achieve specific overall or bulk properties.

Thermal conductivity is a common property which is targeted for maximisation by creating thermal composites. In this case the basic idea is to increase thermal conductivity by adding a highly conducting solid (such as the copper-mesh) into the relatively low conducting PCM thus increasing overall or bulk (thermal) conductivity. If the PCM is required to flow, the solid must be porous, such as a mesh.

Solid composites such as fibre-glass or kevlar-pre-preg for the aerospace industry usually refer to a fibre (the kevlar or the glass) and a matrix (the glue which solidifies to hold fibres and provide compressive strength). A thermal composite is not so clearly defined, but could similarly refer to a matrix (solid) and the PCM which is of course usually liquid and/or solid depending on conditions. They are also meant to discover minor elements in the earth.

Applications

Phase-change material being employed in the treatment of neonates with birth asphyxia^[92][93]

Applications^[1][94] of phase change materials include, but are not limited to:

• Thermal energy storage
• Solar cooking
• Cold Energy Battery
• Conditioning of buildings, such as 'ice-storage'
• Cooling of heat and electrical engines
• Cooling: food, beverages, coffee, wine, milk products, green houses
• Medical applications: transportation of blood, operating tables, hot-cold therapies, treatment of birth asphyxia^[92]
• Human body cooling under bulky clothing or costumes.
• Waste heat recovery
• Off-peak power utilization: Heating hot water and Cooling
• Heat pump systems
• Passive storage in bioclimatic building/architecture (HDPE, paraffin)
• Smoothing exothermic temperature peaks in chemical reactions
• Solar power plants
• Spacecraft thermal systems
• Thermal comfort in vehicles
• Thermal protection of electronic devices
• Thermal protection of food: transport, hotel trade, ice-cream, etc.
• Textiles used in clothing
• Computer cooling
• Turbine Inlet Chilling with thermal energy storage
• Telecom shelters in tropical regions. They protect the high-value equipment in the shelter by keeping the indoor air temperature below the maximum permissible by absorbing heat generated by power-hungry equipment such as a Base Station Subsystem. In case of a power failure to conventional cooling systems, PCMs minimize use of diesel generators, and this can translate into enormous savings across thousands of telecom sites in tropics.

Fire and safety issues

Some phase change materials are suspended in water, and are relatively nontoxic. Others are hydrocarbons or other flammable materials, or are toxic. As such, PCMs must be selected and applied very carefully, in accordance with fire and building codes and sound engineering practices. Because of the increased fire risk, flamespread, smoke, potential for explosion when held in containers, and liability, it may be wise not to use flammable PCMs within residential or other regularly occupied buildings. Phase change materials are also being used in thermal regulation of electronics.

See also

• Heat pipe

References

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Further reading

• Raoux, S. (2009). "Phase Change Materials". Annual Review of Materials Research. 39: 25–48. Bibcode:2009AnRMS..39...25R. doi:10.1146/annurev-matsci-082908-145405.