Heat Storage with Phase Change Materials Jose Cunha - - PowerPoint PPT Presentation

Medium Temperature Latent Heat Storage with Phase Change Materials

Jose Cunha

j.pereira-da-cunha@lboro.ac.uk CREST Loughborough University

Introduction

• Thermochemical Storage;
• Seasonal storage;
• Salt Hydrates;
• High Temperature storage;
• CCS;
• Latent heat Storage;
• Solar:
• Cooling:
• Absorption Chillers (80-110 C);
• Adsorption Chillers (70-85 C);
• Ejection cycles (40 – 200 C);
• Thermal:
• DWH (40-60 C);
• ORC (80 – 120 C):
• Industrial Waste Heat (90-160 C)
• Geothermal ORC (100 – 200 C);
• Sensible Heat storage;
• Thermoelectric cycles (400-700 C);

Effectiveness Storage Density

Scope

• Study the materials with potential phase changes from 90 to 180 ºC:
• relevant physical properties:
• thermal stability;
• heat capacity;
• latent heat;
• thermal conductivity;
• corrosion stability;
• possible enhancing mechanisms;
• Develop latent heat thermal storage systems;
• Reliability;
• Economical;
• Safe;
• Develop performance algorithms;
• practical performance metrics;
• correlate with experimental data;

Material Review

Organic Melts CAS Tmelt ΔHfusion Edensity Price

°C kJ/kg kWh/m3 £/kWh

Maleic acid 110-16-7 131 235 109 11 Adipic acid 124-04-9 152 220 101 15 HDPE 9002-88-4 135 260 69 9 Phthalic anhydride 85-44-9 131 160 68 38 2-Chlorobenzoic acid 118-91-2 142 164 75 35 Erythritol 149-32-6 117 311 134 22 d-Mannitol 69-65-8 165 300 132 23

Aromatic Hydrocarbons Hydrocarboxylic Acids Alkanes Sugar Alcohols

Material Review

Inorganic Eutectics Mass Ratio Tmelt ΔHfusion Edensity Price

°C kJ/kg kWh/m3 £/kWh LiNO3-NaNO3-KNO3 30-18-52 120 135 78 59 LiNO3-KNO3 33-67 133 160 99 58 KNO3-NaNO2 56-44 141 145 91 11 KNO3-NaNO2-NaNO3 (HiTec salt) 53-40-7 142 148 94 15 KNO2-NaNO3 48-52 149 153 94 27 LiNO3-KCl 44-56 160 272 174 47 LiOH-LiNO3 19-81 183 776 484 65 LiNO3-NaNO3 48-52 190 280 175 62

Material Analysis

• Vaporization in their liquid state;
• Unstable without encapsulation;

Material Analysis

• Mannitol and HDPE seemed stable in

molten state;

• Adipic Acid seemed suitable, but thermal

stage indicated also full vaporization in molten state;

Material Analysis

• DSC analysis obtained values below the

literature review;

• Adipic Acid proved thermal stability only

in hermetic container;

Material Analysis

• Phthalic anhydride and 2-Chlorobenzoic

acid proved relative stability in closed container;

• Maleic acid is unsuitable for latent heat

thermal storage;

Material Analysis

• Excellent thermal stability;
• Very hygroscopic;

Material Analysis

• LiNO3/KCl eutectic mixture has shown

great storage densities;

• NaNO2 mixtures were non-hygroscopic;

Analysis Results

Organic Melts CAS Lid Tmelt T

cryst

ΔT Cps Cpl Edensity Price °C kJ/kg.K kWh/m3 £/kWh Adipic acid 124-04-9 H 155 146 9 1.75 2.14 91 11 2-Chlorobenzoic acid 118-91-2 141 134 7 1.39 1.67 60 48 d-Mannitol 69-65-8 N 169 126 43 1.7 2.4 120 27 Eutectic Melts m/m Lid Tmelt T

cryst

ΔT Cps Cpl Edensity Price % °C kJ/kg.K kWh/m3 £/kWh LiNO3-KNO3 33-63 S 133 104 29 1.14 1.41 84 49 LiNO3-NaNO3-KNO3 30-18-52 127 82 45 1.4 1.75 91 42 LiNO3-KCl 58-42 169 154 15 1.85 1.94 94 55 "+ 3% NaNO3" 56-3-41 167 150 17 1.54 1.7 100 53 KNO3-NaNO2 56-44 143 139 4 1.55 1.84 37 27 Hitec Salt 53-7-40 144 142 2 1.15 1.25 48 16 "+ 10% NaCl" 47-6-37-10 140 133 7 1.20 1.28 43 14

N = Normal pan H = Hermetic Pan S = Stitched Pan

• Material Analysis

Container Development

• Larger HT area – lower latent fraction

Aspec 100 25 [m2/m3

cont]

[H/D]cont 29.5 7.5 Dcont 100 160 [mm] N sections 118 15 Nshperes 1180 30 Dsphere 25 80 [mm] L fraction 0.75 0.71 [kWh/kWh] Z fraction 0.49 0.42 [m3/m3] Aspec 100 25 [m2/m3

cont]

[De/Di]tube 2.45 4.58 Dtube 8 8 [mm] De 19.6 36.7 Ltube 36.73 9.18 [m] L fraction 0.82 0.82 [kWh/kWh] Z fraction 0.83 0.95 [m3/m3]

• Larger HT area – larger latent fraction

Encapsulated Static properties Compact Static properties

Vertical array Horizontal Array Shell and tubes Coil in tank

Thermal Modelling

• Compact Latent Heat Systems
• Section View
• Encapsulated Latent Heat Systems
• Section View

Aspec 100 25 [m2/m3

cont]

Re = 500

Q 0.587 [l/min] Wmax 342.12 [W] h 246.4 [W/m2.K]

Re = 5000

Q 5.87 [l/min] Wmax 3421.2 [W] h 1503 [W/m2.K] Aspec 100 25 [m2/m3

cont]

Re = 500

Q 34 13.6 [l/min] Wmax 198.3 7932 [W] h 242.6 60.65 [W/m2.K]

Re = 5000

Q 3.4 136 [l/min] Wmax 1983 79320 [W] h 894.1 223.5 [W/m2.K]

100 m2 / m3 25 m2 / m3 100 m2 / m3 25 m2 / m3

• Performance Metrics:

𝑅 = 𝑛 . 𝐷𝑞𝑔. 𝑈𝑗𝑜 − 𝑈𝑝𝑣𝑢 𝑔 𝑋 ; 𝑉𝐵 = 𝑅 𝑈

𝑔 − 𝑈

𝑄𝐷𝑁 𝑋 𝐿 ;

Thermal Modelling

• Compact Latent Heat Systems
• Encapsulated Latent Heat Systems

Thermal Modelling

• Compact Latent Heat Systems
• Resistivity ratio remains constant trough all the charging

process;

• Encapsulated Latent Heat Systems
• Initial sensible heat stage;
• Exponential growth in the conductive ratio, reaching a maximum

near the end of the charging process;

• Curve non-smoothness due to the lower spatial resolution achieved;

Thermal Performance Test

• Closed loop with heat exchanger to

connect with any source;

• Initial data acquisition system

measuring:

• Inlet – outlet from thermal storage

container;

• Inlet – outlet from heat

exchanger;

• Mass flow;
• Differential inlet-outlet pressure

from thermal storage container;

Shell and Tubes Heat Exchanger

DAQ System

TES Container

ΔT

ṁ

ΔT

pump sensors Heat Source

Expansion vessel

Thermal Performance Test

Sensor Error flow meter +- 0.0072 l/min RTD +- 0.1 °C

𝑓𝑅 = 𝑓𝑊 𝑔. 𝜍𝑔. 𝐷𝑞𝑔. 2. 𝑓∆𝑈 = ±0.042𝑋

Thermal Performance Test

Thank You for the attention