Medium Temperature Latent Heat Storage with Phase Change Materials Jose Cunha j.pereira-da-cunha@lboro.ac.uk CREST Loughborough University
Storage Introduction Effectiveness Density Thermochemical Storage; • Seasonal storage; o Salt Hydrates; o High Temperature storage; o CCS; o Latent heat Storage; • Solar: o Cooling: • Absorption Chillers (80-110 C); o Adsorption Chillers (70-85 C); o Ejection cycles (40 – 200 C); o Thermal: • DWH (40-60 C); o ORC (80 – 120 C): o Industrial Waste Heat (90-160 C) o Geothermal ORC (100 – 200 C); o Sensible Heat storage; • Thermoelectric cycles (400-700 C); o
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 T melt Δ H fusion E density Price Organic Melts CAS kWh/m 3 °C kJ/kg £/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 Alkanes Hydrocarboxylic Acids Sugar Alcohols
Material Review Mass T melt Δ H fusion E density Price Inorganic Eutectics Ratio kWh/m 3 °C kJ/kg £/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 53-40-7 142 148 94 15 (HiTec salt) 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 N = Normal pan • Material Analysis H = Hermetic Pan S = Stitched Pan T melt T cryst Δ T Cp s Cp l E density Price Organic Melts CAS Lid °C kJ/kg.K kWh/m 3 £/kWh Adipic acid 124-04-9 155 146 9 1.75 2.14 91 11 H 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 m/m T melt T cryst Δ T Cp s Cp l E density Price Eutectic Melts Lid % °C kJ/kg.K kWh/m 3 £/kWh LiNO 3 -KNO 3 33-63 133 104 29 1.14 1.41 84 49 LiNO 3 -NaNO 3 -KNO 3 30-18-52 127 82 45 1.4 1.75 91 42 LiNO 3 -KCl 58-42 169 154 15 1.85 1.94 94 55 S "+ 3% NaNO 3 " 56-3-41 167 150 17 1.54 1.7 100 53 KNO 3 -NaNO 2 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
Container Development Encapsulated Static properties Compact Static properties A spec 100 25 [m 2 /m 3 cont ] A spec 100 25 [m 2 /m 3 cont ] [H/D] cont 29.5 7.5 [De/Di] tube 2.45 4.58 D cont 100 160 D tube 8 8 [mm] [mm] N sections 118 15 D e 19.6 36.7 N shperes 1180 30 L tube 36.73 9.18 [m] D sphere 25 80 [mm] L fraction 0.82 0.82 [kWh/kWh] L fraction 0.75 0.71 [kWh/kWh] Z fraction 0.83 0.95 [m 3 /m 3 ] Z fraction 0.49 0.42 [m 3 /m 3 ] • Larger HT area – lower latent fraction • Larger HT area – larger latent fraction Vertical array Horizontal Array Shell and tubes Coil in tank
Thermal Modelling • • Compact Latent Heat Systems Encapsulated Latent Heat Systems o o Section View Section View 100 m 2 / m 3 25 m 2 / m 3 100 m 2 / m 3 25 m 2 / m 3 A spec 100 25 [m 2 /m 3 cont ] A spec 100 25 [m 2 /m 3 cont ] Q 0.587 [l/min] Q 34 13.6 [l/min] Re = 500 Re = 500 W max 342.12 [W] W max 198.3 7932 [W] h 246.4 [W/m 2 .K] h 242.6 60.65 [W/m 2 .K] Q 5.87 [l/min] Q 3.4 136 [l/min] Re = 5000 Re = 5000 W max 3421.2 [W] W max 1983 79320 [W] [W/m 2 .K] [W/m 2 .K] h 1503 h 894.1 223.5 • Performance Metrics: 𝑅 𝑅 = 𝑛 . 𝐷𝑞 𝑔 . 𝑈 𝑗𝑜 − 𝑈 𝑝𝑣𝑢 𝑔 𝑋 ; 𝑋 𝐿 𝑉𝐵 = ; 𝑄𝐷𝑁 𝑈 𝑔 − 𝑈
Thermal Modelling • • Compact Latent Heat Systems Encapsulated Latent Heat Systems
Thermal Modelling • • Encapsulated Latent Heat Systems Compact Latent Heat Systems o Initial sensible heat stage; o Resistivity ratio remains constant trough all the charging o Exponential growth in the conductive ratio, reaching a maximum near the end of the charging process; process; o Curve non-smoothness due to the lower spatial resolution achieved;
Heat Source Thermal Performance Test o Closed loop with heat exchanger to Shell and Tubes Heat connect with any source; Exchanger sensors o Initial data acquisition system ṁ Expansion measuring: Δ T vessel pump • Inlet – outlet from thermal storage container; • Inlet – outlet from heat TES Δ T exchanger; Container • Mass flow; • Differential inlet-outlet pressure from thermal storage container; DAQ System
Sensor Error flow meter +- 0.0072 l/min Thermal Performance Test RTD +- 0.1 °C 𝑓 𝑅 = 𝑓 𝑊 𝑔 . 𝜍 𝑔 . 𝐷𝑞 𝑔 . 2. 𝑓 ∆𝑈 = ±0.042𝑋
Thermal Performance Test
Thank You for the attention
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