U21 International Conference on Energy Technologies and Policy 8th to 10th September 2008, Birmingham, UK Use of Phase Change Materials for Thermal Comfort and Electrical Energy Peak Load Shifting Mohammed Farid and Nahidh Mecaial Department of Chemical & Materials Engineering The University of Auckland, New Zealand
Why Thermal Storage? How heat is lost from buildings? What is thermal energy storage (TES)? Why do we want to increase thermal mass of buildings? How can thermal energy be stored? Why do we use phase change materials (PCMs)? How do we use PCM s (micro and macro encapsulation)? Demonstrating the benefits of using PCM.
Percentages of heat losses from ordinary homes (EECA, 2004)
Thermal Mass of Buildings Do we improve buildings insulation only or do we need to increase their thermal mass? How can we increase thermal mass of buildings without going back to the heavy construction used in the old days?
Heavy thermal mass construction: Egyptian mud-brick rooms, 3200 years old
Phase Change Materials What are the phase change materials (PCMs)? How do they work? How can they be encapsulated in building materials?
Phase Change (melting and solidification at almost constant temperature)
Energy density of thermal storage materials (Rubitherm, 2003)
THERMAL MASS OF PCM-GYPSUM WALLBOARDS (PCMGW) Heat Stored (kj/kg) 70 60 50 40 30 20 10 Gypsum Wallboard Gypsum Wallboard with 24% RT20 by weight 0 10 15 20 25 30 35 Temperature ( o C)
FULL-SCALE SIZE TESTING FACILITY Schematic plan view of outdoor full-scale test-rooms 2400 2600 2500 1100 1200 EQ PVC Spouting 1200 Alum inium fr am e d window 760 x 2000 standard external door in timber frame Door 760 Electricity Board 94mm Insulation EQ 800 * All constructions comply with NZS 3604 Timber stand North Timber steps ** All measurments in mm North Elevation South elevation is similar but with no window East Elevation West elevation is similar but with no door
CONSTRUCTION North-facing test rooms
THEORETICAL ANALYSIS AND SIMULATION Internal Side Insulation Siding External Side Table 1: Thermo-physical properties of the mass types Sp. Heat Conduct. Density Thick. Mass (W/m K) (kg/m 3 (kj/kg ) (m) K) Board 0.25 670 1.089 0.013 Insulation 0.038 32 0.835 0.075 Wood 0.12 510 1.38 0.025 Siding 0.094 640 1.17 0.01 Table 2: Thermo-physical properties of the PCM Gypsum Boards Wood Conductivity (W/mK) Density (kg/m 3 ) Sp. Heat (kj/kgk) 0.2 810 2.1 Latent Heat (kj/kg) Melting Point ( o C) Thickness (m) 172 20 0.004
USE OF THERMAL ENERGY STORAGE IN SUMMER FOR THERMAL COMFORT
Solar radiation and wind speed measurements (1 st to 8 th of January 2007) 1400 1200 Solar Radiation Wind Speed 10 8 Solar Radiation (W/sq m) 1000 800 600 400 200 6 4 2 Wind Speed (m/s) 0 0 00:0012:0000:0012:0000:0012:0000:0012:0000:0012:0000:0012:0000:0012:0000:00 Time
Ambient and indoor room s temperatures (1 st to 8 th of Jan., 2007) 32 30 28 Temp. of GW Hut Temp. of PCMGW Hut Ambient Temp. 26 Temperature (oc) 24 22 20 18 16 14 12 10 8 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 Time PCM room T PCM ORD room T ORD 24.07-18.60 o C 5.47 o C 24.71-15.08 o C 9.63 o C
Simulated inside room s temperature (1 st to 8 th of January 2007) 32 30 28 Simulation GW Room Temp. Simulation GWPCM Room Temp. Ambient Temp. 26 Temperature (oc) 24 22 20 18 16 14 12 10 8 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 Time PCM room T PCM ORD room T ORD 22.37-17.55 o C 4.82 o C 27.07-13.96 o C 13.11 o C
USE OF THERMAL ENERGY STORAGE IN WINTER FOR CAPTURING SOLAR RADIATION AND SHIFTING HEATING LOAD
Measurements of Solar radiation and wind speed (18 th to 21 th of July, 2006) 500 450 400 Solar Radiation Wind Speed 10 8 Solar Radiation (W/sq m) 350 300 250 200 150 100 6 4 2 Wind Speed (m/s) 50 0 0 00:0006:00 12:00 18:0000:00 06:0012:00 18:00 00:0006:00 12:00 18:0000:00 06:00 Time
Measured Indoor rooms temperatures (18 th to 21 th of July, 2006) 30 25 Temperature (oc) 20 15 10 5 Temp. of GW room Temp. of PCMGW room Ambient Temperature 0 00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00 06:00 Time
Simulated indoor rooms temperatures (18 th to 21 th of July, 2006) 30 25 Temperature (oc) 20 15 10 5 0 00:0006:00 12:0018:0000:0006:00 12:0018:0000:0006:00 12:0018:0000:0006:00 12:0018:0000:00 Time Temp. of GWPCM Room Temp. of GW board Room Ambient Temperature
Solar radiation and wind speed measurements (17 th to 22 th July, 2008) Heating systems (1am to 7 am), (850W) 600 10 500 Solar Radiation Wind Speed 8 Solar Radiation (W/sq m) 400 300 200 100 6 4 2 Wind Speed (m/s) 0 0 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 Time
Measurement s of rooms indoor temperatures (17 th to 22 rd July, 2008) Heating systems (1 am to 7 am), (850W) 32 30 28 Ambient Temp. Temp. of GW Room Tem. of GWPCM Room 26 Temperature (oc) 24 22 20 18 16 14 12 10 8 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 Time
Measurements of solar radiation and wind speed (29 th July to 3 th August, 2008) Heating systems (5 pm to 11 pm), (850W) 600 10 500 Solar Radiation Wind Speed 8 Solar Radiation (W/sq m) 400 300 200 100 6 4 2 Wind Speed (m/s) 0 0 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 Time
Measurements of indoor rooms temperatures (29 th July to 3 th August, 2008) Heating systems (5pm to 11 pm), (850W) 32 30 28 Ambient Temp. Temp. of GW Room Tem. of GWPCM Room 26 Temperature (oc) 24 22 20 18 16 14 12 10 8 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 12:00 00:00 Time
Effect of PCM quantity used Simulation of indoor air temperatures 30 28 0.005 m 0.01m No PCM 26 Temperature (oc) 24 22 20 18 16 0 20 40 60 80 100 120 140 160 Time (h)
Effect of PCM melting point Simulation of indoor air temperatures 30 28 20 C Melting Point 22 Melting Point 18 Melting Point No PCM 26 Temperature (oc) 24 22 20 18 16 0 20 40 60 80 100 120 140 160 Time (h)
NUMBER OF SUMMER DAYS BENIFITING FROM THE USE OF PCM 36 34 32 30 39% full utilization 55.5% partial utilization 5.5% no utilization Temperature ( o C) 28 26 24 22 20 18 16 14 12 0 120 240 360 480 600 720 840 960 1080 1200 1320 1440 1560 1680 1800 1920 2040 2160 Time (hour)
CONCLUSIONS 1. Building materials impregnated with PCM efficiently smooth- out daily temperature fluctuations. It leads to a healthier interior spaces with more pleasant temperatures. 2. Use of PCM-building materials can reduce heating or cooling cost by using strategies of peak load shifting. 3. PCM-building materials could be installed with the same technique and equipments used for conventional building materials. 4. Micro or macro encapsulation of the PCM is necessary to prevent PCM leakage