A Review of Thermal Analysis on Novel Roofing Systems. Yuanpei Song Purdue University

Transcription

1 A Review of Thermal Analysis on Novel Roofing Systems Yuanpei Song Purdue University

2 Outline Objective Cool roof Green roof PCM roof

3 Objective Summarize» key s» thermal analysis methodologies,» energy savings Provide a comprehensive thermal analysis method applied in novel roof systems.

4 Cool Roof Cool roofs are designed to keep the roof cool by reflecting the incident solar radiation away from the building roof and radiating the stored heat away at night. Proven benefits:» Saving energy consumption of cooling,» Improving indoor comfort,» Mitigating the heat island phenomena,» Reducing maintenance by extension lifetime.

5 Location Roof color Experiments Simulation Akbari et al. California Gray 6 buildings calibrated DOE-2 Reflectance up to $2.0/m 2 in the value of total annual air conditioning savings Prado et al. Synnefa et al. (2006) Red, white, etc. Silver, white spectral characteristics measurement 14 types of sample Albedo Spectral reflectance, the infrared emittance lower surrounding temperatures and cooler surfaces with raised albedo Reflectance dominates in daytime while emissivity does during night. Levinson et al. (2007) California terracotta, chocolate, gray, green, blue, black Scale houses Emittance, reflectance Statewide peak cooling reduction of 240MW, annual cooling saving of 63GWh/yr, annual emissions of 35 ton CO 2, 1.1 ton NO x, and 0.86 ton SO x Synnefa et al. (2007) World wide TRNSYS Reflectance, U-value Heating penalty is much less than cooling load reduction. Jo et al. (2010) Phoenix White Full scale EnergyPlus Albedo Electricity saving up to 18% Uemoto et al. (2010) White, brown, yellow UV/VIS/NIR reflectance measured Reflectance Cool colored pigments produce significantly higher NIR reflectance and lower surface temperature by 10 C.

6 Akbari et al. Prado et al. Synnefa et al. (2006) Location Roof color Experiments Simulation California Gray 6 buildings Red, white, etc. Silver, white spectral characteristics measurement 14 types of sample Albedo Spectral reflectance, the infrared emittance Used calibrated DOE-2 simulation calibrated to extrapolate savings up to $2.0/m for Reflectance 2 in three the value types of total of one-story commercial building DOE-2 in 16 different California annual air conditioning climatesavings lower surrounding temperatures and cooler surfaces with raised albedo Reflectance dominates in daytime while emissivity does during night. Levinson et al. (2007) California terracotta, chocolate, gray, green, blue, black Scale houses Emittance, reflectance Statewide peak cooling reduction of 240MW, annual cooling saving of 63GWh/yr, annual emissions of 35 ton CO 2, 1.1 ton NO x, and 0.86 ton SO x Synnefa et al. (2007) World wide TRNSYS Reflectance, U-value Heating penalty is much less than cooling load reduction. Jo et al. (2010) Phoenix White Full scale EnergyPlus Albedo Electricity saving up to 18% Uemoto et al. (2010) residential energy load for 27 cities around the world representing different climatic conditions in TRNSYS analyzed the cost benefit and indirect benefits by comparing three different cases in EnergyPlus White, brown, yellow UV/VIS/NIR reflectance measured Reflectance Cool colored pigments produce significantly higher NIR reflectance and lower surface temperature by 10 C.

7 Location Roof color Experiments Simulation Akbari et al. Prado et al. Synnefa et al. (2006) calibrated up to $2.0/m California Gray 6 buildings Reflectance 2 in the value of total Collected detailed DOE-2 data of six buildings annual air conditioning savings spectral Red, white, etc. characteristics measurement Albedo Spectral reflectance, the infrared emittance lower surrounding temperatures and cooler surfaces with raised albedo Measured the spectral characteristics of over 10 types of material Surface temperatures 14 types of of 14 reflective materials in daytime and during Silver, white sample night. Reflectance dominates in daytime while emissivity does during night. Levinson et al. (2007) California terracotta, chocolate, gray, green, blue, black Scale houses Emittance, reflectance Statewide peak cooling reduction of 240MW, annual cooling saving of 63GWh/yr, annual emissions of 35 ton CO 2, 1.1 ton NO x, and 0.86 ton SO x Compared six colors with scale houses located in California Synnefa et al. (2007) World wide TRNSYS Reflectance, U-value Heating penalty is much less than cooling load reduction. Temperatures and albedo of white-colored roof in full-scale building in Phoenix Jo et al. (2010) Phoenix White Full scale EnergyPlus Albedo Electricity saving up to 18% Uemoto et al. (2010) White, brown, yellow UV/VIS/NIR reflectance measured Reflectance Cool colored pigments produce significantly higher NIR reflectance and lower surface temperature by 10 C.

8 Akbari et al. Prado et al. Synnefa et al. (2006) Location Roof color Experiments Simulation California Gray 6 buildings Red, white, etc. Silver, white spectral characteristics measurement 14 types of sample Albedo Spectral reflectance, the infrared emittance up to $2.0/m 2 in the value of total calibrated annual air conditioning savings for onestory commercial DOE-2 Reflectance building. up to $2.0/m 2 in the value of total annual air conditioning savings lower surrounding temperatures and cooler surfaces with raised albedo Reflectance dominates in daytime while emissivity does during night. Levinson et al. (2007) California terracotta, chocolate, gray, green, blue, black Scale houses Emittance, reflectance Statewide peak cooling reduction of 240MW, annual cooling saving of 63GWh/yr, annual emissions of 35 ton CO 2, 1.1 ton NO x, and 0.86 ton SO x Synnefa et al. (2007) 4 C and 2 C during the day and night respectively lower than the ambient in hot condition when white concrete tile is used in World wide TRNSYS Reflectance, U-value Heating penalty is much less than cooling load reduction. Jo et al. (2010) Phoenix White Full scale EnergyPlus Albedo Electricity saving up to 18% 18% electricity saving in Phoenix. Uemoto et al. (2010) White, brown, yellow UV/VIS/NIR reflectance measured Reflectance Cool colored pigments produce significantly higher NIR reflectance and lower surface temperature by 10 C.

9 Green Roof Also know as eco-roof, covered by vegetation Components: vegetation layer, soil layer, webbing filter and drainage material, etc. Types: intensive and extensive Mechanism:» evapo-transpiration of vegetation» insulation of roof layers

10 Liu et al. (2003) Location Vegetation Experiments Simulation Ottawa wild flower meadow 2-year 75% decrease in heat flux through roofing system Kumar et al. India Validating canopy temperature Numerical LAI 3 kwh cooling capacity per day Lazzarin et al. Summer, winter Numerical Latent flux Wet green roof in summer can even result in an outgoing flux. Santamouris et al. (2007) Local wild plants Two stories TRNSYS Significant reduction in cooling load, no important impacts on heating load. Sailor (2008) Chicago, Houston Two stories FASST vegetation integrated in EnergyPlus Soil thickness, LAI, and irrigation. The is applicable. Parizotto et al. (2011) Bulbine frutescens Compared with ceramic and metallic tiles Climate condition Cooling capacity of green roof is reduced in high relative humidity climate. Zinzi et al. (2012) Mediterranean Numerical Green roof is less effective than cool roof.

11 Liu et al. (2003) Location Vegetation Experiments Simulation Ottawa wild flower meadow 2-year 75% decrease in heat flux through roofing system Kumar et al. Lazzarin et al. utilized a control volume approach based on finite difference methods to Validating India analyze layer components canopy which Numerical was coupled LAI into building 3 kwh cooling simulation capacity per day temperature codes later developed Summer, a numerical and Numerical compared Latent the flux ing prediction with winter experimental results Wet green roof in summer can even result in an outgoing flux. Santamouris et al. (2007) Local wild plants Two stories TRNSYS Significant reduction in cooling load, no important impacts on heating load. Sailor (2008) Chicago, Houston Two stories FASST vegetation integrated in EnergyPlus Soil thickness, LAI, and irrigation. The is applicable. Parizotto et al. (2011) Bulbine frutescens Compared with ceramic and metallic tiles Climate condition Cooling capacity of green roof is reduced in high relative humidity climate. Zinzi et al. (2012) presented a numerical comparative analysis between cool and green roofs Mediterranean Numerical Green roof is less effective than cool roof.

12 Liu et al. (2003) Kumar et al. Location Vegetation Experiments Simulation developed wild a numerical flower and compared the ing prediction with Ottawa 2-year meadow experimental results 75% decrease in heat flux through roofing system Validating India performed an experimental canopy study Numerical which lasted LAI two 3 years kwh cooling Ottawa capacity per day temperature Lazzarin et al. Summer, winter Numerical Latent flux Wet green roof in summer can even result in an outgoing flux. Santamouris et al. (2007) Local wild plants Two stories TRNSYS Significant reduction in cooling load, no important impacts on heating load. Sailor (2008) Chicago, Houston FASST vegetation integrated in EnergyPlus Soil thickness, LAI, and irrigation. developed a green roof module based on s of heat and moisture Two stories exchange. The module has been implemented in EnergyPlus. The is applicable. Parizotto et al. (2011) Bulbine frutescens Compared with ceramic and metallic tiles Climate condition Cooling capacity of green roof is reduced in high relative humidity climate. Zinzi et al. (2012) Mediterranean Numerical Green roof is less effective than cool roof.

13 Liu et al. (2003) Location Vegetation Experiments Simulation Ottawa wild flower meadow 2-year 75% decrease in heat flux through roofing system Kumar et al. Lazzarin et al. Santamouris et al. (2007) average indoor air temperature was reduced by 5 C, and that a cooling Validating potential India of 3 kwh per day canopy at leaf area Numerical index (LAI) of 4 3 was kwh provided cooling capacity based per day temperature on a single room occupied by four people in summer the heat flows in through green roof with dry soil is about 60% Summer, Wet green roof in summer can that in traditional roofing, Numerical Latent flux winter in wet condition, even a slight even outgoing result in an outgoing flux is flux. Local wild plants produced Two stories TRNSYS Significant reduction in cooling load, no important impacts on heating load. Sailor (2008) Chicago, Houston Two stories FASST vegetation integrated in EnergyPlus Soil thickness, LAI, and irrigation. The is applicable. Parizotto et al. (2011) Bulbine frutescens Compared with ceramic and metallic tiles Climate condition Cooling capacity of green roof is reduced in high relative humidity climate. Zinzi et al. (2012) Mediterranean Numerical Green roof is less effective than cool roof.

14 Lazzarin

15 PCM Roof Selection of PCM» Melting temperature (18-30 C)» High latent heat of fusion» chemical stability, fire characteristics and compatibility with construction materials.

16 Location Material Experiments Simulation Saman et al. CaCl 2 6H 2 O Flat Slab 2D enthalpy formulation The effects of sensible heat, inlet air temperature and air flow on freezing and melting were analyzed. Pasupathy et al. (2008) India inorganic salt hydrate Slab 1D numerical Melting temperature and climate Double layer PCM roof is more possible to provide a constantly comfortable temperature all the time in one day and over various seasons. Alawadhi et al. (2011) n-octadecane, n-eicosane, and SUNTECH 3D numerical Geometry 39% reduction in heat flux can be achieved by using n-eicosane as PCM in the conical container. Alqallaf et al. (2013) Kuwait A28, A32, and A38 vertical cylindrical holes 3D finite element method Dimension of cylinder, melting point Heat gain can be reduced more with larger PCM holes diameter. The PCM melting temperature of PCM should be selected based on the operating month and working hour period during the day. Chou et al. (2013) Taiwan Corrugated 1D numerical Amount of PCM The new design (Figure 8) is helpful in reducing the downward heat flux.

17 Location Material Experiments Simulation Saman et al. CaCl 2 6H 2 O Flat Slab 2D enthalpy formulation The effects of sensible heat, inlet air temperature and air flow on freezing and melting were analyzed. Pasupathy et al. (2008) Alawadhi et al. (2011) India inorganic salt hydrate 1D numerical Melting temperature and climate Double layer PCM roof is more possible to provide a constantly comfortable temperature all the time in one day and over various seasons. double layer PCM is Slab more possible to provide a constantly comfortable temperature all the time in one day and over various seasons different materials and geometries of the PCM container were compared, n-octadecane, 39% reduction in heat flux can be 3D numerical optimal n-eicosane, choice and n-eicosane PCM in the conical Geometry container, achieved by giving using n-eicosane 39% as SUNTECH PCM in the conical container. reduction in heat flux Alqallaf et al. (2013) Kuwait A28, A32, and A38 vertical cylindrical holes 3D finite element method Dimension of cylinder, melting point Heat gain can be reduced more with larger PCM holes diameter. The PCM melting temperature of PCM should be selected based on the operating month and working hour period during the day. Chou et al. (2013) Taiwan Corrugated 1D numerical Amount of PCM The new design (Figure 8) is helpful in reducing the downward heat flux.

18 Cool roof» Reflectance and emittance» Building simulation software Green roof» LAI and soil condition» Numerical ing PCM roof» Melting temperature and latent heat» Numerical ing

19 THANKS!