High-reflectance Paint Research Articles

AN INTEGRATING SPHERE SPECTROPHOTOMETER PROTOTYPE

Spectroscopy is essential for research in the qualitative and quantitative analysis of samples. In recent years, the need to develop portable and accessible equipment for sample characterization has reduced real-time analysis. The objective is to design and build a prototype of a portable spectrophotometer with an integrating sphere using tools such as Rhinoceros and Trace-Pro for its theoretical design and radiation simulation. The result is an integrating sphere 3D printed with PLA material and an internal coating with a 95% high reflectance paint. The AS7265 Triad module is the detector, along with signal processing to obtain spectra from control samples. The spectral profiles obtained were comparable with commercial equipment, validating the viability of the measurement system as the first spectroscopic instrument in the field, in complement to other spectroscopic techniques. This breakthrough promises to facilitate research in the field and in environments where mobility and accessibility are priorities. Keywords: Integrating sphere, High reflectance coating, simulation Trace Pro, Manufacturing integrating sphere, spectroscopy.

A new tilted strips external thermal insulation composite system (TiS-ETICS): Description and performance assessment through thermal and energy simulation for a residential building

This work presents a new concept of façades coated with machined ETIC boards displaying tilted strips. Strips with upwards tilt have a high total solar reflectance (TSR) paint, to maximize the solar radiation reflection during the summer period. Strips tilted downwards have a low TSR paint, to maximize the solar absorption during wintertime. Parameters that characterize this new tilted strips ETIC system (TiS-ETICS) were optimized for four different locations: Porto, São Paulo, Los Angeles, and Sydney. The indoor temperature, in the free-floating mode, and the energy demand needed over the year, in conditioned mode, were both assessed through building simulation. The use of TiS-ETICS, compared to pristine façades, always led to a positive impact on performance. In free-floating mode, with the new system, indoor temperatures dropped in summer and increased in winter. In conditioned mode, annual energy savings between 10.8% (in Porto) and 32.3% (São Paulo) were obtained.

Effects of natural aging on the properties of a cool surface exposed in different Brazilian environments

Solar reflectance and thermal emittance are fundamental parameters in the evaluation of a building's thermal and energetic performance, particularly important for “cool” surfaces. However, there is little information on typical values of these parameters in Brazil. We determined values of reflectance, thermal emittance, surface roughness and color difference, for a white high-reflectance paint exposed for two years in 4 cities in the States of São Paulo (SP) and Pará (PA), south-eastern and north Brazil, respectively. After 2 years, painted panels exposed in Pirassununga, SP, showed significantly lower reflectance and increased color difference compared with the original paint and the panels exposed at other sites. This appeared to be related to the presence of a biofilm, in addition to particles of the red clay characteristic of this area. This was likely also to be the explanation of the increased surface roughness determined in Pirassununga samples. Emissivity of the paint changed very little at any of the exposure sites over 2 years, but Solar Reflectance Index, calculated from the average values of reflectance and emittance in the four cities, was reduced from between 105 and 107 to between 94 (in São Sebastião, SP) and 77 (in Pirassununga, SP) after two years. Macroscopically, panels from Pirassununga and Belém, were the most discolored and the greatest presence of biofilm was demonstrated by digital and scanning electron microscopy. Such natural aging studies are important for the production of standard tests and determination of control strategies to increase durability of cool surfaces in Brazil.

Influence of dirt and coating deterioration on the aging of solar reflectance of high-reflectance paint

Cool-roof coatings have received considerable attention worldwide as a solution for the “heat island” effect in urban areas. The solar reflectance of roofs coated with high-reflectance paint is reduced by dirt. We continuously measured the solar reflectance of a roof coated with high-reflectance paint with and without a self-cleaning function for more than two years. The solar reflectance of self-cleaning paint decreased by 0.5% per month over two years, due to the effect of dirt. The solar reflectance of conventional paint decreased by 4% per month over four months after coating and then reached a value similar to that for the self-cleaning paint for two years due to deterioration. With a slight decrease in solar reflectance, the self-cleaning function is effective in mitigating the heat island effect and obtaining continuous energy-savings. We applied the alkyl silicate system as self-cleaning for high-reflectance paint, the solar reflectance was measured continuously at 1 minute intervals, and the actual state of the fluctuation in reflectance over the short and long terms was analyzed with the influence of the altitude of the sun. The deterioration of the coating was also investigated by gloss retention and chalking test.

Using Field Measurements to Assess Aging of Self-Cleaning High-Reflectance Paint

Continuous field measurements were used to evaluate the aging of solar reflectance on self-cleaning coatings for roofs in comparison with conventional coatings that have no self-cleaning function. Solar reflectance on self-cleaning coatings decreases by about 6 % per year with annual variations, due to the adhesion of dirt. On the other hand, solar reflectance on conventional coatings greatly decreases, by approximately 18 % within four months of the coating’s application, due to the adhesion of dirt. Then, it gradually recovers at a rate of about 4 % per year, with annual variations, due to degradation of the coating. It is due to degradation of the conventional coating that the difference of solar reflectance between the self-cleaning coating and the conventional coating becomes almost zero in two years. Both the adhesion of dirt and coating degradation by chalking affect the temporal change of solar reflectance with annual variation.

Optical properties and field test results of spectrally-selective solar control window film that enables not increasing downward reflection

Recently high reflective materials such as high reflectance paint for wall and solar control film or Low-E glass for window are utilized as a building façade aiming for reducing the cooling load of the buildings. From a view point of the direction of reflected rays, almost half of the energy goes upward due to diffuse reflection in case of paint, meanwhile most of energy goes down to the ground due to specular reflection by the glass. This leads to deterioration of thermal environment of surrounding buildings, and is one of causes of urban heat island. Retro-reflective façade materials are promising candidates for mitigation of urban heat island. The authors successfully developed a new type of transparent solar control window film Albeedo that selectively reflects near-infrared rays towards the sky. The film has a saw-tooth microstructure with a spectrally-selective reflection layer. This microstructure is able to reflect infra-red rays toward the sky. The upward reflectance of the film is measured by our custom made spectroscope. Firstly, the sample is placed in a large scale integrating sphere. Then, solar energy absorptive materials are arranged under the sample to absorb the transmitted component and positioned where the downward reflection goes to. Finally, a halogen lamp irradiates the sample at an incident angle of 60° as a light source. The result of the upward reflectance of near-infrared is about 33%. We also conducted field test measurements to evaluate the energy savings of the interior of the building and the degree of reflection of the exterior.

Experimental examination of solar reflectance of high-reflectance paint in Japan with natural and accelerated aging

High-reflectance paint for building envelopes is becoming popular as an urban heat island countermeasure technology for reflecting solar radiation. Solar reflectance, which specifies the performance of the roof coated with high-reflectance paint, is reduced from its initial value in the period soon after coating. Therefore, research on the impact of aging on solar reflectance for the roof coated with high-reflectance paint is required. In this study, field measurements of solar reflectance were carried out on a building rooftop where high-reflectance paint has already been coated. Additionally, solar reflectance for white test plates was measured on building rooftops at three universities. Several accelerated aging tests were reviewed based on the literature, and an accelerated aging test was applied for test plates coated with fluorine-type and aqueous acrylic high-reflectance paints. The reduction begins several months after coating and varies over about 0.10–0.25 several years after coating. It is necessary to secure measurement data immediately after coating for reference purposes. Solar reflectance of the white test plate set on building rooftops at three universities fell by roughly 0.05–0.10 about 50 days after coating. Reduction of spectral solar reflectance is significant in the visible wavelength range. Most of the dirt components are carbon, considered to be derived from organisms and exhaust gas. Both reduction of dirt immediately after coating and coating degradation by chalking over a long period affect the temporal change of solar reflectance. An accelerated test should be developed in order to distinguish between these two effects.

Field Observation of Cooling Energy Savings Due to High-Reflectance Paints

Cooling energy savings in a building with the roof coated with high-reflectance paint are examined. It is difficult to recognize such savings using the data observed hourly. Among the factors assumed to affect cooling energy load are: (1) internal heat generation, (2) set temperature, and (3) weather conditions. By analyzing the relationship between indoor-outdoor air temperature difference (averaged) and electric power consumption (integrated) of the air conditioner in the building over a day, the reduction in electric power consumption due to the use of a high-reflectance paint coating is estimated at approximately 72 Wh·m−2·day−1.

Study on the appropriate selection of urban heat island measure technologies to urban block properties

Abstract In this study, we analyzed the effects of introducing urban heat island measure technologies in a typical street canyon model to aid the selection of a suitable technology. It is appropriate to use street trees for improving the thermal environment of a sidewalk and high reflectance paint or water-retentive pavement for the reduction of surface temperature on the roadway. Reduction of solar radiation gain to the sidewalk pavement surface depends on the location and area of the street tree shadows, which are likely to occur on the northern sidewalk of an east–west road rather than an eastern (or a western) sidewalk of a north–south road. Moreover, the area of the shadow is proportional to the square of the width of tree crown (the radius) and inversely proportional to the distance between trees. Thus, it is necessary to prioritize these considerations based on the road orientation and time when the pedestrian use of sidewalk is the highest.

高日射反射率塗料の性能に関する研究:その９ 色相の違いによる耐候性試験と試験後の日射反射率

高日射反射率塗料の性能に関する研究:その９ 色相の違いによる耐候性試験と試験後の日射反射率

Evaluation of the Energy-Saving Performance of Heat-Resistant Paint

We developed an empirical quantitative evaluation of the energy-saving performance of heat-resistant paint in winter. Specifically, heat-resistant paint and conventional wall paint were applied to steel boxes placed in a room kept at constant temperature and humidity, after which heat sources were placed in the boxes and the energy-saving performance of each type of paint was evaluated from the change in temperature at the box walls and inside the boxes. The experimental results show that the heat-resistant paint reduced the amount of heat escaping through the walls, and it can thus be expected to reduce heat loss. Furthermore, in the case of the heat-resistant paint, the amount of heat passing through the walls was 16% less than that in the case of the conventional paint. The conduction heat flux for the box with ceramic insulating paint was less than that for other boxes. It is thus thought that the thermal resistance of the ceramic insulation paint is higher than that of the other paints. We estimated the thermal resistance of each paint and found that thermal resistance of ceramic insulating paint was 12.4 times that of conventional energy-saving paint and twice that of high-reflectance paint.

街路形態に応じたヒートアイランド対策技術の適材適所の導入検討に関する研究

Abstract In this study, we analyzed the effects of introducing urban heat island measure technologies in a typical street canyon model to aid the selection of a suitable technology. It is appropriate to use street trees for improving the thermal environment of a sidewalk and high reflectance paint or water-retentive pavement for the reduction of surface temperature on the roadway. Reduction of solar radiation gain to the sidewalk pavement surface depends on the location and area of the street tree shadows, which are likely to occur on the northern sidewalk of an east–west road rather than an eastern (or a western) sidewalk of a north–south road. Moreover, the area of the shadow is proportional to the square of the width of tree crown (the radius) and inversely proportional to the distance between trees. Thus, it is necessary to prioritize these considerations based on the road orientation and time when the pedestrian use of sidewalk is the highest.

Effect of Pigment Kinds on the Solar Heat Reflection Characteristics of Paint Film in Visible and Near-Infrared Ray Area

In recent years, the global warming has been recognized as a serious problem throughout the world. In Japan, various global warming control technologies for slowing the global warming are being applied and verified. The high reflectance surface for structures has got a great deal of public attention as a promising technology that mitigates the heat island phenomenon which is a cause of the global warming. It is considered that the heat island phenomenon is generated by the temperature rise due to the heat release from the buildings which have a high heat absorptance and are warmed by the solar radiation during the daytime. Applying with solar heat high reflectance paint to the exterior surfaces of urban structures would suppress the increase in temperature, and make possible mitigating of the urban heat island. Solar heat high reflectance paint is composed of various raw materials to enhance the reflection in visible and near-infrared ray. This paper describes solar heat reflectance characteristics of the paint film by varying thickness of film, formulation of paint (pigments by binder mass ratio ; P/B) and kinds of pigments which are uesd for colorling structures in white, black, blue, red, and yellow. The conclusions obtained from this study are as follows : 1) With the increase in P/B, solar reflectance of paint films used organic pigments are devided into two groups. One is not influenced with the increase of P/B and the other is increased with the increase of P/B. The solar transmittance of paint films with most organic pigments is decreases with the increase of P/B. The solar reflectance and the solar transmittance of paint films with inorganic pigments are not influenced with the increase of P/B. 2) The solar reflectance is not influenced by the thickness of paint film and the solar transmittance decreases with the increase of thickness of paint film.

Solar Reflectance of Solar Heat High Reflectance Paint Considering the Solar Transmittance and Reflectance at the Under Layer

It is considered that the heat island phenomenon is generated by temperature rise due to heat release from urban structures which have a high heat absorptance and are warmed by solar radiation during the daytime. Applying solar heat high reflectance paint to the exterior surfaces of urban structures would suppress the increase in temperature, and make it possible to mitigate the heat island phenomenon. This paper describes the influence of solar reflectance and transmittance characteristics of top coat with the change of film thickness and the reflectance characteristic of the under coat on the solar reflectance of paint system, while aiming to establish a design method of solar heat high reflectance paint system. The conclusions obtained from this study are as follows : (1) It has a linear relation between log T that is indicated in a logarithm of film thickness T(μm) and solar transmittance τe1 (%). (2) It has been confirmed that the solar reflectance of the paint system is influenced by the solar reflectance of the under coat. (3) It is possible to show the solar reflectance of the paint system as the sum of total solar reflectance (ρe1) of the top coat and solar reflectance (ρe2) which is transmitted by solar radiation considering the reflection on the surface of the under coat.

高反射率塗料の性能に関する研究 その２ モデル試験棟を用いた温度測定

高反射率塗料の性能に関する研究 その２ モデル試験棟を用いた温度測定

The Use of Visible Light Models for the Study of Radiant Heat Transfer in Furnaces

Apparatus was developed for the study of radiant heat transfer in furnaces by means of models using visible light. Flame radiation was simulated by an array of miniature lamps. Strips coated with a high reflectance paint were used to represent partial wall reflection. Measurements were made with an integrating-sphere light meter. Tests with models of a gas-fired furnace and a pulverized-coal-fired furnace showed the usefulness of the models in the study of such variables as flame position, furnace geometry, and the reduction of heat transfer by ash and slag deposits.