Enthusiasm of public-private cooperation changes heat reduction measures in the city!
-- “Fractal shade” and “heat ray retroreflective film”
In the big city Yokohama, the annual average temperature has been rising for a long time partly because of the heat island effect. That is increasingly affecting society. Every year, for instance, several hundreds of citizens suffer heatstroke and are rushed to hospitals. The Yokohama City Environmental Science Research Institute has carried out a measurement survey in cooperation with private businesses on two new technologies as promising measures against heat (fractal shade and heat ray retroreflective film) and confirmed the effectiveness of both technologies. This survey result has encouraged the introduction of fractal shades into two day nurseries in the city. The shades are well received by the children and their parents. We interviewed Koji Seki, Koji Odagiri and Mitsuya Ishihara at the research institute.
To protect citizens from the risk of heatstroke
How did you come to work with private businesses in the measurement survey of two new technologies?
According to the “2016 Heat Island Monitoring Report” by the Japan Meteorological Agency, the annual average temperature of Yokohama City has risen by 2.8°C per 100 years. The average rise is almost double that of 15 areas where the impact by urbanization seems to be relatively small (1.5°C ). There seems to be the effect of heat islands in addition to the impact of global warming. Our institute has been measuring the city’s temperatures continuously since 2002. We have found that the average temperature in July and August is high in the eastern Yokohama and low in the west area having a lot of greenery. The number of hot summer days (a maximum temperature of 30°C or above) is the largest in the northeast area. The number of days with a sweltering night at 25°C or above is the largest in the east area. The areas with high temperature differs between daytime and night.
In Yokohama City, several hundred people are rushed into hospitals for heatstroke every year. The number was 734 between May and September in 2017. Our institute studied the relationship between the summer heat and the number of heatstroke patients raced to hospitals from June to September in 2015. As a result, we have found that the higher the wet-bulb globe temperature (WBGT) rises, the larger the number of people raced to hospitals per hour becomes. The average temperature is expected to keep rising and there is concern about the spread of adverse effect to human health. As the 2020 Summer Olympics and Paralympics in Tokyo are approaching, we need to develop heat reduction measures, considering the introduction of new technologies.
To officially introduce new technology, it is often necessary to conduct a measurement survey to estimate the quantitative effects and the cost effectiveness. The survey sometimes costs a lot of money. As the city is on a tight budget, we have decided to work with private businesses hoping to save such cost.
Sunlight filtered by the shade is like one coming through leaves. Children love it.
Fractal shade is an unfamiliar word. How different is it from the common shade made of a piece of cloth? How was the result of the measurement survey?
A fractal shade is made of small leave-shaped pieces arranged in a three-dimensional pattern. Fractal is a geometric concept that a curve or pattern consists of smaller curves or patterns in exactly the same shape. Complicated shapes found in the nature, including trees, can be made approximately using the concept. This concept of fractal is applied to a fractal shade. This technology is developed and patented by Professor Satoshi Sakai, Graduate School of Human and Environmental Studies, Kyoto University. Two Japanese manufacturers (LOSFEE Co., Ltd. and Sekisui Heim Supply Co., Ltd.) are licensed to manufacture and market the shades. A fractal shade has a high heat dissipation effect and the temperature of the shade itself does not rise easily. If the temperature of a shade is kept low, heat radiation will be also kept low. Because of this feature, a fractal shade is said to have higher heat prevention than a shade made of a piece of cloth.
From July 20 to 24, 2016, we conducted a measurement survey installing a fractal shade (9 m wide x 5.4 m deep x 2.8 m high) in the event square of the Yokohama Red Brick Warehouse with the cooperation of LOSFEE Co., Ltd. and Yokohama Akarenga Co., Ltd. At noon on July 20, the ground surface temperature under the shade measured 33°C . It was 9°C lower than the temperature in the sun, which was 42°C. Hot air was rising from the ground in the sun but it was not felt under the shade. The temperature 1.5 m from the ground under the shade was 0.6°C lower than in the sun on average.
From August 8 to 16 in the same year, we also conducted a measurement survey in the storage warehouse of “Hamakko-Doshi The Water” (Yokohama City official bottled water) sold by Yokohama City Waterworks Bureau. We placed two fractal shades (10 m x 6 m on the west side and 8 m x 5 m on the east side) on the roof of the warehouse and we measured the roof surface temperatures under the shades and other areas. At 13:30 on August 9, the surface temperature was 55°C under the shade on the west side of the roof and 65°C in an area without a shade. The shade lowered the temperature by 10°C. On the east side, the shade decreased the temperature by 7°C . We also found that the shade even had an effect of lowering the temperature in the warehouse by 1.7°C on average.
Why did you conduct the measurement survey in the Yokohama Red Brick Warehouse?
There are two reasons for choosing the Yokohama Red Brick Warehouse. One reason is that we hope to draw citizens’ interest in our heat reduction measures as many tourists and citizens visit the Yokohama Red Brick Warehouse. The other reason is to save cost of the measurement survey. LOSFEE designing and installing fractal shades agreed to support the measurement survey, part of heatstroke prevention measures, and helped us with the installation of the shade. Yokohama Akarenga Company running the Yokohama Red Brick Warehouse appreciated the significance of installation of a shade for heatstroke prevention and let us use the place free of charge. Thanks to their help, the survey cost less than the city government would conduct it for itself. Our approach to save the project cost by cooperating with private businesses was highly regarded and we won an award for a city government employee who made an excellent technological proposal in January 2018.
How did citizens and tourists respond to the fractal shade?
Although the Yokohama Red Brick Warehouse was air-conditioned and it was cool enough inside, many citizens were having a rest under the fractal shade. That impressed me. People may prefer to spend time in outdoor open space if there is a shady spot they can keep cool. During the five days, only several hundreds of people among 3.7 million citizens may have experienced the coolness under the fractal shade. However, those several hundred people looked really comfortable. That suggested the possibility as a heat reduction measure and greatly encouraged me.
The year after the measurement surveys, the fractal shades were installed in two day nurseries in the city. How are they received?
With the survey at the Yokohama Red Brick Warehouse as a trigger, fractal shades were introduced into two day nurseries in Tsuzuki Ward in July 2017. The fractal shade was installed over the large roof balcony on the second floor in both nurseries. Testing result shows that the installed shades have a service life of around 20 years and withstand a wind speed of up to 50 m/sec. We have received a comment saying “The fractal shade is handy. It does not cause great trouble.” If a cloth shade is used, nursery staff often have to remove the shade every time a strong wind is forecast. The shades are well received by children and their parents. For example, there are comments like “Children enjoy playing under the shade. They can see the sky through the shade. It looks as if they are bathing in the sunlight coming through leaves” or “We had children wear a T-shirt to protect from sunburn. Now, they can bathe in swimsuits and they look comfortable.” Yokohama City has 18 Wards. I have heard Tsuzuki Ward have received inquiries from other wards hearing of the reputation of fractal shades in Tsuzuki Ward about how they can introduce them and how effective they are.
Heat ray retroreflective film reflecting light toward the sky and friendly to people outdoors
What is the heat ray retroreflective film examined in a measurement survey like? What effects is the product expected to produce?
A heat shielding film is applied to a window pane to reflect near infrared rays (heat rays) and prevent sunlight from heating the inside of the room. A conventional heat shielding film reflects heat rays coming from diagonally above and sends them diagonally downward. A conventional heat shielding film can reduce the heat indoors but it will increase the heat outdoors with the reflected heat rays.
The heat ray retroreflective film Albeedo made by Dexerials Corporation has a special reflective layer inside and reflects heat rays coming diagonally above straight back in the incoming direction. When the heat ray retroreflective film is applied to the inner side of a window, it blocks heat rays and reduce the heat indoors. In addition, as it sends back heat rays toward the sky, it also reduces heat rays sent toward the ground are reduced. This film makes people indoors comfortable and it is also friendly to people outdoors.
Please tell me the result of a measurement survey conducted at an elementary school.
Yokohama City, Dexerials Corporation and JVC Kenwood Corporation (helping the establishment of sales channels of the heat ray retroreflective film and verification) jointly conducted a measurement survey of heat reduction measures using the heat ray retroreflective film at Yokohama City Kamisueyoshi Elementary School (Tsurumi Ward) from July 21 to August 25, 2017.
We thought that an elementary school would be suitable for observing the heat reduction effect exhibited by the film as an elementary school had a schoolyard. We used three classrooms on the third floor. Each classroom had (1) no heat shielding film, (2) a conventional heat shielding film or (3) the heat ray retroreflective film. We measured the insolation and temperatures in each classroom and the insolation on the schoolyard. The classroom (2) was 37% lower in insolation and 0.5°C less in temperature than the classroom (1). The classroom (3) was 49% lower in insolation and 0.5°C less in temperature than (1). The result showed that applying a film reduced the heat in the classrooms (2) and (3). What made a big difference was the measurement result on the schoolyard. The insolation in the case (2) was 11% more than that of (1). It was apparent that a conventional heat shielding film increases heat rays on the ground by reflecting them. In the case (3), the insolation was 1% lower than (1). That has confirmed that the heat ray retroreflective film also reduces heat rays sent to the ground.
Great business opportunity
Do you think adaptation measures to reduce adverse impacts of climate change will create business opportunities?
I believe that developing new technologies and products to promote adaptation measures will open up business opportunities as it will create new markets. Although it is not businesses based in Yokohama City that develop and manufacture the heat reduction materials key to the new technologies of the fractal shade and the heat ray retroreflective film, the installation works are likely to be subcontracted to businesses in Yokohama City when they are adopted as heat reduction measures. Positive ripple effects on the city economy are expected to result.
Our immediate targets are the 2020 Summer Olympics and Paralympics in Tokyo and the 2019 Rugby World Cup Final in Japan that include Yokohama City as a venue. We are expecting that international events can offer an opportunity to heighten public awareness of climate change concerns and create new businesses. Annual average temperatures have been showing a long-term upward trend and the world is slowly getting hotter and hotter. I know public awareness and business practice cannot change overnight, but world-class events like Olympics, Paralympics and Rugby World Cup Final can trigger a change. We consider the Tokyo Olympics and Paralympics one of the means of driving future adaptation measures not a goal.
What difficulties did you have in these efforts?
The hardest thing was to find a balance to ensure benefit to both of us in the cooperation with private businesses. The purposes differ between public and private organizations in some aspects. In the survey of the fractal shade, the business found it an advantage to be able to promote the product in a popular tourist spot, Yokohama Red Brick Warehouse. We succeeded in creating a win-win situation. Having a chance to advertise the achievements of our efforts like this interview is advantageous to both businesses and us. It drives us to make another effort.
Is there anything you want support by the national or prefectural government? How do you feel about tackling heat reduction measures as the Environmental Science Research Institute?
The practical application of heat reduction technologies (e.g., heat insulation paving, artificial shade and heat shielding window film) incurs huge expenses in many cases and their introduction is not progressing well. To promote the introduction, I think it will be effective if the national or prefectural government gives a subsidy or other support to municipalities and private businesses trying to introduce such technologies.
As to how I felt about our efforts for the measurement survey, I was pleased that the survey at the Yokohama Red Brick Warehouse bore fruit, as it led to the introduction of the fractal shade to day nurseries. For the measurement survey on the heat ray retroreflective film at the elementary school, we had to check the site and have meetings again and again until we finally conduct the survey. Eventually we could obtain sufficient quantitative data and publicize the result. I am glad about that.
We at the research institute will try to select promising technologies from those receiving little attention and stick with providing measurement data to develop and spread the technologies. I hope we can collaborate with the National Institute for Environmental Studies and other similar institutes in the fields we cannot handle alone, for instance, in data analysis of survey results. The issue of heat varies greatly from area to area in Yokohama City and therefore we cannot take across-the-board heat reduction measures. Overcoming the difficulty, we will work hard to develop effective measures.
(Posted on April 18, 2018)
