Fraunhofer-GesellschaftWeb special of the cover story of Fraunhofer magazine 1.2021
Climate stress
Heavy rain, storms, high temperatures: How we are making our towns and cities more resilient
© Fraunhofer/Heinz Heiss
Under the stress of climate change
How will room climates develop through to the year 2100?
If we want to prevent heat stress for city dwellers, making streets of houses and squares prettier by urban greening is not enough. Another important aspect is the room climate inside buildings. A multidisciplinary team involving 27 partners from Europe and Egypt have been working on the “Climate for Culture” project, funded by the EU and coordinated by Fraunhofer IBP, to deliver a solid basis for assessing this issue.
“We have coupled the hygrothermal building simulation model WUFI®Plus to climate models,” explains Dr. Johanna Leissner, the Fraunhofer-Gesellschaft representative in the research consortium. “This will allow us to simulate the room climate inside buildings through to the year 2100 and to analyze how climate change, but structural measures such as new windows, doors or shading too, is affecting the indoor climate and how much them out of the climate models. To achieve this, they needed to calculate the climate parameters with a resolution of ten by ten kilometers throughout Europe up to the year 2100. In fact, for two different scenarios since the true greenhouse gas emissions in the future can only be estimated. “There was a huge volume of data to process before we could feed it into the building simulation,” recalls Leissner. The research team validated the parameters they had identified using climate data from the past. Although the project focused on historical buildings and cultural heritage, the simulation does lend itself to all kinds of buildings
Hurricanes and strong winds
Although less sensational than droughts, heavy rain and rising temperatures, hurricanes and strong winds are other relevant effects of climate change. The aim here is to systematically break through wind swaths without reducing the positive effects of ventilation used for cooling during the summer months. “Besides topography, the way the wind works its way through cities is also largely down to the man-made obstacles — in other words the buildings,” says Matthias Winkler from Fraunhofer IBP. “Meaning, there are only a few options open to us for buffering wind swaths because we cannot alter the existing building structure that much.” One such possibility is not to close gaps between buildings flush with other houses, but instead to erect the new building slightly higher. Another one is trees, shrubbery or works of art that are positioned at the start of a wind swath and break through the unimpeded wind passage.
The urban climate model PALM-4U can be used to pinpoint the streets of houses in a city down which the wind whistles the strongest, and analyze the effects of such measures in especially windy corners in certain cities. The model is being developed in the “Urban Climat Under Change” project by a research consortium, also belonging to Fraunhofer IBP. “PALM-4U will help us map temperature profiles up to building level and also to simulate wind swaths,” explains Winkler.
The city of Berlin has already been simulated: We will be able to use this model in the future to reveal wind hotspots and examine approaches to counteract their effect. Will they have the desired effect? The researchers are also creating a model for Stuttgart, which they expect to be ready by the end of 2021. In the subproject ProPolis, the Fraunhofer researchers want to put the urban climate model into practice and refine it so it meets the needs of municipalities and other users from practice. This includes developing a graphical user interface and training concepts. After all, the more practical and easier to use the model is, the more likely municipalities, cities and local communities are to take it on board. In the UCare4Citizen project, researchers are preparing the simulation results so that we can experience the complex information by wearing augmented reality glasses. In the KERES project, researchers are investigating the effects of extreme storms on cultural assets, focusing on both historical buildings and garden areas in the process.
The technologies themselves? They are not the problem!
A challenge running through most projects for adapting to climate change like a common thread: For the most part, the technologies are in place. “The difficulty lies in getting them implemented,” says Dr. Susanne Bieker from Fraunhofer ISI. We would often hear the argument that the measures are too expensive. For Bieker, though, this does not hold: “There are numerous sources of funding. The ‘Water in the city of the future’ initiative, for example, covers up to 100 percent of the costs in some cases. Many cities also offer a ‘Green roofs program.’ Habits combined with ignorance and the will to create myths often stops the funding getting to where it needs to be,” Bieker knows only too well. As one such myth would have it: Photovoltaics and green roofs can’t be combined. Complete nonsense, in Bieker’s opinion. In fact, the exact opposite is true: Green roofs cool the photovoltaic elements from below, improving their performance by four to five percent.
An important lever for climate-resilient urban planning, therefore, is allaying the fears of the decision makers, communicating more information about the individual measures and unraveling the host of possible remedies. Researchers at Fraunhofer ISI are pursuing this goal in a feasibility study in Bochum. The team approached a large housing association that looks after various districts. “If we understand exactly what’s needed here, we have wholly different possibilities for a scale-up than through private individuals,” says Bieker.
The researchers focused on a district with around 50 existing buildings which now however — just like many districts in the Ruhr region — is facing densification. In other words: In large gardens or in gaps between buildings, new houses are to be erected and existing buildings are to be made higher. But because, as a result, open spaces can disappear, we have to keep an eye on the hydrological cycles. In the feasibility study, the research team examined which measures would lend themselves to densification initiatives and under which framework conditions.
200 square meters of green roof can save 500 euros
To give the partners a chance to better estimate the costs involved, the researchers broke the figures down. “Our example calculation showed: In Bochum, just one green roof of 200 square meters is able to save 450 to 500 euros per year,” says Bieker. “Then there are the unquantifiable advantages such as improved weather protection for the facade and the cooling effect for the environment and interior spaces.”
Here’s what the project brought to light: Major synergies exist between the housing sector and the municipalities, the interests are much more similar than we expected on many levels. The municipalities, for example, offered to feed surplus rainwater from the district to a cased stream — which would then in turn carry enough water for it to be uncovered. “Getting all stakeholders around one table often bears a lot of fruit,” says Bieker summing up.
Adapting to climate change — a global issue
Of course, the effects of climate change are not limited to just Europe — and neither are the Fraunhofer approaches to tackling climate change. Cities such as Kochi in India and Saltillo in Mexico are being severely impacted by climate change. In the project called “Morgenstadt Global Smart Cities Initiative”, researchers from Fraunhofer IAO, Fraunhofer IGB, Fraunhofer ISI and Fraunhofer IBP are therefore devising precise courses of action. The project is being financed by the International Climate Protection Initiative (IKI) of the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU). “We are making use of the experience we gained from the Morgenstadt network with 40 partners from industry, research and the municipalities, as well as the Morgenstadt tools,” says Dr. Markus Schwegler. The work involves three essential steps: The first one is to analyze the interactions within the city. What are the problems? Second, the researchers will be discussing co-creation — working with all partners and associates, they will work out and prioritize the first project ideas. And in the third and final step, they will set the ideas in motion.
Kochi, one of the most important ports on India’s west coast with a population of 600,000, has first and foremost water problems. “The recent monsoons caused severe flooding, claiming many lives and disrupting public life; around half of the airports had to close,” explains Dr. Marius Mohr from Fraunhofer IGB. For the remaining months of the year, though, the city faces serious water shortages. “The solutions to these two problems are intertwined,” says Mohr. “If we save some of the water the monsoon season brings, it will be available in the dry spells. “Roof gardens would appear to be a good solution for Kochi. Another efficient way of discharging the bodies of water would be to use the open channels that were created during the colonization period but are now clogged with garbage. “We want to experiment with the approach on a small district — our hope is that the city will embrace the idea and roll it out in other districts too,” says Mohr. Turning to Saltillo, Mexico — the second city lab. Defined by the automotive industry, this prosperous city lies in the Chihuahuan desert and is by nature very arid. Due to the effects of climate change, however, water scarcity is a growing problem. Water efficiency is therefore becoming an important subject, especially for industry. Together with partners and associates, the researchers will decide in summer 2021 which projects are to be realized. “Research projects are often halted when recommended actions are devised for the customer. I think it’s wonderful that in the context of the city labs, we can implement tangible approaches in the form of pilot projects,” enthuses Jose Antonio Ordonez, scientist at Fraunhofer ISI and project manager. “We can then see whether the approach is reaping the desired successes, sort out the teething troubles and then replicate it or scale it up.” And by doing so, gradually better counteract the effects of climate change in the cities.