With temperatures reaching 40 degrees or more on hot days in cities, municipalities are always looking for ways to cool. A team of researchers led by the Spaniard José Sánchez has now considered how people on so-called urban heat islands (UHI) can be given cooling. This resulted in the concept of an energy self-sufficient, self-cooling bus station. A pilot project is to be developed in the Spanish city of Seville in 2024.
“This study aims to design a self-sufficient bus stop that provides thermal comfort to residents in hot and dry climates. Self-sufficiency will be achieved through the integration of falling film radiant technology and radiant surface cooling systems,” says the team of scientists from the University of Seville around Sánchez. In a study, a prototype bus stop was converted into a fully sensorised climate chamber. “It’s not like an air conditioner that produces cold air, but the structure of the bus stop exudes freshness, like refrigerators do. Although it consists of more elements, it is cheaper to manufacture than conventional bus shelters.
The bus stop works like this: sensors detect when a person is at the bus stop and activate the pumping system. This draws water from the tank in the floor and circulates it, bringing the temperature of the bus stop down to a comfortable 20 to 24 degrees Celsius. Cool air is released through small holes. The cooling process takes 10 to 20 minutes, after which the water flows back into the container. At night, the water runs over the roof of the station to cool off.
Cooling effect in 10 to 20 minutes
The self-sufficiency of the bus stop in energy is achieved through the integration of falling film radiation technology and radiation surface cooling systems. On the one hand, some results are obtained to obtain the convective and radiant heat flux under different operating conditions. The characterization shows that 60% of the total heat flow is due to the radiation emitted by the installed modules. At the same time, thermal images allow verification of the correct performance of the prototype. It is also noted that cooling is achieved in just 20 minutes.
The temperature reached by the modules is shown in the figure above. The water in the radiant panels takes 20 minutes to cool down. The cooling provided by the modules is uniform and causes the temperature of the examined area to drop from 25.5°C to 17.9°C.
The study was funded by the projects “LIFEWATERCOOL – Water efficient systemic approach to climate change adaptation in urban areas” of the European Commission “CONSTANCY – Resilient urbanization methods and natural conditioning using innovative nature-based solutions and cultural heritage to revitalize street life” of the Spanish Ministry for science and innovation. The European Regional Development Fund (ERDF) also helped finance it.