Rennes, a climate-smart city? - Using IoT to monitor heat islands

Monitoring climatic conditions has become a major contemporary challenge on various scales. On a global scale, climate change is the subject of numerous studies, regularly summarized by the IPCC . On a regional scale, the impacts of certain processes, such as deforestation, or risks such as flooding or drought, are also the subject of much concern. On a local scale, in cities, global climate change is amplified by the warming produced locally by the urban heat island (UHI) phenomenon.

The smart city is also faced with a number of challenges: optimizing resource consumption (water, energy), providing users with access to information (transport, parking, etc.), ensuring day-to-day well-being (environment, land-use planning, safety) and anticipating change (climate, lifestyle and work patterns, etc.). Observation of the urban climate has thus become essential, and has grown considerably in recent decades. The rapid growth of cities in terms of population has led to an increase in urban activities and the creation of heat islands (ICU) .

Although urban overheating has been known for a long time, studies on urban heat islands have developed over the last few decades: in France, the 2003 heat wave, pollution alerts and the need to implement PCAET (territorial climate-air-energy plans) have led many metropolises to set up monitoring programs in partnership with research teams. Indeed, fine-scale climate monitoring requires specific protocols that many local authorities do not master, so it is logical that the first experiments were carried out in university towns where specialized teams on these issues were present (Toulouse, Dijon, Paris and Rennes, among others).

In Rennes, monitoring began in 2003 with the first network of automatic stations: the Rennes Urban Network (RUN). As of 2019, the advent of connected solutions and the falling cost of sensors have led to an overhaul of the observation system, now based on Internet and LoraWan technologies. This article describes the implementation of this unique system in France, its history, principles and practical implications for real-time monitoring of the UHI.