Cool with hotspots

Researchers at Jacobs University have generated a high-precision 3D model of Bremen’s city center using a so-called ThermalMapper. This particular mapping process was initially developed by Jacobs University scientists to thermographically model indoor environments in 3D. For the first time it has now been used to analyze heat distribution and heat flow in a large outdoor setting. ThermalMapper can identify thermal bridges in building which are responsible for heat loss. Mapping results can then be used to improve insulation and increase the energy efficiency of buildings.

February 3, 2012

Running heating systems and air-conditioners in insufficiently insulated buildings can lead to thermal loss and a large waste of energy. According to a recent EU report the 30 % of energy loss could be avoided by improving insulation in residential homes and offices.

However, it is often quite tricky to find areas of thermal loss and act upon the findings. This is where the ThermalMapper designed by Jacobs University comes into play. It generates precise digital models of heat distribution and heat flow by combining high-resolution scans of the surroundings with thermographic measurements of the environment to generate a highly differentiated thermographic 3D model.

A mobile robot captures the surroundings using a three-dimensional laser scanner. The robot  can scan interior spaces, the outside of buildings and whole streets. ThermalMapper simultaneously measures heat distribution within the analyzed area. Algorithms developed by Jacobs University researchers then calculate a thermographic 3D model almost in real time.

„The generated information enables us to create virtual tours and visualizations, which can tell us if thermal bridges exist and give us an idea about their size and form. All relevant model parameters are known, which are in turn necessary for a thermal simulation and to automatically calculate thermal transmission coefficients,” explains Andreas Nüchter, Professor of Computer Science at Jacobs University and head of the automation group, currently working on the ThermalMapper project.

Cold weather makes for ideal experiment conditions

Prof. Nüchter and his research team took advantage of the cold and dry weather of the last days, to generate a virtual 3D model of heat distribution in Bremen’s city center. “We have been taking measurements at night giving our little robot Irma3D a free run across the Rathausplatz, which is too crowded in the daytime,” says Dorit Borrmann, a PhD student at Jacobs University who is working on combining methods of 3D laser scanning and thermography.

“Moreover, such measurements in the outdoors are much more precise at nighttime. Even diffused daylight and cloudy skies could cause exterior surfaces to heat up and masquerade heat loss from the interior. The difference in temperature between the exterior and interior should be 15° Celsius or more. Hence the cold weather has been ideal to conduct our experiment,” she adds.

The result of the experiment is a two-minute virtual tour of Bremen’s market square and the Domshof (please see video below). Blue color means temperatures starting from  -5°C, red stands for temperatures of +10°C and more.

“It is no surprise that most heat emanates from big sized windows of the churches, the town hall and other historic buildings; otherwise Bremen’s city center remains rather ‘cool’. The setting for the experiment was ideal to demonstrate the ThermalMapper's high degree of differentiation in outside surroundings,” says Andreas Nüchter about the results.

With a focus on applications in geodesy, architecture and building management, Prof. Nüchter and his researchers have been working on the principles of robotic three-dimensional mapping. They are examining automated processes of calibration and visualizations as well as planning algorithms to determine ideal recording positions to find out where significant and most informative recordings can be made.

“To increase ThermalMapper’s efficiency in future we are planning to take our next experiments to the air. Using flying robots we could measure rooftops much more precisely than from the ground. These are the areas where we see a lot of heat loss,” says Nüchter.