Authors: Prof. Dr. Philipp Weihs, Prof. Dr. Josef Eitzinger, Ing. Wolfgang Laube
Basic concept of the building block
The following experiment, which can be carried out on various homogeneous paved surfaces, demonstrates the influence of surface reflection (Albedo) on ground surface temperature. Students should be able to understand the differences between the radiation balances of light and dark paved surfaces, as well as be able to measure and quantify this.
Description of the building block
This building block handles the very topical issue of albedo’s influence on heat generation in cities and metropolitan areas. Multiple recently published studies show that changes in the surface albedo in urban structures can lead to local air temperature changes of 1 to 2 degrees. Over-heating of cities in summer leads to an increased energy consumption due to the increased use of air conditioners in buildings and vehicles. Appropriate changes to surface area design can reduce the heat strain and with it the use of non-renewable energy resources.
The measurements consider the spatial and temporal dynamic of energy flows in our environment and can be conducted over a one-day timespan (cloudless conditions necessary).
The temporal variability of the energy balance components, as well as the radiation balance, is examined with the help of measurements taken with a two-component net radiometer (measurement of shortwave radiation upward and downward -Albedo- and measurement of long wave radiation upward and downward).
The two-component net radiometer is mounted on a tripod and positioned alternatingly (every 10 minutes) over a lighter and a darker area. The measured data is visualized using a Campbell datalogger and related software.
The visualized data makes the differences between the short wave and long wave radiation balances over the two surfaces clear. If the natural surroundings do not provide sufficient albedo differences, two specially prepared Styrofoam surfaces painted black and white, simulating strong and weak reflecting surfaces, can be used instead.
The surfaces of the BOKU trial site in Groß-Enzersdorf or at the Exner building provide good trial areas. If circumstances demand, reference surfaces such as the Styrofoam surfaces or a painted surface can be used to artificially measure the albedo.
The building block is divided into four steps:
Step 1: Directions to conducting the experiment
Step 2: Setting-up the experiment
Step 3: Conducting experiment
Step 4: Analyzing and interpreting the data