DigiAudit: Automated real-time energy management of buildings
Soaring energy prices in 2021 are caused by a combination of factors resulting with a mismatch between supply and demand side. The owner of the building has few opportunities to produce energy, but many opportunities to monitor and, if necessary, manage consumption. One of the first steps is to find out where and how much energy is being used. For a single building level, this is a relatively simple task. For building owners with larger building portfolio, who have to manage dozens or hundreds of buildings, it is a rather complex and time-consuming task. DigiAudit project has 45 pilot buildings from Tallinn University of Technology, city of Tartu and city of Tallinn. The current conventional method (analysis of energy bills) would be a time-consuming and costly task and should be repeated monthly and yearly to provide an up-to-date overview.
With digital real-time energy management, it is possible to create an initial overview of a building portfolio in minutes. With the permission of the building owner, data of the electricity use can be obtained through Estfeed for all buildings with electricity connection. Larger district heating companies also enable the exchange of the heat energy use (for example, Utilitas). If we add the data of the building from the Register of Buildings (building type and heated area) and the data of the outdoor temperature, we have all necessary preconditions to create an automated Energy Performance Certificate (EPC) that is renewed in real time.
The energy use of the buildings of Tallinn University of Technology analyzed within the framework of the DigiAudit project shows that the picture is quite mixed for the larger building portfolio. The full scale of energy labels (A → H) is represented. 35 buildings with a total annual energy cost of ~ 2 million euros were analyzed.
~ 10% of the buildings are in the first two classes of the energy label scale (A and B) and ~ 50% of the buildings are in the last two classes of the energy label scale G and H. However, the overview based on the main meter readings does not give the perception that causes high or low energy consumption. One of the buildings in Class A is the new Ehituse Mäemaja, which was opened in 2021, and the other building in Class A is a building, which is no longer in active use.
For more detailed analysis, it is also necessary to look at sub-meter data. For example, the Energy Performance Certificate of the building of School of Business and Governance based on the main energy meters is G. If energy consumers which are not taken into account in EPC calculations (servers, hot kitchens, outdoor lighting, etc.) are deducted from the total consumption, the energy label class is F. An improvement by one energy label class may not seem much but at end of the energy label scale, the class differences are significantly larger than at the beginning of the scale. If, for example, the building was originally in class D, deducting the same amount of consumption of servers, catering and outdoor lighting would take the building to class A.
Preliminary results of DigiAudit show that real-time digital energy management is necessary to get an overview of the current situation and to plan energy saving activities. The technical capacity for automated real-time performance analysis of buildings is now available.
The project is funded by the European Regional Development Fund and the Estonian Ministry of Education and Research.