Article by Eurecat
Building Energy Demand Forecast Methodology (EDCE)
For the optimal sizing and determination of the HVAC system in a building, the precise calculation of the energy demand is an essential task, especially in cases of geothermal installations, due to the fact that the effort and the costs of any afterwards modification are high. Thus, the initial calculation and dimensioning of the installation are crucial to guarantee that the expected system’s performance is achieved.
Nowadays, the dimensioning of a building’s installation can be made in 3 different ways: i) The use of empirical methods based on energy demand estimations, ii) use of real operation energy consumption profiles (acquired by the building’s SCADA system), or iii) use of detailed building energy simulations to accurately characterize the energy requirement of the building.
In the first case, the use of estimations and empirical calculations presents a high risk of oversizing the installation or not fulfilling the energy requirements, resulting in excessive energy use and increased investment costs. On the other hand, the use of energy demand profiles acquired via the SCADA systems can lead to very precise sizing of the heating and cooling equipment. Nevertheless, this method could be used only in cases of retrofitting of buildings, requiring a monitoring campaign of several months in order to accurately characterize the demand patterns. Finally, the less frequent implemented method is based on detailed building energy simulations, using software tools such as EnergyPlus or TRNSYS. This method, although it provides highly accurate results, requires an initial purchase of the software and training the user. Finally, entering building information into the software can be time-consuming, similar to the computational effort of calculations.
In this line of work, Eurecat Centre Tecnològic de Catalunya has developed a methodology, called EDCE (Energy Demand Calculation Engine), which, based on energy analysis and thermal load simulations, can calculate precisely and quickly (in seconds) the annual energy demand of a given building, according to its architectural characteristics (e.g. volume, useful area, orientation, walls thermal transmittance, etc.), climatic conditions (i.e. solar radiation, temperature) and operation profiles. The EDCE method is based on a large sample of building energy simulations combined with mathematical models that describe the correlations between the characteristics of the buildings and their energy requirements. It allows the accurate calculation of the energy behavior of a building under specific climatic and operating conditions.
The EDCE output consists of four hourly-based vectors, including the energy profiles of heating, cooling, domestic hot water (DHW) and electricity for a prediction horizon of 1 year with an hourly resolution.
EDCE presents the same accuracy and precision advantages of the simulation methods, but significantly reduces the configuration and computational effort required to calculate the results. In the proposed method, the calculation is performed using an already trained mathematical model (based on hundreds of thousands of simulations made in Energy Plus), to obtain the annual energy demands of any given residential building with an hourly-based resolution. On the other hand, the proposed tool can be integrated in a GeoBIM environment (CityGML extension), using the standard open BIM protocols (e.g. IFC4), in order to obtain geographical information system (GIS) data.
The following figure presents the structure of the energy demand calculation engine, its proposed integration within the Geofit’s GeoBIM platform.