Planning tool for buildings & districts

Energy simulation of districts

The planning of district energy systems is complex and multi-layered due to the large number of technical, economic and political dependencies. New planning tools make it possible to support the planning process in different project phases.

Planning processes become more complex

In the future, renewable energy and heat sources must be used to supply buildings and districts with low-emission energy. Unlike conventional technologies such as natural gas or oil, renewable heat sources are not available to the same extent all year round. Photovoltaics or solar thermal show strong intra-day fluctuations and offer a strongly seasonal heat supply. This has implications for the planning process of energy systems, as the temporal profile of energy sources and energy demands has a strong influence on the supply.

Planning based on a typical design year

When simulating and optimizing energy systems for buildings and districts, typical design years are often used as a basis. These reference years are based on weather data that represent a typical weather year. The problem is that these test reference years are often based on the average values of past decades. However, due to climatic changes, past average years are no longer representative for the future. Summers in particular are often characterized by prolonged periods of heat with very high outdoor temperatures. Winters are also statistically milder than they were a few decades ago. As a result, the design temperatures for heating systems valid at that time (of -10 °C to -18 °C in Germany) are often chosen too low, which leads to an overdimensioning of heating systems.

Which time resolution is useful for energy simulations?

In simulation tools, very different time resolutions are considered. In systems with thermal energy flows, an hourly resolution is often used. This is because heat demand profiles and weather time series are often only available in hourly resolution. For electrical systems, a 15-minute resolution is also common. Generally, the more sluggish the system, the lower the required time resolutions. In addition, for smaller systems for individual buildings, for example, it must be noted that these have very pronounced demand peaks and therefore hourly resolution is not sufficient. At the neighborhood level, however, demand peaks are averaged out and a continuous demand profile results, which can be represented by standard load profiles, for example, and for which an hourly resolution of the calculation is then also sufficiently accurate.

In the nPro tool, all calculations are performed with an hourly resolution. For building and district simulations of thermal supply systems, this time resolution has proven to be a good trade-off between accuracy and computation time.

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