The planning tool for district energy systems

Documentation of calculation models

On this page you find a brief documentation of the models used in nPro, which you can use to describe them in reports or other documents. The descriptions used on this documentation page can therefore be used either word for word or in modified form for your own purposes without reference or further consent.

Simulation of demand profiles

Top-down methods are used to generate demand profiles for space heating and air conditioning. A simplified physical model based on degree day hours is used to generate an annual demand profile based on the total annual demand. The simulation method has been validated for a large number of building types with measurement data from buildings in several German cities. Simplified models based on standard load profiles are used for process cooling, domestic hot water, e-mobility and electricity (plug-loads). The seasonality of the demand profiles over the year is taken into account.
See also: Demand profile calculation: Validation for different building types

Photovoltaic generation profiles

The yield calculation of photovoltaic systems is based on the documentation of the validated commercial tool PVsyst and the implemented model equations for irradiation calculation from the publication "Duffie, John A., and William A. Beckman: Solar Thermal Power Systems. In: Solar Engineering of Thermal Processes, Fourth Edition, John Wiley & Sons, Inc., Hoboken, USA, 2013".
See also: Photovoltaics: Calculation and validation

Solar thermal generation profiles

The calculation of the time-resolved yield profile for solar thermal collectors is based on DIN EN 12975-2. Yield profiles were validated for a variety of different locations and orientations using the generation profiles of the ScenoCalc tool from the SP Technical Research Institute of Sweden.
See also: Solar thermal: Calculation and validation

Wind power generation profiles

The yield calculation of wind turbines is based on power curves of real wind turbines. The wind speed at hub height is calculated according to Hellmann's power law from weather data and hub height.
See also: Wind power calculation

Design and dimensioning optimization

The calculation models for system design and operational simulation are based on proven mathematical optimization models that are widely used in research, as described, for example, in [1]. These optimization models take into account energy balances in hourly resolution for a typical design year as well as simplified component models with constant and time-variable efficiencies. The design calculation is based on an ideal system operation, which assumes, for example, a perfect foresight of future demands.
See also: Optimization model for design calculation

Calculation of ground temperatures

The calculation of ground temperatures is based on simplified physical calculation models, which have been calibrated and validated with the help of measurement data.

Economic calculation

The economic efficiency is calculated using the net present value method and the calculation approaches set out in the German guideline VDI 2067. In addition to operating costs, annualized investment costs are also included in the calculation.

Weather data

The weather data used are based on data sets from various meteorological organizations. An overview of the used data sets can be found in the publication "Lawrie, Linda K, Drury B Crawley. 2019. Development of Global Typical Meteorological Years (TMYx)."

Coefficient of performance (COP) for heat pumps

The COPs of heat pumps calculated with manufacturer data are based on measurement series of the certification organization Keymark according to standard EN 14825. Due to numerical interpolation, deviations between measured data and calculated COPs cannot be excluded.


  1. Design optimization of multi-energy systems using mixed-integer linear programming: Which model complexity and level of detail is sufficient? M. Wirtz, M. Hahn, T. Schreiber, D. Müller. Energy Conversion and Management, 240, 114249, 2021.
  2. Climate.OneBuilding.Org
  3. PVsyst-Tool

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