ruhnau

Overview

Heat pump COP model following Ruhnau et al. (2019).

Purpose and scope:

• Computes coefficient of performance (COP) time series for heat pumps by relating COP to the instantaneous temperature lift between the source (ambient/ground/water) and the sink (space heating or DHW). Source/sink types map to typical supply setpoints and optional temperature gradients.

Method outline:

• Parameterize COP as a quadratic function of the temperature lift ΔT based on coefficients for air/soil/water systems, and adjust via a correction factor to reflect realistic performance (defrosting, auxiliaries).

• Provide parallel COP streams for space heating and DHW if desired.

Typical use:

• Combine with HVAC load time series to estimate electrical demand of HP systems, or evaluate seasonal performance under different setpoints.

Reference:

• Ruhnau, O., Hirth, L., & Praktiknjo, A. (2019). Time series of heat demand and heat pump efficiency for energy system modeling. Energy Policy, 125, 704–715. doi:10.1016/j.enpol.2019.111179

Key facts

• Method key: ruhnau

• Supported types:

  • hp

Requirements

Required keys (specify in objects)

• weather

Optional keys (specify in objects)

• hp_source

• hp_sink

• sink_temperature[C]

• gradient_sink

• water_temperature[C]

• correction_factor

• hp_system

Required data (specify in data)

• weather

Optional data (specify in data)

• hp_system

Outputs

Summary metrics

Key	Description
hp:heating_avg[1]	average heating COP value
hp:heating_min[1]	minimum heating COP value
hp:heating_max[1]	maximum heating COP value
hp:dhw_avg[1]	average DHW COP value
hp:dhw_min[1]	minimum DHW COP value
hp:dhw_max[1]	maximum DHW COP value

Timeseries columns

Column	Description
hp:heating[1]	heating COP time series
hp:dhw[1]	DHW COP time series

Public methods

• generate

    def generate(
      self,
      obj: dict = None,
      data: dict = None,
      results: dict | None = None,
      ts_type: str = Types.HP,
      *,
      weather: pd.DataFrame = None,
      hp_source: str = None,
      hp_sink: str = None,
      temp_sink: float = None,
      gradient_sink: float = None,
      temp_water: float = None,
      correction_factor: float = None,
      hp_system: dict = None,
      cop_coefficients: dict = None,
  ):
      """Generate heat pump COP time series for both heating and DHW.
  
      Args:
          obj (dict, optional): Dictionary with heat pump parameters
          data (dict, optional): Dictionary with input data
          results (dict, optional): Dictionary with results from previously generated time series
          ts_type (str, optional): Time series type to generate
          weather (pd.DataFrame, optional): Weather data with temperatures
          hp_source (str, optional): Heat pump source type ('ASHP', 'GSHP', 'WSHP')
          hp_sink (str, optional): Heat sink type ('floor', 'radiator')
          temp_sink (float, optional): Temperature setting for heating
          gradient_sink (float, optional): Gradient setting for heating
          temp_water (float, optional): Temperature setting for DHW
          correction_factor (float, optional): Efficiency correction factor
          hp_system (dict, optional): System configuration for heat pump
          cop_coefficients (dict, optional): Custom coefficients for COP calculation (a, b, c)
  
      Returns:
          dict: Dictionary with summary statistics and COP time series for both heating and DHW
  
      Raises:
          ValueError: If required parameters are missing or invalid
      """
      # Process inputs
      processed_obj, processed_data = self._process_kwargs(
          obj,
          data,
          weather=weather,
          hp_source=hp_source,
          hp_sink=hp_sink,
          hp_temp=temp_sink,
          gradient_sink=gradient_sink,
          temp_water=temp_water,
          correction_factor=correction_factor,
          cop_coefficients=cop_coefficients,
      )
  
      # Get input data with validation
      processed_obj, processed_data = self._get_input_data(processed_obj, processed_data)
  
      # Calculate heating COP time series
      heating_cop_series = _calculate_heating_cop_series(processed_obj, processed_data)
  
      # Calculate DHW COP time series
      dhw_cop_series = _calculate_dhw_cop_series(processed_obj, processed_data)
  
      return self._format_output(heating_cop_series, dhw_cop_series, processed_data)