Heat Pump

Create Controlled Function

pandaprosumer.create_controlled_heat_pump(prosumer, delta_t_evap_c=15.0, carnot_efficiency=0.5, pinch_c=None, delta_t_hot_default_c=5, max_p_comp_kw=nan, min_p_comp_kw=nan, max_ramp_up_kw_per_s=nan, max_ramp_down_kw_per_s=nan, max_t_cond_out_c=nan, max_cop=nan, cond_fluid=None, evap_fluid=None, mode='carnot', name=None, index=None, in_service=True, level=0, order=0, period=0, **kwargs)[source]

Creates a heat pump element in prosumer[“heat_pump”] and an heat pump controller

INPUT:

prosumer - The prosumer within this heat pump should be created

OPTIONAL:

delta_t_evap_c (float, default 15) - Constant temperature difference at the evaporator [C]

carnot_efficiency (float, default 0.5) -

pinch_c (float, default 15) -

delta_t_hot_default_c (float, default 5) - Default difference between the hot (feed) temperatures [C]

name (string, default None) - A custom name for this heat pump

index (int, default None) - Force a specified ID if it is available. If None, the index one higher than the highest already existing index is selected.

in_service (boolean, default True) - True for in_service or False for out of service

max_p_comp_kw (float, default None) - Power of the compressor [kW]

min_p_comp_kw (float, default None) - Minimum working power of the compressor [kW]

max_ramp_up_kw_per_s (float, default None) - Maximum ramping up speed of the compressor [kW/s]

max_ramp_down_kw_per_s (float, default None) - Maximum ramping down speed of the compressor [kW/s]

max_cop (float, default None) - Maximum COP

cond_fluid (str, default None) - Fluid at the condenser. If None, the prosumer’s fluid will be used

evap_fluid (str, default None) - Fluid at the evaporator. If None, the prosumer’s fluid will be used

mode (str, default ‘carnot’) - COP calculation mode. Options: ‘carnot’ or ‘lorenz’ (case insensitive)

level (int, default 0) - The level of the controller

order (int, default 0) - The order of the controller

period (int, default 0) - Index of the period, default is 0

OUTPUT:

index (int) - The unique ID of the created heat pump controller

EXAMPLE:

create_controlled_heat_pump(prosumer, “heat_pump1”)

Controller

Input Static Data

Parameter	Description	Unit
name	A custom name for this heat pump	N/A
delta_t_evap_c	Constant temperature difference at the evaporator	Degree Celsius
carnot_efficiency	Carnot efficiency, usually between 0.4-0.6, used to simplify the calculation of the heat pump COP	N/A
pinch_c	Minimum temperature difference between the heat pump and the heat source/sink (pinch temperature)	Degree Celsius
delta_t_hot_default_c	Default temperature difference between condenser outlet and inlet on the hot side	Degree Celsius
max_p_comp_kw	Maximum power of the compressor	kW
min_p_comp_kw	Minimum working power of the compressor	kW
max_ramp_up_kw_per_s	Maximum ramp-up rate of electrical power	kW/s
max_ramp_down_kw_per_s	Maximum ramp-down rate of electrical power	kW/s
max_t_cond_out_c	Maximum condenser outlet temperature	Degree Celsius
max_cop	Maximum COP	N/A
cond_fluid	Fluid at the condenser. If None, the prosumer’s fluid will be used	N/A
evap_fluid	Fluid at the evaporator. If None, the prosumer’s fluid will be used	N/A
mode	COP calculation mode. Options: ‘carnot’ (default) or ‘lorenz’	str	‘carnot’ or ‘lorenz’	No
overflow_strategy	How to dispatch surplus mass flow to responders when the heat pump is clamped to `min_p_comp_kw` but the demand requires a smaller condenser mass flow. `'dump_proportional'` (default) splits the surplus across responders in proportion to their requests, closing the energy balance; `'dump_on_last'` pushes the surplus onto the last responder at `t_cond_out_c`; `'cap'` drops the surplus and leaves a mismatch between `q_cond_kw` and the heat delivered to the responder (an `EnergyLeakWarning` is emitted). See Overflow Strategy: Dispatching Surplus Mass Flow.	str
in_service	True for in_service or False for out of service	boolean

Input Time Series

Parameter	Description	Unit
t_evap_in_c	Temperature of the heat source at the inlet of the evaporator.	Degree Celsius

Output Time Series

Parameter	Description	Unit
q_cond_kw	The provided power at the heat pump condenser	kW
p_comp_kw	The compressor consumed electrical power	kW
q_evap_kw	The extracted power at the heat pump evaporator	kW
cop	The operating Coefficient Of Performance	N/A
mdot_cond_kg_per_s	The mass flow rate at the condenser of the heat pump	kg/s
t_cond_in_c	The input temperature at the condenser of the heat pump (return pipe)	°C
t_cond_out_c	The output temperature at the condenser of the heat pump (feed pipe)	°C
mdot_evap_kg_per_s	The mass flow rate at the evaporator of the heat pump	kg/s
t_evap_in_c	The input temperature at the evaporator of the heat pump (feed pipe)	°C
t_evap_out_c	The output temperature at the evaporator of the heat pump (return pipe)	°C

Mapping

The Heat Pump Controller can be mapped using FluidMixMapping.

The heat pump can be used as responder for a FluidMix mapping, taking the output from another controller as its input
The following outputs are mapped:
- mdot_kg_per_s
- t_cond_out_c

Note

If the heat pump is not mapped as a responder, it is considered to be connected to free air. In this case, the input t_evap_in_c should be mapped from a timeseries of the ambient air temperature.

Model

class pandaprosumer.controller.models.heat_pump.HeatPumpController(prosumer, heat_pump_object, order, level, in_service=True, index=None, name=None, **kwargs)[source]

Controller for heat pumps.

Parameters:

prosumer – The prosumer object
heat_pump_object – The heat pump object
order – The order of the controller
level – The level of the controller
in_service – The in-service status of the controller
index – The index of the controller
kwargs – Additional keyword arguments

control_step(prosumer)[source]

Executes the control step for the controller.

Parameters:: prosumer – The prosumer object

name_class()[source]: Return the controller class identifier used in results and logging.

t_m_to_receive_for_t(prosumer, t_feed_c)[source]

For a given feed temperature in °C, calculate the required feed mass flow and the expected return temperature if this feed temperature is provided.

Parameters:

prosumer – The prosumer object
t_feed_c – The feed temperature

Returns:

A Tuple (Feed temperature, return temperature and mass flow)

The evaporator of the heat pump should get heat from a District Heating Network or from the ambient air.

The condenser should be connected to downstream elements in the prosumer or to a District Heating Network.

Schematic representation of a thermal-based heat pump considered by EIFER during modeling (source: own creation)

To understand the thermal-based heat pump model developed by EIFER, it is first necessary to have an overview of the technologies and parameters involved in the modelling of a heat pump. Figure 4 offers a schematic representation of a thermal-based heat pump considered by EIFER during modelling.

The thermal-based heat pump modelled includes a compressor, a condenser, an expansion valve, and an evaporator. In general terms, a heat pump requires a certain amount of power \(P_\text{comp}\), it transfers a certain amount of heat \(Q_\text{cond}\) to the heat sink, and it absorbs a certain amount of heat \(Q_\text{evap}\) from the heat source.

The thermal-based heat pump model developed by EIFER calculates the required heat pump mass flow on the evaporator (\(\dot{m}_\text{evap}\)) to produce enough heat (Qcond) to meet the requirements of the network in terms of temperature increase (\(T_{\text{out}_\text{cond}} - T_{\text{in}_\text{cond}}\)) with a given mass flow (\(\dot{m}_\text{cond}\)).

To do so, a series of parameters are required as a given input from the model developed:

\(T_{\text{out}_\text{cond}}\): target temperature need from the network.
\(T_{\text{in}_\text{cond}}\): return temperature from the network to the considered HP.
\(\dot{m}_\text{cond}\): mass flow in the network, which for simplicity is considered water.
\(T_{\text{in}_\text{evap}}\): temperature of the heat source at the inlet of the evaporator.
\(\Delta T_\text{evap}\): it is the temperature difference between the inlet and outlet of the evaporator on the heat source side.
\(Pinch\): it is a small temperature difference, usually in between 5-10 K, to account for temperature difference between the heat pump side and the heat source (or heat sink) side.
\(\eta_\text{C}\): Carnot efficiency, usually between 0.4-0.6, used to simplify the calculation of the heat pump COP
\(T_{\text{out}_{\text{cond}_\text{max}}}\): it is the maximum temperature that can be achieved at the outlet of the condenser on the heat sink side, it is usually given from the HP manufacturer and it depends on the refrigerant chosen.

Then, the calculation steps modelled follow the equations presented below:

The first step is to calculate the condenser thermal demand \(Q_\text{cond}\), meaning the thermal need from the network

\begin{align*} Q_\text{cond} &= \dot{m}_\text{cond} * Cp_\text{cond} * (T_{\text{out}_\text{cond}} - T_{\text{in}_\text{cond}}) \\ \end{align*}

Where \(Cp_\text{cond}\) is the specific heat capacity at constant pressure of the fluid used in the heat network, which is usually water

Then the temperature at the outlet of the evaporator is calculated (\(T_{\text{out}_\text{evap}}\))

\begin{align*} T_{\text{out}_\text{evap}} &= T_{\text{in}_\text{evap}} + \Delta T_\text{evap} \\ \end{align*}

Thanks to step n°2 it is possible to calculate the Carnot COP (\(COP_\text{C}\))

\begin{align*} COP_\text{C} &= \frac{T_{\text{out}_\text{cond}} + T_\text{pinch} + 273.15\text{K}}{T_{\text{out}_\text{cond}} - T_{\text{in}_\text{evap}}} \\ \end{align*}

Which allows a simplified calculation of the heat pump COP (\(COP_\text{HP}\))

\begin{align*} COP_\text{HP} &= \eta_\text{C} * COP_\text{C} \\ \end{align*}

The required electrical power \(P_\text{comp}\) to provide \(Q_\text{cond}\) is also calculated

\begin{align*} P_\text{comp} &= \frac{Q_\text{comp}}{COP_\text{HP}} \\ \end{align*}

From which it is possible to derive the heat required from the heat source \(Q_\text{evap}\)

\begin{align*} Q_\text{evap} &= Q_\text{cond} - P_\text{comp} \\ \end{align*}

And finally the mass flow \(\dot{m}_\text{evap}\) needed at the evaporator for the HP to provide the required \(Q_\text{cond}\) Where \(Cp_\text{evap}\) is the specific heat capacity at constant pressure of the fluid used in the heat sink

\begin{align*} \dot{m}_\text{evap} &= \frac{Q_\text{evap}}{Cp_\text{evap} * \Delta T_\text{evap}} \\ \end{align*}

It is important to check that the temperature at the outlet of the condenser is not above the maximum temperature achievable from the considered HP with the given refrigerant, otherwise that means that the maximum heat that can be provided to the network is lower than the requirement

\begin{align*} \text{if}\ T_{\text{out}_\text{cond}} > T_{\text{out}_{\text{cond}_\text{max}}}\ \text{then}\ Q_\text{cond} &= \dot{m}_\text{cond} * Cp_\text{cond} * (T_{\text{out}_{\text{cond}_\text{max}}} - T_{\text{in}_\text{cond}}) \\ \end{align*} The COP and power consumption are then recalculated based on the new :math:`Q_\text{cond}`.

If the COP is higher than the maximum COP of the HP, the power consumption is set to the maximum power, \(T_{\text{out}_\text{cond}}\) is also recalculated based on the maximum COP.
If the power consumption is higher than the maximum power of the HP, \(\dot{m}_\text{cond}\) is recalculated so that the power consumption is set to the maximum power.

\begin{align*} \text{if}\ P_\text{comp} > P_{\text{comp}_\text{max}}\ \text{then}\ \dot{m}_\text{cond} &= \frac{P_{\text{comp}_\text{max}} * COP_\text{HP}}{Cp_\text{cond} * (T_{\text{out}_\text{cond}} - T_{\text{in}_\text{cond}})} \\ \end{align*}

If the power consumption is lower than the minimum power of the HP, the heat pump is considered off and the power consumption is set to zero,

Note

Limitations of the model:

Assume a constant \(\Delta T_\text{evap}\)
Assume a constant \(\eta_\text{C}\)
The model does not account for dynamic effects such as thermal inertia or transient behavior.
The model assumes ideal behavior and does not include efficiency losses due to real-world factors like friction or heat loss.

Edge Cases and Error Handling

The heat pump model includes several edge case handling mechanisms:

Ramp Up/Down Constraints: The model has the option to enforce maximum ramp-up and ramp-down rates for the compressor power to simulate realistic operational constraints.
Temperature Limits: The model checks and enforces maximum condenser outlet temperature limits to stay in realistic ranges.
COP Limits: The model enforces maximum COP limits to ensure realistic performance characteristics.
Power Limits: The model enforces both minimum and maximum power limits for the compressor. The option to add a minimum power ensures a simulation operating closer to real systems contraints.
Mass Flow Constraints: The model handles cases where the evaporator mass flow differs from the required mass flow by implementing bypass logic (to handle any extra mass flow at the evaporator) or recalculating the heat demand (if the available mass flow at the evaporator is not enough for the heat pump to satisfy the demand).
Shutdown Conditions: The model properly handles shutdown conditions when there is no demand on the condenser or when operational limits are exceeded.