Models

This page gives an overview of the available models in SIMONA.

Model

Description

ChpModel

Combined heat and power plant

WecModel

Wind energy converter

EvcsModel

Electric Vehicle Charging Station

ChpModel

This page documents the functionality of the CHP Model (combined heat and power plant model) available in SIMONA. This model is part of the SIMONA simulation framework and represented by an agent. The current model is feasible to simulate nano- and micro-CHP units. As it is a cross-sector agent (heat/electricity) the usage of a house-heat-model is mandatory.

Attributes, Units and Remarks

Attribute

Unit

Remarks

uuid

universally unique identifier

id

human readable identifier

operationInterval

time interval, in which the system is operating

scalingFactor

scaling the output of the system

qControl

type of reactive power control

sRated

kVA

rated apparent power

cosPhiRated

rated power factor

pThermal

kW

rated thermal power (generated by CHP unit)

storage

thermal storage

Implemented Behaviour

Assumptions

The CHP unit is able to operate either at full load or not at all. Uncovered heat demand of former time steps is not considered in the following steps, as the CHP unit does not posses a memory.

Agent Objectives

The objective of the CHP agent is to cover the given heat demand in each time-step.

Storage medium

This model can be implemented with any mutable storage (meaning that the storage requires the trait MutableStorage). The CHP unit is able to store/take energy, while the underlying storage medium performs the calculations for these operation.

The implemented behaviour is shown in the program sequence plan below. In general, the unit will turn on, if the energy in the storage is too low to satisfy the given heat demand and will turn off if the storage is completely filled. During operation, the CHP unit operates at full utilization.

Implementation:

../_images/ChpModelCalculation.png
Mathematical concept

The implementation of the CHP unit’s behavior is based on the following mathematical model.

Variable

Remarks

c(t)

indicates if the CHP unit is running or not

I

interval of two time steps (t-1, t]

td(t)

time of a single time step

WD(t)

heat demand

Wchp,n(t)

rated heat production

Wst(t)

storage level of the storage medium given by energy

Wst,min

minimum storage level of the storage medium given by energy

Wst,max

maximum storage level of the storage medium given by energy

Wges(t)

Wchp,n(t) + Wst(t)

deltaWD(t)

WD(t) - Wchp,n(t)

Qth,chp,n(t)

rated heat flow produced by the CHP

Pchp,n(t)

rated active power production

Pgen(t)

generated active power

Qgen(t)

generated reactive power

Given a time interval I, the heat demand WD(t-1), the running status c(t-1) and the storage energy level Wst(t-1) the CHP model calculates if the heat demand can be covered and if the CHP unit has to be turned off/on.

../_images/ChpModelMathematicalNotations.png

WecModel

This page describes the wind energy converter model (WecModel). Given the current wind velocity, temperature and air pressure the model can calculate the wind turbines active power output.

Attributes, Units and Remarks

Attribute

Unit

Remarks

uuid

universally unique identifier

id

human readable identifier

operationInterval

time interval, in which the system is operating

scalingFactor

scaling the output of the system

qControl

type of reactive power control

sRated

kVA

rated apparent power

cosPhiRated

rated power factor

rotorArea

the swept area of the turbines rotor

betzCurve

see example below (Enercon E-82)

Calculation

The figure below depicts the calculation steps as implemented.

../_images/WecModelCalculation.png
Air density

The air density is calculated using the temperature and the air pressure, as stated in the diagram above. For this calculation the formula ρ = (P * M) / (R * T) is used. The arguments for this formula are listed in the table below. In case no air pressure is given, the default value 1.2401 kg/m³ is returned, which corresponds to the air density at sea level at 20° Celsius.

Argument

Unit

Remarks

P

Pa

air pressure

M

kg/mol

molar mass of air (0.0289647)

R

J/(mol*K)

universal gas constant (8.3144626181532)

T

K

temperature

Note, that the arguments M and R are constants. Their values are contained in the column “Remarks”. After inserting the constant values the formula looks as follows: ρ = P / (287.058 * T)

Enercon E-82

It is useful to look at a real wind turbine for the visualization of some parameters.

Rotor area

The Enercon E-82 has a three-bladed rotor with a diameter of 82m. A rotors swept area is a circle, therefore it is calculated as follows: A = π * r². The swept area (rotorArea) of the Enercon E-82 is 5281.02 m² = π * (82m / 2)².

Betz curve

The betz curve (or betz characteristic) is a mapping of wind velocities to cP values. It is used to determine the power that can be extracted from the wind. It follows Betz’s law. Each wind turbine has a unique betz curve. The figure below shows the betz curve for the Enercon E-82 wind turbine.

../_images/EnerconE82cpPlot.png

The cut-in wind velocity is 2 m/s, meaning that the turbine requires wind speed of at least 2 m/s to produce energy. The cut-off wind velocity is 34m/s, meaning that the Enercon E-82 won’t produce energy for velocities that are higher.

EvcsModel

The currently connected EvModels are saved within the state data of EvCsAgent and passed to EvCsModel with each trigger. The model then calculates the active load of the charging station.

Attributes, Units and Remarks

Attribute

Unit

Remarks

uuid

universally unique identifier

id

human readable identifier

operationInterval

time interval, in which the system is operating

scalingFactor

scaling the output of the system

qControl

type of reactive power control

sRated

kVA

rated apparent power

cosPhiRated

rated power factor

chargingPoints

number of charging points available

locationType

the charging station location type

Calculation

The following arguments need to be provided for power calculation:

Argument

Unit

Remarks

dataFrameLength

duration in ticks until next EV movement data

currentEVs

set of EVs connected to the CS at this moment