Central systems
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Central systems
All objects can be dragged from the palette on the left hand side to the building tab. To open the object, double click and choose “Open” in the shortcut menu. To remove the object, click the wastebasket. The following type of objects can be inserted:
Wind turbine
A wind generator may be described in terms of a performance curve, which describes generated power as a function of hub level wind velocity.
A Wind profile object must also be selected. This object describes the local vertical wind variation, which depends on the type of terrain.
Figure 58.
Solar energy
If solar thermal or photovoltaics systems have been added to the building, these will be visible in the building 3D and shading window as solar panels, Figure 61. By default these objects are placed in origo but can be given a more sensible position in 3D space by holding down the Ctrl-key and dragging the panel to a new position. The panel will move in the x-y plane. Hold down the shift-key to move the panel in the z-direction.
Solar panels are shaded by other shading objects. Solar panels themselves shade other solar panels and windows if they have been moved to a sensible position, i.e. if they are left at the origin they will not shade.
Generic solar thermal
Select a solar collector model from the drop down list. Either total area or number of units of the selected type can be specified.
Figure 59.
Generic photovoltaics & AC PV panel (with inverter)
Generic photovoltaics can be specified in terms of area and overall efficiency (panel as well as inverter system). It is also possible to choose an AC PV panel (with inverter) from a database (using the form for this). All generated electricity shows up as a negative contribution in the delivered energy report.
Figure 60.
Figure 61. A building with a solar panel/photovoltaics on the roof
Ventilation
All objects can be dragged from the palette on the left hand side to the building tab. To open the object, double click and choose “Open” in the shortcut menu. To remove the object, click the wastebasket. The following type of objects can be inserted:
Standard air handling unit
Figure 62.
The standard air handling system consists of the following components Figure 62: supply air temperature setpoint controller (1), exhaust fan (2), heat exchanger (sensible heat exchange only) (3), heating coil (4), cooling coil (5), supply fan (6), schedule (7) for operation of both fans and a schedule for the operation of the heat exchanger (8). The unit provides temperature-controlled air at a given pressure. Some key parameters of individual components are presented in the form; open them to edit. The supply air temperature setpoint is set in the Air distribution system dialog opened by double-clicking on the Air supply control box (1).
Exhaust air only AHU
Figure 63.
This AHU should be used for mechanical ventilation systems with exhaust air only. The make-up air in the rooms is ambient air. An error message is issued if a supply air flow is requested by any room.
AHU with electrical heating coil
Figure 64.
This AHU is similar to the default AHU, but heating is done by electricity.
AHU with return air and CO2 control
Figure 65.
This air handling unit provides the possibility of recirculating zone air in order to minimize the use of outdoor fresh air. Temperature control of supply air is done with the same options as for the default unit, including night ventilation and cycling. In addition, the CO2 level of the return air is controlled by a proportional controller. When the return air CO2 level is above the setpoint of any zone (by default 1000 ppm (vol)), a maximum amount of fresh air is used. As the measured CO2 level drops, the fresh air fraction is successively reduced down to zero, at 500 ppm (vol) (selectable in Additional settings in full ESBO).
Exhaust air with liquid heat recovery
Figure 66.
This AHU should be used for mechanical ventilation systems with exhaust air only and with an air-to-liquid heat recovery coil. Design parameters for the liquid loop is given in a separate form for the coil. Based on the given parameters, an approximate level of extracted heat is computed.
Normally, a brine to water heat pump or equivalent device should be added to the plant in order to lift the extracted heat to a useful temperature level. The size of the heat pump should be selected to extract approximately the intended amount of heat at design conditions. There is no control loop that maintains the targeted exhaust air temperature. If an oversized heat pump is selected, the air will be cooled too low. No warning is issued for this condition during simulation.
Enthalpy wheel air handling unit
Figure 67.
This air handling unit is the same as the Standard Air Handling unit except for the heat exchanger, which here models the behaviour of a thermal wheel with possible moisture exchange (according to prEN 16798-5-1.) An untreated wheel will only transfer moisture via condensation. The hygroscopic wheel is treated with a special desiccant material which enables moisture transfer. Sorption wheels have even higher sorptive capacity.
If Frost protection is enabled, the speed of the wheel is adapted to avoid frost formation. The user must then provide a minimum temperature level for the exhaust air. For dwellings 1 °C is recommended, while for other applications the risk of frost build-up is lower and lower temperatures can be selected.
AHU with limited capacity
The air handling unit is designed in a way that it can be used with the Swegon Wise water system.
The difference to the Enthalpy wheel air handling unit is that the heating and cooling coils have limited capacity. The capacity is calculated dependent on the settings of each coil. Click on the coils to alter the settings.
For heating the settings are as in the figure below
The heating power is then calculated as
Power=(“Dim Supply temperature” – “Dim outdoor temperature”)*1007*1.189 * ”Max supply air flow” /1000.
The mass flow in the valve is than calculated as Flow=Power/”Dim tem drop, liquid”.
For cooling the settings are as in the figure below.
The cooling power is then calculated as
Power=(“Hin_rat” – “Hout_rat”) *1.189 * ”Max supply air flow” where Hin_rat and Hout_rat are enthalpies calculated from the inlet and outlet temperatures and humidity at the rating point. The inlet humidity is given and the outlet humidity is estimated dependent on the average coolant temperature.
The mass flow in the valve is than calculated as Flow=Power/”Liquid temperature rise at rating”.
Hot storage
Generic hot water tank
Figure 68.
A hot water storage tank may be defined to store heat from, e.g. a solar collector. See the online help topic “Technical description of the generated plant” for further details
In full ESBO, the temperatures of the different tank layers may be studied by selecting Plant details for Requested output on the Simulation tab.
Cold storage
Generic cold water tank
Figure 69.
A cold water storage tank may be defined to store cold from, e.g., the evaporator circuit of a heat pump. See the online help topic “Technical description of the generated plant” for further details.
In full ESBO, the temperatures of the different tank layers may be studied by selecting Plant details for Requested output on the Simulation tab.
Topup heating
Generic topup heater
Figure 70.
The top-up heater is employed when the available water temperature drops more than 2⁰C below the highest requested temperature. Energy source as well as a constant production efficiency (or COP) can be selected. The total capacity can optionally be limited.
Base heating
Ambient air to water heat pump
Figure 71.
Figure 71 shows the dialog for a model with an air-to-water heat pump unit for water heating. At the given rating condition (press button to see dialog below), the model will yield given total power and COP. Note that this unit has its own ambient air heat exchanger, i.e. there is no need to add a separate such device to the model.
Figure 72.
Brine to water heat pump
Figure 73.
Figure 73 shows the dialog for a model with a brine to water heat pump unit for hot water heating. At the given rating condition (press button to see), the model will yield given total power and COP.
The cold (evaporator) side of the Brine to water heat pump, will automatically be connected to the brine circuit. In most situations, some ambient or ground heat exchanger must also be added by the user to the brine loop in order to collect heat for the heat pump. This is done by simply dragging such a component into the form. The cold side of the heat pump will always be connected to a heat exchanger in the cold tank and thus provide “free” cooling to the building whenever this is possible. Click to open the dialog for rating conditions
Figure 74.
Generic combined heating and power base heater
Figure 75.
A simple, fixed efficiency, CHP model is available.
Cooling
Generic chiller
Figure 76.
The energy source as well as a constant production efficiency (or cooling COP) can be selected. The total capacity can optionally be limited.
Brine to water chiller
Figure 77.
Figure 78.
Figure 78 shows the dialog for a model with a brine to water on-off controlled unit for water cooling. At the given rating condition (press button to see), the model will yield given total power and EER (cooling COP).
It is generally not recommended for most users to change any other parameter than the total cooling capacity.
Away from the rated point, the performance will be determined by the additionally specified parameters. These are measurable quantities but may not always be made available by equipment manufacturers. If parameters have been identified with respect to measured data from a real device, the model will predict the performance over the whole operating range within the accuracy of a few percent, typically around one.
The hot (condenser) side of the Brine to water chiller, will automatically be connected to the brine circuit. In most situations, some ambient or ground heat exchanger will must also be connected to the brine loop in order to dispose of the waste heat. This is done by simply dragging such a component into the form. The hot side of the chiller will always be connected to a heat exchanger in the hot tank and thus provide “free” heating to the building when possible. Click to open the dialog for rating conditions.
Figure 79.
Ambient heat exchange
Ambient air to brine heat exchanger with possible condensation
Figure 80.
Figure 80 shows the dialog for a model with a fan assisted ambient heat exchanger. In heat production mode, condensation may occur and therefore a wet coil rating point is required. The efficiency is defined with respect to an apparatus dew point which is the average of entering and leaving brine temperature. Wet coil leaving air conditions will lie on a straight line between entering conditions in the psychometric chart and the apparatus dew point. The dimensionless distance along this line is defined as the efficiency.
Ground heat exchange
All ambient or ground heat exchangers are connected to a brine loop. The brine loop will always be connected to heat exchangers in the hot and cold supply systems. This way, a ground heat exchanger can directly cool the building without the assistance of a chiller. However, should a Brine to water chiller be dragged in, its condenser will also be cooled by the brine loop (and the resulting hot brine may even be warm enough to be utilized directly for heating).
When two or more central system boxes are graphically connected the added system covers the function of both boxes.
Select Plant details under Requested output in the Simulation tab in order to see the time-evolution of key Central system variables.
Heat exchange with given temperature source
Figure 81.
The model is used to specify the option of heat exchange with a temperature source with a practically infinite capacity, such as sea water or in some approximations the ground. In place of the default constant temperature, a schedule that prescribes the temperature variation as a function of time can be given. To do this, click the hyperlink.
The given power, temperature difference and pressure loss are used to determine sizes of the heat exchanger and associated pumps and pipes. Pumps are regarded to be capacity controllable down to zero flow with given constant efficiency.
Ground source borehole loop
A detailed model for a borehole system is provided. ESBO supports a series of identical boreholes that are positioned far apart from each other and that are connected in parallel. (A separate module is available for IDA ICE to study interacting boreholes.)
Figure 82.
The present version of ESBO only supports the study of a borehole system during the first year of operation. The ground temperature is started at the yearly average temperature of the climate file.
The default control options will try to use borehole heat (or cold) whenever it is needed and available. No long term strategies of storing heat for future use are employed.
Combined systems
Systems with combination of two functions, e.g. ventilation and heating.
Exhaust air with DX heat
A ventilation system with only exhaust air combined with a DX heat pump recovering exhaust air heat. When opening the macro and then the heat pump model, a heat pump can be chosen from a database through "Load from database... ". Also settings for the fan and the fan operation time can be done by opening the models.