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What input is needed?

Electrical system

PhotoVoltaics and Batteries are part of the Electrical system from IDA ICE 5. Apart from PV, it is also possible to model electricity production from a Wind turbine. The capacity of the electrical system is set under Grid settings. A description of how to set up a PV system in IDA ICE is given in the PV Getting Started Guide.

PhotoVoltaics (PV) converts the incoming solar irradiation to electrical energy. The panels can be free standing or integrated with the building model. Self-shading by building parts and neighborhood PV panels can be taken into account as well as the thermal balance of the modules and their backside ventilation for the building integrated panels. For modelling PV production, IDA ICE provides two model fidelities:

• The generic PV model calculating with a single electrical system efficiency
• The very detailed 1 diode model considering the characteristic curve of a solar cell and containing models for
  • PV modules (or PV panels)
  • PV strings
  • PV inverters

In particular, when it comes to electrical energy, actors within the assessment boundary of a building can act as energy consumers or producers. Through clever energy management and trading between individual such actors (called "traders"), energy communities can minimize the load on the grid and maximize the degree of self-sufficiency. Read more about this in the section Energy sources.

Generic PV model

For most cases, this PV model is sufficient. Parts of the building envelope can be covered with PV and with help of the follwing parameters, the exact chronological sequence of the produced electrical power can be calculated.

• Orientation of the panels (when tilted or twisted against the orientation of the building envelope surface)
• Relevant geometric parameters like distance between two rows
• Fraction of the envelope surface that is covered with PV panels
• PV panel efficiency at standard conditions
• PV panel thickness (for the thermal mass to calculate temperautre dependency of the efficiency)
• Depth of the air gap behind PV panels (for the ventilation of the backside)
• PV system losses from panel to grid (cables, inverters etc.)

PV modules

Alternatively, the user can use a more detialed model, which is called the "1 diode model" and takes the chracteristic curve of a solar cell into accont. With this model, a detailed maximal power tracking of partially shaded modules and strings will be considered (Shading on cell level). Using this model is only recommended for cases, where e.g. an optimization of the stringing is to be performed, or the profit from using AC inverters or optimizers is to be considerd.

The PV panels must be given a location on a building body. The placement is done in the 3D view using a similar gridding feature as for windows placed on a façade. The PV panels contain a number of input parameters, that can be taken form a database with a number of commercially available products. The most important parameters are:

• Length, width and thickness
• Length and width of the part that is covered by solar cells
• Mass
• Short-circuit current
• Open-circuit voltage
• Maximum power point current
• Maximum power point voltage
• Temperater coefficient for short-circuit current
• Temperatur coefficient for open-circuit voltage
• Arrangement of cells within the module
• Number of cells in series

In the user interface, you will find two diefferent types of PV modules: AC panels (called "PV AC panel") and DC panels (called "PV panel"). However, the difference is only that the definition of inverter parameters is on panel level for the former, and on string level for the latter.

PV strings

DC panels do not come with inbuilt inverters. They need to be grouped into strings in order to allocate inverters to them. It is not relevant, how the panal within a string are electrically interconnected. The user only has to group the panels. Optimizers for partially shaded panels or strings can be added to maximize the electrical power output.

PV inverters

Either each AC panel or string of DC panels need to be assigned with an inverter of suitable size depending on the number of DC panels in the string. While doing this, the user is shown whether the string voltage is within the range of the inverter limits.

Batteries

Batteries can be added to the electrical system under the Electrical System widget. Only one type of model can be used but there can be several batteries connected in series and parallel. The model must be taken from the database, and a charger must be chosen from the database. It is also possible to set schedules for charging from the grid and for discharging. The default values are to never charge from the grid and always allow discharging. The charging and discharging is determined by the electrical power grid object depending on if there is a surplus of produced energy or a need for extra energy. Thermal balances are computed for both the charger and the batteries. The batteries can be chilled by different types of fans, liquid and heat pipes.

Wind turbines

A single wind turbine can be added to the electrical system. The performance of the wind turbine is given by a performance curve as a function of the wind speed. The user can input the height, maximum power and reference air density. The produced electricity is handled the same way as the electricity produced by the PV panels and can be used by the building or sold to the outside.

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