Simulation

EnergyPlus Version

Speckel utilises EnergyPlus™ (version 9.5.0 + and 22.2) for all our building simulation modelling.

For those unfamiliar, EnergyPlus™, it has been under development since 1997 and is an open-source whole-building energy modelling (BEM) engine. It is continuously maintained, thoroughly documented and fully supported.

The primary reason for providing two working versions of EnergyPlus™ is to include all the latest developments that the EnergyPlus™ engine has to offer, including new features and bug fixes to the simulation engine.

Hundreds of improvements have been made from EnergyPlus™ Version 9.5.0 to 22.2, rendering EnergyPlus™ 22.2 more stable while improving key areas such as moisture transfer, specific HVAC systems, air boundaries and ground heat transfer.

To select an Energy version, navigate to 'Modelling', select 'Simulation', and locate the 'EnergyPlus Version' dropdown. We recommend EnergyPlus™ Version 22.2 is used in all cases.

Custom Convergence Settings

Loads Convergence Tolerance Value

Loads Convergence Tolerance Value represents the maximum allowable difference between consecutive days' maximum heating and cooling loads for individual zones during the warm-up period. This parameter is essential for determining when the simulation has achieved a steady-state condition, ensuring accuracy by indicating when load fluctuations have stabilized within acceptable limits.

Temperature Convergence Tolerance Value

Temperature Convergence Tolerance Value refers to the maximum allowable difference between consecutive days' maximum and minimum zone air temperatures during the warm-up period. This parameter helps determine when the simulation has reached a steady-state condition, ensuring accurate results by indicating when temperature fluctuations have stabilised within acceptable limits.

Maximum Warmup Days

Warm-up days ensure simulation accuracy by stabilising building thermal systems before data collection. This process addresses inaccuracies that could affect HVAC calculations. Convergence is checked by tracking parameters like zone air temperature and heating/cooling loads. Simulation begins when these parameters stay within tolerance for consecutive days, indicating steady-state conditions. Errors can arise in shorter simulations if warm-up isn't properly achieved, impacting energy and economic outcomes.

Custom Convergence Settings expose advanced EnergyPlus simulation parameters and can impact simulation runtime and accuracy. If unsure, disable this setting.

Step Size

Step Size refers to the time interval at which the simulation calculations are performed. This is also known as the "timestep" or "time step".

Set the number of timesteps per hour in a simulation, which effectively determines the step size. For example, if you set the timesteps per hour to 4, the step size would be 15 minutes (60 minutes / 4). This means that the simulation will perform its calculations and update the state of the building model every 10 minutes of simulated time.

Set a Step Size by navigating to 'Modelling' under 'Simulation' and locate the 'Step Size' slider, and set 1, 2,3 or 4 timesteps.

Solar Distribution

Solar Distribution refers to the method used to calculate the distribution of solar gains onto and inside a zone. The solar distribution method can significantly impact the results of an energy simulation.

The following Solar Distribution settings are available.

Minimal Shadowing: All beam solar that strikes a window is added to the zone as diffuse (scattered) solar, which is uniformly distributed across all surfaces in the zone. There is no attempt to model the impact of shadows on the distribution of solar gains.

Full Exterior: The model keeps track of shadowing on the exterior of the building, but once the sunlight enters a zone through a window, it is treated as diffuse solar and is uniformly distributed across all surfaces in the zone.

Full Exterior With Reflections: These options provide the most detailed modelling of solar distribution. They account for both exterior shadowing and the impact of interior furniture and partitions on the distribution of solar gains. With the "WithReflections" option, the model also accounts for reflections from interior surfaces.

To select Solar Distribution, navigate to 'Modelling', select 'Simulation', and locate the 'Solar Distribution' dropdown. Then select the desired Solar Distribution method.

Building Rotation

Building Rotation is nominated as the degrees from true North, e.g. 0° is no alteration, 90° where your building is rotated clockwise 90°.

Set Building Rotation by navigating to 'Modelling' under 'Simulation'. Then, nominate the degrees from true North and hit 'Save'.