Heat loads in LadyBug and calculation method of HoneyBee Peak Loads component

grasshopper honeybee
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Hi,

I have been working with the “HB Peak Loads” component and noticed a few things that go against my understanding of how the component works and general questions. The three major items are:

  1. What calculation method does this component use to produce the peak loads?
  • There are two accepted methods of calculating heat loads in accordance with ASHREA Fundamentals 2017. These being Heat Balance Method (Iterates in time steps over the day calculating the loads based of heat balance equations) and Radiant Time Series (Utilises table coefficients to multiply against the loads before summing them all together).
  • From my research it appears that HoneyBee relies on Energy Plus’s method of calculation which uses the Heat Balance Method of calculating heat loads .
  • This seemed consistent with the results, however, I noticed when I toggled the Monthly_cool_ parameter to “LB EPW to DDY” the results seemed to resemble a normal distribution which more closely aligns with the RTS method.
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  1. How are gains and profiles incorporated into this calculation? What control over this is available?
  • I, upon analysing the outputs have compared my set gain profiles with the outputs of the “HB Peak Loads”. It appears that the set profiles are note reflected with the output being consistent across the entire day. (Cannot attach a file to show this as I am a “new user”)
  • By inspecting this it looks as though the values are being “saturated” similarly to one of the options IES provides where it is set to 100% at all times. This isn’t a huge issue in itself but depending on the situation can impact the heat loads.
  1. How are the solar gain determined by this component?
  • The calculation of solar gains is dependent on the software. IES utilises sun cast to get accurate data where as others simply take the glazing area insulative value and calculate it depending on the orientation.
  • I am comparing against IES and noticed a large disparity between them. I am aware IES definition of solar gains may diverge from Energy Plus by including window conduction but am struggling to find sources to support this.

Thanks in advance!

4 Likes
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Hi @Christo
Did you discover what methods HB uses?

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I’m also intrigued by these questions. It would be nice if someone could elaborate on the possible answers.

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Sorry that no one answered this 3 years ago. Hopefully, a lot of you found the answers by looking at other posts on the forum but, for the sake of others coming here, these are the answers:

The HB Peak Loads component always uses EnergyPlus. So, yes, it is always using the Heat Balance method.

It looks like you had the right intuition of changing the schedules assigned to your Honeybee Rooms but you probably forgot to change the _summer_des_ and _winter_des_ values used on a component like HB Weekly Schedule. EnergyPlus allows you to specify different daily profiles for design days vs. typical days of an annual simulation. Only the design day profiles are used by the Peak Loads component. So change the design day profiles of the schedules you are assigning to the Honeybee rooms and you will see the change reflected in the loads.

By using EnergyPlus’s PolygonClipping method to account for shading effects on the window. The component uses the EnergyPlus “FullExteriorWithReflections” solar distribution so that it accounts both for blocked sun on the window and reflected sun on the window by context geometry.

EnergyPlus window constructions have separate properties for transmittance, absorptance and conductivity. So you’ll see the incoming solar split between direct transmission (the solar term in your screenshot) and the solar heat that was absorbed by the glass and then conducts to the interior (part of the window conduction term in your screenshot).