# Processing Energy Plus outputs. COP and?

#1

I’m about to present some data from my energy model and need to know if there are additional processes I need to perform similar to the COP calculations.

I have been wondering if my total heat load is accounting for internal gains through lighting, people, and equipment. Is this accounted for or do I need to subtract these units?

I also assume that my total heating and cooling is accounting for solar gain. I have tested this and believe it is.

Anything else I’m missing to get good numbers out?

#2

David,

I am not sure if I am understanding your question but energyplus is running an energy balance calculation that accounts for all of the terms that you see in this chart:

http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&for…

If you are looking for output heating and cooling in units of electricity/fuel rather than heating/cooling load, I suggest that you run your modyl with a real HVAC system instead of the default ideal air loads as you see in this example file:

http://hydrashare.github.io/hydra/viewer?owner=chriswmackey&for…

This will likely be much more accurate than multiplying your ideal air loads by a COP.

-Chris

#3

Hi Chris,

COP depends on temperature e.g. in some building codes there are 2 minimum COPs required (T1,T3). What’s the accurate way in such cases? Would it make sense to make 2 groups of months or hours with average temperatures close to T1 and T3 and then divide each group’s energy loads by corresponding COP? Is there any way to calculate it fast and accurate?

Thank you

#4

@AryanShahabian ,
If you know what you are doing, rough calculations of the COP like what you mention can be decent ways of approximating energy use. However, the state of the art in energy modeling practice is to model fully detailed HVACs that use chiller objects in the energy simulation file. Such chiller objects are defined by curves (literally just polynomial equations), which calculate the COP as the simulation is running at every timestep of the calculation. They do this calculation using the outdoor air temperature, the temperature of the chilled water they are trying to make, the temperature of the water returning to the chiller, and the curve that you specify (which typically comes from manufacturer of HVAC equipment). Whenever you assign a system other than ideal air loads with the Honeybee_HVAC component, such chiller objects with default curves are being used. You can edit the coefficients of these curves within the OpenStudio GUI.

Let me know if that is clear.

#5

Thank you @chris for your comment.
Let’s say for instance we want to analyze the impact of glazing ratio on energy efficiency of buildings (in a certain climate e.g. Dubai), regardless of their mechanical/HVAC systems. In other words we want to look at the problem from an architectural point of view.

On the one hand, if we use ideal air loads, the results won’t include any COP, and on the other hand, if we set mechanical/HVAC systems, we should involve so many parameters and do multiple simulations which are far from the aim.

Please have a look at the attached image. It shows 3 pages of a green building code in Dubai, explaining the minimum requirements of HVAC systems.

According to your experience, do you think if there is any way to avoid modelling multiple HVAC systems while being able to reach results ranging close to reality?

Thanks