Energy Balance Storage

Hi everyone,

I’m studying the energy balance of my model and I noticed that the storage term is very high : the annual storage load represents half the heating load. Knowing that this term should be very small, I think this value make my energy balance faulty.

My understanding of this term is that it’s computing from all the other variables of the energy balance. I’m trying to fix this problem but I don’t know these variables so I can’t figure out where the error came from.

Is there a way to explode the Storage term into all the variables computed ?
Is there anyone who knows what can cause an high value for this term ?

@antoine.abelard ,

The storage term in your balance isn’t too big in comparison to the heating/cooling load. Are these values for a month? or the whole year?

A high storage term over long periods of simulation time (like a month) is usually an indication of one of the following:

  1. You may not have connected all of the HBZones up to the energy balance, in which case the storage term is an indication of heat loss/gain to other zones.
  2. You are missing a term from the energy balance. For example, if there is natural ventilation in your model, the storage term might be accounting for gain/loss from natural ventilation.
  3. The simulation is actually unstable, in which case E+ will usually give you a severe error.

Do any of these fit the bill?

Hi Chris, thank you for your answer !

These values are for the whole year. I seen a topic where you was saying that the storage term should be relatively small over long time periods, that’s why I’m wondering if my energy balance is faulty.

More over, I’m doing the same simulation on IES-VE in order to compare results between the two softwares and it seems that the storage term is the one causing diffrences between my cooling and heating needs. For the cooling, I got a percentage difference equal to about 20% testing different calculation methods.

To answer your questions :

  1. I just got two HBzones and I think that they are both connected since I got the results for the two zones.

  2. I did my energy balance with all the gains of my model and I don’t think I’m missing a term because I did the same energy balance on VE : for the two softwares, all the terms are about the same, the only real difference is on the heating and cooling terms, and it seems to come from the storage term since VE don’t have that term on his energy balance.

  1. I got 2 severes errors in my simulation : “DetermineShadowingCombinations” and “This component will replace this HVAC system with an Ideal Air Loads system. To model advanced HVAC systems, use the Export to OpenStudio component.”

I can fix these errors choosing the “MinimalShadowing” method and set an Ideal Air Load system. But even when the errors are fixed, the storage term don’t really change and is still big relatively to the others terms.

Severe errors :

Fixing errors :

Annual storage term after fixing severe errors :

I hope I’m being clear, my english is not very good.

I’m really trying to get the sense of this storage term but I don’t really understand the meaning of it.

Hi Antonie,
I am trying to do similar test. in my simulation, storage also looks quite high. Have you figured out the reason in your case?