Hi, Jean
I was not saying that EPlus was not good enough as a software research tool. The part of simulatin tool that are commonly used by this group is schedule driven.
DCV is another module in EPlus, that is good. I have not looked at the EPlus modules in detail since version 3.0.
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Years ago, I was not certain in the system capacity requirement in one installation. I suggested to under design the capacity to save initial cost and keep the room adjacent to the plant room as an ICE room. If the weather or the occupancy was really larger than the full capacity, the operator would call the local ice making factory to dump a load of ice in that room. Because of that proposal, the design was approved. For the following five year, we did not have the need to use the ICE room.
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The EPlus simulation gives you the margin of two or more different design and capacity scenario. The operational cost and initial cost amount provide the guidance of choice. The simulation need not be exact.
I am not really interested in the LEED certification. It is mainly politics. EPlus can do more than just for the certification of green buildings. In your case, you may still have rooms to save by reducing building heat load.
A computer controlled distributed modular system is probably more economical to install and operate.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Mon, 26 Sep 2011 14:52:55 +0000
Subject: [EnergyPlus_Support] Re: OutdoorAir:Mixer questions
I read your reply many times and fully agree, however I won't go as far as talking about software limitations of e+ in particular. E+ actually has objects for CO2 based DCV, but I was limited with the DOAS and had to build a bit of a custom add-on as you say.
As you stated, in real life a DCV system can use either occupancy sensors (direct or indirect) or CO2 sensors. I have not compared the two stradegies, because it is an existing system using the latter. Some of my zones are large volumes with high swings in occupancy, so I can understand why the latter stradegy was chosen. For me, however the goal was to find as close as possible how high the peak chilled water rate will be given a strict set of design day data. The lessons that are learnt are "nice to now" but sadly, I don't think anyone cares. All that is interesting is the bottom line peak district chilled water usage rate. As I said before, this is not what simulations are good for...that being said, it should hopefully be better than the hand calculation method. A sensitivity analysis is actually needed (and depending on the politics, may even get ordered).
As you stated, in real life a DCV system can use either occupancy sensors (direct or indirect) or CO2 sensors. I have not compared the two stradegies, because it is an existing system using the latter. Some of my zones are large volumes with high swings in occupancy, so I can understand why the latter stradegy was chosen. For me, however the goal was to find as close as possible how high the peak chilled water rate will be given a strict set of design day data. The lessons that are learnt are "nice to now" but sadly, I don't think anyone cares. All that is interesting is the bottom line peak district chilled water usage rate. As I said before, this is not what simulations are good for...that being said, it should hopefully be better than the hand calculation method. A sensitivity analysis is actually needed (and depending on the politics, may even get ordered).
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