Re: RES: [EnergyPlus_Support] Use of DOAS

["Jean Marais jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

There seems to be an ongoing battle to prove the case of DOAS vs. for typical American VAV with reheat systems. ASHRAE journal prints some of these cases. The take home message is that both systems need to be specifically set up and optimised taking the entire design and control strategy into account. They work very differently and should be "driven" differently. It makes drawing direct comparisons difficult.

I will say (IMO) that practically, I suspect DOAS to be less appropriate in relatively humid climates.

On 1 Feb 2017 10:14 a.m., "'Alberto Hernandez Neto' ahneto@xxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

Dear Jim,

 

Thanks for the response. I will check the inputs.

 

Regards,

 

Alberto

 

De: EnergyPlus_Support@yahoogroups.com [mailto:EnergyPlus_Support@yahoogroups.com]
Enviada em: terça-feira, 31 de janeiro de 2017 16:50
Para: EnergyPlus_Support@yahoogroups.com
Assunto: Re: [EnergyPlus_Support] Use of DOAS

 

Dear Alberto,

I believe that the fundamental question for every energy model is "Why?"

 

For example, "Why is the energy higher for DOAS in Sao Paulo?" To answer that question, you will need to analyze the results in more detail than total energy for an entire year. Is cooling energy higher than expected? Fan energy? Is the economizer providing substantial cooling benefit that is lacking in the DOAS?

That, in turn, requires close comparison of each file's inputs and also the outputs by category of energy use (e.g., fan energy, cooling energy, heating energy, etc.)

 

In a recent project, I noticed that the heating energy was much higher for one design than the alternative design. (I expected a small increase, not a big one.)

I discovered by reviewing hourly outputs that, of three systems, only one was very high - almost double.  That made me review inputs more carefully (comparison software such as WinMerge is helpful for this) and I discovered one seemingly innocent input that was causing the problem.

 

In short, I think that careful review is necessary, even when results appear OK.

 

I wish you good success in finding the reason behind the differences.

 

On Tue, Jan 31, 2017 at 1:05 PM, 'Alberto Hernandez Neto' ahneto@xxxxxx [EnergyPlus_Support] <EnergyPlus_Support@yahoogroups.com> wrote:

 

Dear ,

 

I am starting to analyze the use of DOAS for commercial buildings and my first attempt was to verify the two examples files : HVACTemplate-5ZoneFanCoil and HVACTemplate-5ZoneFanCoil-DOAS. I got the two examples and I simulated them for the same climate (São Paulo, Brazil).

 

For my surprise, the model with DOAS consumes 16% more energy than the one without DOAS? I simulated the same files for the climate of Chicago (original city in the site location of the example files) I got similar results. Shouldn´t be the opposite ?

 

I would appreciated any help.

 

Regards,

 

Alberto

 

 

 

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--

James V Dirkes II, PE, BEMP, LEED AP
CEO/President
The Building Performance Team Inc.
1631 Acacia Dr, GR, Mi 49504

Direct: 616.450.8653
jim@buildingperformanceteam.com

Website l  LinkedIn | May 2016 ASHRAE Journal article on energy modeling

...and the more I considered Christianity, the more I found that while it had established a rule and order, the chief aim of that order was to give room for good things to run wild.

 

 

 

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Posted by: Jean Marais <jeannieboef@xxxxxxxxx>

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