[TRNSYS-users] how to get a fixed solar fraction

[Cramer Silkworth]

Carlos,

I spoke too soon I think. The code I sent yesterday didn't actually work
the way I thought. Here's a fixed version which works properly - I had
two parameters mixed up and was sending the wrong values back into the
type for hysterersis. Whoops.

*-----------------------------------------------------------------------
---------------
UNIT 30 TYPE 2 Window Opening/Closing Controller
*-----------------------------------------------------------------------
---------------
PARAMS 2
5	! num of oscillations before sticking
95	! high limit cutoff - OFF if input 3 exceeds this value

INPUTS 6
Tdb_zone	! upper input temp
0,0		! lower input temp
0,0		! high limit cutoff monitored value
WindowsShut	! hysteresis
0,0		! upper dead band
0,0		! lower dead band
*initial/constant values:
20  0  90  1  25  -50

EQU 3
hour = mod(time, 24)
WindowsShut = [30,1] * not(eql(hour,6))
WindowsOpenable = not(WindowsShut)

*-----------------------------------------------------------------------
---------------


-----Original Message-----
From: Cramer Silkworth 
Sent: Wednesday, November 05, 2008 12:37 PM
To: trnsys-users at engr.wisc.edu
Subject: Re: [TRNSYS-users] how to get a fixed solar fraction

Carlos,

I actually just now had a similar problem, where I wanted to have a
particular value reset at a certain time every 24 hours. It's part of a
natural ventilation control scheme: I wanted to "shut the windows," so
to speak, if the space temp reached a certain point (and reactivate
mechanical cooling), but also to not allow the windows to "reopen" for
the rest of the day. I wanted to add "real-world" user behavior to the
system - once it gets too hot and the A/C gets turned on, people rarely
stop to think later in the day that maybe it's cooled off outside and
the windows can be opened again. I hope I haven't digressed to far but I
want to set up my situation. Anyway:

I used Type 2, the differential controller with hysteresis, and where
you normally feed its output back into it for hysteresis (input 4), I
put a variable which is normally the output of the function but modified
by a time-based reset. here's the code (only useful if you code by hand
I suppose, not in SimStudio...):

*-----------------------------------------------------------------------
---------------
UNIT 30 TYPE 2 Window Opening/Closing Controller
*-----------------------------------------------------------------------
---------------
PARAMS 2
5	! num of oscillations before sticking
95	! high limit cutoff - OFF if input 3 exceeds this value

INPUTS 6
Tdb_zone	! upper input temp
0,0		! lower input temp
0,0		! high limit cutoff monitored value
WindowsOpenable	! hysteresis
0,0		! upper dead band
0,0		! lower dead band
*initial/constant values:
20  0  90  1  -50  25

EQU 2
hour = mod(time, 24)
WindowsOpenable = not([30,1] * not(eql(hour,6)))
*-----------------------------------------------------------------------
---------------

I'm still working on it, but it seems to be doing what I want. Maybe
this method can be adapted to your situation. 

Hope that helps,
Cramer

J. Cramer Silkworth
Transsolar Climate Engineering
Technical consulting for energy efficiency and environmental quality in
buildings.
145 Hudson Street
Suite 402
New York, NY 10013
Office: 212-219-2255
silkworth at transsolar.com





-----Original Message-----
From: Matt Duffy [mailto:duffy at tess-inc.com]
Sent: Wednesday, November 05, 2008 10:44 AM
To: Carlos Flores; trnsys-users at cae.wisc.edu
Subject: Re: [TRNSYS-users] how to get a fixed solar fraction

Dear Carlos Flores,

I am not too familiar with all of the controllers, but I do know that
most of them iterate with the TRNSYS time step.  The exception to this
that I know is the PID controller has a mode that does not follow the
TRNSYS time step, but like I said, I am not too familiar.

You might have to get creative with an equation. The list of EQUATIONS
Statements are also in the TRNEdit Manual (ref. 7.3.9, page 23).

Best regards,

Matt Duffy



----- Original Message -----
From: "Carlos Flores" <karlitro at gmail.com>
Sent: Wed, November 5, 2008 8:20
Subject:Re: [TRNSYS-users] how to get a fixed solar fraction


In addition to the previous e-mail,

Is there any controller that actually can work in a 24 hour basis and
not only for each time step?

Best regards

Carlos Flores
Universidad de Chile
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----- End of original message -----

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