TYPE 69:  RADIATIVE SKY TEMPERATURE ESTIMATOR
written by David Summers, Solar Energy Lab, University of Wisconsin - Madison
February 1995

For some TRNSYS components, including the unglazed transpired collector system 
(Type 71), the sky temperature is needed to calculate the amount of radiation from 
the surface to the sky.  However, the sky temperature is not included in the TMY 
weather files.

This component calculates the sky temperature from data in a full TMY weather file.
Some of these data are missing, in which case the are replaced with the nearest 
previously recorded values.  In the TRNSYS deck, it is important to have reasonable 
initial values for the inputs.  The following are suggested:

7777.0  0.0  0.0  0.0  0.0  10125.0  0.0  0.0  0.0  0.0  0.0  0.0

A ceiling value of 7777 corresponds to a clear sky.  It is also important to make 
sure that the inputs to the Type 69 subroutine from the TRNSYS deck are not 
interpolated.  So, the data reader (Type 9) which reads the full TMY data file 
should have the parameters set such that interpolation is off.

The atmospheric pressure and snow cover indicator are also output.  The snow cover 
indicator is output so that the ground reflectance can be more accurately calculated
in the TRNSYS deck.


Parameters: none

Inputs from the original TMY file:
  1. Ceiling(202): Filled with 9's 2 out of 3 hours. (m * 0.1)
2-5. Sky condition(203): Filled with 9's 2 out of 3 hours.
  6. Station pressure(206): No known missing values. (kPa * 100)
  7. Dewpoint temp(207): No known missing values. (C * 10)
8-9. Cloud cover(209): Filled with 9's 2 out of 3 hours. (* 10)
 10. Snow cover(210): Filled with 9's at night.

Inputs from the SEL TMY file:
 11. Hour of the month
 12. Ambient temperature (C)

Outputs:
  1. Radiative sky temperature (C)
  2. Atmospheric pressure (kPa)
  3. Snow cover indicator


Sample TRNSYS Deck:

ASSIGN  commer.lst                    6
ASSIGN  commer.out                   11
ASSIGN  commert.plt                  12
ASSIGN  commerq.plt                  13
ASSIGN  MADISN.WI                    14
ASSIGN  MADISN.ALL                   15
ASSIGN  COMMER.DAT                   16
* LOGICAL UNIT 14 = SEL TMY DATA FILE.
* LOGICAL UNIT 15 = FULL TMY DATA FILE.
* LOGICAL UNIT 16 = HOURLY DATA ON INTERNAL GAINS AND AIR FLOW RATES.

SIMULATION  1  8760  1
WIDTH  72

UNIT 9 TYPE 9 DATA READER
PARAMETERS 26
*MODE  N  TD  21*(CONVERSION FACTORS)  LOGICAL-UNIT  FRMT
-2  8  1  -1 1 0  -2 1 0  -3 1 0  -4 1 0  5 0.1 0  6 0.0001 0  8 10 0
14  -1
*OUTPUTS 8
*MONTH  HR  IDN  I  TDB  HUMRAT  WINDVEL  WINDDIR

UNIT 10 TYPE 9 DATA READER 2
PARAMETERS 35
*MODE  N  TD  30*(CONVERSION FACTORS) LOGICAL-UNIT  FRMT
-2  10  1  -1 1 0  -2 1 0  -3 1 0  -4 1 0  -5 1 0  -6 1 0  -7 1 0
-8 1 0  -9 1 0  -10 1 0  15  1
(72X, F4.0, 1X, 4F1.0, 17X, F5.0, 4X, F4.0, 7X, 2F2.0, F1.0)
*OUTPUTS 10
*CEILING  SC(1-4)  PATM  TDP  NTOT  NOPAQ  SNOW

UNIT 11 TYPE 9 DATA READER 3
PARAMETERS 5
*MODE  N  TD  LOGICAL-UNIT  FRMT
-2  4  1  16  -1
*OUTPUTS 4
*HR  LSENSIBLE  FLOW1  MINOUT1

EQUATIONS 2
SNOW = [69,3]
RHOG = 0.2 + SNOW * 0.5

UNIT 16 TYPE 16 RADIATION PROCESSOR
PARAMETERS 9
*MODE  TRACK-MODE  SURF-MODE  DAY  LAT  SC  SHFT  SMOOTH  IE
7  1  1  1  43.1  4871  0  0  -1
INPUTS 7
*I  IDN  TD1  TD2  RHOG  SLOPE  AZIMUTH
9,4  9,3  9,19  9,20  RHOG  0,0   0,0
0.0  0.0  0.0  1.0  0.2  90.0  0.0

UNIT 69 TYPE 69 TSKY ESTIMATOR
INPUTS 12
*CEILING  SC(1-4)  PATM  TDP  NTOT  NOPAQ  SNOW  HOUR  TAMB
10,1  10,2  10,3  10,4  10,5  10,6  10,7  10,8  10,9  10,10
9,2  9,5
7777.0  0.0  0.0  0.0  0.0  10125.0  0.0  0.0  0.0  0.0
0.0  0.0
*OUTPUTS 3
*TSKY  PATM  SNOW

UNIT 71 TYPE 71 TRANSPIRED COLLECTOR
PARAMETERS 14
*AREA  HT  DIAM  PITCH  EMISC  ABSOR  DEPTH  EMISW  RWALL  UA
*TROOM  TBYPASS  QMAX  NITEBP
50.0  2.74  0.0009  0.01  0.9  0.9  0.08  0.9  0.489  7197.0
20.0  15.0  1000000000.0  1.0
INPUTS 11
*MONTH  HR  RAD  TAMB  TSKY  PATM  GAIN  FLOW1  MINOUT1  FLOW2
*OUT2
9,1  9,2  16,6  9,5  69,1  69,2  11,2  11,3  11,4  0,0
0,0
0.0  0.0  0.0  0.0  0.0  101.3  0.0  0.0  0.0  30000.0
0.0
*OUTPUTS 21
*TPLENUM  TOUT  TMIX  TSUP  TCOL  QSAVE  QVCOL  QVWALL  QRCOL  QRWALL
*QDWALL  QRED  QABS  QAUX  OUTFLOW  EFFHX  SOLEFF  DELP  BYPASS  QTRAD
*FANPW

UNIT 24 TYPE 24 INTEGRATOR
PARAMETERS 1
*INTERVAL
8760
INPUTS 8
*QSAVE  QVCOL  QVWALL  QRED  QABS  QAUX  QTRAD  HR
71,6  71,7  71,8  71,12  71,13  71,14  71,20  71,19
0.0  0.0  0.0  0.0  0.0  0.0  0.0  0.0

UNIT 25 TYPE 25 PRINTER
PARAMETERS 5
*STEP  START  STOP  LOGICAL-UNIT  UNITS
8760  1  8760  11  1
INPUTS 8
24,1  24,2  24,3  24,4  24,5  24,6  24,7  24,8
QSAVE  QVCOL  QVWALL  QRED  QABS  QAUX  QTRAD  HR
KJ  KJ  KJ  KJ  KJ  KJ  KJ  HR

UNIT 26 TYPE 25 PRINTER 2
PARAMETERS 5
*STEP  START  STOP  LOGICAL-UNIT  UNITS
1  1  8760  12  2
INPUTS 10
9,5  69,1  71,1  71,2  71,4  71,5  71,15  71,16  71,17  16,6
TAMB  TSKY  TPLENUM  TOUT  TSUP  TCOL  OUTFLOW  EFFHX  SOLEFF  RAD

UNIT 27 TYPE 25 PRINTER 3
PARAMETERS 5
*STEP  START  STOP  LOGICAL-UNIT  UNITS
1  1  8760  13  2
INPUTS 10
71,6  71,7  71,8  71,9  71,10  71,11  71,12  71,13  71,14  71,18
QSAVE  QVCOL  QVWALL  QRCOL  QRWALL  QDWALL  QRED  QABS  QAUX  DELP

END


Reference:

1.  Martin & Berdahl, "Characteristics of Infrared Sky Radiation in the United 
    States," Solar Energy, Vol. 33, p. 321, 1984.