[TRNSYS-users] Type 34 - Wrong calculation of beam fraction ?

[Marko Brandes]

Hello TRNSYS users,
using Type 34 (overhang and wingwall shading) with long extensions I ran into strange results.

>>> The scenario: <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
- Receiver: H = 1m / W = 1m / receiver azimuth = 0 (south)
- Overhang: depth s = 1m / gap d = 0 / extension left e1 = 2m / extension right e2 = 2m
- Wingwalls: none

>>> Expected results for beam fraction: <<<<<<<<<<<<<<<<<<<
The output beam fraction should be only dependent on receiver an overhang geometry, so the results should look like:
- sunrise: starting close to 1, continuously falling
- noon: lowest beam fraction (max. beam shading)
- sunset: continuously rising, ending close to 1

>>> Results from Type 34 for some test data <<<<<<<<<<<<<<<<
|row	|hour	|zenith	|azimuth	|beam fraction
1	6	87,5		-93,5		0,000
2	7	85,2		-88,3		0,791
3	8	76,2		-76,2		0,366
4	9	67,6		-63,2		0,086
5	10	60,0		-48,8		0,124
6	11	54,1		-32,4		0,142
7	12	50,5		-13,9		0,149
8	13	49,8		5,6		0,151
9	14	52,2		24,7		0,146
10	15	57,2		42,0		0,134
11	16	64,2		57,2		0,106
12	17	72,4		70,7		0,164
13	18	81,3		83,1		0,615
14	19	87,5		91,1		0,000

>>> Conclusion: <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
Have a look at row 4 and row 5: Type 34 calculates a rising (!) beam fraction even though the turning points for zenith and azimuth are not reached yet.
Furthermore the beam fraction rises aftwerwards (less shading) until 1 p.m. This is even more disturbing as shading should increase with falling zenith angles.

Can someone confirm this or knows what is wrong here?

Greetings from Berlin

BLS Energieplan GmbH
i. A. Marko Brandes

Elsenstraße 106
D-12435 Berlin
Tel.: +49 30 53 32 81-0
Fax: +49 30 53 32 81-40
____________________________________________________
BLS Energieplan GmbH
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