Thanks Wouter.
I had the impression that nothing could beat a fixed 45° slat, but the question came from a client who had a proposal to change the slat angle with the sun .
I couldn't confirm this for cooling load. But if I understand well, this is correct.
--
Met vriendelijke groeten,
Geert Bellens
Van: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] Namens Wouter Beck
Verzonden: 12 August 2012 17:41
Aan: EnergyPlus_Support@xxxxxxxxxxxxxxx
Onderwerp: Re: [EnergyPlus_Support] Blockbeamsolar
Geert,
Block beam solar just blocks direct beam solar radiation on the window.
For a south oriented facade, block beam solar can be achieved for normal Venetian blind geometries by leaving the blind essentially open (slat angle phi_b = 90 deg or close to that) during a large portion of summer. This depends of course on such parameters as latitude, slat width and slat pitch.
Depending on the reflectivity of your slats, a significant amount of solar radiation reflected by the slats may still enter your zone.
In these cases a fixed slat angle of 45 deg will certainly reduce solar heat gain much better than the block-beam-solar angle.
Block-beam-solar is not optimal in a the sense of solar heat gain reduction. If you look at daylighting or view through potential, block beam solar is one of the strategies to consider.
Best regards,
Wouter Beck
On 08/12/2012 03:19 PM, Geert Bellens wrote:
Of course I look at the detailed results.
The blind is outside the window.
What surprises me is that the hourly results from "Window Transmitted Beam Solar" are higher due to te BlockBeamSolar function.
I would expect that this value should be lower as a result from the optimal slat angle.
I've simulated a dozen variants, each time with a different default angle and different min and max angle.
With a fixed angle I have 67 kWh/m² cooling load. Every other simulation with the BlockBeamSolar function gives me results between 84 and 92 kWh/m².
Geert
Van: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] Namens YuanLu Li
Verzonden: 12 August 2012 13:51
Aan: EnergyPlus_Support
Onderwerp: RE: [EnergyPlus_Support] Blockbeamsolar
I think you are one of those user who does not look at the detailed timestep values.
If the blind is inside the zone, the beam is blocked, but the heat and the diffused component may increase.
IF you mount the blind outside, you may get a different result.
The heat through the wall is also changing when the son moves. Therefore, averaged value such as cooling load will not give you a true picture.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: geert.bellens@xxxxxxxxxxxxxxxxxxxxxx
Date: Sun, 12 Aug 2012 08:10:00 +0000
Subject: [EnergyPlus_Support] Blockbeamsolar
Using blockbeamsolar to simulate a sun protection automatically moving with the angle of the sun, I get strange results.
The best result apparantly is to put the angel of the sun protection always at 45°.
Using the Blockbeamsolar function, which follows the sun, cooling loads get worse. I would expect the opposite. Or am I missing something....?
Geert
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