RE: [EnergyPlus_Support] Blockbeamsolar

I produced the attached diagram, some time agao, to show that there are many components reaching a window. Rotating each slat, the effect of the transmitted component can be more easily visualized.

The radiation is blocked when the upper edge of the lower slat and the lower edge of the upper edge touches the line that the radiation is coming from. When the beam is coming from a high angle, the blind is open wider.

The block beam control blocks the "beam to beam" component. The blocked beam may still have a diffused component to enter the room. This is probably the reason why a 45° degree setting is a better one, because the solar angle is mostly above that angle and the diffused beam is reflected away from the building.

When the ground reflectance is at a low value, the ground reflected radiation will enter the room with the 45° setting, but at a relatively low intensity.

I usually said that the parametric method to optimize the design of a window for minimum energy would not work, because there are so many components to consider..

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: geert.bellens@xxxxxxxxxxxxxxxxxxxxxx
Date: Sun, 12 Aug 2012 15:19:12 +0200
Subject: RE: [EnergyPlus_Support] Blockbeamsolar

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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