[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [EnergyPlus_Support] Summer Design Day -- Direct Solar Radiation Calculation



Hi Linda,

Yes, the Direct Solar radiation is interpolated linearly based on each xx:30 calculation. I put my analysis results. The red ones are E+ calculated results, and any data between two red cell is linearly interpolated. The question how the red cell is calculated. If we apply Clear sky model EDN = A / exp( B / sin(beta) ), E+'s result doesn't match with this equation.

So the problem might be the:
1) Direct Solar E+ output is not EDN but a part of it. (a sin or cos fraction)
or 2) E+ doesn't use EDN equation.

Brent, if we multiply Direct Solar another sin(beta), we will get some strange results in the morning time since when beta angle is very small in morning, the multiply will give a very small solar number, smaller than E+ results. We can test this by using my copied data at 6:30am.

So, the question how E+ calculate the red cells.

        Time                                                       Direct Solar [W/m2]  Hand Calc EDN [W/m2]  angle beta [deg]
 07/21  05:00:00 1.029241551 4.043344 1.9035213
 07/21  05:15:00 1.543862327 95.27744 4.3720704
 07/21  05:30:00 2.058483103 231.8478 6.8894213
 07/21  05:45:00 101.5593178 352.0787 9.4502428
 07/21  06:00:00 201.0601525 448.4016 12.049462
 07/21  06:15:00 300.5609872 524.7024 14.682215
 07/21  06:30:00 400.0618219 585.66 17.343797
 07/21  06:45:00 458.2456969 634.9998 20.029602
 07/21  07:00:00 516.4295719 675.466 22.735063
 07/21  07:15:00 574.6134468 709.0551 25.455574
 07/21  07:30:00 632.7973218 737.2292 28.186416
 07/21  07:45:00 660.8134207 761.0732 30.922652
 07/21  08:00:00 688.8295197 781.404 33.659015
 07/21  08:15:00 716.8456186 798.8455 36.389766
 07/21  08:30:00 744.8617175 813.8806 39.108517
 07/21  08:45:00 760.0646187 826.8877 41.808008
 07/21  09:00:00 775.26752 838.1665 44.479828
 07/21  09:15:00 790.4704212 847.9565 47.114053
 07/21  09:30:00 805.6733224 856.4505 49.698783


--
Best Regards

Kelvin Feng


On Thu, Jul 23, 2009 at 7:14 PM, Linda Lawrie <linda@xxxxxxxxxxxxxx> wrote:
 

The solar values are actually interpolated around the "half-hour", but I don't think that is well documented in the documentation.






__._,_.___


The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

EnergyPlus Documentation is searchable.  Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.



Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___