I think, these minor time shift and averaging appears with other variables as well.
For example, the outside dry bulb temperature listing at the output is unchanged at the hourly points when using timestep as listing interval (same as the EPW hourly value). When listed as in a hourly interval report, the value is the average of the preceding hour, which is slightly different from the original list value in the EPW.and is the same as the half hour points of the time step listing.
I have a feeling that this is done by the post processor using the ESO in time steps, and not at the simulation time.
Date: Sun, 31 Jan 2010 20:06:15 -0500
Subject: [EnergyPlus_Support] diffuse solar
Hi, allIn EnergyPlus, when timestep = 4, the diffuse solar in weather file is different from the output at the same hour. For example, in weather file, at 9:00, the diffuse solar is 58, while in the output, 58 appears at 8:30. This rule seems different from interpolation mentioned in help ref.In calculating Daylight Factor, EP ref. mentions it uses hourly DF and then interpolate the two hour DF to calculate the DF at time step in one hour. So when calculating Daylight Factor, the Energyplus adopts which hour values of Diffuse and direct Radiation in the Outputfile? Does EP use 58 (at 8:30 in the output), or use value at 8:00 in output (average values at 7:30 and 8:30, which are corresponding to 8: 00 and 9:00 in the weather file respectively) ? .Thanks in advance,jia
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