Dear all,
?
We are working on a project in which we measured the actual global solar horizontal radiation through out an year. Can we know the direct normal and/or diffuse horizontal radiation from the available global radiation value.
Upon changing the global radiation, we haven't found any effect on the energy consumption of a building which is modeled?in Designbuilder and EnergyPlus using .epw weather file. Does global horizontal radiation have?any affect in energy simulation, if yes, please let us know the output parameters which are affected by this variable?
?
Thanks and regards
Aviruch Bhatia
Role of Global Solar radiation in Simulation
Mar 20, 2009
Hello Aviruch,
Yes, there are models available for estimating the separate components of direct and diffuse when the horizontal global is known. An initial question on this would be: did you do measurements of hourly values or daily? I have a rudimentary model that I am willing to share with you that separates hourly global into direct and horizontal diffuse. (The algorithms are written in BASIC and FORTRAN.) Some recent work on this has also been done by the ASHRAE technical committee (TC-4.2, Climatic Information) that you can likely get access to.
On the second question, because all solar radiation will impact a building's energy consumption, it will also be a noticeable factor in the building's energy simulation results. You should be seeing effects on both cooling and heating loads, or, if you are examining strictly passive measures, you should be seeing effects on the building's internal temperatures.
Regards,
Larry O. Degelman
Aviruch,
There are a number of models that estimate the split between direct and
diffuse radiation, mostly based on the KT (ratio of the global radiation
to the extraterrestrial radiation). The simplest and perhaps easiest to
use model assumes a Gompertz function. Attached is a paper by a
colleague of mine who's applied this model to measured data for Asian
locations.
Joe Huang
Dear Larry,
Thank you for the reply.
Yes, we measured the hourly global horizontal radiation for a year. It would be so great if you can share the algorithms developed. We will also go through the information which ASHRAE is providing in this regard.
We took a existing weather file and we changed the global horizontal radiation value (also tried with an option making this value zero through out the data) and used this modified weather file to run a model in Designbuilder and Energyplus. We couldn't find any affect of global radiation on the energy consumption of the building.(A building with HVAC system)
Wanted to confirm whether Designbuilder and Energyplus use global radiation value of the weather file in the? the simulation.
Thanks & Regards,
Aviruch Bhatia