gmolina's profile - activity

Hi! I still struggle to find the best set of parameters for lighting simulation! But, yours seem quite "high", so I wou

Hola, ¿De que programa estás hablando? ¿En que sistema operativo? (I would move to english... most people here uses t

Thanks, adambgnr, but I think I will stick to my own approach. That way, EnergyPlus will do its own calculation and ever

Shading:Building:Detailed shading more area than it should Hello everyone, I am trying to model a dynamic shading devic

Very cool, that was exactly what I was looking for! thanks very much.

Dear everyone,

I am using genOpt to perform an optimization of a shading device. This device has been parametrized, and 5 parameters have been found.

Even though all these parameters are independent of each other (they are a base), one of them is constrained to be half of another. Otherwise, the geometry does not make sense.

Accordingly, what I need to achieve is something like:

Parameter{ 
    Name    = spacing;
    Min     = 0.01;
    Ini     =  0.25;
    Max     =  2 * radius;
    Step    =  0.1;
}

Parameter{
    Name    =  radius;
    Min     =  -3;
    Ini     =  0;
    Max     =  3;
    Step    =  0.5;
}

I have not been able to get a clear understanding of constraints by reading the genOpt manual, so I have not been able to implement this.

I think I can create some auxiliary variables for solving this, but the results will be somehow complex and "unnatural", since this new variables will not really mean much in the visual part of the geometry... thus, I want to avoid this.

Thanks in advance!

Thanks very much, Chandan. That was very very helpful.... The reported values and the schedule still do not match, though.

I read somewhere that the scheduled values are used to "propagate" Radiation within the room. Is that so? That is... Solar radiation arrives to the surfaces, and then EnergyPlus calculates the solar radiation that would end up in all other surfaces due to intereflections.

Dear Everyone,

I am trying to simulate extremely complex environments using EnergyPlus and Radiance. Since I am used to use Radiance, my apporach is to

1. Calculate Solar irradiance over walls
2. Create a Schedule for EnergyPlus that will be read using the SurfaceProperty:SolarIncidentInside.

However, I am having some trouble reading the documentation. Even though its name is SolarIncidentInside, then the documentation basically says the schedule will replace the absorbed solar radiation... the units are W/m2. All cool for now.

However, when I try to report it using the Output:Variable,*,Surface Inside Face Solar Radiation Heat Gain Rate per Area,hourly;, I do not get the same value as in the Schedule... and they do not even match the values multiplied by the surface absorbtance.

Can anyone please explain this discrepancy to me?

Kind regards,

Thanks, guys! I guess this is all the information available, and seem to be enough for me. Will inform if any of this works.

Regards

Thanks very much, Michael. But what I want to do is to create an FMU from a Radiance Model ... That is, calculating the daylighting and artificial lighting levels from Solar Position, Solar Radiation and Luminaire Power.

I believe I can create a script that (1) writes a C program, (3) compiles it to create an executable that (4) would work as a block (i.e. call it with the parameters and returns illuminance levels in a scene). However, I do not know how to pack that into a FMU... is it VERY HARD? is it Possible?

Thanks very much, Michael. But what I want to do is to create an FMU from a Radiance Model (i.e. calculating the daylighting and artificial lighting levels from:

• Solar Position
• Solar Radiation
• Luminaire power

I guess what I would have to do is to

1. Calculate the contribution of the luminaires over the workplanes
2. Calculate the daylight coefficients
3. Pack that into some "magic methods" within my FMU

I believe I could make a script that (1) writes a C program (2) compiles it to generate an executable that (3) returns the lighting levels from the previous data (i.e. calculate the Sky Vector from a Perez model, multiply by DC, add the contribution of the luminaires scaled by the power)... but I do not know how to put all that into a Functional MockUp Unit.

Is it even possible?

My plan is to create "empty" (no internal loads, no HVAC) EnergyPlus FMUs and Daylight FMUs, in order to load them into OpenModelica and test different control algorithms that integrate daylighting and energy.

Am I totally lost?

THANKS!

Hi everyone,

I am working on a project that requires pretty complex co-simulation between energy and lighting software. I developed some tools for that in the past, but I would like to get the new technologies now.

I have been reading about Modelica and particularly FMUs. I think they are very cool and have a lot of potential, but I have not been able to find out how to compile one of those. Are any of you guys aware of tutorials or guides for this?

I would start by using them within EnergyPlus and/or OpenModelica

Thanks very much!

THanks for worying!

I think, Michael, that the problem was on my computer, shutting itself down because of overheating... I already fixed this, and am going to try these files again soon. I will let you know if it keeps failing.

BYE!

Thanks for your comments. I tried to use the SpreadSheet one, and it did not really work for me. I understood measures, how to script them, and that is something I mixed with GenOpt... quite easy and very powerful.

I will have a look to the spreadsheet again.

Best!

Thanks, Michael!

The error I showed before is the only thing I get in the console AND the log file. Ut just says "java.lang.ArrayIndexOutOfBoundsException: 0" after succesfully simulating the first generation, but it never gets to the second one.

Any ideas?

I will read that paper. THanks

Update: I tried the following, but got an error message ... java.lang.ArrayIndexOutOfBoundsException: 0

Main = GPSPSOCCHJ; NeighborhoodTopology = vonNewmann; // gbest | lbest | vonNewmann NeighborhoodSize = 1; // 0< ... Ignored for vonNewman and gbest NumberOfParticle = #{10n_vars}; NumberOfGeneration = 15; Seed = 12; CognitiveAcceleration = 1.5; SocialAcceleration = 1.5; MaxVelocityGainContinuous = 1; MaxVelocityDiscrete = 1; ConstrictionGain = 0.8; MeshSizeDivider = 2; InitialMeshSizeExponent = 0; MeshSizeExponentIncrement = 1; NumberOfStepReduction = 4; *

I am not sure about the exact answer, but I can tell you this: ConductionFiniteDifference march through time, solving one timestep after another, relying on the solution found for the previous and/or following instant. This 'and/or' will depend on the solution scheme used. (I guess this is controlled with difference scheme in the HeatBalanceSettings:ConductionFiniteDifference object in EPlus)

For example, you start at t=0, solve an equation and find the values for t=1. Then, use t=1 to find values of t=2.

These methods usually involve a critical timestep that assures convergence (if timestep is bigger than that, your solution will explode in plusHUGE or minusHUGE numbers). Fulfilling this criteria, however, does not assure accuracy, so it is a common practice to divide the critical timestep by some constant, and use that as the timestep in your solution. This constant, I think, has something to do with the space discretization constant in the HeatBalanceSettings:ConductionFiniteDifference object in EPlus.

CRITICAL TIMESTEP IS SMALLER IF YOUR MATERIALS ARE LIGHT (it is actually a relationship between thermal mass and conductivity --> thermal diffusivity)

Finally, (and here I am guessing) if you have some "light" materials (i.e. plywood, gypsum boards) the critical timestep might be smaller than what you asked for EVEN IF THE MATERIAL IS NOT SUBDIVIDED, thus forcing EnergyPlus to ignore the input option and making it 3 minutes or so.

I would love to know if I am correct.

Hello everyone,

I am playing around with optimization of OpenStudio models using genOpt. It all has been working OK when optimizing Insulation thickness and WWR and overhangs, but now I want to try some discrete variables (i.e. number of glazing layers in windows)... discrete variables are bothering me. I have been reading the genOpt manual and Literature, but I am still not sure of anything.

So, I wanted to know what algorithms do you recommend for optimizing a building design, using EnergyPlus (OpenStudio) including continous and discrete variables.

I understand genetic algorithms CAN do this... but I am kind of skeptical to those 'magic' things. What about them?

THANKS

Hello,

I am trying to use genOpt on an Intel i7 with Ubuntu 14.04. The GUI actually says that all 8 threads are assigned to genOpt, but my resources show that only one is in use.

What am I doing wrong? I also tried to run it without GUI, but nothing changed.

Algorithm{ Main = GPSCoordinateSearch; MultiStart = Uniform; Seed = 12; NumberOfInitialPoint=8; MeshSizeDivider = 2; InitialMeshSizeExponent = 0; MeshSizeExponentIncrement = 1; NumberOfStepReduction = 4; } ```

I guess you would have to make a difference between "tools that allow you to quickly create models" (i.e. OpenStudio for EnergyPlus/Radiance and SU2RAD or Groundhog for pure Radiance ) and "tools that advice on what the design should be" (I am not aware of any of those that is currently in development or use... I heard of a few, though, some years ago)... I guess you will find more of the first kind than of the latter, and I think this applies to all design-related fields. For example, if you want to design a bridge, you make a proposal of how the steel might be arranged and then perform a structural analysis to see if your proposal was good (I understand that is how it works today).

I had this discution a few times in my last job. They always told me that the last advisor they had relied only on a highly educated common sense to make proposals and design alternatives. I believe that most of the people actually do that. However, building simulation tools allow checking if a design proposal is good or bad (just as the structural engineer designing a bridge) and also adding numbers to the analysis (i.e. everybody know that a lower WWR lowers the Solar Heat Gains and increases the insulation of the building... but, how much? what would be an appropriate WWR in this particular case?).

Long story short, I do not believe that any tool, nowadays, can "advice" very well on building design. However, there are tools, like the CLIMATE CONSULTANT that help getting an overview of the weather from a Weather File. This information is a very valuable input for your design process.

At least this would be my approach... first, study the weather; second, study the building requirements (internal loads, etc.); third, study the site available (size and shape, surroundings); fourth, use a tool that allows me quickly creating and evaluating design alternatives (i.e. OpenStudio and Groundhog).

Long post... sorry. Regards!

Thanks, Dan and David.

I did not fully undertand the available documentation on Large Scale Analysis... however, I think I am already learning how to do it using Ruby scripts. It is kind of tricky at the beggining, but I am learning.

Bye!

Hello,

As far as I understand (I do not really use DIVA) it is not currently possible to use BSDF information in any Daylight Coefficient implementation (i.e. Daysim, DIVA). This is because of the method used within Radiance to perform the Daylight Coefficients calculations... something I do not really fully understand.

I have read things that make me think that "they" are working on an implementation of the 5phase method that should enable using BSDF within DIVA/Daysim... I am just gossiping, though.

As I mentioned before, I do not really use any of those programs (I usually use pure Radiance), but this is what I understand from the methods underneath.

Regarding any other options, Radiance or OpenStudio 3phase method allow using BSDF information, but I would not advice that if your BSDF is very specular.

Bye!

Hello everyone,

I have been learning OpenStudio for the last few days and I think I am finally understanding the whole idea. It is great! thanks for making it possible.

Anyway, I have been trying to figure out how to implement a real Optimization algorithm using OpenStudio. I mean, I know that PAT can actually run A LOT of simulations, but I am not sure I like the "randomness" of how measures are impleented (or I think they are implemented)... it seems to me that the "lets run all these models, and see what happens" approach can be enhanced.

I am thinking on something more like "lets apply these measures, run a simulation, check the results and then figure out what the next measure to try should be". Does that make any sense to you guys? Is it possible to do that from PAT itself (can it be scripted or something?) Is it possible to do it from Command line (Terminal) from the existing binaries?

#this kind of code is what I am picturing

seed_model=load_osm("seed.osm")

measure_1=load_measure("measure)

iteration_1=apply_measure(seed_model, measure_1)

results_1=simulate(first_iteration)

measure_2=figure_out_next_measure_from_results(results_1)

#repeat for iteration 2 with measure 2

THANKS VERY MUCH, I may be speaking nonsense, but I think OpenStudio is not far from allowing this, if it does not already does.

Hi there,

I also use OSx for simulation, but have never used the ep launch. What I usually do is to start the simulation from the command line. That is, you open the terminal (command line), go to the directory where your IDF is placed, and write

'runenergyplus name.IDF weather.epw'

Of course, replacing "weather" and "name" by valid files

Not sure if you need to add this script to the path (as Radiance and other tools require)

Hope it helps!

Thanks for the Advise, everyone. I found the main problem: Ventilation values for sizing and simulation were different. I guess the temperatures being correctly in the sizing periods was just "luck".

Now, I see that the unmethours is still high... That, I assume, is because the Design Days are not the "actual peaks".

THANKS

Hi everyone,

I am using EnergyPlus 8.2 in Ubuntu for performing a series of simulations of a building located in Lima, Peru. Since my intention is to compare a reference and a proposed model (i.e. ASHRAE 90.1), there are two models: one with almost everything autosized, and the other with nearly everything predefined (except those values not clearly specified by the HVAC engineer).

Anyways, both models run Sizing:Plant and Sizing:Zone calculations, and there seem to be no important errors in the *.err file (only a few convergence ones... the system corresponds to System 8 on Appendix G: VAV PIU with Reheat).

When simulating the sizing periods (i.e. winter and summer design days) every conditioned zone's temperature lies between setpoints (21 and 24 °C); so I assume Sizing is being done correctly. However, when simulating the whole year, the results show about 3000 unmet hours, using a tolerance of 0.55°C. This happens with both the proposed and reference building.

I, honestly, do not know what to check anymore... any suggestions?

THANKS VERY MUCH IN ADVANCE! HAPPY HOLIDAYS!