[00:00:00] In the last video, we set up our thermal zones with ideal air loads and in this video, we’re going to run our first EnergyPlus simulation.  This is a debug run to check that the basic setup of the model is correct and ready to go before we add a more detailed HVAC system.  So we have a few things to set up before we simulate.  From the Zones page, we’re going to skip the Detailed page and go to output variables.  I’m going to turn all of these off and then let’s go through this list and select the output variables that are going to be useful to check that our model is running sensibly.  Now what are those?  Those are going to be things that tell us whether we’ve set up our loads correctly and whether the temperature inside the spaces is within the target bed.

[00:00:57] So let’s turn people occupant count on.  That tells us how many people in each zone.  Let’s go through the list and select a few more.  Zone air system, sensible cooling rate.  Likewise for heating.  Zone air temperature.  Zone electric equipment power.  Now we want lights and infiltration.  There’s our infiltration air train track and we just need the lights.  Zone lights electric.  Now energy’s never on but power is what I want.  So those are all the output variables that are available and useful at this point.  What you will find is that this is a fairly short list.  If it’s not on this list, we can’t add it with this page.  However, we can add other output variables and in this video, I’ll give you a sense of how that’s done and then I’ll show it to you in the following video.  So that’s all the output variables that we need from this page and next we’re going to jump to the simulation settings.

[00:02:14] Here on this page, we can select the date range, so we’re going to go for a full year from January through December.  We can set our heating sizing and factors, cooling sizing factors.  We want six times per hour.  That’s the EnergyPlus best practice guidance.  Now simulation control.  We want to do zone sizing.  We don’t want to do plan sizing.  We don’t want to run for the simulation sizing periods, which is the design days.  If you do do that, it just gets a little annoying.  You get these ten output periods that are just not particularly useful for our purposes in this case.  The system sizing is not necessary.  Again, we’re just running ideal air loads so there’s no HVAC system to size.  And that’s also why I turned off the plan sizing.  Warm up days.  For a good simulation, you really do need to warm up the building before you start counting.  That’s everything we really need to cover here on the simulation control.  I won’t go into too much detail here at this point.

[00:03:15] Now measures.  On the Measures page, we can add a measure that allows us to add additional output variables.  That’s one example of what we could do here.  Another example is the reporting.  So what we make use of is the built-in OpenStudio results report.  Now that you can see under this list here but that’s also built into the OpenStudio and that’ll give us a summary report of all the useful information from the simulation.  We can customize that report and perhaps even create our own custom report and we can drop that into a corresponding part of the page here.  That gives you a sense of what you can do here on the Measures page.  For now, we’re not going to add anything, but in the following video, I’ll show you the Add Output Variable measure.

[00:04:12] So now we can go to the Play button and fire off the EnergyPlus simulation.  OpenStudio will then fire up EnergyPlus and it’ll bring back the output from that EnergyPlus simulation as it progresses and tell you how it’s progressing.  It’ll give you any sort of information about whether it’s failed and why it’s failed.  So as that’s running, what I’ll show you is what happens at the tree level.  On this Tree tab, it shows you the expansion of the OpenStudio file to the IDF.  Now this tree is actually a summary of the folders and files that are being created by the OpenStudio run.  Now to give you a more direct view of what’s happening there, let’s go to the working directory and within that Video8 file that I’m now simulating, we can see a number of folders have been created.  There’s first of all a Files folder, and within this is the EnergyPlus weather file that we’ve associated with our simulation.

[00:05:20] Within the Run folder is a number of subfolders and this shows what OpenStudio is doing.  So it expands the model to an IDF, then it expands any objects, then it runs any user scripts, any preprocessing and then within step four here, that’s the guts of EnergyPlus simulation.  This is where the input and output for the actual EnergyPlus simulation run is contained.  Two things to draw your attention to here.  First of all, the .err or error file, and second of all, the Output Variable Dictionary which has the .idd extension.  We’ll come back and have a look at those.  Once the simulation is finished, we’ll all see an EPlus table file.  So here’s an .html file that just popped up as I was speaking, and that’s the EnergyPlus results summary report.  So I know the simulation has now finished successfully because that’s been created.  So let’s go back to the OpenStudio output and we can see that the green bar has gone across to 100% and there are 44 warnings and zero errors.

[00:06:32] Now the step I recommend once your simulation is finished is each and every time your simulation finishes, you should have a look at the error file.  So opening up that error file, you know, in this case, just a Notepad and we can have a look through the warnings that have been created.  So here we see something about one of our schedule type limits, control mode in invalid.  That’s a warning, it’s not particularly important, and if you’re worried about what the means, you can go into further detail.  Here’s another example: it’s looked for something called “gas facility” and it hasn’t found it.  So it’s looking for a meter with a name of “gas facility” and it hasn’t found one, and in this case it’s because we’re running ideal air loads, we’re not consuming any gas.  So it’s not producing any metered output about the gas and so it hasn’t found it.  That’s the kind of information you’ll see here in the error file.  And then the important part is right at the bottom that says there are 12 warnings, zero severe errors so you’re good to go.

[00:07:41] Now let’s have a look at the results.  So we go to the last page in the icon  here and we see OpenStudio results.  First of all, let’s look at the zone conditions.  Here in the zone conditions, we see a summary of what temperature the space has been at over the course of the simulation period.  So for each zone, in this case, in the admin office zone, it tells us how many unmet heating hours there were.  So there were zero unmet heating hours.  We also see zero unmet cooling hours.  Now between those two, it tells us that there were 2,208 hours between 74 and 76 degrees Fahrenheit.  So this zone conditions summary table tells us whether the energy model is successfully holding the temperature we desire in each zone.  And to me, that’s the first thing to check once you’ve run an EnergyPlus simulation.  You want to make sure that the conditions that you’re expecting to maintain within each zone have been maintained by the way that you’ve set up the simulation.

[00:08:54] So that’s the zone conditions report.  Next, let’s have a look at the HVAC sizing summary.  So to do that, we go to the EnergyPlus results.  Let’s go to the table of contents and let’s have a look at the HVAC sizing summary.  Now it’s called the HVAC sizing summary, but what it really tells me, which is more fundamental than HVAC, is the amount of cooling required in each zone.  So here we see the user design load per area.  So we see 38 watts per square meter of cooling is required at the peak condition in that admin office.  And we can see that watts per square meter cooling requirement for each of the zones.  Now that’s a useful number because in my mind, there’s a number that says, “For your local climate, we’re going to need roughly X watts per square meter of cooling in each zone, whether it’s perimeter or internal.  And that tells you whether you’ve set up the basic structure of the model such that you’re getting sensible numbers out.  So that’s the zone cooling and if we scroll down, we see the zone heating table likewise.

[00:10:06] Next, let’s have a look at the energy end use intensity.  We’ll go back to the table of contents and source energy and used components summary.  This is broken up in a few different ways.  First of all, there is the annual numbers given in gigajoules and then we see it normalized to the conditioned floor area, so here we have mega joules per square meter.  This table breaks down the energy use for the building into different components.  So we see 455 mega joules per square meter for heating and 90 mega joules per square meter for cooling.  So this table is a very useful one for comparing different HVAC option.  Now that’s the whole idea of the course, so what I’d like to do at this point is just grab a copy of this table and I’m just going to hold down the left mouse click and select that table and I’m actually just going to use Control C on the keyboard and I’m going to dump that into a very straightforward summary spreadsheet that I’ve created for this purpose.

[00:11:23] So there’s a summary table and this chart that I’ve created is going to basically chart the difference between the three cases that we’ll run.  Don’t be concerned about the spreadsheet being complicated or difficult to create yourself.  I’ll make this available to download with the course and it’s a very straightforward sort of a spreadsheet.  So that table that I’ve copied to my clipboard I’ll now paste onto this page, and when I come back to the results comparison, that’s updated the table and the chart and that’s just very simply linked this cell to this cell here.  So nothing too fancy going on there.  And that summarized the heating, cooling, interior lighting, and interior equipment for that ideal air loads case.

[00:12:16] So that’s a nice way of summarizing the energy end use intensity.  That’s everything we want to cover in this video.  In the next video, we’ll go on to replace the ideal air loads with a package terminal pump and we’ll again go through the zone conditions and the energy end use and begin to make some comparisons between different HVAC options.