[00:00:00] In the last video, we set up our energy model with ideal air loads and ran our first simulation successfully.  In this video, we will move onto the HVAC Systems page and add a packaged terminal heat pump to each of the zones in the model.  So let’s dive into the HVAC systems page and what can we see here and what can we do here?  On the central area of the page, we see a service hot water plant loop.  So that’s empty at the moment.  We can switch to the refrigeration page.  Again, that’s empty.  And there’s also a VRF page.  So this drop down area on the top right of the page allows us to navigate between the different plant loops that you can configure and create here on the HVAC Systems page.  What we want to do here is from the green + button, add an HVAC system.

[00:01:02 ] So pressing on that Add HVAC System button will open up the selection drop down dialogue box here, and this shows all the template systems that come with the OpenStudio software.  There’s a packaged rooftop unit, there’s a packaged rooftop heat pump.  You’ll see a package rooftop variable air volume with reheat.  We’ll go into this system in the next video.  And at the bottom of the list, you’ll also see an empty air loop and an empty plant loop and it’s from these empty loops that you will be able to start from scratch and create your own custom HVAC system.  So what we’ll do here is select the packaged rooftop unit and click Add to Model.  This creates an air loop here in the model and we see that here in the main page and we now navigate through the different sheets or plant loops and the packaged rooftop heat pump is one of the plant loops that’s now defined in our model.

[00:02:13] Now the name of that is not particularly helpful in my opinion because what you don’t really recognize from the name of that this is that it’s an air loop.  So if you hover your mouse on the Supply Equipment/Demand Equipment sort of main area of that loop, it throws open the Edit view on the right hand pane here and you can see by the type of object that it’s an OpenStudio air loop type object.  So let’s rename that just to make the point more clear, and in renaming that, we can also see that the name’s updated in this drop down area.

[00:02:56] So what kind of system are we looking at here and what has OpenStudio created for us?  Well it’s an air loop.  It’s got a number of components on it.  There are two sides to the air loop.  There’s the supply equipment side, which is the top half, and the demand side, which is the bottom half.  On the supply side of the loop, there’s an outdoor air system and this is where the return air escapes to the outdoors and where the outdoor air can enter into our system.  There’s a cooling coil, a heating coil, supplementary heating coil, a constant volume fan, and a set point manager.  On the demand side, we see an air terminal and we see this node.  Now this node is where we can drop a thermal zone onto the system.  So let’s do that now. 

[00:03:45] Under My Model, expand the Thermal Zone section.  Now let’s drop the admin office adjacent to the air terminal.  So that zone is now controlled or conditioned by this packaged rooftop air pump unit.  So that’s the method for adding a PTHP to each of the zones that you want to condition with that kind of system involved.  Now if you wanted to do that for each of the 20-odd zones, it would become a little bit tedious and it would also be air-prone.  You know, you’re pretty likely going to make a mistake or two along the way in doing that.  You know, it might just be a small mistake such as naming it incorrectly or trying to add the same zone twice.  So rather than doing it manually, we can simplify that task by looking for a measure to do that job for us.

[00:04:42] So from the Components and measures menu, let’s go and find a measure to do that job.  So we’ll click on Find Measures and we’ll make our way to the Building Component Library.  Expand the HVAC category and let’s browse through the whole system category within that HVAC Systems.  Now I know that it’s on the last page but there’s a few others I’d like to sort of show you while we’re navigating.  Here’s one for Enable Ideal Air Loads for All Zones.  On the second page, there’s another one that could help you to add a system type seven.  And here on the third page, we’ll find Add a Packaged Single-Zone Heat Pump to Each Zone.  So put the tick in the box there and download that and that will make that measure available to use in your OpenStudio software.

[00:05:38] While we’re here, I’d like to show you two other useful measures.  Under the Reporting category, let’s go to Quality Control.  Now what we’re looking for here is the Add Output Variable measure.  This allows us to extend the list of output variables that we can add to the OpenStudio model.  What I’ll show you in a moment is how to add a particular output variable for the packaged terminal heat pump unit.  So we’ll need to add this output variable measure to our OpenStudio software.  There’s another one I’d like to grab, and that’s the zone report.  Here on the second page, you’ll find one and it’s called zone report.  Grab a copy of that as well and we’ll use that to create sort of a more mechanical engineering type report for each of the systems on each of the zones.

[00:06:39] So now we’ve finished grabbed those measures that we need.  Let’s go back to the software and what we’ll do is use this button called Apply Measure Now.  It’ll prompt you to save your model so I’m going to do a File, Save As at this point and I’m looking to save this as Video10.  And we’re going to now apply the HVAC whole system.  We want to add a packaged single-zone heat pump to each zone.  So this measure takes a few arguments.  First of all, do we want to delete any existing HVAC equipment?  So I’m going to tick the box to say yes and that’s going to remove the system that I’ve just added to the model.  We can apply a COP or coefficient of performance for cooling and for heating.  Let’s select the fan type as the default constant volume fan.  And how do you want to choose the affected zones?  And I’m going to select By Zone Filter.  What this’ll do is look through the name of each of the zones and if it finds the word that I put into this field, in this case, if it finds the word “thermal” in the name of a zone, then it will apply a packaged terminal heat pump to that zone.

[00:08:04] So each of my zones has got the word “thermal” in its name so the zone filter will pick up that word and apply the packaged terminal heat pump to that zone.  So that’s exactly what I want to do.  You could also apply it by space type, so if you wanted to, select By Space Type and then for example, you could apply it to all of the open office areas, for example.  But in my case, we’ll do zone filter and filter by the word “thermal.”  So let’s apply that measure now.

[00:08:43] That’ll take a moment to think about it and then it returns some information on what it’s done.  So it’s deleted one existing air loop and it’s added a number of air loops.  It’s added 27.  So we’re going to accept those changes.  Now if you think on that for a moment, it’s added a packaged terminal heat pump to each and every zone in the model, which is nonsense.  We don’t want to condition our stair for example.  So I’m going to delete that one.  I’m also going to delete that stair.  There’s a couple more stairs I think.  Delete from that stair zone, that stair zone.  And I also want to remove the conditioning from the restrooms.  So that just tidies up a little bit and that’s a bit more of a sensible approach to the HVAC strategy.

[00:09:40] Now looking at this system, you might have some questions.  You know, you might want to know, “What am I doing here?  What kind of system have I put in there?  And if I pop the hood and looked at the EnergyPlus definition, what exactly am I looking at there?”  And if you’ve got those sorts of questions, the best place to go to is here on the bigladdersoftware.com help site.  I’m just going to close that because it’s in my way.  So here at Big Ladder Software, they’ve taken all of the EnergyPlus help files and they’ve put them online which is a really fantastic service.  And if you search through that, you can get more information on the type of system you just added.

[00:10:21] So we’ve just put a packaged terminal heat pump system into our model and that should be here on this page that I’m scrolling through.  I’m just going to scroll up to the area that’s interesting.  And it’s unfortunately a not very nice way of looking through the info because there’s just so much there and it takes quite a while to load it all into the browser.  So I’m just going to go to this link that I’ve prepared here.  So here on the bigladdersoftware.com website, they’ve made all of the EnergyPlus help documentation available.  I’ve navigated my way to the packaged terminal heat pump input/output reference, and here we see a schematic of the HVAC system we just added.  The other useful thing that we can get from this documentation is a list of the available output variables.  Just scrolling down through this list, we come to the – here we see the definition, the IDF, of the object and there’s a few other bits and pieces of the group that get defined along with it.  And here we see the outputs.

[00:11:57] So what I’m interested in is how much electricity that unit is consuming.  So let’s copy this zone packaged terminal heat pump and electric power.  I’m going to just copy that and let’s go back to OpenStudio and let’s add that output variable through our measure so that we extract that information from the simulation.  Again we’re going to use the Apply Measure Now functionality.  We’ll save that and from the reporting [INAUDIBLE 12:27] we select the Add Output Variable and we enter the name of that output variable that we’re interested in to that input field and apply measure.  So that adds the output variable that we’re interested in to the OpenStudio model and that means we can extract that information when we run the simulation and we’ll be able to understand how much electricity each of the PTHPs is using in the time series data.

[00:12:56] So we’re now kind of set up the HVAC system the way we want it and I’ve also showed you how to grab a couple of measures that are useful to help do that so we’re ready now to simulate.  Let’s just fine-tune the simulation control settings and we want to do plant sizing and do system sizing.  And let’s run the simulation.  So the EnergyPlus simulation’s now completed and the first thing we should do is check the air file.  Looking at the air file, we see a lot or warnings.  This is related to a frost warning on the cooling coils and the heating coils, which could indicate a problem with unmet heating hours.  So we see a very large number of warnings, but none of them are severe.  So the simulation is completed successfully but it may indicate a problem with of the assumptions that we have on the sort of mechanical nature of the equipment and you would want to look into those in more detail to understand if the settings on the packaged terminal heat pump are correct for the climate that you’re in.

[00:14:34] But for output, since we’re going to go ahead and look at the next stage of the results.  So let’s go to the results summary and first of all, we’ll look at the zone conditions.  So here we see there are about six unmet heating hours in the admin office.  This corridor zone, which is a real problem in the model, has got about 39 unmet heating hours.  Again, the corridor lobby has got about 35.  That, in my opinion, is largely to do with the way that we zoned the model which has got a number of different orientations to it and it’s quite a large space so the zoning of that space is really part I think of the issue with the unmet heating hours.  In terms of unmet cooling hours, we see that there are zero for all of them, so that system is working reasonably well without having done – you know, out of the box, it’s doing a pretty good job.

[00:15:32] So let’s have a look at the EnergyPlus results, and from the table of contents, we’ll go straight to the source energy and use components summary.  I’m going to do what we did in the previous video, which is just to make a copy of this table.  Control C on my keyboard and I’m going to dump this into this little comparison spreadsheet I’ve made for the purpose.  I’m going to paste that in there and it should bring across the key results to this table.  So here we see about 235 mega joules per square meter for heating, around 105 for cooling.  The interior lighting and interior equipment are the same and it’s the ideal air case and we were also using additional energy for fans which weren’t in the ideal air loads case.  So that’s straightaway quite a nice sort of comparison between your benchmark, which is the idea air loads case and your packaged terminal heat pump unit.  You can take confidence from the fact that your interior lighting number is the same and your interior equipment is the same.

[00:16:40] Now it’s interesting to note that the heating number in the idea air case is much higher than it is in the package terminal heat pump case.  Now that’s to do with your coefficient of performance where the ideal air loads case is I think a much lower heating COP than the packaged terminal heat pump is.  So there’s an efficiency there that translates into less energy consumed for the PTHP.  But that’s not really the comparison that we’re interested in between these two.  The comparison that we are interested in in this exercise is between the packaged terminal heat pump system and the variable air volume system.  So in this video, we’ve created the packaged terminal heat pump system in our model and in the next video, we’ll go on to replace that with a variable air volume air handling unit setup and then we’ll come back to this comparison sheet and see how the energy compares between those two different HVAC options.

[00:17:37] So in this video, we’ve shown you how to add a packaged terminal heat pump system to your model, we’ve shown you how to grab measures that are useful from the Building Component Library, and we’ve always shown you how to add additional output variables to your simulation to extract the more fine-tuned information about how systems are operating under the time series data.  So in the next video, we’ll go on to replace the PTHP with a VAV system.