I am trying to simulate a mixed mode model, naturally ventilated and conditioned, in Honeybee 1.4. But I need some of your help to deal with this because I don’t know how to configure it.
I have configured the natural ventilation control as shown in Figure 1. But now, there is an easy way to tell de Idealloads to turn On when the interior temperature is outside the range of natural ventilation and the windows are closed? My Set Points are configured 18°C and 23°C.
I currently have the model configured to open and close the windows based on the inside and outside temperature. Do you say that I should use another schedule to open and close the window? But how do I link it with the HVAC on and off?
Just design your natural ventilation parameters such that windows close whenever natural ventilation can’t maintain the setpoint range. Then you don’t need to any additional logic for your HVAC system, it’ll automatically turn on when windows are closed and the interior temperature falls outside the setpoint range.
You can ensure windows are closed when the HVAC system is on by aligning your interior ventilation setpoints with your HVAC setpoints, i.e. set min_in_temp_ and max_in_temp_ to around 18C and 23C, respectively.
Hi @SaeranVasanthakumar, thank you very much for your suggestion, sorry for my delay.
I am having some problems with this solution. I set the natural ventilation as shown in Fig. 1. And the SetPoits are defined as Fig. 2. But something is wrong because HoneyBee is opening windows and using heating and cooling throughout the whole year. As the balance plot shows in Fig. 3, obviously something is going wrong because natural ventilation is greater in winter than in summer. In winter the room needs a big amount of heating energy but at the same time is using natural ventilation. Of course, this is not logical, since in winter we should not open the window and turn on the heating. And on the other hand, the balance shows that in summer use some heating, another illogical result.
I take a quick look at the results in excel. It is clear that something is wrong since is considering the window opened at the same time that is using heating as shown in Fig. 4.
Fig. 4.
I know that I could set a min_ou_temp to control the natural ventilation in the winter season, but the problem is that this temperature it is also used in summer, which is a problem because in our climate we have summer nights with low temperatures, good for night cooling. Can you imagine any solution?
Another thing I was thinking is, in my logic, I should set the min_in_temp_ and max_in_temp_ with a degree difference to avoid calculation problems. Because if I set both equals, heating and cooling setpoint and natural ventilation min and max, the program will use turn on both at the same time. What do you think about that? Do you think I should place one degree more than the heating setpoint and one degree less than the cooling setpoint, in the minimum and maximum ventilation temperature respectively?
At the same time to deal with the heating problem during the summer season (Nov, Dec, Jan, Feb, and Mar), I used the Seasonal Schedule proposed by @chris as shown in Fig. 5.
Yeap! I should have been clearer, but that’s what I meant when I said the ventilation setpoints should be set to “around” the HVAC setpoints - if they’re the same, the window is often open at the same temperature your HVAC starts operating.
I think simply offseting your setpoints and running the simulation would have gotten you the answer to this question
But if you’re asking if your reasoning is correct, I can confirm that you have the right idea. But make sure to test a couple of different offsets, there isn’t a single rule that will work for all buildings. One thing to keep in mind is that the heat released by people, lights, equipment, or energy stored in thermal mass will keep the interior temperature greater than the outdoor temperature, unless you’re actively cooling the space (known as the balance point temperature). So your minimum ventilation temperature can usually be an exception to this rule, as it can be less than or equal to the heating setpoint, due to this interior, passive heating. But again, this will vary based on the actual internal heat gain rate, room volume, and ventilation rate, so you’ll have to test it out.
Is there any useful ventilation potential in winter? If not, the easiest solution here would be to just turn off the ventilation during winter with the _schedule_ input in the Ventilation Control component. It accepts True/False values that allow you to disable the ventilation during certain time periods.
Hi! Thank you very much for your suggestions. I really appreciate your time spent for this long and complete answer.
I did some tests based on your comments. I was able to fix it, not turning on the heating when the window is open by putting 2 degrees difference in the min_in_temp_. I’ve also defined a min_out_temp_ which doesn’t affect my cooling loads during the summer.
Now I am not being able to solve for the cooling, that the windows stay closed when the cooling is on. If I don’t define max_in_temp_, shown in Fig. 1, the cooling is on while the window is open, for example in the evening. If I try to set the max_in_temp_ two degrees below (25°) the setpoint temperature (27°C), the software always keeps the window closed and turns on cooling all the time, as shown in Fig. 2. It is somewhat strange since in the first case from 0am to 7am it opened the windows to ventilate, but in the second case, it keeps them closed, which causes the temperature to rise dramatically. And it is for that reason that exceeding the max_in_temp_ always keeps the windows closed.
I can’t figure out what could be the problem. Can you imagine what could be a possible solution?
Try switching your max_out_temp_ and max_in_temp_. And if that doesn’t work, try reducing the max_out_temp_ even more (i.e. ~24C), and removing the max_in_temp_ completely.
The max_out_temp_ needs to be lower because your ventilation air will be passively warmed a couple of degrees by your internal and solar gains in the room. From the screenshot, it looks like outdoor air is warmed an additional 3 degrees, which is why 25 or 24C seems more reasonable.
The max_in_temp_ needs to be higher to avoid conflicting with your HVAC setpoint.It’s clear your HVAC system is maintaining room temperature at your cooling setpoint, which is preventing your window from opening. I’m not exactly sure why this is happening, I would have to look at your GH file to get a better sense of your building. My guess is your building has very high internal or solar gains, which is preventing your building from cooling down passively even when the air temperature is quite low. I admit this contradicts my earlier advice to maintain an offset from the HVAC setpoint. As you can see, that suggestion doesn’t work in cases when the internal heat rate prevents the room from equilibrating with the outdoor temperature.
Also, can you pass your latest GH script? There’s a couple of things in your screenshot that I’m not sure about, that would be easier to check in GH.
Sorry, I forgot to upload the GH file in the previous answer. I think that one of the conflicts may be due to what you say about high solar gains, since the area I am studying is relatively small with a large glazed area. As seen in the results of the energy balance, the solar gains are significant, Fig. 1.
I just tried out the strategy I recommended and it works. Switching the max_out_temp_ and max_in_temp_ still resulted in some cooling with the windows open, but lowering the max_out_temp_ to ~24C resolves it. You can probably refine the setpoints some more, but with just those edits, you can see the end result (image below) seem to address all your concerns. The zone has natural ventilation during the cool mornings, cooling during the warmer evenings, and only some minor overlap during the transition between the two. It also seems robust. It works on the other zone with windows, and at some other dates, but you should investigate it further, I only did a cursory check.
I increased the cooling setpoint in the file you uploaded from 26 to 27, in order to get it to match the scenario you described in Figure 2.
My dates start at Jan 10th, 01:00, whereas yours starts at Jan 10, 00:00. This again, is to match the senario in Figure 2. The dates there seem to be one hour forward, from the LB dates (which is what I used). Most likely this is just a copy and paste error, and will have no effect on results.
I’m outputting the interior drybulb temperatures, whereas you are using the interior operature temperature. The ventilation setpoints refer to interior drybulb temperatures, so I think this is a more useful output.
The resulting cooling, and window opening factor results don’t exactly match what you’re showing in Figure 2, so its possible there’s another discrepency I missed (or some software version mismatch), but it seems close enough that I think the optimized scenario above should work the same in either case.
Finally, I notice that you are shutting off the HVAC, and the natural ventilation between 8am and 1pm, with a custom schedule, (which explains the odd temperatures during that period in the outputs above). I’m curious, why is this needed?
