Hi, Jean
Your first points on simulation for buildings are good.
However, it is not the simulation processes that limits the presentation of real time result.
It is the software that limits it. EPlus is schedule driven and only use feed back on temperature related variables. Any other simulation you wanted to do are add on items. All the input values are scheduled for a fixed time step.
That was why I added the day lighting as an example. The program was not measruing the light intensity through the window. It was calculating the intensity using the input value in the .epw which is a fixed schedule of TMY weather conditioon.
If you change the people object to CO2 object and use a schedule, the OA damper will be CO2 level controlled. Then you have lost the "green" grading comparison base line.
You can do an add-on as you have suggested to show that CO2 detection and control will save running cost. However, it is already included in the people object, if it is the source of CO2 and OA dampler is already controlled by the number of people.
You have detached the source that generating the CO2 and measuring the level directly for the control of CO2 using OA damper. The DAOS was used for the same reason, fresh air to the zones. The CO2 level is not scheduled, but is measured at real time. How do you generate this operating level without using a schedule for EPlus? It can be a CO2 reference file, which is still a annual schedule. This is my point. As soon as you use the EMS to change the schedule, the base line characterestic is lost.
If you do have a real time calculation introduced in Eplus for CO2 control, it will be another module which is optional for grading comparison calculation.
This is also the reason, I think, why the room air, inter-zone ventilation are not part of the simulation for annual weather file energy usage.
The limitation is the EPlus software operation and not the limitation of a simulation process.
The comparison of energy usage is OA with people and without people object dependency as damper control. In order to have OA demper control, some sensor must be used. People counter at the door, CO2 level measurement of the room air. These are not in EPlus.
So CO2 measurement is required in real life as a sensor to implement the variable damper position based on people in a room.
This is my reason for warning people using VAV and VRV. The sensors are not in the EPlus input. The control equipment for the VSD and VFD and VAV damper positions are not included.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Mon, 26 Sep 2011 04:
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Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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Your first points on simulation for buildings are good.
However, it is not the simulation processes that limits the presentation of real time result.
It is the software that limits it. EPlus is schedule driven and only use feed back on temperature related variables. Any other simulation you wanted to do are add on items. All the input values are scheduled for a fixed time step.
That was why I added the day lighting as an example. The program was not measruing the light intensity through the window. It was calculating the intensity using the input value in the .epw which is a fixed schedule of TMY weather conditioon.
If you change the people object to CO2 object and use a schedule, the OA damper will be CO2 level controlled. Then you have lost the "green" grading comparison base line.
You can do an add-on as you have suggested to show that CO2 detection and control will save running cost. However, it is already included in the people object, if it is the source of CO2 and OA dampler is already controlled by the number of people.
You have detached the source that generating the CO2 and measuring the level directly for the control of CO2 using OA damper. The DAOS was used for the same reason, fresh air to the zones. The CO2 level is not scheduled, but is measured at real time. How do you generate this operating level without using a schedule for EPlus? It can be a CO2 reference file, which is still a annual schedule. This is my point. As soon as you use the EMS to change the schedule, the base line characterestic is lost.
If you do have a real time calculation introduced in Eplus for CO2 control, it will be another module which is optional for grading comparison calculation.
This is also the reason, I think, why the room air, inter-zone ventilation are not part of the simulation for annual weather file energy usage.
The limitation is the EPlus software operation and not the limitation of a simulation process.
The comparison of energy usage is OA with people and without people object dependency as damper control. In order to have OA demper control, some sensor must be used. People counter at the door, CO2 level measurement of the room air. These are not in EPlus.
So CO2 measurement is required in real life as a sensor to implement the variable damper position based on people in a room.
This is my reason for warning people using VAV and VRV. The sensors are not in the EPlus input. The control equipment for the VSD and VFD and VAV damper positions are not included.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Mon, 26 Sep 2011 04:
Dr Li is pointing at one of the fundimentals of building energy simulation.
--Simulation is a good way of comparing stradegies and learning from the effects which are better combinations than others.
--Simulation is bad at replicating reality to come up with realistic results within 10% of the real world measurements. This is because of unknown usage types, patterns and schedules of the building to a large extent.
Unfortuanately, the latter is always the expectation in the mind of the client. As everybody knows, the best ideas in the world don't get used if they don't get sold. A good example of this is a simulation building's geometry and zone division simplification. The client will want to see what the 3D simulated building looks like. When the pictures look bad, you won't sell him believability of the simulation.
In my case I have a working EMS now to control my dampers with regard to the CO2 levels in the spaces and are playing with control stradegies. What has become apparent is the combination of the link between combating CO2 loads with this technology and at the same time retaining the room set point temperatures. The two do not always co-exist peacefully. They also have an upto 10% impact on my peak cooling load which is the main question from the client.
The client was quite insistant that the CO2 DCV is simulated and prooves effective, because it helps justify his having sold the idea to his client.
Never forget that the building industry is a very political place.
As for my system and the suggestion of my ODA, I have it easy in that the fan volume capacities are known from the installed systems. It is a DOAS and so when my dampers open and close they directly change the ODA. I have suppressed mixing by setting the ODA fraction schedule in the ODA Controller to always-1.
--Simulation is a good way of comparing stradegies and learning from the effects which are better combinations than others.
--Simulation is bad at replicating reality to come up with realistic results within 10% of the real world measurements. This is because of unknown usage types, patterns and schedules of the building to a large extent.
Unfortuanately, the latter is always the expectation in the mind of the client. As everybody knows, the best ideas in the world don't get used if they don't get sold. A good example of this is a simulation building's geometry and zone division simplification. The client will want to see what the 3D simulated building looks like. When the pictures look bad, you won't sell him believability of the simulation.
In my case I have a working EMS now to control my dampers with regard to the CO2 levels in the spaces and are playing with control stradegies. What has become apparent is the combination of the link between combating CO2 loads with this technology and at the same time retaining the room set point temperatures. The two do not always co-exist peacefully. They also have an upto 10% impact on my peak cooling load which is the main question from the client.
The client was quite insistant that the CO2 DCV is simulated and prooves effective, because it helps justify his having sold the idea to his client.
Never forget that the building industry is a very political place.
As for my system and the suggestion of my ODA, I have it easy in that the fan volume capacities are known from the installed systems. It is a DOAS and so when my dampers open and close they directly change the ODA. I have suppressed mixing by setting the ODA fraction schedule in the ODA Controller to always-1.
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
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