Hi, QiangMin
In the chiller operation, the tank is chilled to a set point temperature and stop.
You can use the night cooling to cool some water and store in the tank. Because the temperature from night cooling is not very low and uncontrolled, it cannot be easily scheduled.
One can let it cool and shut off at 5 am, when the temperature is usually the lowest.
The normal chillar capacity is quite high. When the cooling is used, the chiller is running.
With the storage tank case, the tank capacity is the cooling available. The capacity is not enough to cool the one or two hour period during the hottest time of the day.
One of my student tried this was done in Malaysia, where the low temperature is in the 23-25°Crange. You may have a lower night time temperature. If the desired room temperature is 28°C, there are only 3°C of temperature difference.
In the simulation, there are two loops using he same tank. The charging mode in the tight time. The discharging mode when the water is needed.
There is a hotwater tank system also running in the similar way. Heat it up and then used it some other time as domestic hot water. The heater was a solar panel.
==========================
Two loops are required, the source side and the use side of the tank.
Source side can be the solar roof panel. The use side would be a low temperature radiant panel, which is turned on when the room temperature is above 27°C. The tank water temperature would rise when in use and the cooling effect is zero when the room temperature is around 29°C, while the natural temperature without the cooling would be around 31°C. At that point, the outdoor temperature is actually falling, and you have to make sure that the panel continue to heat the room.
===============================
The conclusion was to make a large un insulated tank mouned in a wooden insulated cabinit.
In this way, the coolness can be turning on off fast. The storage tank object has a insulation field to control the heat transfer rate.
Open the doors of the cabinet when cooling is needed. As soon as the tank is hot, close the doors again, until it can be cooled again by night cooling.
Because the operating temperature is un-known, the charging has to be done on a time schedule with high temperature lock out. The coldest night would then be the tank temperature.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx
Date: Tue, 26 Jul 2011 11:07:19 -0700
Subject: Re: [EnergyPlus_Support] control sequnce
Thermal tank connect a cooling tower(source side/condenser loop) and the chilled water loop(use side). (no chiller or compressor in the system)
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In the chiller operation, the tank is chilled to a set point temperature and stop.
You can use the night cooling to cool some water and store in the tank. Because the temperature from night cooling is not very low and uncontrolled, it cannot be easily scheduled.
One can let it cool and shut off at 5 am, when the temperature is usually the lowest.
The normal chillar capacity is quite high. When the cooling is used, the chiller is running.
With the storage tank case, the tank capacity is the cooling available. The capacity is not enough to cool the one or two hour period during the hottest time of the day.
One of my student tried this was done in Malaysia, where the low temperature is in the 23-25°Crange. You may have a lower night time temperature. If the desired room temperature is 28°C, there are only 3°C of temperature difference.
In the simulation, there are two loops using he same tank. The charging mode in the tight time. The discharging mode when the water is needed.
There is a hotwater tank system also running in the similar way. Heat it up and then used it some other time as domestic hot water. The heater was a solar panel.
==========================
Two loops are required, the source side and the use side of the tank.
Source side can be the solar roof panel. The use side would be a low temperature radiant panel, which is turned on when the room temperature is above 27°C. The tank water temperature would rise when in use and the cooling effect is zero when the room temperature is around 29°C, while the natural temperature without the cooling would be around 31°C. At that point, the outdoor temperature is actually falling, and you have to make sure that the panel continue to heat the room.
===============================
The conclusion was to make a large un insulated tank mouned in a wooden insulated cabinit.
In this way, the coolness can be turning on off fast. The storage tank object has a insulation field to control the heat transfer rate.
Open the doors of the cabinet when cooling is needed. As soon as the tank is hot, close the doors again, until it can be cooled again by night cooling.
Because the operating temperature is un-known, the charging has to be done on a time schedule with high temperature lock out. The coldest night would then be the tank temperature.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx
Date: Tue, 26 Jul 2011 11:07:19 -0700
Subject: Re: [EnergyPlus_Support] control sequnce
Dr. Li,
In thermal storage:
- setpoint temperature, which seems used to determine whether the source side flow(condenser loop) is requested or not, when the tank temperature rise.
- Source side availability schedule name, which is used to control the flow too.
- condenser operation scheme, which seems used to control the condenser loop.
my project has a interesting schedule, which is unoccupied during weekday, most likely, and has a big occupancy number in weekend.
I'm going to use the model of single speed cooling tower run in the "free convection" regime to simulate the night sky cooling roof to produce condenser water and collect them in thermal storage in the night time, and use these chilled water from thermal tank in weekend day time. When I use the chilled water from thermal tank during daytime, there is no flow in my source side, no matter how high the temperature is in tank, since I only have the night sky roof cooling in my condenser loop. I wish I state my issue clear.
Is there any other method to simulate night sky cooling roof than cooling tower? I know about 60% heat is removed by radiant, not convection in night sky cooling. Thanks a lot.
Regards,
Qianmin
On Tue, Jul 26, 2011 at 10:20 AM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:
What is the control sequence you are considering?
Charging and discharging time, of the storage tank?
I have not look at the example yet.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx
Date: Mon, 25 Jul 2011 17:20:29 -0700
Subject: [EnergyPlus_Support] control sequnce
Hello,Besides .svg file, is there any other source could help me study the control sequence of each hvac system? I am looking at the chilledwaterstorage-stratified.idf, and there are schedules or setpoints for condenser water loop, thermal storage, and source side of thermal storage. I'm confused the control sequence in this system now. Anyone could help me better understand its sequence? Thanks a lot. Is there any override?Regards,Qianmin
__._,_.___
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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