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How to Consider HVAC-Template for a Building with Out-source Plant Energy?

asked 2020-05-17 12:56:27 -0600

Negar's avatar

updated 2020-05-17 14:17:49 -0600

I have a 13-story building for modeling in EP. The building is using an out-source energy plant with the boilers` efficiency of 85% (outside the building), the efficiency of two heat exchangers at the building (about 95% efficient), and the tunnel piping efficiency (about 95% efficient). Currently, I am not sure how I should consider the HVACTemplate for building heating. How can we design the source of heating for such a building?

More info provided here: The building was built from the start to accept high pressure, high-temperature hot water from the central plant. Hot water is produced through three HTHW to heating water heat exchangers. One of the three exchangers was added with neighbor building and is not shown on the control graphic below.

Hot water is distributed for the following purposes:

- entry force flow heaters and penthouse unit heaters

- hot-deck coils in the Link multi-zone air handler

 - heating coils in the building air handlers

 - reheat coils in Tower floor spaces

- domestic water storage immersion heater

 - perimeter hot water finned radiation

image description

Wondering if you can help me with EP modeling and the logic behind it?

Thank you

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answered 2020-05-17 18:06:34 -0600

If your building is connected to a central hot water plant that serves other buildings as well, then the best EnergyPlus option is the District Heating object. This allows you to set a flow rate and capacity of heating associated with the central hot water plant, so you will need to update the Environmental Impact Factors object to set the district heating efficiency (default value is 0.3 without the Environmental Impact Factors object).

Unfortunately, it doesn't appear that the latest EnergyPlus version 9.3 has an HVAC Template object to create a hot water plant with the building's heating components on the demand side and this District Heating object on the supply side -- there are only HVAC Template objects to create a hot water plant with a boiler on the supply side. If you are using the HVAC Template objects because you are altering the EnergyPlus input data file (IDF) manually, then you can use the boiler HVAC Template object to create the loop as a first step. When you simulate that IDF, EnergyPlus creates an expanded IDF (EXPIDF) containing all of the individual objects generated from the HVAC Template. As a second step, you can then replace the boiler with district heating in the EXPIDF. You can use any EnergyPlus example file with district heating as a resource if you have issues.

This process of replacing a boiler with district heating in a hot water plant would be much easier in an interface for EnergyPlus (DesignBuilder, OpenStudio, etc.) that has an HVAC diagram to visualize the connections between components.

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As I am working in Open-studio, I wonder how I can add more than one heat exchanger in the interface?

Negar's avatar Negar  ( 2020-05-22 19:34:40 -0600 )edit

First, add a WWHX to your plant loop diagram from the Library section on the right. That will connect one side of the WWHX, so then you need to view the other plant loop connected to this WWHX in order to add it from the My Model section on the right. Read this post for more details. You can add multiple WWHXs to each plant loop.

Aaron Boranian's avatar Aaron Boranian  ( 2020-05-23 09:02:32 -0600 )edit

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Asked: 2020-05-17 12:56:27 -0600

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Last updated: May 17 '20