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Thermal Storage - Hot Water Storage Object

asked 2015-11-20 13:08:17 -0500

RChidwick gravatar image

updated 2015-12-10 15:27:03 -0500


I have been looking around the forum trying to figure out how to set up hot water thermal storage. I am working on a simulation for a greenhouse that uses a hot water radiant floor. The hot water is supplied by a boiler. So I have currently put together a plant loop using a boiler, HW setpoint manager, low temp radiant var flow object, and a variable speed pump. This is very similar to what the actual system is.

However, the greenhouse also has a very large hot water storage tank. Hot water can be stored there in case not all of the hot water is required at a certain time to heat the greenhouse, or if the greenhouse operator wants to run the boiler to get CO2 off the stack and pump that into the greenhouse for the plants while the hot water gets stored in the tank for later use.

I am wonder how I would go about doing this. I see from the HVAC System Requests and Priorities spreadsheet that a Thermal Storage - Hot Water Storage object exists but I do not see it in OpenStudio. I am currently using OS 1.9.0.

So far I have tried using water heaters on the demand side of the loop with the boiler on the supply side but that hasn't worked.

I'm grateful for any suggestions and help. Does anyone know if maybe the Thermal Storage Hot Water Storage object has been developed but not yet released?

Thank you.

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answered 2015-11-21 15:32:14 -0500

updated 2015-11-21 15:37:42 -0500

You can always use a water heater as a hot water storage tank. If it is meant to be only a storage tank, heater capacity can be set to zero. In addition, if the storage tank is located in your greenhouse (and if this is also a thermal zone) you can assign it to this zone, i.e. the ambient temperatures for the tank will the zone air temperatures of the greenhouse.

You might also look here

Does this answer your question ?

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Thank you for your quick reply! This is very helpful.

I do have a followup question. How can I set up the plant loop so that the boiler serves both the HW heater and the radiant floor, but serves the radiant floor first and then charges the HW heater when there is no demand for heat by the radiant floor? And then how do I get the HW heater to also serve the radiant floor?

RChidwick gravatar image RChidwick  ( 2015-11-24 12:22:00 -0500 )edit

You could set up a plant loop with a boiler (perhaps with small tank volume) in parallel with a HW tank on the supply side of the loop; define the desired temperatures for the HW tank, for the plant loop (with the loop setpoint manager), and for the the radiant floors separately. If this does not work satisfactorily, you could also use an additional tempering valve on the supply side of the plant loop.

OS-user-AT gravatar image OS-user-AT  ( 2015-11-27 03:33:35 -0500 )edit

I tried putting the HW tank in parallel with the boiler and that gave better results. I would like to try your suggestion with the tempering valve but I don't know how to use a tempering valve. I tried adding one to my plant loop but I got several severe errors (shown below). How would I add a tempering valve to my plant loop? -TemperingValve object needs to be on an ACTIVE branch -TemperingValve object setpoint node not valid. Check Setpoint manager for Plant Loop Temp Setpoint -TemperingValve object stream 2 source node not valid.

Thank you so much for your help, I'm very grateful!

RChidwick gravatar image RChidwick  ( 2015-12-04 18:52:01 -0500 )edit

regarding use of TemperingValve, I would need some more testing for myself. But it could help you to run some of the example idf files in the EP distribution. Or you could post another question on unmethours.

OS-user-AT gravatar image OS-user-AT  ( 2015-12-11 02:01:43 -0500 )edit

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Asked: 2015-11-20 13:08:17 -0500

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Last updated: Nov 21 '15