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Demand shifting with thermal storage in Energyplus

asked 2016-05-05 15:02:03 -0600

rkbest's avatar

Does EnergyPlus uses optimization to charge thermal storage during off-peak hours and discharge during peak? If not how can this be implemented for cost minimization? 1. I am using reference DOE commercial building with thermal storage to see the impact w.r.t building without storage. I also want to control the charging and discharging based on the peak and off-peak power price. Any suggestions how to implement this. 2. How do I get the total peak energy use and off-peak energy use for building conditioning from the simulation?

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answered 2016-05-05 22:44:44 -0600

RyanStochastic's avatar

I'm not aware of any optimization for TES in E+; a quick search of the documentation for the text 'optimiz' or 'optimis' might get you what you need.

As for controlling based on the peak pricing, you will likely have to import the pricing signal as a schedule, and use the energy management system language to roll your own algorithm/logic for controlling the TES.

To your last question, you can output the hourly (8760) results from your simulation (they should come out automatically from the DOE models), then use your favorite analysis software (Excel works in a pinch) to pull out the records for the peak/off peak hours separately and sum/average them as you see fit.

DView may have the ability to filter by hour of day or day of year - i'm not sure.

Good luck!

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@RyanStochastic Thanks, I wanted help with your second suggestion for importing the pricing signal as schedule and if you could guide me to some example or tutorials for setting EMS in the way I desire. (I have never wrote any EMS control yet.)

rkbest's avatar rkbest  ( 2016-05-17 14:17:20 -0600 )edit

answered 2016-05-06 10:08:04 -0600

301_Hours's avatar

Some additional practical items to consider that you may already know, but am noting for others are some sizing info, demand charge time frame and any redundancy you may be able to remove to reduce first cost.

You want to size the tank so the chillers (i'm assuming you're storing chilled water) don't run during peak hours. in very large systems (2+ million gallons [8M liter]) you may not be able to achieve this.

You need to size the tank for 10% additional capacity to account for themocline between the warm top layer and cold bottom layer of CHW.

Confirm your utility rate structure does in fact charge demand over a certain time period. I just finished an analysis for a 5M gallon CHW storage tank, which reduced the day time peak by 3,000 kW. However that 3,000 kW just came online later and i saved almost nothing on demand charges because the utility didn't care what time of day the peak demand occurs.

If you have multiple chillers, say 3 chillers sized for 500 tons with a building peak load of 1,000 tons. You may be able to remove the redundant chiller if your storage tank can produce 500 tons of cooling. That savings should help reduce your system cost.

Hope that helps.

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Thanks @301_Hours, What was the configuration for the CHW tank in you analysis?i.e. Parallel to the chiller as a separate branch or in series with the chiller. Also, can you throw some light on how you setup your operation scheme? I am just using single chiller for s small office and CHW storage. Hence, if I need to completely avoid peak power, the storage will be bigger than chiller capacity with desired autonomy.

rkbest's avatar rkbest  ( 2016-05-06 10:30:22 -0600 )edit

For the larger plants they are designed to operate in parallel.

Like you stated the sizing becomes large if you want to avoid using the chiller entirely so parallel is needed.

Also, depending the size of the tank a chilled water reset temperature may be challenging. You'll have to monitor that to ensure you're not getting a bunch of unmet load hours.

301_Hours's avatar 301_Hours  ( 2016-05-06 11:26:12 -0600 )edit

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Asked: 2016-05-05 15:02:03 -0600

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Last updated: May 06 '16