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%OA Increase & Increased Air Filtration Energy Consumption
Due to COVID-19, there is an large demand for increased fresh air and increased air filtration, particularly in shared spaced. I'm trying to figure out the below questions, but am not sure how to go about calculating energy increase for these situations...
In a 300,000 sq ft* building that has approximately 300,000 CFM of AHUs that were previously getting 20% outdoor air and are now getting 100% outside air, what would the energy increase (in kwh) be to condition 300,000 CFM of outside air instead of 240,000 CFM of return air and 60,000 CFM of outside air? Assume EER of 12 for both situations. Unit operates 2080 hrs per year. Neglect capacity of chiller plants/boiler plants/etc.
Separately, what if MERV-14 filters were used instead of MERV-8 filters? What would the energy increase (in kwh) be for 300,000 CFM of fans for 2080 hrs per year? Assume ballpark average for pressure drops.
Thank you in advance.
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Originally Posted by
ixratskrad
Due to COVID-19, there is an large demand for increased fresh air and increased air filtration, particularly in shared spaced. I'm trying to figure out the below questions, but am not sure how to go about calculating energy increase for these situations...
In a 300,000 sq ft* building that has approximately 300,000 CFM of AHUs that were previously getting 20% outdoor air and are now getting 100% outside air, what would the energy increase (in kwh) be to condition 300,000 CFM of outside air instead of 240,000 CFM of return air and 60,000 CFM of outside air? Assume EER of 12 for both situations. Unit operates 2080 hrs per year. Neglect capacity of chiller plants/boiler plants/etc.
Separately, what if MERV-14 filters were used instead of MERV-8 filters? What would the energy increase (in kwh) be for 300,000 CFM of fans for 2080 hrs per year? Assume ballpark average for pressure drops.
Thank you in advance.
You cant go from 20% to 100% without MAJOR increases in BTU transfer!
Energy increase roughly 500% increase!
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how bigs a piece of string? so many variables starting with Climate location
Keep it simple to keep it cool!
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The question can't be answered without knowing your weather conditions. Where I live, you can run 100% OA all year long with no energy penalty. In Miami, the penalty is massive.
By the way, ASHRAE's emerging advise is to not go to 100% air but upgrade to a high-MERV filter. See this YouTube video preso from ASHRAE. The discussion about using recirc with a good filter vs. 100% OA is early in the presentation. The filtration discussion starts at 22:30.
https://www.youtube.com/watch?v=GNl4...ature=youtu.be
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I agree that there are too many unknowns to help answer your question. Without knowing your design conditions, it is unclear if it is advisable to load your equipment with 100% outdoor air.
With those disclaimers, using $0.13/kWh, I came up with $1,123,166.97 (lol - definitely don't go to the bank with this number!! So many unknowns that it could be off by several decimal points!!)
I basically used dimensional analysis and these calculators to solve for the change in total load (sensible + latent):
It was a fun academic exercise - interested to see what you come up with.
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