Hi all,
I have modeled chilled beams and conventional VAV systems for an office
building. I am getting 28% lower annual energy consumption with chilled
beams.
Has anyone done similar comparison? I would like to confirm if such energy
savings are achievable with chilled beams??
Thanks and Regards,
Sanket
The ASHRAE Journal has at least two detailed articles in the past ~6 months comparing these. The first was by Steve Taylor and included many considerations for controls and design differences. The second was a case study of a large building somewhere in Asia (I think).
Sorry I can?t give specific references ? I?m about to depart for the day.
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
Actually, the case study building was built by InfoSys in India and used one system for half of the large building and another for the other half.
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
You might want to check the following paper from TRANE about that topic:
http://www.trane.com/content/dam/Trane/Commercial/global/products-systems/education-training/engineers-newsletters/airside-design/adm_apn034en_1209.pdf
Kind regards
p.p. Florian Dubisch
ifes GmbH
in the etrium
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Germany
Fon: +49 221 801099-0
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ifes is member of the DGNB = German Sustainable Building Council e.V.
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ppa. Gerhard Hoffmann
Von: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] Im Auftrag von Jim Dirkes
Gesendet: Dienstag, 10. Juni 2014 12:29
An: Jim Dirkes; Sanket Puranik; bldg-sim at lists.onebuilding.org
Betreff: Re: [Bldg-sim] Chilled beam Vs conventional VAV systems
Actually, the case study building was built by InfoSys in India and used one system for half of the large building and another for the other half.
James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653
28% reduction sounds like a big difference if you are referring to total energy use of the building.
Can you go back to your two cases and show each end-use to verify where the savings is occurring?
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Sanket,
Your energy savings is based on a lot of factors.
? You might see significant reheat reduction if you?re moving less total air.
? You?ll see a fan power savings by moving less air, but be cautious on pressure drop due to reduced AHU size and duct size, which can eat into the fan power savings. A VAV system sized for 450 fpm in the AHU operating most hours between 250-350 fpm may use less energy than a CAV system serving chilled beams where the velocity is 450 fpm all the time even if half as much air is being distributed.
? There shouldn?t be much cooling savings. A little associated with reduced fan heat due to reduced air flow.
? If you have a separate chiller that is providing warmer chilled water to the beams you should see some saving there too versus a central chiller that is generating 44F and then blending the water to 58F for the beams.
Here?s a link to the 2012 SimBuild conference paper ?Issues Arising from the Use of Chilled Beams in Energy Models?.
http://www.ibpsa.us/simbuild2012/technical_sessions.shtml
Good luck,
Fred
Fred Betz PhD., LEED AP ?BD&C
Senior Sustainable
Systems Analyst
AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Blvd. | Madison, WI 53719
P: 608.236.1175 | F: 608.238.2614 | www.aeieng.com
fbetz at aeieng.com
A low energy radiant slab system is one of the strategies in Nrel's 'Strategies
. Worth a skim through!
for 50% energy savings in large offices'
Radiant systems such as chilled beams affect Operative temperature more
directly than VAV. The standard unmet hours test is therefore a little
unfair to these kinds of system. Perhaps it is worth the hassle
demonstrating that a comparable level of comfort is achieved during
occupied hours.
Apart from the conditioning of outdoor air latent heat removal is limited
because chilled water temperatures are higher. DOAS tends to deliver air at
a higher temperature as well - typically 15 - 16degC. This is also a
limiting factor in terms of the kind of load that CBs can deal with.
Designers are loath to specify CBs. Reasons include loss of flexibility for
subsequent fit outs, limited loads and limited contractor experience.
Hope this helps
Chris