[Bldg-sim] Spam:Re: Process Loads?

Arvinder Dang Arvinder.Dang at som.com
Thu Feb 5 09:28:56 PST 2009


Marcus,

Hope you're doing well. A quick question as a follow up.

I have a campus building that is using district chilled water and steam - and the energy modeling is based on "Required Treatment of District Thermal Energy in LEED NC 2.2 and LEED for Schools". The project is seeking only 2 points and the model only includes downstream equipment keeping the district heating and cooling cost neutral in both the base case and the design case.

The cost of steam is around $44.2 per Mlb of Steam, cost of chilled water $0.18 while that of electricity only $0.09 base don campus rates.  Since the cost of steam and chilled water is way higher than that of electricity, there is no way that process energy cost which includes equipment, elevators, etc equates to 25%. Cost of space heating and cooling constitutes a bigger fraction compared to lighting, equipment, pumps and all others end uses that use the electric rate.

Would a narrative explaining the same justify why the minimum 25% requirement cannot be held for district heating and cooling systems that model only downstream equipment and are kept cost neutral due to the differential in the rate structure.

Thanks


ARVINDER DANG, LEED(r) AP
SUSTAINABILITY SPECIALIST

SKIDMORE, OWINGS & MERRILL LLP
224 SOUTH MICHIGAN
CHICAGO, IL 60604
T: 312.360.4633  F: 312.360.4910
ARVINDER.DANG at SOM.COM<mailto:ARVINDER.DANG at SOM.COM>


SOM

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From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Marcus Sheffer
Sent: Thursday, February 05, 2009 10:49 AM
To: bldg-sim at onebuilding.org
Subject: Re: [Bldg-sim] Spam:Re: Process Loads?

The word "default" is unfortunate; the credit language should read "at least".  If your project is under 25% simply submit justification for why you are under 25%.  The best way to do that is with a table showing the assumed plug loads or other process loads in the facility.

So if you are over 25% no worries; if you are under justify why you are under.  Don't add process loads until you reach precisely 25% as some projects submitting for LEED have done.

Regarding facilities with very high process loads pursuing LEED certification, James is correct that this poses a major problem which the USGBC will hopefully address this year.

Marcus Sheffer, Vice-Chair USGBC EA TAG
Energy Opportunities, Inc/a 7group Company
1200 E Camping Area Road, Wellsville, PA  17365
717-292-2636, sheffer at sevengroup.com<mailto:sheffer at sevengroup.com>
www.sevengroup.com<http://www.sevengroup.com>

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of James Hess
Sent: Wednesday, February 04, 2009 10:11 PM
To: Demba Ndiaye; Anis Ben Ayed;
Cc: Caleb Brantley
Subject: Re: [Bldg-sim] Spam:Re: Process Loads?

FYI ... our take on this issue is to document the inputs that make up the misc equipment.  In many cases, we find that misc equipment, or "process loads" come nowhere close to 25% of total costs.

For example, we are currently working on a library LEED project.  We have very good estimates for the number of computers going into the facility, and have estimates for students with notebook computers, printer/copiers, breakroom equipment (refrigerator, coffee pot, etc.), etc.  You can get energy estimates for all that stuff from EnergyStar's website (they have lots of good data), or take your own measurements of equipment over time like I have ( using simple inexpensive equipment such as the "KillaWatt" plug in 120V plug load measurement device).

Anyway, we document it and add all that up --> comes to ~ 0.3 watts/SF, add a schedule into our energy simulation program, and we come nowhere close to 25% of total energy costs.

What would we do at that point?  We have good wattage inputs based on sound and reasonable data.  For example, a typical desktop computer will use ~ 65 watts on average.  A 22" flat panel LCD monitor will use ~ 45 watts.  So, do you throw all those numbers out and arbitrarily increase the "watts/SF" values until process loads = 25%?

Our interpretation is no.

Based on the following from LEED NC 2.2

[cid:image001.jpg at 01C98784.EE340830]

We interpret this as we can use less than 25% as long as we document, so we document.  We document our assumptions for process loads anyway so if it comes out less, we're covered.

We did have a project that was a flight simulator building for the US Air Force.  The simulator equipment used a ton of energy --> energy costs > 75% of total building energy costs.  That blew the LEED savings out of the water.  Even if you assign the same load to the baseline, mathematically it's very difficult to achieve overall building energy savings of  14% if 75% of energy --> you can't do anything about.  :).  In fact, we could not.

Just some food for thought on how we approach this area.

Hope this helps.

Regards,

James


James A.  Hess, PE, CEM
Energy Engineer
TME, Inc.
Little Rock, AR
ph   501-666-6776
cell  501-351-4667
jhess at tmecorp.com<mailto:email at tmecorp.com>

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Demba Ndiaye
Sent: Wednesday, February 04, 2009 5:57 PM
To: Anis Ben Ayed; bldg-sim at onebuilding.org
Subject: Spam:Re: [Bldg-sim] Process Loads?

The process energy cost should compose at least 25% of the total energy cost.

And yes, if you have a total cost of $1,333 then the process energy should be >= $333.

_____________
Demba Ndiaye

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Anis Ben Ayed
Sent: Wednesday, February 04, 2009 6:33 PM
To: bldg-sim at onebuilding.org
Subject: [Bldg-sim] Process Loads?

Hi All,

According to the LEED NC v2.2 user manual, the default process energy cost is 25% of the total energy cost for the baseline building.

Example:
The total energy cost for a baseline building is T = (X + Process loads)
Let's assume that X = $1000.00 = 75% * T

To find the energy cost for a baseline building, we solve for T
Therefore T = $ 1000.00 / 75% = $ 1333.33
and the Process loads' cost = 25 % * $ 1333.33 = $ 333.33
This is how I understand the 25% process load calculation.

Can someone please confirm this approach?

Thank you,

Anis

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