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NC-2009 EAc1:Optimize Energy Performance

DES Energy Cost

Marina Andrade

Sustainability Consultancy Services

Cushman & Wakefield

LEEDuser Basic Member

11 thumbs up

May 13, 2013

According to the Advance Energy Modeling for LEED, page 49 option 1, I should model all upstream equipment as cost neutral. However on the LEED guidelines for district energy systems says that we need to model the DES energy rate according to the section 2.4.2 "Energy Model Implementation: Energy Rate", page 14. Should or shouldn't I consider the energy cost from the DES system using option 1?

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 05/13/2013 - 19:31

For Option 1 you treat the DES just like any purchased energy source. You will need to determine a rate for the purchased energy. If you are actually buying it the rate is pretty straight forward. If the building owner and DES are owned by the same entity you will need to determine a reasonable rate. In either case the cost of the purchased energy is going to be be somewhat aligned with the cost of operating the DES.

Marina Andrade

Sustainability Consultancy Services

Cushman & Wakefield

LEEDuser Basic Member

11 thumbs up

Mon, 05/13/2013 - 20:23

Hi Marcus, The building owner and DES are owned by the same entity, so could I use the rate that is actually using in the DES system or I need to use the equation informed in the LEED guidelines for district energy systems? I'm saying that because using the rate derived from the equation "Units of $/MBTU=Virtual Electric Rate (in $/kWh)x71", the annual energy cost from the DES system was very high, which affect the cost energy saving from the downstream equipments. Thanks!

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 05/13/2013 - 20:55

Let me correct myself. If you follow DES you need to calculate the rate according to the formulas on page 14 in the DES. If you follow 90.1 and not DES then you can use the actual rate. Since the DES is optional you can do either one.

Marina Andrade

Sustainability Consultancy Services

Cushman & Wakefield

LEEDuser Basic Member

11 thumbs up

Tue, 05/14/2013 - 12:03

Right, you are saying that if I use the DES option 1 (Building Stand-Alone Scenario) I need to calculate the rate according to the formula in the DES guide and using the option 2 (Aggregate Building / DES Scenario) I could use the 90.1 to calculate the rate. Am I right? Thanks,

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 05/14/2013 - 13:22

Not quite. If you use DES Option 1 (2.4.1.1) then you follow 2.4.2.1. If you use DES Option 2 (2.4.1.2) then you follow 2.4.2.2 which allows the local rate. You do have the option of treating the DES as purchased energy under 90.1 and not using the DES at all. In this case follow the 90.1/LEED rules regarding rates.

Marina Andrade

Sustainability Consultancy Services

Cushman & Wakefield

LEEDuser Basic Member

11 thumbs up

Wed, 05/15/2013 - 12:03

Hi Marcus, Following the item 2.4.2.1 for DES option 1, I have 2 formulas to calculate the DES District Chilled Water rate: 1- “Units of $/MBTU = Virtual Electric Rate (in $/kwh)x71”; 2- “Units of $/ton-hour = Virtual Electric Rate (in $/kWh) * 0.85” *The virtual energy rate is 0.173 $/kWh Using the formula 1, it will give a result of 12.28 [$/MBTU]. 1[MBTU] = 0.29307107 [kWh] 12.28[$/MBTU] = 41.92[$/kWh] Using the formula 2, it will give a result of 0.14705 [$/ton-hour] 1[ton] = 3.51 [kW] 0.14705[$/ton-hour] = 0.042[$/kWh] Which one do you think I should you for the project? Thanks for your help,

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Wed, 05/22/2013 - 14:15

The MBTU conversion for formula 1 should be 1000000 BTU/3413 BTU/kWh = 293 kWh/MBTU. So the result is the same for both formulas.

Marina Andrade

Sustainability Consultancy Services

Cushman & Wakefield

LEEDuser Basic Member

11 thumbs up

Tue, 05/28/2013 - 14:05

Thanks!