Pumping requirements - District cooling system

Vincent, same answer as v2009: in addition to distribution network pumps you should also include central plant pumps.

Eliot

Hello

I am using "Path 2. Comprehensive System Power Simulation" to achieve this credit. I understand that Path 2 does not need to meet the requirement of not exceeding 2.5% annual thermal energy in my pumping system.

Instead, I just need to show that my proposed DES plant shows an annual energy savings improvement of at least 10% compared to a DES plant with minimum efficiency requirements and a that the proposed average efficiency must be 10% better than the baseline case average efficiencies.

Could you help me confirm if this is correct, please?

Antonio, I believe your understanding may be incorrect. Path 2 does not eliminate the 2.5% pumping energy requirement, but instead offers a different way of documenting compliance. I'm not seeing an explicit exemption for pumping energy in Path 2 in the Reference Guide's Step-by-Step Guidance or Further Explanation sections, or in the Appendix 4 DES modeling guidelines. Are you seeing wording that gives you the impression that the pumping energy limit is not part of Path 2?

Eliot

Hello again, thanks for the previous answer. I get that the 2.5%-pumping-energy requirement must be achieved no matter the path.

I have another doubt related to this credit: Does the plant with efficiency upgrades analysis take into account the pumping systems? I think not because these systems are not included in sections 6.4 and 7.4 in ASHRAE 90.1-2010. Only in the chillers, boilers and cooling towers, I have to do the analysis with the 10%-efficiency improvement. I need to do this analysis because the project has a combined heat and power system

Can you help me to confirm if this is correct please...

Antonio, there are two kinds of pumping energy in the credit: first, distriubution pumping to move hot/chilled water through pipelines to customers; and second, boiler/chiller pumps within a production plant. The latter should be included in a plant upgrade analysis, while distribution pumping outside the plant should be excluded from the analysis.

Eliot

Thanks for the clarification, Eliot.

Currently, I am developing the three scenarios asked by path 1 (pg. 440 LEED ND V4) with the following features of my pumps within the central plant:

Minimally efficient DES plant (Baseline ASHRAE 90.1)

Chilled-water pumps---------22 W/gpm

Condenser-water pumps----19 W/gpm

Proposed CHP plant (current project's pumps)

Chilled-water pumps---------79.1 W/gpm

Condenser-water pumps----28.7 W/gpm

DES plant with efficiency upgrades (10% efficiency upgrades)

Chilled-water pumps---------19.8 W/gpm  ??

Condenser-water pumps----17.1 W/gpm  ??

Should I consider these numbers in this scenario?

Antonio, yes, I would include those numers.

Eliot

I really appreciate your help, Eliot.

Also, in this project that I'm working on, they are including heat exchangers in each of the 15 independent buildings that are part of the district cooling with the following temperatures:

Cold side ----- ∆T=15°F

Hot side ------ ∆T=12°F

Would you see any inconvenience in using this ∆Ts ? I ask this because I have seen projects with ∆T=10, 12 and 14 but this is the first time I see ∆T=15.

Which source would you recomend me that explains thess design temperatures for a District cooling?

Thanks

Antonio, I would recommend providing documentation from the heat exchanger manufacturer (e.g. a "cut sheet") that describes exchanger performance specifications, including the deltas.

Eliot

Hello

"Annual district pumping energy consumption that exceeds 2.5% of the annual thermal energy output......." 

This requirement should include the chilled-water (chiller to load) and condenser-water (chiller to cooling tower) pumpings? Or just chilled-water pumps?

Thanks

Antonio, any kind of pump should be included in the 2.5% calculation, including condenser water pumps.

Eliot