Northwind Coolant Plant Tour (Downtown Phoenix)

We (Arco Const Team) went down to Phoenix to see a coolant plant that uses off peak electrical power to cool water to make ice during the evenings when the electricity is cheap that is then used to cool buildings during the day.

This project is a great example of District Power. District power works best in dense environments where a bunch of buildings are located within close proximity to each.

Current power systems if they were located closer to populated area would save a lot of energy by making use of district power.

The plant we toured is one of several in the downtown PHX area run by Arizona Public Service’s (APS) District Power subsidiary Northwind. The system was first developed in 2001 and has since then underwent rapid expansion. They have about 30 accounts that use the cool water to cool their buildings. Several large pipelines form a loop around the downtown to transport cool water to clients.

From EPA Profile Page about Northwind Phoenix:

Northwind Phoenix builds, owns, operates, and maintains campus and district energy systems, including combined heat and power facilities. Northwind provides the energy produced by these plants in the form of electricity, chilled water, and heat to its end-use customers, such as office buildings, universities, research facilities, and municipal buildings. The energy is typically transported over thermal and electrical distribution systems constructed, operated, and maintained by Northwind. From chilled water loops and thermal energy storage to electrical and steam distribution systems, Northwind Phoenix is the largest turn-key operator of district energy systems in Arizona.

From the APS/Northwind webpage is a nice short definition of District Power:

District energy, is an innovative centralized cooling and heating system that utilizes an extensive underground network of pipes to efficiently deliver hot and cold water, steam, or electricity from a central plant. This central plant is capable of servicing an entire campus or individual buildings, parceled areas, downtown locations and individual locations where there are concentrated energy requirements.


The key in understanding district power is to see it is particularly relevant in high density built environments.

  1. District power can enable cost savings through the efficient use of Combined Heating and Power (co-generation) and even tri-generation systems (Combined Heating, Cooling and Power) because they produce power very close to the point of consumption and thus district heating and cooling becomes a viable way to heat and cool buildings in the “district” surrounding the power production facility.
  2. Finally transmission lines lose a significant amount of power both through leakage and resistance (I have heard numbers in the range of 10-25%).

Thus we have a practical rationale for the development of an Arcology that makes use of such technologies.

According to the APS website the benefits to businesses and real estate companies are:

  • Eliminates up-front capital expenditures
  • Creates attractive life cycle economics
  • Facilitates budget predictability
  • Reduces risk exposure
  • Reduces structural design requirements in new buildings
  • Eliminates and/or reduces electrical distribution for cooling
  • Increases space availability in building
  • Increases flexibility to add future cooling capacity
  • Eliminates costly maintenance and capital replacement expenses
  • Reduces average cost for kWh
  • Allows client to focus on core business
  • Provides 24/7 expert service
  • Strengthened energy infrastructure
  • Reduced emissions and pollution

Below are some pictures of the field trip:

Additions Related Articles and Resources:

  1. District Power Magazine Article about Northwind Phoenix:
  2. Wikipedia Definition of District Power which is also known and Distributed Power:
  3. Biz AZ Article about how the plant cools the water for the ballgames and more…
  4. Accolodes on APS’s work “Northwind(TM) Phoenix Garners Top Award from International District Energy” Association:
  5. A bit more of a techical explanation of the plant’s “INSTRUMENTATION & CONTROL systems”:

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