Cellular One Cell Towers

After the HVAC energy conservation measure savings and improvements were validated with an investment grade kWh meter, CellularOne deployed this ECM, now in its 4th generation, called CryoGenX4, in every one of the hundreds of cell towers they own and operate.

This case study details the results of the completed comprehensive energy performance study conducted at one of the CellularOne cell tower shelters located nearest to their headquarters in Show Low, AZ.

Running from August 21 to October 5, 2015, the pilot was designed to illustrate the positive impact the energy control measure -- referred to as the “ECM” -- would have on the performance of the wall-mounted cell tower shelter air conditioning system.

As shown in this field demonstration, the ECM restores the capacity of cooling systems lost over time due to fouling of the heat exchange surfaces.

The ECM will benefit CellularOne in all of the following ways:

-Restore capacity of the cooling systems to better satisfy fluctuating shelter loads

-Produce additional cooling system redundancy at no extra cost or interruption to operations

-Improve cooling system efficiency, lowering cost to produce each ton of cooling required

-Restore thermal efficiency, allowing cooling systems to achieve thermostat set points faster and shut off sooner

-Improve cooling system performance, reducing runtime and extending equipment life by 20% or more

-Reduce amp draw, kW and overall kWh consumption

-Reduce operating system pressures in compressors, reducing unscheduled service calls

The location chosen for this field demonstration is a standard cell tower shelter supported by two nominal 3-ton wall-mounted cooling systems operating in a redundant fashion. The systems are rotated bi-monthly, so runtime on each is balanced out over time. The primary cooling system is normally set to 73 degrees as it was for the pilot, while the back-up cooling system is set for 78 degrees. It only operates when the shelter load gets so heavy that the single cooling system can no longer keep up or it malfunctions. Only the primary unit was operated for this demonstration.

Field Demonstration Highlights

When comparing the pilot cell tower cooling system before and four weeks after the ECM was installed, below are some of the highlights of the field demonstration:

• When initially tested, the pilot system was producing 2.35 tons of cooling. Four weeks after installation, the cooling capacity jumped by .48 tons, or 20.4% to 2.83 tons.
• The overall cost to produce each ton of cooling on the pilot system dropped 25.4% from 2.01kW/ton in the baseline to 1.5 kW/ton four weeks after installation of the ECM.

This means that for every ton of cooling the pilot system is asked to produce, CellularOne is spending 25.4% less money to do so.

• The projected annual kWh’s were reduced by 25.3% from 17,070 to 12,750.
• The conditions inside the cell tower shelter remained constant at 73 degrees while the cooling system ran less but produced more tonnage.
• The average kW dropped 10.1% from 4.72 in the baseline to 4.25 in the post when comparing multiple hour-long blocks of time under similar outdoor air temperatures affecting the condensing units.