Wireless technology enables a ski resort to make snow

For a northern Arizona resort, supplementing Mother Nature with manufactured snow provides a predictable ski season that could inject millions of dollars into the local economy. Controlled wirelessly, roughly 5.5 million litres of reclaimed effluent water from a nearby city would be needed daily to blanket the arid climate in fresh snow.

Since the 1930s, multiple resort and land owners attempted to develop the majestic San Francisco Peaks for recreational purposes. Located at approximately 2740 m, the seemingly ideal recreational area is littered with a history of developer bankruptcies, repossessions and foreclosures because of inconsistent snowfall.

With a consistent ski season, analysts speculate that tourists would spend an additional $23m a year at local hotels, shops and restaurants.

The obvious answer simply is to make snow. But that requires about 680 million litres of water per season to be supplied to the mountaintop resort in arid Arizona.

After considering numerous options, the resort’s solution was to pump treated wastewater to the facility and control the system with controllers from Rockwell Automation using a wireless ethernet network from Rockwell Automation Encompass Product Partner ESTeem Wireless Modems.

Wireless transcends distance

The physical separation of system components created a challenge. The rugged 24-kilometre distance between segments drastically increased the cost of fibre-optic installation, making that option cost prohibitive. Wireless communications provided the most cost-conscious solution available, spanning the distance with limited new infrastructure needed.

In addition, implementing a wireless control system provides the flexibility to program and install the network in a matter of days and at a fraction of the cost of a fibre-optic network.

How ethernet makes snow

A local system integrator in Payson, Arizona, designed the system and chose Rockwell Automation-based control using ESTeem Wireless Modems for the control network. To maintain signal strength in the rugged terrain, wireless modems were mounted directly outdoors on antenna masts.

ESTeem, which manufactures high-speed, wireless ethernet modems, provided the hardware to cover the long distances between the ethernet segments while maintaining high data rates.

After successfully completing an initial radiofrequency (RF) analysis using modelling software, the system integrator conducted an on-site RF site survey. Thorough RF testing at each location validated the results of the software model and demonstrated successful communications. The ESTeem Model 195Ed was selected for this application. It operates in the licence-free, 900 MHz frequency band with RF data rates to 54 Mbps.

The 900 MHz frequency was chosen for its ability to tolerate the rugged terrain and provide reliable high-speed communications. Standard spread spectrum radio modems operating in the 900 MHz band have a much lower data rate and wouldn’t have provided the data rates or range needed. A clear radio pathway between antennas, called a line of sight (LOS), greatly increases the reliability of a wireless network. To maintain LOS, the ESTeem wireless modems were mounted directly outdoors on antenna masts. This mounting method eliminates the high cost and signal degrading of coaxial feedlines.

Each wireless link was tested for receive signal strength, frequency interference and data rates prior to installation. Once installed and configured, the modems form a single ethernet control network.

The individual locations communicate using a common EtherNet/IP protocol, allowing them to operate as a single network. The wastewater treatment plant acts as the system master. A ControlLogix programmable controller from Rockwell Automation retrieves tank levels from a primary holding tank located across town via an ESTeem wireless communication link.

Based on current tank levels, produce and consume data are exchanged with a booster station via another link to provide the needed water to meet demand. Water is then pumped directly from the holding tank to the mountaintop resort nearly 24 kilometres away. An estimated 5.5 million litres of treated water is used daily for snowmaking. For this challenging application, the ethernet-based control system using controllers from Rockwell Automation and ESTeem Wireless Modems provided an effective solution at a fraction of the cost of fibre optics. As technology continues to evolve and application demands advance, wireless communications will continue to replace physical connections as a cost-effective communication solution.

By Don Tolley, Product Specialist, ESTeem Wireless Modems

Reprinted with permission from The Journal from Rockwell Automation and Our Partners, copyright 2012 by Rockwell Automation, Inc and Putman Media, Inc.