Solar Powered Air Quality Monitor Operating Near Weeping Water

Article by Richard Webster

Weeping Water. This poetic-sounding name was given to a creek in southeast Nebraska by Native Americans (the creek was called “the weeping waters”). The town of Weeping Water eventually grew alongside the creek. But it is not water, weeping or otherwise, that now distinguishes this area. Rather, it is a rock formed over thousands of years when the Weeping Water area was covered by a warm, shallow sea. Extensive deposits of marine organisms and other debris on the floor of this sea were transformed over time into what we call limestone.

There is no doubt about the importance of limestone to the Weeping Water area. At the entrance to the town sits a “Welcome to Weeping Water” greeting – constructed, of course, of limestone. And the town’s claim to fame? The Limestone Center of the Nation. Summer finds the town celebrating Limestone/Independence Day.

Six major limestone quarrying and aggregate operations are vital to the area’s economy. Limestone quarrying and associated crushing and transportation activities produce large quantities of dust that must be controlled through various means. Control is important because high levels of dust particles inhaled into the lungs can contribute to respiratory illnesses. Due to the presence of the limestone industry, the Nebraska Department of Environmental Quality (NDEQ) has operated particulate air quality monitors in Weeping Water since soon after the department’s creation in the early 1970s.

In 2003 NDEQ expanded its monitoring network by placing a new monitor in a Weeping Water park. The department also decided to expand the network outside (but still nearby) Weeping Water. Due to the requirements of the new monitor and associated meteorological equipment (close to an area considered vulnerable to particulate emissions, close to a power source, unobstructed landscape for 300 feet in all directions) traditional sites were all eliminated.

The search for a location to place a new air quality monitor eventually led to the farm of Kenneth Lauritzen, a local landowner and farmer. Mr. Lauritzen agreed to allow a small portion of his cropland to be used to site the monitor. NDEQ’s plan to tap into a nearby electrical substation was found to be unworkable, though. The department’s alternative plan to run power from Mr. Lauritzen’s farmhouse was found to be too expensive.

When it looked as if the Lauritzen site might have to be abandoned, NDEQ staff decided to explore the possibility of using alternative power sources. Following extensive research, Air Quality program staff settled on a unique solution to the power problem: they would use photovoltaic, or solar, power to operate the new monitoring station.

“We considered wind power because it is approximately one quarter the cost of solar power per watt of power generated,” said Chris Hetzler, NDEQ Air Quality Program Specialist. “Based on wind data we had collected at a nearby monitor, though, it turned out that a site powered solely by wind power was unfeasible because the average wind speed is too low. Solar power is workable about anywhere, however. It’s just a matter of having a large enough array of panels and enough batteries to run through the night and on cloudy days.”

NDEQ began constructing the solar powered monitoring station in January 2005. Work was completed in April 2005. The completed air monitoring and meteorological station (see photos) consists of:

When the Weeping Water photovoltaic system became operational on April 8, 2005, it was the first known air monitoring application of photovoltaic power of this scale (Pima County, Arizona operates a small solar powered carbon monoxide monitor). The Weeping Water monitoring site has performed well, delivering a steady stream of data to DEQ’s Lincoln headquarters. The system has shut down just once, for three days, when snow covered the solar panels and staff were unable to reach the site and clear the panels.

Reducing power consumption to only the essential monitoring operations was a key to the success of the project, according to Hetzler. “The real challenge at this site was determining what was absolutely essential for monitor operations to reduce power consumption. We knew from the beginning that we would have to do without air conditioning and heating in the trailer. Designing passive heating and cooling systems allowed us to use much less electricity and still maintain the trailer’s temperature within the operational range for the monitoring equipment. Greatly reduced power consumption meant that photovoltaics would be a viable alternative to grid power. Monitors that do not require grid power allow environmental agencies much greater freedom when siting air monitors.”

As with any completed project, the Weeping Water photovoltaic system project has lessons to offer, Hetzler said. “We have concluded that renewable energy is a viable alternative in many situations and when a renewable system is properly designed, it is comparable in reliability to grid power.” He also feels that, as an environmental agency, NDEQ should look for ways to set examples, and the Weeping Water project offered such an opportunity. “This project convinced us that reducing energy consumption is good practice all the time, not just when designing renewable energy systems.”

Additional information about the Weeping Water solar powered air quality monitor is available by contacting Chris Hetzler (402-471-0007) or Brad Pracheil (402-471-4141) of NDEQ’s Air Quality Compliance Section.
The document “Design and Deployment of Ambient Air Monitors That Utilize a Photovoltaic Power Source” is available at the following link:

Nebraska Department of Environmental Quality
1200 "N" Street, Suite 400
P.O. Box 98922
Lincoln, Nebraska 68509
(402) 471-2186