Lake Of Egypt Temperature Buoy Profiles Effects Of Power Plant Discharge

By on August 12, 2015

A NexSens CB-450 Data Buoy supports a GPS receiver, thermistor string and radio data logger on Lake of Egypt. (Credit: Southern Illinois Power Cooperative)

Illinois’ Lake of Egypt provides a lot for the nearly 8,000 people living around it. Drinking water is first on the list, followed by boating and fishing opportunities. But its waters also help to provide something they don’t have to be on the lake to enjoy: electricity.

The lake’s water is the main coolant used by a coal-fired power plant sitting on its banks. It’s operated by the Southern Illinois Power Cooperative, where employees have, for years, managed the temperature of water discharged back into Lake of Egypt using calculations. The method relied on temperature readings taken at the discharge point, which were then used to estimate conditions further out into the water body. The concern, like at many other reservoirs used by power plants, was that inappropriate discharge temperatures could negatively impact aquatic life.

Thankfully, plant managers no longer have to rely on estimates, as the Cooperative recently installed a data buoy in Lake of Egypt to let managers know exactly what’s going on in real time. The installation was also completed weeks before the U.S. EPA asked the plant to begin collecting continuous temperature data on the lake, meaning its operations were kept in line with permit requirements of the National Pollutant Discharge Elimination System.

“Because of this work, we had it ready before the EPA asked for it,” said Leonard Hopkins, vice president of fuel, environmental and safety at the Cooperative. “From that standpoint, I’ll give our company a pat on the back.”

At the center of the platform is a NexSens CB-450 Data Buoy. Hopkins says a buoy was chosen for the project over other options because of the changing levels of Lake of Egypt. Given those fluctuations, a buoy was the best option because it would rise and fall along with them.

Plant managers keep track of the buoy’s location on the water via a Garmin GPS receiver that sits on its topside next to a solar marine light. This acts as a beacon for boaters during nighttime hours. Below the platform and securely deployed in one of the buoy’s pass-through holes is a string of NexSens TS210 thermistors. Running vertically through the lake’s water column, these sensors capture temperature changes in a profile, which allows managers overseeing discharge operations to know exactly how the lake’s strata are affected.

A thermistor string is made of a series of connected temperature sensors. (Credit: NexSens Technology)

Measurements from the Garmin and TS210 string are recorded by a NexSens iSIC-CB Buoy Data Logger housed in the buoy’s instrument well. This logger is equipped with radio telemetry that lets it transmit readings to a base station in the plant every 10 minutes.

“I believe the temperature readings are logged every 15 seconds, but we limit that to report once every 10 minutes,” said Hopkins. “We only need an average hourly temperature, so there’s no need to run it every 10 seconds.”

In addition to helping the plant meet regulatory requirements, Hopkins says the buoy will help chart seasonal changes in Lake of Egypt, and officials at the plant are looking into adding another buoy in the future. It would be deployed further away from the discharge point and monitor ambient temperature changes.

Picking where to deploy a second buoy would be a little tough, he says, because the large lake does a good job of dissipating the heat released into it. At a certain distance out into the reservoir, there simply isn’t an effect to measure.

“We’d have to figure out where else in the lake is ambient. All our options are open at this point,” said Hopkins. “The buoy we just launched is a prototype for us, and we want to make sure it all pans out. But it’s a fairly inexpensive way of continual temperature measurement.”

Top image: A NexSens CB-450 Data Buoy supports a GPS receiver, thermistor string and radio data logger on Lake of Egypt. (Credit: Southern Illinois Power Cooperative)

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