Below the Surface
- By Michael Fickes
- April 1st, 2012
Back in 2009, officials at Ball State University in Muncie, IN, took a deep breath and broke ground on what will become the largest geothermal heating and cooling system on a college or university campus in the United States.
“This is a district ground-source geothermal heating and cooling system,” says Jim Lowe, director of engineering, construction, and operations for Ball State. “It uses a vertical ground-loop heat exchanger.”
When complete, the $80M system will include 3,600 vertical boreholes between 400- and 500-ft. deep, tied together with more than 1,000 miles of piping. Equipped with four heat-pump chillers, the system will heat and cool almost all of the 47 buildings on the University’s 731-acre campus. A couple buildings are too far away to be linked into the system economically.
In March, phase one of the system came on line and began heating and cooling about half of the campus.
It’s working, and it is very efficient. “When you burn something like coal for energy, you don’t get all of the heat value,” says Lowe. “Coal is about 75 percent efficient when you burn it. During distribution, you lose more of that efficiency. The system might be 60 percent to 70 percent efficient. “But with our geothermal system, we pay $1 for electric power to run the system and get $7 in energy value back.”
Phase two has begun construction, which will continue through 2014.
How Geothermal Works
In the Ball State system, heat pump chillers condense a refrigerant to remove heat from the air and make chilled water for cooling, says Lowe. The by-product of that process will be hot water that can then be used for heating. In other words, the same system makes hot and cold water.
Geothermal systems work because of the Second Law of Thermodynamics, which says that heat energy flows from higher temperatures to lower temperatures. Above ground, the temperature of the air varies with the seasons. It might spike to 90°F in the summer and plunge to 0°F or below during the winter. Below ground, however, the temperature of the earth varies very little, perhaps from 40°F to 80°F.
In the winter, cold water flowing through an underground geothermal piping system picks up heat from the warmer earth. A heat pump amplifies that heat and heats water, which then heats a building. In the summer, the process reverses, and hot water flowing through the underground geothermal piping systems transfers heat to the cooler earth. The heat pump removes more heat from the water, which allows the air in a building to cool.
Ball State’s heating and cooling system will consist of two closed loops of piping. One will carry cold water at a temperature of 42°F, and the other will carry hot water at a temperature of 150°F. That’s important because in a complex campus, some spaces — such as buildings housing computers — need cool air even in winter, while the neighboring buildings need heat. “Our cooling needs increase in the summer and decrease in the winter,” Lowe says. “Likewise, heating needs increase in the winter and decrease in the summer. But we’re always using both.”
The Path to Geothermal
How did Ball State decide to forgo conventional heating and cooling and turn toward a green solution like geothermal?
The selection process started back in 2004, when the U.S. Environmental Protection Agency (EPA) tightened emissions regulations for coal-fired boilers. At that time, Lowe’s team was evaluating the life expectancy of four coal-fired boilers that had been installed in the 1940s and 1950s and three natural gas-fired boilers installed in the 1960s and 1970s.
“As you know, enrollments on college campuses exploded during the 1950s and 1960s,” Lowe says. “That created capacity issues for us. On top of that were the new EPA regulations. So we began thinking about a new circulating fluidized bed boiler (CFB) to produce steam and pipe it to campus, where it would make hot water for heating and domestic purposes.”
A CFB would boost efficiency by 16 percent and reduce carbon dioxide emissions. The technology would allow Ball State to burn both coal and a renewable alternative fuel such as wood or switchgrass. The plan was to fuel the boiler with a 70 percent to 30 percent mix of coal to an alternative.
The system would still need emission controls for particulate matter, sulfur dioxide, nitrogen oxide, and carbon monoxide.
As the plan came together, Lowe began estimating costs. “In 2008, the cost of this project increased significantly,” he says. “The estimates were around $65M. At that point, we started to think about other ways to make steam — with natural gas or some kind of solid fuel.”
Lowe investigated firing the boilers with natural gas. Back then, however, natural gas prices were reaching record highs, and Lowe kept looking for alternatives.
“Eventually we wondered if we could heat and cool our buildings with a renewable energy like geothermal.”
Geothermal technology had been around for a number of years. It had been used successfully to heat and cool individual buildings, but could it hand a district-wide system? “I had never heard of this,” Lowe says, “but we decided to study it.”
Lowe contacted the Oak Ridge National Laboratory in Oak Ridge, TN, and the National Renewable Energy Laboratory with offices in Golden, CO, and Washington, DC.
Lowe’s National Lab contacts introduced him to MEP Associates, LLC, a multi-disciplinary engineering consulting firm specializing in the design of complex facilities such as large geothermal heating and cooling systems. “At that point, we had started talking about a system that would distribute hot water for heating as well as cold water for cooling — from the same plant,” Lowe says.
Cost and Payback
MEP designed the Ball State closed-loop geothermal heating and cooling system, and the installation work began in 2009. With an $80M price tag, the system will cost $15M more than the proposed CFB system.
Several considerations will make the higher priced geothermal system work for Ball State.
“First, we’re no longer going to burn coal,” Low says. “If EPA regulations on coal-fired boilers tighten again, we won’t feel any effect. Second, we spent about $3M per year on coal for the coal-fired boilers. With the geothermal system, we won’t have to buy coal anymore.”
Lowe will need to buy more electric power to run the heat pumps, but the extra electricity will only cost $1M, producing an annual net savings of $2M. By saving $2M per year, the geothermal system will pay off the $15M extra capital cost in seven to eight years. After that, Ball State can put the $2M to work elsewhere.
Then, of course, there are the sustainable environmental benefits of geothermal heating and cooling.
The Big Green
By not burning 36,000 tons of coal
per year, Ball State will eliminate
85,000 tons of carbon dioxide emissions annually and reduce the campus’s
carbon footprint by half. Eliminating
coal will also eliminate 240 tons of nitrogen oxide emissions, cut particulate matter emissions by 200 tons, slash
sulfur dioxide emissions by 1,400 tons, and reduce carbon monoxide emissions by 80 tons.
That’s a lot of green.