Nicknamed “The Big Green” years ago for the color of their uniforms, Ottoville Local School District, OH, can boast another big, green achievement. The new K-12 building, which opened in September 2003, features an energy-efficient geoexchange system for HVAC. This system, which relies on the earth’s stable temperature for its energy efficiency, not only saves the school district significant energy costs - it also influenced the standards of the Ohio School Facilities Commission and has convinced other schools to use similar HVAC systems that are efficient and cost effective.
From the very first plans, school officials required one major upgrade over the old building. The new school had to be fully air-conditioned. The older building was only partly air-conditioned; plus, the boiler-steam heating system was costly to operate. Knowing that a bigger school and complete HVAC system had the potential to boost energy costs significantly, officials sought a system that would mitigate projected cost increases. They based their solution on a life-cycle cost analysis that estimated significant utility cost savings and a relatively short payback period compared to a conventional central air-handling system.
The new geoexchange system relies on 88 McQuay® water source heat pumps to deliver heating or cooling to individual classrooms or other spaces. “It’s a cost-effective solution, particularly for schools, where spaces are not in constant use,” says Jeff Stringham, senior mechanical engineer, JDRM Engineering Inc. “Water source heat pumps can deliver either heating or cooling to only those classrooms that are in use. The advantage is that you don’t have to condition the entire school during periods of partial occupancy.”
Digging Deep for Energy Savings
Currently, Ottoville School has a student body of 590 in grades K-12 with a capacity for 850 students. When the small community in northwest Ohio voted to fund 17 percent of the new school’s cost via a bond levy, their investment paid for a 1-story, 131,000-square-foot facility with over 50 classrooms, a media center, multi-purpose “auditeria,” and two gymnasiums. It also paid for one of the most energy-efficient HVAC systems available at a cost comparable to a traditional system.
Geoexchange systems can reduce energy consumption - and corresponding emissions - by over 40 percent compared to electric resistance heating and standard air-conditioning equipment. Their simplicity further reduces costs. Geoexchange systems do not require chillers, cooling towers, or boilers, and the closed-loop water circulating system requires very little maintenance. During cold months, heat is transferred from the ground via the closed-loop circulating system to individual McQuay water source heat pumps. During warm months, heat is transferred out of the school and absorbed into the ground.
Most of the McQuay water source heat pumps are ceiling-mounted units, varying from one to six tons, which serve classrooms on an “as-needed” basis. Larger vertical floor-mounted units serve the gymnasiums, auditeria, and media center. Each space has a separate thermostat; direct digital controls manage the entire system.
Life-Cycle Analysis Sways the Commission
Despite the energy cost-saving advantages of a geoexchange system, it was not one of the four HVAC systems recommended by the Ohio School Facilities Commission (OSFC), which provides funding, management oversight, and technical assistance for the construction and renovation of all of Ohio’s schools.
“We conducted a life-cycle cost analysis, and the results convinced the commission to give us a variance to build the geoexchange system,” says Stringham.“The analysis estimated that the new school’s geothermal system would save $15,000 per year in utility costs compared to a conventional air-handling system. The utility costs are primarily for propane and electricity, as natural gas was not available in the area at the time of the analysis.” Stringham adds that the relatively short 4-year payback period also helped win the variance. “At the time, we estimated that the additional $60,000 for the system, primarily due to the additional cost required to drill the well field, would be paid off in 4 years by the utility cost savings,” explains Stringham. “We are currently estimating the systems, including the well field, to be approximately the same cost as a conventional system.”
Actual cost savings for operating the system far exceed expectations. According to Mike Ruen, treasurer and chief financial officer with the Ottoville Local School District, the school district paid 55 cents per square foot in utility costs (electricity and propane gas) during the 2005-2006 school year, or approximately $75,000. In comparison, OSFC estimates that an Ohio school district can expect to pay between $1.50 and $1.75 per square foot in utility costs for a new building that does not use geoexchange systems. “In other words, it is possible that we are saving in excess of $150,000 per year,” says Ruen.
Ruen also compares the costs of the new building with the previous building, and the original goal of keeping costs down. “Our complete utility costs (electric, propanegas, water, and sewage) in the second full year in the new building were 10-percent greater than the last year in the old building - and we’re working with a building that’s 33-percent larger than the older building.”
Setting a New Standard Pays Off for the Big Green
Ottoville Schools did more than mitigate energy cost increases with the new, larger school. Since opening its doors, Ottoville School’s energy-efficient HVAC system is recommended by the OSFC and is an example for other schools looking for quiet, energy-efficient systems. “From experience, we know that geothermal systems are cheaper to maintain and operate, and we don’t have to worry about the seasonal spikes in energy costs,” says Tim Kimmet, maintenance manager at Ottoville Schools. “We’re happy to be leading the way.” It’s just one more victory for the Ottoville Big Green.
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