Ground-source heat pumps — energy-efficient heating and cooling systems Lincoln Public Schools has installed in nearly all its buildings — aren’t as efficient as they should be at three high schools.
District officials say they can solve the problem by spending $1.1 million to add equipment to the systems at North Star, Southwest and Southeast. No other schools have had similar issues, Lincoln Public Schools Operations Director Scott Wieskamp said.
“I know it’s a big investment, but I don’t feel that it’s a bad investment,” Wieskamp said. “I think it’s a course correction.”
Because ground temperature remains relatively stable despite the temperature swings above ground, geothermal systems use the ground as a sort of radiator to heat and cool water that’s then circulated through systems that regulate temperature in the buildings.
LPS installed its first geothermal systems when it built Campbell, Cavett, Maxey and Roper elementary schools in 1995. Wieskamp, who wasn’t working for LPS at the time but did work for one of the architectural firms hired to build the schools, said the district was encouraged by Lincoln Electric System to try what was then a very new technology.
District officials decided to install the more-expensive ground-source systems in the elementary schools, but use traditional systems in Lux and Scott — two new middle schools it was also building — and compare the energy costs.
Replacement parts are less for geothermal systems, and the energy rate the district is charged also is less, Wieskamp said.
“The geothermal proved itself heads-and-tails above the other,” Wieskamp said. “The energy per square foot of those elementaries is almost half of what it cost to heat the other buildings.”
Initially, energy costs at Scott and Lux were $1.40 to $1.45 a square foot — about $230,000 a year. LPS has made some improvements and reduced costs to $1.15 to $1.20 per square foot, saving about $40,000 a year.
Compare that to Irving Middle School, which recently got a geothermal system. Annual utility costs went from $1.01 a square foot to 57 cents a square foot, a savings of more than $81,000 a year.
As the district built more schools, it continued to use the geothermal systems, and North Star and Southwest were the first high schools to get them.
The first existing school that got a geothermal system was Elliott Elementary in 1999. Energy costs there today are about 80 cents a square foot, Wieskamp said. He estimated the cost was at least a dollar a square foot before that, when the school wasn't air-conditioned.
One of the major parts of the $250 million bond issue in 2006 was replacing systems at existing schools — many of which were not air-conditioned — with geothermal systems that both heated and cooled them. Cost of retrofitting the buildings — which also got new roofs and other energy-saving updates — was between $70 million and $75 million, Wieskamp said.
Southeast was the first of the older high schools to get a geothermal system. Today, all schools but Scott, Lux and Park middle schools and Everett Elementary have them.
In recent years, though, LPS started noticing issues at North Star, Southwest and Southeast. District officials look at energy consumption, building use and ground temperature, as well as energy costs. They noticed water circulating through the pipes at the high schools was warmer than it should be.
"We've been watching this for several years," Wieskamp said. "We cannot afford to let the well fields heat up."
The savings were diminishing — the annual cost of heating the schools ranges from about $450,000 at Southeast to nearly $500,000 at North Star, and Wieskamp estimated the district is spending between $50,000 and $60,000 more a year for all three buildings than it was when the geothermal systems were first installed.
The biggest concern was that ground temperature had risen, which means systems weren't cooling as effectively, largely because the buildings are being used more than anticipated, especially in the summer months, Wieskamp said.
Essentially, the water being “rejected” or sent back into the ground is warmer and that’s heating up the ground.
"I can't afford to have the system ... being overloaded due to excessive use or more use than anticipated," he said.
District officials could add more water pipes to the well, but that's more expensive, and while it would keep the ground from heating further, it wouldn't cool the ground as quickly.
Instead, the district wants to buy equipment that will be mounted on the schools’ roofs that will help cool the water before sending it back through pipes into the wells, Wieskamp said, supplementing the cooling process of the ground.
The Lincoln Board of Education will consider the low bid of $1.1 million from Hayes Mechanical in La Vista on Tuesday. Two other bids came in at $1.4 million and $1.6 million.