Schools Save Energy with CHP
Combined heat and power facilities help schools meet energy and emissions goals
With elementary and secondary schools tightening their purse strings, and with post-secondary institutions seeing a drop in enrollment numbers over the past couple years, schools across the nation are looking for ways to cut costs. Increasingly, they are turning to cogeneration as a way to save money while also being more environmentally friendly. And, while cogeneration is still largely an industrial process, the market has significant potential for educational institutions coast to coast.
COMBINED HEAT AND POWER
Combined heat and power (CHP), also known as cogeneration, is the simultaneous production of electricity and heat from a single fuel source, such as natural gas, biomass, biogas, coal, waste heat, or oil. According to the U.S. Environmental Protection Agency (EPA), the two most common CHP system configurations are a gas turbine or engine with heat recovery unit, and a steam boiler with a steam turbine.
“For us, we take natural gas and we run an engine, the engine makes electricity, and the heat that’s generated through that process is used to provide heat to the building,” said Benjamin Locke, co-CEO of American DG Energy, a provider of on-site energy solutions. “You install this [Tecogen Inc.] unit in your building and hook it up to your electrical panel and your hot water loop, and the electric meter is not running as fast because you’re making your own electricity, and the boilers aren’t turning on as much.”
American DG Energy recently completed an installation at Wolman Hall student housing at The Johns Hopkins University in Baltimore. Through a purchase of power agreement with Johns Hopkins, American DG Energy is now operating a 75-kW CHP system that will help the university offset up to 415 tons of CO2 per year.
“At Johns Hopkins, we used one 75-kW module because it fit their needs,” Locke said. “We place the number of units that matches what the electric and thermal loads are for those buildings. Having cogeneration in your building is much more efficient and economical than getting those two sources — electricity from the grid and heat from the boiler — separately.”
Hot water or steam produced by electrical generation can also be used in absorption chillers in order to air condition large commercial buildings. According to the EPA, since absorption chillers can make use of waste heat, they can essentially provide free cooling in certain facilities.
A GROWING MARKET
When coupled with the peace of mind a stable power supply provides, the energy savings and reduced emissions associated with CHP have helped propel the market forward, especially as many public schools struggle to stay afloat while funding and enrollment decrease.
“What’s happening in higher education is that colleges and universities are innovating and adapting their traditional classrooms,” said Charles McGinnis, senior director of higher education for North America, Johnson Controls Inc. “They’re delivering education online, which is very different from the traditional classroom model. … Because of that — and the changing dynamics between community college and higher education, where a lot of people are going to community college for the first two years — and the general decline of the number of people graduating from high school, higher education is challenged to figure out how many students are going to be enrolling in their campuses in the next five to seven years.
“Because of this new way of teaching and the decline of potential students, it’s forcing them to look at their facilities,” McGinnis continued. “The construction boom is no longer happening. … There’s a decline in funding at public universities, in particular, and it’s forcing them to look hard at tuition, which is about 75 percent of their revenue. So, what they really need to do is save money on operations. Every dollar saved in energy can be redirected to the classroom.”
Trane, a brand of Ingersoll Rand, provides heat recovery, pumps, chillers, and other solutions for CHP plants in schools, hospitals, manufacturing facilities, wastewater treatment facilities, and other similar applications. John Gabbard, director of engineering and construction, Trane Renewable and Power Solutions, said CHP on college campuses is “a great market” that will continue to grow.
“Many university and college central plants are undergoing changes and expansion to meet the ever-changing needs and modernization of their facilities,” Gabbard said. “The application of CHP during these times is excellent. Rather than simply installing additional conventional electric chillers and boilers, a CHP plant provides the option of installing this same equipment fueled by the heat recovered from electric generation. The installation of the equipment is not simply a capital expense, but a revenue-generating cost with a very attractive payback period.”
The system Trane designed and installed at Pacific Union College in Angwin, California, utilizes a gas turbine to generate 1.2 MW of base load electricity and 10,000 pounds per hour of steam, which is distributed throughout the main campus steam system for heating during the winter and directed to fuel a steam absorption chiller for cooling during the summer.
“Universities that are big enough to do cogeneration — and there are many out there — own and operate extensive insfrastructure,” Gabbard added. “That market is very big.”
At Stanford University in Stanford, California, engineers recently transformed the campus’ gas-fired CHP plant, which had produced 90 percent of Stanford’s greenhouse gas (GHG) emissions and consumed 25 percent of the campus’ potable water supply since it was commissioned in 1987, to a Central Energy Facility (CEF) powered mainly by green energy that has helped cut its water use by 15 percent and is projected to save $420 million in operational costs.
Developed with help from Johnson Controls, the CEF utilizes efficient building technologies, including heat recovery chillers (HRCs), hot and cold water thermal energy storage, and a patented smart technology system that uses weather and electricity pricing forecasts to optimize operations.
York heat-recovery chillers will meet more than 90 percent of campus heating demands by capturing almost two-thirds of the waste heat generated by the campus cooling system to produce hot water for the heating system. Along with a Metasys building automation system, Johnson Controls’ Enterprise Optimization System will optimize cost and energy use based on the 10-day weather forecast and future grid electricity prices and determine how much hot and cold water to store in the CEF’s water thermal storage tanks. In all, the custom-engineered heat-recovery process is 70 percent more efficient than the old CHP process.
“The beauty of the HRCs is that we’re filling up these thermal storage tanks when energy is cheapest and using that in tandem with the chillers to heat and cool campus,” said Maurice Hatchett, installation manager, Johnson Controls Inc. “The whole thermal energy concept is really catching on in a lot of places we’ve seen, and we’d much rather generate green energy via wind, solar, or hydro and use that to make heat.”
“Stanford is really beyond cogeneration — this is the next logical step,” said Robert Turney, engineering fellow and advanced development lead, Johnson Controls Inc. “What we’re really doing is using green energy to combine heating and cooling.”
“Stanford is happy with what they’re seeing,” Hatchett added. “This was a dream a couple of years ago, but now we’re walking around campus, and there are surgeries going on in these buildings. And, a large part of the time, we’re just circulating stored water.”
In addition to the inherent energy and monetary savings, the energy independence created through CHP will only continue to benefit forward-thinking school campuses and facilities, especially as energy costs continue to rise.
“Having a central plant as a reliable and efficient source of electricity and thermal load is really important,” McGinnis said. “By being self-sufficient with a central plant, they have better control over their future, and they can avoid unforeseen costs the utilities may charge.”
Publication date: 8/3/2015