September 2009

Why UNC has (cling, clang, sss) steam heat

The neighbors closest to our campus have been incredibly patient as Carolina has undertaken projects to improve our energy infrastructure, including repairs to the steam tunnel that connects our cogeneration facility on Cameron Avenue to the rest of the campus.

At the university, we are well aware of how important steam and our cogeneration plant are to our operations, but I'm not sure if that knowledge extends beyond campus. So let me tell you the basics of how we generate energy at the UNC cogeneration facility and how we plan to do that even more sustainably in the future.

The combined heat and power (also called cogeneration) system at UNC uses our cogeneration facility to primarily generate and distribute thermal energy (steam). This centralized, or district energy, system is much more cost-effective and energy efficient than locating heating and cooling equipment (boilers and chillers) within individual buildings. Most institutions with dense campuses such as ours use district energy technology and distribute heat in the form of steam or hot water and cooling in the form of chilled water.

Steam from our cogeneration facility is piped to 175 campus buildings, including UNC Hospitals, for heating, humidification, hot water heating, sterilization and making distilled water in laboratories. This steam is also used to generate electricity, with the capacity to meet one-third of the university's peak demand. This dual function results in an overall thermal efficiency that is twice that of any plant built solely for the purpose of power generation. The power generated this way is also much more efficient and cost-effective than that purchased from the grid.

Some individuals and environmental groups have expressed concern that the cogeneration facility uses coal. In the future, we do plan to move beyond coal. Meanwhile, we have taken steps to reduce the environmental impact of our coal usage as much as possible. The coal that we purchase is not mined from mountaintops, according to our suppliers. (Most of the coal is deep mined, but a small portion is from surface mines.) Also, 100 percent of our coal ash is used as structural fill or as an agricultural and horticultural soil supplement.

Even though it uses coal, our cogeneration plant has won multiple awards for cleanliness and efficiency from the U.S. Environmental Protection Agency Energy Star Combined Heat and Power program. The EPA recognized the university's system for reducing greenhouse gas emissions in 2008 equivalent to taking 9,011 passenger vehicles off the road. We also use special technology within the plant to reduce emissions of sulfur dioxide and nitrogen oxides.

Still, with new technology in the future, we certainly plan to replace coal over the long term. That strategy is detailed in our new Climate Action Plan (http://www.climate.unc.edu/portfolio/), recently submitted to the American College and University Presidents Climate Commitment as part of our pledge of carbon neutrality by 2050.

Part of that plan is to replace 20 percent of the coal we use with torrefied wood (a charcoal-like substance) by 2025. (Because the coal-fired boilers that give us the advantage of cogenerating power must use solid fuel, we can't make a complete switch from coal overnight.) In the mid- to long-term, solar thermal panels, heat recovery chillers and a biomass gasification plant could provide additional carbon abatement.

I hope that I've explained why the steam tunnel repair that has been so inconvenient for our neighbors is so vital to the university. If you want to learn more, please arrange for a tour of our cogeneration facility. We'll show you why we like our (cling, clang, sss) steam heat.