University of Wisconsin ripping out coal boilers in favor of gas-fired system

The University of Wisconsin is in the process of ripping out coal-fired boilers at the Charter Street Heating Plant and replacing them with gas-fired facilities.

John Harrod Jr., who works at the University of Wisconsin-Madison as Director of Physical Plant–Facilities Planning and Management, provided testimony filed Aug. 27 at the Wisconsin Public Service Commission in a review of an application of Madison Gas and Electric for authority to change electric and natural gas rates. The purpose of his testimony was to provide background information regarding UW’s energy needs, its relationship with Madison Gas and Electric regarding the West Campus Cogeneration Facility (WCCF) and UW’s future energy plans.

The UW Campus district energy system provides steam, chilled water, cogenerated electricity and compressed air. The district energy system is composed of three major facilities: Charter Street Heating Plant (CSHP); Walnut Street Heating Plant (WSHP); and WCCF. The system is operated as an integrated district energy system with multiple boilers, chillers, and compressors, and one steam turbine generator (STG) to serve the UW load for each of those energy needs.

The CSHP delivers heating and cooling to the campus and also generates about 9 MW of electricity via a back pressure steam turbine generator. The CSHP is in the midst of a $188.3m construction project. It will remove the existing coal-fired boilers and replace with four gas/oil fired boilers, each rated at 225,000 pounds per hour (lb/hr). The project will also provide a new water treatment system and mechanical, electrical and control system replacement and upgrades. The CSHP will be completed in the fall of 2013.

WSHP is located adjacent to WCCF on the west side of the Campus producing steam from three gas/oil-fired boilers. No electricity is produced at WSHP. The WSHP steam output is utilized for steam turbine-driven chillers, and is interconnected into the UW Campus steam system for space heating and process purposes. In addition, a new electric-driven chiller was installed in the fall of 2010 at WSHP. The chillers produce chilled water for distribution throughout the UW Campus for building air conditioning.

WCCF is jointly owned by an MGE affiliate, MGE Power (56%) and UW (44%), and consists of: a combined cycle cogeneration system that produces about 150 MW for MGE customers and 400,000 PPH of steam output for campus distribution; and a four-unit electric-driven chiller system (about 17 MW) that produces chilled water, also for campus distribution. The combined cycle cogeneration system consists of two about 60 MW STG gas-fired combustion turbines with the hot exhaust gas fed into heat recovery steam boilers that in turn feed steam into an approximate 45 MW STG.

Under a Joint Ownership Agreement, MGE has the right to WCCF electricity and UW has the right to WCCF steam and chilled water output, Harrod noted. The university can call on WCCF for firm steam production during winter months from October through April 14 and interruptible steam service for non-winter months when WCCF is dispatched by the Midwest Independent System Operator (MISO) to produce power. UW is not required to take the steam produced by WCCF during MISO-dispatched operations but usually does due to a discounted steam price.

The four UW-owned chillers co-located at the WCCF are rated 5,000 tons per hour. These chillers use Station Service electricity and are not charged demand charges. As a co-owner of the facility that includes electric facilities, UW was entitled to electric output to serve these chillers without paying MGE for capacity charges. Among the considerations for UW’s approximate $90m investment in WCCF, MGE and UW agreed that the facility chillers would be supplied by Station Service which was defined to be the production cost of electricity.

UW is in the process of rebuilding the CSHP plant to extend its life another 50 years, Harrod said. The CSHP Rebuild Project will replace three existing coal-fired boilers with four new natural gas/oil-fired boilers. Two boilers were installed in late 2011 and two boilers are being installed in 2012; all feeding into the existing 600 psig common header. When the CSHP Rebuild Project is complete in 2013, UW will still rely heavily on MGE to serve UW electricity loads during peak and intermediate load periods.

The CSHP Rebuild Project is going a long way to improve not only the reliability of the steam and chilled water operations but also improve electric generation reliability. When complete, the five boilers (four new and one existing natural gas fired) will be equipped with a state-of-the-art digital control system capable of precise load control and quick reaction to potential upset conditions. High pressure steam (600 psig) from these boilers drives the steam turbine coupled to the electric generator. Early in 2012 the high pressure steam piping to the steam turbine was modified to eliminate a restriction that limited the maximum electrical output of the generator. In the fall of 2012, the digital control system will be expanded to control and monitor the steam turbine generator package.

As part of the CSHP Rebuild Project, two new 225,000 PPH gas/oil boilers were installed at CSHP in the fall of 2011. With these new boilers in service, the existing coal-fired boilers have been retired and all coal use at CSHP has ended. At this point, the UW Campus steam production is 100% fueled by natural gas/fuel oil.

About Barry Cassell 20414 Articles
Barry Cassell is Chief Analyst for GenerationHub covering coal and emission controls issues, projects and policy. He has covered the coal and power generation industry for more than 24 years, beginning in November 2011 at GenerationHub and prior to that as editor of SNL Energy’s Coal Report. He was formerly with Coal Outlook for 15 years as the publication’s editor and contributing writer, and prior to that he was editor of Coal & Synfuels Technology and associate editor of The Energy Report. He has a bachelor’s degree from Central Michigan University.