Local utility helps fund a microturbine to provide emergency power and peak-load shedding

Innovative partnership with the educational community and the local utility helps fund a microturbine for the City of Milwaukee

Venu J. Gupta
Director, Buildings and Fleet
City of Milwaukee, Wisconsin
Member, APWA Facilities and Grounds Committee

In January 2003, the installation of a 60 kW microturbine (electrical generator) was completed at the City of Milwaukee's Anderson Municipal Building (formerly Lake Tower). The Milwaukee School of Engineering will monitor the microturbine and the associated heat recovery as an academic research project through use of Internet-based communications.

The total estimated cost was $150,000, broken down as follows: a grant from WE Energies (local utility) - $50,000; a grant from Focus on Energy (administered by Milwaukee School of Engineering) - $50,000; City portion of funding - $50,000.

Traditionally, the Department of Public Works would fund the installation of a conventional emergency generator as part of a remodeling project from the City's Six-Year Capital Program. All high-rise buildings require that emergency power be provided to operate fire/life safety systems, and for emergency lighting for safe evacuation of the building during power outages and emergencies. As part of this remodeling, an emergency generator was needed to provide code compliance in a very tight funding environment.

The need for an emergency generator, lack of remaining funds for this project, and increasing cost of electricity led to the idea of using the building generator to produce electricity and shave off demand to reduce the peak-load penalty charge by the local utility on a daily basis, with the generator still being available for emergencies.

Joseph Jacobsen, the Operations Manager, and Andy Hilgendorf, the Electrical Services Manager, teamed up to analyze building loads and to evaluate various generator technologies available. The staff proposed a 60 kW Capstone Microturbine run on natural gas.

The maximum connected load to the building is 400 KVA, or approximately 320 kW. Emergency load requirements for such systems as emergency lighting, fire pumps and alarms, UPS for phone systems, and backup power for boiler circulating pump and controls were calculated to require 25 kW. The engineering staff had been evaluating the newer generation of microturbines that are now available in 30 kW or 60 kW sizes, and multiple turbines can be installed for one site application.

The microturbine installation at the City of Milwaukee's Anderson Municipal Building. Pictured are (from left) the heat exchanger, the 60 kW microturbine, and the natural gas compressor.

Jacobsen and Hilgendorf evaluated the use of microturbines and reciprocating engines and found that if the heat generated by the microturbine can be captured effectively, with the turbine's 79 percent efficiency rating coupled with cost savings realized during on-peak hours to shave off peak demand, the microturbine could potentially save $3,000 per year. After they reviewed various options, it was clear that the best alternative was a natural gas fired 60 kW microturbine produced by Capstone Company. The Capstone Microturbine met two basic but important requirements: (1) Record of reliability and minimum maintenance, and (2) a company with a proven record and established history of technical support.

City staff made several presentations to the local utility (WE Energies) and a state-operated energy conservation group (Focus on Energy) to introduce the concept of combined heat and load shedding with the use of building emergency backup generator. The City of Milwaukee has a state-of-the-art digital energy/utility management system infrastructure in place. The current system uses real-time, web-based readings on an assortment of strategic points using an existing SCADA system. The City offered the installation as a "demonstration" project for the utility, the energy conservation group, and the local educational community.

This demonstration project can be viewed live on the following websites:

In late 2002, two-thirds of the project was funded by the utility and the state energy conservation group. Today the system is successfully operating and saving the City money.

The success of this demonstration project has paved the way to utilize building emergency generators to provide double duty: to act as building emergency power when needed and to reduce building operating costs by shaving peak-load charges and heat recovery from the generator. Joe Jacobsen and Andy Hilgendorf can be reached at the Department of Public Works by calling (414) 286-8222.

Venu J. Gupta can be reached at (414) 286-3401 or at vgupta@mpw.net.