A Look Inside the Berkeley Cogeneration Facility

I recently (Cal Day '01) had an opportunity to tour the cogeneration facility on campus at UC Berkeley. This page is a result of that tour. Any of the information here could very well be wrong, as I've written it all from my memory of what the plant staff told me. I'd appreciate any comments, corrections, or additions.

Unfortunately the inside of the plant is not very conducive to meaningful photographs—it's tightly packet with a three dimensional network of pipes, ducts, and equipment. It would be really nice to have an overall schematic to outline the operation of the plant, but for now you'll have to use your imagination.

The MIT cogeneration plant has a comprehensive website describing its operation.

Overview

Simply put, the Cogeneration Facility on campus at UC Berkeley supplies the campus with steam (for heating and a variety of other uses) and electricity. By generating steam and electricity simultaneously the plant is able to boast an overall energy conversion efficiency of 76%.

The actual ownership and accounting are a little bit more complicated: the Cogeneration Facility itself (eg, the building) is owned by the University of California; however, the newer equipment including the gas turbine and heat recovery system is owned by Delta Power. The plant is operated by General Electric and sells steam directly to the UC Berkeley campus. The electricity produced by the cogeneration facility is sold to Pacific Gas & Electric, but realistically it powers campus directly; however, campus buys its electricity from Enron through a University-wide longterm contract.

The primary means of energy conversion in the plant is a LM2500 Gas Turbine with duct-burners; however I think that there are also traditional boilers still in use, but I don't have any information on them. The plant also has a traditional diesel generator that may be used in the case of a complete power loss to provide sufficient power to start the operation of the cogeneration facility.

The cogeneration plant sells steam to the UC Berkeley Physical Plant. The staff at the cogeneration plant knows little about how the steam is actually used on campus; their only job is to make it, and bill campus for the energy use (by keeping track of its enthalpy). The steam is distribued through campus in a network of underground pipes, some in the steam tunnel but most simply buried. The main campus steam tunnel leads from the cogeneration facility, through the bridge where Cross Campus Road crosses Strawberry Creek, follows cross campus road until it turns right to go under/through Wheeler Hall, crosses Strawberry Creek a second time, and then enters the University Substation adjacent to the Old Art Studio. Apparently the Old Art Studio (a brick building just East of Sather Gate) was the original campus boiler plant before such operations were moved to the current cogeneration facility.

The LM2500 Gas Turbine Engine

A General Electric LM2500 Gas Turbine is at the heart of the cogeneration facility; it is used to generate both electricity and steam. This turbine is the same model engine as powers the DC-10 aircraft! The LM2500 at Berkeley usually burns natural gas, but it is able to burn many other fuels as well, such as diesel. The shaft of the turbine drives an electric generator, and the hot exhaust gasses are fed into a "heat recovery unit" for the production of steam. Before entering the heat recovery unit, duct burners raise the gas temperature from about 700°F to nearly 1200°F. After leaving the heat recovery unit, the exhaust gasses have cooled to about 300°oF and are vented to the roof. The gas turbine produces about 21,000 horsepower(?), and when it is fueled by diesel oil, consumes 28 gallons per minute; under normal operation the cogeneration facility is fed natural gas via a 5½" natural gas pipeline; it is the capacity of this pipeline that limits the energy production of the facility.

Under the street outside the facility, there are diesel fuel storage tanks to provide a backup fuel supply for the plant. Currently it would be less expensive to burn diesel fuel rather than natural gas; however, campus prefers natural gas because the exhaust products are odorless. Burning diesel fuel as the primary fuel at the cogeneration facility has been compared to driving fifty semi trucks around campus continually.

The cogeneration facility currently pays approximately $3,000,000 per month for natural gas.

Control Room

Many of the operations of the cogeneration facility are directed from a centralized, computerized control room situated on the south side of the building, near the LM2500. The facility is staffed twenty-four hours a day with a minimum crew of two at all times, who generally work twelve hour shifts. Available below are shots of a few of the information screens available from the control software. These screen shots detail (a) the LM2500 operation, (b) electrical energy distribution to campus and PG&E, (c) the heat recovery system, (d) some statistics, and (e) controls and emissions/pollution monitoring for one of the boilers.

Click an image for a much larger (1024x768) version.

Afterword

That's all I have right now... I'd love to add more, so if you have anything to add, please email me.

Copyright © 2001 by Tobin Fricke