The Little Engines That Can

Distributed power generation gains new ground
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From GreenSource
Nancy B. Solomon, AIA

Source: EEA, Inc CHP Installation Database

The custom-designed CHP system is located below grade. Together, the two generators produce up to 70 percent of the building's electrical needs. The other 30 percent still comes from the grid, which is operated by Pacific Gas & Electric (PG&E). “We have the capability to produce more, but the policies of the local utility prevent us from doing so,” says Peterson. PG&E requires the building to import 100 kilowatts from the local grid at all times and prohibits it from generating electricity during a blackout.

A jacket water system—a collection of pipes within each engine block—pumps the water that has absorbed the engines' waste heat to three apparatuses: an absorption chiller, which uses the energy from the hot water to create 300 tons of cooling capacity (backup electrical chillers are available when needed); a plate-and-frame heat exchanger, which shifts enough waste heat to the variable air volume reheat system for space heating throughout the year; and a shell-and-tube heat exchanger, which transfers enough waste heat to the domestic hot water system to supply hot water year-round as well.

Exhaust pipes from the engines are fitted with catalytic converters to ensure emissions from the combustion of natural gas meet the requirements of the Bay Area Air Quality Management District. Annually, the facilities department hires a third-party company to perform emissions tests and submit the results to the district to obtain its annual operation permit.

The CHP is controlled by a web-based interface that is monitored by both the in-house engineering department, which oversees daily operations and undertakes minor repairs, and an outside company, which provides preventive maintenance and other operational support.

This CHP system has been in operation since May 2009, and Peterson is pleased with the final results. He calculates that it has reduced annual operating costs by about $700,000 per year. Given the fact that the CHP retrofit cost about $4.6 million and the project received $600,000 in rebates from PG&E, Aegon should recoup its investment within about five years.

Third-party rating systems have also shown approval. In 2009, before the CHP was operational, the Pyramid received an Energy Star rating of 77 and a LEED Existing Buildings: Operations & Maintenance (EBOM) certification level of Gold. In 2011, once the CHP system had been up and running long enough to reapply with new data, the building's revised Energy Star rating jumped to 98, allowing the Pyramid to achieve a LEED EBOM certification of Platinum.

 

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Originally published in GreenSource
Originally published in May 2012

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