As an early adopter of microgrids and distributed energy, Harvard University continues to lead the way in demonstrating energy security, reliability, sustainability and resilience for higher education.
Harvard’s history of producing and distributing power, heat and water dates back a long way. Having been a district heating customer since the early 20th century, the university purchased the Blackstone steam heating plant from the local utility in 2003 when Massachusetts restructured power industry ownership rules.
The university installed combined heat and power (CHP) in 2009, with a second addition in early 2016, according to Robert Manning, director of Harvard University Engineering & Utilities. Today, one of the CHP units serves a 7.5 MW load pocket as a microgrid, capable of both islanding and blackstart (automatic startup) service.
“Harvard’s Cambridge campus has always had its own internal electric grid, allowing greater response to campus needs, as well as ensuring high levels of maintenance and renewal on our distribution system,” Manning told Microgrid Knowledge. “Building and operating a microgrid is a complex endeavor, requiring skilled internal resources as well as key partners in all aspects of the system life cycle – design consultants, equipment vendors, controls, operations, maintenance, etc.”
Making the most out of combined heat & power
Run by Harvard Energy & Utilities, which manages the production, procurement, distribution and billing of utilities for much of the university’s Cambridge and Allston campuses, the CHP plants each serve different load pockets.
The first, a 7.5-MW combustion turbine equipped for heat recovery, effectively acts as a combined cycle generator. The new CHP unit replaced an aging boiler and was sized to meet minimum heat loads so that it runs year-round.
The second, a 5-MW back-pressure turbine, serves loads based on the output of the district energy system’s thermal steam generator. The higher the steam pressure and flow, the higher the electrical output. The unit doesn’t operate in summer months, when the steam load is very low, Manning said.
“Heat recovered during power generation is used to convert water to steam, which then flows through the back-pressure turbine eight months of the year, so we can run in a combined cycle mode,” Manning said.
Harvard uses primarily natural gas for the systems, but also maintains a backup supply of Number 2 fuel oil. All of the CHP and boilers are dual-fuel. “If necessary, we could operate for many days on our backup supply,” Manning said.
All told, the university’s energy modernization projects are yielding substantial cost savings, as well as helping improve human and environmental conditions and quality of life.
“This is behind the meter, so the value of electricity produced is far greater than just the commodity portion – we have reduced our demand charges and annual capacity costs. And there are additional financial benefits via Massachusetts alternative energy credits, which we get for electricity produced via CHP,” he said.
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12 December 2017