Why did MIT choose cogeneration for its on-campus power plant?

Cogeneration is a highly efficient process that uses one fuel to generate two types of energy, electrical and thermal. By capturing and using heat that would otherwise go to waste, cogeneration reduces the overall fuel consumed in the process. It is one of the cleaner and most cost-effective options available for energy production.

• MIT has produced its own power through cogeneration since 1995, using a natural gas turbine. 
• The upgraded cogeneration system will be designed to help MIT achieve greater campus resiliency by enabling the campus to function even when the electric grid is not available.
• Compared with the option of purchasing all of its electricity from the grid and generating steam using natural gas boilers, cogeneration enables MIT to reduce emissions, conserve energy, and operate more efficiently at a reduced cost. 
• Cogeneration is a key component of MIT’s Plan for Action on Climate Change, which outlines our commitment to reducing greenhouse gas emissions at least 32% by 2030.
• View the EPA website for details about the benefits of cogeneration in terms of efficiency, cost effectiveness, and environmental impact.

How does cogeneration work at MIT?

• Existing 21-megawatt gas turbine generates electricity
• Heat recovery steam generator captures waste heat from turbine exhaust
• Captured steam is used for heating and cooling (via chillers driven by steam turbines)
• Power from the cogeneration unit has been able to meet the majority of campus electric power needs (MIT also purchases power from utility companies)

How is cogeneration different from “conventional sources” of energy?

Large utility companies usually generate electricity at a centralized location and then transmit the electricity over miles of wires (often referred to as “the grid”). The transmission process and the waste heat loss at the centralized power plant result in high energy losses. In contrast, a CHP cogeneration system is typically located on site, and the system is designed to capture waste heat from the generation of electricity and put that heat to use (obtaining both electricity and heat through a single process). Given its on-site location and dual-purpose process, cogeneration is a more efficient way for MIT to generate electricity and heat compared with conventional generation options.

Will MIT end up using more fuel oil as a result of the plant upgrade?

No. In recent years, due to the nature of our gas service contract, MIT has had to rely on fuel oil for an average of 20-30 days/year, using natural gas on all other days. We have negotiated a new agreement with Eversource that will enable the cogeneration plant to run entirely on natural gas with the exception of emergencies and testing. By 2020, we expect to use #2 fuel oil for only 2-3 days/year for testing and as backup fuel in the case of an emergency. This will assist with MIT’s efforts to reduce emissions. 

Will MIT be storing natural gas on site?

No. The MIT plant will be receiving a steady supply of natural gas through a dedicated transmission gas line.

If MIT’s new plant uses more natural gas than the old plant, will this disrupt and/or reduce the gas supply to Cambridge? 

No. In fact, Cambridge’s gas supply will improve. MIT has partnered with Eversource to make the dedicated transmission gas line available to Eversource through a regulating station inside the new plant. This new regulating station will supplement and back up the existing station on Third Street and will improve natural gas availability to the area of Cambridge around MIT.  

I regularly see steam coming from manholes. What is causing this, and shouldn’t MIT fix these first? 

• In most cases, the manholes are emitting water vapor (not steam) created when local groundwater comes into contact with an underground steam or condensate system. MIT works to minimize this contact, but some contact is unavoidable given the proximity of the campus to the Charles River and the relatively high local water table.
• In some cases, a problem within the MIT steam distribution system (such as a steam leak) may cause steam or vapor to rise from a manhole. MIT addresses each issue as quickly as possible. If an issue occurring during cold weather is minor, the repair may be postponed until spring or summer to avoid disrupting heat delivery to campus buildings.
• In addition, a private energy company maintains a local underground steam distribution system for nearby businesses and residences, and steam or vapor rising from a manhole may be related to ongoing repairs to that company’s system.

In the case of a sea level rise, will the plant get swamped?

We have learned a great deal from the events in New York and New Jersey during and after Superstorm Sandy. As a result, the plant project will improve MIT’s ability to handle storm events; equipment is being designed and sited specifically to maintain operation during severe weather conditions. All of the key equipment in the upgraded cogen plant will be built above the anticipated 500-year flood level. As utility work progresses on campus, we will also make adjustments to the historical design standards at MIT, moving critical and easily damaged equipment to elevations that will not be prone to flood damage in the future. 

MIT has been supporting the City of Cambridge in their Climate Change Vulnerability Assessment. View current information posted by the City.

Has MIT’s cogeneration plant won any awards?

The plant received the Energy Star Combined Heat and Power Award in 2002 for environmental excellence from the U.S. Environmental Protection Agency (EPA) and the Department of Energy.