By Charles River Watershed Association and Conservation Law Foundation
Since 1949, the Kendall Cogeneration Station, located near Longfellow Bridge and now owned by Veolia, had been withdrawing 77 million gallons of Charles River water to cool its three turbines. Called “once-through” cooling, the water was pumped through a piping network and used to convert the steam that had already given up most of its energy to making electricity back to liquid water. This cooling water did not contact the steam but absorbed heat that was then discharged back to the Charles River from 10–20 degrees warmer than when withdrawn. The daily volume used (77 million gallons) is often greater than the flow of the Charles in summer. Since the ambient surface temperature of the Charles can reach 85 degrees in the summer, the added heat upsets the river ecosystem, contributes to algal blooms, and has contributed to fish kills.
The Story of a Successful Partnership
In September the heated discharge will end. Instead, the plant will reject heat to an air-cooled condenser and recycle the excess heat into thermal energy to heat and cool buildings in Boston and Cambridge, including Mass General Hospital. Some of the “Green Steam” will travel from Cambridge to Boston through a newly constructed 7,000-foot pipe across the O’Brien Highway.
A double win, the “Green Steam” not only prevents adding heat to the Charles River, but also reduces the use of additional fuel for heating and cooling buildings. As an added bonus, the plant owner, Veolia, has been able to shut down its Kneeland Street steam plant from late spring into early fall, further reducing regional green house gas emissions. The project demonstrates the power of cooperation and creative thinking to protect the environment.
This unnaturally hot water entering the Charles River harmed aquatic habitat, fish, and wildlife, and is partly responsible for toxic algal blooms in the Charles River Lower Basin. Concerned for the health of the Charles River, Charles River Watershed Association (CRWA) and Conservation Law Foundation (CLF) reached out to Southern Energy to discuss alternatives that would better protect the Charles River.
Over the next decade, CRWA’s Bob Zimmerman, CLF’s Peter Shelley, and the Kendall Cogeneration Station’s representative Shawn Konary (representing first Southern Energy, then Mirant, GenOn, and NRG as the Kendall Cogeneration Station changed ownership) worked together to develop and implement a solution that would end heat from entering the Charles River. Each brought his own skills and perspective to the conversation, allowing for creative out-of-the-box thinking. To eliminate the discharge, a switch to a back pressure steam turbine had to be made, and an additional steam pipeline to Boston had to be constructed. Recognizing the significant expense and site configuration difficulties Kendall faced, CRWA and CLF worked with the plant’s owners/operators and the EPA to give Kendall the time to make the changes.
The result is a solution that not only protects the Charles River and reduces greenhouse gas emissions, but also keeps this vital power-generating asset as a viable power provider. Finding the optimal solution required a familiar research-based understanding of the complexities of the Charles and its problems, a complete understanding of engineering options on a very challenging site, and a savvy understanding of environmental regulations and their application.
As a result of these negotiations, EPA issued a new water quality permit in 2011, requiring the plant to reduce its heat discharge and water withdrawal by approximately 95 percent, and to ensure that any heated discharge does not warm the river enough to cause harm. Under the settlement, the plant will capture most of the heat generated and distribute it as steam to Boston through a new pipeline across the O’Brien Highway.
The 7,000-foot pipeline from Cambridge to Boston is now complete. The Kendall Cogeneration Station will produce usable heat and electricity simultaneously, saving fuel and preventing waste heat from entering the Charles River. Over the course of the summer, the reconfigured Kendall Cogeneration Station will transition to recycling the waste heat into efficient thermal energy. By the fall, the heated discharge will be completely eliminated from the Charles River.
Benefits to the Charles River
Eliminating the heated water entering the Charles River will:
- Protect native fish populations including river herring
- Help to restore the ecosystem and habitat in the lower Charles River
- Reduce the severity of cyanobacteria (blue-green algae) blooms, making the river safer for people and pets
Other Benefits of Combined Heat and Power
- Reduces fuel needed by more efficiently producing power and heat
- Reduce greenhouse gas emissions
- Improves air quality
- Provides a unique public utility to businesses that require high pressure steam