Renewable Energy at Deer Island
Massachusetts Water Resources Authority

The MWRA’s Deer Island Wastewater Treatment Plant treats an average of 360 million gallons of wastewater each day from 43 communities in greater Boston and is one of the largest electricity users in the Northeast.

Deer Island currently self-generates 20% of its electricity needs and more than half of the Island’s energy demand is provided by on-site, renewable generation.

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In addition to solar power, MWRA has a number of on-going and new renewable energy programs to ensure that the facility reaches the goal of 30% by 2020 established by Governor Patrick’s Executive Order 484:

Wind turbines at Deer Island (larger image)

• A design/build contract was awarded in October 2008 for the installation of two 190-foot, wind turbines (600 kW each) at Deer Island. The wind turbines will generate over 2 million kW hours per year for an annual estimated savings of $230,000. The turbines have been installed and are scheduled to be operational by the end of 2009.

• A 100-kW roof-mounted solar photovoltaic system was installed on the Residual/Odor Control Building at Deer Island in early 2008.  All power generated is being utilized on-site. The $870,000 solar photovoltaic project was funded by a $310,000 CREB loan and a grant of $560,000 from the Division of Energy Resources. The solar installation will be qualified as a Massachusetts Renewable Portfolio Standards Program (RPS) renewable generation unit and MWRA can sell the Renewable Energy Certificates for solar as it currently does for digester gas.
  
  
  
• Since 2002, energy is recovered by the flow of treated wastewater as it drops from the plant into the outfall tunnel shaft through two one-megawatt hydroelectric generators that produce over 5 million kW hours of electricity, avoiding approximately $500,000 in energy costs annually.
  
  
• The methane generated from the sludge digestion process (“digester gas”) is collected and used in Deer Island’s on-site power plant to create steam that supplies hot water and heat for the facility. The steam is also run through a steam turbine generator that produces electricity. This co-generation facility saves MWRA approximately $15 million in annual fuel oil costs.
  
  
• Digester gas-derived electricity generated by the steam turbine qualifies as a renewable (“green”) source of energy under the Massachusetts RPS Program. This program prescribes that a minimum amount of power that is supplied into the Massachusetts market be derived from renewable energy sources. Deer Island is awarded certificates for each megawatt-hour of green electricity produced. Suppliers that do not meet the minimum requirement through their own sources can purchase certificates from generators such as Deer Island through an open bid process, generating $1 million in revenues for MWRA in FY2008.
  
  
• MWRA has accelerated a project to modify the steam co-generation system and optimize use of the digester gas by installing a back pressure turbine at the Thermal/Power Plant. The modifications are expected to significantly increase renewable energy production by 5.5 million kW hours per year with a net savings of approximately $500,000 per year.
  
  
• Deer Island is also able to self-generate electricity by running its own two 26-megawatt combustion turbine generators to reduce or eliminate its purchases from the regional power grid. Deer Island participates in the Load Response Program, administered by the not-for-profit Independent System Operators of New England (ISO-NE). In addition to the direct compensation MWRA receives from ISO-NE when Deer Island removes itself from the grid during demand events, MWRA also avoids the high market prices that typically occur during such events. Revenue from the program for FY2008 was $650,000.
  
  
• Deer Island electricity has been purchased competitively since 2001. Energy market conditions are characterized by their volatility, and MWRA has sought to balance the ability to respond to changing conditions with maintaining a measure of budgetary predictability.
  
  
• Electrical upgrades are ongoing at the two pump stations to replace the variable frequency drives that power the eighteen 1,250 horsepower motors with more energy efficient technology. Work at the South System Pump Station was completed in August 2007, resulting in an annual reduction of electricity purchases of $130,000 plus a rebate of $209,000.
  
  
• Through NStar, Deer Island recently completed the second phase of a multi-phase lighting improvement program aimed at replacing existing lamps and ballasts with high performance fluorescent reduced wattage fixtures, integrated day lighting, occupancy controls, and replacement of “Exit” signs with LED technology. 

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Updated August 24, 2009