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Power Supply & Delivery Infrastructure

The Cape & Islands grid is relatively simple. Local homes, businesses, and communities are strung together by power lines. These high- and low-voltage wires, together with other utility equipment, deliver electricity to consumers.

Nantucket and Martha’s Vineyard are tethered to Cape Cod by underground and undersea transmission cables. Overhead transmission lines cross the Cape Cod Canal and link the regional grid to a network spanning all of New England and, for that matter, the rest of North America: This complex, interconnected system, which serves Mexico, the United States, and Canada, has been called the largest machine in the world.

The Canal Generating Plant feeds electricity into the Cape & Islands grid at a substation in Bourne. Other small, dispersed generating systems supply electricity to local consumers, including a growing number of renewable energy installations. When the Canal Plant is operating, output exceeding the amount demanded on Cape Cod, Martha’s Vineyard, and Nantucket is exported across the canal and injected into the New England grid. Otherwise, electricity generated elsewhere is imported to the region.

Click on the links below for more detailed information:

Supply Portfolio
National
New England
Massachusetts
Southeastern Massachusetts

Supply Portfolio
An electricity supply portfolio represents the mix of fuels used to generate power within a specified area. In the Cape & Islands region, the supply portfolio is dominated by the Canal Generating Station in Sandwich. This plant is owned and operated by Mirant, an integrated energy company headquartered in Atlanta. Mirant’s electricity supply portfolio includes more than 22,000 MW of generating capacity in North America, the Caribbean, and the Philippines. Its risk management and marketing center procures fuel for these generating assets and sells electricity in wholesale and retail markets.

The Canal plant’s total capacity is 1100 MW, far exceeding electricity demand within Cape & Islands communities. It includes two units and an undeveloped site for a third unit. Unit 1 is fueled by oil, and it is designed for continuous, full-capacity (baseload) operation. Unit 2 is designed to operate over a wide range of loads. It was retrofit in 1996 to combust oil or natural gas, but to date the cleaner and more expensive fuel has been used only sparingly. Over the past couple years, the plant itself has operated sparingly due to the high cost of oil.

Other small generating systems are located in Cape & Islands communities, but the amount they deliver to the grid is negligible when considered in light of the region’s overall demand. Many of these distributed energy solutions are sized to serve on-site needs or sited to deliver backup power in the event of an outage. Examples include the following:

Fossil-fueled generators sited on Martha’s Vineyard and Nantucket meet local needs if undersea cables go down.
Gasoline-, diesel-, and propane-fueled generators represent backup sources of power for hospitals, police and fire stations, water supply pumping facilities, private sector companies, and homeowners.
Combustion turbines and a microturbine operate as cogeneration sources, delivering cleaner electricity (and providing heating) to a retirement community in South Yarmouth, public schools in Sandwich, and other sites.
Solar photovoltaic panels supply green electricity to a growing number of homes and other buildings. Both grid-connected and off-the-grid systems exist, such as a 26.4-kW array installed atop the Woods Hole Research Center’s high-performance building and a smaller system nestled within the dunes at the Race Point Lighthouse in Provincetown.
Massachusetts Maritime Academy hosts a 660-kW wind turbine, and a growing number of small wind turbines are cropping up on the Cape and Vineyard. Land-based and offshore wind energy projects are being pursued by towns and private developers.

Generating facilities on Cape Cod, Martha’s Vineyard, and Nantucket contribute to electricity supply portfolios spanning various geographic scales. Click on the links below for more detailed information on the local implications of these portfolios:

National
New England
Massachusetts
Southeastern Massachusetts

National
According to the U.S. Energy Information Administration, coal-fired power plants accounted for 52% of total electricity generation in the United States in 2003. Nuclear plants produced 21%, natural-gas-fired plants 16%, hydroelectric facilities 7%, oil-fired plants 2%, and geothermal and “other” sources 1% each.

There are two key local implications of the U.S. supply portfolio, both relating to national reliance on coal:

Burning coal releases a variety of harmful pollutants into the air. Coal-fired plants in the midwestern United States have been identified as major sources of the sulfur dioxide (SO2) emissions that degrade air and water quality and threaten public health in New England. These plants also emit significant quantities of mercury, most of which travels long distances before it falls to the earth’s surface. Once mercury reaches ponds, lakes, and other water bodies, it can enter the food chain and become concentrated in fish. Eating contaminated fish poses health risks. The Massachusetts Department of Public Health has issued fish consumption advisories for a number of ponds and lakes in the Cape & Islands region due to elevated mercury concentrations in fish tissues.
Coal has the highest “carbon intensity” among the fuels commonly used for power production. In other words, coal-fired power plants release more carbon dioxide (CO2) per megawatt-hour of electricity than other generating sources. The Cape & Islands region is particularly vulnerable to the localized effects of climate change resulting from global emissions of CO2 and other greenhouse gases.

New England
New England’s supply portfolio is comparable to the national portfolio, as shown in the pie charts. However, nuclear plants account for a greater percentage of electricity, and the limited regional dependence on coal is offset by much greater reliance on natural gas and oil for electricity generation.

These charts illustrate broad-brush similarities and differences between the U.S. and New England electricity supply portfolios. In both charts, the “Other” category includes electricity supplied by a variety of sources; in the New England chart, this category also includes power imported from New York, New Brunswick, and Quebec that may have been generated by fossil, nuclear, hydroelectric, or other sources. (Data sources: U.S. Energy Information Administration, ISO New England)

A more detailed table of 2003 contributions by individual fuel sources is provided in the table, Sources of Electricity in New England in 2003. The most important trend in the six-state region’s supply portfolio is displayed in the bar chart below. Reliance on natural gas is steadily increasing. This has significant economic consequences for all local electricity consumers and for residents, businesses, and other organizations that rely on natural gas for heating, cooking, manufacturing, and other uses. Higher electricity and fuel prices are a major concern, on their own and because they have ripple effects: Consumers end up paying more for other products and services.

New England’s growing dependence on natural gas for electricity generation poses risks to Cape & Islands residents and businesses, including higher electricity and fuel prices, increased price volatility, and fuel shortages and service outages. (Data source: ISO New England)

Periodic fuel shortages leading to price spikes, rolling blackouts, and gas service cutoffs represent another key concern—and not just a theoretical one. During a January 2004 cold snap, some power plants in New England stopped operating because no gas was available, while others shut down because plant owners could reap higher profits by selling (rather than burning) their fuel. The shortfall in generating capacity led ISO New England to issue a warning about possible rolling blackouts. The fuel shortage caused some Cape Cod residents and businesses to lose gas service.

Massachusetts
Because Massachusetts is part of the larger New England marketplace, its electricity supply portfolio is not of specific concern to Cape & Islands consumers. However, the Commonwealth’s Renewable Portfolio Standard (RPS) has important local implications.

In April 2002, the Massachusetts Division of Energy Resources promulgated the RPS (225 CMR 14.00) under authority granted by the Electric Utility Restructuring Act of 1997. Since 2003, retail suppliers operating within the state—including distribution companies such as NStar and National Grid as well as municipal aggregators such as Cape Light Compact—have been required to purchase a certain amount of “generation attributes” from renewable energy facilities that meet criteria established by the RPS.

Generation attributes are environmental and other non-monetary characteristics associated with electricity production. In the New England marketplace, these attributes are tracked by the New England Power Pool’s Generation Information System (NEPOOL-GIS). For each megawatt-hour of electricity, NEPOOL-GIS creates an electronic certificate that describes when and where the power was produced; the fuel source used; the facility’s RPS eligibility; the amount and type of certain pollutant emissions; and other characteristics. Electricity suppliers may sell their certificates to retail suppliers or other market participants, separate and apart from the actual electricity they generate. RPS-qualified facilities thus generate green electrons as well as renewable energy certificates (RECs).

In 2007, retail suppliers are required to secure RECs equivalent to at least 3% of their annual sales within the state. This percentage increases by 0.5% annually through 2009, when it reaches 4%; thereafter, it is scheduled to increase by 1% annually. These RPS requirements, similar standards in other states, and additional provisions of the state’s Electric Utility Restructuring Act are beginning to expand the role of renewables in the electricity supply portfolio of Massachusetts and the entire New England marketplace.

RPS requirements have two important local implications:

At present, the supply of green energy is low and its costs are relatively high. Distribution companies such as NStar and National Grid pass the costs of RPS compliance along to electricity consumers.
RPS requirements provide incentives for renewable energy development, as evidenced by municipal and private sector proposals to harness wind energy resources in and around local communities.

Southeastern Massachusetts
Until recently, electricity was priced uniformly throughout New England. In 2003, ISO NE instituted a new system, known as locational marginal pricing (LMP), to more efficiently price wholesale power costs. Eight different LMP zones exist, three in Massachusetts and one each in Connecticut, Maine, New Hampshire, Rhode Island, and Vermont. Cape Cod, Martha’s Vineyard, and Nantucket fall within the Southeastern Massachusetts (SEMA) LMP zone. Because generating capacity within SEMA far exceeds demand, electricity is generally exported to neighboring LMP zones.

The area’s supply portfolio, though more heavily weighted toward fossil fuels than that in the rest of New England, does include a mix of fuels. For example, SEMA facilities ranging in capacity from 75 to 200 MW rely on coal, fuel oil, natural gas, and jet fuel. The three major power plants in SEMA include the following:

The 1599-MW Brayton Point Station is located in Somerset on Mt. Hope Bay at the head of Narragansett Bay. It is the largest fossil-fuel-fired power plant within New England. It generates electricity largely by burning coal, but one of its four units can operate on fuel oil or natural gas.
The 670-MW Pilgrim Nuclear Station is located in Plymouth on Massachusetts Bay. It is the sixth-largest power plant—and the only nuclear plant—in Massachusetts.
The 1100-MW Canal Generating Station is located in Sandwich at the northern end of the Cape Cod Canal. It is the second-largest power plant in Massachusetts. It generates electricity largely by burning oil, but one of its two units can operate on natural gas.

The proximity of these large facilities to the Cape & Islands region has important implications for local environments and populations.

Every day, smokestacks at the Brayton Point Station introduce hundreds of thousands of pounds of pollution into the atmosphere just upwind of the Cape & Islands region. These emissions degrade air and water quality, threaten public health, and contribute to climate change.
(Photo Source: U.S. EPA Region 1)

The Brayton Point plant is the single largest source of air pollution in New England. Data from the U.S. Environmental Protection Agency (EPA) indicate that the facility emitted more than 70 million pounds of SO2 and more than 21 million pounds of nitrogen oxides (NOx) in 2003. According to the U.S. EPA’s Toxics Release Inventory, the plant’s four smokestacks released 180 pounds of mercury and more than 1 million pounds of other toxic substances in 2001. Prevailing winds carry these airborne contaminants toward local communities.

The Pilgrim plant generates electricity without producing SO2, NOx, or mercury. It is the exceptional event, rather than routine operation, that poses risks to the Cape & Islands region: A release of radioactive material from the plant, though unlikely, is possible. The U.S. Nuclear Regulatory Commission (NRC) defines two zones around each nuclear power plant. In the “emergency management zone” (EMZ), which covers an area about 10 miles in radius, the primary concern is direct exposure to and inhalation of airborne radioactive contaminants. In the “ingestion zone” (IZ), about 50 miles in radius, the primary concern is ingestion of contaminated food and water. (See Fact Sheet on Emergency Planning and Preparedness at Nuclear Power Plants from NRC.)

Portions of the town of Bourne fall within the Pilgrim plant’s EMZ, and many more local communities lie within its IZ. If an accident or attack results in a radioactive release, emergency plans would go into effect. The Sagamore Bridge would be closed to control access to the EMZ, and responses by Bourne and other towns would include alarms, sheltering, and evacuation, as appropriate. In addition, these towns, along with others within the IZ, would be required to alert residents, test locally grown foods and local water supplies, stop the distribution of contaminated food and water, relocate livestock, and control access, as appropriate.

Communities with potassium iodide (KI) stockpiles would distribute these pills to reduce the risk of thyroid cancer in individuals exposed to radiation. This compound helps prevent the thyroid gland from absorbing radioactive iodine, one of several isotopes that could be present in a radioactive release. A Massachusetts law passed in 2002 requires the state to provide KI to communities in the Cape & Islands region that elect to stockpile thyroid-blocking agents.

For the Canal plant, some economic, environmental, and social effects on local communities are itemized here.

Last updated 09.19.07.