Renewable Energy Systems In Cambridge
In Depth Case Studies
- Residence at 45 Antrim Street (PDF, 76KB)
- Residence at 31 Chilton Street (PDF, 82KB)
- Porter Square Shopping Center (PDF, 102KB)
These files are in PDF format and require use of the free Adobe Acrobat viewer.
Types of Renewable Energy Installations
There are many different types of renewable energy systems available that provide clean energy, avoid greenhouse gas emissions, and reduce monthly energy bills. Here are some examples:
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Solar photovoltaic (PV):
PV cells work when the energy from the sun’s rays excites electrons within the solar cells creating electricity. The electricity is produced in direct current (DC) voltages that must be converted by an inverter device to alternating current (AC) for use in electrical devices and equipment. Output from the solar panels depends on weather and time of year (i.e., sunlight is more intense during the summer and the days are longer). At night or during periods of extended cloud cover, the building may revert to conventional electricity from the utility grid. During sunny days the panels may produce enough electricity to turn an utility meter backwards, depending on electricity usage. -
Solar thermal:
Capturing solar thermal energy can be as simple as using the heat from the sun to warm a backyard pool. There are also more complex ways to transfer that heat and use it as a cost effective way to produce hot water in the home. Two types of systems can do this: active and passive. In a passive system, a large volume of water is collected in a sunny spot (such as a roof) and flows into the hot water heater for storage without the use of pumps or controls. An active system uses pumps to continuously pipe water through large panels that concentrate the sun’s rays and quickly heat it. There are two further classifications of systems. A direct system is the simplest—the water warmed by the sun is the same water used for bathing and washing clothes. An indirect system involves an additional step—the liquid warmed by the sun flows into a heat-transfer unit where it warms the cold water as it flows into the traditional hot water tank. The warming solution can also be water, but an anti-freeze solution is preferable in cold climates because it won’t freeze. -
Small wind:
A “small wind” system is a wind powered electric generation system sized for homes and businesses, generally producing less than 100 kilowatts of electricity. According to the Massachusetts Technology Collaborative, for wind power to be a viable option a site must have an average wind speed of at least 12 mph. A number of different small wind energy systems are available on the market. -
Biofuel Cogeneration:
Biofuels are liquid fuels produced from plant sources such as corn, soy, canola, algae, and cellulose. Available forms of biofuels include biodiesel and ethanol. Biofuels created from vegetable oil can be burned to power a cogeneration electricity system or directly in furnaces and boilers. Cogeneration is the use of an engine or power plant to simultaneously produce both electricity and heat. Traditional electricity generators emit heat as a byproduct of production through cooling towers, where it is lost. As an alternative, combined heat and power (CHP) engines capture this heat energy for use within buildings. Iggy’s Bread of the World, located in Alewife, has a CHP system that burns biofuel to produce electricity, then captures the heat to run its ovens, heating system, and hot water. Their 45 kW generator with heat-capturing technology is fueled by 100% biodiesel and produces 70% of the electricity that the bakery consumes in a year. Note that there is considerable controversy as to whether biofuels produced from food crops are environmentally sustainable and may lead to an increase in greenhouse gas emissions.
Cambridge Renewable Energy Facts
There are currently 28 solar PV systems in Cambridge that contribute 248.45 kilowatts of clean, renewable energy generating capacity. This is a 218% increase from last year. We also have one residential system that is generated by wind power, and Iggy’s Breads of the World that powers its bakery with biofuel cogenerated heat and electricity. Collectively, this means that Cambridge is a leader in Massachusetts for its commercial use of clean energy. As a city we save approximately 300 tons of CO2 emissions each year and $55,000 in electricity costs from our solar PV systems.
How Renewable Energy Reduces and Avoids Greenhouse Gas Emissions
Electricity for most of Cambridge is supplied by NSTAR from sources located throughout the northeast region of the United States and Canada. This electricity is generated by a variety of fuels, primarily coal, oil, natural gas, nuclear and hydropower. Regardless of the origin, the electricity comes to Cambridge over a network, or grid, of overhead and underground transmission cables.
The environmental impact of the electricity depends on the fuels used to produce it. For example, coal-powered electricity plants generate twice the carbon dioxide emissions than a plant powered by natural gas. According to the Independent System Operator of New England (ISO New England), the manager of the regional electric grid, about 0.91 pounds of carbon dioxide are emitted from the regional electric grid for each kilowatt-hour of electricity produced. In addition to greenhouse gases, the combustion of fossil fuels produces other pollution such as the chemicals that form smog and particulates.
Cambridge has two large electric generating facilities. The Kendall Square electric generating station, owned by Mirant Corp., has a 234-megawatt generating capacity. This electricity is not consumed solely in Cambridge; it is fed into the regional grid. The plant also produces steam generated by waste heat, which Dalkia distributes in East Cambridge. MIT owns the second facility, a 22-megawatt cogeneration plant that generates most of the university’s electricity. This plant reduced the emission of carbon dioxide and conventional air pollutants by 45%, compared to the situation when the co-generation plant was built in 1995.
Beginning in July 2008, customers of NSTAR will have the option to purchase clean energy produced by wind farms in upstate New York and Maine.
What Solar Photovoltaics Can Do for You
To help offset the cost of solar photovoltaic systems, the Massachusetts Technology Collaborative offers grants through the Commonwealth Solar program to residents, businesses, and organizations. In addition, there are state and federal tax incentives that may apply. Property owners interested in solar PV or solar thermal systems can find installers through the Northeast Sustainable Energy Association (NESEA) and Solar Energy Business Association of New England (SEBANE).
| System Size (kW) |
Annual Electricity Generation (kWh) |
Annual CO2 Emission Reduction (lbs) |
Annual Electric Bill Savings1 |
|---|---|---|---|
| 1 | 1,033 | 1,100 | $165 |
| 2 | 2,065 | 2,170 | $330 |
| 10 | 10,326 | 11,000 | $1,652 |
| 20 | 20,653 | 21,600 | $3,304 |
| 1. Based on 2007 average cost of electricity in Massachusetts, which was $0.16/kWh. | |||
Resources
- The Home Energy Saver: A comprehensive do-it-yourself energy audit tool developed by the Environmental Energy Technologies Division at Lawrence Berkeley National Laboratory
- Energystar: An Environmental Protection Agency and U.S. Department of Energy program, which covers a wide variety of information to help you start reducing your carbon footprint.
- Solar calculators
- Massachusetts Technology Collaborative Commonwealth Solar Program
- Solar Electricity for Massachusetts Residents: If you are interested in installing photovoltaics on your home or building and want to know if solar energy is practical for you, this guide from the Renewable Energy Trust and SEBANE provides an overview of basic steps consumers should follow in planning a photovoltaic installation.
- MTC matching grants:
- Database of State Incentives for Renewables and Efficiency (DSIRE): DSIRE is a comprehensive source of information on state, local, utility, and federal tax and other incentives that promote renewable energy and energy efficiency.
- Contractors
For More Information
For more information about climate protection activities in Cambridge please contact John Bolduc, Environmental Planner, jbolduc@cambridgema.gov, at 617/349-4628. The Community Development Department TTY line is 617/349-4621.
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