Currently, the only renewable energy source which contributes a meaningful portion of the nation’s and Massachusetts energy supply is hydropower. Biomass burning is considered a renewable source, but it accounts for only about 1% of power generation nationally. The most popular renewables — wind, solar and geothermal — account for well under one percent of electric power generation, nationally and in Massachusetts.
“Other Renewables” (other than hydropower) include wood, black liquor, other wood waste, municipal solid waste, landfill gas, sludge waste, tires, agriculture byproducts, other biomass, geothermal, solar thermal, photovoltaic energy and wind. The total “other renewable” wattage increased 24% from 1994 to 2005, but as a share of total energy, “other renewables” declined very slightly, as coal and natural gas increased substantially. The chart below shows the national breakdown of electrical energy sources in 2005. This data is derived from Energy Information Administration.
| Net Electric Energy Generation by Source | 000 of Megawatt Hours in 2005 | % of Total |
| Coal | 2,013,179 | 50% |
| Petroleum | 122,522 | 3% |
| Natural Gas | 757,974 | 19% |
| Other Gases | 16,317 | 0% |
| Nuclear | 781,986 | 19% |
| Hydroelectric Conventional | 269,587 | 7% |
| Other Renewables | 94,932 | 2% |
| Hydroelectric Pumped Storage | (6,558) | 0% |
| Other | 4,749 | 0% |
| Total | 4,054,688 | 100% |
Within the “other renewables category“, biomass combustion accounted for 45% of the total and geothermal for 34%; wind was 20% and solar was under 1%.
For Massachusetts, the breakdown is slightly different — more heavily natural gas. These data are also from the Energy Information Administration.
| Net Electric Energy Generation by Source | Megawatt Hours in 2005 | % of Total |
| Coal | 12,033,546 | 25% |
| Petroleum | 7,119,369 | 15% |
| Natural Gas | 20,276,566 | 43% |
| Other Gases | – | 0% |
| Nuclear | 5,475,057 | 12% |
| Hydroelectric Conventional | 1,041,950 | 2% |
| Other Renewables | 2,030,598 | 4% |
| Hydroelectric Pumped Storage | -461,643 | -1% |
| Other | – | 0% |
| Total | 47,515,443 | 100% |
In Massachusetts, “other renewables” account for 4.3% of the total for elecric power generation — up 30% from 1990 to 2005, but up only very slightly as a share of the total — from 3.9% from 4.3%. The EIA data do not appear to break down the other renewables as a share of electric power generation. However a share of total Massachusetts energy use (including non-electric uses), solar, geothermal and wind together — but not biomass — were only 2.2 out of 1,542.9 trillion BTU, 0.14% — so roughly one half of one percent if the denominator were electric power generation, since electric power generation accounts for roughly 1/3 of all energy use in Massachusetts.
As a comparison point, the Cape Wind Project is expected to add 1,489,200 megawatt hours per year (170 average production x 24 x 365), an amount equal to 3% of 2005 power consumption.
According to the Deparment of Energy, Solar Technologies Program, distributed photovoltaic power — a rooftop system — has the potential to provide roughly half of the power needed by a typical household. This may be high for Massachusetts, where available sunlight is little more than half what it is in the southwestern states. Consider that the average daily irradiation of one square meter in the Massachusetts area (reflecting latitude and cloud cover, pollution, etc.) is betwee 4 and 4.5 of kilowatt hours of energy. Available solar panels promise 12.5% efficiency on an area of approximately 1.5 square meters. 6 of these panels would produce approximately 4.5 kwh/day, roughly 1600 kwh/year — less than quarter of a typical home. That is a good sized rig — roughly 25 feet by 10 feet. But these are soft numbers; for more information on solar, see www.nrel.gov the website of the National Renewable Energy Laboratory.
