Fuel Diversity

Providing reliable electricity means giving generators the right spin.

Spin a turbine that’s hooked to a generator and you get electrical power. How do you spin a turbine? For most electric utilities there are three good ways: boil water and use the expanding steam to spin the turbine, pass lots of water through a turbine to make it spin, or burn fuel and let the rapidly expanding gases spin the turbine.

Is one way better than another? While some methods are certainly more efficient, less costly or more environmentally friendly, the key to providing reliable electric power to hundreds of thousands of people and businesses is to have all three ways of spinning a turbine available 24 hours a day, 365 days a year.

How to boil water?

A steam turbine powered generator is one of the most reliable ways to generate electricity because so many different fuels can be used to boil the water to make steam. Steam turbines provide 80 percent of the electrical generation for PSNH. The steam to drive them comes from burning coal, gas or oil. Some steam turbine plants are "dual fuel". If natural gas prices rise, some gas driven power plants can easily switch to oil.

Water over the dam.

The turbines in hydroelectric power plants are spun by water—or more accurately, they’re powered by gravity as water flows downhill past the turbine blades. Efficient, reliable and affordable, hydroelectric plants provide, clean electric power at low cost. Unfortunately, they must be located near a river or below a dam and they are limited in the relative amount of power they can produce. For example, PSNH’s Newington Oil/Gas power plant produces 409 megawatts of power while its nine hydroelectric plants have a combined output of only 69 megawatts. Hydroelectric power comprises 5 percent of PSNH’s total electrical output.

In addition to adding to diversity, hydroelectric power plants can also "store" energy simply by holding lots of water behind the dam above the power plant. If additional power is needed rapidly on a high-use day, operators simply open the dam to create additional power.

Kick in the afterburners.

The turbine in a jet fueled power plant is remarkably similar to the jet engine in an airplane in that they use hot burning fuel to spin the turbine. But like their cousins in the air, they’re expensive to run and not very efficient. What they’re best at is providing large amounts of power almost instantaneously. This makes them ideal for use as backup when a large plant is unexpectedly shut down for repairs, or a heat wave dramatically increases electricity requirements. Due to the expense, jet-fueled power plants are never turned on unless other plants can’t keep up with demand.

Much more efficient and cost effective, are the new natural-gas powered turbines which, like jet fuel turbines, use rapidly expanding exhaust gas to spin the turbine.

A number of independently-owned gas turbine power plants have gone on line in recent years in New England, reducing the chance of energy shortages.