Frequently Asked Questions

How does Northern Wood Power at Schiller Station generate electricity?
Before Northern Wood Power was developed, PSNH's Schiller Station in Portsmouth used three 50-megawatt coal-fired steam boilers built in the 1950s. PSNH replaced one of these coal boilers with a new fluidized-bed boiler. This state-of-the-art boiler burns whole-tree wood chips and other clean, low-grade wood materials to generate electricity.

How much electricity does Northern Wood Power generate?
50 megawatts - enough to power approximately 50,000 New Hampshire homes.

Does PSNH use new-generation technology for this project?
Yes. PSNH uses a highly efficient fluidized-bed boiler. While this type of boiler is not new, it has benefited from advances in generation technology.

How does the fluidized-bed boiler work?
Unlike typical "stoker grate" boilers where wood chips are simply burned as they pass along a rolling grate, the fluidized-bed boiler circulates the wood chips and burns them while they are suspended in air within the combustion chamber. This process burns fuel more completely, limits the production of nitrogen oxides and other emissions dramatically, and captures any unburned carbon compounds for further combustion. It also converts water to superheated, high-pressure steam more efficiently, which then spins the turbines to generate electricity.

What other materials does PSNH currently use to produce electricity?
In addition to wood, PSNH owns and operates a fleet of power plants that use coal, oil, natural gas, and water (hydro) as fuels. Wood-fired generation provides more diversity to PSNH's fuel mix and helps ensure a reliable supply of affordable electric energy for PSNH customers.

Where do the wood chips come from?
Whole-tree wood chips and other low-grade woods-often referred to as "biomass materials"-are natural byproducts of responsible forestry and land management practices. Generally, whole-tree chips are produced from trees unsuitable for use in lumber or paper mills, or from the tops and branches of trees harvested for lumber. Other clean wood products, such as wood residue from sawmills, are also suitable for fuel.

Does the demand for wood chips deplete NH forests?
Not at all. New Hampshire is the second most forested state in the country (behind Maine), with more than 84 percent of its land mass covered by trees. In the past, trees unsuitable for lumber or paper production were simply left in the forest. Over time, these unhealthy trees could become dominant and obstruct the growth of healthy trees. But Northern Wood Power helps PSNH convert what would be waste to a practical, economical, and environmentally sound fuel source. As part of responsible forest management, Northern Wood Power actually helps foresters and landowners grow a more healthy and productive forest in New Hampshire.

How much did Northern Wood Power cost to develop?
The project's total cost was estimated to be $70 million, including construction of a new fluidized-bed boiler, emissions control systems, a covered wood-chip storage facility, a wood unloading and handling system, and a covered conveyor to deliver chips to the boiler. Northern Wood Power was put into service in 2006.

What is a Renewable Energy Certificate?
PSNH earns Renewable Energy Certificates, or RECs, as a result of producing energy from approved renewable energy sources and technologies. These RECs can then be sold or traded to electric suppliers and utilities lacking sufficient renewable energy resources of their own. RECs are in high demand in the emerging energy market. States such as Massachusetts and Connecticut have mandated that their electric suppliers add renewable energy-commonly known as "green power"-to their energy portfolios. As a certified green power supplier, PSNH uses proceeds from the sale of RECs to help offset the construction cost making it cost-neutral to PSNH customers.

Why was the Schiller Station site chosen for the project?
Early on, PSNH concluded that retrofitting an existing facility to wood-burning technology would be much more cost-effective than building and staffing a new power-generation facility. PSNH chose Schiller Station because of its size (three 50-megawatt boilers), its infrastructure, and the trained personnel already in place to accommodate the new technologies. In addition, it was conveniently located near major transportation routes. And by reducing the use of coal, PSNH could also dramatically improve the air emissions from the existing facility.

Are there any visible differences at the power plant now that Northern Wood Power is operational?
The stack connected to the new wood-fired system produces a noticeable increase in water vapor. This is because the wood chips are very moist-up to 50 percent water content-and the water evaporates as the wood burns. The steam, however, dissipates harmlessly into the atmosphere. Total emissions from the new stack are significantly lower compared to the coal-fired system.

How does Northern Wood Power benefit the environment?
Northern Wood Power replaces coal with wood while still generating the same amount of power. This reduces the use of more than 130,000 tons of coal annually. PSNH's new wood combustion technology is so efficient that it has reduced emissions by thousands of tons each year. Burning wood chips reduces oxides of nitrogen (NOx) by about 70 percent, mercury (Hg) by 90 percent, and sulfur dioxide (SO2) by 95 percent. Whole-tree wood chips and other biomass materials are considered "carbon neutral," meaning no additional net carbon is released into the atmosphere from burning wood.

How does Northern Wood Power benefit the economy?
As a new, significant buyer of whole-tree wood chips and other clean, low-grade wood, PSNH has become a key supporter of New Hampshire's forest industry. Northern Wood Power contributes approximately $20 million annually to the state's economy and is part of PSNH's ongoing efforts to provide New Hampshire residents and businesses with a reliable supply of affordable electric power. As our state continues to grow, projects like Northern Wood Power at Schiller Station will help reduce our dependency on fossil fuels, and help to keep customer rates stable in the future.

What impact does Northern Wood Power have on electric rates?
A primary objective of Northern Wood Power during its development was to ensure that the project's costs would be offset by the sale of Renewable Energy Certificates (RECs). These RECs are in high demand by energy providers in other states that need to comply with renewable energy mandates, like Massachusetts and Connecticut. PSNH estimates that between 300,000 and 400,000 RECs are generated each year by Northern Wood Power.