Wind Systems

Q. Wind energy systems- wind turbines: What they are and how do they work?

A. A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy. A wind turbine operates like a fan in reverse using wind to make electricity. The wind turns the blades, which spin a shaft, which is connected to a generator that makes electricity.

Q. What is the current capacity of wind energy systems in the US and worldwide?

A. As of December 31, 2009, 34,863 MW of wind power have been installed across the United States. View a larger image of the map or download a printable map (PDF 1.8 MB).

The United States Department of Energy National Renewable Energy Laboratory (NREL) has made available an Installed Wind Capacity - 1999 -2009 Animation Map

The animation shows the progress of installed wind capacity between 1999 and 2009. To view the Animated Map, visit WindPoweringAmerica.gov

As reported by The Global Wind Energy Council (1996-2009), there are 157,899 MW of cumulative installed wind capacity in over 50 countries nationwide.

Q. How is the output of wind turbines determined?

A. The energy output of a wind turbine depends on the turbine’s size and the wind’s speed at the turbine height. Wind speed is the crucial element in projecting wind energy system performance. A site’s wind speed is measured through a wind resource assessment prior to a wind system’s construction. Generally, annual average wind speeds greater than six meters per second (m/s) or 14 miles per hour (mph) are required for large-scale wind systems.

Q. How are wind areas classified?

A. Wind power is characterized by a simple system that assigns the wind potential to one of seven wind classes. The wind potential in Class 1 or 2 areas are low and not suitable for utility-scale wind energy systems. Class 3 and 4 are fair to good; and Class 5 and higher are excellent for utility-scale wind energy systems. Most of New Jersey is a Class 1 or Class 2 wind area. There are some Class 3 wind areas along the New Jersey coast and in the northwestern mountain ridges. There are Class 4, and higher wind areas off shore.

Q. What is the general capacity factor a wind energy system?

A. A wind energy system is “fueled” by the wind, which blows steadily at times and not at all at other times. During the year there are times when the wind does not blow or at speeds below which the wind turbine will turn to produce energy. Even when the wind is blowing the wind energy system does not always produce energy at its full rated capacity. The capacity factor of wind energy systems ranges from 25 percent to 45 percent. The theoretical maximum capacity factor for a rotor wind turbine is 59 percent. Off shore wind energy systems will achieve higher capacity factors.

Q. What is the average wind speed off shore?

A. Over the year the wind speed off shore in New Jersey varies between 5 to 9 m/s. The off shore wind speed in New Jersey peaks between October to April and is highest in December/January and lowest in July/August. The wind speed off shore can varies roughly 1.5 m/s over the day. In addition, during the summer months because of the thermal difference between the temperature of the water and the land a sea breeze circulation develops along the shore. The sea breeze can increase wind speeds between four m/s one half mile off shore to one m/s six miles off shore. Overall the wind is steadier and more predictable off shore.

Q. Why look off shore for wind energy systems?

A. There are a number of factors that influence the performance of a wind energy system. These includes: wind shear, turbulence, wake effect, and tunnel effect. These factors can lower the overall performance of as wind energy system and are evident to a lesser degree offshore. This coupled with higher wind speeds offshore increase the potential performance of offshore wind energy systems. With equivalent offshore and onshore wind energy systems (same MW capacity), an off shore wind energy system will produce more energy over the year.

Q. How many homes can one off shore wind turbine supply?

A. A New Jersey household uses, on average, 8,500 kilowatthours (kWh) of electricity per year. Each home on average represents a 2 to 4 kW load. A 3.6 MW wind turbine in a Class 4 or higher wind area can produce more than 10,800,000 kWh of energy in a year – enough electricity to power more than 1,200 households on an annual basis.

Q. How much does a wind system cost compared to other renewable energy or traditional energy systems?

A. Onsite wind can generate electricity for less than 5 cents per kWh in a Class 5 or higher wind area. In PJM, grid baseload power plants generate electricity for 1.5 to 3 cents per kWh. Solar electric or photovoltaic (PV) costs 21 cents per kWh and sustainably grown and harvested biomass (organic matter such as willow trees, switch grass, food waste) can generate electricity for approximately 6 to 7 cents per kWh. Offshore wind cost more than onshore wind because of additional costs which includes: additional construction cost to install the foundation; additional operating costs for a corrosive salt environment and more severe weather; and additional power collection and transmission costs. A 100 MW off shore wind energy facility, in an area with a wind speed of 8 to 8.5 m/s and a capacity factor between 32 to 35, would result in a levelized electricity cost of between 8.5 to 8.9 cents per kWh.

Q. Can wind energy systems meet all of New Jersey’s electric demand?

A. Wind is an intermittent resource and because of this intermittent nature some have looked at a limiting factor for wind of approximately 20% of the total system capacity. However, there is no firm or maximum limit. Development of future energy storage systems or advanced voltage regulation control technology with the wind energy system could significantly increase this factor. In addition, matched with other intermittent renewables like solar electric (photovoltaics), can also increase this factor.

Q. How much energy can the off shore wind resource generate?

A. Based on the Atlantic Renewable Energy Corp. Feasibility Report dated May 2004, accounting for areas that would be excluded because of conflicting concerns, an area mostly beyond 3 miles offshore in up to 100 feet of water encompassing 1,223 square miles stretching 75 mile from Seaside Hts./Park to Cape May could be conditionally viable. At densities of 20 MW per sq mile, each MW of installed capacity could produce 3,000 MWh per year while occupying less than 0.01% of the seabed in the project area.