Wind Turbines

What is wind power ?

Wind power is the generation of electricity from wind energy as a natural resource. Wind energy is a converted form of solar energy. This is how: The sun's radiation heats different parts of the earth at various rates, with the greatest variations occurring between day and night. Since different earth surfaces such as water and land absorb and reflect heat at different rates, portions of the atmosphere vary in temperature. When hot air rises, it reduces the atmospheric pressure at the earth's surface, and cooler air is drawn in to replace it. This drawing in of cooler air is what we experience as wind.

Air has mass. When this mass is in motion, it contains the energy of that motion known as kinetic energy. A wind energy system transforms the kinetic energy of the wind into mechanical or electrical energy that can be harnessed for practical use.

Popular uses for mechanical energy include pumping water - often seen in rural or remote areas – and commonly known as the farm windmill.  In addition, mechanical energy is also used for many other purposes such as grinding grain, sawing, pushing a sailboat, etc.

Wind power consumes no fuel for its operation, and works without the emissions associated with electricity production. Wind power does not produce carbon dioxide, sulfur dioxide, mercury, particles, or any other type of air pollution that is caused by fossil fuel power sources.

Wind turbine design

There are two basic designs of wind electric turbines: Vertical-axis wind turbines (VAWT) and Horizontal-axis wind turbines (HAWT) “propeller” style machines. Horizontal-axis wind turbines are the most common today, constituting nearly all of the "utility-scale" (>100 kilowatts capacity) turbines in the global market.

Turbine subsystems include:

• A rotor or blades, which convert the wind's energy into rotational shaft energy
• A nacelle (enclosure) containing a drive train, usually including a gearbox* and a generator
• A tower to support the rotor
• Electronic equipment such as controls, electrical cables, ground support equipment, and interconnection equipment

*Some turbines, including TechnoSpin turbines, do not require a gearbox

Growing wind power capacity

Over the past ten years, global wind power capacity has continued to grow at an average cumulative rate of over 30%. 2008 was a record year with more than 27GW capacity (a 36% increase over 2007), which was dominated by three main markets: Europe, North America and Asia.

Utility scale versus small wind

Wind turbines sizes are divided into two main groups: utility-scale and small wind turbines. Generally, small wind turbines are used to provide electricity to remote locations or as hybrid solutions in combination with the existing electricity grid. Large scale wind farms usually support electric power transmission networks.

Utility-scale wind turbines are often grouped together into a single wind power plant, also known as a wind farm, and generate electrical power bulk. Electricity from these turbines is fed into the utility grid and distributed to customers, similar to conventional power plants. The utility-scale wind turbines capture the majority of the global wind market and are rapidly growing with a 53% growth in 2008 compared to 2007.

Small wind turbine sizes are up to 100kW per turbine. Small wind turbines have a wider range of configurations and applications including grid-connected and off-grid applications. Turbines can be installed as individual units for residential homes or for businesses, or as a mini wind farm where turbines are grouped together to leverage the required power.

Small wind power: cost-effective renewable energy

Small wind electric systems are one of the most cost-effective renewable energy systems. A small wind electric system helps you lower home and business electricity bills by 50%–90%. It eliminates the high costs of running extended utility power lines to remote locations and greatly reduces the need for the installation of costly infrastructure and fuel delivery logistics in low-populated areas. Small wind power is particularly attractive in developing areas for its low cost support of bringing technology to homes and businesses.

Small wind power growth

The small wind turbine industry projects a significant growth in the next few years. In the United States only, experts predict a 30-fold growth within as little as five years, despite a global recession. This means that by the end of 2013, a total capacity of 1,700 MW would be installed in the U.S. Much of this estimated growth will be spurred by the eight-year 30% federal Investment Tax Credit passed by Congress in October 2008 and recently augmented in February 2009.

Grid-Connected and Off-Grid Applications

A small wind system can be connected to an electric distribution system (grid-connected) or it can be used as a stand-alone system (off-grid).

Small wind energy systems that are connected to the electricity distribution system are called grid-connected systems. A grid-connected wind turbine reduces the power consumption from the utility company and can be used for lighting, appliances, electric heat etc. When the wind system produces more electricity than required, the excess is sold to the utility company. Whenever wind powering is insufficient, the grid system fills the gap.

 

The grid connected applications are implemented successfully in countries that have introduced an incentive plan for renewable energy. The incentive plan may include subsidies on installation, net metering option, and subsidized Feed-In Tariffs (FIT) otherwise known as renewable energy payments.

Wind power can be used in off-grid systems, also called stand-alone systems, which are not connected to an electric distribution system or grid. In these applications, small wind electric systems can be used as stand-alone or in combination with other components—including a small solar electric system—to create hybrid power systems with other renewable energy sources and/or a diesel generator. Hybrid power systems can provide reliable off-grid power for homes, farms, or even entire communities (a co-housing project, for example) that are located far from utility lines.

Wind energy versus other renewable energy technologies

Wind power is competitive with solar photovoltaics (PV) or solar energy, biomass and diesel generators, providing the best business case in relation to many other energy alternatives. The advantage of wind is derived mainly from its ease of transportation and installation – benefits that are particularly appealing in developing areas. Wind-generated electricity is the least expensive form of renewable energy power, and is quickly becoming one of the cheapest forms of electricity — from any source.