Wind Turbine Magazine

Wind farms can range in size considerably, and there can be some confusion over exactly how many turbines it takes for a site to become regarded as a 'wind farm'. The number of turbines on a wind farm depends primarily on the amount of available land. A small wind farm may have just a few wind turbines, while a large wind farm can have hundreds or even thousands of turbines. Typically, wind turbines are located at least five rotor diameters apart, so they don’t interfere with one another. If wind turbines are smaller, they can be grouped more closely together because they have shorter rotors, which would allow more wind turbines on a given parcel of land. However, utility-scale wind turbines can have much longer wind turbine rotors and therefore need to be spaced further apart. For example, although it varies by the manufacturer and the model, a 2.5 MW wind turbine can have a rotor diameter of 100 metres. Therefore, wind turbines would need to be located about 500 metres apart. Although it may seem counterintuitive, more wind turbines don’t necessarily mean more energy generation because electricity production depends on the capacity of each turbine. Thus, three 500 kW wind turbines have a lower nameplate capacity (at 1.5 MW combined) than one 2.5 MW turbine. So, three small turbines may actually produce less power than one big one. Why are wind turbines often grouped together? Typically, utility-scale wind turbines are sited together because it is a more economical way to generate electricity. Now, wind energy is one of the most economical sources of electricity available, and wind developers work hard to keep costs down while maximizing energy production. However, if wind turbines are too close together, the efficiency of the wind farm decreases. Typically, wind turbines are spaced out enough to prevent turbulence but close enough to reduce the required infrastructure of the project and maximize energy production. When feasible, it is usually more economical to group wind turbines together into wind farms because of the economy of scale. Although more turbines raise the total project cost, they usually disproportionately increase the income from the project. For this reason, utility-scale wind farms usually consist of as many wind turbines as possible. However, there are also other constraints on wind turbine siting. For example, there needs to be adequate interconnection capacity for the project to connect to the utility grid. Also, roads, buildings, other infrastructure, and topographic features can limit wind farm development. Although utility-scale projects typically group wind turbines together for consumption off-site, some residential and small commercial projects consist of just one or two wind turbines. Often, these projects have wind turbines of 100 kW or less and are located close to where the power will be consumed by homes, telecommunication dishes, or water pumping stations. What is the biggest onshore wind farm in the world? The Gansu Wind Farm, also called the Jiuquan Wind Power Base, is a megaproject located in north-central China on the edge of the Gobi Desert. It consists of several parts but has a planned capacity of 20 GW and 7,000 wind turbines. Gansu wind farm - the biggest onshore wind farm in the world (as of 29th March 2022) Currently, about 8 GW are constructed and connected to the grid. One challenge with this project is that it is located so far from population centres, so grid infrastructure is needed to utilize the power. What is the largest offshore wind farm globally? Hornsea 2 in the United Kingdom will be the largest offshore wind farm in the world when it is fully operational. Located next to Hornsea 1 off the Yorkshire coast in the North Sea, it will comprise an area of 462 square kilometres. Once complete in 2022, it will have a capacity of 1.3 GW and will have 165 Siemens Gamesa 8 MW offshore wind turbines. Hornsea 1 had previously been the largest offshore wind farm globally, with 1.2 GW of capacity from 174 wind turbines. Once fully operational, Hornsea 2 will power approximately 1.3 million homes in the United Kingdom. Currently, plans are underway to construct Hornsea 3 on a 696 square kilometre site. This project will consist of up to 231 offshore wind turbines and power over 2 million homes. Have wind farms increased in size in recent years? Certainly, the capacity of the largest wind farms has increased dramatically considering some of the megaprojects like the Gansu Wind Farm. In addition, the maximum power rating of utility-scale wind turbines has also increased significantly in the last decade. As a result, wind turbines have grown in size significantly. In particular, the hub height and rotor diameter have increased. As utility-scale wind turbine technology advances, the turbines are able to generate more power from a single unit. Why are wind turbines getting bigger? Taller wind turbines can reach wind resources that aren’t possible at lower hub heights, making more sites feasible locations for wind farms. This is critical as wind energy expands and is helping to replace energy production from fossil fuels. However, larger turbines also need greater spacing between units, which requires more land. Although bigger is generally better, there is a limit. It is challenging and costly to transport large wind turbines. Even if they are initially transported by cargo ship or train, all the turbine components must eventually be transported by truck to the project site. Thus, wind turbines are designed for both power generation but also ease of transport to wind farm sites. Although some components, such as the towers, can be transported in pieces and assembled onsite, wind turbine blades need to be one continuous piece. However, researchers could help overcome some of these challenges with onsite manufacturing. For example, the National Renewable Energy Laboratory (NREL) is researching the use of advanced thermoplastic resins to manufacture wind turbine blades. In addition to being more readily recyclable, they may also produce more durable and lightweight blades. Also, thermoplastic resins might cater to the onsite manufacturing of wind turbine blades. This would allow larger blades and reduce transportation costs, according to NREL.

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