Bill Cook, renewable energy global account manager for Aggreko, a leading temporary power company
As the fourth largest source of power in North America, wind energy continues to be an essential part of the renewable energy story. The U.S. Department of Energy’s Wind Vision report expects wind energy to supply 10 percent of the United States power needs by 2020, 20 percent by 2030 and 35 percent by 2050.
To keep up with the ambitious growth trajectory, the size of wind turbines is also growing. So, engineers are turning to more powerful temporary generators to start the larger wind turbine, as well as to assist the entire lifecycle of the wind farm from construction to commissioning.
Larger rotors continue to be a dominant trend in wind energy, according to news reports. Rotors increased in size from 150 feet in diameter 20 years ago to 400 feet in diameter today with towers taller than 300 feet. A larger turbine diameter and taller tower allow turbines to catch faster-blowing winds at greater distances from the ground and enable the turbine to extract more power from the wind. Temporary generators can and do provide the power required to start and commission these giant wind turbines, and these generators will continue to keep pace with the market, as larger wind turbines, especially for offshore wind, are developed.
Whether it is powering the construction trailers or commissioning wind turbines, temporary power can modify as wind farms evolve. Temporary power has the flexibility to scale up or down to the specific needs of the project. For example, one wind farm developer uses two 1500kW generators during the day to power an onshore wind substation then scales down to one generator in the evening when less power is required, saving energy costs.
Not only is the temporary power scalable, but the generators are also lightweight and durable, which is vital for offshore wind farms. Recently, 30kW generators were installed on a man-access platform and charged by a wind turbine to power the electrical equipment during the offshore wind construction phase. Since these generators weigh less than a ton, they can be lifted off by a davit crane without requiring a large vessel for the installation.
Temporary power suppliers play a pivotal role in wind farm commissioning in remote areas. Off-grid generators and load banks allow commissioning turbines before connection to the power grid, avoiding commissioning delays. Recently, a 33 kV high-voltage power generation and load bank package was installed at one wind farm’s main substation so comprehensive testing could begin – not just on the turbines but also on all high-voltage gear. Because the wind farm developer could test multiple turbines at once, the commissioning process sped up. The time saved allowed wind farm owner to meet its commercial operation date and to realize the tax incentives and credits available once the wind energy system was fully operational.
Operations and maintenance
Following commissioning, low-voltage power can be supplied at the base of each turbine to power ancillary equipment, such as lighting and the hydraulic pumps to turn the rotor and prevent bearing lock-up if the turbine needs to be taken offline. Alternatively, a central high voltage package can power the integrated system from one point of connection, keeping transformers and switchgear running, in addition to the turbines if the site needs to come offline.
Maintenance typically uses temporary power from standard generators, while transformers are also made available for the higher voltages, such as 690V (the industry standard for many years). In fact, transformers have been supplied for multiple uses. To connect the circuits in the field, 480 V/34.5 transformers in the 2,500 to 5,000 kVa range are provided. To keep the system operational, power has been supplied to the field when the main transformer has failed or the utility has to take the distribution system out of service.
Power outage support
Once operating, wind farms must have contingency plans that enable fast response to power outages. Quickly restoring power with backup or emergency power system is the best way to avoid business disruptions and protect equipment. One capability that has benefitted wind farm power plants is the installation of embedded generators for turbines and substations. With unique designs and rental models available, they can significantly reduce the lifetime cost of an outage. The capabilities of such generators continue to expand as the industry trends change. Offshore projects in North America and elsewhere, require turnkey packages, complete with auxiliary vessels and refueling capabilities, which is why the multiple “layers” of expertise are needed in the wind energy business.
In conclusion, temporary power keeps wind farms generating power. These generators power the larger wind turbines coming to market, provide off-grid power to remote areas, scale up or down as the project progresses, as well as support operations and maintenance to make sure production is steady. The benefits of temporary power also apply to other renewable energy sources such as solar, as the pre-commissioning and commissioning procedures are similar to wind energy.