Wind energy is a major source of renewable power, but the electricity it generates must travel from the often remote, windy locations where it is captured to the population centers where it is consumed. The fundamental challenge of wind energy transport involves safely and efficiently moving this power over long distances. This journey requires a series of carefully engineered steps to convert the power from the turbine’s internal voltage to the ultra-high voltages needed for bulk transmission and, finally, to the low voltages usable in homes and businesses.
Preparing Wind Energy for the Grid
Wind turbines convert the kinetic energy of the wind into electrical energy, typically generating low-voltage alternating current (AC), often around 690 volts (V) to 3 kilovolts (kV). This low voltage is not suitable for even short-distance travel because it would result in significant energy loss due to electrical resistance. To prepare the power for movement, a transformer is installed either at the base of the turbine or inside the nacelle to immediately “step up” the voltage.
This initial step-up raises the voltage to a medium-voltage level, usually between 10 kV and 35 kV, creating the internal electrical network for the entire wind farm. Power from all individual turbines is collected through a network of cables, often buried underground, which converge at a central substation on the site. This collector substation acts as the gateway to the main transmission system and performs the second, much larger voltage increase necessary for long-haul transport.
The High-Voltage Transmission Network
To move vast amounts of power from the wind farm collector substation over hundreds of miles, the voltage must be increased to extremely high levels, often 100 kV up to 500 kV or more. By increasing the voltage, the current required to transmit the same amount of power is decreased, which minimizes energy lost as heat. This efficiency makes remote wind generation economically viable.
The collector substation uses large power transformers to boost the medium-voltage power up to the high-voltage transmission level. This power is then injected into the main electrical grid, composed of large transmission towers and high-voltage alternating current (HVAC) lines. These lines form the backbone of the grid, spanning regions and countries to deliver bulk electricity. The AC system is the standard for most domestic transmission networks, allowing for simple voltage adjustments using transformers throughout the grid.
Transporting Power from Remote Wind Farms
Connecting wind farms in remote or offshore locations requires specialized transmission technologies. Offshore wind farms use submarine cables to transport electricity to an onshore substation. For shorter distances, typically less than 50 kilometers, standard High-Voltage Alternating Current (HVAC) cables are used.
For very long distances, such as linking remote onshore farms or large offshore wind farms to distant urban centers, High-Voltage Direct Current (HVDC) transmission is preferred. HVDC systems are much more efficient over long distances (often beyond 50 to 100 kilometers for cables) because they avoid the reactive power losses inherent to HVAC over great lengths. While HVDC requires expensive converter stations to change AC to DC and back again, the reduced line losses make it the economical choice for bulk power transfer.
Final Delivery to Consumers
Once the high-voltage power reaches population centers, it must be prepared for safe consumption. This final stage involves a methodical “step-down” process through a series of substations. Regional substations receive the ultra-high voltage power and reduce it to a level suitable for regional sub-transmission, often in the range of 35 kV to 138 kV.
The power then moves to local distribution substations, which perform the final major voltage reduction, typically bringing it down to a medium-voltage range (such as 2 kV to 33 kV). This medium-voltage power travels along the distribution network, consisting of lines supported by utility poles or buried underground. Distribution transformers, often mounted on poles or pads near homes and businesses, step the voltage down one last time to the low, usable household level (such as 120 V or 240 V) for delivery to the consumer.