Construction Begins on Largest Renewable Energy Project in US
SunZia, the renewable energy project in New Mexico and Arizona, will cost $11 billion and add more than 2,000 jobs.
New Mexico and Arizona will soon become the site of the largest renewable energy project in the U.S. The $11 billion SunZia Wind and Transmission project by Pattern Energy will bring wind energy to about 3 million people in the Southwest.
Transmission lines in New Mexico. Image used courtesy of Bureau of Land Management
But what exactly is the SunZia project, and how will it work from a power electronics perspective?
The SunZia Transmission Project
The SunZia Transmission project involves the construction of a 550-mile, ±525 kV high-voltage direct current (HVDC) transmission line to connect New Mexico and Arizona with energy from SunZia’s wind farms. The farms are based in three counties in central New Mexico and will generate up to 3,500 MW of power. The transmission lines will be able to transport 3,000 MW of renewable energy throughout south-central Arizona.
The project combines SunZia Transmission with SunZia Wind. Image used courtesy of Pattern Energy
Ultimately, the project aims to supply customers with renewable energy during early evening hours when demand is high but supply is low. The project will create an estimated 2,000 construction jobs and 100 permanent jobs.
High Voltage Direct Current Overview
HVDC transmission technology transfers electricity long distances using direct current.
Converters are core components of an HVDC system and play a critical role at both ends of the transmission line. At the sending end, a converter station functions as a rectifier, transforming AC power from the electrical grid into DC power. This conversion is crucial as DC is more suitable for long-distance transmission, minimizing power losses typically encountered with AC transmission over great distances.
A high-level diagram of an HVDC system. Image used courtesy of National Grid
Once converted into DC, the electricity travels along the transmission line, either overhead lines or underground/undersea cables. Unlike AC systems, HVDC technology doesn't impose a technical limit on the length of these transmission lines, making it particularly effective for spans that exceed several hundred miles.
Upon reaching the receiving end, another converter station acts as an inverter, re-converting the DC power back into AC power. This AC power can then be fed into the local electrical grid for consumer use. The converters use power electronic devices, such as thyristors or IGBTs (insulated gate bipolar transistors), to manage these conversion processes efficiently. These devices allow for precise control of the power flow and voltage, ensuring stability and reliability in the power transmission.
Why Is SunZia Using HVDC Transmission?
An interesting aspect of the SunZia Transmission project is the choice of HVDC over AC for transmission. Where most power transmission on the grid is done via AC, why is SunZia choosing HVDC?
In most cases, HVDC systems are more expensive to implement than high-voltage alternating current (HVAC) systems, but this narrative changes when transmission distances get long enough. HVDC solutions become more cost-effective in the long run when implemented for distances exceeding 400 miles.
Comparison of HVDC and HVAC. Image used courtesy of Energy Information Administration
Power losses in HVDC transmission systems can be lower than in AC systems over long distances, resulting in more efficient transmission and reduced operational costs over the lifespan of the infrastructure. The lower energy loss means more generated power reaches the end user, making HVDC economically favorable for long-haul power transmission. In SunZia’s 500-mile transmission, HVDC is in the sweet spot of cost-effectiveness.
Moreover, HVDC systems can connect asynchronous power grids and link areas with different frequency AC systems or areas without synchronous AC connections. This feature is particularly beneficial for integrating sources of renewable energy sources, which often generate power in remote locations far from major consumption centers.
SunZia as Major Progress in Renewable Energy
The SunZia project represents a monumental leap in sustainable energy as the country’s largest project yet. Construction is underway, and SunZia is expected to begin commercial operation in 2026.