Solana Generating Station
The Solana Generating Station is a 280 MW gross capacity concentrating solar power plant located near Gila Bend in Maricopa County, Arizona, approximately 70 miles southwest of Phoenix, utilizing parabolic trough collectors to focus sunlight onto heat transfer fluid for steam generation.[1][2] It incorporates molten salt thermal energy storage, enabling dispatchable electricity production for up to six hours after sunset, marking the first such utility-scale implementation in the United States.[3][1] Completed in October 2013 at a cost exceeding $2 billion, with partial financing from a U.S. Department of Energy loan guarantee, the facility supplies power sufficient for around 70,000 homes primarily to Arizona Public Service customers.[3][4][5] Developed by Abengoa Solar, the plant spans about three square miles and features over 2,700 parabolic trough mirrors, representing a significant advancement in solar thermal technology by addressing intermittency through storage, though its parent company's subsequent financial distress, including Abengoa's 2015 bankruptcy filing, raised concerns about long-term viability.[4][6] Despite these innovations, operations have been marred by underperformance, generating less than projected energy in early years due to technical issues and weather variability.[7] The station has encountered environmental and safety controversies, including 21 air quality permit violations between 2013 and 2016—such as exceeding emission limits for nitrogen oxides and failing required monitoring—resulting in $1.5 million in fines from the Arizona Department of Environmental Quality, alongside incidents like transformer fires in 2017 and leaks of heat transfer fluid leading to soil contamination.[8][9] Now owned by Atlantica Sustainable Infrastructure, Solana continues to operate, contributing to renewable energy goals but exemplifying challenges in scaling CSP amid reliability and regulatory hurdles.[2][10]History
Development and Construction
The Solana Generating Station project originated from efforts by Abengoa Solar, a subsidiary of the Spanish engineering firm Abengoa, to deploy large-scale concentrating solar power (CSP) technology in the United States, targeting utility-scale power purchase agreements with Arizona Public Service (APS).[5] Development planning included site selection near Gila Bend, Arizona, leveraging high solar irradiance and land availability, with an environmental assessment finalized by the U.S. Department of Energy in May 2010 to evaluate impacts on local ecology and water use.[11] Financing was secured through a combination of private investment and public support, including a $1.45 billion loan guarantee from the U.S. Department of Energy issued in December 2010 under the Loan Programs Office to mitigate risks associated with the innovative molten salt thermal energy storage system.[3] The total project cost reached approximately $2 billion, reflecting the scale of installing over 2,700 parabolic trough collectors across 3.2 square miles.[1] [4] Construction broke ground in December 2010, with Abengoa serving as the engineering, procurement, and construction (EPC) contractor responsible for fabricating and installing the solar field, heat transfer fluid systems, and power block components.[12] The build phase spanned nearly three years, involving specialized labor for precision alignment of mirrors to achieve optical efficiencies above 70% and integration of the storage tanks capable of holding 1,380 million pounds of molten salt.[4] Challenges included managing extreme desert temperatures affecting material curing and ensuring minimal groundwater drawdown, addressed through dry-cooling systems to comply with Arizona water regulations.[11] The facility achieved mechanical completion and began initial electricity generation on October 7, 2013, marking the first U.S. CSP plant with six hours of dispatchable thermal storage at commercial scale.[4] [12] Post-construction testing validated the system's ability to deliver baseload-like output, with APS contracting to purchase the full 250 MW net capacity output at a fixed rate.[1]Commissioning and Initial Operations
The Solana Generating Station achieved its initial synchronization with the electrical grid on October 7, 2013, marking the production of its first megawatt-hours of electricity through the parabolic trough solar thermal system.[12][13] This milestone followed construction that commenced in December 2010 and represented the first U.S. deployment of large-scale molten salt thermal energy storage integrated with concentrating solar power, enabling six hours of dispatchable generation post-sunset.[4][3] Commercial operations commenced later that month in October 2013, with the plant ramping up to full capacity of 280 megawatts gross output, sufficient to power approximately 70,000 homes under a long-term power purchase agreement with Arizona Public Service.[3][14] Initial performance validated the system's ability to store thermal energy in molten nitrate salts during peak sunlight hours and release it to generate steam for the turbines during non-solar periods, achieving the targeted 900,000 megawatt-hours of annual clean energy production.[3] Early operations focused on grid stability testing and optimization of the heat transfer fluid circulation, with no major disruptions reported in the startup phase.[15] Developed by Abengoa Solar under a U.S. Department of Energy loan guarantee, the station's commissioning underscored advancements in dispatchable solar thermal technology, distinguishing it from photovoltaic alternatives by providing firm power independent of real-time insolation.[3] Subsequent monitoring confirmed reliable initial output, with the storage system enabling over 38% capacity factor in the first years, exceeding non-storage solar baselines due to extended operational hours.[1]Location and Infrastructure
Site Characteristics
The Solana Generating Station is located in Maricopa County, Arizona, near Gila Bend, approximately 70 miles (113 km) southwest of Phoenix, at coordinates 32.917° N, 112.967° W.[1][2] The site encompasses 1,920 acres (777 hectares) of predominantly flat desert terrain, which was previously used for agriculture, facilitating the installation of large-scale solar infrastructure with minimal topographic obstructions.[4][5][11] This arid, open landscape in the Sonoran Desert provides high solar exposure essential for concentrated solar power operations, though the site's former farmland status raised considerations under federal protections like the Farmland Protection Policy Act during development approvals.[11] Access to the facility is via State Route 238 and nearby roads, with the plant address listed as 57750 S. Painted Rock Dam Road, Gila Bend, AZ 85337.[16]Facilities and Scale
The Solana Generating Station features a large-scale parabolic trough solar field spanning approximately 3 square miles (1,920 acres or 7.8 km²), designed to capture and concentrate sunlight using an array of 808 loops comprising 3,232 solar collector assemblies (SCAs) of the EuroTrough (E2) model.[1][3][4] Each SCA measures roughly 500 feet in length, 25 feet in width, and 10 feet in height, with the total solar field aperture area exceeding 2.2 million square meters to maximize thermal energy collection via heat transfer fluid (Therminol VP-1) heated to around 735°F.[1][4] The field incorporates over 32,000 individual collector assemblies, each equipped with 28 curved mirrors that focus sunlight onto absorber tubes running parallel to the troughs.[3] The power block includes two 140 MW steam turbines operating in a Rankine cycle at 100 bar pressure, yielding a gross capacity of 280 MW and a net output of 250 MW after accounting for auxiliary loads such as pumps and cooling systems.[1][4] Wet cooling towers support the steam condensation process, integrated with the overall infrastructure to convert heated fluid into electricity.[1] Thermal energy storage is provided by a two-tank indirect molten salt system (60% sodium nitrate, 40% potassium nitrate), capable of storing up to 6 hours of full-load generation (over 1,000 MWh thermal equivalent) in 12 insulated tanks, each with a 140-foot diameter and 45-foot height, holding a total of 125,000 metric tons of salt maintained between 550°F and 730°F for dispatchable output.[3][4]| Key Facility Metrics | Value |
|---|---|
| Nameplate Capacity | 250 MW net[1] |
| Solar Field Loops | 808[1] |
| Solar Collector Assemblies | 3,232[1] |
| Aperture Area | 2,200,000 m²[1] |
| Storage Duration | 6 hours[3] |
| Storage Tanks | 12 (125,000 metric tons total salt)[4] |