Outokumpu stores heated corrosive salt to maintain utility-scale solar electricity production

Outokumpu stores heated corrosive salt to maintain utility-scale solar electricity production


Perfecting utility-scale electricity production from solar power has always come up against a fundamental roadblock, according to Outokumpu: when the sun goes down, the power dies. Now, it has said designers of the Crescent Dunes Solar Energy Plant in Nevada have overcome that hurdle: “The answer is a first-of-its-kind system that relies on molten salt to store heat, allowing the plant to stay in operation day and night, rain or shine.” 

Like most plants built on the Concentrated Solar Power (CSP) model, Crescent Dunes consists of a field of tracking mirrors, or heliostats, that focus light onto a central receiver mounted on top of a concrete tower. 

But Crescent Dunes doesn’t use this concentrated heat to boil water directly to create steam to drive a turbine generator. Instead, the plant heats a mix of sodium and potassium nitrate to almost 600 degrees Celsius and pumps it to an insulated thermal storage tank. Whenever electricity is needed, the salt is sent through a steam generation system, superheating water to turn a turbine that can generate enough power for 75,000 homes.

To resist the harsh, corrosive salts contained in the plant’s hot nitrate tank, it has been constructed from 650 tonnes of specialised stainless steel – Outokumpu’s Therma 347H. This grade of austenitic stainless steel is designed specifically to ensure a long life when exposed to high temperatures.

Stainless steel is also mission critical to the plant’s 10,000-plus heliostats. These must pivot on two planes as they track the path of the sun throughout the day, keeping the energy-rich rays directed toward the receiver. 

Over 60 tonnes of Outokumpu’s Forta LDX 2101 went into the manufacture of their anchoring bolts, which have to function in an atmosphere of wildly fluctuating temperatures, sand, moisture and resists the corrosion that comes with them. This duplex stainless steel grade was selected for its ability to withstand these tough conditions, making sure the sunlight never loses focus, nor does Nevada’s drive toward clean renewable energy.

For more information visit www.outokumpu.com

8th July 2020