Scientists develop eco-friendly lubricant additives to protect water turbines and waterways

Testing with ORNL tribology equipment found that new ionic liquid-based lubricant additives developed for water turbines significantly reduced friction and equipment wear. Credit: Genevieve Martin/ORNL.

Scientists at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed groundbreaking lubricant additives that not only protect water turbine equipment but are also friendly to the environment.

This new development is a significant step towards more sustainable industrial practices, especially given that roughly 2.47 billion gallons of lubricating oil are used annually in the U.S., with about half of it eventually leaking into the environment.

The new additives are made from ionic liquids (ILs), which are organic liquid salts that mix well with oils.

These ILs help reduce friction between machine parts like bearings and gears, and they perform well across a variety of temperatures.

What makes these ILs especially appealing is their environmental safety—they are non-toxic, biodegradable, and show minimal impact if accidentally released into waterways.

Researchers focused on developing ILs that are both high-performing and environmentally safe.

These efforts led to the creation of ammonium phosphate and phosphonium phosphate ILs, which when added to lubricants, resulted in a 50% reduction in friction and a tenfold decrease in wear and tear on equipment.

This performance surpasses that of conventional gear oils currently available.

These innovations come after more than two decades of IL research at ORNL, including efforts to improve lubricants for vehicle engines which significantly enhanced fuel economy and reduced wear.

“Our previous work showed us that you could dramatically increase the performance of lubricants with the addition of just 1% or even a half-percent of ILs,” said Jun Qu, who leads the Surface Engineering and Tribology group at ORNL.

The project aimed to create a non-toxic additive for turbines that generate electricity using water currents. Unlike other lubricant ingredients, ILs are less toxic and designed to have a negligible environmental footprint.

“They have to perform well, not be toxic to aquatic organisms, and degrade rapidly if spilled,” explained Teresa Mathews, leader of the Biodiversity and Ecosystem Health group at ORNL.

The team also ensured that the ILs were free from potentially harmful elements like fluorine, chlorine, and metals such as zinc and iron.

They discovered that a four-carbon chain length in the ILs was the optimal size for maintaining oil solubility and thermal stability.

The effectiveness of these lubricants was tested using metal pieces simulating turbine gears and bearings, with the results showing significant reductions in surface wear.

These findings were further supported by electron microscopy at ORNL’s Center for Nanophase Materials Sciences.

Ecotoxicologist Louise Stevenson conducted toxicity and biodegradability tests using water fleas, a sensitive indicator of aquatic health, to assess the environmental impact.

The tests followed strict Environmental Protection Agency protocols, revealing that while conventional additives were extremely toxic, the newly designed IL additives allowed for 90-100% survival rates among the water fleas.

These biodegradable lubricants not only promise reduced environmental harm but also enhance the durability of equipment, particularly marine turbines which face harsher operating conditions and less frequent maintenance schedules compared to their wind turbine counterparts.

The successful collaboration between materials scientists and environmental scientists at ORNL underscores the potential of green chemistry to address pressing economic, environmental, and societal challenges.

The project now looks to adapt these lubricant additives specifically for tidal turbines in oceans, which face unique challenges like seawater contamination and varying pressures and temperatures.