Salt-Ice Combination Unlocks Novel, Waste-Free Electricity Generation Method

Scientists have discovered that a simple combination of salt, ice, and mechanical strain can generate waste-free electricity, opening new avenues for renewable energy harvesting from frozen environments. Researchers report on September 15 in Nature Materials that cone-shaped pieces of saline ice (approximately 25 percent salt by weight) just smaller than a black peppercorn can produce about 1 millivolt of electrical potential. Arrays containing 2,000 such cones could yield around 2 volts, enough to power a small red LED light.

This electricity generation is explained by the flexoelectric effect — a phenomenon where a solid material produces an electrical charge when subjected to non-uniform mechanical deformation. While pure ice exhibits weak flexoelectricity that may relate to atmospheric electricity such as lightning generation, the presence of salt as a common impurity turns ice into a much more effective generator of electric current.

Physicist Xin Wen and colleagues advanced this research by freezing saltwater into cone and beam shapes, then using specialized equipment to bend these saline ice forms and measure the produced electrical charge. The cone shapes withstood higher forces and generated higher voltages, and smaller cones responded with greater strain-induced electrical output. Such arrays of small cones hold promise for amplifying power output from saline ice structures.

The underlying mechanism involves nanoscale layers of liquid brine trapped between ice grains. When bent, ice develops pressure gradients pushing this charged brine from compressed to stretched regions. Since the brine contains positively charged ions (cations), their movement creates a streaming electric current. This streaming flexoelectricity effect is significantly enhanced by salt's influence on ice microstructure—reducing ice grain size, increasing brine channel thickness, and altering water molecule behavior to boost dielectric properties and ionic transport.

While the generated electrical output remains modest, this discovery suggests saline ice could serve as a renewable power source in cold environments, potentially powering sensors or low-energy devices. However, scaling this technology to power everyday electronics is challenging; for example, charging a smartphone might require a salty ice block tens to hundreds of square meters in size. Ongoing research aims to improve efficiency and reduce the environmental footprint of such ice-based energy harvesters.

Overall, this new understanding of flexoelectricity in naturally salty ice not only advances potential sustainable energy solutions but also sheds light on geophysical phenomena and may inform studies of icy worlds in our solar system, such as Europa or Enceladus, where saline ice covers vast surfaces.