Changes to solar panel technology are accelerating demand for silver, a phenomenon that’s widening a supply deficit for the metal with little additional mine production on the horizon.

Silver, in paste form, provides a conductive layer on the front and the back of silicon solar cells. But the industry is now beginning to make more efficient versions of cells that use a lot more of the metal, which is set to boost already-increasing consumption.

Solar is still a fairly small part of overall silver demand, but it’s growing. It’s forecast to make up 14% of consumption this year, up from around 5% in 2014, according to a report from The Silver Institute, an industry association.