Retired mining machinery gets second life in new solar installations

Czech energy company ČEZ Group is testing the central sections of conveyor belts in strip coal mines to serve as structures for carrying photovoltaic power plants.

As mining is phased out, the central sections of the mine’s conveyors, which are used to move excavated soil from one area to another, could be given a new purpose. The steel structures with their side rail could serve as supporting structures for photovoltaic power plants.

Normally, these structures are bored into the ground; however, the common solution cannot be used in areas with unstable subsoil, such as spoil heaps, waste ponds and other unfirm areas.

Engineers from PRODECO, a ČEZ Group company, have been developing prototypes that are able to cope with moving soil.

Jan Kalina, member of the Board of Directors and head of ČEZ Group’s the Renewable and Conventional Energy Division, commented in a statement: “We place our photovoltaic plants primarily on infertile soil, in brownfields, and in areas in which industrial mining has been discontinued. Before life returns to such places, they can be useful for generating renewable energy from the sun. The soil deposited in spoil heaps is loose, it only settles gradually, and it may take decades for it to stabilise.

“We must adapt the technology used for building photovoltaic plants, and our goal is to behave in a sustainable manner and not to needlessly increase our carbon footprint.”

According to ČEZ Group, if the panels were mounted on standard structures, they would jam and crack. The team therefore had to find a solution that would be time and cost-sensitive.

A solution that offered itself was to use technologies that are already available in strip mines.

“We used the central sections of conveyor belts, which offer great advantages: they are robust, because they are designed for heavy-duty operation, and they feature side rails that are now used for transport along the plain. This makes these structures fit for any unstable subsoil or subsoil encumbered with an environmental burden, as they only stand on the surface, are extremely stable, and they offer a non-invasive method of building photovoltaic power plants,” commented Luboš Straka, chairman of the Board of Directors and CEO of PRODECO.

Once the extracted material settles, the structure tilts as a whole and the stress is therefore not transferred to the panels.

Once coal mining is phased out at Bílina Mine, thousands of these modules will be available. Several pilot structures have already been deployed on a reclaimed area near the Bílina Mine extraction area to test how photovoltaic panels cope with subsoil movement.

“The positive news is that the performance of the solar panels did not drop. For unstable subsoils, however, it will be more suitable to use technologies other than conventional silicon panels, such as thin-layer panels without silicon cells, in which the semiconductor is applied directly to the glass. The selection of the ideal technology is now the subject of further development,” adds Kalina.

ČEZ is working to build 6GW of renewable capacity by 2030. At the Ledvice Power Plant, a green energy laboratory was set up several years ago, in which ČEZ experts test the properties and suitability of various types of panels.

The first Czech floating photovoltaic power plant has been deployed in the upper reservoir of the Štěchovice pumped-storage power plant, which is unique for being placed on a water surface whose level fluctuates constantly.