Eni's prototype photovoltaic panel said to work on cloudy days ROME, Nov. 28 (UPI) -- Italian energy company Eni announced from Rome it was testing a prototype photovoltaic panel that it said is effective on cloudier days. Eni said from Rome that it was using a dedicated parking facility for electric vehicles as an outdoor lab to test a new type of photovoltaic panel. Called luminescent solar concentrators, the panels contain a specific type of fluorescent dye that's better able to make use of solar light. "By making use of the phenomenon of total internal reflection used in optical fibers, the emitted radiation is led toward the thin edges of the plate where it is concentrated on small surfaced conventional solar cells, which convert it into electrical energy," the company said. Eni said its prototype panel can capture indirect and direct solar radiation, meaning orientation doesn't matter. The panels, the company said, are just as efficient in cloudy conditions as they are in full sunlight. Each of the testing facilities can generate about 500 watts of electricity used to charge batteries on electric vehicles.