 "CaR PaRK full" signs drive most motorists potty. Not Sam Tilley. He sees them as a business opportunity. a former oil analyst in the City of London, Tilley, 35, has started a company that puts solar panels into car parks.  The concept is straightforward.  He installs a canopy with a solar panel in the roof. The devices can be made small enough to cover a single bay, or large enough to cover a row or many rows of cars.  The power generated from the panels can be used to charge an electric car through a charging point built in to the structure. alternatively, the new panels could help to keep the lights on for whoever owns the car park.  although the panels are no different to the solar cells being strapped to the roofs of buildings across the country, Tilley thinks his device has big advantages.  Fitting a solar farm in the company car park, he says, is a clear sign of dedication to the green energy cause.  "These panels are more visible [than rooftop intallations]," said Tilley. "Companies can demonstrate their commitment to the environment in a much more visible way."  Tilley's company, Infinite Energy, has been talking to large businesses - including retailers - and local authorities to gauge their interest in installing the canopies in their car parks.  Those who do so would benefit from the government's feed-in tariff, a financial incentive to encourage the take-up of renewable energy schemes. The cost of installing the system becomes cheaper the more bays are covered. a row of up to 16 would cost up to ?6,000 per bay to cover with solar-powered canopies.  Tilley founded his company last year after more than a decade working in the City. He spent seven years at Sucden, one of the world's bigges 