A solar-powered tractor could be on sale by 2010 for between €45,000 and €50,000 (£31,600-39,500), according to Open Energy, the Austrian company developing the technology.

Powered by a 26sq m solar panel, the first tractors are aimed at vegetable and fruit producers and will be able to cope with jobs like weeding and drilling. Power output is a modest 4kW (5.5hp).

Because the solar panels constantly adjust their position, says development engineer Peter Prohaska, they are 40% more efficient than fixed units and can use less direct sunlight. "There is nearly always more power being stored than is being used, so the tractor will be able to run constantly for up to a day and a half on slower-paced jobs like watering or weeding. Heavier, more demanding applications will require more battery capacity," he says.

A typical speed for the solar-powered tractor will be just 0.5kph, suitable for applications such as mechanical weeding. But higher speeds of 5-6kph will be possible for shorter periods of time.

Open Energy also reckons that the solar-powered tractor will be able to cope with short bursts of heavier jobs, even ploughing. They add that it would be an ideal vehicle to be GPS-guided.

The first prototype is due to be on-farm in Austria in 2009, with sales starting in 2010 and initial demand likely to come from the Austrian market. Interest in manufacturing has already been shown by both Asian and US companies.