New Delhi, Jan. 1: India's roadside vegetable vendors may soon get a chance to turn to the sun for reduced drudgery and a bit more take-home money.

Scientists in New Delhi have designed a solar-powered vending cart that may help increase the shelf life of vegetables and alleviate the vendors' grind of sprinkling water on their vegetables on hot days.

The solar power panels atop the cart generate electricity to evaporatively cool a closed chamber just beneath the vending platform, lowering the temperatures inside by 8°C to 11°C, the scientists at the Indian Agricultural Research Institute (IARI) said.

In field tests during summer, the evaporatively cooled cart - which requires about 20 litres of water a day - was able to keep fruits and vegetables fresh for two to five days compared to conventional carts where most vegetables spoil in less than two days.

"The evaporative cooling of the chamber is similar to the way desert coolers work," David Samuel, an agriculture engineering specialist at the IARI, told The Telegraph . The solar electricity powers a battery to run a fan blowing cooled air in the lower chamber that stores vegetables.

Crop scientists estimate that about 35 per cent of India's annual fruits and vegetables harvested is lost through spoilage, primarily because of poor storage, and that much of these losses occur at roadside vending carts.

Street-side vendors typically keep their vegetables on or within wet gunny bags or repeatedly sprinkle water on the vegetables on hot days. While this has a cooling effect, it also contributes to spoilage, with green leafy vegetables, tomatoes and cucumbers among others lasting only two days.

When fruits or vegetables lose about 10 per cent of their weight through heat-driven moisture loss, they wilt, look bad and keep customers away. Vendors are forced to lower prices as vegetables approach spoilage and discard spoilt produce, losing income.

The field tests by the IARI research group suggests that the evaporatively cooled vending cart can help maintain the freshness of vegetables, assessed through colour, texture and coarse appearance, for an average of five days, even longer for some vegetables - cabbage remained usable for 10 days and cauliflower and carrots for seven days inside the cooled chamber.

"The solar power vending cart is ideal for hot and dry weather," said Pramod Sharma, an agricultural engineering researcher who led the field experiments. The IARI scientists have published the results of their field tests in the journal Current Science.

The IARI team estimates the solar-powered vending cart could be made available for about Rs 30,000, and the umbrella-like solar panel atop the cart's platform, the fan-and-cooling system, and the battery would increase the cart's weight by about 5kg to 8kg.