The Netherlands has opened the world's first solar bike path, a revolutionary project to harvest the sun's energy that could eventually also be used on roads.

The so-called "SolaRoad" bike path is made of concrete modules each measuring 2.5 by 3.5 metres, embedded with solar panels covered in tempered glass.

To help prevent accidents, the glass has been given a special non-slip surface.

The solar cells currently put the electricity they generate onto the national grid, but future plans include using the energy to power street lights.

Electric bikes and cars will one day be able to refuel using contactless charging directly from the road or bike path, said Sten de Wit, a physicist who helped develop the project.

"The idea is that in the Netherlands we have approximately 140,000 kilometres (87,000 miles) of road which is much bigger than all the rooftops put together," Dr De Wit said.

"We have 25,000 kilometres of bike paths in the Netherlands."

"The real potential of this product is unlocked when we apply it not only to bicycle paths, but to other roads used by cars," De Wit added.

The path has been working for 16 days, during which it generated 140 kilowatt hours of electricity, equivalent to around 140 washing machine cycles, said SolaRoad spokeswoman Jannemieke van Dieren.

The project has so far cost €3 million, mainly for research, but SolaRoad declined to say what the cost per kilometre might be.

Dutch Economics Minister Henk Kamp cycled the first 70-metre pilot stretch of bike path on a busy provincial bicycle route north of Amsterdam.

"The Netherlands is quite ambitious when it comes to sustainable energy. This innovation is an important part of it," Mr Kamp said.

The small country of 17 million people - and around 18 million bicycles - hopes to triple sustainable energy usage by 2020 and be "energy neutral" by 2050, he added.

The SolaRoad will be tested over the next two years on a path that carries around 2,000 cyclists a day, Dr De Wit said.

The aim is to have the solar road commercially available on Dutch roads within the next five years as the number of electrically-powered cars and bicycles grows.

"We are very confident that in five years we will have a product we can apply on a large scale," Dr De Wit said.