Vienna.– New trees are planned to be planted throghout the streets of Europe soon to light up the nights and save energy.

A solar tree prototype recently passed a key test phase and went on display for four weeks in October on a busy street — the Ringstrasse — in Vienna, Austria.  They were able to provide enough light during the night-time even when the sun did not show for as much as four days in a row.

According to RenewableEnergyAccess.com, the solar cells on the tree were able to store enough electricity in spite of receiving no direct solar light for days because of the clouds; they showed that solar trees really are a practical form of street lighting.

The City of Vienna was now in the process of deciding whether to install more solar trees. "We hope that not only the city of Vienna but other cities will see the merits of using renewable energy for street lighting to cut emissions," said Christina Werner from Cultural Project Management.

Putting solar powered LED light systems on trees would cut down on the carbon emissions and also slash the bills of local authorities. Street lighting consumed 10 percent of all the electricity used in Europe in 2006 or 2,000 billion KWh, and resulted in carbon emissions of 2,900 million ton.

The use of more energy-efficient lighting in the Austrian city of Graz, with a population of almost 300,000 saved the city 524,000 KWh of electricity and 67,200 euros [US $96,800] in 2005.

The branches of the solar tree were decorated with 10 solar lamps, each one comprising 36 solar cells; they also had rechargeable batteries and electronic systems. A sensor was used to measure the amount of light in the atmosphere and trigger the solar lamps to go on automatically at sunset and off at sunrise.

The tree's lights went on for the first time in Vienna on October 8, 2007 at 11:00 pm. They are now on display outside the La Scala opera house in Milan.

The tree was designed by Ross Lovegrove, a British designer, who said that they are not only efficient but also attractive and bring "nature into a gray city environment".