Related Clues:

• Take to the air
• Renewable energy type
• Type of energy
• Alternative to fossil fuels
• Alternative energy source
• Without practical significance
• Get off the ground
• -- energy
• __ year (2008 or 2012)
• From the sun
• Energy option
• Look before you do this
• One way to tackle a hurdle?
• Springing movement
• Of the sun