One of the biggest obstacles to widespread use of solar energy is the lack of a low - cost, effective way to store it when the sun is not shining. (discovermagazine.com)
Additionally, it has been hard to make use of solar energy on a vehicle because cars are curved, as opposed to a flat surface needed for proper sun exposure. (thesupercars.org)
The highly variable levels of light plants receive, particularly in densely planted crop fields, presents a challenge to the efficient use of solar energy. (newscenter.lbl.gov)