A solar thermal system now being demonstrated in the UK uses plastic Fresnel lenses instead of conventional glass mirrors to focus the sun's radiation.

Bourne-based Lark Energy has received a UK patent for its Solar Steam technology, which the company says offers greater design flexibility and is less expensive to manufacture compared with conventional concentrated solar thermal technologies.

Simone Perini, Lark Energy renewable development engineer, stands next to a prototype of the Solar Steam system. Image credit: Solar Steam.Solar Steam works by focusing the sun's rays through a Fresnel lens array onto a tube that contains water. The water is heated to create steam, which can be used in industrial heating and cooling applications.

(Read “The Fresnel Lens: A 19^th Century Innovation with 21^st Century Applications.”)

The angle of the lens array can be adjusted through a vertical axis to track the sun. The array is seated on a circular track that allows it to follow the sun's progress horizontally across the sky. By tracking in both planes, the system maintains high levels of solar radiation concentrated on the tubes.

Lark Energy says the potential for renewable power generation using a solar steam array is greatest in sunny regions such as southern Europe and Asia. It estimates a potential capacity of between 700 GW and 2,100 GW of capacity in India alone for solar steam systems.

The company says the solar steam array may have particular use as a renewable method of powering the multistage flash method of desalination, which uses heat to convert salt water into potable water. The technology has particular potential in coastal countries with water shortages, such as India.