polymer sheet that has the same performance as the heavy glass mirrors, but at a much lower cost and weight. It also is much easier to move and install. The glossy film uses several layers of polymers, with an inner layer of pure silver. As this renewable source of energy is inconsistent by nature, methods for energy storage have been studied, for instance, the single-tank (thermocline) storage technology for large-scale solar thermal power plants. The thermocline tank approach uses a mixture of silica sand and quartzite rock to displace a significant portion of the volume in the tank. Then it is filled with the heat transfer fluid, typically a molten nitrate salt. Enclosed trough The enclosed trough architecture encapsulates the solar thermal system within a greenhouse-like glasshouse. The glasshouse creates a protected environment to withstand the elements that can reduce the reliability and efficiency of the solar thermal system. Lightweight curved solar-reflecting mirrors are suspended within the glasshouse. A single-axis tracking system positions the mirrors to track the sun and focus its light onto a network of stationary steel pipes, also suspended from the glasshouse structure. Steam is generated directly using oil field-quality water, as water flows along the length of the pipes, without heat exchangers or intermediate working fluids. The steam produced is then fed directly to the field's existing steam distribution network, where the steam is continuously injected deep into the oil reservoir. Sheltering the mirrors from the wind allows them to achieve higher temperatures and prevents dust from building up as a result from exposure to humidity. GlassPoint Solar, the company that created the Enclosed Trough design, states its technology can produce heat for EOR for about $5 per million British thermal units in sunny regions, compared to between $10 and $12 for other conventional solar thermal technologies. Enclosed troughs are currently being used at the Miraah solar facility in Oman. In November 2017, GlassPoint announced a partnership with Aera Energy that would bring parabolic troughs to the South Belridge Oil Field, near Bakersfield, California. Early commercial adoption In 1897, Frank Shuman, a U.S. inventor, engineer and solar energy pioneer built a small demonstration solar engine that worked by reflecting solar energy onto square boxes filled with ether, which has a lower boiling point than water, and were fitted internally with black pipes which in turn powered a steam engine. In 1908 Shuman formed the Sun Power