Emerging solar technologies

Emerging solar technologies

By Monique Hanis on 02/01/2008

We are witnessing an exciting time in the solar-energy sector. Research facilities, universities and companies are striving to develop new and innovative solar technologies for the commercial and residential sectors. From building-integrated and thin-film materials, to concentrating-solar and solar-thermal applications, the options for converting the sun’s rays into energy are expanding like never before. Meanwhile, improvements in the technology, manufacturing processes and installation are converging to help drive costs down.

Federal incentives, along with state and local rebate and loan programs, are now lessening the up-front costs of solar energy. In fact, a number of companies including Google, Wal-Mart, Best Buy, Macy’s and Safeway have plans for significant solar photovoltaic (PV) installations as part of their energy-efficiency programs.

Advancements in PV technology continue as researchers at the National Renewable Energy Lab, University of Delaware, Sandia National Lab and others create new combinations of layered-cell structures that split and refract sunlight for more efficient energy production. Prototype PV cells have reportedly reached 42 percent efficiency, nearly three times the 15 to 22 percent in today’s PV panels. Other innovations — like the trackers at Nellis Air Force Base that rotate 15-megawatt PV panels to follow the sun — improve performance by 30 percent.

Thin-film solar — a new technology — does not use silicon, the basic component of PV panels. Instead, a combination of copper, indium, gallium and selenide (CIGS) or cadmium telluride are effectively painted onto a thin, flexible backing to create a semiconductor material. They can be produced in large rolling sheets or incorporated into building materials, including roof shingles and tinted windows.

While thin-film materials are less efficient than the typical PV solar panel, they are 20 to 40 percent less expensive and can be incorporated on larger surface areas of a building. Companies like Miasole, First Solar, Applied Materials and Dow Chemical are all working hard to improve and deploy thin-film technology.

The big news in solar this year? Nevada Solar One, the first concentrating solar power (CSP) plant in the United States. The parabolic-trough design uses mirrors to focus the sun’s energy to heat a tube of oil, which is used to run steam-powered turbines to produce electricity. The utility-scale project in Boulder City, Nev., went online in June and produces 64 megawatts of electricity — enough to power 15,000 homes. Acciona Energy, the Spanish company that built Nevada One, announced plans for another 200-megawatt CSP plant in the next three years.

Perhaps the most interesting new solar-thermal technology is the absorption chiller: a closed-loop system that converts solar-heated water into air conditioning. Water heated by the sun through flat-panel collectors or evacuated tubes is subjected to a low-pressure loop with lithium bromide that causes the water to reach a cool 44 degrees Fahrenheit. This cooled water runs through copper piping; air forced over the coils produces air conditioning.

State and federal energy policy will also drive the deployment of small, distributed generation of solar on rooftops, as well as large-scale solar plants. While Congress missed a huge opportunity to extend federal solar incentives beyond December 2008 with the 2007 energy bill, state policies are leading the way — from California to New Hampshire. Meanwhile, industry and solar advocates across the nation are gearing up for a new fight. They want measures passed to spur solar development and to make its cost comparable to that of traditional fossil fuels by 2015 or 2016.