A new study reported in the journal Applied Physics Letters in August this year (published by the American Institute of Physics), explains how solar energy could potentially be collected by using oxide materials that have the element selenium. A team at the Lawrence Berkeley National Laboratory in Berkeley, California, embedded selenium in zinc oxide, a relatively affordable material that could make more efficient use of the sun’s power.

The team noticed that even a relatively small amount of selenium, just 9 percent of the mostly zinc-oxide base, significantly enhanced the material’s efficiency in absorbing light.

The main author of this study, Marie Mayer (a fourth-year University of California, Berkeley doctoral student) affirms that photo-electrochemical water splitting, that means using energy from the sun to cleave water into hydrogen and oxygen gases, could potentially be the most fascinating future application for her labor. Managing this reaction is key to the eventual production of zero-emission hydrogen powered motors, which hypothetically will run only on water and sunlight.

Journal Research: Marie A. Mayer et all. Applied Physics Letters, 2010 [link: http://link.aip.org/link/APPLAB/v97/i2/p022104/s1]

The conversion efficiency of a PV cell is the proportion of sunlight energy that the photovoltaic cell converts to electric power. This is very important when discussing Pv products, because improving this efficiency is vital to making Photovoltaic energy competitive with more traditional sources of energy (e.g., fossil fuels).

For comparison, the earliest Photovoltaic products converted about 1%-2% of sunlight energy into electric energy. Today’s Photo voltaic devices convert 7%-17% of light energy into electric energy. Of course, the other side of the equation is the money it costs to produce the PV devices. This has been improved over the decades as well. In fact, today’s PV systems generate electricity at a fraction of the cost of early PV systems.

In the 1990s, when silicon cells were 2 times as thick, efficiencies were much smaller than nowadays and lifetimes were reduced, it may well have cost more energy to make a cell than it could generate in a lifetime. In the meantime, the technological know-how has progressed significantly, and the energy repayment time (defined as the recovery time necessary for generating the energy spent to produce the respective technical energy systems) of a modern photovoltaic module is generally from 1 to 4 years depending on the module type and location.

Usually, thin-film technologies — despite having comparatively low conversion efficiencies — obtain significantly shorter energy repayment times than standard systems (often < 1 year). With a normal lifetime of 20 to 30 years, this means that contemporary photovoltaic cells are net energy producers, i.e. they generate significantly more energy over their lifetime than the energy expended in producing them.

The author — Rosalind Sanders writes for the solar pool cover ratings blog, her personal hobby weblog focused on tips to help home owners to save energy with solar power.