Spurred by global development and population growth, the world's energy
needs are expected to double by 2050. The best solution to meet this coming
demand is an energy mix that includes generous amounts of renewable energy sources
such as solar, wind and biofuels, as well as nuclear energy and fossil fuels.
Of the many options, the sun represents the most abundant renewable energy
source. Its rays have a potential supply that dwarfs the global demand for energy
today and for the foreseeable future. However, the costs of converting sunlight
to usable electricity, heat or fuel must be radically reduced to realize this
potential. And that can only be accomplished through the development of technologies
that are low-cost, highly scalable and based on plentiful source materials.
Dozens of researchers at the U.S.
Department of Energy's (DOE) Argonne National Laboratory are exploring new
solar technologies as part of its Alternative Energy & Efficiency Initiative.
The initiative aims to achieve revolutionary advances toward the large-scale
use of solar energy by merging basic and applied research that is supported
by collaborations with industry and other research organizations.
Argonne's solar energy research covers four specific areas: next-generation
photovoltaic technologies such as organic, hybrid and dye-sensitized solar cells;
transparent conductors deposited on 3-D photovoltaics; concentrating sunlight;
and systems analysis.
Current photovoltaic technologies perform well, but their costs are too high
to compete directly with fossil fuels. Without significant government subsidies,
incremental improvements to these technologies will not lower costs enough to
achieve grid parity, where the costs are equal to or lower than burning coal,
Next-generation technologies with potential for very low-cost production are
needed. Organic, hybrid and dye-sensitized solar cells are among the most promising
of these low-cost options. Basic science is needed to design, synthesize and
understand these materials, and applied science to optimize performance and
scale up the fabrication of devices based on these materials. Furthermore, systems
analysis will provide insight into how the complex interplay of issues such
as variability of sunshine, geographic and resource factors, regulation and
economics will impact the market penetration of these technologies.
Light must enter into one side of a solar cell, and that side also has to
serve as an electrode for the device to function—so transparent conductors
are a crucial component of virtually all solar cells. Indium tin oxide is the
workhorse of transparent conductors in today's devices. But the world's
indium supply is limited, so alternatives are needed to reduce the amount required
or eliminate it altogether. Argonne has a team of experts in a technique called
atomic layer deposition (ALD) that can prepare extremely thin layers of transparent
ALD also provides perfectly conformal coverage, even on highly three-dimensional
materials such as those required for dye-sensitized solar cells. Using ALD to
deposit indium tin oxide will enhance performance and reduce the cost of next-generation
photovoltaics. Extending this technique to alternative, earth-abundant transparent
conductors will ultimately bring us closer to fabricating efficient solar energy
devices on a massive scale.
Sunlight is bountiful but diffuse. Another route to lowering the cost of capturing
solar energy is to use inexpensive materials to collect sunlight from a large
area. This light is directed either to a small, high-performance solar cell
or to a fluid that transfers the thermal energy to steam turbines that generate
electricity. Argonne has a program developing luminescent solar concentrators
for the first approach that will function in a broad variety of climates and
another program studying advanced heat transfer fluids for the second, which
performs best in regions with abundant sunshine. Because numerous factors could
influence the commercial viability of these technologies, systems analysis will
provide essential direction regarding device targets and appropriate markets.
Argonne is also exploring in detail the environmental impact of shifting to
new solar energy technologies on a large-scale and examining how consumers will
respond to these technologies.
Photovoltaics and concentrated solar power hold the promise of ushering in
a new energy economy for the electricity grid. Looking forward even further,
turning sunlight into chemical fuels is an exciting route to replacing fossil
fuels in the transportation sector; the laboratory is laying the groundwork
to tackle this goal, too.
Argonne's integrated approach to solar energy research represents a new
way of addressing the challenges associated with shifting global energy generation
away from fossil fuels to provide a clean, secure and virtually limitless supply
of energy in the future.