What happened? MIT researchers are rethinking how light can be manipulated within solar cells. They have applied an antireflection coating, a novel combination of multi-layered reflective coatings and a tightly spaced array of lines to the backs of ultrathin silicon films to boost the cells' output by as much as 50 percent. [No official statement has been released on original vs improved efficiency level.]
The coatings on the back of the solar cell force the light to bounce around longer inside the thin silicon layer, giving it time to deposit its energy and produce an electric current. "Without these coatings, light would just be reflected back out into the surrounding air" said Peter Bermel, an MIT postdoctoral physics researcher.
"It's critical to ensure that any light that enters the layer travels through a long path in the silicon," Bermel said. "The issue is how far does light have to travel [in the silicon] before there's a high probability of being absorbed" and knocking loose electrons to produce an electric current.
Why is this important to the future? Depending on the range of its applications, this type of breakthrough could transform solar efficiencies for traditional crystalline (glass substrate) solar cells as well as thin film (carbon substrate) solar.
While we invest in commercializing solar energy systems, we must not turn our backs on funding basic science that can yield fundamental breakthroughs. "The simulated performance was remarkably better than any other structure, promising, for 2-micrometer-thick films, a 50 percent efficiency increase in conversion of sunlight to electricity," said Lionel Kimerling, the Thomas Lord Professor of Materials Science and Engineering, who directed the project.
Researchers at US Los Alamos National Laboratory (LLNL) have confirmed a unique energy phenomena known as 'carrier multiplication' via nanoscale sized semiconductor crystals that could improve the efficiency of solar cells by squeezing more energy out of inbound photons.
Traditional solar cells absorb a photon of light that releases an electron to generate an electrical current. Any excess energy from the photon reaction is wasted as heat or vibration. The notion of 'carrier multiplciation' rests on the idea that we can get multiple electrons released from a single photon by forcing electrons into a more confined space.
This idea was observed several years ago, but has been criticized as a phantom phenomena via a process known as 'photoionization. Now a research team led by Victor Klimov has confirmed that semiconductor crystals designed at the nanoscale (billionth of a meter) can channel this excess photon energy into a group of tightly packed electrons, leading to a more efficient solar cell.
The team did not release statements about commercialization or scalable efficiencies. “Researchers still have a lot of work to do,” Klimov cautioned. “One important challenge is to figure out how to design a material in which the energetic cost to create an extra electron can approach the limit defined by a semiconductor band gap. Such a material could raise the fundamental power conversion limit of a solar cell from 31 percent to above 40 percent.”
The future where buildings integrate energy generation systems like 'thin film' solar rooftops might be closer than you think.
Instead of designing expensive, bulky and ugly glass based solar panels, solar start ups are pushing down costs of plastic-substrate based 'thin film' solar cells that resemble today's roof shingles. The field also includes 'Big Chemistry' players like Dow and DuPont who hope to drop the costs of advanced solar materials.
PV Tech is reporting on the continued push by Dow Chemical to expand mainstream construction use power-generating roof shingles by 2011. Dow has already committed more than $3 billion towards polysilicon production that will help lower the global costs of solar cells.
“This facility has state-of-the-art printing capabilities that are ready for full operation, with the future potential to produce over a gigawatt of flexible plastic solar modules per year,” commented Howard Berke, executive chairman and co-founder of Konarka. “Our technical leadership and innovation in flexible thin film solar, along with this facility’s capabilities of producing in excess of 10 million square meters of material per year, will allow us to produce Power Plastic for indoor, portable, outdoor and building integrated applications.”
Konarka has long been considered a leading start up in the solar field, but this Gigawatt production capacity helps to cement its position among a growing base of thin film competitors. Analysts have been fond of describing ‘spectacular growth’ ahead for thin film solar, but near term expansion is not likely to be as easy as paper forecasts as the solar industry confronts fundamental challenges including rising costs of raw materials. Rising costs aside, the solar industry is expected to grow from a market volume of 5.6 GW in 2008 to 79.5 GW in 2015. And if thin film companies like Konarka can continue to open large scale MW and GW capacity plants they should certainly expect bright days ahead.
Thin-film- solar startup XsunX, Inc. is moving forward on building out
its 25 megawatt thin film photovoltaic (TFPV) solar module
manufacturing plant in Oregon. A recent company press release describes the companies efforts to align material resources with low cost manufacturing process for its 90,000 square foot facility. The company expects to begin commercial production in early 2009.
Last week we reported on the opening of the first 1 Gigawatt capacity thin film solar plant operated by Konarka. (Konarka image shown) XsunX now appears to be on track to add to real production capacity for the thin film solar market.
Energy forecasters believe that growth of thin film solar could soon surge around its advantages over traditional glass-based solar panels.
While thin film’s performance (by energy conversion efficiency) is lower than traditional solar panels, it has a cost advantages per-watt because of its lower materials and manufacturing ‘roll to roll’ costs. Thin film can also be integrated into more products and building materials, and sold over retail shelves at Home Depot, Walmart and Tesco.
If XsunX and Konarka (Image) stay on course, soon solar panels will be produced on the same types of ‘reels’ that spit out newspapers using inkjet printing processes.
Leaked photos of the next generation Mac Mini suggest that Apple is committed to steadily shrinking components and appears to be on the road to something that may look a lot like this vision of the iPhone 2015 that we published last November:
Sometimes it’s hard for people to get an accurate sense of what the future holds for certain technologies. For instance, could the average person three years ago have imagined that something like the 3G iPhone could exist now?
It is for this reason I present this vision of the iPhone circa 2015.
Contact Lens Display
The most interesting feature of the iPhone 2015 is its first generation Contact Lens Display System. If there’s one thing that iPhone users believe themselves to be, and that Apple stresses all the time, it’s that people who use Apple products are independent and unique. It is for this reason that an eyeglass display was thrown out. No iPhone user would be caught dead wearing the same glasses as over ten million other iPhone users. The fact is, glasses are cumbersome. They gather dirt, get lost easily, and make sports rather difficult.
In 2007, development of a contact lens display system began at the University of Washington, Seattle. “Engineers at the University of Washington have for the first time used manufacturing techniques at microscopic scales to combine a flexible, biologically safe contact lens with an imprinted electronic circuit and lights.” In the time between now and 2015, the cost involved in the production of a contact lens display will likely reduce in price, meaning the loss of one won’t reduce you to tears in case of loss.
The problems associated with contact lenses (protein build-up, 8-hour wear limit, annoyance of constant inserting and removal) will be lessened with oxygen-permeable lenses. O2OPTIX, a company currently specializing in such breathable lenses, already sells a lens capable of week-long wear without removal. “O2OPTIX is made with a revolutionary silicone hydrogel technology allowing up to 5 times more oxygen through the lens than the leading traditional 2-week lens, to help protect from the signs and symptoms of corneal oxygen deficiency.” It only makes sense that seven years from now a lens will be developed which can last even longer making wearable contact lenses less of a pain.
Of course there always is the option of implanting the lens permanently into the eye, but who would ever go under invasive surgery for first generation technology?
Bo Albinsson at Chalmers University of Technology in Gothenburg, Sweden, has figured out a way to use DNA as a nano fiber optic cable. They accomplish this by combining DNA strands with a chromophore called YO which has a strong attraction to DNA molecules. By wedging itself into areas of DNA, a 3nm diameter fiber optic cable is born (these fibers are self-assembling).
Fiber optic cables have become more commonplace in the world and are expected to take an even bigger step into the solar energy business by improving photo voltaic cells. Optical computers could also benefit greatly from photon-specific nanowires.
Barack Obama's energy platform included goals for renewable energy, higher automoative gas mileage standards, support for plug-in hybrid electric vehicles, and targets for energy efficiency of homes...and that's just to start. With the recent announcement of Nobel laureate and now former head of the Lawrence Berkeley National Laboratory Steven Chu as Energy Secretary, Obama's administration can be the catalyst that makes alternative energy markets viable.
Will the Obama administration be successful in making the energy changes he promised in the election?
The Future of Energy will be based on our ability to elegantly control the interactions of light, carbon, hydrogen, oxygen and metals. And for all our engineering prowress of extracting and blowing up ancient bio-energy reserves (coal/oil), there is still so much to learn about basic energy systems from Mother Nature.
Laying Down Algae Shells for Solar Panels Researchers from Oregon State University and Portland State University have developed a new way to make “dye-sensitized” solar cells using a 'bottom up' biological assembly processes over traditional silicon chemical engineering.
The teams are working with a type of solar cell that generates energy when 'photons bounce around like they were in a pinball machine, striking these dyes and producing electricity.'
Rather than build the solar cells using traditional technqiues, the team is tapping the outer shells of single-celled algae, known as diatoms, to improve the electrical output. (Diatoms are believed to be the ancient bio-source of petroleum.)
The team placed the algae on a transparent conductive glass surface, and then (removed) the living organic material, leaving behind the tiny skeletons of the diatoms to form a template that is integrated with nanoparticles of titanium dioxide to complete the solar cell design.
Biology's Nanostructured Shells & Bouncing Photons? “Conventional thin-film, photo-synthesizing dyes also take photons from sunlight and transfer it to titanium dioxide, creating electricity,” said Greg Rorrer, an OSU professor of chemical engineering “But in this system the photons bounce around more inside the pores of the diatom shell, making it more efficient.”
The research team is still not clear how the process works, but 'the tiny holes in diatom shells appear to increase the interaction between photons and the dye to promote the conversion of light to electricity... potentially with a triple output of electricity.'
According to the team, this is the 'first reported study of using a living organism to controllably fabricate semiconductor TiO2 nanostructures by a bottom-up self-assembly process.' So, chalk up another early win for advanced bio-energy manufacturing strategies!
Researchers from Northeastern University and the National Institute of Standards and Technology (NIST) have improved the efficiency of clustered nanotubes used in solar cells to produce hydrogen by splitting water molecules.
By layering potassium on the surface of the nanotubes made of titanium dioxide and carbon, the photocatalyst can split hydrogen gas from water using ‘about one-third the electrical energy to produce the same amount of hydrogen as an equivalent array of potassium-free nanotubes.’
Rethinking the Possibilities at the Nanoscale Energy is about manipulating the interactions of carbon, hydrogen, oxygen, metals, biological enzymes and sunlight.
When we design core enabling energy systems (e.g. catalysts, membranes, cathodes/anodes, et al) at the nanoscale (billionth of a meter) we find performance that is fundamentally different from the same systems designed at the 'microscale' (millionth of a meter).
Because smaller is better when it comes to manipulating molecules and light, the research teams used ‘tightly packed arrays of titania nanotubes’ with carbon that ‘helps titania absorb light in the visible spectrum.’ Arranging catalysts in the form of nanoscale-sized tubes increases the surface area of the catalyst which in turn increases the reactive area for splitting oxygen and hydrogen.