from Hacker News

Scientists Design Solar Cell That Captures Nearly All Energy of Solar Spectrum

by 3eto on 7/12/17, 4:59 PM with 128 comments

• by sbierwagen on 7/12/17, 5:46 PM

  As usual with press releases, this pretends there is no prior art. Of course, stacking solar cells to increase efficiency has been a thing for five decades: https://en.wikipedia.org/wiki/Multi-junction_solar_cell

• by matt_wulfeck on 7/12/17, 6:10 PM

  I just had my panels turned on. I love solar. It's still difficult to justify it short-term on a cost-basis, but I'm saving about a dollar a day after all things are said and done.

  That being said, I'm generating my own electricity and my panels will run for a very long time. The best is cranking the AC and still watching the meter run in reverse during really scorching days.

• by meri_dian on 7/12/17, 5:11 PM

  >"This particular solar cell is very expensive, however researchers believe it was important to show the upper limit of what is possible in terms of efficiency. Despite the current costs of the materials involved, the technique used to create the cells shows much promise. Eventually a similar product may be brought to market, enabled by cost reductions from very high solar concentration levels and technology to recycle the expensive growth substrates."

  We will end our reliance on fossil fuels not by forcing masses of people to change their lifestyles and inconveniencing them, but by developing green energy tech that is simply more efficient and cost effective than fossil fuels. Once this happens the transition away from carbon based energy sources will be swift.

  Given the rate of progress, I believe we'll see widespread adoption of renewable energy far before climactic conditions on earth become dire for humanity.

• by adamwong246 on 7/12/17, 6:26 PM

  I always wondered why we did not just use prisms to separate the different wavelengths, then capturing selections of the spectrum with a variety of simpler, unstacked panels. Perhaps one could even deflect the infrared into a more conventional, presumably more efficient, heat collector while the higher frequencies are directed to true photovoltaics.

• by vectorjohn on 7/13/17, 12:51 AM

  What is it that makes solar panels cost what they do, ultimately? Not materials, right? Those are all basically sand and other not so special things. Labor? Isn't it mostly automated? Upkeep of the factories? Input energy?

  Maybe it's just all those things together. But it sure seems like if we wanted to it wouldn't be that hard to ramp up production and drive costs down a couple fold. Not that I know how.

• by Gys on 7/12/17, 5:36 PM

  'The new design converts direct sunlight to electricity with 44.5 percent efficiency, giving it the potential to become the most efficient solar cell in the world.'

• by philipkglass on 7/12/17, 6:05 PM

  The abstract is more informative than the press coverage:

  http://onlinelibrary.wiley.com/doi/10.1002/aenm.201700345/ab...

  The cell is assembled in a mini-module with a geometric concentration ratio of 744 suns on a two-axis tracking system and demonstrated a combined module efficiency of 41.2%, measured outdoors in Durham, NC. Taking into account the measured transmission of the optics gives an implied cell efficiency of 44.5%.

  Since this is a concentrating cell, compare to the concentrator cell records tracked on NREL's PV efficiency records chart:

  https://www.nrel.gov/pv/assets/images/efficiency-chart.png

  The current record for 4-junction-or-more concentrator cells is 46.0%. This isn't a record-setting cell even if the implied efficiency holds up under standardized test conditions.

  This cell like all high-concentration cells is unlikely to see mass market acceptance on Earth. The module needs precise two-axis sun tracking to work effectively even under perfect clear-sky conditions. That's significantly more expensive than fixed arrays or single-axis sun tracking as used by conventional large scale PV. And there's a vicious feedback loop: since two-axis tracking is significantly more expensive, it doesn't get developed/scaled, so the cost gap gets even wider over time WRT its competitors.

  But that's not actually the worst problem of high-concentration PV for terrestrial use. The worst problem is that HCPV can use only direct normal irradiance. Ordinary non-concentrating PV cells produce very nearly 25% of its rated output if it receives 25% of test-condition illumination under non-ideal conditions (due to some combination of clouds, air pollution haze, dusty glass, etc.) Concentrating cells will produce close to 0% of rated output under the same non-ideal conditions. Few regions have clear enough skies to work with HCPV, but those same regions tend to be dusty, which the concentrating optics cannot tolerate. Mechanical and optical complications make HCPV higher-maintenance than ordinary flat PV and more expensive to install initially.

  That's why there were a dozen+ companies working on concentrating PV in 2008 and all of them are now bankrupt or have exited HCPV manufacturing. Eking out another cell-level improvement wouldn't have rescued the value proposition of their complete systems. The refined polysilicon price spike that made exotic technologies look briefly promising only lasted a few years and then it became clear again that crystalline silicon is very hard to beat.

• by grandalf on 7/13/17, 2:00 PM

  Would these panels capture energy from the signal being radiated by my mobile phone? What about gamma rays?

  In other words, is a solar cell something that captures energy from photons and converts it into usable electricity? Or from some subset of photons?

• by afeezaziz on 7/12/17, 5:27 PM

  If the process to make this kind of solar cell can be lowered enough through scale then they should communicate this process to Chinese solar companies. I am sorry for my poor understanding of chemical process; if the materials of the solar cell are roughly the same then it would be quite easy for the existing manufacturers to actually switch to this solar cell production.

  I cannot wait for the era of super cheap electricity!