Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.
Plants are the most efficient solar converters known to man, and their tool of trade is photosynthesis. We do try to replicate it synthetically but it requires breaking water into oxygen and hydrogen gases via electrolysis (using electricity to stimulate the separation). Solar-driven electrodes exist but they degrade quickly in water-driven applications. But a team at Caltech found that via “reactive sputtering under high vacuum” nickel could be coated onto the electrodes as a protective coating with a thickness of 75 nanometers giving optimal performance. They have some other convenient properties also like being “transparent and antireflective…conductive, stable, and highly catalytically active,” all great advantages (Saxena).
Solar Meets Thermal Physics
Airlight Energy, Dsolar, and IBM Research in Zurich have developed a rig which generates both solar and thermal power at the same time, giving about an 80% efficiency rating. Dubbed the Solar Sunflower, it uses the sun to create electricity as well as thermal power using highly efficient concentrated photovoltaic/thermal (HCPVT) cells to make our sun’s output mimic that of 5,000 suns. To accomplish this, 36 reflectors cast light onto 6 collectors which are a group of gallium-arsenide photovoltaic cells totaling a few square centimeters per collector but are capable of generating 2kW of electricity each. But this generates temperatures as high as nearly 1500 degrees Celsius. To cool this off, water surrounding the cells acts like a heat sink, gathering that warmth up to about 90 degrees Celsius. It is then used as hot water for various applications. To summarize, the solar method generates 12kW while the thermal generates 21 kW (Anthony).
Solar Meets Quantum Mechanics
One of the limiting factors in solar cell technology is the wavelength response range. Only certain values work well for efficient conversion of energy, and the window can be quite narrow. This is due to the semiconductor’s bandgap, or the energy that is needed to get an electron into a movable state of excitability. Usually stacking solar cells of different wavelengths is a partial solution. But scientists at West Virginia made use of a quantum feature – virtual photons from electron excitability – to help this process out. If one has materials that intake one type of light and expel a different wavelength, then one can gap them perfectly so that the virtual proton that is released from one material gets absorbed by another which starts off a chain going from blue light (high energy) to red light (low energy)…in theory. But quantum mechanics has a fuzzy factor to it and through coherence we can get several transitions possible for a given material, even if the probability of it happening is low. If one covers gold spheres ( a conductor) with a semiconducting material, then the free electrons around the gold oscillate as they cohere and that affects the probability field for the semiconductor, lowering the bandgap needed and thus allowing for easier access to electrons that can move about in the semiconductor and thus allow the material to absorb more photons than previously was possible (Lee "Turning").
Cooking with Solar Steam
Imagine cooking food using solar rays and how many applications that could yield. We could do this with enough mirrors to concentrate the sunlight onto a point but is there an easier way to get it done? MIT scientists found a way to get it done using a floating rig the size of a small pot. It works by absorbing the visual portion of the spectrum but doesn’t radiate much heat courtesy of the polystyrene foam insulating it. The absorbing material is inside this container and is sealed with a plate of copper that has a plastic cover to allow water vapor to be released. This rigging can heat water to boiling point in about 5 minutes, with no mirrors involved at all. Applications include easy heat generation for the evening and a great way to sanitize water (Johnson).
Invisible Solar Cells
Yes, it sounds crazy but scientists have found a way to use glass as a solar cell. The material involves nanoparticles coated with ytterbium. These will emit two infrared photons as the electrons jump orbitals, and these happen to be perfect for silicon to absorb and are also highly unlikely to be absorbed by the ytterbium again. The silicon in turn will emit two electrons for each of the infrared photons, and boom we get our electricity. With a nanosheet of this put onto glass, it offered the best heat-option for maximum electron withdrawal. The catch? The transparency means most photons are not being used, so not too efficient but maybe coupled with the right system and who knows...(Lee "Transparent").
With all the known limits on solar tech, innovative ideas are welcomed. So how about bending our semiconductors inside our solar cells? Using a nano-indentor, the surface of the semiconductors involving strontium titanate, titanium dioxide, and silicon can have their structure altered to actually increase their photo-voltaic effects. This is great because these are readily available materials and integrating the tech wouldn't be too hard. Who knew (Walton)?
Anthony, Sebastian. “The Solar Sunflower: Harnessing the Power of 5,000 Suns.” arstechnica.com. Conte Nast., 30 Aug. 2015. Web. 14 Aug. 2018.
Johnson, Scott K. “Floating solar device boils water without mirrors.” arstechnica.com. Conte Nast., 26 Aug. 2016. Web. 14 Aug. 2018.
Lee, Chris. "Transparent solar cell turns edge on and generates its own light." arstechnica.com. Conte Nast., 12 Dec. 2018. Web. 05 Sept. 2019.
---. “Turning red to blue for solar energy.” arstechnica.com. Conte Nast., 23 Aug. 2015. Web. 14 Aug. 2018.
Saxena, Shalini. “Nickel oxide films enhance solar-driven splitting of water.” arstechnica.com. Conte Nast., 20 Mar. 2015. Web. 14 Aug. 2018.
Walton, Luke. "New research could literally squeeze more power out of solar cells." innovations-report.com. innovations report, 20 Apr. 2018. Web. 11 Sept. 2019.
© 2019 Leonard Kelley