by Publitek European Editors:
Monitoring is the key to unlocking the energy production of the solar cell. It is easy to lose efficiency through the use of circuit architectures that assume constant energy production when the solar environment is constantly changing.
The change in current-voltage properties as a solar module heats up or receives more light can be an important source of efficiency losses in solar arrays. If the inverter that generates grid-compatible electricity is not tuned to the output voltage and current conditions, it will waste more of the electricity than it should. In response, electronics companies have produced ICs that perform the maximum power-point tracking (MPPT) needed to optimize energy conversion as well as bypass electronics to prevent temporarily unproductive modules from disrupting the output of active cells.
Maximizing the Output from Solar Modules – [Link]
Researchers Steve Dunn at Queen Mary University and James Durrant at Imperial College London have been experimenting with a new design of thin, flexible solar cell made from zinc oxide. Manufacturing costs of the new cells will be significantly lower than conventional silicon based technology. The only disadvantage is their poor efficiency; just 1.2 %, a fraction of that achievable with silicon.
The material also exhibits piezo-electric properties, nanoscale rods of the material generate electricity when they are subjected to mechanical stresses produced by sound wave pressure. Sound levels as low as 75dB, equivalent to that from an office printer, were shown to improve efficiency. Durrant said “The key for us was that certain frequencies increased the solar cell output, we tried our initial tests with various types of music including pop, rock and classical”. Rock and pop were found to be the most effective. Using a signal generator to produce sounds similar to ambient noise they saw a 50 % increase in efficiency, rising from 1.2 % without sound to 1.8 % with sound.
New Solar Cell Shows a Preference for AC/DC – [Link]
Julian Ilett demonstrates his Arduino Solar Charge Controller. He has mounted all of his Arduino modules to a piece of wood to keep everything nice and neat. [via]
“High efficiency values (96% – 97%) are achievable when the buck converter is stepping down from 18v to 12v. With a 72-cell panel and the converter stepping 35v down to 12v, the efficiency drops to around 88%.”
Arduino Solar Charge Controller – [Link]
A team comprised of the Fraunhofer Institute for Solar Energy Systems, Soitec, CEA-Leti and the Helmholtz Center, Berlin has just unveiled the world’s most efficient solar cell! Boasting an efficiency of 44.7%, the cell breaks the record set by Sharp just three months ago by 0.3%. The four-junction photovoltaic cell is not only dramatically more efficient than the theoretical 33.7% efficiency limit of conventional silicon-based solar PV, but it puts the team well on the road to reaching their goal of 50% efficiency by 2015.
German-French Team Unveils World’s Most Efficient Solar Cell! – [Link]
Graphene is by definition flat and planar, but researchers at Michigan Tech have discovered a manner of fabricating 3-D graphene–a honeycomb structure that can replace the expensive precious metals in solar cells and potentially other energy applications such as batteries and even superconductors. [via]
3D Graphene for Cheaper Solar Cells – [Link]
Super Capacitors have become more popular over the past 5 years and are beginning to replace batteries in some applications. Charging a super cap can be tricky especially if you want to avoid damaging it. Here is a basic circuit that will allow you to charge a super capacitor with a solar panel.
How to Charge a Super Capacitor with a Solar Panel – [Link]
Battery-Charging Controllers for Energy Harvesters by Jon Gabay:
Whether your energy harvesting application uses large solar panels with high voltages and currents or, more often the case, must make do with minute amounts of power derived from various other ambient energy sources, one thing is almost certain: some type of energy storage is on board, whether in the form of a small rechargeable lithium ion battery, a supercapacitor, or solid-state energy storage technology. For the engineer this means that not only do we need to design circuits to harvest and convert ambient energy, but we also have to include an energy-harvesting interface (and protection circuitry) as well as a charge controller. This article looks at single chip energy harvesting devices that also provide some form of charge control. It discusses the different conditions under which energy can be extracted as well as what to expect when trying to squeeze power out of the ambient environment. Finally, the article will present some typical integrated solutions for small-sized low-power energy-harvesting designs.
Battery-Charging Controllers for Energy Harvesters – [Link]
A special circuit is needed when charging a battery from a Solar Panel. When the solar panel is not providing any power the battery might start draining current into the panel. One common solution is to have a diode in series with the charging circuit to keep the current from going back to the solar panel. The problem with using a diode is the voltage drop across the diode reduces the available voltage for charging.
This circuit is great because the LTC4357 prevents the current back feeding into the panel without having the voltage drop limitation of the diode circuit
Solar Panel Charging Circuit – [Link]
The following is important because with flexible organic photovoltaic cells, we are nearing a new era of development for practical solar-based solutions can be implemented with clever usage of these devices. Efficiency needs to be higher, but technology is progressing in the right direction and a breakthrough is inevitable.
Heliatek announced a record breaking 12.0% cell efficiency for its organic solar cells. This world record, established in cooperation with the University of Ulm and TU Dresden, was measured by the accredited testing facility SGS. The measurement campaign at SGS also validated the superior low light and high temperature performances of organic photovoltaics (OPV) compared to traditional solar technologies.
New world record for organic solar technology with a cell efficiency of 12% – [Link]