Startup company Aquion Energy gave MIT Technology Review a behind-the-scenes look at their battery manufacturing process. The company’s goal is to make non-toxic, cheap batteries for storing off-grid energy. The batteries will first be sold in regions that don’t have access to an electrical grid, such as rural areas and villages in poor countries.
How to Make a Cheap Battery for Storing Solar Power - [Link]
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]
Bill Schweber writes:
The power-management IC (PMIC) supports and manages the transducer and energy-collection channel, the energy-storage element (battery, conventional capacitor or supercapacitor), and the processor/wireless link. This critical block of any energy-harvesting design implements several major functions: Captures and extracts the random, miniscule energy from the source transducer, Transforms that extracted power into energy for the storage element, usually via a DC/DC converter, Manages the outflow of power from the storage element, while ensuring that power is not drawn when the stored energy is below a threshold value and would be wasted, Perhaps most challenging, it has to manage its own start-up sequence in the transition from when there is insufficient available stored energy for the PMIC itself.
Choosing a Power Management IC for Energy-Harvesting Applications - [Link]
An application note from Microchip: Practical guide to implementing Solar Panel MPPT Algorithms (PDF!)
This application note describes how to implement MPPT using the most popular switching power supply topologies. There are many published works on this topic, but only a tiny portion of them show how to actually implement the algorithms in hardware, as well as state common problems and pitfalls. Even when using the simplest MPPT algorithm with a well-designed synchronous switching power supply, it can be expected that at least 90% of the panel’s available power will end up in the battery, so the benefits are obvious.
Practical guide to implementing Solar Panel MPPT Algorithms - [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]