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]
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]
Researchers at Stanford University claim to have developed the world’s first peel-and-stick thin-film solar cells (TFSCs) that don’t require any modification of existing processes or materials. The new process would allow the creation of decal-like solar panels that could be applied to virtually any surface.
Unlike with standard thin-film solar cells, the new process doesn’t require direct fabrication on a final carrier substrate. Instead, a 300-nm film of nickel (Ni) is deposited on a silicon/silicon dioxide (Si/SiO2) wafer, on which thin-film solar cells are then deposited using standard fabrication techniques, and covered with a layer of protective polymer. A thermal release tape is then attached to the top of the thin-film solar cells as a temporary transfer holder. [via]
Peel-and-stick solar cells - [Link]
This teardown article will delve into the architectural design and components of a solar inverter card starting from the Solar panel DC inputs and working our way through the DC to AC conversion process to the AC output that is sent out to the power grid. We will show what features need to be implemented into such a design to meet various safety and other performance standards as well as stringent power company demands upon the signal that is put onto their grid.
Teardown: The power inverter – from sunlight to power grid - [Link]
By Lee H. Goldberg:
The Schottky bypass diodes used in most cell-based solar panels serve as a protection mechanism that allows the panel to continue producing power when one of its cell strings is shaded or damaged. However, the characteristics of traditional diodes create energy losses that reduce the overall efficiency of a solar power system and, in some situations, may actually cause costly damage. To solve this problem, several manufacturers have introduced a new class of “active diodes” that use transistors to produce diode-like behavior, while allowing the solar panels they protect to operate with higher efficiency and better reliability. This article will explore the technology that underlies active diodes, look at the products currently on the market, and look at how they are changing the way solar panels are being designed and manufactured.
Active Bypass Diodes Improve Solar Panel Efficiency and Performance - [Link]
MIT engineers have proposed a new way to improve solar cell performance by using special ‘funnels’ to capture photons. The funnels would be formed in a thin film of semiconductor material by pressure from microscopic needles, producing elastic strain in the funnel area. The strain causes the band gap of the material to vary over the surface of the funnel, which allows a broader spectrum of light to be converted into electricity. The electron/hole pairs produced by the photons in the incident light would also be guided toward the centre of each funnel by electrical forces, improving efficiency compared to the usual diffusion process.
The MIT team used computer modelling to determine the effects of elastic strain on a funnel depression in a thin sheet of molybdenum disulphide (MoS2), a natural semiconductor material that can form films just one molecule thick. The elastic strain, and the corresponding change in the potential energy of the electrons, varies with the distance from the centre of the funnel. The potential energy determines the wavelength of the photons that can be captured by the material, and thus the portion of the light spectrum that can be converted into electricity. The team hopes to carry out laboratory experiments in the future to confirm their theoretical findings. [via]
Energy Funnels Boost Solar Cell Performance - [Link]