In December 2013 Linear Technology announced a new chip – LT8490. This chip includes a 80V Buck-Boost Lead Acid & Lithium Battery Charging Controller that actively finds true Maximum Power Point in solar applications.
No yet available, that chip looks very promising. It operates with input voltages down to 6V and can boost that to charge batteries with higher voltage. I made already a schematic and board design from the preliminary datasheet that charges a 3S LiPo from a solar panel with up to 5A. A small board size allows usage in model gliders with large wing span to charge the battery in flight.
Solar charger with MPPT - [Link]
Maximum power point tracking (MPPT) is a technique that solar battery chargers and similar devices use to get the maximum possible power from one or more solar panels (several solar cells connected in series and parallel). Solar cells have a complex relationship between solar irradiation, temperature and total resistance that produces a non-linear output efficiency known as the I-V curve. It is the purpose of the MPPT system to sample the output of the cells and apply the proper load to obtain maximum power for any given environmental conditions.
Solar Cell MPPT - [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]
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]
Chris Glaser writes:
Many solar-panel-powered applications need only pulses of power to operate. Systems for data collection or measurement sampling frequently need to turn on, perform a measurement or some other task, transmit the processed or measured data, and return to sleep. In many cases, wirelessly transmitting the data consumes the largest portion of output power. These required power pulses, either for the system itself or for transmitting data, typically are difficult to support with a power-limited supply such as a solar panel. By operating at the solar panel’s maximum power point (MPP) and by intelligently drawing the power from the panel, energy can be successfully harnessed to power a pulsed load. This article presents a simple and costeffective solution for maximum-power-point tracking (MPPT) for use in such pulsed-load systems.
Easy solar-panel maximum-power-point tracking for pulsed-load applications - [Link]
The LTC®4000-1 is a high voltage, high performance controller that converts many externally compensated DC/DC power supplies into full-featured battery chargers with maximum power point control. In contrast to the LTC4000, the LTC4000-1 has an input voltage regulation loop instead of the input current regulation loop.
Features of the LTC4000-1’s battery charger include: accurate (±0.25%) programmable float voltage, selectable timer or current termination, temperature qualified charging using an NTC thermistor, automatic recharge, C/10 trickle charge for deeply discharged cells, bad battery detection and status indicator outputs. The battery charger also includes precision current sensing that allows lower sense voltages for high current applications.
LTC4000-1 – High Voltage/Current Controller for Battery Charging with Maximum Power Point Control - [Link]
Steve Taranovich writes:
Home energy systems based on renewable sources, such as solar and wind power, are becoming more popular among consumers and will gain increasing support from governmental bodies.
In this article, the power inverter will be discussed in the context of solar energy, especially as it relates to the latest, low power microinverter architectures that make the most sense in converting a photovoltaic (PV) panel’s DC output to an AC signal for residential use.
Microinverters are installed on each individual PV panel and typically handle 300 W. Microinverters provide the benefit of scalability for those who want to start small, yet have full DC/AC conversion with maximum power point tracking (MPPT). Many people want to put their excess power back onto the power grid, which will speed up the return on investment (ROI) time and ultimately could lead to freedom from grid reliance. The technology that will enable ubiquitous architectures like this on our roof is getting closer.
An Engineer’s Guide to Power Inverters for Solar Energy Harvesting - [Link]
The SM72441 is a programmable MPPT controller capable of controlling four PWM gate drive signals for a 4-switch buck-boost converter. Along with SM72295 (Photovoltaic Full Bridge Driver) it creates a solution for an MPPT configured DC-DC converter with efficiencies up to 98.5%. Integrated into the chip is an 8-channel, 12 bit A/D converter used to sense input and output voltage and current, as well as board configuration. Externally programmable values include maximum output voltage and current as well as different settings on slew rate, and soft-start.
Programmable Maximum Power Point Tracking Controller for Photovoltaic Solar Panels - [Link]
Energy harvesting with a photovoltaic cell requires an efficient dc-dc converter that operates with very low voltage inputs and whose output can charge an external battery. The newly introduced LTC3105 meets these requirements.
Sam Davis writes:
ENERGY HARVESTING CAN EMPLOY SURPLUS OR AMBIENT energy to trickle charge a battery that supplies system power. This eliminates the need to for an ac power line-based recharging circuit, which may be impractical in a remote application. Typically, these applications require very low average power, but can require periodic pulses of higher load current. The Linear Technology LTC3105 is intended for these types of energy harvesting applications.
The LTC3105 is a high efficiency dc-dc boost converter (Fig. 1) that has a 250mVstart-up capability. A resistor divider connected between the VOUT and FB pins adjusts the converter output from 1.5V to 5.25V. An integrated maximum power point controller (MPPC) optimizes performance from photovoltaic (PV) cell inputs. The LT3105′s 3mm × 3mm DFN package (or MSOP-12) and very small external components offer a compact solution for energy harvesting.
LTC3105 DC-DC Boost Converter Harvests Photovoltaic Energy - [Link]
High brightness LEDs and special optics allow street lamps to be spaced up to 50 meters apart — much wider than is possible with other solutions. By charging these street lamps efficiently during daylight hours using solar energy, the capacity of the conventional electricity grid can be supplemented, saving money and reducing CO2 emissions. This solution dubbed Solar Gen2 and developed by NXP Semiconductors in collaboration with Philips Lighting has resulted in the most cost-effective solution per km of road lighting and provides a serious alternative to grid-connected AC systems.
NXP’s MPT61x range of intelligent charge controllers for maximum power point tracking (MPPT) make it possible to transfer the maximum amount of power from the solar panels to the batteries, achieving up to 98% power conversion efficiency with solar photovoltaic (PV) cells. The controller that includes an ARM7TDMI-S MCU core running at 70 MHz features intelligent algorithms for battery charging and discharging to maximize battery life and it is also capable of dimming light levels as needed based on self-learning and a history log. [via]
Self-learning solar-powered LED street lights save energy - [Link]