Piezoelectric Ribbons Print onto Rubber for Energy Harvesting

Researchers at Princeton and CalTech have developed a way of printing piezoelectric elements onto rubber so that they generate current when the rubber moves. This allows breakthroughs in implantable or wearable energy harvesting systems where the motion of the person powers the electronics, particularly low energy sensors.
Being electromechanically coupled, piezoelectric crystals represent a particularly interesting subset of smart materials that function as sensors/actuators, bioMEMS devices, and energy converters. Yet, the crystallization of these materials generally requires high temperatures for maximally efficient performance, rendering them incompatible with temperature-sensitive plastics and rubbers. The researchers have overcome these limitations by presenting a scalable and parallel process for transferring crystalline piezoelectric nanothick ribbons of lead zirconate titanate from host substrates onto flexible rubbers over macroscopic areas.

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Ultra low power microcontroller extends battery life

A Norwegian startup is pushing the limits of low power in microcontrollers, cutting power by a factor of four over even 8bit devices.
Energy Micro has developed the EFM32 low power 32bit microcontroller based on the ARM Cortex-M3 architecture with low power clocks and peripherals that consumes less than 180µA per MHz while executing real life code from Flash memory and the lowest active mode current consumption of any microcontroller. Its standby current consumption is also the lowest, at typically 900nA while running real time clock, power-on reset, brown-out detector and full RAM and CPU retention and less than 20nA in its deepest sleep mode. The start-up time of less than 2µs is also the industry’s fastest. The power is lower than traditional 16 or 8bit devices from Silicon Labs, Texas Instruments and Microchip (see chart).

“We are very proud that we have delivered on our mission to provide the world with the most energy friendly microcontrollers,” said Geir Forre, founder and CEO. “By introducing innovative new energy saving features, such as our peripheral reflex system and energy management unit, the potential saving in battery life that can be achieved is immense.”

The low power peripherals include:
a 4x40 segment LCD controller running at less than 900nA;
an 8-channel 12-bit 1M samples/sec ADC running at less than 200µA;
a brown-out detector running at less than 100nA;
a 32kHz real time counter running at 50nA;
and a UART capable of 9600bps at 100nA.

The devices, built in standard low leakage CMOS, are initially targetted at smart metering and home automation, with battery lifetimes of 10 to 15 years with low cycle times. “The EFM32G family of microcontrollers has been specified in close partnership with many world leading companies within, for example, the energy metering, home and building automation and alarm and security industries,” said Øyvind Janbu, co-founder and CTO of Energy Micro. “Working so closely with top engineers in such sectors has enabled us to produce a family of microcontrollers that truly is a perfect fit for a variety of different applications.”
One of Energy Micro’s partner customers is window maker Velux, one of the strongest brands in the global building materials and home improvement industry. It is planning to use the EFM32 in a range of contorllers later this year.
Meter company Kamstrup is also looking to use the device for products next year.
There are 22 different EFM32G microcontroller products which will become available over the next few months, in a variety of packages including QFN32, QFN64, QFP100 and BGA112. The EFM32G operates from a single supply rail of between 1.8 and 3.8V. The operating temperature range is –40degC to +85degC. The microcontrollers provide up to 128KB Flash memory and up to 16KB of RAM.
The first products are being offered by Energy Micro in QFN64 and BGA112 profiles and are currently sampling with lead customers. Pricing for the initial 32-pin devices starts at $1.55 in 100k quantities.

Low power USB development kit from TI at $49

With a low power digital signal processor, Texas Instruments has managed to develop a development kit in a USB stick which drops the cost of a full-featured emulator and integrated development platform down to $49. This enables rapid creation of DSP applications including portable audio players, voice recorders, IP phones, portable medical devices, biometric USB keys, software defined radios (SDRs), hands-free headsets and metering applications. At this extremely low price point, it is the industry’s lowest cost DSP tool, making development accessible to existing and potential customers, hobbyists, researchers and students.
The TMS320VC5505 eZdsp USB stick development tool simplifies development by providing integrated features such as an on-board XDS100 emulator and on-board audio codec and connectors. Taking advantage of the energy efficient C5505 DSP, the eZdsp requires no other components or cables allowing the entire development tool to be powered by the USB port. Designers simply plug into the USB port of any laptop or workstation for hassle-free development and a simple out-of-the-box experience.
It is based on the C5505 processor, the industry’s lowest power 16-bit DSP with active power consuming less than 0.15 mW/MHz and standby power less than 0.15 mW. An on-board audio codec and connectors allow developers to evaluate many features of the C5505 processor and quickly optimize complex DSP algorithms in terms of performance and power consumption across a variety of design scenarios, and an extension connector allows developers to design and directly connect to daughter cards suitable for their application.
The C5505 eZdsp USB stick development tool is available now $49, which includes a full XDS100 emulator and a target version of the CCStudio v.4 software. Special incentives are available for educators, university students and developers actively participating in TI’s online community.

Google data on spring cleaning solar panels

Google has been looking at whether it should clean its solar panels, and d'uh, finds that the efficiency rises dramatically when it does! However, there are also some interesting slides on the data they collected.

Ever since we assembled a 1.6 MW solar panel installation at our headquarters in Mountain View in 2007, we've been wondering, "Does cleaning the solar panels make them more effective?" We thought it might, but we needed to be sure. So we analyzed the mountains of data that we collect about the energy that these panels produce — after rain, after cleaning and at different times of the year.

We have two different sets of solar panels on our campus — completely flat ones installed on carports, and rooftop ones that are tilted.

Since the carport solar panels have no tilt, rain doesn't do a good job of rinsing off the dirt they collect. (Also, our carports are situated across from a sand field, which doesn't help the situation.) We cleaned these panels for the first time after they had been in operation for 15 months, and their energy output doubled overnight. When we cleaned them again eight months later, their output instantly increased by 36 percent. In fact, we found that cleaning these panels is the #1 way to maximize the energy they produce. As a result, we've added the carport solar panels to our spring cleaning checklist.

The rooftop solar panels are a different story. Our data indicates that rain does a sufficient job of cleaning the tilted solar panels. Some dirt does accumulate in the corners, but the resulting reduction in energy output is fairly small — and cleaning tilted panels does not significantly increase their energy production. So for now, we'll let Mother Nature take care of cleaning our rooftop panels.

Accumulated dirt in the corners of a rooftop solar panel

We've also been crunching numbers on dollars-and-cents; the more energy our panels produce, the sooner we'll be paid back by our solar investment. Our analysis now predicts that Google's system will pay for itself in about six and a half years, which is even better than we initially expected.

If you want to learn more about our solar study, check out these slides showing the effects that seasonality, tilt, dirt, particulate matter, rain and cleaning have on Google's solar energy output. We hope you solar panel owners out there can tailor our analysis to the specifics of your own installation to produce some extra energy of your own!