Toward Tiny, Solar-powered Sensors

(Nanowerk News) The latest buzz in the information technology industry regards “the Internet of things” — the idea that vehicles, appliances, civil-engineering structures, manufacturing equipment, and even livestock would have their own embedded sensors that report information directly to networked servers, aiding with maintenance and the coordination of tasks.
Realizing that vision, however, will require extremely low-power sensors that can run for months without battery changes — or, even better, that can extract energy from the environment to recharge.
Last week, at the Symposia on VLSI Technology and Circuits, MIT researchers presented a new power converter chip that can harvest more than 80 percent of the energy trickling into it, even at the extremely low power levels characteristic of tiny solar cells. Previous experimental ultralow-power converters had efficiencies of only 40 or 50 percent.

The MIT researchers’ prototype for a chip measuring 3 millimeters by 3 millimeters. The magnified detail shows the chip’s main control circuitry, including the startup electronics; the controller that determines whether to charge the battery, power a device, or both; and the array of switches that control current flow to an external inductor coil. This active area measures just 2.2 millimeters by 1.1 millimeters.

Moreover, the researchers’ chip achieves those efficiency improvements while assuming additional responsibilities. Where its predecessors could use a solar cell to either charge a battery or directly power a device, this new chip can do both, and it can power the device directly from the battery.
All of those operations also share a single inductor — the chip’s main electrical component — which saves on circuit board space but increases the circuit complexity even further. Nonetheless, the chip’s power consumption remains low.
“We still want to have battery-charging capability, and we still want to provide a regulated output voltage,” says Dina Reda El-Damak, an MIT graduate student in electrical engineering and computer science and first author on the new paper. “We need to regulate the input to extract the maximum power, and we really want to do all these tasks with inductor sharing and see which operational mode is the best. And we want to do it without compromising the performance, at very limited input power levels — 10 nanowatts to 1 microwatt — for the Internet of things.”
The prototype chip was manufactured through the Taiwan Semiconductor Manufacturing Company’s University Shuttle Program.
Ups and downs
The circuit’s chief function is to regulate the voltages between the solar cell, the battery, and the device the cell is powering. If the battery operates for too long at a voltage that’s either too high or too low, for instance, its chemical reactants break down, and it loses the ability to hold a charge.
To control the current flow across their chip, El-Damak and her advisor, Anantha Chandrakasan, the Joseph F. and Nancy P. Keithley Professor in Electrical Engineering, use an inductor, which is a wire wound into a coil. When a current passes through an inductor, it generates a magnetic field, which in turn resists any change in the current.
Throwing switches in the inductor’s path causes it to alternately charge and discharge, so that the current flowing through it continuously ramps up and then drops back down to zero. Keeping a lid on the current improves the circuit’s efficiency, since the rate at which it dissipates energy as heat is proportional to the square of the current.
Once the current drops to zero, however, the switches in the inductor’s path need to be thrown immediately; otherwise, current could begin to flow through the circuit in the wrong direction, which would drastically diminish its efficiency. The complication is that the rate at which the current rises and falls depends on the voltage generated by the solar cell, which is highly variable. So the timing of the switch throws has to vary, too.
Electric hourglass
To control the switches’ timing, El-Damak and Chandrakasan use an electrical component called a capacitor, which can store electrical charge. The higher the current, the more rapidly the capacitor fills. When it’s full, the circuit stops charging the inductor.
The rate at which the current drops off, however, depends on the output voltage, whose regulation is the very purpose of the chip. Since that voltage is fixed, the variation in timing has to come from variation in capacitance. El-Damak and Chandrakasan thus equip their chip with a bank of capacitors of different sizes. As the current drops, it charges a subset of those capacitors, whose selection is determined by the solar cell’s voltage. Once again, when the capacitor fills, the switches in the inductor’s path are flipped.
“In this technology space, there’s usually a trend to lower efficiency as the power gets lower, because there’s a fixed amount of energy that’s consumed by doing the work,” says Brett Miwa, who leads a power conversion development project as a fellow at the chip manufacturer Maxim Integrated. “If you’re only coming in with a small amount, it’s hard to get most of it out, because you lose more as a percentage. [El-Damak’s] design is unusually efficient for how low a power level she’s at.”
“One of the things that’s most notable about it is that it’s really a fairly complete system,” he adds. “It’s really kind of a full system-on-a chip for power management. And that makes it a little more complicated, a little bit larger, and a little bit more comprehensive than some of the other designs that might be reported in the literature. So for her to still achieve these high-performance specs in a much more sophisticated system is also noteworthy.”



Cisco signs solar power deal for San Jose headquarters

By Pete Carey

Photo: Cisco headquarters (Paul Sakuma, Associated Press)

Cisco Systems announced plans Tuesday to develop a 20-megawatt solar power facility in the Sonoran Desert near the California-Arizona border that will supply power to its San Jose headquarters.

The deal requires little upfront money from Cisco. NRG Renew, the solar arm of independent power producer NRG Energy, will build the facility at a vacant 153-acre parcel at its Blythe location the NRG has been developing since 2010. Cisco agreed to purchase power from the solar farm for 20 years.

Power will start flowing at the end of 2016.

Ali Ahmed, Cisco’s global energy and sustainability chief, said the plan will further Cisco’s goal of using renewable sources for at least 25 percent of its needs by 2017.

Silicon Valley companies — especially those with big, power-hungry data centers — have embraced green energy in the past few years. Apple recently announced plans to power its Cupertino headquarters building, now under construction, with solar energy from a solar farm operated by First Solar in Cholame, in a remote part of Monterey County. Google signed a 20-year agreement with Florida-based NextEra to buy nearly 43 megawatts of electricity from an Altamont Pass wind farm beginning next year.

Cisco already has about 2 megawatts of solar power for some of its facilities around the U.S., including a new system in Boxborough, Mass. The company said it is focusing on its engineering labs, which it described as “the company’s largest consumers of energy and greatest source of greenhouse gas emissions.”

NRG said its Blythe II solar farm is in a location where average temperatures are 90 degrees or higher. It said the new installation’s 20 megawatts will provide enough electricity to power 14,000 homes and will prevent more than 100,000 metric tons of carbon dioxide from entering the atmosphere, a reduction that it said is equivalent to removing 21,000 cars from the road.

NRG is a major independent power producer with about 3 million retail customers nationwide.


Save Energy and Save Money – A Definitive Guide

When it comes to cheaper domestic energy solutions, the homeowner is often drawn towards money saving tips, as well as hints on how to use energy smarter.
However, in the past, this has meant reading in the dark and not cooking. The good news is that this in no longer the case! With a combination of change in habits, short and long term investments in your home, you could soon be enjoying lower energy bills.

Update ‘The Old Boiler’
Possibly one of the most expensive pieces of kit in any household is the boiler, and not just in terms of purchase cost. The Internet is awash with hints and tips on saving energy and one that appears time and time again, is the need to have a modern, sophisticated boiler, with a sophisticated thermostat system.
Prices of boilers are no longer as eye watering as you think but still, when the household budget is tight, forking out £400+ can be a big ask. However, the running costs of a modern boiler are far lower and you will reach the other side of winter, toasty warm but with a lower energy bill.

Investing in an all-singing, all dancing boiler and thermostat system is all well and good but if the warmth but, if the heat is leaking out of ill-fitted, single pane window and gaps under the front and back doors any gain is literally being lost. Think insulation before you take on a new boiler.
Quick tip – turn the heat down by 1° to save £55 a year. That said, turning it down to a more ambient temperature and layering on the woolly cardigan is not such a bad idea either.

The new system – only when you need it
Older boiler systems and thermostats operated on a clock system. In some cases, this was not a bad thing. You could have the house lovely and warm, waiting for you when you got in from, the kids from school. You could set it for coming on in the morning so no one was cold when they left their bed.
Except, the house may not have been cold at these points and like many other households, you probably switched it off and opened a window. The newer, more modern thermostat systems monitor the temperature in the house.
You set the optimum temperature at which you think you need it on. For example, if the temperature in the house falls to 15°, the boiler will kick in and it will continue to be active until the desired temperature is reached, such as 18°. It will do this at any time of night or day, perfect in so many ways.
But, if you think you could be heating an empty house during the day, then use the drop button on the system that tells the boiler you are not home, and that the lowest temperature has dropped dramatically. It also has ‘frost protection’, so you never have a truly cold house.

Quick tip – become super-savvy by installing a Vortex energy saver in the boiler that through a simple, yet effective scientific principle takes out most of the oxygen in the water, saving the system from corrosion. A super idea that see an extra 30% saving.

Look after the boiler and the radiators to get the most out of your system and keep it in tip top shape for longer. Just like a car, there are moving parts that can malfunction and also need some TLC every now and then. Don’t wait for it to break down but get the boiler serviced regularly. Flushing the radiator system every now and then can be expensive, but worth it in the longer term.
Add a little extra, and save a lot more – the exhaust gas from your boiler has heat in it; this is why you get the cloud of light coloured ‘steam’ from the flue. This heat can be recycled back in to the system and used to heat water, saving you another 33%. Most boilers can be fitted with a Passive Flue Gas Heat Recovery Device.

Shower rather than wallow in the bath
We all likes and dislikes; there is nothing better than a soak in the tub after a long, stressful day. However, is you are a daily bath taker you could be paying for this in terms of both increased energy consumption and more water.
‘Experts’ suggest that a 4 minute shower should be the norm – although teenagers struggle with this concept – but a daily bath over the year uses 13,000 litres of water. Far more than the average daily shower over a year.
Saving money on your energy bills is not hard. There are many hints, tips and additional pieces of equipment that can make small savings but, when added together, make a huge financial impact.

Solar-powered hydrogen generation using two of the most abundant elements on Earth

By Colin Jeffrey

By smoothing the surface of hematite, a team of researchers achieved “unassisted” water splitting using the abundant rust-like mineral hermatite and silicon to capture and store solar energy within hydrogen gas (Credit: Nature Communications)

One potential clean energy future requires an economical, efficient, and relatively simple way to generate copious amounts of hydrogen for use in fuel-cells and hydrogen-powered vehicles. Often achieved by using electricity to split water molecules into hydrogen and oxygen, the ideal method would be to mine hydrogen from water using electricity generated directly from sunlight without the addition of any external power source. Hematite – the mineral form of iron – used in conjunction with silicon has shown some promise in this area, but low conversion efficiencies have slowed research. Now scientists have discovered a way to make great improvements, giving hope to using two of the most abundant elements on earth to efficiently produce hydrogen.

Hematite holds potential for use in low-power photoelectrochemical water splitting (where energy, in the form of light, is the input and chemical energy is the output) to release hydrogen due to its low turn-on voltage of less than 0.3 volts when exposed to sunlight. Unfortunately, that voltage is too low to initiate water-splitting so a number of improvements to the surface of hematite have been sought to improve current flow.

In this vein, researchers from Boston College, UC Berkeley, and China’s University of Science and Technology have hit upon the technique of “re-growing” the hematite, so that a smoother surface is obtained along with a higher energy yield. In fact, this new version has doubled the electrical output, and moved one step closer to enabling practical, large-scale energy-harvesting and hydrogen generation.

“By simply smoothing the surface characteristics of hematite, this close cousin of rust can be improved to couple with silicon, which is derived from sand, to achieve complete water splitting for solar hydrogen generation,” said Boston College associate professor of chemistry Dunwei Wang. “This unassisted water splitting, which is very rare, does not require expensive or scarce resources.”

Working on previous work that realized gains in the photoelectrochemical turn-on voltage from the use of smooth surface coatings, the team re-assessed the hematite surface structure by employing a synchrotron particle accelerator at the Lawrence Berkeley National Laboratory. Concentrating on massaging the hematite’s surface deficiencies to see if this would result in improvements, the researchers used physical vapor deposition to layer hematite onto a borosilicate glass substrate and create a photoanode. They then baked the devices to produce a thin, even film of iron oxide across their surfaces.

Subsequent tests of this new amalgam resulted in an immediate improvement in turn-on voltage, and a substantial increase in photovoltage from 0.24 volts to 0.80 volts. Whilst this new hydrogen harvesting process only realized an efficiency of 0.91 percent, it is the very first time that the combination of hematite and amorphous silicon has been shown to produce any meaningful efficiencies of conversion at all.

As a result, this research has shown that progress has been made towards the possibility of producing photoelectrochemical energy harvesting that is totally self-sufficient, uses abundantly available materials, and is easy to produce.

“This offers new hope that efficient and inexpensive solar fuel production by readily available natural resources is within reach,” said Wang. “Getting there will contribute to a sustainable future powered by renewable energy.”


Solar-powered Charging Station benefits Students, Environment

It was another sunny day on campus when Jawad Khalid, a civil engineering graduate student, noticed his phone needed to charge.

He had forgotten his charger, so Khalid walked up to a charging station in front of the Philip Guthrie Hoffman Hall. He switched charging plugs a couple of times, but finally stuck with one after he lifted his glasses to ensure his phone was charging.

This charging station is not like the ones seen at airports – this one is free and uses solar power energy.

The solar-powered charging station is brought to campus in collaboration with NRG Energy and UH. | Sara Samora/The Cougar

The panels take the energy that comes in the form of light and converts it into electricity, which UH Chief Energy Officer Ramanan Krishnamoorti said is the same energy one finds in an electrical power outlet.

“All of (the) energy we get on earth comes from the sun in some way or another,” Krishnamoorti said. “(The question is) can you capture that in some effective way?”

The charging station is not the first of its kind on campus. In 2011, a solar array was installed on the central power plant roof. The solar arrays powers 25 percent of the office space for the plant.

Krishnamoorti said the idea for the solar charging station was only recent, when NRG Energy approached school officials with a possibility of coordinating a solar charger for the university as well as having it available for the masses.

“We decided to find a way to install it in a matter that it would be consistent with as large an audience as possible,” Krishnamoorti said. “Energy is part of the environment and (because of) the distinction between the energy and the environment, we felt that we are (celebrating) doing both promoting the idea of using energy, but also bring it in a way that’s consistent in a sustainable way.”

Krishnamoorti said one of the ideas for the future is to install solar power charging stations for vehicles. He said, however, that they are looking for strategic opportunities.

“We don’t want to do it just for the sake of doing it,” Krishnamoorti said.

Khalid said that solar energy is a renewable source, and that making more stations, such as the one in front of PGH, will make students aware about the alternate source of energy.

“It also helps for them to not only depend on electricity,” Khalid said. “So we should look at the source of energy; it helps the environment, and it helps others as well.”