Energywise iconEnergywise

Taiwanese Researchers Report Progress Towards a Magnesium-ion Battery

Back in January, when lithium-ion batteries powering the electronics in the Boeing Dreamliner aircraft caught fire, the news came as a shock to many. The culprit was the lithium in these rechargeable batteries. It easily ignites when, for example, oxygen is released inside the battery. Batteries made with magnesium are less flammable because a protective layer of magnesium oxide covers the metal. However, it’s not just the lower likelihood that they could turn into tinder boxes that makes magnesium batteries interesting as an alternative to their lithium counterparts. The magnesium ions in the electrolyte also carry a double positive charge, increasing the amount of charge that can be stored by a battery of a given size. Manufacturers of electrically powered cars are especially interested in a workable magnesium-ion battery, but a commercially viable formulation has eluded researchers up to now.

Now a research team led by Fei-Yi Hung, Chun-Shing Lu and Li-Huei Chen from the Department of Materials Science and Engineering at National Cheng Kung University (NCKU) in Tainan, Taiwan, claims that it has developed "next-generation" magnesium batteries that could replace lithium batteries. “We control the reduction-oxidation effects by magnesium membrane electrodes and magnesium powder electrodes technology to increase the magnesium battery prototype’s stability.” Hung is quoted in EnergyTrends, a Web publication based in Taiwan and China. Hung adds that, “A magnesium battery’s capacity is 8 to 12 times higher than a lithium battery. In addition, its charge-discharge efficiency is 5 times higher.”

One of the lingering concerns that troubled engineers looking to design a magnesium battery has been fears over the high reactivity of magnesium. David Prendergast, and Liwen Wan, both researchers at Lawrence Berkeley National Laboratory in California, published in October the results of supercomputer simulations showing that the reactivity of magnesium is not a hindrance at all. The existing misconception, that magnesium ions would form complex coordination compounds that would hinder the motion of the ions through the electrolyte, proved wrong. Their simulations indicated that the ions formed only four coordination bonds instead of six, making a magnesium-ion coordination complex much smaller and more efficient than was expected.

Their finding should encourage the Taiwanese team and other research groups, which should lead to a diversity of approaches, according to Prendergast. One of the remaining problems is working out the chemistry for solutions that have cathodes, anodes, and electrolytes which are mutually compatible. "The hope is that we can come up with a set of prototypes that we can at least propose and then vet them against each other, and try to come up with a working combination," says Prendergast.

Is Iceland Poised to Become a Data Center Paradise?

Past the bullet- and blast-resistant security station, through a two-door man-trap or two, and inside a few card-plus-passcode doorways at Verne Global’s facility one can finally see one of the two main things that make Iceland an attractive place to put data centers: holes in the walls. More accurately, simple vented walls that allow the outside air to come in, pass through some filters and laser monitoring systems, and on into the rooms full of server racks. Data centers need massive amounts of cooling power, and Iceland’s often chilly air can do the trick.

Read More

EU Climate Summit Commits to 2030 Carbon Cuts

European leaders wrapped up a two-day climate summit in Brussels last week with a deal to cut the European Union's total greenhouse gas emissions to 40 percent below 1990 levels. This would continue a downward trend – the EU is already on track to meet a 20 percent reduction from 1990 levels by 2020 – but the ageement is weak relative to Europe's prior ambitions to confront climate change.  

Investors in green tech pushed agressively for the deal, seeking a longterm signal that the European market will continue to reward advances in energy efficiency and low-carbon energy production. The deal is also a shot in the arm for the Paris global climate talks, scheduled for December 2015, which will seek to achieve the decisive binding global targets for greenhouse gas reductions that failed to emerge from the 2009 Cophenhagen climate talks.

Read More

Power Production Decentralizes in Mexico

Over the last twenty years, Mexico's electricity sector has shifted from being almost 100 percent state-owned and centralized to about one quarter privately generated. This summer, the Mexican government signed into law energy and electricity grid reforms that will accelerate the decentralization of its electricity production (See “Mexico Opens Its Grid to Competition.”). By the end of this year, a new agency should have a regulatory map available for power producers large and small, said Edgar López, renewable energies director at Mexico's Energy Regulatory Commission (CRE) at a conference in Mexico City last month.

Read More

Internet-Exposed Energy Control Systems Abound

Two-and-a-half years ago researchers at Chicago-based cyber security firm Infracritical set out to measure how many industrial control systems are openly exposed to the Internet. Their disquieting findings are up for discussion today at the 2014 ICS Cyber Security Conference in Atlanta.

Infracritical remotely identified over 2.2 million unique IP addresses linked to industrial control systems at energy-related sites including electrical substations, wind farms, and water purification plants. And they were still logging an average of 2,000-3,000 new addresses per day when they closed the count in January 2014.

Read More

Can Organic Solar Cells Reach Old Age?

Although organic photovoltaic cells are less efficient than silicon-based ones, experts expect their to one day be a big market for them. That’s because they are cheap to manufacture, flexible, and light-weight. However, there is a big obstacle to their wide-scale use: their lifetime is limited by oxygen and by ultraviolet radiation.

There’s hope, according to Monica Lira-Cantu, an engineer investigating organic solar photovoltaics at the Catelan Institute of Nanoscience and Nanotechnology in Bellaterra, Spain. She was one of the three organizers of ISOS-7 International Summit on OPV Stability (ISOS) held in Barcelona, on 6-8 October.

Read More

A Thermoelectric Generator That Runs on Exhaust Fumes

Alphabet Energy has designed a generator that uses no fuel. Instead, it uses racks of thermoelectric modules to convert the waste heat from industrial machines into electricity.

The Hayward-California based startup earlier this week introduced the E1, claiming that it is the first large-scale commercial thermoelectric generator on the market. The company is already taking orders from mining companies that have large amounts of waste heat and no use for it.

To set it up, a mining company needs to connect a flexible tube to direct exhaust from an engine into Alphabet Energy’s generator, which is packaged in a shipping container. The gases flow through 32 racks of thermoelectric modules that produce a direct current, which is inverted to alternating current and fed to the site’s breaker. A radiator cools the modules because they need a difference in temperature to produce current.

Read More

India Plans First Offshore Wind Farm, Continued Coal Expansion

The energy picture for the world's biggest democracy will always be a bit muddy. All in the space of a week, India announced plans for its first offshore wind farm, promised an enormous expansion of solar power and other renewables, seen its new Prime Minister Narendra Modi have supposedly productive talks with President Obama on climate change, and stood defiantly behind plans to also rapidly build up coal-fired power infrastructure. Providing electricity for 1.4 billion people—300 million of whom currently lack any access at all—is more than a bit complicated.

First, the good news: the government of India announced that a memorandum of understanding has been signed toward building the first offshore wind farm in the country, a 100-megawatt "demonstration" project off the coast of the northwestern state of Gujarat. Construction of such a plant is still a ways off, with feasibility studies and other preliminary steps standing in the way. But Piyush Goyal, the Indian minister for power, coal, and new and renewable energy, pointed out that with 12,230 kilometers (7,600 miles) of coastline the opportunities for rapidly scaling up offshore wind are huge.

Read More

Rooftop Solar’s Threat to Utilities by the Numbers

The rise of rooftop solar has resulted in a catchy phrase—the “utility death spiral”. It's the idea that utilities will be put out of business by distributed energy. A Lawrence Berkeley National Laboratory study confirms utilities in the United States do have reason to worry but finds that changes to regulations could make solar and utilities friends, rather than foes.

Read More

Cheap Solar Cells Offer Hydrogen Hope

Perovskite solar cells have made remarkable progress in the past few years, and the rising efficiency of the low-cost devices has begun to rival conventional silicon cells. Now perovskite photovoltaics have been used to split water to produce hydrogen, offering a promising route to the clean-burning fuel.

Hydrogen is very slowly gaining ground as a transportation fuel, but it has a dirty secret: most of the world’s supply of the gas is made via reactions with methane and steam at high temperatures, releasing the greenhouse gas carbon dioxide in the process. Developing a less-polluting source of hydrogen could help to bolster its green credentials and speed its adoption. Using electricity from renewable sources to split water by electrolysis, however, is far too expensive today.

That’s partly because it takes a voltage of at least 1.23 V to split water, with commercial systems running at about 1.8 V to 2.0 V. Conventional silicon or cadmium-telluride solar cells cannot deliver that voltage, because their bandgap is not wide enough. So three or four cells must be connected in series to reach the electrolysis threshold. At large scales, such systems are therefore uneconomical.

Enter the clean energy savior du jour: perovskites, which have a wide band gap, enabling each cell to produce a relatively beefy voltage of up to 1.5 V. What’s more, they rely on a cheap and easy-to-manufacture light-absorbing layer such as methyl ammonium lead iodide. (The cell’s name refers to this material’s crystal structure). And since 2009, improvements in the chemistry and design of the cells’ various  layers have pushed their efficiency from just 3.8 percent to a whopping 17.9 percent, with some labs reporting unconfirmed results up to 19 percent.

Michael Grätzel at the Swiss Federal Institute of Technology in Lausanne (EPFL), Switzerland, one of the pioneers of perovskite cells, has now shown, along with his colleagues, that using just two cells in parallel is enough to start the hydrogen fizzing out of water. Their research was published this week in Science.

His team connected the cells to cheap, efficient electrocatalysts of their own design that use the solar power to split water. One electrode delivers electrons to water, splitting the molecules into hydrogen gas and hydroxide anions. The other electrode uses those hydroxide anions to produce oxygen gas and release more electrons back to the circuit.

Previous electrocatalysts like platinum and iridium are cursed by high costs, and cheaper materials that contain cobalt or molybdenum are finicky. Electrolysis systems generally need the water to be spiced with acid or base to help the current flow, but here's the rub: Electrocatalysts that are good at generating hydrogen are generally only stable if the water is acidic, while those adept at generating oxygen prefer basic conditions.

Grätzel’s system builds on previous work with an electrode made of  iron and nickel. His team coated porous nickel “foam” with iron and nickel hydroxide, and tested the electrodes in a basic solution of sodium hydroxide. They found that the electrodes generated oxygen more effectively than a platinum-nickel electrode, and were almost as good at generating hydrogen— quite a surprise, given that this reaction usually runs far more slowly in basic solution. “The real advance is being able to use this less-than-ideal catalyst, because the voltage of the perovskite cell is so high,” says Thomas Hamann at Michigan State University in East Lansing, who wrote a commentary on the work in Science.

In the researchers’ prototype system, a pair of perovskite cells converted light into electricity with an efficiency of 15.7 percent, and generated a healthy 2.0 V. That was more than enough to make hydrogen and oxygen stream from the electrodes. Measuring the rate of gas production, Grätzel’s team calculated that the overall solar-to-hydrogen conversion efficiency was 12.3 percent. That matches the performance of a gallium-indium-phosphide/gallium-arsenide tandem cell linked to platinum catalytic electrodes—but at a much lower cost, says Hamann. Indeed, of all similar systems that use cheap, abundant materials, nothing has topped 10 percent efficiency, he adds.

Loading the player...
Video: EPFL

As perovskite cells continue to improve, Grätzel’s team reckons that the overall solar-to-hydrogen conversion efficiency could rise to 15 percent. That’s in line with the trajectory of the US Department of Energy's goals for solar hydrogen production: 15 percent efficiency by 2015, 20 percent efficiency by 2020, and significant cuts to the cost of the system’s components.

If those targets could be met, hydrogen might also be used to bank excess energy generated by solar power or wind turbines and be deployed when these facilities idle or when demand surges. In theory, storing energy in the form of free hydrogen could be more convenient than pumped hydropower, and a lot cheaper than batteries.

There is one major drawback: Grätzel’s perovskite cells degraded after only a few hours. “Stability of the perovskites is a known issue,” says Jingshan Luo, part of Grätzel’s team at EPFL. But he points out that other researchers have recently shown that perovskite solar cells can be made much more resistant to moisture or heat, and in some cases, made to operate for more than 1000 hours without any loss in performance.

If the stability issues can be conquered, Hamann suggests that there are other ways to improve the performance of the system. Rather than using two perovskite cells, one of them could be placed on top of a silicon cell. Since silicon has a smaller band gap, it would absorb light from the red end of the spectrum that currently streams through the semi-transparent perovskite cell. This could halve the area of solar panels needed, increase the overall efficiency of the solar energy conversion, and boost hydrogen production. “That’s exactly what I’m doing now!” says Luo excitedly.

This strategy comes with a cost, however: It would lower the overall voltage of the tandem cell, requiring a more efficient hydrogen-evolving electrode. Luo is working on this, too, and says he and his colleagues are making good progress: “Most perovskite groups are focused on the cells, and they’re not experts in solar fuel generation,” he says. “We’re doing research on both sides.”

Advertisement

Newsletter Sign Up

Sign up for the EnergyWise newsletter and get biweekly news on the power & energy industry, green technology, and conservation delivered directly to your inbox.

Advertisement
Load More