We seem to feature new ideas for methods of generating power every week on EcoGeek. Varieties of methods for harnessing energy from wind, waves, and the sun are being investigated and developed by scientists and inventors all over the globe. But many of these power sources are intermittent, compared to the steady output that is available from combustion of (most often) non-renewable fossil fuels.
One of the regular complaints from opponents of wind or solar power is that it is sporadic or unreliable. "The sun doesn't shine at night;" "The wind doesn't always blow when you need it;" and other complaints are leveled against renewable power systems. That doesn't mean they aren't useful, though. Instead, the grid needs to be better equipped to store that power when it is generated and then draw from it again when demand rises. It's part of the 21st century grid our power system will need.
Ars Technica has a story on power storage that is well worth reading. It looks at some of the theoretical options for power storage, as well as current technologies that are already in use.
MIT is definitely a hot spot on the map of green innovation. Besides making a major breakthrough in hydrolysis catalysis this past summer, MIT has delivered many good technology concepts lately, such as power-generating shock absorbers, solar race cars and even self-propelling fish farms, just to name a few. The latest MIT idea comes from its materials chemistry department, where a professor has demonstrated a new kind of battery.
A conventional battery consists of two solid metal electrodes immersed in an electrolyte that is touching them both. As they react over time, electrons travel through the electrolyte as well as through the load. This battery uses liquid electrodes instead. Three liquids are poured into a vessel – molten magnesium, molten antimony and an electrolyte. Due to their different densities, the three liquids naturally separate; the antimony settles to the bottom, the electrolyte rests in between and the magnesium sits on top.
As the battery discharges, the molten metals react and slowly ionize, dissolving into the electrolyte solution. Thus, when discharged, the battery is mostly electrolyte, with only thin layers of metal remaining. When it is recharged, the magnesium ions are reduced and the antimony ions are oxidized – which, in this case, causes both the magnesium and antimony to go from ionic to metallic form. Thus, the recharged battery once again has thick liquid metal layers and a thin electrolyte layer.
This might not be more than an interesting chemistry experiment, were it not for the fact that such a liquid battery offers numerous advantages over conventional ones. The liquid metals and molten salt (used as the electrolyte) can absorb very high electrical currents – ten times higher than the best batteries we have today, according to the MIT professor heading the project. And the design of the battery allows it to be built quickly and cheaply (the team only used magnesium and antimony for the prototype - they have found better, cheaper materials to use for real-world versions, but are keeping the details quiet).
In other words, these batteries could be ideal for solar power storage. If so, they would be welcomed with open arms – solar proponents know that the biggest thing standing in the way of large, utility-scale solar power is the question of how it can be effectively stored. We don’t yet have any really promising answers to that question. Solar power can drive hydrolysis and generate hydrogen gas to be used as fuel, but it can be inefficient. Some have proposed to pump water up hills so that it can power turbines on the way down, but if you’re short on water, that isn’t the best option. And ultracapcitors are still a little way off.
MIT, keep ‘em coming.
Via MIT Tech Review
A number of tech blogs are reporting a humorous and green-sounding new battery technology: the NoPoPo Japanese battery that can be recharged by filling it up with… urine. Sounds great, right? Free electricity! The ultimate recyclable resource! Not only that, but this battery can run on any liquid – beer, tea, juice, coffee… even water!
That’s where I stopped to think. Water? Really? How does a battery “run” on water? Every now and then a video goes around showing some garage inventor who has managed to generate energy from water, or salt water, or something like that. Every time it’s proven to be a hoax. Because you just can’t create energy out of nowhere; to quote the Simpsons, we follow the laws of thermodynamics in this household.
So then how do these batteries work? Nearly all of the posts refer to the fact that “the liquid reacts with a mix of carbon and magnesium”. They also mention the fact that the battery can only be recharged a limited number of times. But if the liquid were the fuel, why would it be limited like that?
The best explanation I found was in a comment by “retired Chemistry Professor” on the blog Hexus. He pointed out that when the liquid is introduced it allows the magnesium to oxidize, thereby generating a current. As soon as the magnesium runs out, the battery is dead. In lieu of an official explanation of the technology from the NoPoPo people, this sounds the most plausible to me.
So is there value to this battery? Maybe a little. It claims to be made of environmentally benign materials. Also, whereas a regular battery slowly dissipates its charge no matter what, maybe this one would be able to “hibernate” in between liquid injections, thereby giving you the full potential of the magnesium inside. But the battery is only rated to give you 500 mAh (milliamp hours) – as opposed to 1700-3000 mAh in a normal alkaline battery – and it’s only powerful enough to run a small device like a clock or a radio (when’s the last time you even used a portable radio?).
Moral of the story – be skeptical when someone tells you something runs on water.
The world's smallest fuel cell, measuring just 3mm x 3mm x 1mm (roughly 0.1 inches square by 0.04 inches tall), has been built by scientists at the University of Illinois Urbana-Champaign. The tiny cell is able to produce about 1 milliamp at 0.7 volts for 30 hours.
The cell is so small that it simply eliminates some of the components typically found in larger fuel cells.
"It's not practical to make a pump, a pressure sensor, and the electronics to control the system in such a small volume," says Saeed Moghaddam at the University of Illinois at Urbana-Champaign. "Even if they are magically made at that scale, their power consumption would probably exceed the power generated."
So with this fuel cell, there is no fuel tank, for example. The tiny cell gets the necessary moisture for its operation from water vapor in the air. To regulate the system, as water vapor enters the chamber and reacts to produce hydrogen, the pressure of the hydrogen closes a membrane which blocks more vapor laden air from entering until the hydrogen pressure has been reduced again.
As more tiny electronic devices are developed, providing power for them can start to become an issue. Many cell phones weigh less than the batteries that are attached to them to provide them with power. Instead of needing heavy power supplies for small electronics components, this type of very small fuel cell may play a role in providing the necessary power for tiny distributed electronics applications in the future. And, developments in these systems may also lead to new developments in fuel cell power systems to replace batteries in consumer electronics devices such as portable phones and laptop computers.
via: New Scientist Tech