So you’re telling me that my electric car’s battery is in the paint?

What comes to mind when you picture a battery? The familiar Duracell Coppertop AA battery? A clunky  automotive battery? The small rectangular battery in your cell phone? Researchers at Rice University are reinventing the concept of batteries and battery packaging by creating a lithium-ion battery with spray paint. That’s right, your local neighborhood hoodlum taggers can now be more energy forward than you sitting at home watching Cops.

A team of researchers from Rice University have demonstrated in a paper in Nature Scientific Reports that special “spray paints” can be used sequentially to build up the layers needed to form a lithium-ion battery. A spray-on battery could be used on a variety of materials, both rigid and flexible. They point out that the technology could be coupled to energy conversion devices such as solar cells.

Simply put, a lithium-ion battery is created by tightly layering cathodes and anodes like in the image shown below. The researchers at Rice University replicate this cylindrical design in a customizable form using the spray coatings that they developed. They applied the battery painting process to a variety of materials including stainless steel, glass, ceramic tile, and flexible polymer sheets. An SEM image of a cross section of the battery is shown below. Each of the spray painted batteries performed as a typical battery. They even applied the spray paint to a coffee mug to spell out the name of their Alma mater while also storing energy. They added that more complicated surface geometries could be possible using different spray nozzle designs that are tailored to the different viscous properties of the paints.

The are a few drawbacks to a spray painted lithium-ion battery. For one, the materials are highly toxic, corrosive, and flammable, hence why they are always tightly packaged and hidden away in their conventional form. Secondly, the batteries are highly sensitive to oxygen and moisture. This sensitivity currently restricts their widespread use because they still have to be packaged like their conventional brethren, reducing their novel promise. A spray painted battery is shown below on a glazed ceramic tile alongside its final packaged form. One of the researchers’ next steps is to develop a sealing layer to protect the batteries from these elements. Because who wants to paint their electric vehicle with a new battery but then have the painter tell them that they always have to keep the car cover on.

Typical lithium-ion battery construction.

Conventional and spray painted lithium-ion batteries.

SEM image of spray painted lithium-ion battery cross section.

Glazed ceramic tile with spray painted battery prior to packaging (left) and post-packaging (right)

 

Salinity gradient power rising as a realistic renewable energy source

Amazon River estuary
http://images.gizmag.com/gallery_lrg/11206_12030952855.jpg

Estuaries are the locations where river water mixes with seawater. They are found along coastlines throughout the world, but what most people don’t realize is the significant potential to produce clean energy from these mixing water streams. The salinity gradient between the two streams of water contains a large amount of osmotic power, which can be thought of as the available energy (or chemical potential) from the differences in salt concentration between the fresh water and seawater. The enormous amounts of energy released where freshwater and seawater meet “can be utilized for the generation of power through osmosis”, which is “defined as the transport of water through a semi-permeable membrane.” [1]

The idea of obtaining energy from osmosis, or salinity gradient power, has been studied for decades, but in early 2009 two teams were racing to be the first to build a working prototype power plant making salinity gradient power a feasible method for renewable energy generation. Both teams have been working on the development and implementation of a membrane based osmotic process, but their approaches for generating the electricity are very different [2]. Westus (The Centre for Sustainable Water Technology), located in the Netherlands, is focusing on the Reverse Electrodialysis (RED) method to produce electricity. They claim that they will utilize fresh water from the Rhine river and saltwater from the North Sea to construct a type of battery by employing two membranes permeable to ions, but not to water. Utilizing the saltwater, one membrane will allow the passage of positively charged sodium ions into a stream of fresh water and the other membrane will allow the passage of negatively charged chloride ions into another channel of freshwater. The separated charged particles with electrodes placed in both streams makes up the chemical battery, which directly produces electricity. [2] Statkraft, a leading renewable energy group located in Norway, is focusing on Pressure Retarded Osmosis (PRO) as their method to extract electricity from salinity gradients. This method utilizes a membrane, permeable to water, to draw fresh water into the concentrated salt water, thus increasing the pressure in the salt water chamber. The resulting pressure can then be used to drive a turbine to produce electricity. In November of 2009, Statkraft opened the world’s first prototype osmotic power plant in Tofte Norway. [3] This facility had a limited production capacity (of around 4 kW) and is mainly used for testing and validation of data, hopefully leading to the construction of a large commercial power plant by 2015.

Statkraft osmotic power prototype
http://images.gizmag.com/gallery_lrg/osmotic-2.jpg

While the idea of harvesting free energy from estuaries and salinity gradients may seem like a flawless idea, it comes with both pros and cons. On one side, the technology is considered “as green as it gets”, with the only waste product being brackish water, which flows into the sea mixing with the sea water [2].  It is a constantly flowing source of renewable energy, unlike the intermittent energy provided by sources such as solar or wind power. It can also easily be combined with existing power plants and industries and can be built underground, thus reducing costs and visual pollution [2]. On the other side, the membrane technology still has a long way to go. The membranes are prone to bio-fouling from algae and silt, which reduce the membrane’s lifetime and efficiency. Salinity gradient power is mainly suitable only for places where there is an abundant supply of freshwater meeting saltwater, which clearly favors countries with a large coastline [2]. Also, the environmental impact and environmental policy should be considered for future plants of this type. First off, there are many species of aquatic life that are adapted to survive in waters with a specific range of salinity concentrations, and these power plants could affect the salinity of an area of water. It has been found that large salinity changes in aquatic environments can result in low densities of plants and animals [4]. Then one must consider the environmental policy and impact of structures that intake such large volumes of river water and sea water. These power plants must conform to strict construction permits and environmental regulations.

While many issues dealing with the viability of salinity gradient power as a renewable energy source are still being addressed, advancements in the technology are constantly being made. In June of 2012, Statkraft’s head of osmotic power said “We see that the development of technology is accelerating and that an industry is emerging. The membranes we are testing at Tofte this summer are ten times more efficient than the ones we installed during the opening of the prototype in the autumn of 2009” [5]. Earlier this year, researchers discovered a new more efficient way to harness osmotic power utilizing Boron nitride nano tubes [6]. They claim that a 1 meter-squared membrane using this technology could have the same 4 kW capacity as the whole Statkraft prototype power plant. This experimental device, which is three orders of magnitude more efficient than the current system, could significantly enhance the commercial viability of salinity gradient power as a realistic source of energy [6]. While the ultimate future of salinity gradient power is unknown, it has the potential to be one of the prominent renewable energy sources on the planet.

[1] http://www.statkraft.com/energy-sources/osmotic-power/

[2] http://www.gizmag.com/salinity-power-renewable-energy-osmosis/11206/

[3] http://www.gizmag.com/statkraft-osmotic-power/13451/

[4] Montague, C., Ley, J. A Possible Effect of Salinity Fluctuation on Abundance of Benthic Vegetation and Associated Fauna in Northeastern Florida Bay. Estuaries and Coasts. 1993. Springer New York. Vol. 15 No. 4. Pg. 703-717

[5] http://www.statkraft.com/presscentre/news/statkraft-considering-osmotic-power-pilot-facility-at%20sunndalsora.aspx

[6] http://www.gizmag.com/osmotic-salinity-gradient-power-nanotubes/26623/

New Future for Paper? Think Energy Storage Devices

The coming years will see more and more renewable sources, plug in electric vehicles, and even more electronic devices requiring energy storage. All these require an inexpensive , light, scaleable, and efficient energy storage. Energy storage is especially critical to further development of some intermittent renewables like wind and solar. From the policy standpoint, having reliable and inexpensive energy storage can make it easier to achieve renewable portfolio standards, help with electricity peak demands by offsetting them, or make electric vehicles more accessible. Well, paper just may be the answer. 

Recently, scientists at Stanford coated office paper with nanotubes and nanowires to make it conducting. Moreover, they produced lightweight, flexible battery and supercapacitor (high-energy density capacitor). The discovery was unexpected as the researchers substituted paper for plastics in their previous research as a base-layer for the coating [1]. More porous paper holds this special “ink” made with carbon nanotubes better, making for a more durable battery and capacitors. 

The device is made from an off-the-shelf office paper. The paper is coated with carbon nanotube “ink”. Because of its porosity and good absorbance, the ink rheology is not very important and nanotubes bind well to it. The Proceedings of National Academy of Sciences paper [2] reports a resistance of 1 Ω (Ohm)/sq (per square). This is comparable to a resistance of a 100W light bulb (its metal filament) and not very different from an internal resistance of a regular AA alkaline battery. This paper can be folded, crumpled or even dipped in acid and it still retains its unique properties. Professor Yi Cui, said that one day, he could use a brush to paint his walls with an energy storage device (energy-storing wallpaper, anyone?) [2,4]. 

“]”]

Conducting paper rolled into a tube, Ref. 3

Conducting paper rolled into a tube, Ref. [3] 

Paper for Supercapacitors 

For comparison, a 50nm layer of gold (very good conductor) deposited on a sheet of standard Xerox paper had resistance of 7 Ω (Ohms)/sq (it was 1Ω for the coated paper). By coating both sides of paper with the carbon nanotube ink, the researchers created a supercapacitor with capacity of 200F/g (Farad per gram) in sulfuric acid electrolyte. This capacity was not severely diminished even under high current loadings of 40A/g. The gold-based supercapacitors made in a similar fashion had about 4-5 times lower capacity. Ultimately, the supercapacitor performed well even at 40,000 cycles with capacitance losses less than 3%. In MIT Technology Review article [5], Nicholas Kotov, professor of chemical engineering at the University of Michigan, says that the dipping method to make the supercapacitors is “simple and nice”. 

Paper for Batteries 

Because a large weight of batteries, up to 20% is due to heavy metallic current collectors, the paper can also be used in batteries to reduce weight while still maintaining reasonable resistance. Thus a higher gravimetric energy density can be accomplished [1].  Such battery proof of concepts made by the Stanford group achieved over 500 cycle times with high capacity retention. Paper was stable in the electrolyte over the period of 3.5 months and the battery showed only small self-discharge. 

Below is a video from Dr. Cui’s group at Stanford showing how simple it is to make this paper (of course, the “secret sauce” of the nanotube ink is not revealed) 

Nanotubes + ink + paper = instant battery

What I personally like about this technology is that is seems “ready to go”, or pretty close to commercialization. Who knows, in a strange twist of fate, maybe in a year or two, our electronic readers such as kindles and iPads will rely on paper they replaced for their energy storage. 

References: 

[1] Paper Battery Shows Promise for Grid, Vehicle Energy Storage
http://www.nytimes.com/gwire/2009/12/08/08greenwire-paper-battery-shows-promise-for-grid-vehicle-e-59107.html

[2] Hu, L., Choi, J.W., Yang, Y., Jeong, S., La Mantia, F., Cui, L., Cui, Y., 2009, “Highly Conductive Paper for Energy-Storage Devices,” Proceedings of National Academy of Sciences
http://www.pnas.org/content/106/51/21490.full.pdf+html?sid=502de90b-f1a2-49d3-8c4f-12c052917c89

[3] “Battery Made of Paper Charges Up,” BBC News, Tuesday, December 8, 2009, 16:38 GMT
http://news.bbc.co.uk/2/hi/technology/8401566.stm

[4] “Making Powerful, Lightweight Batteries From Nothing But Nanotube Ink and Paper” Popular Science, Clay Dillow, Posted 12.08.2009 at 11:15 am
http://www.popsci.com/science/article/2009-12/making-powerful-lightweight-batteries-nothing-nanotube-ink-and-paper

[5] “Batteries Made from Regular Paper”, MIT Technology Review, Katherine Bourzac, December 8, 2009
http://www.technologyreview.com/energy/24097/?a=f

Small Nuclear, Coming Soon

No new nuclear power plants have been constructed in the US since the 1980s. Despite this, nuclear energy continues to be touted as a critical element of reducing carbon emissions. This blog has several excited posts on nuclear energy, including  President Obama’s  announcing a tripling of federal guarantees for new plant financing and a recap of Bill Gates’ comments at the TED conference.  Several companies are positioning themselves to market smaller, self contained, standardized and portable reactors that, if the nuclear electricity market heats up, could also help meet an increase in demand through modularization.

The technology is not new,  but if taking the form of smaller battery-style reactors, can match some elements that that larger plants struggle with.  A partial list of the  obstacles that small battery style reactors could help overcome include:

• huge financing amounts that prohibit new plants or plant expansion
• deep regulatory hurdles
• the perennially low priority problem of where to store waste
• ample amounts of coolant, typically another scarce resource – water
  
• and lingering fear of accidents that lead to local or even national NIMBYism

Considering the difficulty of financing a nuclear reactor, take the example of the recent decision by the San Antonio utility’s consideration of the South Texas Project’s (STP) planned expansion. San Antonio has some of the cheapest rates of electricity for a large city, in large part to their current share of the STP plant and its cheap per kWh rates, which lead a number of electricity intense employers and manufacturers to expand or open new facilities like data centers there. For a number of years San Antonio was interested in expanding that capacity, but eventually cost escalation and the issue of financing such a large amount at once became more than that utility could bear. So they lowered their commitment share on the expansion from 50% to 7.6%. A smaller reactor could pose more manageable for the utility to finance, at a fraction of the cost, and could therefore be more acceptable.

Small, automated, self-contained and modular systems manufactured in a licensed plant (that has manufactured nuclear submarine powerplants for decades, for example) may more readily pass the onerous and frequently changing regulatory structure for nuclear power, another costly obstacle.

Self contained reactors under development are designed with built in lifespans of 30 to 60 years, with the fuel needed for the development contained inside. While while does not obviate the outstanding questions of what to do long term with spent fuel and nuclear waste, the smaller size and sealed characteristic do compartmentalize the waste issue per reactor, which appears to be the de-facto national policy for handling nuclear waste until a more permanent solution can be politically agreed upon.

Some of the newer smaller systems are even air cooled, like the Babcock & Wilcox mPower reactor, which would allow for deployment in water scarce regions like the southwestern states.

Lastly, while no system is fail-proof, the smaller units lessen the scope of damage that could occur from an accident, and again their self contained structure is intended in part to minimize error and contain a potential accident. While this may not assuage all opponents, it may make it more feasible to locate them on smaller sites or with less opposition.

Examples of small, battery style reactors under development (organized by decreasing size) include:

• The Small, Sealed, Transportable, Antonymous, Reactor SSTAR being developed by the Lawrence Livermore National Labratory in the US.
• The Babcock & Wilcox mPower, set for reactor design approval in 2012, and possible deployment in 2018.
• the GE PRISM, set to submit for design approval in 2011.
• the Westinghouse and their parent company Toshiba’s micro reactor the 4S: Super-safe, Small, and Simple

Small reactors still have significant obstacles, including the long term waste issue, well entrenched electricity generation competitors, and the issue of security for any reactor, including the possible byproduct of breeder style reactors – plutonium. Yet despite these detractors, small reactors have been used on military ships for decades. Given time and the proper due diligence, perhaps development of these technologies will bring dispersed, reliable, carbon free energy to augment the electricity system as it grows to meet increasing need.

Power to the People

Ask yourself a question for a moment: How many electrical cords do you use on a daily basis? You charge your cell phone, power your refrigerator, toaster, microwave, television, computer, etc. The infrastructure for electricity delivery in the United States is truly impressive considering how many devices we support on a daily basis. However, as the modern way of life continues to be ever more “on-the-go”, point sources of electrical supply may not be sufficient for consumers that crave longer battery life and less charging.

For true portability and mobility, we all want electronic devices that require little to no time plugged in. Imagine a world where you can walk into a room, and your cell phone or computer is powered without any cords, or any effort on your part. Imagine going on a week long hike and never having to charge your mp3 player in the middle of the woods. Imagine being able to capture energy using the most mundane of sources: a piece of paper or a t-shirt. Everything you are imagining is achievable by today’s technology. Lest this post sound too much like a sales pitch though, suffice it to say that these ideas pose an interesting question regarding our future energy policies and needs.

In the past decade, scientists have developed means for wireless power transmission over several meters, carbon nanotubes spread into paper and cloth that serve as wearable batteries, curtains that shade a room and capture energy from the sun using photovoltaic cells, biomechanical energy harvesters that capture energy from human movement, and the list goes on. While some of these advances are purely novelties at this point in time, it is certain that the future will trend more and more towards mobility and longevity of electrical devices. These inventions represent an innovation in thinking, to the end that one need not bring the device to the wall outlet, but rather bring the wall outlet to the device (in a manner of speaking).

For now, the utility companies still supply the power to the wireless transmitter, and the carbon nanotube paper battery  requires a bath in electrochemicals (manufactured no doubt using utility companies). But if we go down the rabbit hole of speculation: with the advent of more and more technologies each year, if our next generation cell phones are charging themselves from a battery t-shirt, or leeching power from a nearby transmitter, how will the law keep up?

Some homesteads are already generating their own power and selling it back to the grid. What if that same capability were available on a per capita basis? If every person is both using from and supplying energy to “the grid” (if such a thing could be engineered), how can we keep the system fair? If power supply is not consolidated in utility companies, but rather, distributed among the population, will we be able to construct policies to control price, reliability, and equal use? Though none of these products are commercially available, let alone viable, it is also uncertain whether our governmental system and the representatives in control of that system are equipped to handle the complexities involved in such a scheme.  Furthermore, how would the balance of energy concerns (National Security, Environment, and Economics) change? It may a long way off, but as we take energy and power supply back to a home/residence level, and even to a personal level, we find that there is a mix of promise in the potential applications, and uncertainty as to its feasibility and sustainability.