Tuesday, 11 October 2016
Monday, 14 December 2015
Five ways chemicals can save the world from climate change
When it comes to the environment, the chemical industry doesn’t have the best reputation. Yet it has a vital role to play in developing technological solutions to help save us from climate catastrophe, and could create significant opportunities for global economic development at the same time.
1. Energy storage and transport
The growing use of intermittent renewables such as solar power will increase the demand for storing and transporting energy. We could generate enough energy for the whole planet by covering 3% of the Earth’s landmass with cutting-edge photovoltaic (PV) solar panels. But the best place for them is in the middle of deserts rather than close to consumers, meaning we would need to transport the energy over long distances. And the sun doesn’t shine at night, so if using PVs we would need to keep at least 12 hours’ worth of energy stored as a buffer, too.
The scale of this challenge means that we cannot simply use a pile of batteries made from existing technology. But we are already able to transport and store large amounts of energy in the form of gases or liquids in our global network of pipelines, freight vehicles, and containers. Instead of fossil fuels being taken out of the desert, we are likely to see the production of chemicals with a high energy content such as hydrogen, methane, or ammonia wherever clean energy is available. Their handling, processing, and transport are routine in the chemical industry – expertise the future green energy sector will tap into.
2. Fertiliser production
Ammonia is also used to make fertiliser, and the chemical’s large-scale production was a major breakthrough in efforts to feed a growing global population. The fertiliser industry is still a big energy consumer, and producing ammonia close to renewable energy sources and agricultural production sites rather than in centralised facilities will be an important way of reducing its carbon footprint.
Any sustainable fuel or fertiliser cycle will also have to account for the water supply. Making ammonia (NH₃) uses hydrogen, which is present in all high-energy chemicals (fuels) and ultimately requires water for production. The fact that the most solar power can be generated in places where water is scarce is one of the biggest obstacles to a large-scale roll-out of renewables-based fuel – and needs to be addressed.
3. Electric vehicles
Electricity-powered transport is the only way out of polluted cities, but this demands improved energy storage technologies. Incremental improvements in battery materials and manufacturing have brought electric vehicle prices down and their performance up. Further progress is possible, but there are limits as to how far a technology derived from magnetic tape manufacturing can be pushed.
Breakthroughs in completely new technologies that combine lithium with oxygen or sulphur will pave the way for the next generation of electric vehicles. We’ve also seen fuel cell vehicles that generate electricity from hydrogen, such as the Toyota Mirai and Hyundai ix35, enter the market. Fuel cells still rely on expensive and environmentally costly platinum, but fundamental chemical research could provide alternatives.
4. Hidden energy storage
The chemical industry itself is actually a massive player in the energy market. Plants can increase or cut their energy usage at the request of grid operators when there’s too much or too little electricity being produced in order to balance supply and demand. But they could also provide a form of energy storage.
Many chemicals are produced in several stages, some of which require much more energy than others. Running the more energy-intensive processes when there’s lots of electricity available (like when the sun is shining) and storing the chemicals produced for further treatment later is effectively like storing the energy. It means the factory will be using less energy during peak times, freeing up electricity for the rest of the grid. And building more tanks to hold these intermediate chemicals is more cost-efficient than building a complicated energy storage system.
However, this practice will only happen if it becomes profitable, which will require concerted efforts from both the energy and chemical industries in reforming the electricity market. Politicians can help through tax breaks or subsidies for energy-intensive processes that are designed to encourage companies to become more flexible.
5. Rare materials
Modern LED lightbulbs consume around one tenth the amount of electricity of their traditional counterparts thanks to semiconductor technology based on the chemical gallium nitride. But it comes with a price and another challenge for chemistry: gallium is rarely found on Earth. It is only used in tiny amounts in LEDs, which seems like a good thing at first but also makes it very difficult to recycle and so we could see bottlenecks in its production in the future as demand increases. Similar problems exist with the noble metals such as platinum used in the catalyst filters of petrol and diesel cars and in the electrodes of fuel cells.
Optimising technology to reduce the need for these scarce metals will make them cheaper and require less mining. But again, while that sounds good, it may make recycling impossible. Chemistry is not alchemy: transforming one element into another only occurs in nuclear reactors and particle accelerators, and it will not work on larger scale any time soon. In this way, we need chemists, geologists and logistics experts to join forces to keep us going.
Harry Hoster, Director of Energy Lancaster and Professor of Physical Chemistry, Lancaster University
This article was originally published on The Conversation. Read the original article.
Monday, 2 November 2015
Lithium-air: a battery breakthrough explained
Lithium-air: a battery breakthrough explained
Harry Hoster, Lancaster UniversityIn the quest for smaller, longer-lasting, more powerful batteries, scientists have tried many alternative approaches to battery chemistry. One may have just produced the breakthrough we’re waiting for.
The urban legend is that there was a small leak in a battery cell that chemist K M Abraham was testing in his laboratory in 1995, which provided the cell with a far higher energy content than expected. Rather than try to fix the leak, Abraham investigated and discovered the first rechargeable lithium-air (Li-air) battery. So far this discovery hasn’t led to any technically viable products, but a paper published in Science from a University of Cambridge research group may be about to change that.
In 2008, Tesla amazed industry watchers with its bold, electric Roadster car that ran on off-the-shelf lithium-ion (Li-ion) batteries, the sort that power everything from smartphones to laptops to cameras and toys. Since then, not only has the market for electric vehicles quickly grown, but so has the average range of the batteries that power them. However that growth needs to accelerate: from 1994 it took 20 years to triple the energy content of a typical Li-ion battery.
The new research, led by professors Gunwoo Kim and Clare Grey, experimented with Li-air cells that use only an electron conductor, such as lightweight, porous carbon, instead of a metal-oxide typically used in a Li-ion battery. Practically speaking, this saves a lot of weight, but brings its own difficulties.
How Lithium-air batteries work
A Li-air cell creates voltage from the availability of oxygen molecules (O2) at the positive electrode. O2 reacts with the positively charged lithium ions to form lithium peroxide (Li2O2) and generate electric energy. Electrons are drawn out of the electrode and such a battery is empty (discharged) if no more Li2O2 can be formed.
However, Li2O2 is a very bad electron conductor. If deposits of Li2O2 grow on the electrode surface that supplies the electrons for the reaction, it dampens and eventually kills off the reaction, and therefore the battery’s power. This problem can be overcome if the reaction product (lithium peroxide in this case) is stored close to the electrode but does not coat it.
The Cambridge researchers found a recipe that does exactly that – using a standard electrolyte mixture and adding lithium iodide (LI) as an additive. The team’s experiment also include a rather spongy, fluffy electrode made of many thin layers of graphene filled with large pores. The last important ingredient is a small amount of water.
With this combination of chemicals, the reaction as the battery discharges does not form the Li2O2 that would gunge up the electrode’s conducting surface (see image below, left hand side). Instead it incorporates hydrogen stripped from the water (H2O) to form lithium hydroxide (LiOH) crystals. These crystals fill the size of the pores in the fluffy carbon electrode, but crucially they don’t coat and block the vital carbon surface that is generating the supply of voltage (right hand side). So the presence of lithium iodide as “facilitator” (though its exact role is not yet clear) and water as co-reactant in the process boosts the Li-air battery’s capacity.
How will Li-air change things?
This process which ensures the electrode surface is kept clear is essential to boost battery capacity. However, the drawback is that the same lack of electrical contact between the electrode and the discharge product that boosts its capacity should in principle make it difficult to recharge.Again, it turns out the lithium iodide additive is the missing ingredient needed: at the electrode, negatively charged iodide ions are converted into I3 (triiodide) ions (see picture, right-hand side). These combine with the LiOH crystals and dissolve, allowing for a complete recharge by clearing the pores.
In fact this mechanism is even more effective than the recharge of Li2O2 attached to the electrode surface. Since the electrons do not need to travel through a Li2O2 layer, less voltage is required to recharge a Li-air battery with the iodine additive than without it. So less energy is needed to recharge the battery, which would make an electric car running on such a Li-air battery more energy efficient. The study’s authors present data that are approaching an energy efficiency of around 90% – which brings this new battery technology close to that of conventional Li-ion batteries.
Their findings reveal a promising way forward for Li-air technology, at a time when many other research groups have given up. As more researchers return to the subject following this breakthrough, perhaps a commercial Li-air battery will finally become reality.
Harry Hoster, Director of Energy Lancaster and Professor of Physical Chemistry, Lancaster University
This article was originally published on The Conversation. Read the original article.
Tuesday, 20 October 2015
‘Dieselgate’ is the wake-up call to look seriously at alternative car technologies
We should thank Volkswagen for the wake-up call. The scandal that has engulfed the company has highlighted how an overwhelming focus on carbon dioxide emissions has oversimplified the debate about the negative impacts of all our combustion engines.
Yes, looking at CO2 works well to quantify effects on global climate and fossil resource depletion, but health impacts are a more complex story. “Dieselgate” is forcing people to realise that most vehicles also produce harmful chemically reactive substances such as nitrogen oxides or tiny particulate matter.
This insight has reached the highest ranks of UK government, where diesel subsidies may soon become re-examined. In fact particulate matter may be responsible for as many as 3m prenatal deaths globally every year, according to a recent study in Nature.
No one can tell at this point if this is the end of the diesel engine but surely now is the right moment to look towards cleaner and more sustainable ways to power a car.
Two key technologies are on the rise: electric vehicles, including hybrids, and fuel cell vehicles which run off hydrogen. The problem for electric vehicles is most people like to stay in their comfort zone and are worried about charging stations and mileage. The industry recently passed the threshold of 1m global sales in total, half of these sold since July 2014, but it is still behind targets set by the US and other governments.
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The new Toyota Mirai Fuel-Cell Car
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Fuel cell vehicles are a better match with existing habits. Their energy comes from hydrogen stored in a high-pressure tank which then reacts with water to produce electricity that powers the drive train. This allows for mileages similar to those of conventional cars while being refuelled within a few minutes. Hyundai and Toyota already have small numbers of these vehicles on the market, and some other brands are not far behind.
Hydrogen suffers from a long-standing damaged reputation since the Hindenburg disaster in the 1930s. But lots has changed in the past eight decades. These days, the hydrogen isn’t stored in a flimsy airship but in a tank made of a highly stable carbon composite so the risk of it catching fire is minimal. Hydrogen cars can now be considered as safe as petrol or diesel cars, even in crashes.
The more recent fuelling stations extract hydrogen from water by running a current through it, effectively converting electrical energy into hydrogen fuel (you may remember doing this exact water electrolysis experiment in school). This all takes place on site, next to where the hydrogen is then stored ready for drivers to use. Doing everything in the one place – essentially all you need to bring is electricity and water – helps avoid transporting hydrogen fuel around in trucks.
A point commonly raised in this context is the fact that electricity production still largely relies on fossil fuels and that hydrogen production through electrolysis is not the most efficient way of using that primary energy. And, if one really wished to have hydrogen, the “cheaper” way was large-scale production out of natural gas. But this leads back to the important differentiation between localised emissions that harm your health and global emissions that damage the atmosphere: even if the hydrogen production involves fossil fuels, fuel cell cars are still considerably better for your lungs.
Even the global emissions will benefit from a hydrogen economy in the long run: hydrogen can be stored in tanks, thus allowing for the production of more hydrogen at times of electricity oversupply. Hence, hydrogen fuels will become an essential buffer to help smooth out increasing gaps between supply and demand in the electric grid of the future. That grid will be increasingly dominated by solar and wind power – which follow weather and daylight patterns – and nuclear power, which provides a solid base supply but cannot dynamically react to demand fluctuations either.
Economically, all three technologies are dominated by capital expenditure rather than fuel costs, so producing hydrogen at times when no one else needs the electricity may become even cheaper than today.
Hydrogen refuelling stations are stuck in the same chicken-egg problem that battery-charged vehicles had to overcome. This calls for large strategic investments to ensure that a critical mass of cars powered by fuel cells can be reached and operated, which will then drive down the costs of refuelling stations.
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Hydrogen is produced on site from
wind-generated electricity at this
refuelling station in Yorkshire. ITM Power
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Given such stations can be developed and produced in the UK, rolling out hydrogen refuelling infrastructure will serve a double purpose: it paves the way for cleaner air along our roads and it gives the country an opportunity to lead rather than to react in a rising technology.
We should be more than a market for the hydrogen technology that is already embraced and pushed forward by the big technology nations: Japan, Korea, China, and the US. The recent discussion around the proposed nuclear power plant at Hinkley, French-owned and Chinese-funded, had a similar ring to it. Why is the country that once built the first civil nuclear power plant in the position of a technology-importing customer? On hydrogen, it’s time to take the lead.
Note: this text was recently published in "The Conversation"
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