Renewable Energy

Shock Wave: Electricity From The Ocean

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First published in UCD College Tribune

Even in this futuristic world of ours, all our electricity is generated by simply spinning a turbine. The fossil fuels which are bringing us ever closer to a complete climate catastrophe are not just used to power our cars, but also to create steam which generates the electricity needed for everything from phones to lightbulbs. This is exactly the same principle employed by nuclear power plants. In both cases, fuel is used to create heat, which is used to generate electricity. There are ways, however, to generate electricity which do not require heat at all. Some renewable technologies harness the vast mechanical power available from a planet that is in constant motion. Wave power generators (WPGs) are a possible energy source of the future, but how do they compare with their rivals?

It is worth quickly comparing ocean energy and wind energy since the two are similar in a number of ways. This is why underwater turbines closely resemble those of wind farms. A major difference between the two is the potential energy contained within. Water is nearly 800 times denser than air, meaning that the same volume, travelling at the same speed, contains much more power. What this means on the practical side is that much smaller devices can produce the same yield of energy.

A major difference between WPGs and tidal power is the source of energy. Tides result from the gravitational pull of the moon dragging water up and down our shores as it passes by above us. WPGs, alternatively, find their energy source in the sun. Solar radiation does not heat the earth evenly. The air in places which receive more heat rises upwards, allowing colder air to rush in to take its place. That rushing of air is what we call wind. Since wind is the driving force behind waves, any energy that we harvest from waves comes indirectly from the heat of the sun. It is for this reason that WPGs are considered a renewable technology.

Tidal power is perhaps the most reliable source of energy on earth. Twice a day like clockwork, unimaginably vast quantities of water rush in and out of our coasts. Globally, there is as much power available from tides alone as there would be from nearly 5 and a half billion coal-burning plants. One of the problems, however, is that only a very small fraction of this energy could actually be harvested. There are only 40 or so places in the world where the difference between low and high tide is great enough to produce a worthwhile amount of power. One way that the power of the tides can be harnessed in such places is by building tidal ‘barrages’. These consist of huge dams which trap water from the rising tide, then release it slowly when the tide is low. As the water passes through the dam back into the sea, it spins a series of turbines to generate electricity.

WPGs come in a variety of forms. One very cool design that was deployed in the ocean as far back as 2004 resembles a giant sea-snake. Each segment of the snake is attached to the next by hinge joints which are connected to hydraulic rams. As the sections of the snake move back and forth over the waves, the hydraulic rams drive a series of electrical generators.

Another simple yet ingenious way of harnessing the power of waves is by using a device known as an oscillating water column (OWC). These machines consist of a hollow cylinder containing a turbine which is attached to a buoy. As the waves pass by underneath, air is forced up through the cylinder, spinning a turbine. What makes these devices truly remarkable is the special kind of turbine contained within. The so-called ‘Well’s Turbine’ is shaped in such a way that it can generate electricity regardless of which way the air is flowing. This means that power can be harnessed when the device is rising to the crest of a wave and also when it is falling to a trough, doubling the overall efficiency.

The final method for generating electricity from the ocean is called ocean thermal energy conversion (OTEC). This is another way we can indirectly generate solar energy using the ocean as a middle man. The way OTEC works is that a liquid with a low boiling point (like ammonia) is evaporated by the warm surface water of the ocean and expands, spinning a turbine. The ammonia vapour is then condensed using cold seawater and returned to the evaporation chamber to start the process over again.  The technology required for this method is simple and rapidly improving, meaning that OTEC is very much one to watch out for in the coming years.

So, which is better, WPGs or tidal barrages? WPGs hold greater promise in my view, largely because tidal barrages can be devastating to already strained marine ecosystems. Think about it; much of the ocean’s life is concentrated close to the shore. As the tide rises, both water and marine life can pass freely through the dam. Once that waterway is shut, however, the only way back to the sea is through a series of rotating blades. Many barrages are built on estuaries where rivers meet the sea. By preventing free movement through these estuaries, barrages can also seriously disrupt the spawning patterns of fish like salmon. WPGs, floating on the surface in open water, are much easier to build in a way that’s hospitable to marine life.

This is of vital importance; through plastic pollution, overfishing and ghost fishing, we have already utterly decimated almost all marine life. With plastic pollution and ocean acidification set to get much worse, we simply cannot afford to do any more harm to the beautiful animals that reside beneath the waves. If a plan is to be truly environmentally friendly, it must consider not only the CO2 it will emit, but also the effects it will have on our fellow animals. It is this major issue, coupled with the location problem mentioned earlier, which means that WPGs hold more promise than tidal barrages. In any case, it is clear that as both the financial and environmental costs of fossil fuels rise in the coming decades, blue power will assume an increasingly important position in the global energy industry.

Win Win Win Win: The Magic Science of Plasma Waste Converters

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First Published in the UCD College Tribune

Humans have an incredibly extensive waste problem. Right now, most of that waste is sent to landfills where it takes up space for thousands of years, leaching harmful chemicals and gases into the soil and atmosphere. Alternatively, we send our waste to incinerators which burn it for energy, but which release harmful greenhouse gases (GHGs) and toxic by-products in the process. A large proportion of our plastic waste ends up in the ocean, where it strangles and poisons fish, seabirds and marine mammals. What if I told you that there was a way to get rid of almost any type of waste in one machine, that the machine would release no harmful chemicals or GHGs, and that the process would produce useful by-products and excess energy that could be sold back to the grid? Such a machine exists right now; the plasma waste converter (PWC).

While incinerators are able to extract about 15% of the potential energy from rubbish, PWCs can extract an incredible 80% through a process called ‘gasification’. Plasma is ionised gas, meaning that it contains roughly equal numbers of positively charged ions and negatively charged electrons. It is often called the fourth state of matter since its characteristics are so different to those of liquids, solids and gases.

One way you can make plasma is by creating an arc of electricity between two rods, then passing a gas like argon through it. This set-up is known as a plasma torch and can heat gases to a higher temperature than the surface of the sun. Plasma torches were invented by NASA in the 60s to test how much heat the hulls of their spaceships could withstand. The crucial difference between using a plasma torch and using an incinerator is that in PWCs, combustion doesn’t take place. That means no smoke, no GHGs and no ash. The plasma breaks down the bonds between atoms, separating them into very simple forms. Despite the extremely high temperatures, it would be wrong to say that the waste is being ‘burned’; rather it is being decomposed at an accelerated rate.

One of the products of gasification is, you guessed it, gas. This energy-rich gas, known as syngas, is largely made up of hydrogen and carbon monoxide. Syngas mainly comes from the gasification of organic matter. As the gas expands, it spins a turbine, generating electricity. The high temperature of the gas can also be used to evaporate water, generating steam to turn another turbine. The syngas itself can then be burned for fuel or scrubbed with water and released safely. Remember, all of this energy production and revenue is coming from rubbish. We are talking about the plastics that are decimating marine life. Metals, fabrics, wood, even toxic or hazardous waste from industrial run-off or medical facilities. This is stuff that we desperately need to get rid of and by getting rid of it like this, we can also take some of the stress off an already strained energy production sector.

The solid by-product of gasification is called ‘slag’. Slag is produced mainly from inorganic materials like metals. It can be used in construction to bulk up concrete and tarmac, making it a very useful commodity. The molten slag also pools at the bottom of the chamber and helps to maintain the temperature, reducing the energy consumption of the PWC. The real magic happens when you pass compressed air through molten slag to create a material known as ‘rock wool’. Rock wool is currently made by drilling into rock, melting it down and spinning it in a centrifuge. Made in this way, rock wool is sold at one US dollar per pound. When it’s made of rubbish instead, it can be sold at just ten cent per pound.

Rock wool can be used in a number of ways. As an insulation material, it is twice as efficient as fibreglass and could significantly decrease heating and air conditioning bills, further reducing the carbon footprint of gasification. Surprisingly, you can also hydroponically grow plants from seed in rock wool. Perhaps its most amazing use is that it can clean up oil spills. Rock wool is lighter than water and extremely absorbent. This means that if you spread it out over the surface of an oil spill, it will float and absorb all the oil. The rock wool can then be collected with relative ease. Slag and rock wool are two more saleable products that can increase the economic viability of plasma waste conversion.

PWCs are currently being built all around the world. Some plants are already so efficient that they need to take rubbish out of landfills to use as feedstock. There is even a mobile plasma torch on the back of a truck in the US which can be jammed straight into landfills, which act as makeshift gasification chambers. The need to reduce GHG emissions and simultaneously fix our massive waste problem has generated huge interest in PWCs in recent years. Landfills have only one way to make money; they charge you a ‘tipping fee’ for getting rid of your waste. Since PWCs can generate revenue from both energy production and by-products, they can make their tipping fees much more competitive.

So why haven’t these things solved the problems of pollution and climate change already? The answer is largely that PWCs are still a relatively new technology. The cost of building and operating one is still much higher than that of some of its competitors including landfills and incinerators. There has not yet been standardisation of the design and thus the huge and complex machinery must be custom-built every time. The energy needed to power PWCs is also very high, especially compared to incineration, which requires only a match. It must be said, however, that although it takes a lot of energy to run a PWC, you will very quickly make all that energy back and more. PWCs are extremely efficient long-term; unfortunately, short-term profits dictate much of what happens in society.

One worry is that by making waste a profitable commodity, we encourage people and companies to keep polluting with impunity. The best way to solve pollution is not to pollute more and then clean it up better. It is to reduce the amount of pollution we are producing, whether that is by reducing our individual consumption, or by researching innovative ways to package our goods without making a mess. There is, on the other hand, already a lot of waste out there, languishing in landfills and contributing to the decimation of marine ecosystems. The best thing to do with all that waste is to get rid of it with the fewest possible emissions and the most possible benefits. PWCs may be just the technology for the job.

The price of fossil fuels is slowly being raised by various economic policies to reflect the cost to life on earth and we need to find as many alternative sources of energy as we can. With countless landfills already full and the world still producing around 2 billion tonnes of waste per year, rubbish will not be scarce for a very long time. This really is a win win win win win. One machine can get rid of harmful waste, cut GHG emissions, produce fuel, energy and construction materials and clean up oil spills all while making a profit. An investment in plasma waste converters is not only economically sound, it is also an investment in the future of our planet.

Getting High on Grass – Can Plants Really Fuel a Plane?

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Updated 11/09/2019

In the wake of recent studies showing how dangerously close to the brink we are when it comes to climate change, it is more important now than ever to seriously consider every possible alternative to environmentally damaging fossil fuels. One such alternative comes in the form of biofuels. Humans have been using biofuels for as long as we’ve been using wood to fuel our fires. In the last hundred or so years, however, we’ve begun to understand how plant matter can be converted into liquid fuels that could soon power a plane. In this piece, I’ll be looking at where biofuels are now and where they need to be if they are to significantly reduce CO2 emissions. I’ll be concentrating my efforts on recent attempts by the scientific community to make grass a viable fuel for transportation.

Grass is the most abundant plant on the planet. In my home country of Ireland, more than two thirds of all land is covered in naturally growing grass. If we could refine and perfect the process of turning grasses into fuel (grassoline), this could be a real contribution towards slowing the march of climate change. The problem right now is that it is expensive and inefficient. Many scientists in the field, however, think that given time and money, we could tap into this huge source of unharnessed power and perhaps help to save the planet in the process.

The reason grass in particular is being considered as a biofuel is not because it is necessarily the most efficient plant to use, but rather because of its abundance and willingness to grow in fields that are inhospitable to food crops, known as marginal lands. Another reason that grass is attractive as a biofuel is that it is not really needed for anything else. Other candidates for biofuels (like wood, sugarcane and soybeans) have the disadvantage of being useful for things like furniture, rum and tofu.

But why aviation fuel? One reason is that while cars are slowly turning electric, it is unlikely that planes will follow suit any time soon. This means that in the near future, cars could be powered by renewable sources whereas planes will continue to require liquid fuel. The other more pressing reason is that travelling by plane is far worse for the environment than any other mode of transport. This is down to two factors; first, planes are less efficient than other modes of transport in terms of emissions per passenger mile. Second, planes allow us to travel a far greater number of miles than we would otherwise be able to travel. The carbon footprint of flying from London to Hong Kong and back again is about a quarter of the average UK person’s annual carbon footprint.

The idea that we could use grass, algae and other plants to produce aviation fuel is not nearly as crazy as it sounds. The fossil fuels which we currently use are themselves made of organic matter that has, over a very long time, undergone a natural process called pyrolysis. Human beings have been using the process of pyrolysis for our own gain for thousands of years in the form of charcoal burning. Pyrolysis involves separating materials into their constituent molecules in the absence of oxygen. This means, very roughly, heating up the material to a specified temperature, covering it, and allowing it to separate into liquid, solid and gas. These products can then be refined into fuels. Recently, it has been found that microwave heating produces a higher pyrolysis yield than traditional methods since it can be done entirely in the absence of oxygen and at a very precise temperature. Another benefit is that the characteristic ‘hot spots’ of microwave heating aid in pyrolysis.

You might be thinking that grass is an important source of food for livestock. The beauty of using grass as a biofuel is that this resource would not be lost. The solid by-product of grass pyrolysis can still be fed to livestock. What’s more, by removing the liquid constituents, the feed can be preserved much longer than fresh grass cuttings. In the UK, biofuels already account for nearly 3% of all road and non-road mobile machinery fuel, but with the predicted change in efficiency given a few years, they could eventually account for a lot more than that.

Right now, scientists can only produce a few drops of biofuel from grass in the laboratory. Tests carried out at Ghent University in Belgium show, however, that there is a potentially very efficient energy source in grass if we can learn to harness it correctly. In April 2017, the researchers at Ghent found that a certain type of bacteria (clostridium) can be used to metabolize certain grasses into decane, a key ingredient in both petrol and aviation fuel. While this breakthrough cannot yet be used effectively, it is key knowledge that will inform future research into better biofuel technologies.

Hang on, you might say, if refining plant matter gives us the same fuel as we are already using, then why is it better for the environment? Surely biofuels release the same amount of CO2 as fossil fuels? This is indeed true. The difference is that the CO2 in living plants has only recently been absorbed from the air by the plant and is simply being released again. As the grass grows, it sequesters CO2 from the air. When it burns, that recently absorbed CO2 returns to the atmosphere to be trapped by the next batch of grassoline. Because of this, biofuels are said to be ‘carbon neutral’. With fossil fuels, the CO2 has been absent from the environment for a very long time, trapped underground. By burning it, we are releasing extra CO2 rather than what was already there.

A major obstacle to biofuel efficiency growth is that governments and companies are not willing to invest heavily in something that may not yield solid results for years to come. This is simply short-sightedness. The science will continue to improve. Lack of investment only slows down the process. The people who invest heavily now will surely see a huge return in a matter of years. Another well-known obstacle in the way of all renewable energies is the huge sums of money tied up in the fossil fuel industry. The industry is worth about 7 trillion USD globally. No wonder, then, that lobby groups are able so easily to sway policy-makers.

Biofuels are controversial among environmentalists, since they come with a number of downsides. Perhaps the most worrying is that every square foot of land which is used to produce the fuel is land that could instead be used to nurture biodiversity. Species are currently being lost so quickly as to constitute the sixth mass extinction in earth’s history. For me, using food crops like corn as feedstock is entirely off the table, since it opens the door to a future in which rich elites use corn-fed biofuel to fly away on their holidays while depriving poor people of food which is vital to their survival.

Another drawback is that biofuels are not very efficient when it comes to land use. According to Mike Berners-Lee, using solar panels instead to generate the power for flying would require 270 times less land than growing wheat for biofuel. The problem, however, is building a good enough battery. Right now, 1 kilo of jet fuel carries about the same energy as 20 kilos of premium lithion-ion batteries. One ray of hope came in March of 2015; ‘Solar Impulse 2’ began its attempt to become the first entirely solar powered plane to fly around the world. The journey was arduous and long for the two pilots. One of the pilots was named Bertrand Picard, a Swiss medical doctor who who was already the first person to fly around the world non-stop in a hot air balloon. Captain Picard of the USS Solar Impulse finally landed the plane in Abu Dhabi on July 26th 2016, from the spot where it had departed 505 days earlier.

Regardless of what figures like the US president may say, climate change is a very real and very serious danger. Biofuels are just one example of the many ways in which we can combat this danger, but they are one which will continue to grow in importance for years to come. The question is whether our money would be better spent developing renewable energies like solar and wind which require far less land and are thus better for wildlife conservation. When it comes to planes, however, grassoline may help to ease the transition to a low-carbon world. Every little helps in the fight against the huge and menacing entity that is climate change.

Some Further Reading and Research Sources