Shock Wave: Electricity From The Ocean

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?

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.

Lawn of the Dead: How Cutting your Grass Affects Wildlife

All ecosystems are fragile and vulnerable to devastating chain reactions. By reducing the diversity of the plants on your lawn, you greatly reduce the hospitability of that environment for insects like bees, beetles and butterflies. This, in turn, has an effect on the food supply available to birds and small mammals. On top of all this, most of us cut the grass with either petrol-powered or electric mowers, both of which hasten and intensify climate change, the greatest threat currently facing people and animals alike.

Why do we cut our grass? The short answer is that we think it makes our gardens look neat and respectable. What would the neighbours think if our grass was long and full of weeds? What this kind of thinking fails to consider is the massive toll that lawn mowers have on local wildlife. All ecosystems are fragile and vulnerable to devastating chain reactions. By reducing the diversity of the plants on your lawn, you greatly reduce the hospitability of that environment for insects like bees, beetles and butterflies. This, in turn, has an effect on the food supply available to birds and small mammals. Some animals like mice and hedgehogs are often killed directly by the blades of mowers. On top of all this, most of us cut the grass with either petrol-powered or electric mowers, both of which hasten and intensify climate change, the greatest threat currently facing people and animals alike.

Humans have an obsession with shaping and controlling the world around us. Vast tracts of land are occupied either by our urban environments, crops or livestock. In the suburbs of our cities lie hundreds of millions of houses, with hundreds of millions of gardens. The reason gardens are so ubiquitous is that we psychologically require some part of our artificial environment to at least resemble nature. That is also why the paintings we hang on our walls often depict natural landscapes. While grass that is cut every week or two resembles nature, it is by no means natural. The hormones which suppress horizontal growth are in the tips of each blade of grass, which means that frequent cutting eventually creates a dense carpet which is impenetrable to anything but the grass.

To a bee, the difference between a well-cut lawn and a natural meadow is like the difference between a desert and a buffet. Global insect populations have been crippled in recent years by a combination of pesticides, herbicides, habitat loss and overactive lawnmowers. A 2017 study found that the number of flying insects in Germany has dropped by more than 75% in less than 30 years. Though you may think they’re creepy and unnecessary, insects serve a vital role in almost all ecosystems. Just like any other chain, if you break one link in a food chain, the whole thing becomes useless. The issue is not just the food supply of other animals, but also that some insects serve a critical function as pollinators. Three quarters of the world’s flowering plants and a third of all food crops depend on pollinators for their survival.  

Plants really are the bedrock of all ecosystems. Animals have no way of converting the energy of the sun into energy that we can use to do things like move and breathe, so we rely on photosynthesising plants for all of our nutrients. Even if you eat a lot of meat, poultry and fish, it’s important to remember that those animals only survived their first day on earth because of the nutrition they got from plants. Whether it is corn-fed chicken or grass-fed beef, we owe everything we eat to plants. Without pollinators like bees, many plants are left with no way to reproduce and, thus, no way to survive.

Petrol-powered lawnmowers are not regulated in the same way that petrol-powered vehicles are. The U.S Environmental Protection Agency (EPA) estimates that each petrol-powered lawnmower produces as much air pollution per year as 43 new automobiles being driven 12,000 miles each. If you’re thinking that this section doesn’t apply to you since you have an electric mower, it is important to remember that the electricity required to power your mower comes from a power plant that most likely used fossil fuels to generate the electricity.

If it is a choice between the two, however, electric mowers are the much greener choice. The emissions are more controlled and you do not need to use fossil fuels to transport the petrol all the way from a refinery to your back garden. In addition to this, the EPA estimate that 17 million gallons of petrol are spilled on lawns each year by Americans refuelling their lawnmowers. That is 6 million gallons more than was spilled in the infamous Exxon Valdez oil spill in 1989. Manual mowers which are powered by the elbow-grease of the user are both cheaper and better for the environment than either of the other kinds. If you are not able to push a manual mower for that long, solar-powered models are also available.

Lawn mowers are expensive. The fuel or electricity which powers them is expensive. On top of that, the actual process of cutting the grass requires time and effort and is widely considered to be a chore. A 2008 poll found that 58% of Americans surveyed said that they disliked cutting their grass. Ian Graber-Stiehl, in an article for Earther, claims that Americans spend between 47.8 and 82 billion dollars per year on lawncare and landscaping, compared to the 49.4 billion dollars they spend on foreign aid. Like smokers or alcoholics, we are paying through the nose to shoot ourselves in the foot. And for what? So that the neighbours don’t look down on us? My personal view is that if having long grass causes someone to lose respect for you, then that person’s respect is something you can do without.

For me, the important question to consider here is whether the benefits of cutting the grass outweigh the costs. I would argue that the answer to this question is a definitive no. The list of cons includes the killing of wildlife, contribution to climate change, high costs, noise pollution, air pollution and the fact that most of us hate doing it. The only real pro is that cut grass looks better, but even that is a matter of taste.

Personally, I think that a natural garden, with all its colour and movement, looks far more appealing than a still and monotonous carpet of green. It is important to point out that this is not an all-or-nothing situation. If you don’t want to abandon your mower altogether, you can still allow a neat patch of grass to grow long or mow a path to a small clearing where you can immerse yourself in the wild beauty that will surround you.

We need to change the perspective on this. We should not look down on people with long grass, quite the opposite! Those people are the ones who are helping their local environment by providing food and shelter for wildlife and cutting down on their carbon emissions in the process. In the age of anthropogenic climate change and mass extinction, the aesthetic appeal of our gardens needs to be lower on our list of priorities than helping animals to thrive.

We have brought the natural world to its knees in so many ways. The continued existence of every species on earth needs to be our top priority, not because they cannot take care of themselves, but because we are the ones who have endangered them. We have a responsibility to fix what we have broken and not only does leaving your grass to grow achieve that goal, it also saves you money and reduces greenhouse gas emissions. It is not often that you find a free way to help the environment, let alone one which will save you both money and effort. This is one of the rare win-win ways in which we can help our fellow inhabitants of earth get back on track.