Tidal streams are underwater turbines that take advantage of the fast-moving sea currents that occur when the tides rise and fall.3 The energy generated by the turbines is then transferred back to the land via underwater cables. Available in a variety of forms, the most common is a multi-blade turbine, not too dissimilar to an onshore wind turbine.4 However, because water is some 800 times denser than air,5 a 15-metre-diameter tidal turbine can generate as much energy as a 60-metre-diameter wind turbine.6 Furthermore, if the tidal stream turbines are able to swivel, they can capture energy both as the tide comes in, and as it goes out.7 To allow for safe maintenance, both the turbine and the generator can be mechanically lifted above the water.8 To date, no large-scale tidal stream arrays have been constructed, but a number of schemes are under construction including one in Scotland that, when finished, will have 269 tidal stream turbines.9 Together, they are expected to generate enough energy to power 175,000 homes.10 Unfortunately though, it is estimated that tidal streams can only supply 1% of the world’s energy demand.11 As such, although they have some relevance, they cannot be considered a global solution.
If we pretend that the United States is a shallow sea flowing at around 1.5 metres per second, some 4% of the area of the country would have to be covered with tidal streams to meet the country’s energy demand.20 For the UK, the equivalent of some 12% of the country’s landmass would have to be covered with tidal streams to meet the nation’s energy demand.21
Tidal streams are large structures, but, as they can be submerged entirely beneath the water, visual impact will be minimal. Despite this, some form of way-finding will be required for waterborne transport to avoid collisions with the submerged tidal streams. Furthermore, the tidal streams will be visible when they are raised for maintenance. However, raising the tidal streams for maintenance is more likely to be considered a spectacle than as something that damages the appearance of the landscape.
Tidal streams are best located in areas of strong tidal movement.22 This can be found along small streches of the world’s coastlines and particularly in areas that funnel or capture large expanses of the ocean.
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| Global Potential | | | ★ ★ ★ ★ ★ ★ |
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To summarise, tidal streams provide a highly predictable energy source that causes minimal disruption to marine life. Tidal streams can also be submerged so they have minimal visual impact. Despite this, there is limited global potential and they are currently prohibitively expensive. However, it is likely the cost will significantly reduce once the technology becomes more developed. We are not limited to using the tides to generate our energy from the sea though. Why not see what waves have to offer by clicking the link below? Alternatively, find out other ways we can stop climate change by returning to the main menu.
Title image created by and copyrighted to Siemens.
United States map created by SUPER RADICAL.
Image of underwater turbines created by and copyrighted to Siemens. Minor modifications undertaken by SUPER RADICAL LTD.
World map created by SUPER RADICAL. World map based loosely on all coastlines not covered by ice that benefit from a tidal range greater than four metres. Tidal range sourced from Commonwealth of Australia, Bureau of Meteorology – ‘Tidal Range’ – Map. Areas of ice cover sourced from Koistinen, Ville – ‘The Main Biomes in the World’ – commons.wikimedia.org.
All figures presented in this section are estimates based on best available data, assume optimum locations, and, wherever possible, are based on comparable studies. That said, many of the studies assume different economic conditions, climatic conditions, time frames and locations. Furthermore, the technologies discussed in this section are in a constant state of development. As a result, the figures presented within this section provide a rough guide only and should not be viewed as a definitive performance level.
For the total world energy demand, a figure of 104.4 million GWh has been used. The figure is based on 2012 data and sourced from International Energy Agency – 'World Balances for 2012' – www.iea.org.
All UK to USA currency conversions have been set at $1.656 USD for each £1 GBP. The figure is based on the conversion rate as of the 1st January 2014 and sourced from XE – 'XECurrency Table: USD - U.S. Dollar' – www.xe.com.
For further information about any of the above sources, please visit the ZERO EMISSION WORLD Works Cited page.
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To summarise, coal is a solid energy source that is primarily used to generate electricity. However, using coal produces large quantities of carbon dioxide – the key driver of climate change. The majority of the carbon dioxide could be captured, however, most people would likely be unwilling to pay the additional cost. As such, we […]
To establish which energy source is best, we use six key metrics. Specifically, these are energy price, life span, energy generated per square kilometre, payback period, carbon offset period and global potential. In this article, we explain what these metrics are and how we use them.
Before we get started, there are a few basic questions that we need to answer. Specifically, we need to know what is renewable energy, what’s good about it and why aren’t we already taking advantage of the many benefits renewable energy has to offer.
Using offshore wave devices, a one-kilometre stretch of coastline could provide some 128 million kWh per year.5 That’s enough energy to power some 6,800 typical homes,6 slightly more than we could power using nearshore wave devices.7 However, are there enough waves available for us to meet the world’s energy demand using offshore wave devices?
A one-kilometre stretch of coastline could provide some 104 million kWh per year using nearshore wave devices.8 That’s enough energy to power some 5,500 typical homes.9 However, can we meet all the world’s energy demand using nearshore wave devices? Furthermore, what damage would this do to our coastlines?
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Make no mistake, climate change is the biggest threat we have ever faced. If we continue to emit greenhouse gases at the current rate, our planet will be beyond salvation in less than a decade. We need to act fast, and we need to act now, but what can we do? ZERO EMISSION WORLD is an all-encompassing graphical solution to climate change that demonstrates how human-made emissions can be reduced to zero by the year 2050. This includes explaining how we can dramatically reduce the amount of energy our buildings, vehicles, and factories consume while also demonstrating how we can power our remaining energy demand using only renewable technologies.
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