Add hydrokinetic to that mix please -- ocean waves, tides, and currents. Water has much higher energy density than sunlight or wind.
You can install our site as a web app on your iOS device by utilizing the Add to Home Screen feature in Safari. Please see this thread for more details on this.
Note: This feature may not be available in some browsers.
He's a smart man, but wrong on this. His calculations mistakenly consider waves to be linear fronts rather than having depth; furthermore, he assumes very poor conversion efficiency. The US West Coast, the British Isles, Portugal, South Africa, and several other regions could easily generate 100% of their total power requirements from ocean waves using technology that is currently under construction. It doesn't solve the problem of matching generation to load, however; we either need a lot of storage (including existing hydro and pumped hydro) or fossil generation.Robert.Boston: Wave might contribute, but not by much. Britain is very well endowed with wave power - it's ideally positioned right in the path of the waves of the Atlantic. Still, MacKay estimates the upper bound to be 4 kWh/day/person. That's about 2-3% of the needed amount. Tide is good stuff though, particularly because it's reliable. MacKay's estimates for Britain are here, he gets a maximum of about 8% of UK consumption. Britain is exceptionally well endowed with tidal power. We still need to find a way to store 80% of UK consumption for two or three weeks.
At this point, details are still proprietary. Waves have depth, so the energy drawn off the top by a floating device is quickly replaced by energy from lower depths.Robert.Boston, this is really interesting. If you have any links to better info on the energy content of waves, then I would be very interested.
I don't immediately understand how the linear front idea can be wrong - is it not true that incoming waves only can be harvested once?
dhrivnak: That's the book I'm linking to above I also think it's very good. Chapter F, here, explores the physics of wave power.
There are two big omissions in his book, though: The first is that he seriously underestimates the difficulty of backing up wind and solar. He considers outages lasting a few days, but the truth is that wind and solar frequently fall below 10% throughout entire continents and for weeks at a time.
Let’s look at real data and try to figure out a balanced viewpoint. Figure
26.2 shows the summed output of the wind fleet of the Republic of
Ireland from April 2006 to April 2007. Clearly wind is intermittent, even if
we add up lots of turbines covering a whole country. The UK is a bit larger
than Ireland, but the same problem holds there too. Between October 2006
and February 2007 there were 17 days when the output from Britain’s 1632
windmills was less than 10% of their capacity.
At the end of February, a demonstration project designed to use the ocean swell they produce went live. As a result Australia’s largest naval base now gets part of both its electricity and its fresh water courtesy of the ’Forties.
The buoys themselves are 11 metres across, made of steel and filled with a mixture of seawater and foam to give them a density slightly below that of water, so that they float. Being submarine means that, unlike previous attempts to extract power from waves, they are not subject to storms and the constant battering that life at the interface between sea and air brings.
Even below the surface, though, the swell is enough to generate power. Each buoy’s rising and falling drives, as the diagram shows, a pump attached to the seabed at the bottom of that buoy’s tether. This pump pushes water through a pipe to a power station on Garden Island. There, the water’s pressure spins turbines that turn a generator. This arrangement produces about 5% of the base’s electricity.
Interesting! Amazing how much energy the Earth could produce to help us to get rid of fossil fuels.
I personally find harnessing both waves and wind a bit cumbersome, but better than digging and processing fossils.
Me too. I always feel kind of tired and worn out after being outside harnessing wind or waves for a couple of hours. Now tanning on the other hand relaxes me.