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⚡"Marine Energy"

The Energy Transition Show

Photo by Andrzej Kryszpiniuk / Unsplash

Table of Contents

Host: Chris Nelder
Guest: Dr. Andrea Copping | Energy & Environment Directorate | Pacific Northwest National Lab
Category: ⚡ Renewable Energy

Podcast’s Essential Bites:

[5:31] “We tend to use the World Bank definition of blue economy. And what they have to say is that it is the sustainable use of ocean resources for economic growth, improved livelihoods, and jobs, while still preserving the health of ocean ecosystems. So this means blue economy could be everything from transoceanic shipping, capture fisheries, aquaculture, includes observation systems at sea that provide data for weather forecasts and search and rescue. And it also includes increased knowledge of the oceans. So we need to do all this so we can protect the oceans and the animals that live there. But at the same time, we can really benefit from the bounty of the oceans.”

[6:13] “We know that the ocean economy is large now, but it's expected to double by 2030 to about $3 trillion worldwide. So the research we do centers around this idea that many of the blue economy uses are powered by fossil fuels, which are unsustainable, or by batteries, which they use for ocean observation platforms […]. So what we want to do is try and produce power at sea, we’ll use the waves, the tides, the ocean currents and other forces to power these uses, and therefore make it easier for these blue economy industries and so on to thrive. But at the same time, we're using marine energy to cut fossil fuel emissions. And we even believe that we can help remove carbon dioxide from the ocean to further mitigate climate change.”

[7:12] “The other thing we do at the same time, we call it resilient coastal communities, we're trying to supply marine energy to remote coastal areas, and islands that are again, using fossil fuels to generate electricity. We think we can get a great deal of use out of this think about coastal Alaska, or perhaps islands in the Caribbean. The other very cool thing about marine energy, we can generate electricity, but we can also do mechanical work directly from the power of the waves and the ocean movement. And this can let you do things like desalinate seawater, and provide power in other ways.”

[8:22] “Right now most of the existing devices that have been developed that have been tested and deployed at sea, and are harvesting energy are from waves and tides. Though there are a lot of other means of capturing ocean energy, large ocean currents, thermal gradients, etc. […] Let's start with tidal energy. […] You have the ocean running through a narrow area, and the tides run very fast through there. Now what we used to capture, these are turbines, and they're not very different from the water turbines that are used in hydropower dams, or even they look the same as air or gas turbines, we use in other energy sources. […] We put these tidal turbines either right down on the bottom with a lot of heavy weight to withstand the currents. Or there's some models that are floating like sort of a semi submerged submarine, they're anchored to the bottom and then the turbine blades are underneath them.”

[10:47] “We are looking at harvesting waves from the persistent ocean currents, especially on the western side of the ocean basins, you get this what's called western intensification, you get very strong currents that are narrow and well defined. The one we know best is the Gulf Stream in the Atlantic. […] And there's a lot of energy there, and it flows all the time. So there's been tests with really large […] title turbines, but they're set partway down in the water column, not as the surface, not at the bottom, but suspended there. So they can take this flow, and then they're anchored in really, really deep water.”

[11:48] “One other really promising technology I'd love to tell you about is known as OTec, or ocean thermal energy conversion. And this is based on heat exchange from warm surface water in the tropics, to cold deep sea water. And the technology is fairly simple, but big. It consists of a very long cold water pipe that brings cold water up and a shorter, warm water pipe that brings it into the plant. You have pumps, heat exchangers, turbans. Then you return the cold water at some sort of intermediate depth, so it's not a temperature shock to the surface water and the animals living there. And then the warm water can just be returned to the surface. There's two major kinds of these OTec cycles. One is called a closed cycle where you use a gas like ammonia to do that heat exchange, and then you just send the water back out. There's also an open cycle where you use the seawater itself to actually cross heat exchanger surfaces. And the beauty of the open cycle is you can also desalinate seawater that way, so you can get fresh water out of it. You can also use the cold water for air conditioning, [and] for other pre-cooling.”

[13:27] “I want to just mention one other technology around tidal devices. And that's a tidal barrage. This is essentially a dam that is built across the mouth of an estuary and then it has turbans in it much like a hydro power down. And so the rise and fall of the tides, it fills the reservoir behind the barrage, and then it empties that through the turbines and means you can generate power on the incoming and the outcoming tides. Something else called a tidal lagoon, it's really similar but it sort of encloses an area of water in a bay that doesn't include the river mouth. So these are really efficient ways to harness tidal energy, you get it all just like a hydro dam. But we're no longer building these in the Western nations because they destroy the estuary, they just take it out of existence. We don't know as much about tidal lagoons because there really aren't many anywhere. We think the environmental effects will be less but we don't know yet.”

[14:41] “Ocean water […] is saline […] and where a river enters the ocean, you get a big difference in salinity. And you can in fact, generate some power through an osmotic process, using a membrane. […] And across that membrane, you do get some electrical conductivity. So you can in fact, use the right kind of membranes and you can get some electricity that way. It's really only useful where you have a big salinity difference, like where a river enters the sea. We have in fact, been researching these much smaller salinity gradients for electrical possibilities. And they don't seem that great. You need pretty big ones.”

[15:50] “I would say the bulk of [the technologies] are in the development testing and early deployment stages. However, we do have commercial projects. The European nations have been further ahead than North America, simply because they got started earlier and put a lot more effort into it. They've actually got several title projects. […] What we are also seeing is the emergence of a lot of small projects and island nations, their small title projects underway in the Philippines and Indonesia, where you may have not the huge tidal currents we see in Alaska or north of Scotland, but enough to supply islands. We are seeing ocean thermal energy conversion projects in Korea and Japan and in the Caribbean. There's one otech project in Japan that's been going for eight or 10 years now. And we […] have very long running OTec projects in Hawaii. And big title projects are starting to be built in Korea, Japan and China. So we're getting there, we're not there. And we are not at what I would call a full commercial industry, but we've got a lot of the sort of hallmarks of it.”

Rating: ⚡⚡⚡

🎙️ Full Episode: Apple | Spotify
🕰️ 25 min | 🗓️ 09/15/2021
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