Seatrec – Thermal Energy Harvesting from the Ocean

In this episode of Ocean Science Radio, inquisitive aquanauts chat with our CEO, Dr. Yi Chao, and Senior Engineer, Michael Zedelmair, about Seatrec’s thermal energy harvesting technology. Our team discusses how phase-change material helps harvest heat and pressure difference in the ocean to generate electricity for drones, research facilities, and possibly even small communities. Tune in to the whole interview with Andrew Kornblatt and Frances Farabaugh. (We also included highlights of the Q&A below.)

Definition of Energy Harvesting

Energy harvesting provides a method of powering electronics in areas where there are no conventional power sources. This includes remote or difficult-to-access locations, as well as underwater where batteries and traditional power deployment are not cost-efficient, practical, or sustainable to use. With energy harvesting, sources such as temperature gradients, light, mechanical load, vibrations, etc., are captured and converted to generate small levels of electricity.

 

Highlighted Q&A:

Challenges of Powering Ocean Drones and Robots Sustainably

Francis: On this program, we have covered a few different types of underwater vehicles and drones. From the incredible and dynamic mapping Sunfish to the anthropomorphic haptic sensor using Ocean One Robot. And that ever-growing international fleet of robots needs to find a way of charging their batteries.

Andrew: Rather than the lengthy process of pulling these robots back into their ship or boats and charging on land or by the boats’ diesel engine, imagine platforms that allow underwater drones to dock and charge on the go using locally and preferably sustainably generated energy.

Francis: Come with us now on an amazing journey to the world of Seatrec, who is doing just that.

Andrew:  Welcome back to Ocean Science Radio, the podcast that brings you the latest, greatest, and sometimes deepest stories in the ocean. I am Andrew Kornblatt, ocean science, and conservation gunslinger.

Francis: And I’m shark researcher, aquanaut, and ocean nerd, Francis Farabaugh. When we think of energy harvested from the ocean, most think about tidal capture – pulling the energy from the motion of the ocean. But the engineers at Seatrec have found another way to pull energy from the ocean through the temperature differential of the different ocean layers.

Andrew: How does that work exactly? Well, first let’s introduce former NASA scientist and CEO and Founder of Seatrec, Yi Chao. 

 

From Caltech-NASA’s Jet Propulsion Labs to Startup

Yi: My name is Yi Chao, Founder and CEO of Seatrec, a startup company based in Pasadena, California.  We spun-off from Caltech NASA Jet Propulsion Labs a few years ago, commercializing the technology we developed at Caltech. Seatrec develops renewable energy technology – we harvest energy from the temperature difference in the ocean, so we can create this energy to power sensors and robotics underwater, which traditionally are powered by batteries with a limited lifetime. It is extremely difficult and costly to change batteries at sea, so we create energy in the ocean to power sensors directly.

Francis:  As we mentioned, the actual method of harnessing energy from the ocean is a big game-changer here.

Yi:  Any time you see a temperature difference, that is the energy you can harvest.  So, if you think about the steam engine, you burn coal to create a 100°C  temperature difference, and with that energy, you can generate electricity.  Our innovation is to use a relatively small temperature difference – it’s about 10° Celsius or 18° Fahrenheit. We use a specific material that responds to the temperature by changing phases and expand the volume, so you basically when you warm up the material, you melt the material from solid to liquid, and then expand the volume to create pressure, and you can use that pressure to spin the motor, and that generates electricity.

Andrew: Many substances expand as they are heated and change phase from solid to liquid to gas. This expansion results in pressure that can be captured and used to generate electricity. Seatrec is developing techniques to generate energy from both the solid-to-liquid and the liquid-to-gas phase transition of several substances.

 

Phase-Change Materials and Thermodynamics

Francis: For more on the mechanics of how this all works, let’s introduce Michael.

Michael: Hi, my name is Michael Zedelmair; I’m a mechanical engineer at Seatrec. Since we’re a very small company, I am responsible for all mechanical engineering for everything we build. What we’re doing is we build a unit that can be attached to any kind of ocean-going robot that dives in the ocean and therefore experiences different temperatures in the ocean. In most parts of the ocean, you have a warm surface, and the deeper you go, the colder the ocean gets. We’re using a material that’s called phase-change material. In our case, it’s pentadecane, which, when it changes phase from a liquid to a solid, reduces its volume, and when it changes back to liquid, volume increases. We use that volume change to create pressure drives a hydraulic system that generates energy and stores it. The pressure differential results out of the volume change and the volume change happens during phase change and the reason why the material changes phase is that pretty much every material changes phase.

Andrew: Alright, Michael, hit me with an example.

Michael: The most simple example is water, which is actually the exact opposite because it changes – it actually expands when it freezes. Most other materials when they melt, they expand, which means when you pass a certain temperature, in our case 10°C, the solid turns into a liquid and expands, and that expansion, when contained in a pressure vessel, generates pressure. So whenever we have a prototype that we want to test in the ocean, we usually tend to go somewhere where it is pretty easy to get into deep waters. We could do all this off California’s coast, but it would take quite a bit to get to deep enough water to do those tests. So we usually go to Kona, Hawaii, the Big Island, because it is essentially a volcano and the shore drops very quickly, and it gets very deep after probably 5 miles out, and that’s where we deploy our units for testing.  

 

Thermal Energy Harvesting in Kona, Hawaii

Francis: Not that anyone really needs an excuse to head to the lovely waters around Hawaii, but the easy access to an ocean dropoff wasn’t the only reason that Seatrec chose Hawaii as a testing ground. 

Michael: We performed those tests in Kona, because, first of all, it’s deep there. You have a warm surface water temperature, and as soon as you get to 400 meters roughly, you pass the 10-degree thermocline, which means we reach the point that we can actually generate energy roughly at 400 meters. And another advantage of Kona, or off the shore of Kona, is that there is sort of a raceway of currents, meaning that if you drop equipment in there and you’re lucky enough, the equipment just does a little loop and comes back to you, so you can pick it up again. Actually, it went pretty good. We really had no major issue, and we got lucky with the weather, which can be pretty bad out there, I mean, anywhere in the ocean, but especially Hawaii since there is really just ocean all around. So, we had a couple of good days, some little choppy days, but overall it’s been a good way to test our units.

Andrew: Michael keeps mentioning the units, so let’s describe what these things actually look like.

Francis: Think about a long plastic tube connected to a cable that transmits the energy produced. The full system is anchored to the seafloor, and the part known as the buoyancy engine module propels the unit up and down in the water column, harnessing the energy from the phase change of the substance therein.

Andrew: Think of those toys that used to come in cereal boxes, the plastic ones when you put them in a closed plastic bottle and squeeze, they would sink to the bottom. A similar image here, but this is taking the pressure and heat differences to generate electricity.

 

The Perils of the Sea

Francis: So these devices have been tested and proven in many places around the world, but not everything goes as swimmingly as their test in Hawaii. 

Michael: There are certainly times when things don’t happen the way you planned it, because you can do tests in a lab, and everything works the way you would expect it to work. But as soon as you’re in the environment and then the ocean, things just happen differently than you would plan for.

We have had several occasions where things didn’t work out the way we wanted to. For example, we had one deployment (not the one that we’ve just been at), where one of the units got in a current and then took off, and it actually drifted into the Maui channel, which is a channel between the Big Island and Maui. And it gets pretty rough there, and so we tried to go out there and find the unit.  Imagine that everything you can see of the unit once you put it in the water is a little antenna. You’re on a boat that’s constantly moving, and all you got is a GPS signal that roughly tells you where the unit is, so you’re looking into that direction you’re on a moving object and that little antenna that is bobbing up and down in the ocean with big waves. So in that particular situation, we were not able to get the unit, so we spent probably 5-6 hours on a rocking boat trying to not fall overboard and couldn’t find anything. So we had to go back, try it again when the weather was not quite as bad. We actually waited until the unit drifted in through Maui channel into the waters that weren’t quite as hostile, and then we were able to get it back, which meant we had to travel, I think, 70-80 miles offshore, which took us pretty much a whole day to get there and to get back.

Those are kind of the little things that can happen. So far, we’ve always been able to recover all of the prototypes that we’re testing, which is pretty essential because all the data that we collect during a deployment is stored on the unit, so we kind of have to get it back to get any information about the sea trials. But sometimes it definitely happens that something just drifts away and you can’t get it back. So far, we’ve been lucky with that.

 

Surface vs. Subsurface (Going Deep with Energy Harvesting)

Andrew: So, what makes Seatrec’s technology unique?

Michael: There is a lot of technology that can extract energy from the ocean like waves or currents, or stuff like that, but the neat thing about the technology that we’re developing is that it works subsurface. If you go below the surface, you’re running out of opportunities pretty quick, because there’s no wind, there’s no solar, and that is actually where most of the, let’s call it, robots –  float, gliders whatever researchers use to better understand the ocean –  that’s where those units are most of the time. They’re not at the surface. You don’t really want to be at the surface because of rough weather or boats running into you. If you think about it this way, you want to generate energy somewhere, not at the surface in the ocean. That’s kind of where we come into play.

 

Ocean Science Radio Commercial Break

Francis: So if you enjoy Ocean Science Radio, you should check out the growing library of podcasts we have at the Speak Up for Blue Network. You’ve probably heard Andrew and me on some other ones like Madame Curiosity or Dugongs and Seadragons.

Andrew:  Let’s hear from one using an old-time radio filter. If you like Ocean Science Radio, why not tune into the marine conservation happy hour. It’s a little like a late-night talk show with alcohol and the latest marine science and conservation issues. Tune into the Marine Conservation Happy Hour twice a week every week. And now, back to our program.

 

Wanted: 10,000 Underwater Robots to Improve Weather Prediction

Francis: According to Dr. Chao, the future is filled with fleets of underwater robots. Seatrec is at the head of a growing market.

Yi: Well, today, there are about a few thousand of the robots in the ocean at a given time.  According to the vision of oceanographers 20 years ago, we need at least ten times more robots than we have today.  Our vision is that with our technology, it is economically feasible and sustainable to the environment to have tens of thousands of robots in the ocean, so we can collect those missing data sets for weather prediction to climate forecasting. We can potentially provide continuous power for those devices to help communication, signal relay to power weather stations in the Arctic, and I’m also reaching out to remote villages in Alaska and Canada. We can potentially help them generate local microgrids and provide electricity for homes and local communities, where it is difficult to use solar power, wind power, or they have logistical challenges to deliver diesel. There are a number of directions we’re exploring in the future – we’re not selling in these areas right now, but we are doing R&D to expand our technology into those spaces.

Francis:  According to Dr. Chao, the applications for this technology, since it is scalable, can really make a whale of a splash, which is why Seatrec has already won two $10,000 prizes under the Powering the Blue Economy Ocean Observing Prize administered by the US Department of Energy and NOAA.

Andrew:  They also got initial seed investing from Breakout Labs and Schmidt Marine Technology Partners. So how did a NASA scientist specializing in satellites get to ocean work?

 

Monitoring Ocean Health without the Power Bottleneck

Yi: That’s an interesting journey. I was trained as an oceanographer studying ocean sciences and got my Ph.D. from Princeton. My first job was working at NASA Jet Propulsion Labs to develop satellites to study the ocean from space/. After 20 years, I ran into this major obstacle.

Andrew:  Dr. Chao’s work has led him to take a long hard look at the problems facing the collection of ocean data and possibly money-making solutions to those problems.

Yi: It can be physical parameters of the ocean, chemistry, or biological parameters. They can be used by oceanographers to study climate change, improve hurricane prediction and weather prediction. We are designing our energy system for these kinds of vertical diving robots.  In the last couple of years, we have been commercializing the technology and the goal of this year’s deployment is to a thousand-meter diving capacity of an energy system.

Francis:  Dr. Chao realized that as amazing as satellite technology is at monitoring sea surface, you couldn’t really get the best imagery and data below the sea surface. We still need to measure how things are working and changing deeper down in the water column.

Yi: Our technology is a way to monitor these changes. One of the biggest challenges is how do you take the pulse of the ocean?  How do you go to the sea and then measure how the ocean changes from the surface to 1000 meters down.  That’s really a fingerprint of climate change. You don’t know how the ocean will respond; you cannot have a reliable computer model to predict future climate change.

In the last decade or so, we have been making major breakthroughs in robotic technology to monitor the ocean conditions, and our technology is taking that step further to scale-up the number of the robots and then the capability of the robots to attach more and more powerful sensors to monitor not only the temperature change and how the chemistry, the biology respond to the climate change as well, so we can address ocean health, ecosystem change, and fisheries, and the other important aspects important to human life.

Andrew: One of the secret issues with ocean exploration and sciences is that while most try to be as sustainable and cost-saving as possible and collect every piece of technology deployed, sometimes, once an underwater vehicle finishes its mission and dies, there isn’t funding, time, or the ability to collect it.

 

 Like Throwing Out Your Tesla When Your Battery Runs Out 

Yi: Today, we use more and more powerful lithium batteries, but they have their limitations as well. They have a limited lifetime. When the battery dies, you’ll have to hire a ship or throw the battery into the sea, so neither is not economical or environmentally not scalable. So in the last 10 years, I have been developing this technology trying to address this challenge to provide renewable energy to power those robots in the deep ocean.

Francis: These super expensive robotic gliders and floating sensor stations monitoring the world’s oceans are sometimes effectively treated as disposable devices, and are therefore sometimes a waste of money, not to mention they’re also contributing to a growing assortment of abandoned lithium-ion batteries. These could be polluting the ocean through leaking toxic materials. Dr. Chao hopes that his technology and what his team is working on can help solve this issue.

Yi: The current practice here is currently not sustainable. Imagine you’re driving a Tesla, and every time you run out of battery, you throw your Tesla away and then buy a new one. You put a Tesla on the roadside; that’s essentially what we are doing for ocean robotics.  We have a number of R&D projects to expand this technology into other spaces.  For example, we are designing a power station in the Arctic ice for the Navy right now. So the Arctic sensor exploration may pretty much rely on diesel generators and deliver diesel with an Icebreaker. As you can imagine, this is expensive, and it is difficult to survive in the winter. So our goal is to harvest energy in the Arctic from the air-sea temperature difference. So there’s very cold in the air, relatively warm in the water, so we potentially can provide continuous power for those devices. 

 

Data, Data, Data – Making a Positive Impact on Our Blue Planet

Andrew: If you ask Michael and Dr. Chao, what is driving them in their work, what really inspires them is a sense of discovery, innovation, and positive impact.

Michael: if we think about the things we know about our planet and we look on land, and we know a lot, I mean you can get anyplace fairly easily, but if you think about our oceans, there’s a saying that, “We know more about the surface of the moon than we know about our oceans.”  It’s actually on the same planet, and that’s kind of crazy, so I’m super excited that we’re developing something that makes it possible in the future to just collect more data to help us understand what the impact is on the ocean on our everyday life on the planet and the whole fisheries. I think I’m pretty lucky to be able to work on something that really has a meaning, and that can make a difference.

Yi: The message I want to convey to your audience is the ocean is mysterious, we know very little about the ocean, we only explore a small fraction – less than 10% of the ocean, and there’s a lot of information we can collect in the ocean through this technology enabled by our technology. We can provide that information at the fingertips of decision-makers and policymakers, and also for researchers, industries to make better decisions to support aquaculture, for example, providing future seafood to the human society and also protect our ocean at the same time. 

Francis: One thing to remember is that this technology is scalable, and the work of Seatrec continues. If you have a project that you need an energy solution, and this podcast makes you go, “Hmmm,” you should reach out.

Andrew: I mean, I just want one. Maybe put together a floating platform with a couple of those Sunfish drones we were talking about?

Francis: Maybe you can power an underwater research laboratory? 

Andrew: They do talk a little bit about powering buildings and powering small villages, and if they can power that much, they can definitely power things like the Aquarius Reef Base.

 

Ocean Science Radio Summary

Francis: A big thanks to our guests who joined us and big thanks to you, our listeners.

Andrew:  Be sure to like, rate, subscribe, and share this podcast with your friends and family.  Until next time this has been another Ocean Science Radio.

 

Ocean Science Radio is a joint project between Andrew Kornblatt, founder and host of the Online Ocean Symposium, and Naomi Frances Farabaugh of FIU.