THE CASE FOR TIDAL
How tidal energy stacks up against other clean sources, and why it’s essential for the energy transition
Written by Brad Fletcher
February 21, 2024
“Ah, yes. Tidal energy. The flying cars of the utility world.”
Chatting with the Head of Strategic Services for the Homer Alaska utility company, he explained to me that he’d been contacted dozens of times over the years about developing the tidal resources in and around Homer. The Cook Inlet in Alaska has some of the highest tidal variance in the world, and many starry-eyed developers have been eager to harness that power into electricity.
But in his mind it was like flying cars. Hung on his wall were various covers of science magazines from over the years talking about flying cars. He called it the “oft-promised but never delivered” technology, and he considered tidal energy to be analogous, since up to that point, no attempt had really been successful.
But now it’s 2024. The world at large is in the throes of the Energy Transition—moving away from fossil fuels in favor of clean, renewable energy. The world’s tides have been estimated with the capacity to supply up to a third of global energy needs. Can we afford for this aquatic flying-car-equivalent to remain a cozy yet unfulfillable fantasy?
Comparing to Other Clean Energy Sources
In the quest for sustainable, emission-free energy sources, there are few that stand out more than wind, solar, and nuclear power. Though all three have their merits, and a firm place in the energy transition, let’s talk about why tidal energy ultimately presents a more promising path for our renewable energy future.
Predictability and Consistency
Probably the most significant advantage of tidal energy over wind and solar power is its predictability and consistency. While forecasting methods are improving for wind and solar which allows us to reasonably estimate how much power can be generated over the course of a year, the day-to-day and especially hour-by-hour predictions are severely lacking.
Tidal patterns, on the other hand, are governed by the gravitational forces of the moon and the sun, meaning we know where the water level will be days, months, and years in advance; and we can get pretty close estimates up to decades ahead of time. This means a clean energy grid can be built entirely around tidal output.
Economic Viability
The predictability of tides is key to its economic viability. With technological advances, the price per MWh (megawatt-hour) has dropped significantly for wind and solar, mostly putting them in the $35-$40/MWh range. That looks very attractive when compared to tidal, at $64-$68/MWh—until you look under the hood.
Wind and solar can produce power at that low cost for as long as their power input doesn’t actually matter; as long as the grid is mainly powered by fossil fuels. Attempting to make wind and solar primary power providers would mean that they would need to be backed up by rapid response systems, which means batteries. Once you add in the cost of batteries, the price of wind & solar doubles, triples, or even increases 10x in some cases.
Nuclear power is a different story altogether. Nuclear doesn’t need batteries, but is very expensive regardless. Costs can range from $80-$100/MWh.
If we’re serious about the Energy Transition, even a hybrid one; wind, solar, and nuclear cannot be the primary power sources without sacrificing everyone’s energy bill in the process.
Longevity and Durability
A downside to the economics of tidal energy is the high upfront cost. These are similar to nuclear, although lower, but much higher than wind and solar. But this is tempered by the ridiculously long lifespan of tidal energy plants.
Nuclear plants typically last 40-50 years, while wind and solar are around 20 years. All require regular costly maintenance and updates. Add in the energy storage (read: batteries) needed for wind and solar, which last 10 years at the most and are very expensive, then you start to see why wind and solar costs are 10x higher in reality than they’re portrayed to be.
Tidal plants, in contrast, can last up to 120 years. The $65/MWh drops down to $50 after 20 years, and the operation and maintenance needs are very low and inexpensive. So while upfront costs may be high, taking a long-term outlook makes tidal economics extremely compelling.
(If only someone could design a tidal system that slashes those pesky upfront costs… Stay tuned…)
Environmental Impact
When it comes to how they affect the land, environment, wildlife, and other ecological considerations, there’s really no contest.
Wind and solar farms, both onshore and offshore, require large expanses of land and can impact local landscapes and wildlife habitats. A tidal plant that has 1200 MW of capacity built using Nestar’s system would span 12 km long and 4m wide–the total footprint comes out to just under 12 acres. A solar farm with similar capacity would be more like 15 square miles. A comparable wind farm ends up around 60 square miles!
And nuclear? Well, it generates radioactive waste that requires secure storage for up to a million years. Not a joke. Additionally, the process of uranium mining and fuel processing poses significant environmental risks. And, although safety measures have improved, the potential for catastrophic failures, as seen in Chernobyl and Fukushima, casts a long shadow over nuclear’s environmental credentials.
Plus, new developments in tidal energy allow for marine life to pass around and through turbines without injury, and innovations in water sequestration have eliminated the sedimentation, silting, and water quality problems associated with tidal plants of the past.
Efficiency and Energy Density
Energy density is the amount of energy stored in a given system or region of space per unit volume. Efficiency is the percentage of energy that a system captures, relative to how much total energy passes through it.
Hydropower, the energy behind tidal power, is the most energy-dense renewable resource. Nuclear is similar. Both are far superior to wind and solar.
Water is over 800 times denser than air, which means that even slow-moving tidal currents can generate significantly more energy and at lower speeds than wind turbines. This makes tidal energy installations vastly more productive per square meter than wind farms, especially in areas with strong tidal currents.
And solar comes in last on this one, with around 18-22% efficiency, compared to wind’s 60%.
The Merits
This isn’t to say that these other forms of clean energy are without their merits. Wind and solar systems are significantly cheaper to install. They also have a much higher potential energy threshold. This leads them to be favorable for individuals, families, and small businesses wishing to install their own clean energy systems.
In nuclear power, although the pace of innovation is slow compared to renewable technologies, advancements such as small modular reactors (SMRs) offer hope for safer and more efficient nuclear power in the future.
Discoveries and innovations in battery energy storage systems are promising, and may eventually allow the cost of backing up wind and solar systems to not be so exorbitant.
Conclusion
The truth is, flying cars DO exist. They’ve been around for almost 90 years. They just don’t look exactly the way people would like, and they go by a different name: Helicopters.
Maybe the energy transition doesn’t look exactly the way we’ve envisioned it either. It would be nice to just put a giant solar panel satellite up in space that generates enough power for the whole planet, and simply ship it back down to earth. While that would be cool, and may be possible, it’s not happening any time soon. But there’s no time for dilly-dallying. It will take a large and concerted effort on all fronts to truly make this happen. To truly pull off the Energy Transition in a way that preserves the planet and works for everyone, we will need all the help that we can get.
Due to the economic benefits, the environmental friendliness, the small footprint, the efficiency, and the longevity of tidal plants, it’s time for tidal energy generation to truly have its day in the sun. Or rather, in the water.
In order for the grid to truly rely on clean energy sources for base load power, without compromising people’s utility bills, the reliability of their electricity, their usage, or the environment, we need more than wind, solar, and nuclear. We need the ocean. We need tidal energy.
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Nestar Energy has developed a system for tidal power generation that reduces upfront costs by up to 80%, eliminates ecological and environmental concerns, and is capable of supplying a third of global electricity demand. Reach out to find out more!
Citations:
https://www.energy.gov/eere/solar/articles/success-story-novel-approach-solar-forecasting-delivers-improved-reliability
https://www.nrel.gov/grid/solar-wind-forecasting.html
https://ntslf.org/about-tides/tides-faq
https://www.eia.gov/outlooks/aeo/pdf/electricity_generation.pdf
https://www.eia.gov/outlooks/aeo/pdf/electricity_generation.pdf
http://euanmearns.com/the-cost-of-wind-solar-power-batteries-included/
https://www.iaea.org/sites/default/files/29402043133.pdf
https://www.statista.com/statistics/1229935/lifetime-power-plants-energy-sources-globally/#:~:text=Global%20lifetime%20of%20energy%20sources%20and%20power%20plants%20by%20type&text=The%20lifetime%20of%20an%20average,storage%20last%20roughly%2010%20years.
https://oyarenewables.com/resources/solar-farm-requirements-everything-you-need-to-know/?doing_wp_cron=1708376148.3795540332794189453125#:~:text=In%20the%20case%20of%20a,a%205%20MW%20solar%20farm.
https://www.landgate.com/news/does-my-land-qualify-for-a-wind-farm-lease#:~:text=Acreage%20Required%20for%20a%20Wind%20Farm&text=One%20wind%20turbine%20can%20require,on%20much%20of%20the%20land.
https://www.forbes.com/sites/christinero/2019/11/26/the-staggering-timescales-of-nuclear-waste-disposal/#:~:text=High%2Dlevel%20nuclear%20waste%20consists,up%20to%20a%20million%20years.
https://www.nature.com/articles/s41598-022-25341-9#Sec17