Tidal energy is a form of power generation that is created as the tides and the currents of the ocean rise and fall. It is a renewable energy resource, since the tides come and go naturally, though some fossil fuels are consumed to create the paddles and turbines that are used to create the energy.
In areas where there is a significant difference between low tide and high tide, electricity generation can be plentiful. The largest facility in operation right now is the Sihwa Lake Tidal Power Station in South Korea.
The United States does not have any tidal energy plants, nor are there many suitable locations to install them.
Here are the pros and cons of tidal energy to consider as we look at ways to wean ourselves off of fossil fuels for electricity generation.
List of the Pros of Tidal Energy
1. It is a climate-friendly form of power generation.
Tidal energy does not produce any emissions once the equipment has been created for power generation. That means the amount of time it takes to achieve a net savings is very low, even for a large complex. Some facilities can see net emissions savings being in 5 years or less. At the same time, a tidal energy complex takes up a minimal amount of space and does not interfere with the natural behaviors of the oceans.
2. It is a renewable energy resource.
As long as the Earth continues to rotate and as long as the moon orbits, there will be tides. Gravitational fields create water movement around the planet and this is what generates the power when looking at tidal energy. Once the investment into collection materials is made, the energy produced by the tides will be converted into electricity as long as the installation remains active.
3. It offers a predictable energy resource.
Many forms of renewable energy are somewhat unpredictable. Solar can be disrupted by an overcast day. Wind energy can be disrupted because winds are too weak or too strong for the turbines to process it. Tidal energy, however, works on cycles that are tracked and predictable. That makes it possible for each installation site to receive the customized construction that is necessary to maximize the energy potential that is available.
4. It offers huge rewards for small movements.
Did you know that the density of the water in our ocean’s is about 1,000 times higher than the density of the atmosphere at sea level? That means tidal energy can generate electricity at very low water movement speeds. At the average tidal energy facility, movement levels of just 3 feet per second can generate enough power to spin turbines for power generation. For comparison, water movement speeds along rivers that are dammed for hydropower may move as fast as 23,000 feet per second.
5. It has a longer effective life than nuclear power plants.
When they were constructed, the expected lifespan of nuclear power plants in the United States was about 40 years. According to Scientific American, those plants are expected to last another 50-70 years beyond that expected life cycle. Tidal energy provides a longer effective lifespan than that without the danger of a meltdown. The first tidal energy plant was installed in 1966 and is still in operation today, generating the same levels of electricity that it did in its first years.
6. It is a highly efficient form of energy production.
The average coal-fired power plant achieves an efficiency rating of about 30%. Clean coal plants improve that rating to about 50%. Many forms of renewable energy are in the 70% range for efficiency. Tidal energy, however, comes in at an 80% efficiency rate. We are able to convert a vast majority of the useful energy found in the water movement to electricity.
7. It has low maintenance and operational costs.
When installation costs are excluded from tidal energy installations, the operational costs are incredibly low. In some locations, there are as little as $0.02 per kilowatt hour. That makes it one of the most affordable forms of energy that we can access using current technologies.
List of the Cons of Tidal Energy
1. There may be unintended environmental consequences.
Tidal facilities have been operating for more than 50 years without environmental impact. That doesn’t mean this trend will continue. Adding more facilities along shorelines may impact how beaches operate, how marine life interacts with the shore, and other impacts that we may not know about. The reality of tidal energy is that it is still an emerging technology and we may still have several issues that need to be resolved to make it something that is safe to use.
2. There are limited installation points.
Tidal energy facilities must be located close to land, so the electricity that is generated can be distributed to the general network. They must also be located near a shoreline that has dynamic tidal energies to be effective. In the United States, only a handful of regions display the potential for being a good site for the first U.S.-based tidal energy plant. That includes Puget Sound in Washington and Cobscook Bay in Maine.
3. There are high capital expenses to consider.
The estimated cost of installing an 8,000-megawatt facility in the Severn Estuary in the United Kingdom is $15 billion. Even a facility that would produce about 2,200 megawatts as a tidal fence in the Philippines comes with an estimated price tag of more than $3 billion. The fact is that tidal energy is still an unproven commodity. The largest plant in the world today only generates an average of 254 megawatts per year. The Kislaya Guba Tidal Power Station in Russia, commissioned in 1968, generates just 1.7 megawatts of energy.
4. There may be impacts to the regular tidal cycles.
Tidal energy must be collected for it to be used. That means the energy of the tides must be harvested. That process could reduce tidal movements in certain locations, which would have a rippling effect on the shorelines of the entire region. It may result in more debris washing up on beaches or it could cause more debris to remain in the water as an obstacle for boats. It may also change the structure of tidal flats that are used as a habitat by marine life and birds, depending upon the tide present.
5. There may be changes to salinity.
Harvesting the energy of the tides is also known to alter the salinity of the water in that region. Changes to water salinity could impact marine life in a number of ways. It may even cause certain regions to become barren. That is why the United States is testing tidal energy in the Puget Sound region. The goal is to learn how any salinity changes, or the presence of tidal energy equipment, may impact local marine life.
6. There is the possibility that it would be a non-continuous energy resource.
There are regular tides that come in and out. Then there are large tides that occur 1-2 times per month in many locations. These “King Tides” are naturally occurring events that are predictable and only occur a few times per year, although it could still be devastating to the power generation capabilities of a tidal energy plant. The erosive power of a King Tide is well-known. It may also expose the equipment to potential damage. At the very least, some tidal movements may cause the power plant to be non-continuous when the tides are too low.
7. There is a persistent threat of corrosion.
Tidal energy converters must be placed in water with high salinity levels in most locations for this technology to be effective. That means there is a constant threat of erosion to the equipment being used. There are many corrosion-resistant materials that can be utilized for tidal energy, though “resistant” is not the same as being “corrosion-proof.” There are low maintenance costs associated with tidal energy, but we must also consider the costs of corrosive elements leaking into our oceans and what it would take to clean that up.
8. There is the risk of damage always present.
Tidal energy is often collected in regions where shipping traffic may also be present. Buoys, markers, and lighted indicators are used to indicate the location of the facility to prevent damage. If those markers were to be damaged for some reason, there is the possibility that boaters or swimmers could encounter the facility and not realize it. Not only could that damage the equipment, it could be a life-threatening encounter.
These tidal energy pros and cons show us that there is a world of potential with the motion of our global waters. The tides can be used to produce electricity, but the costs of doing so may be too much right now for many to think about using it. It is a proven idea, so our job is to innovate. As technologies improve, tidal energy could be cheaper, faster, and easier than other forms of energy.