Advantages of Tidal Power
One of the bigest advantages of tidal power generation schemes is greenhouse gas emissions. Though there is some release of GHGs during construction of tidal generators, once they are in operation there are no further emissions. Of course, greenhouse gases are but one of the many advantages to be had from tidal power. We look at the advantages common to all tidal power schemes and then focus on benefits that are specific to certain types of tidal power.
Greenhouse Gas Emissions and Tidal Power
As was pointed out, once a tidal power scheme is in place and functioning, it creates no greenhouse gas emissions at all and because the systems are being designed to run for 30 or more years without replacement or major routine maintenance, the impact of the initial build is easily mitigated.
Concrete is one of the two primary sources of carbon dioxide emissions. In fact, the entire industry is responsible for about 5% of all CO2 emissions. Because concrete is a major component of barrage-type tidal power schemes, these systems have the greatest greenhouse gas impact. However, the impact occurs only once in the lifetime of the system and because no emissions are generated by the production of power from barrage systems, the debt is quickly paid back. By some estimates, the carbon debt incurred by building a large barrage scheme, like the one proposed for the Severn Estuary, can be paid back in as little as 6 months which is a huge advantage over other renewable energy schemes.
This only takes into account the equipment emissions, transport of materials, and production of materials. What it does not take into account is changes in the ecosystem that result from installation. While these changes are estimated to have little impact on greenhouse gas emissions, only future analysis can determine if that estimate is correct. For the time being, tidal power systems seem to have very limited greenhouse impact. Systems other than barrages are likely to have even less GHG emissions.
Renewable and Efficient
Another advantage is that it is estimated that tidal power will be useful to humans for at least 2 billion years, making tidal power as renewable as wind and solar. The only major problem facing these systems is maintenance over the long term.
Tidal turbines are very efficient because they are based on the same designs (in many, but not all cases) that have been used in hydro and wind projects for decades. At 80% efficiency, these systems are roughly twice as efficient as the best solar panels that are still in the research phase and anywhere from two to four times more efficient than wind turbines.
Unlike wind and solar, the tides are predictable and constant. In fact, barring any major disaster, like an earthquake, the tides can be predicted hundreds of years into the future. The reliability of tides solves one of the major impediments to the large-scale adoption of wind and solar, which is generating power when the wind isn’t blowing or the sun isn’t shining. Because the tides are predictable, we can ensure a relatively steady power supply so long as the system is designed correctly.
The cost of a tidal power system is a double-edged sword. The initial costs are extremely high, higher in fact than just about any other power generation scheme yet conceived. On the other hand, however, the systems are nearly maintenance free over life spans of 30 to 40 years. Such low operating costs mean that, over the long term, electricity produced by tidal schemes is less expensive than any other form of generation. So, even though startup costs are high, the long term financial benefits of tidal power are substantial.
Beauty is in the eye of the beholder, so this particular criterion is debatable to say the least. Nevertheless, most people agree that tidal power systems are less of an eyesore than most other power generating systems. In fact, other than tidal barrage systems, most tidal power systems are completely submerged and thus not seen or heard by humans.
Advantages Unique to Barrage Systems
Barrage tidal schemes offer two unique advantages that no other tidal scheme offers. First, barrage systems can protect coastal towns and ports from flood. Because a barrage is nothing more than a dam with some turbines incorporated into it, it can be used to control the flow of water into the estuary, bay, or river mouth.
The second advantage to a barrage system is that it can usually double as a bridge or other connection route. So, you not only get power generating capabilities from the barrage, but you also get a transportation scheme as well. The advantage is further enhanced by the fact that maintenance is now on a single structure, rather than on say a bridge and a power plant. This means reduced overall costs to taxpayers.
Advantages of Tidal Stream Generators
Tidal stream generators are probably the most eco-friendly of all tidal power schemes. They are carefully designed to avoid injuring marine wildlife and, so far, have shown no appreciable impact on the environments in which they are installed. The problems of silting, trapped wildlife, and landscape/seascape changes associated with barrages are not seen with stream generators.
The other advantage of tidal stream generators is that they operate at all times. Barrage systems often operate only at low tide as they let water exit through the turbines. This means they only generate intermittent power (for about 12 hours per day in most cases). Because tidal stream generators can be designed to work no matter what direction the tide is flowing, they can generate power up to 20 hours per day, making them more practical as standalone systems (rather than the supplemental role that barrage systems have so far played).
Advantages of Dynamic Tidal Power (DTP)
Thought DTP has not been tested, the theoretical advantages are numerous. First and foremost, DTP systems are large enough to generate massive amounts of electricity. These systems are technically capable of generating multiple gigawatts of power at all times where as barrage and stream generators are usually rated at a few hundred megawatts at best.
The second advantage of DTP is that like tidal stream generators, DTP systems work regardless of which way the tide is flowing. These systems should be able to generate power for 20+ hours in a day if properly designed.
DTP also benefits from the fact that it doesn’t enclose any area and so, theoretically, should be immune to the problems that barrage systems create such as silting and changes to sensitive estuary ecosystems. Of course, migratory patterns of fish and other wildlife may be altered by DTP systems, but such effects can only be tested when a DTP system is installed.
There are a number of advantages to tidal power that make it an attractive option for a power-hungry world faced with serious problems by its current power generation schemes. Like any human innovation, however, tidal power is not without impact. Responsible use and careful consideration of environmental impact can and will guide productive and safe use of tidal power moving forward. Tidal power is not a silver bullet, but it can become part of the human repertoire of low impact, environmentally friendly power generation schemes.