In Canada’s Nova Scotia, the difference between tides at the Bay of Fundy is the world’s highest. The province’s southwest shore has low tides, with heights reaching 3.5 feet at most. At the head of the bay, the situation changes dramatically. Tides reach as high as 53 feet. Ideally, the difference in tide sizes should make Nova Scotia a powerhouse in tidal energy.

That was the expectation in 2009, when Nova Scotia launched its first tidal energy project. Nine years later, however, it is still struggling to install tidal energy as a viable source of energy for its communities.

Nova Scotia’s case is not an isolated instance. For the most part, similar problems are being experienced at other locations which are planning to use tidal energy as a source of electricity. Water is more dense as compared to air, which means that the amount of energy extracted per unit is more. That should make tidal energy attractive to renewable energy developers and policy makers. But tidal energy is yet to catch on. Till date, there are only five tidal power plants in the world.

There are two reasons why tidal energy is yet to take off as an economically sustainable form of renewable energy.

The first one is the high cost associated with generation of tidal energy. Equipment is expensive as are the additional costs for laying connections to the electric grid and infrastructure for smooth functioning and transfer of energy systems. The world’s biggest tidal power station in South Korea cost $560 million in 2011 and has a capacity of 254 MWh. Those costs haven’t come down. The Swansea Bay Tidal Lagoon in the UK is estimated to generate 530 GWh per year and will cost $1.6 billion. Based on calculations from this article, that translates to electricity generated at a whooping 19.7 cents per KWh.

A report from the World Energy Council and Bloomberg New Energy Finance (BNEF) estimated that electricity generated from ocean movements cost eight to nine times as much as the highest average price for wind energy in Europe. Closer home, ratepayers who chose to use electricity generated using tidal energy in Eastport Maine paid three times more in costs as other ratepayers in the same region back in 2016.

The high costs have ensured that the market for tidal energy has moved in fits and starts and the electricity generated using this form of energy remains expensive. Naval Energy, a leading renewable energy company from France, pulled out of Canada’s tidal energy market, stating that the market for it had deteriorated. According to the company, this is reflected in “a lack of commercial prospects (for tidal energy) over the long term.”

The second reason for tidal energy’s unpopularity is fears over its effect on ecological systems. There are two ways in which tidal energy can be produced: a hydrokinetic approach and a barrage approach. As the name indicates, the latter approach requires the construction of a large structure, such as a dam, to convert water’s kinetic energy into electricity. This is the approach which has been used at the Sihwa Tidal Power Station in South Korea. But the chances of it being replicated in other countries are slim because of conflicting evidence about the seemingly adverse ecological and social impact that dams have. The technology and equipment for the second type of tidal energy is still unproven. For example, turbines in Nova Scotia’s initial experiment 2009 broke because the designers had underestimated tide velocity. There are also fears in the province that it turbines could adversely affect the population of lobsters, which are a source of revenue for fishermen there.

What Is The Future For Tidal Energy?

As of this writing, the market for tidal energy seems pretty limited and it is expected to remain that way in the near future. The United States’ Department of Energy has made a grant of $20 million in funding for wave and tidal energy projects this year. In 2012, the federal agency estimated that waves and tidal current could produce approximately 1420 TWh of power per year. But this year’s estimate puts an estimate for power produced using tidal stream resources at between 220 TWh to 330 TWh per year.

To be sure, tidal energy is beneficial for regions that are near a coast and have the necessary conditions (a difference between low and high tides of, at least, 5 meters) to make this novel form of energy cheaper. To make the economics work, however, tidal energy producers will have to contend with riders. For example, PPAs in Nova Scotia transfer risk onto the producers rather than ratepayers. If the producers fail to deliver power per requirements, the ratepayers can cut off payments to the power producer Effectively then, ratepayers only pay for the duration that power is produced.