Tidal energy vs solar: why one took off and the other didn't

Tides follow a perfect predictable calendar. We know exactly when they'll rise and fall for the next 100 years. Solar depends on clouds and seasons. So why is solar 100× more deployed than tidal?

Tidal: the advantages

1) Predictable to the minute. 2) Energy density 800× higher than wind (water is denser). 3) No storage needed if multiple plants are well-designed. 4) Doesn't occupy farmland. 5) Power available near populated coasts.

Tidal: the killers

1) Capital cost 5-10× more than solar (large submarine turbines, marine install). 2) Brutal underwater maintenance (corrosion, biofouling). 3) Only ~30 sites worldwide have sufficient tides (>16 ft). 4) Marine wildlife impact debated.

Solar: why it won

1) Brutal learning curve: 90% cost reduction in 15 years. 2) Modular: install 1 panel or 1 million with same tech. 3) No moving parts: minimal maintenance. 4) Any roof in the world is a candidate. 5) Allows self-consumption (tidal doesn't).

World tidal plants

La Rance (France, 1966): 240 MW, still operational. Sihwa Lake (South Korea, 2011): 254 MW, largest. MeyGen (Scotland, 2018): 6 MW operational. World total tidal: ~530 MW. World total solar: 1,500,000 MW. Ratio 1:2,800.

When tidal wins

Only in small island countries with big tides: UK (north), France (Brittany), South Korea, Atlantic Canada. And only if solar isn't viable (tiny roofs, extreme latitudes with low insolation). Super specific case.

The future: complementary, not competitors

Optimal energy system combines both. Solar for daytime hours. Tidal for tide hours (predictable). Wind to supplement. Battery for gaps. Each renewable fills a distinct role in the matrix.

More on big solar in world's largest solar plant.