Climate tech: can we save the planet while doing sports?

The cost of creating your own wave

For those passionate about surfing, there's a known limitation: you can only surf where there are waves. Even if you're fortunate to live by the ocean, as I did, the waves aren't always consistent. While one day might offer perfect conditions, the next could leave you with still waters. So, what's the solution? Create your own wave!

An artificial solution

This is precisely the approach taken at places like Surf Ranch, where a massive wave travels 2,300 feet. To begin, you need a water body, essentially a rectangular pond. On one of its long sides, there's a rail car with a hydrofoil, a wing-like structure that moves across the water. As it moves, it generates waves. Moreover, adjusting the hydrofoil can tailor waves, ranging from 6 to 8 feet high and traveling at speeds between 10 and 20 mph.

Challenges and their solutions

But what if you're not near a surf park and decide to DIY? Let's sidestep the technicalities and assume you have a lake and can construct a track beside it to push a giant hydrofoil powered by an electric motor. The real concern is: how much will a single wave cost you?

Understanding wave energy

Your monthly electricity bill pays for energy in the form of electric current. By estimating the power required to generate an artificial wave, and considering average electricity prices, we can deduce the cost.

Every wave has kinetic and gravitational potential energy. The kinetic energy is associated with the wave's motion, while gravitational potential energy deals with the wave's height above the water's surface. Given that our wave is triangular, the majority of the water remains near the base with only a fraction at the top. Therefore, the center of mass of this wave would be 1/3 of its height.

Crunching the numbers

Both types of energy are dependent on the wave's mass. Assuming our wave consists of water, with a density of 1,000 kilograms per cubic meter, we can determine the volume and consequently the mass. Using these values, we can compute the total energy of a wave.

In my calculations, a wave traveling at 20 mph would require 16 million joules of energy. To put that in perspective, lifting a textbook from the ground to a table consumes about 10 joules. Meanwhile, a smartphone battery stores approximately 10,000 joules.

If using an 85% efficient electric motor, you'd need 19 million joules to extract 16 million joules for the wave. With the average US electricity price being 23 cents per kilowatt-hour, generating this energy would cost about $1.23.

A gasoline-powered hydrofoil has its own set of calculations. Given the efficiency and costs associated with gasoline, it turns out that the price comes close to that of an electric wave.

Lastly, if you're considering human power, be prepared for some serious effort. You'd be looking at about 89 hours of cycling to store sufficient energy for one wave.

Conclusion

This analysis aimed to showcase how renewable energy can blend the "natural" with the "artificial." In doing so, it can be harnessed for leisure or sports, demonstrating the versatility of clean technology.

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