Wave energy
Wave energy is generally considered to be the most concentrated and least variable form of renewable energy. It is the high-power density of wave energy that suggests it has the capacity to become the lowest cost renewable energy source. The World Energy Council has estimated that approximately 2 terawatts (2 million megawatts), about double current world electricity production, could be produced from the ocean waves.
– Center for Wave Energy.
Wave Potential
A couple of wave farms along a total length of 300 km wave front in the northern part of the Dutch North Sea would receive an annual mean wave energy amount of 300.000m x 15kW/m=4500MW. At a moderate 30% efficiency, this would generate a yearly average of ca. 1350 MW, enough for 3,5 Million households and more than the amount of solar energy that can be generated in the Netherlands.
Energy Distribution
Wave energy has an orbital path and is located mainly at and just below the water surface. It's proportional to the square of the wave height; double wave height = 4x more energy. In our part of the North Sea, the usual wave height for which a device gets designed would lie around 3-4m in area's where the mean yearly wave energy density would lie between 10 and 20 kW/m wave front. In oceans that could be up to 7 0r 8m wave heights and 60-70 kW/m wave front.
Biodiversity
The anchor is 10m marine grade concrete block that can contain air or water. For transport it contains air and gets towed to its destination. There it's filled with seawater and sunk to its final location on the seabed. For maintenance it's filled with pressed air until it floats up to the surface, allowing underwater parts and connections to be inspected and maintained. The anchor proactively enhances marine biodiversity as its structure is suitable for early food chain organisms to attach and develop.
The food chain starts with hard soil as that's needed for small organisms to develop. Ever since the obliteration of hard soil by fishing away most of the boulders and oyster banks, flora and fauna in the North Sea got decimated. At this point, the ca. 3000 ship wrecks start the basic food chain but each wind park that gets protected by a Slow Mill park would add about 30-40 ha hard soil to make flora and fauna in the North Sea flourish and prosper again.
If a wave farm is positioned along the entire northern Wadden Island coast, apart from economic coastal protection and fully sustainable islands, 300-400 ha hard soil is created to enhance marine life.
Field Comparison
A study was done to compare the general features of wave energy and particularly those of the Slow Mill, to other sustainable energy fields. At first inspection it looks like the Slow Mill outperforms most other technologies.
Footprint
The power density of wave energy in the Netherlands also compares favourably to other sustainable energy sources. Whereas solar gets about 150W/m2, winds yields about 600W/m2 and open tidal may reach up to 4000W/m2, Dutch wave energy reaches up to 15.000W/m, hardly needing any surface area. A direct competitor, Wind at Sea, was closer examined as to the amount of space needed for the same amount of energy. A 70 km2 wind farm of 350 MW installed capacity and a utilisation rate of 45% generates an average of 158 MW.
A Slow Mill wave farm, consisting of a single row of 35km length and 0,1 km wide in 15kW/m seas, receives an average of 35.000 x 15=525 MW wave energy. At 30% efficiency (or in case of a double row at lower efficiency 2 x 15%) this is also 158 MW. However, the space needed for this same amount of energy, is 35 x 0,1 = 3,5km2 or 3,5/70=5% of the wind footprint.