Questions

The designs aim to avoid it. Spiral blades turn slowly with open space between them. Faster units sit behind screens and ducts that keep fish out. We will measure the effect on fish and marine mammals in field trials.

The generators and drivetrains are commercial parts you can buy today. Our development work is the blade shape, matched to each range of water speeds. Full-scale prototypes and lab tests are the next step.

Units are 2 to 10 metres across, depending on the power needed and the water speed at the site. There are six capacities, from 50 kW to 2 MW.

Yes. They fit ISO shipping containers and can be assembled on site in about four hours.

No. A standard assembly line is enough, and the parts and skills are available worldwide. Early units can be built in any fabrication workshop.

Every six months. The generator pod is lifted out and replaced, and the used pod is serviced on land.

Units suit bay entrances, high-tide coasts, ocean currents, offshore wind towers, river banks and walkways, bridges, and irrigation and water supply pipes. The best sites are where water infrastructure meets existing power lines.

By boat in calm weather. A buoy dropped off the stern at anchor shows the direction, and tracking the boat's drift by GPS gives the speed. A hundred metres in sixty seconds is 1.7 metres a second, about 3.3 knots, a common tidal speed and one we prefer.

No. At most sites the units run fully below the surface. In rivers they hang under walkways and bridges.

They sit below the surface and are placed clear of shipping lanes.

Yes. Most cities are on the coast or a river. Making power close to users means fewer new transmission lines.

Far less than solar or wind with the same output, because moving water carries more energy per square metre. Exact spacing depends on water speed and depth and will be set during trials. In a river, units can sit every three to four metres along a bridge or walkway.

Rivers, ocean currents and water pipes flow all day. A tidal site flows for about 20 hours in 24, with a short pause each time the tide turns. Units at several tidal sites along a coast cover each other's pauses, so an array can supply power around the clock. That is two to four times the running hours of wind or solar.

Small units sell at list: US$350,000 to 400,000 for 50 kW, US$450,000 to 500,000 for 100 kW and US$800,000 for 250 kW, each with a yearly service fee. Over ten years that is half or less of the diesel they replace.

Data centres and cities buy 500 kW and 1 MW units at US$5.0 million per megawatt for the first 50 MW, stepping down to US$3.5 million per megawatt after 200 MW. The planning build cost of a 1 MW unit is about US$1.21 million.

Leased power is priced under the buyer’s next cheapest firm option: US$100 per megawatt hour to cities and data centres, against on-site gas engines at about US$107, and US$150 to islands, against diesel power at about US$300. The supply runs day and night without batteries. Field trials will test these prices.

Tidal power is proven. La Rance in France has run since 1966. Most current designs are large machines that need fast water. Their many moving parts make them costly to build and maintain. AFE builds small units from stock parts that work in slower water.

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