Bourne Energy's RiverStar: a fresh approach to hydropower

Hydroelectric dams produce little-to-no emissions and draw energy from a renewable resource, but they are still plagued with the inherent problems of all large-scale power plants: they’re costly to build and maintain, land intensive, and have negative environmental consequences. That’s why Bourne Energy believes the future of hydropower, and the solution to global energy demand, is in small generators that harness power from river currents.

Bourne’s RiverStar power modules collect kinetic energy from rivers, passing the water through low RPM turbines that don’t harm aquaculture. The units can be cheaply mass-produced, and require no construction on river bottoms, allowing them to be installed quickly and inexpensively even in areas inhospitable to development. Unlike wind and solar power, which are only as consistent as the weather, the steady flow of rivers is unlikely to alter for up to hundreds of years. The thickness of water compared to air means that the potential energy of the 200,000 miles of major rivers that cover the Earth exceeds what can be gathered from wind turbines.

As a percentage of the world’s electricity, hydropower has grown from 16% in 2003 to 19% in the present day – swamping other renewable sources like solar and wind, which make up less than 1%. It accounted for 6.4% of the US electricity supply in 2005, a higher share than biomass, geothermal, solar and wind energy. Ironically, while the statistics might sound like a glowing endorsement, they instead signalled the end of government funding, with the US Department of Energy calling it a “mature technology” that needed no further sponsored research. However, Bourne Energy believes that if the research is expanded beyond hydroelectric stations to mini-hydro, damless systems, they could together provide up to one-third of the energy consumed by the US.

If potential hydroelectric sources include rivers which would yield 1MW or under, the US has developed only 40% of its total hydropower potential, leaving a further 170 GW available. Similar potential is being exploited globally, with small-hydro installations growing by 8% during 2005. Not all of these are damless, but the concept is gaining ground rapidly. Linda Church Ciocci, executive director of the National Hydropower Association, says: "There's this view that hydropower is a technology that's been around a long time, and there's not much more we can do to improve it - but we've got the next generation of hydropower - ocean, tidal, wave and conduit energy coming on."

Each RiverStar has a generating capacity of up to 50 kilowatts in a 4 knot current. The patent pending RiverStar Kinetic Energy System is a self-contained module that includes a stabilizer, energy absorber, energy transmission and mooring system, and energy conversion and control system. Instead of requiring a dam or reservoir, it harvests hydropower in-river, in interconnected arrays.

An average array is composed of 20 RiverStar units, which can be stacked one after the other down a section of river. RiverStar modules are connected to each other at a depth of ten feet by high strength steel cables. The mooring cables, which are anchored into the shoreline at the same depth, include power transmission and control lines. The turbine drives a proprietary generator module, and is kept stabilized by the cable, the strut, and a rudder that maintains a precise altitude to the river current.

Unlike disruptive hydro-electric dams, which often require the relocation of communities, the RiverStar system can be applied to industrialized, populated sites seamlessly. It can even be beneficial to residents, who may lease out rivers on their land for use by RiverStar. And unlike wind-farms and conventional hydropower facilities, which pose a danger for wildlife, the slower RiverStar turbines present less of a risk and actually repel fish with a slight pressure wave that forms in front of the turbine according to Bourne Energy.

Bourne Energy also has products to harness tidal and wave power. The TidalStar can produce approximately 50 kW at peak capacity, and does not pollute, or affect sediment and water salinity. Like RiverStar, it uses an interconnected array of modules, this time placed across a tidal flow. The system once again saves on infrastructure, and does not require barrages, embankments, caissons, or sluices.

The OceanStar captures the underlying pressure wave through a series of small turbine generators. Several miles of OceanStar arrays can be moored offshore, reducing the force of storm surges upon fragile shoreline areas.

Bourne Energy plans to have small demonstration power arrays operating in Asia, US and Europe within the next 12 months.