The City of Hastings in Minnesota, USA will soon have a two-turbine Hydro+ project downstream from the city’s 4.4 megawatt (MW) run-of-river hydropower plant.

Located on the Mississippi River, the Hydro Green Power equipment will generate up to 250 kilowatts (kW), representing a 5.7 per cent increase in renewable energy generation at the existing site. Hydro Green’s technology is the first surface-suspended system in the industry.

Hydrokinetic power refers to the generation of electricity from moving water without impoundments or diversionary structures that are typically used at conventional hydropower facilities. Hydro Green’s technology operates in open rivers, tidal areas and oceans. The surface-suspended technology operates without having to first construct dams or impoundments and can be deployed downstream from existing hydropower facilities – known as Hydro+ – allowing for new, clean power generation within the existing project’s footprint.

The hydrokinetic power turbine arrays are composed of a modular, interchangeable, zero-head, current-based turbine. The nameplate capacity of the design is 250 kW per unit with a rotor diameter of 3.6 metres. Due to the surface suspension system, there are also operational maintenance and safety advantages.

An on board gantry allows for the raising and lowering of individual generating units in the hydrokinetic turbine array without having to conduct underwater diving and maintenance operations in extreme water velocity and near zero visibility conditions. The floating raft provides a platform for operation and maintenance workers to stand on and place equipment during activities. In a tidal energy setting, this advantage becomes even more pronounced since all maintenance activities typically occur within a 15–30 minute slack tide. From an underwater diving standpoint, the short operational window during the slack tide significantly increases the risk of injury to the divers and the potential loss of equipment.

The company said the advantages of current-based hydrokinetic power systems include:

• High capacity factor (~90+ per cent) - for in-stream river and ocean-current applications
• Predictable, base load power
• Maximum net energy from in-stream - river and ocean-current energy applications
• Peak power generation in tidal energy - applications
• Large projects to consist of metal - construction
• Small projects to consist of reinforced - plastic construction
• Scalable to large power generating - stations (100+ MW) – utility scale power.

The Federal Energy Regulatory Commission (FERC) approved the project in December, authorising the installation of the first turbine in Hastings. Once the electrical systems are tested, the hydrokinetic turbine will send renewable electricity to the electric power grid. The installation of the second turbine is scheduled for the second quarter of 2009. The National Hydropower Association (NHA) Executive Director Linda Church Ciocci said the proposed addition of hydrokinetic turbines to the existing hydropower facility “represents a tremendous step forward on the path to commercialising the nascent instream hydrokinetic power industry.”

In a submission to FERC, NHA cites Electric Power Research Institute estimates that 13,000 MW of potential is ripe for development by 2025, utilising new advanced technologies in the ocean, tidal and instream hydrokinetic sector. However, NHA believes that this potential will not be fully realised until the USA adopts necessary economic, regulatory and research and development policies to support this growth.

Ms Church Ciocci said “The Hydro Green turbines in Hastings are on the vanguard of clean energy technology, and they represent the first step in what will be a long line of applications that will expand – and one day double – America’s largest renewable energy resource.”

Following tests, the company began sending power to the grid in February.