Focusing on the Next Generation of Hydropower Technology

By Gregory B. Poindexter

The U.S. Department of Energy (DOE) has released its “Quadrennial Technology Review: An Assessment of Energy Technologies and Research Opportunities” (QTR). According to DOE, the 505-page QTR examines the status of the science and technology that are the foundation of the U.S. energy system, together with the research, development, demonstration and deployment (RDD&D) opportunities to advance them.

DOE says the review focuses primarily on technologies with commercialization potential in the midterm and beyond. It frames various trade-offs that all energy technologies must balance across such dimensions as cost, security and reliability of supply, diversity, environmental impacts, land use, and materials use. Additionally, it provides data and analysis on RDD&D pathways to assist decision makers as they set priorities, within budget constraints, to develop more secure, affordable, and sustainable energy services. Policies and regulations are examined separately by the Quadrennial Energy Review.

A portion of the QTR identifies technological and social considerations the hydropower industry must understand with regard to undeveloped hydropower.

More than 3,000 utilities comprise the U.S. electricity generation industry, and hydropower provides 7% of annual total U.S. electricity, according to government data. Federal agencies own and operate about half of U.S. hydropower capacity. Investor-owned utilities, state and municipal utilities, and independent power producers own and operate the remaining half.

In a challenging financial environment that is experiencing declining retail rates for electricity and increased regulation to produce clean, renewable energy, how can these hydro plant owners increase operating efficiency and economic gain?

Highlights from the QTR show how hydro could increase its presence in the U.S. sustainable energy mix. The report enumerates opportunities for research, identifies market challenges and provides a future outlook for the hydro industry.

QTR hydropower assessment

From 1949 to 2013, on average, hydropower has provided 10.5% of cumulative U.S. power sector net generation. As of 2014, with 78 GW of installed conventional hydro capacity and 22 GW of pumped-storage capacity, hydropower provided 47% of all U.S. renewable power sector generation.

Market challenges

U.S. hydropower development and operations are intertwined with water resources development and management, which presents unique deployment challenges among renewable energy sources. Hydropower is evolving from energy production to include emphasis on species protection and restoration, drinking water considerations and navigational and recreational uses.

Large-scale pumped-storage development could positively affect the market, but the absence of market signals and assured revenue streams have muted financial investment. Hydropower development requires site-specific design, permitting, construction and commissioning processes, which nullifies cost-reducing standardization and guaranteed development. Addressing siting, permitting and environmental concerns results in long planning cycles and time to deployment.

Technology challenges

The age of large-scale hydro development in the U.S. has long since passed, and the potential hydropower that remains comprises small-scale development opportunities. Advancements for small-scale turbine-generators must reduce technology cost and enable more compact support structures and smaller physical and environmental footprints to achieve economic feasibility.

Factors driving change in hydropower technology

Environmental impact mitigation remains the overarching factor that drives hydropower technology advancement. Continued operation of existing facilities and new deployment will depend upon demonstration and acceptance of environmental mitigation technologies for facilities of all sizes – within and external to the turbine. Future drivers for hydropower and water storage could be the impacts of climate change, with potentially increased water shortages – especially in the western states.

Opportunity exists to add up to 12 GW of capacity to existing non-powered dams, and there is about 65 GW of undeveloped stream-reach potential in the U.S.

According to the National Hydropower Asset Assessment Program, “The New Stream-reach Development Resource Assessment (NSD) project uses an innovative geographic approach to analyze the potential for new hydropower development in U.S. stream segments that do not currently have hydroelectric facilities.”

The 2015 Quadrennial Technology Review
The 2015 Quadrennial Technology Review

NSD is one among other types of untapped hydropower potential, such as non-powered dams, existing hydropower facilities, pumped storage and small conduits. The NSD project considers “new stream-reach development” (assessments conducted for the conterminous U.S.) and “new site development” (assessments conducted for Alaska and Hawaii) distinct from the other hydropower resource classes identified by the DOE Water Power Program.

Much of this potential capacity will require low-cost turbines operating at less than 25 ft of head. Small hydropower technology must become less expensive to manufacture, install and operate if it is to see widespread deployment. Traditional powertrain, powerhouse, dam and reservoir designs could be unacceptable for this application because they have footprints that may be too expensive, with too many environmental impacts.

Hydropower technology RDD&D opportunities

With technology innovation, cost reductions and favorable market mechanisms, hydropower could substantially contribute to reducing criteria pollutants and lessening CO2 emissions as a substantial part of the U.S. power portfolio. Design, siting and operation also need to take into account potential changes in precipitation and evaporation as a result of climate change. RDD&D can help sustain and enhance existing hydropower capabilities and achieve a market-competitive levelized cost of energy (LCOE) for new hydropower development in the following four areas:

Integrating environmental mitigation technology into turbine designs

Environmental performance optimization requires advanced computational models of flow dynamics, fish kinematics and gas transfer within turbine flow passages, as well as laboratory and field scientific experiments to inform those models. Such design tools will require advanced physics-based turbulence modeling and will need high-performance computing power to incorporate fish passage and water quality objectives into the turbine design process.

Advanced powertrains

Innovations can reduce direct costs of low-head turbine components, as well as reduce the physical footprint of small turbines that influence overall costs and environmental impacts of low-head hydro development.

Market acceleration and deployment

Opportunities exist to reduce the cost and duration of market barriers, including fish and wildlife protection, environmental issues and multiple-use concerns such as navigation and water supply.

Potential market barrier technology solutions include:

  • Standardized technology packages and site civil layouts to reduce the uncertainty and complexity of environmental and safety reviews for new development; and
  • Decision support tools, which integrate fish passage, water quality and other environmental objectives more robustly into hydroelectric and power system scheduling.

Advanced grid integration

Large-scale studies of power systems can include hydropower and pumped-storage facilities as some of the solutions to integrate variable renewables into the grid. The capabilities and operational constraints of existing and future hydropower technologies must be accurately represented in such studies and within the operational and planning models that electric utilities and other stakeholders rely upon for decision making. Further, the impact of altered operational strategies for hydropower will have operations and maintenance (O&M) impacts and costs that must be projected as part of decision making and O&M planning.

MHK technology

Marine and hydrokinetic (MHK) technologies convert the energy of waves, tides and river and ocean currents into electricity. With more than 50% of the U.S. population living within 50 miles of the nation’s coasts, MHK technologies hold significant potential to supply renewable electricity to consumers in coastal load centers.

MHK resource assessments identify a continental U.S. technical resource potential of as much as 538 to 757 TWh of annual generation. For context, about 90,000 homes can be powered by 1 TWh of electricity generation each year.

Major challenges

The major challenges to commercial deployment of MHK technology in the U.S. include:

  • Capital cost reductions and performance improvements are challenges for MHK to be competitive on a regional basis;
  • Cost-competitiveness of MHK energy will require that individual devices capture more than double the amount of energy than current prototypes for the same device size;
  • Lack of available test facilities, in particular multi-berth, full-scale, grid-connected open water test facilities for wave energy devices, to support the anticipated acceleration in U.S. MHK market growth; and
  • Lack of scientific information, for example baseline environmental data, and high monitoring costs can drive environmental and regulatory expenses to 30%-50% of total early-stage MHK project cost.

Current status

While tidal barrage energy has been employed for several decades, overall MHK technologies are in the early stages of development, with a wide variety of designs and architectures.

Despite a significant increase in renewable generation and a diverse set of MHK technologies, there are no commercial MHK technologies deployed in the U.S. As of the end of 2014, four companies held licenses from the Federal Energy Regulatory Commission for MHK technology deployment projects, with 11 other projects in the development pipeline (holding a preliminary permit or in pre-filing for a license).

MHK power technology RDD&D opportunities

Opportunities exist for RDD&D in MHK technologies that have the most abundant resources and great potential for techno-economic viability and can be deployed in markets that have high energy costs.

Technology advancement and demonstration

Provide the ingredients for and incentivize incubation of revolutionary concepts. Prove technical credibility, catalyze device design evolution and optimize performance (i.e., application of optimized controls, power takeoff, and structure components to double annual energy production and increase availability).

Testing infrastructure and instrumentation

Strengthen MHK device quality and reliability, provide affordable access to facilities for testing, and develop robust instrumentation and sensors.

Resource characterization

Classify U.S. MHK resources, disseminate resource data among stakeholders and develop numerical modeling tools to predict loading conditions. Quantify and classify environmental conditions to reduce siting risk.


The Renewable Energy Policy Network for the 21st Century (REN21) indicates at the end of 2014, the U.S. was second in the world, with China in first place, in renewable power total capacity or generation – including hydropower. Although the U.S. is not in the top nations for investment in hydropower, the report did indicate the U.S. is one of the top five nations investing in other renewables (e.g., solar and wind). Within QTR’s hydropower section, it is clear DOE thinks next-generation hydro technology is the main factor that will fuel investment and deployment of hydropower systems.

To read the QTR, log onto

Gregory Poindexter is associate editor of Hydro Review.

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