From the birth of modern electricity-generating wind turbines in the late 1970s to now, wind energy technology has dramatically improved. Capital costs have plummeted, reliability has improved, and efficiency has increased. High-quality turbine manufacturers exist around the world, and wind plants of 300 MW and larger are being integrated into the electrical grid to exacting utility specifications. These modern wind plants are now routinely produced by multinational manufacturing companies at a cost of energy approaching, and in some cases below, that of fossil-fuel generating plants. At the end of 2006, the total U.S. wind energy capacity had grown to 11,603 MW, or enough to provide the electrical energy needs of more than 2.9 million American homes. Wind capacity in the United States and in Europe has grown at a rate of 20% to 30% per year over the past decade. Despite this rapid growth, wind currently provides less than 1% of total electricity consumption in the United States. The vision of the wind industry in the United States and in Europe is to increase wind's fraction of the electrical energy mix to more than 20% within the next two decades.

Developments in the world of wind continue to happen at record speed. The world as a whole is in the midst of grappling with an epochal transition from a system dominated by fossil and nuclear fuel to one that relies much more heavily on renewable energy. No technology breakthroughs are required for the United States to achieve the scenario of 20% of electricity from wind by 2030. Instead, many evolutionary steps executed with technical skill, which can cumulatively result in a 30-40% improvement in the cost effectiveness of wind technology over the next few decades, are expected to occur.

Tidal energy has received increasing attention over the past decade. This increasing focus on capturing the energy from tidal currents has brought about the development of many designs for tidal current turbines. Several of these turbines are progressing rapidly from design to prototype and pre-commercial stages. As these systems near commercial development, it becomes increasingly important that their performance be validated through laboratory tests (e.g., towing tank tests) and sea tests. Several different turbine configurations have been tested recently. The test results show significant differences in turbine performance between laboratory tests, numerical simulations, and sea tests. Although the mean velocity of the current is highly predictable, evidence suggests a critical factor in these differences is the unsteady inflow. To understand the physics and the effect of the inflow on turbine performance and reliability, Verdant Power (Verdant) and the National Renewable Energy Laboratory (NREL) have engaged in a partnership to address the engineering challenges facing marine current turbines. As part of this effort, Verdant deployed Acoustic Doppler Current Profiler (ADCP) equipment to collect data from a kinetic hydropower system (KHPS) installation at the Roosevelt Island Tidal Energy (RITE) project in the East River in New York City. The ADCP collected data for a little more than one year, and this data is critical for properly defining the operating environment needed for marine systems. This paper summarizes the Verdant-NREL effort to study inflow data provided by the fixed, bottom-mounted ADCP instrumentation and how the data is processed using numerical tools. It briefly reviews previous marine turbine tests and inflow measurements, provides background information from the RITE project, and describes the test turbine design and instrumentation setup. This paper also provides an analysis of the measured time domain data and a detailed discussion of shear profiling, turbulence intensity, and time-dependent fluctuations of the inflow. The paper concludes with suggestions for future work. The analysis provided in this paper will benefit future turbine operation studies. In addition, this study, as well as future studies in this topic area, will be beneficial to environmental policy makers and fishing communities.

Todaypsilas wind technology has enabled wind to enter the electric power mainstream. Continued technology advancement will enable cost-competitive generation of 20% of the US electrical energy from renewable wind power.