Robert Thresher

Ecological impacts of wind energy development on bats: questions, research needs, and hypotheses

At a time of growing concern over the rising costs and long-term environmental impacts of the use of fossil fuels and nuclear energy, wind energy has become an increasingly important sector of the electrical power industry, largely because it has been promoted as being emission-free and is supported by government subsidies and tax credits. However, large numbers of bats are killed at utility-scale wind energy facilities, especially along forested ridgetops in the eastern United States. These fatalities raise important concerns about cumulative impacts of proposed wind energy development on bat populations. This paper summarizes evidence of bat fatalities at wind energy facilities in the US, makes projections of cumulative fatalities of bats in the Mid-Atlantic Highlands, identifies research needs, and proposes hypotheses to better inform researchers, developers, decision makers, and other stakeholders, and to help minimize adverse effects of wind energy development.

To Capture the Wind

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 winds fraction of the electrical energy mix to more than 20% within the next two decades.

A mighty wind

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.

Inflow Measurement in a Tidal Strait for Deploying Tidal Current Turbines: Lessons, Opportunities and Challenges

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.Copyright

Marine Hydrokinetic Turbine Power-Take-Off Design for Optimal Performance and Low Impact on Cost-of-Energy

Marine hydrokinetic devices are becoming a popular method for generating marine renewable energy worldwide. These devices generate electricity by converting the kinetic energy of moving water, wave motion or currents, into electrical energy through the use of a Power-Take-Off (PTO) system. Most PTO systems incorporate a mechanical or hydraulic drive train, power generator and electric control/conditioning system to deliver the generated electric power to the grid at the required state. Like wind turbine applications, the PTO system must be designed for high reliability, good efficiency, long service life with reasonable maintenance requirements, low cost and an appropriate mechanical design for anticipated applied steady and unsteady loads. The ultimate goal of a PTO design is high efficiency, low maintenance and cost with a low impact on the device Cost-of-Energy (CoE).Copyright

A commercialization path and challenges for marine hydrokinetic renewable energy

Marine and hydrokinetic energy can be broadly categorized as wave energy, tidal current, open-ocean current, river current, and ocean thermal gradient. Salinity gradient energy is often included as a form of marine energy. The technologies used to convert these forms of energy to electricity are often referred to collectively as marine hydrokinetic (MHK) energy technologies. This paper will give a brief introduction to MHK technologies and their current status. It will also explore the scientific, technical, and nontechnical challenges and barriers to the wide-spread use of MHK technologies. The challenges and barriers include: 1) siting and permitting barriers, 2) environmental impact research needs, 3) technical research and development issues, 4) policy issues, 5) market development barriers, 6) economic and financial issues, 7) grid integration barriers, and 8) education and workforce training needs.

Wind program technological developments in the United States

Under its wind energy research and development program, the U.S. Department of Energy (DOE) works as a partner with industry to improve understanding of wind system technology and to develop and deploy advanced wind turbines in multi-regional markets. Installed capacity in the U.S. reached 1720 MW by the end of 1995. This figure however does not include some capacity that was retired or taken off line. Growth of about 140 MW during 1995, is attributed to improved and lower cost turbines and was stimulated in part by the availability of energy tax credits and production and financial incentives. In addition, there are nearly 500 MW of firm contracts for new domestic wind plants. Recently, there has been substantial growth outside the U.S. Europe went from 1671 MW in 1994 to 2478 MW in 1995 and the rest of the world went from 192 MW in 1994 to 642 MW in 1995. Commercial projects are currently producing electricity in the

Wind turbine technology — The path to 20% US electrical energy

0.05 to

Marine hydrokinetic turbine technology and the environment: Device-biota interactions

0.07/kWh range operating at moderate (5.8 m/s average) wind sites.

Trends in the evolution of wind turbine generator configurations and systems

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.