Eamon McKeogh

Air entrainment rate and diffusion pattern of plunging liquid jets

Abstract In Section 1 of the paper the authors investigate the factors governing the rate of air entrainment by plunging jets by varying the jet velocity, jet d In Section 2 the nature and extent of the biphasic diffusion region is investigated for both rough and smooth jets. These two types of jet produce very

LIDAR and SODAR Measurements of Wind Speed and Direction in Upland Terrain for Wind Energy Purposes

Detailed knowledge of the wind resource is necessary in the developmental and operational stages of a wind farm site. As wind turbines continue to grow in size, masts for mounting cup anemometers—the accepted standard for resource assessment—have necessarily become much taller, and much more expensive. This limitation has driven the commercialization of two remote sensing (RS) tools for the wind energy industry: The LIDAR and the SODAR, Doppler effect instruments using light and sound, respectively. They are ground-based and can work over hundreds of meters, sufficient for the tallest turbines in, or planned for, production. This study compares wind measurements from two commercial RS instruments against an instrumented mast, in upland (semi-complex) terrain typical of where many wind farms are now being installed worldwide. With appropriate filtering, regression analyses suggest a good correlation between the RS instruments and mast instruments: The RS instruments generally recorded lower wind speeds than the cup anemometers, with the LIDAR more accurate and the SODAR more precise.

Derivation of Intertemporal Targets for Large Pumped Hydro Energy Storage With Stochastic Optimization

This paper models large pumped hydro energy storage in a future power system where variable generation, primarily in the form of wind generation, is the dominant source of power generation. The research question posed is how to formulate day-ahead and week-ahead reservoir targets for pumped hydro energy storage in the context of wind forecast uncertainty. The innovation in the work is the use of historical wind data series and wind forecasts to derive a management strategy for the operation of large PHES using stochastic optimization that outperforms current methods in power systems with significant wind generation. This approach derives intertemporal targets for large pumped hydro energy storage that reduce overall system costs when compared to targets derived using a conventional method.

Electric Vehicles and energy storage — a case study on Ireland

Renewable energy is generally accepted as an important component of future electricity grids. In late 2008, the Government of the Republic of Ireland set a target of 10% of all vehicles in its transport fleet be powered by electricity by 2020. This paper examines the potential contributions Electric Vehicles (EVs) can make to facilitate increased electricity generation from variable renewable sources such as wind generation in the Republic of Ireland. It also presents an overview of the technical and economic issues associated with this target.

Wind power forecasting & prediction methods

Globally on-shore wind power has seen considerable growth in all grid systems. In the coming decade off-shore wind power is also expected to expand rapidly. Wind power is variable and intermittent over various time scales because it is weather dependent. Therefore wind power integration into traditional grids needs additional power system and electricity market planning and management for system balancing. This extra system balancing means that there is additional system costs associated with wind power assimilation. Wind power forecasting and prediction methods are used by system operators to plan unit commitment, scheduling and dispatch and by electricity traders and wind farm owners to maximize profit. Accurate wind power forecasting and prediction has numerous challenges. This paper presents a study of the existing and possible future methods used in wind power forecasting and prediction for both on-shore and off-shore wind farms.

Wind energy integration and the Ireland-Wales interconnector

In a small electricity grid such as the all Ireland system of Northern Ireland and the Republic of Ireland, managing with the variability of high levels of wind power generation will be crucial to ensuring the economic success of wind energy generation and the overall stability of the electricity system. Storage and interconnection are frequently proposed to manage this variability and total flexibility of the interconnector is assumed. This paper examines how market and meteorological effects could constrain interconnector operation. Currently an interconnector between the Republic of Ireland and Wales officially referred to as the East West Interconnector is in planning. The split between energy transfer and reserve provision through the interconnector will be dictated by energy prices and relative value of reserve services. The levels of wind power generation in each connected region may limit the mutual support expected from interconnection. In this regard wind forecasting and wind correlations in the connected regions are extremely relevant and are discussed in this paper.

Electric vehicles and displaced gaseous emissions

Electric vehicles (EV) do not emit tailpipe exhaust fumes in the same manner as internal combustion engine vehicles. Optimal benefits can only be achieved, if EVS are deployed effectively, so that the tailpipe emissions are not substituted by additional emissions in the electricity sector. This paper examines the potential contributions that Plug in Hybrid Electric Vehicles can make in reducing carbon dioxide. The paper presents the results of the generation expansion model for Northern Ireland and the Republic of Ireland built using the dynamic programming based long term generation expansion planning tool called the Wien Automatic System Planning IV tool. The model optimizes power dispatch using hourly electricity demand curves for each year up to 2020, while incorporating generator characteristics and certain operational requirements such as energy not served and loss of load probability while satisfying constraints on environmental emissions, fuel availability and generator operational and maintenance costs. In order to simulate the effect of PHEV, two distinct charging scenarios are applied based on a peak tariff and an off peak tariff. The importance and influence of the charging regime on the amount of energy used and gaseous emissions displaced is determined and discussed.

Forecasting Wind Generation, Uncertainty and Reserve Requirement on the Irish Power System using an Ensemble Prediction System

The ability to quantify forecast uncertainty is critical to safe, efficient and economical operation of the power system, given the rapidly increasing wind penetration into the relatively small synchronous Irish system (over 1.5 GW of wind in an all-island system with a peak demand of less than only 7 GW). An ensemble prediction system has been employed for the forecasting of generation for wind farms in the Republic of Ireland, as well as for the quantification of the forecast uncertainty at each farm. Results indicate the forecast (mean absolute) error for the total wind generation capacity (over the 51 wind farms studied) was less than 7% (normalised to installed capacity). Single-site forecast errors are typically almost twice as much as this, which highlights the benefits of regional, aggregated wind generation forecasting for safe and efficient power system operations.

Wind energy and system security – the grid connection moratorium in Ireland

This examines the interaction between technical challenges and policy choices that are made regarding wind power, and uses the grid connection moratorium in Ireland as a case study. While total installed wind capacity in Ireland is low compared with Germany, Spain and Denmark, wind power penetration is higher in the Irish system than in either the British, UCTE or NORDEL systems. In December 2003 the system operators expressed concerns about high wind power penetration, in particular the challenges of maintaining power system stability, security and reliability, resulting in a moratorium on new grid connection agreements. Significant progress has since been made in grid codes and dynamic models for wind turbines. In March 2006, there remain almost 3000 MW of proposed wind capacity awaiting a grid connection agreement. This paper investigates the technical issues underpinning this moratorium, monitors progress made since its introduction and suggests alternative technical solutions to the moratorium.

Verification of wind power forecasts provided in real-time to the Irish Transmission System Operator

Wind power forecasts for 21 representative wind farms provided in real-time to the Transmission System Operator in Ireland have for the first time been verified against actual wind generation data. Forecast data were generated using an ensemble prediction system. For forecast lengths up to 23 hours, the mean absolute error for individual wind farms was typically about 13% (normalised to installed capacity). The error increases to ∼ 14% for day-ahead forecasts (24 – 48 hours), and to ∼ 17% for 2 – 3 day forecasts. The error growth for the aggregated total of the wind farms was substantially lower, increasing from 8% (day-ahead) to 10% (2 – 3 days). Forecasting for the aggregate of 51 wind farms only reduced these errors by 1%. Using 21 representative wind farms is therefore a reasonable balance between up-scaling from a smaller number of wind farms, and the lower errors that result from monitoring and forecasting a much larger number.