Techno-economic comparison of operational aspects for direct drive and gearbox-driven wind turbines

The majority of wind turbines currently in operation have the conventional Danish concept design-that is, the three-bladed rotor of such turbines is indirectly coupled with an electrical generator via a gearbox. Recent technological developments have enabled direct drive wind turbines to become economically feasible. Potentially, direct drive wind turbines may enjoy higher levels of availability due to the removal of the gearbox from the design. However, this is only a theory: so far not substantiated by detailed analytic calculation. By providing such a calculation, this paper enables us to quantitatively evaluate technical and economic merits of direct drive and gearbox-driven wind turbines

Towards quantification of condition monitoring benefit for wind turbine generators

Condition monitoring systems are increasingly installed in wind turbine generators with the goal of providing component-specific information to the wind farm operator and hence increase equipment availability through maintenance and operating actions based on this information. In some cases, however, the economic benefits of such systems are unclear. A quantitative measure of these benefits may therefore be of value to utilities and O&M groups involved in planning and operating wind farm installations. The development of a probabilistic model based on discrete-time Markov Chain solved via Monte Carlo methods to meet these requirements is illustrated. Potential value is demonstrated through case study simulations

Supporting high penetrations of renewable generation via implementation of real-time electricity pricing and demand response

The rollout of smart meters raises the prospect that domestic customer electrical demand can be responsive to changes in supply capacity. Such responsive demand will become increasingly relevant in electrical power systems, as the proportion of weather-dependent renewable generation increases, due to the difficulty and expense of storing electrical energy. One method of providing response is to allow direct control of customer devices by network operators, as in the UK 'Economy 7' and 'White Meter' schemes used to control domestic electrical heating. However, such direct control is much less acceptable for loads such as washing machines, lighting and televisions. This study instead examines the use of real-time pricing of electricity in the domestic sector. This allows customers to be flexible but, importantly, to retain overall control. A simulation methodology for highlighting the potential effects of, and possible problems with, a national implementation of real-time pricing in the UK domestic electricity market is presented. This is done by disaggregating domestic load profiles and then simulating price-based elastic and load-shifting responses. Analysis of a future UK scenario with 15 GW wind penetration shows that during low-wind events, UK peak demand could be reduced by 8-11 GW. This could remove the requirement for 8-11 GW of standby generation with a capital cost of £2.6 to £3.6 billion. Recommended further work is the investigation of improved demand-forecasting and the price-setting strategies. This is a fine balance between giving customers access to plentiful, cheap energy when it is available, but increasing prices just enough to reduce demand to meet the supply capacity when this capacity is limited

Electrical system designs for the proposed 1GW beatrice offshore windfarm

Paper outlines a demonstrator programme which will install 2 x 5MW RePower wind turbines. Existing platforms will be used to connect demonstrator wind turbines and infrastructure can be used for a full scale 1GW wind farm

Probabilistic reliability evaluation for distribution systems with DER and microgrids

This paper presents a method for calculating the reliability of distribution systems with distributed energy resources (DER). The impact of intentional islanding of the DER units on the reliability is studied in detail as well as the impact of different switching devices. A Monte-Carlo-based computer program has been developed to simulate the performance of different typical distribution feeders. Details of the Monte-Carlo simulation and selected simulation results are given in the paper. The presence of circuit breakers and the reliability of the DER unit have a large influence on the supply reliability. The reduction in interruption costs is further determined by the relation between costs and duration

Scenarios for examination of highly distributed power systems

A set of three scenarios has been created in order to examine the incorporation of extensive penetrations of micro-generators into electricity networks (termed 'highly distributed power systems'). The scenarios have been created as a synthesis of the Future Network Technologies scenarios and the UK domestic carbon model, and yields energy use and carbon dioxide emissions of the UK housing stock from inputs of household numbers, house type, thermal efficiency, appliance efficiency, as well as the number and efficiency of micro-generators used. The centralized supply mix also varies between scenarios and features extensive penetrations of large-scale renewables. The scenarios illustrate the scale of change required to reduce CO2 emissions by 60 per cent by 2050, which has substantial impacts for electricity network operation. Moving from a centralized system to the one where one-third of electricity comes from distributed sources poses significant challenges including: reverse power flow on networks, load balancing, storage requirements, phase unbalance, harmonics, and ancillary services

Specification of reliability benchmarks for offshore wind farms

Future deployment of offshore wind farms is perceived as a logical step in energy supply diversification by policy makers and large utilities. Capital costs are high and for this reason the investment decisions are focused on initial expenditure rather than operational costs, which are assumed to be small in comparison. Nevertheless, significant operational issues have arisen in existing offshore wind farms, highlighting the need for consideration of issues such as reliability and its impact on investment payback period. Hence, the key aim of the work is to establish a set of reliability thresholds which may provide important signals to prospective investors on how technical issues such as reliability and maintenance practice can impact on long-term investment decisions in offshore wind projects: aspects which have been largely ignored by wind farm investors until recently. The studies compare the effect of these aspects with more established key metrics such as capacity factor. Capacity factor is a key variable in wind farm design and extensive studies are employed to ensure yield at the sites will be high enough to merit investment. We argue that operational aspects are equally important in decision-making

Condition monitoring benefit for onshore wind turbines: sensitivity to operational parameters

The economic case for condition monitoring (CM) applied to wind turbines is currently not well quantified and the factors involved are not fully understood. In order to make more informed decisions regarding whether deployment of CM for wind turbines is economically justified, a refined set of probabilistic models capturing the processes involved are presented. Sensitivity of the model outputs with respect to variables of interest are investigated within the bounds of published data and expert opinion. The results show that the levels of benefit are dependent on a variety of factors including wind profile, typical downtime duration and wind turbine sub-component replacement cost

Calculation of economic transmission connection capacity for wind power generation

Applications for the connection of large-scale wind power generation to transmission networks are presenting new issues both for transmission system planners and generation developers. One of the major problems faced is the assessment of transmission system capacity requirements for the export of power from areas with high penetration of variable and intermittent sources of generation such as wind power. A method for evaluating the required transmission connection capacity from an area dominated by wind generation to the main interconnected system is presented, based on historical time series data for both wind power generation output and the demand in the group. The operational implications for the transmission system and generation owners are evaluated using a cost-benefit approach. The method is demonstrated for a number of network situations. Conclusions are drawn about the value of the method and, more generally, about the trade-off between investment in transmission capacity and curtailment of wind generation under favourable wind conditions

Active management solutions to distributed and renewable generation network integration challenges in the UK

This paper is published in the Proceedings of the World Renewable Energy Congress 2005 (Wrec 2005). The proceedings were published in May, 2005, by Elsevier