Reduction of wave-induced pitch motion of a semi-sub wind platform by balancing heave excitation with pumping between floats

It is desirable to control pitch motion of semi-submersible wind platforms to reduce turbine hub acceleration and increase structural fatigue life. This is achieved by balancing the moment on the platform due to heave float excitation by generating a differential internal head of water between the floats though a pump. This is demonstrated with an experimentally validated linear diffraction-radiation-drag model of an idealised platform. Different scales of platform are considered corresponding to 5, 10 and 20 MW turbines. The pitch angles and hub accelerations generally reduce as scales increase. Pumping reduces hub accelerations by up to about 40% for larger sea states. The power required for pumping would be small with a hybrid pump also operating as a turbine to store energy for the pumping operation. Without storage the power requirement is still small relative to the turbine capacity except for very high wind speeds.

A novel fractional discrete nonlinear grey Bernoulli model for forecasting the wind turbine capacity of China

PurposeA new method for forecasting wind turbine capacity of China is proposed through grey modelling technique.Design/methodology/approachFirst of all, the concepts of discrete grey model are introduced into the NGBM(1,1) model to reduce the discretization error from the differential equation to its discrete forms. Then incorporating the conformable fractional accumulation into the discrete NGBM(1,1) model is carried out to further improve the predictive performance. Finally, in order to effectively seek the emerging coefficients, namely, fractional order and nonlinear coefficient, the whale optimization algorithm (WOA) is employed to determine the emerging coefficients.FindingsThe empirical results show that the newly proposed model has a better prediction performance compared to benchmark models; the wind turbine capacity from 2019 to 2021 is expected to reach 275954.42 Megawatts in 2021. According to the forecasts, policy suggestions are provided for policy-makers.Originality/valueBy combing the fractional accumulation and the concepts of discrete grey model, a new method to improve the prediction performance of the NGBM(1,1) model is proposed. The newly proposed model is firstly applied to predict wind turbine capacity of China.

On the Development of a Metamodel and Design Support Excel Automation Program for Offshore Wind Farm Layout Optimization

In this study, a metamodel of an optimal arrangement of wind turbines was developed to maximize the energy produced by minimizing the energy loss due to wakes in a limited space when designing a wind farm. Metamodeling or surrogate modeling techniques are often used to replace expensive simulations or physical experiments of engineering problems. Given a training set, you can construct a set of metamodels. This metamodel provided insight into the correlation between wind farm geometry and the corresponding turbine layout (maximizing energy production), thereby optimizing the area of the wind farm required to maximize wind turbine capacity. In addition, a design support Microsoft Excel program was developed to quickly and easily calculate the annual energy production forecast considering the wake effect, as well as to confirm the prediction suitability, the annual energy production (AEP) analysis result of the wind farm, and the calculation result from existing commercial software were compared and verified.

Assessing the value of a diversified by-product portfolio to allow for increased production flexibility in pulp mills

This paper presents a model for design optimization of pulp mill steam utility systems subject to variations in energy prices and steam demands. A Scandinavian Kraft pulp mill is used as case study to investigate investment opportunities in lignin extraction and new turbines. The model enables solutions to be identified that are more flexible than the solutions that would have been identified with a corresponding model using, for example, annual average values for key input data. The results from the case study show that lignin extraction has a potential to contribute to flexibility in pulp mill electric power production under certain conditions provided that the mill invests in both lignin extraction and condensing turbine capacity. However, the potential electric power production flexibility will vary over time. In the studied mill, with a capacity increased to around 1.3 million tonnes/a of pulp, it is estimated to vary between 15 and 30 MW. Furthermore, investment in new condensing turbine capacity only seems to be attractive if electricity prices that are considerably higher than the spot prices of recent years are assumed. Such prices may occur if there is a clear value of tradable electricity certificates or if future electricity prices rise significantly.

Benefits and limits of season-ahead forecasts for hydropower production: a global analysis

<p>Season-ahead hydro-climatological forecasts are a useful source of information for hydropower operators: at the onset of a flooding season, for example, predictive information on the timing and magnitude of the inflow volume can help operators schedule the release trajectory, decide on the amount of volume to store, and therefore maximize hydropower production. Intuitively, the forecast value varies not only with predictive accuracy, or skill, but also with the reservoir design specifications. Characterizing and explaining the relationship between skill, design specifications, and value is thus a necessary step towards a more informed and effective use of seasonal forecasts. To investigate the nature of this relationship, we modeled 1,593 hydropower reservoirs, for which we developed 3-month ahead monthly inflow forecasts—based on a principal component linear regression model. Our results show that more than half of the dams could benefit from forecasts, averaging a 6.56% annual increase in hydropower production. We also found that forecast value is largely controlled by reservoir design specifications; specifically, we found that reservoirs with small storage capacity (relative to inflow) and large inflow volumes (relative to turbine capacity) have better chances of benefitting from accurate forecasts. With this information, we classify and map each dam on the basis of its potential to increase hydropower production.</p>

Perencanaan Pipa Dua Fasa pada Fasilitas Produksi Panas Bumi Dieng

<p><span><span><span>Lapangan Panas Bumi Dieng beroperasi sejak tahun 2004 dengan kapasitas turbin 60 MW serta memiliki target produksi sebesar 55 MW selama tigapuluh tahun. Lapangan ini, masih layak untuk dilakukan pengembangan dengan total sebesar 110 MW. Dalam mengoptimalkan kualitas uap (<em>steam quality</em>) dari kepala sumur sampai dengan input turbin maka perlu adanya perencanan mengenai dimensi dari pipa yang mengalirkan uap. Parameter yang diperhatikan dalam perencanaan pipa dua fasa yaitu diameter pipa dan penurunan tekanan. Tujuan penelitian adalah menentukan diameter pipa dua fasa dan penurunan tekanan pada salah satu sumur pengembangan lapangan Panas Bumi Dieng. Metodologi perhitungan dimensi pipa ini menggunakan standar ASME dalam penentuan diameter pipa dan menghitung besarnya penurunan tekanan sebelum input turbin menggunakan <em>software pipesim. </em>Hasil perhitungan salah satu sumur yang memiliki masa aliran sebesar 60 kg/s <span> </span>didapatkan jenis pipa Xtra Strong (XS) kualitas uap 0.176 dengan diameter pipa 8 inchi serta kecepatan aliran yang optimal sebesar 27.33 m/s <span> </span>serta penurunan tekanan dari <em>well head</em> menuju separator adalah 7, 476 bar dengan tekanan input turbin sebesar 22,985 bar.</span></span></span></p><p><em>Dieng Geothermal Field operates since 2004 with a 60 MW turbine capacity and has a production target of 55 MW for thirty years. This field is still feasible for development with a total of 110 MW. In optimizing the quality of steam (steam quality) from the wellhead to the turbine input, it is necessary to plan on the dimensions of the pipe that flows steam. Parameters that are considered in planning two-phase pipes are pipe diameter and pressure drop. The research objective was to determine the two-phase pipe diameter and pressure drop at one of the wells in the Dieng Geothermal field development. The methodology for calculating the pipe dimensions uses the ASME standard in determining pipe diameter and calculating the amount of pressure drop before the turbine input using pipesim software. The calculation results of one well that has a flow period of 60 kg / s obtained Xtra Strong (XS) pipe type vapor quality 0.176 with 8 inches pipe diameter and optimal flow velocity of 27.33 m / s and pressure drop from well head to separator is 7 , 476 bars with turbine input pressure of 22,985 bars.</em></p>