Wind Energy DIY Guide

Home Wind Turbines

Build home wind turbines or residential wind turbines. Learn how residential wind power works. These instructions to build a windmill include a 1,000 watt and a 3,000 watt versions. This e-book is full of pictures and diagrams to explain the concepts: testing with 4 blades. testing with 6 blades. how to make Free homemade wind turbine blades and it will only take about an hour to finish a set of 3. a page full of equations and examples of how to use them to figure out power, rpm, tsr, windspeed etc. (units are in miles per hour and feet) how to find Free fork lift batteries and how to make them as good as new. making a homemade de-sulfator so you can pulse any battery back into new condition. what kind of generator to look for and how to get the best prices. how to make a simple curling system to protect the windmill in high winds. how to charge several banks of batteries all at once while pulsing them back to health. How to make a 1,000 watt wind turbine for less than $150 (including tower) How to make a 3,000 watt wind turbine for about $220! Continue reading...

Home Wind Turbines Summary


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General attitudes towards wind power

Several studies in the literature do not specifically address attitudes towards on-land or offshore wind farms, but elicit attitudes towards wind power in a broader context. Some of which are presented in table 1. One of the first studies that addressed this issue was the paper by Krohn & Damborg (1999). Based on a Danish study, they reported from a survey carried out in a local area with many turbines. It was found that the distance to the nearest wind turbine and attitude are invariant. Accordingly, the distance to the nearest on-land turbine does not seem to have an influence on the attitude. Indeed they found that respondents who could see between 20-29 turbines from their home and who were living within 500 m from the nearest wind turbine tend to be more positive towards wind power in general. Unfortunately, they did not indicate whether these results were statistically significant. wind power Attitude towards wind energy with wind turbines in Table 1. General wind power...

Prior experience and implications for the future development of wind farms

In the previous sections, the potential influences of prior experience with wind turbines on the attitude towards different aspects of wind power development were presented. In this section, the results from this review are elaborated and discussed in relation to which information the studies indicate for the future development of wind farms. The discussion will focus specifically on the type of experience, such as number of turbines seen daily, having wind turbines in a view shed, etc.

View to wind turbines

Whether having an on-land or and offshore wind turbine in the view shed from the permanent or summer residence or not, seems to have heterogeneous effects on the individual attitude. In general, having a wind turbine in the view shed seems to have some effects on the perception of wind farming. Having a view to on-land (and offshore) turbines or having a view to on-land turbines and seeing many turbines per day seems to reduce acceptability of a even stronger future expansion of on-land wind power systems (Ladenburg 2008 Ladenburg et al. 2011). On the other hand, having a view to on-land turbines can increase acceptability of offshore wind farms (Ladenburg, 2010). Interestingly, having a view to offshore wind farms appears not influence attitude towards offshore wind power (Ladenburg, 2008 2009 2010). This could point towards offshore wind power development becoming an increasing acceptable substitute for land-based wind power systems, if the future on-land development cannot be kept...

Attributes of wind turbines

Conditional on having experience, it can be expected that the type of experience with the wind turbines has an impact on attitude. Ladenburg & M ller (2010) argue that the individual perception and actual exposure to wind turbines via the distance to the turbine(s), the size of the turbine(s) or the number of turbines in the vicinity might be very different between respondents. Accordingly, respondents living close to several large turbines are expected to have a completely different experience with wind turbines compared to respondents living near one single turbine, though both would state that they live close to a wind turbine. Some of these aspects were elaborated in the previous sections. However, to identify the links between the physical characteristics in terms of how different attributes of wind turbines and wind farms influence the individual attitude of a local resident remains to be a challenge. For instance, several studies have pointed out, that specific attributes of...

Characteristics of the wind turbine library

Depending on the wind turbine technology, different models must be used. For squirrel cage induction generator, a fifth order model must be used. If there are manufacturer data available, the behaviour in rated conditions must be checked with a tolerance of 10 for real and reactive power. If there are no manufacturer data for the wind turbine inertia, the value to model the wind turbine is H 4 s. For the doubly fed induction generator, the simplyfied model must take into account the rotor dynamics, to determine the overcurrent tripping of the wind turbine during voltage dips.

Active and reactive powers and currents formulations applied to wind farms

Figure 1 schematically shows the equivalent circuit of a wind generator connected to the grid (represented by a delta-connected load). Phases of the wind generator are star-connected and there is no neutral wire. Active and reactive phenomena in these power systems do not depend on the zero-sequence voltages and, thus, any artificial ground can be chosen to measure phase voltages at the point of common coupling (PCC). Figure 1 schematically shows the equivalent circuit of a wind generator connected to the grid (represented by a delta-connected load). Phases of the wind generator are star-connected and there is no neutral wire. Active and reactive phenomena in these power systems do not depend on the zero-sequence voltages and, thus, any artificial ground can be chosen to measure phase voltages at the point of common coupling (PCC). Fig. 1. Equivalent circuit of a wind generator connected to the grid Active and reactive phenomena in that power system are analyzed and their...

Case study comparison of PSD of a wind farm with respect to one of its turbines during 12 minutes

A literature review on experimental data of power output PSD from wind turbines or wind farms can be found in (Mur-Amada & Bayod-Rujula, 2007), with a parameterization and analysis of the data from very different locations. (Apt, 2007) shows an interesting comparison of the spectrum of the wind power from a wide area. In this sub-section, the analysis of a case based on (Mur-Amada, 2009) is presented. The similarity of the PSD at one turbine and at the overall output of a wind farm of 18 turbines is shown. If the fluctuations at every turbine are independent (i.e. the turbines behaves independently from each other), then the PSD of the wind farm is approximately the PSD of each turbine multiplied by the number of turbines and by the power flow efficiency. Each turbine experiments different turbulence levels and wind averages, so a representative turbine should be selected. The time lag between the variations measured in the farm and in the turbine depends on the farm layout. The...

Probabilistic small signal stability analysis with wind farm 71 Principle of Monte Carlo simulation

7.2 Probabilistic small signal stability incorporating wind farm The flow chart of the Monte Carlo simulation technique for power system small signal stability analysis with consideration of wind generation intermittence is given in Fig. 6. It is well known that the uncertainty of wind generation is due to the uncertainty of wind speed, so we begin with the probability distribution of the wind speed. Fig. 7 shows a Weibull distribution function of wind speed with k 2 and c 10. When a random wind speed is generated, the mechanical power output extracted from the wind can be calculated via a king of wind turbine model usually given by functions approximation. If the wind speed Vm is less than the cut-in speed Vcut-in or is larger than the cut-off speed Vcut-off, the wind farm will be tripped. If the current wind speed belongs to the speed range from cut-in to cut-off, the wind farm will be kept connected to the grid in power flow calculation and small signal stability analysis. The...

Attitudes towards offshore wind farms

In the following section, the attitude studies focusing on offshore wind farms are presented (Table 3). Perception of visual impacts from offshore wind farms at 4, 8 and 12 km from the shore Attitude towards more offshore turbines Perception of visual impacts from offshore wind farms turbines offshore wind farm TmveUme_30mm*< 0 nearest offshore wind farm offshore wind farm Bishop & Miller (2007) tested prior information in a study by analysing the visual impact from an 18 turbine offshore wind farm which could be viewed from the coast at different sites from the shoreline at 4, 8 and 12 km respectively. Prior experience was analysed using the approach described in Ek (2005) . It was investigated whether respondents living in an area with land-based wind farms perceived the visual impacts from offshore wind farms as being more severe when compared to respondents without any contact with wind farms or living in an area with proposed or approved wind farms. The results suggest some...

Asymptotic properties of the wind farm spectrum

On the other hand, fast wind speed fluctuations are mainly due to turbulence and microsite dynamics (Kaimal, 1978). They are local in time and space and they can affect turbine control and cause flicker (Martins et al., 2006). Tower shadow is usually the most noticeable fluctuation of a turbine output power. It has a definite frequency and, if the blades of all turbines of an area became eventually synchronized, it could be a power quality issue. Fig. 5. Time series (from top to bottom) of the active power P MW (in black), wind speed Uwmdd m s at 40 m in the met mast (in red) and reactive power Q MVAr (in dashed green). Fig. 5. Time series (from top to bottom) of the active power P MW (in black), wind speed Uwmdd m s at 40 m in the met mast (in red) and reactive power Q MVAr (in dashed green). Fig. 6. Detail of the wind farm active power during 20 s at the wind farm. Fig. 6. Detail of the wind farm active power during 20 s at the wind farm. The central limit for the sum of phasors is...

Model of wind farm of DFIG type

In this chapter, a simple aggregated model of large wind farm in the small signal stability analysis is employed. We assume that currently the operating conditions of all wind generators in a wind farm are same, and the wind farm is considered to be formed with a number of wind generators jointed in parallel. Therefore, the wind farm can be reduced to a single machine equivalent. For a wind farm consisted of N wind generators, the values of stator and rotor voltages are same as the value of single machine. The stator and rotor currents are N times larger than the single machine. The stator and rotor resistances and reactances as well as K2 are 1 N larger than the single machine. The remaining control parameters are same as the single machine.

Wind turbine faultride through

As it has been said, one of the main problems for power quality are voltage dips. Due to high renewable penetration level in transmission system, Transmission System Operators (TSO) demand to this sort of energy source support voltage under voltage sags. This obligation has provoked a huge investment in devices to support wind systems during voltage dips. Fig. 2 shows the three main technologies in the wind turbine industry. Their behaviour is different in continuous operation and during voltage dips. Fig. 2a shows the fixed-speed wind turbine with asynchronous squirrel cage induction generator (SCIG) directly connected to the grid via transformer. Fig. 2b represents the limited variable speed wind turbine with a wound rotor induction generator and partial scale frequency converter on the rotor circuit known as doubly fed induction generator (DFIG). Fig. 2c shows the full variable speed wind turbine, with the generator connected to the grid through a full-scale frequency converter....

Potential habitat enhancement by offshore wind farms

Figure 2a illustrates the general scale of boulder or gravel protection around the base of a wind farm, for relative scales compared to average turbine dimensions. Although actual dimensions vary with specific turbine makes and models, and deeper water will bring about new designs and technologies, in general, projects currently under construction, or well-advanced in the planning process are in waters up to around 30m. Projects entering the Fig. 2. a) Approximate extent of rock gravel protection around the base of a monopile wind turbine foundation and b) Polypropylene frond mats around a foundation. Both taken from Linley et al. (2007). Table 1. Habitat loss gain due to the installation of an offshore wind turbine and associated scour protection. For these calculations, a turbine foundation diameter of 4m was assumed, with 10m of scour protection extending from the edge of the foundation. For gravel, a mean diameter of 5cm was assumed, with a 2m diameter for boulders. Table 1....

Current evidence for offshore wind farms as artificial reefs

Due in part to the youthful nature of the offshore wind industry, there are still relatively few fully comprehensive studies into the influence of turbine arrays on fish and benthic populations, other than the monitoring requirements set out in the consent conditions. However, where datasets do exist, it is suggested that offshore wind farms are demonstrating benefits for such populations. The effect on commercial stocks, such as lobster and crab, are an obvious concern to those directly and indirectly involved in the exploitation of such stocks therefore any impacts are key to the Environmental Impact Assessment (EIA) process. Observations made onboard a commercial potting vessel deploying gear within the operational Barrow Offshore Wind Farm, off the north west coast of England, eighteen months after construction was completed, found that catch rates for lobster were similar inside and outside of the wind farm boundary (Centrica, 2009). In addition to this, the number of undersized...

Case study comparison of PSD of a wind farm with respect to one of its turbines during a day

In order to study the behaviour of fluctuations slower than one minute, the next section will analyze the mean power of each second during a day. Daily records with one second time resolution allow to study the fluctuations with durations from a few seconds up to an hour. Overall, the transition frequency from uncorrelated to correlated fluctuations is mild and, in fact, the ratio PSDfarm(f) PSDtmUne(j) depends noticeably on atmospheric conditions and it varies from one wind farm to another. This is one of the reasons why the values of the coherence decay factors Aiong and Aiat may vary twofold among different sources. At higher frequencies, the control and generator technology influences greatly the smoothness of the power delivery. At low frequencies and under rated power, the variability is mainly due to the wind because any turbine tries to extract the maximum amount of power from the wind, regardless of their technology. During full power generation, the fluctuations have smaller...

Wind farm modeling

Wind farm models may be built with different detail levels ranging from one-to-one modeling or by an aggregated model that consists of one or few equivalent wind turbines and an equivalent of the internal network. The aggregated model includes wind turbine units, compensating capacitors, step-up transformers, etc. Fig. 25 compares the detailed and the aggregated models. The aggregated model can be used to verify a wind installation according to PVVC when all the wind turbines that form the wind installation are of the same type. If a wind installation is formed by different wind turbines, aggregated model can be done grouping the wind turbines of the same type. Fig. 25. Wind farm modeling. Fig. 25. Wind farm modeling. When the aggregated model is used, the difference between the results obtained by the two models must be negligible. Fig. 26 and Fig. 27 show the results obtained in a example wind farm. Fig. 26 shows a comparison between the real power obtained by the simulation of a...

Wind turbine model

In modelling turbine rotor, there are a lot of different ways to represent the wind turbine. Functions approximation is a way of obtaining a relatively accurate representation of a wind turbine. It uses only a few parameters as input data to the turbine model. The different mathematical models may be more or less complex, and they may involve very different mathematical approaches, but they all generate curves with the same fundamental shapes as those of a physical wind turbine. In general, the function approximations representing the relation between wind speed and mechanical power extracted from the wind given in Equation (1) (Ackermann, 2005) are widely used in modeling wind turbine.

A model for prior experience

Attitude formation towards wind power is far from being straightforward and clear predictions are not easy. The central theme in most of the wind power literature focusing on public attitudes is how turbines under different settings and circumstances can generate opposition (see Gross 2007 Graham et al. 2009 Jobert et al. 2009 Jones & Eiser 2009 Ladenburg 2009 and Haggett 2011 for some of the more recent papers on this subject). As mentioned, the aim is to shed light on how prior experience with wind turbines might have an influence on attitude, and most importantly how we relate this to attitudes towards the wind farm landscapes to come in a near future. We therefore need a model that takes prior experience into account. Quantitative analyses of attitudes in previous research on wind power attitude formation and prior experience typically define differences in individual attitudes in a linear form, in which individual i's latent attitude qi* is a function of the individual...

Attitudes towards landbased turbines

Table 2 comprises a list of studies that analyse the potential relations between attitudes towards on-land turbines and prior experience with wind turbines. Focusing on attitudes, and the local intention to oppose turbines, Johansson & Laike (2007) tested in a Swedish study if residential prior experience variables related to the distance to the local turbines and to the view on these turbines. None of the variables are found to be significant in influencing individual perception and possible opposition. In a Danish study by Ladenburg (2008) the attitude towards more on-land turbines based on a survey from 2003-2004 was analysed. The study included two experience variables, e.g. whether the respondent could see on-land or and offshore wind farms from the permanent summer residence. The results suggest that only in the case that the respondent can see both on-land and offshore wind turbines (fiview On-Land and Offshore) prior information seems to influence the attitude towards more...

Fault ride through solutions

New wind turbines have integrated different systems to withstand voltage dips however the old wind turbines have to install different FACTS to overcome dips. The main solutions are installed either in each turbine or in the point of common coupling. The FACTS used in wind systems can be divided into three categories depending on their connection (Amaris, 2007 Hingorain, 1999)

Unified theorys active and reactive powers

Fundamental positive-sequence complex power supplied by the wind generator showed in fig. 1 is expressed as Positive-sequence active power (P+) is the real part of the above quantity and it characterizes the direct torque applied to the axis of the wind-generator. This quantity has two components, due to the active loads (Pa+ ) and caused by the unbalances (Pu+ ) Pa+ is the positive-sequence active power supplied by the wind-generator under positive-sequence balanced voltages thus, it may be defined as the positive-sequence active power due to the load consumptions. This quantity measures the active power which is transformed under the best efficiency and power quality conditions. Pu+ represents the increasing of the positive-sequence active power produced by the voltage and load unbalances. Last quantity identifies the poor power quality in the power system, since it occurs when there are voltage unbalances, and it may have the same or different sign that Pa+ , so it increases or...

Active and reactive phenomena according to the Spanish Grid Code

Active and reactive currents supplied by the wind-generator (Iaz, Irz, z A,B,C) are the traditionally known fundamental-frequency line current 0 and 90 respectively dephased with respect to its fundamental phase voltage (Vz ), Active and reactive powers supplied by the wind-generator, according to the Spanish Grid Code implicitly proposes, are the well-known active and reactive powers for sinusoidal three-phase circuits

Grid code requirements

Grid codes established by the different countries provides the minimum operation and security requirements of the wind farms installations connected to the Electric Network in order to guarantee the supply continuity in presence of voltage dips. The Spanish Operation Procedure O.P. 12.3, which constitutes the present Spanish Grid Code, establishes wind farms and all their components must be able to withstand, without disconnection, transient voltage dips at the grid point of common coupling caused by three-phase, two-phase and single-phase faults within the area described by the voltage-time characteristic showed in fig.2a. That characteristic or LVRT (Low Voltage Ride Through) requirements has been recently modified by the draft of the Spanish Operation Procedure O.P. 12.2 by increasing the allowed depth of the voltage drop up to zero during the first 150 ms after the beginning of the disturbance (fig.2b), similar to the LVRT requirements of the German Grid Code from E.ON Netz,...

Reactive power requirements

The present Spanish Grid Code (O.P. 12.3) prescribes that reactive power consumptions are not allowed in the wind farm installations at the point of common coupling with the grid during the voltage dip and the following clearance fault and voltage recovery. However, some reactive power consumptions lower than 60 of the registered rated power in each cycle (20 ms) may be allowed during just the 150 ms after the beginning of three-phase balanced voltage dips and the 150 ms after its clearance (fig.3a). These admitted periods of reactive power consumptions will be reduced in the future Spanish Grid Code (O.P. 12.2) to 40 ms after the beginning of the fault and 80 ms after the voltage recovery and clearance fault (fig.4a). For unbalanced single-phase and two-phase voltage dips (fig.3b), some unspecified reactive power consumptions are allowed during the 150 ms after the beginning of the fault (80 ms according to the O.P. 12.2, fig.4b) and the 150 ms after the voltage recovery (80 ms...

Practical experiences

Two remarkable events occurred in a Spanish wind farm is used in this section to analyze utility of the active and reactive formulations established in section 2 and their application for verifying grid code requirements. Those events are a three-phase balanced voltage dip and a two-phase voltage dip manifested at the connection point of a 660 kW rated power wind generator, with 690 V phase to phase nominal voltages. Spanish and German grid code requirements was verified by the wind farm in presence of the analyzed two-phase dip whether the Unified Theory is used. However, the application of the traditional theory is very complicated since the traditional active and reactive currents have different sign and value in each grid phases (figs. 16 and 18) and traditional active and reactive powers contain negative-sequence components. Unified Theory's positive-sequence active and reactive currents verify grid code requirements because their values are not increased during the fault (figs....

Example of model system

Fig. 1 shows an overview of FESS operation proposed in this chapter. The isolated power system consists of main power supply, a consumer load and a wind farm. FESS is installed near the wind farm. FESS detects the network frequency and stabilizes it by supplying or absorbing active power to from the network. FESS also sends a command to the main power supply to adjust its output so as to keep suitable stored energy level of FESS. Fig. 1 shows an overview of FESS operation proposed in this chapter. The isolated power system consists of main power supply, a consumer load and a wind farm. FESS is installed near the wind farm. FESS detects the network frequency and stabilizes it by supplying or absorbing active power to from the network. FESS also sends a command to the main power supply to adjust its output so as to keep suitable stored energy level of FESS. Fig. 2 shows the power system model used in this chapter. A Wind Farm (WF) is modeled by a single induction generator with a wind...

Mathematical framework and notation 21 Model assumptions

According to (Cidras et al., 2002), voltage drops can only induce synchronized power fluctuations in a weak electrical network with a very steady and a very uniformly distributed wind. Most grid codes have been modified to minimize the simultaneous loss of generation during special events such as breaker tripping, grid transients, sudden voltages changes, etc. Except during the previous events, the synchronization of power fluctuations from a cluster of turbines is primarily due to wind variations that are slow enough to affect several turbines inside a wind farm. Experimental measurements have corroborated that blade synchronisation is unusual. In addition, fluctuations due to turbine vibration, dynamics and control can be considered statistically independent between turbines, whereas turbulence and weather dynamics are partially correlated. Fortunately, slow fluctuations can be linked to equivalent wind fluctuations through a quasi-static approximation based on the power curve of...

Pf Pf e Pt e2nf tdt LPt1

In this chapter, P(t) represents the power output of a turbine or a wind farm. The root mean square value (RMS for short) of power fluctuations at frequencies between f-Af 2 and f+Af 2 is P(f) I l2-Af . Power variance inside the previous frequency range is PSDp (f )-Af . Hence, PSDp (f) in this chapter does not represent a power spectral density and this term can lead to misinterpretations. Therefore, PSDp (f) will be referred in this chapter as the auto spectral density although the acronym PSD (from Power Spectral Density) is maintained because it is widespread. Sometimes PSDp (f) will be replaced by ap (f) to emphasize that it represents the variance spectral density of signal P at frequency f. Fig. 3. shows the estimated PSD from 13 minute operation of a squirrel cage induction generator (SCIG) directly coupled to the grid (a portion of the original data is plotted in Fig. 1). The original auto spectrum is plotted in grey whereas the estimated PSD is in thin black The...

Interaction of dispersed power generation sources DPGS with the power grid

In the case of using asynchronous generators, only parallel cooperation with the power system is possible. This is due to the fact that reactive power is taken from the system for magnetization. When the synchronous generator is used or the generator is connected by the power converter, both parallel or autonomous (in the power island) work is possible. The level of generating power and the quality of energy have to be taken into consideration when dispersed power sources are to be connected to the distribution network. In regard to wind farms, it should be emphasized that they are mainly connected to the HV distribution network for the reason of their relatively high generating power and not the best quality of energy. This connection is usually made by the HV to MV transformer. It couples an internal wind farm electrical network (on the MV level) with the HV distribution network. The internal wind farm network consists of cable MV lines working in the trunk configuration connecting...

Technical requirements for the dispersed power sources connected to the distribution network

Basic requirements for dispersed power sources are stipulated by a number of directives and instructions provided by the power system network operator. They contain a wide spectrum of technical conditions which must be met when such objects are connected to the distribution network. From the point of view of the power system automation, these requirements are mainly concerned with the possibilities of the power level and voltage regulation. Additionally, the behaviour of a wind farm during faults in the network and the functioning of power protection automation have to be determined. Wind farms connected to the HV distribution network should be equipped with the remote control, regulation and monitoring systems which enable following operation modes participation in the frequency regulation (this type of work is suitable for wind farms of the generating power greater than 50 MW). During faults in HV network, when significant changes (dips) of voltage occur, wind farm cannot loose the...

Influence of connecting dispersed power generating sources to the distribution network on the proper functioning of

Even more frequently, using of the DPGS, mainly wind farms, is the source of potential problems with the proper functioning of power protection automation. The basic functions vulnerable to the improper functioning in such conditions are The subsequent part of this paper will focus only on the influence of the presence of the wind farms on the correctness of action of impedance criteria in distance protections. Distance protection provides short-circuit protection of universal application. It constitutes a basis for network protection in transmission systems and meshed distribution systems. Its mode of operation is based upon the measurement and evaluation of the short-circuit impedance, which in the typical case is proportional to the distance to the fault. They rarely use pilot lines in the 110 kV distribution network for exchange of data between the endings of lines. For the primary protection function, comparative criteria are also used. They take advantage of currents and or...

Future study requirements

The status of offshore wind energy generation as a relatively young industry has both positive and negative aspects for developing its potential in habitat creation. With few long-term studies of the changes in abundance and diversity of species within wind farms available, due to the relatively low number of developments currently operational, there are few datasets to fully analyse for the potential habitat gain which have been discussed in this chapter. These findings highlight the need to ensure surveys of already operational offshore wind turbines, and their associated scour protection and infrastructure, continue throughout the lifetime of the project, which can be up to fifty years (Centrica, 2009). The Perkol-Finkel and Benayahu (2005) study also highlights the fact that surveying the development of life on turbines alongside neighbouring natural communities will allow evaluation of the biological and environmental benefit of the turbines as artificial reef structures. Further...

Unified theorys active and reactive currents

Let's consider the equivalent circuit of a wind-generator connected to the grid, represented in fig.1. Fundamental-frequency voltages obtained at the point of common coupling (PCC) Fundamental positive-sequence line currents (IA, IB, IC ) supplied by the wind-generator showed in fig. 1 are unbalanced have the following general expression, from (4) and (8) being Ge _ Ye cos ae the load positive conductance, the real part of the positive admittance (Ye ). The above current is 0 dephased with the fundamental positive-sequence phase to ground voltage (VA+ ) and it transfers the useful power (positive-sequence active power, P+) produced by the wind-generator. Active fundamental positive-sequence line current may be decomposed into two components too, as it is appreciated from (11)

Voltage dip generator model

In PVVC the system shown in Fig. 19 is proposed. In this system, the voltage measured in the field test is introduced in the simulation and reproduced by a voltage source. Thus, the wind turbine model is subjected to the same voltage than the wind turbine during the field test and only the active and reactive power must be compared to validate the model.

International grid code requirements

Wind farms should contribute to power system control (voltage and frequency) and also to the electricity network recover in case of networks faults such as voltage dips or swells. In the most cases a wind turbine should work with a power factor of 0.90 lagging to 0.95 leading and the frequency should situate within the range from 47.5 Hz to 52 Hz. The most outstanding international Grid Codes are the following USA FERC Interconnection for Wind Energy 18 CFR Part 35 (Docket No. RM05-4-001 Order No. 661-A), Issued December 12, 2005 and Interconnection Requirements for a Wind Generating Plant, Appendix G to the LGIA. China - CEPRI Technical Rule for Connecting Wind Farm to Power System, December, 2005. Denmark - ELKRAFT SYSTEM and ELTRA Wind Turbines Connected to Grids with Voltages above 1GG kV - Technical regulations for the properties and the regulation of wind turbines, Regulation TF 3.2.5, December 3, 2004. Canada - AESO Wind Power Facility - Technical Requirements, Revision 0,...

Fault ride through certification procedure for power generating units

Once the requirements for wind power system have been established, another important point is how wind turbine manufacturers and wind park operators can prove the fulfilment of Grid Codes. The Spanish Wind Energy Association (AEE) has developed the document Procedure for Verification Validation and Certification of the Requirements of the OP 12.3 on the Response of Wind Farms in the Event of Voltage Dips (PVVC), and the German Fordergesellschaft Windenergie und andere Erneuerbare Energien (FGW) the document Technical Guidelines for Power Generating Units. Part 8. Certification of the electrical characteristics of power generating units and systems in the medium, high- and highest-voltage grids that describes the procedures to certify wind power installations according their corresponding Grid Codes. This section describes the steps to fulfil certificate wind systems by these two procedures. 4.1 PVVC procedure The General Verification Process consists of verifying that the wind farm...

Robust frequency control in a hybrid winddiesel power system

The basic system configuration of an isolated hybrid wind-diesel power generation system as shown in Fig. 5 (Das 1999) is used in this study. The base capacity of the system is 350 kVA. The diesel is used to supply power to system when wind power could not adequately provide power to customer. Moreover, The PPC is installed in the wind side while the governor is equipped with the diesel side. In addition to the random wind energy supply, it is assumed that loads with sudden change have been placed in this isolated system. These result in a serious problem of large frequency deviation in the system. As a result, a serious problem of large frequency deviation may occur in the isolated power system. Such power variations and frequency deviations severely affect the system stability. Furthermore, the life time of machine apparatuses on the load side affected by such large frequency deviations will be reduced. Step input of wind power or load change Random wind power input...

Sum of partially correlated phasor densities of power from several turbines

If turbine fluctuations at frequency f of a wind farm with N turbines are completely synchronized, all the phases have the same value f) and the modulus of fully correlated If there is no synchronization at all, the fluctuation angles i(f) at the turbines are stochastically independent. Since Pi, uncorr (f) has a random argument, its sum across the wind farm will partially cancel and inequality (13) holds true. Note that the phase of the admittance J(f) has been omitted since the phase lag between the oscillations at the cluster and at a turbine depend on its position inside the cluster. The admittance is analogous to the expected gain of the wind farm fluctuation respect the turbine expected fluctuation at frequency f (the ratio is referred to the mean values because both signals are stochastic processes). An analogous procedure can be replicated to sum fluctuations of wind farms of a components. The main difference in the regional model -apart from the scattered spatial region and...

Evaluation of the wind installation response

The wind farm must withstand the dips without disconnection. The simulation model must include the protections that determine the disconnection of the wind turbines. As has been shown in section 7.1, there are two possibilities for the wind farm modeling Detailed model (without aggregation). In this case, the continuity of supply is guaranteed if the real power of the disconnected wind turbines during the simulation does not exceed the 5 of the real power before the dip.

Voltage dip generator

Dip generator scheme and its position with respect to the windmill and the wind farm. 5.1.1 20 kV 5 MW Voltage dip generator This section describes the design of a 20 kV, 5 MW voltage dip generator. It is installed in a trailer, so it is able to move to the wind turbine location (Garc a-Gracia et al, 2009). Fig. 12. Dip generator scheme and its position with respect to the windmill and the wind farm. 5.1.1 20 kV 5 MW Voltage dip generator This section describes the design of a 20 kV, 5 MW voltage dip generator. It is installed in a trailer, so it is able to move to the wind turbine location (Garc a-Gracia et al, 2009). Wind turbine


As stressed in the prior experience model, the prior experience relates to a physical encounter with wind turbines entails different types of information. In the review below, these differences are addressed and related to the type of wind power development location, i.e. general attitude towards wind power and attitudes towards specific locations of development. Hereby land-based and offshore installations are distinguished.

Number of turbines

One of the fundamental wind power planning aspects is, how many wind turbines an area can contain without having too negative impacts on the local acceptance of wind power. Focusing on Ladenburg & Dahlgaard (2011) and Ladenburg et al. (2011), there seems to be a relationship between attitude towards land-based wind turbines in general and the total number of wind turbines in the local area. Apparently, higher numbers of turbines reduces acceptability of both existing and future planned increase of land-based wind turbines. However, the results also point to the triggers that cause the negative relation. The negative effects of seeing many turbines on a daily basis are tightly linked to having an on-land wind turbine in the direct view shed. Accordingly, many wind turbines in an area might not be a problem, as long as the number of respondents who have a direct view shed to turbines are minimised. In general, the cumulative effects of the total number of turbines on the individual...

Distance to turbines

The distance to wind turbines captures several dimensions of prior experience. If wind turbines are more common in the landscape, the distance captures the potential subjectivity to the impacts from the wind turbines. If people live close to a wind turbine, they might be more disturbed by visual intrusion, noise impact etc. compared to a respondent, who lives far from a wind turbine. However, if wind turbines are a relatively scarce commodity, such as the current offshore wind farms in Denmark, the distance captures a measure of the potential experience with a wind turbine, i.e. the further away people live from a wind turbine the lower is the probability that they have actually ever seen a wind turbine. Such effects could explain some of the observed distance effects in the reviewed studies. Findings from the literature thus stress the role of distance, though the results are nonetheless ambiguous. In Warren et al. (2005) acceptance of on-land wind turbines decreases with distance....


The Spanish Grid Code and the grid codes from other countries require some quantities, such as active and reactive currents and powers, must be controlled in order to avoid unexpected disconnections of the wind farms submitted to voltage dips. These grid codes implicitly propose the traditional well-known formulations, included in the IEEE Standard 1459-2010, for measuring active and reactive powers and currents. For balanced voltage dips, these formulations are adequate to verify grid code requirements, although the different values of the active and reactive phase currents may difficult the verification process. However, for unbalanced voltage dips, traditional formulations include components which are a result of the imbalances and, thus, mistakes in the magnitude and duration of the active and reactive quantities may be presented. This decomposition established by the Unified Theory has been expressed in section 2. It shows how imbalances of supplies and loads originate additional...

Simulation example

A determination of the energy storage capacity is very important for designing energy storage system. In this chapter, the energy storage capacity of FESS is determined from a point of view of adequate frequency control ability but reducing it as small as possible. The power rating of FESS is decided as 70 of that of the wind farm since instantaneous output change of the wind farm can hardly reach its power rating in normal operation. Comparative study between the proposed frequency control method (shown in Fig. 7 and Table I) and a power smoothing method (shown in Fig. 12 and Table V) which is generally considered in a wind farm connected to large power system, is performed in the simulation analysis here. In conventional power smoothing method, an energy storage system only smoothes wind farm output fluctuations, and slow change of wind farm output is absorbed by several thermal and hydraulic power plants installed as main generators in large power system. However, since the total...


This chapter has proposed a new method of network frequency regulation by using Flywheel Energy Storage System (FESS) for an isolated power system including a wind farm, and the validity of the proposed method has been evaluated by computer simulations. From the comparative study between the proposed method and the conventional output smoothing control of wind farm, it has been shown that the proposed method is very effective on the stabilization of network frequency in an isolated small power system. The proposed method can be applied basically not only to a FESS system but also other types of energy storage system. Therefore the proposed method can contribute to expand wind energy utilization into isolated power systems like a small island.


Existing insights relating to the research questions above are yet limited. Thus, an exploratory or discovery-oriented approach was chosen, in which the primary stipulation was that the research should be empirical. The results and deliberations presented here are generated from several focus group meetings, stakeholder workshops, and semi-structured interviews over the course of years of research on the subject of multi-use management of offshore wind farms and mariculture. The key findings are summarised in Buck (2002) Krause et al., (2003) Buck et al., (2008) Michler-Cieluch and Kodeih, (2007) Michler-Cieluch and Krause, (2008). Core of the discussions below are the findings from semi-structured interviews with people involved in the offshore wind farm sector and with individuals of the mussel fishery farming sector in Germany. Conclusions about suitable organisational structures are based on participants' views and their critical understanding of potential 'wind farm- mariculture...


However, when addressing the identified offshore stakeholders, most of the interviewees were generally interested in this specific type of multiple-use setting and vitalized the conversation around the guiding questions with their own comments and ideas. Concurrently with judging 'wind farm - mariculture integration' as an idea worthy to consider, interviewees mentioned several framework requirements for initiating and effectively pursuing cross-sectoral offshore operation and organisation. Not only had certain preconditions to be fulfilled, for example the need to clarify the working tasks and siting of aquaculture installations in the forehand, but also overall regulatory conditions, e.g. determination of working rules, allocation of responsibilities, as well as commercial arrangements or actuarial regulations (Figure 1). The issue of sharing responsibilities in the context of everyday organisation and questions of ownership were especially stressed. In the following, we discuss the...


The results of this stakeholder survey can help us to differentiate the likelihood of various mariculture-wind farm integration scenarios going forward, specifically regarding the various forms of ownership and management such a venture might take. The attitudes and perceptions of these groups prior to implementation are informed by their views on the possible synergies in production and organisational structure. Framing the results of the surveying and other contextual information in the well-developed literature of inter-firm organisation and cooperation will provide a basis for understanding the potential of this concept. Wind farmer Wind farmer Wind farmer Fig. 1. Framework requirements for managing 'wind farm-mariculture integration' (modified after Michler-Cieluch and Krause, 2008). There are many literature reviews that attempt to identify the basic elements necessary to conduct comparative research into inter-firm organisational structures and processes (Grandori & Soda,...

Model validation

The Spanish PVVC and the German FGW-TG4 (FGW, 2009) give the procedures to validate wind turbine systems by comparing the results obtained by simulation and that obtained from on-site test. PVVC and FGW-TG4 gives the maximum deviation and the specific time intervals for the comparison of the results. The Spanish PVVC establishes a time window of 1 s with 100 ms before the voltage dip, and the German FGW-TG4, 500 ms before the voltage dip and 2 s after the voltage recovery. Fig. 18 shows the different time windows established in each document. It is important to point out that the time window from the PVVC is fixed and does not depend on the voltage dip duration whereas the FGW-TG4 depends on it. Next the validation process followed for a wind turbine generator from in-field testing results according to the Spanish PVVC.


Chapter 1 Local Attitudes towards Wind Power The Effect of Prior Experience 3 Chapter 2 Wind Farms and Grid Codes 17 Chapter 4 Frequency Control of Isolated Power System with Wind Farm by Using Flywheel Energy Storage System 65 Chapter 6 Power Fluctuations in a Wind Farm Compared to a Single Turbine 101 Chapter 7 Distance Protections in the Power System Lines with Connected Wind Farms 135 Part 5 Spin-off Products of Offshore Wind Farms 183 Chapter 9 The Potential for Habitat Creation around Offshore Wind Farms 185 Chapter 10 Perceived Concerns and Advocated Organisational Structures of Ownership Supporting 'Offshore Wind Farm - Mariculture Integration' 203 Capturing wind energy has been widely employed for centuries - i.e. the traditional windmills of the Netherlands being a significant landscape element for centuries. To date, the emerging market for wind power energy is experiencing remarkable global growth rates which affect not only the problem of how to technically link these...


Prior experience with wind turbines is found to be a significant determinant of individual attitude towards wind farms in many studies. With the increasing level of wind power development on a global scale, this information can be of particular importance. The information entailed in the impacts from prior experience can thus serve as a guideline for policy planners and wind generation developers to increase the wind power capacity in an effective manner, so that opposition or negative attitudes towards wind power are minimised in future wind power landscapes. Based on the significant prior experience effects, the review of the studies points towards that increasing number of turbines on-land can reduce the acceptance of future wind power development at even small additions to the current numbers of wind turbines. This is particularly evident if wind turbines cannot be kept out of the view shed from the individual residence. It could be shown that a solution to this increasing problem...

Application example

A wind farm with 200x2MW DFIGs is integrated into the non-generator buses, i.e. busl-bus29. The corresponding parameters of wind turbine and DFIG are given in Table 1. According to the procedure given in Fig. 6, the frequency distribution of wind speed by applying Monte Carlo method to the Weibull probability distribution of wind speed can be calculated as depicted in Fig. 9. The sample size is set to be 8000 during simulation. Table 1. Parameters of wind turbine and DFIG with 2 MW capacity Table 1. Parameters of wind turbine and DFIG with 2 MW capacity Wind speed m s Fig. 9. Frequency distribution of wind speed Next, in accordance Eq. (1) and the frequency distribution of wind speed as shown in Fig.9, for the wind farm with 200*2MW capacity, the probability distribution of wind farm power output can be finally obtained as shown in Fig. 10. From Fig.10, there exist two concentrations of probability masses in the distribution one corresponds to the value of zero, in which the wind farm...

Z2 a 09 ZAB 09ZBC

Courses of the rms value of voltage U, current I, active and reactive power (P and Q) when there are voltage dips caused by faults in the network. The recordings are from a wind turbine equipped with a 2 MW generator with a fault ride-through function (Datasheet, Vestas). This function permits wind farm operation during voltage dips, which is generally required for wind farms connected to the HV networks. Fig. 8. Courses of electric quantities for Vestas V80 wind turbine of 2 MW a) voltage dip to 0.6 Un, b) voltage dip to 0.15 Un (Datasheet, Vestas) Fig. 9. Linear approximation of current and voltage values for the wind turbine with DFIG generator during voltage dips Ug - voltage on generator outputs, Ig - current on generator outputs, iim_G - generator reactive current, ti 50 ms, 3- 2 100 ms Fig. 10. Course of the wind turbine reactive current Fig. 10. Course of the wind turbine reactive current The negative influence of the low value steady current from the wind farm is cumulating...

Juming Wanga Ted W Sammisa and David R Millerb

Eddy covariance technology has been used for crop water use measurements (evapotranspiration, ET) widely because its operation is relatively simple and the equipment is less expensive than constructing a lysimeter. However, this technology has energy closure problems. These problems can be caused by low wind speed, stable conditions, horizontal flux or and canopy roughness. In addition, wind sensor leveling, air humidity, and footprint can affect the ET measurement accuracy. This commentary discusses how to check ET measurement accuracy and how to measure accurate ET using eddy covariance technology. Eddy covariance technology has been used widely because of its relatively simple operation and lower expense for equipment compared to constructing a lysimeter. An eddy covariance system consists of a vapor concentration sensor (e.g., infrared open-path Licor-7500, Campbell Sci., Inc., Logan, Utah) and a high-frequency sonic wind velocity sensor

Monitoring and Predicting Agricultural Drought

According to Diepen and van der Wall (1996), factors influencing yield can be categorized as (1) abiotic factors, such as soil water, soil fertility, soil texture, soil taxonomy class, and weather (2) farm management factors, such as soil tillage, soil depth, planting density, sowing date, weeding intensity, manuring rate, crop protection against pests and diseases, harvesting techniques, postharvest loss, and degree of mechanization (3) land development factors, such as field size, terracing, drainage, and irrigation (4) socioeconomic factors, such as the distance to markets, population pressure, investments, costs of inputs, prices of output, education levels, skills, and infrastructure and (5) catastrophic factors that include warfare, flooding, earthquakes, hailstorms, and frost. Measuring or estimating some of these factors is often not feasible, and the influence of some other factors may be considered insignificant or constant in an economically stable region. It is therefore...

Appropriate Averaging Time

Appropriate averaging time should be chosen for eddy covariance measurements. Usually daytime averaging time is longer than nighttime. Vickers and Mhart (2006) provide a cospectra method and corresponding software to determine the averaging time. Using this paper and its software we obtained averaging times for an eddy covariance system for a full-canopy pecan orchard at Las Cruces, NM, USA. An infrared open-path Licor-7500 (Campbell Sci., Inc., Logan, Utah) and a high-frequency sonic wind velocity sensor (CSAT3, Campbell Sci., Inc., Logan, Utah) were set up above the pecan canopy. A CR23X was used to record

Data From Weather Satellites

Now we have launched our own Oceansat-1 onboard IRS-P4 on 26th May, 2003 which contained 8 channel onboard sensor called Ocean colour monitor ( Chlorophyll content ) over ocean and another microwave sensor called Muti-channel microwave radiometer (MSMR) with channel frequencies (6.6 GHz, 10.8Ghz, 18 GHz and 21 GHz) in both horizontal and vertical polarization, and is used to measure geophysical parameter related to ocean such as sea surface temperature (SST), wind speed, total integrated water vapour, and cloud liquid water vapour content (Krishna Rao, 2000).

Some Important Microwave Payloads And Their Applications

And precipitation radar are the examples of active microwave sensors. Scatterometer with operating frequencies in C-Band ( 5 GHz), or K-Band ( 13 GHz) is an indispensable tool for monitoring the ocean surface wind speed and wind direction with high resolution ( 25 km ) and global coverage. Ocean surface winds have a number of applications. These winds are important factors in the computation of air-sea energy and mass exchange, and they also provide input to the global ocean and wave forecast models. The use of scatterometer winds in assessing the situations leading to the formation of tropical cyclones have been demonstrated. Precipitation radar (PR) onboard Tropical Satellite Measuring Mission (TRMM) satellite is the first precipitation radar in space. This instrument operating at 13.6 GHz is capable of taking observations of vertical profiles of rainfall over the global tropics. Among passive microwave meteorological systems, Special Sensor Microwave Imager (SSM I) onboard US...

The Past Revisits and the Future Begins

By the beginning of the second year, I knew the landscape so well that I could have walked around the farm with my eyes closed. I knew the grade of the prairie. I could sense clearings by the subtle change in wind speed, and distance by the sounds of my neighbor's farm vehicles working the crops. The smells alone nonnative catnip plants and native mints, bergamot, and various types of fertilizers wafting on the breeze gave me a sense of perspective and grounding, a deep familiarity with the land. It was my home, and I felt elated as I drove or flew back from business trips. Each time I returned, I brought with me new knowledge and widening perspective. My professional work whether it was studying the impact of livestock grazing on national forest land in Colorado, designing river and wetlands restorations, or exploring the sustainability of nature preserves in Illinois always informed my domestic life on the farm. And things I learned on the farm certainly informed my work. My only...

Drought Research Needs

In Mexico, only a few weather variables are monitored daily at the manual stations. These variables include precipitation (24-h total), maximum and minimum temperature, evaporation, wind speed and direction. The new automatic stations linked via satellite (GOES-12) monitor the above variables plus relative humidity, solar radiation, and precipitation. Mean values of 10-min data are sent every 3 h to the SMN headquarters for rapid uploading on-line

Equations to Elaborate Models for Agricultural Planning Inside the Oasis

As said in the previous paragraphs there is many problems in the oasis of the region that concern the methods adopted to manage the distribution of nutrients and water between plants. The soil of the oasis is isotropic, homogeneous and very porous. We found different kinds of market gardening, different types of fruit trees and many sorts of date palms in the same filed. Those canopies are arranged in different ways and directions. Many questions we must ask which nutrient to use to which type of plant in this kind of soil How it is distributed and what is the quantity really absorbed by the roots of plants If the amount of water used to irrigate represents really what the plants need How the water infiltrates in this type of soil How to quantify the water lost and how to distribute it between plants with an efficient manner for this special architecture If the disposition of the existing species is the best for an efficient use of solar radiation in order to minimise...

Adjustment for Climate

Under humid and calm conditions, the Kc values for full-cover agricultural crops generally do not exceed 1.0 by more than about 0.05. This is because full-cover agricultural crops and the reference crop of clipped grass both provide for nearly maximum absorption of shortwave radiation, which is the primary energy source for evaporation under humid and calm conditions. Generally, the albedos a are similar over a wide range of agricultural crops, including the reference. Because the VPD is small under humid conditions, differences in ET caused by differences in aerodynamic resistance ra between the agricultural crop and the reference crop are also small, especially with low to moderate wind speed. In other words, under humid and calm wind conditions, the Kc values become less dependent on the differences between the aerodynamic components of ETc and ET0. The values for Kcmid and Kcend in Table 5.1 represent conditions where RHmin 45 and U2 2 ms 1. When climatic conditions are different...

HttpbboMTUcomSECOND chance

Susan and I met one such couple, bright young professionals who'd abandoned apartment life and high-paying careers in downtown Chicago once they were expecting their first child. They had wandered around the rural Midwest looking for the ideal place to start their family, finally locating a small tidy farmstead not far from us. We invited them to dinner and showed them the farm after hearing how intent they were to learn about alternative energy choices. They specifically admired our wind generator. As Susan and I saw it, they were experiencing an impulse similar to that which drove people to reconsider their lifestyles during the back-to-the-land-movement of the 1960s. Like those modern pioneers, they wanted to become more energy independent and self-reliant. They wanted to grow organic produce and live simpler lives in rural communities. They had grown up confined by their surroundings and wanted their kids to have more immediate access to nature. And yet they weren't moving so far...

Background and Purpose

The northeast trades blow year-round along the northeast corner of South America where Guyana is situated. Because wind power represents a genuine alternative for many regions, Ocean Arks International launched in 1979 a broad, multidisciplinary project to develop advanced design wind-powered fishing vessels.

Query Shell Module GeoLIMIS Query Shell

Of egg hopper adult etc in the form of spot ratio (Figure 10a, b) as well as meteorological data of selected variable on monthly basis in graphical form. The size of the spot varies proportionately with the value of density. The detailed information of any locust sight could be visualized as a text file using sight-info button. The some of the climate data that could be plotted include temperature, humidity, wind velocity, cloudiness and rainfall in the form of bar or line diagram. For climate data display the EXCEL file must be available in the user's workspace. The package automatically coverts .xls files for corresponding meteorological station into INFO file. In the EXCEL to INFO conversion interface, the user can specify the name of the station along with the year of interest.

Climate suitability for Locust Migration Flight

Migration and long march of adult locusts is a function of temperature, saturation deficit, wind velocity and direction, cloudiness and the upper atmospheric condition i.e. vertical distribution of atmospheric water vapour and mixing zones of upper atmosphere especially in the convergence zones. There is a minimum threshold temperature for flight muscle activation (greater than 17oC), on the other hand above 42 oC thermal inactivation of muscle take place and flight is rare. Most optimum temperature is nearer to 35 oC. Similar to air temperature, humidity also play role in maintaining water balance during flight. Threshold wind velocity required for flight of DL is 13 m s as the swarms prefer to move passively downwind with + -10 degree deviation along its direction. Below the threshold wing movement is limited to hopping and saltation. In a cloudy day however, locusts do not fly. All the above constraints were used in programming logic to evaluate the chances of flight.

Types of Erosion and Its Assessment

Soil erosion losses are often due to a few severe storms with high rainfall intensity and or high rainfall depth 6 , or to high wind velocity values. Figure 4.13 shows that, on a given site, with an invariable land-use and crop management, the long-term average soil loss is dominated by a few and relatively rare events. Soil particles are carried by wind into suspension, by saltation, and by surface creep, depending on their size 1 . Soil particles and small aggregates (< 0.05 mm in diameter, 0) are kept in suspension by air turbulence unless the wind velocity is drastically reduced. Intermediate-size grains (0.05 < 0 < 0.5 mm) move in a series of short leaps, jumping into the air and bouncing back on the soil surface. Soil particles larger than 0.5 mm are not lifted. However, grains that are 0.5 < 0 < 1 mm are bumped along the surface by jumping particles. Grains larger than 1 mm in diameter are non-erodible whereas particles that are 0.5 < 0 < 1 mm are only eroded by...

The Ocean Pickup in Guyana

Buying boats, engines, fuel, and gear from industrial countries. I started to look for more regional solutions that borrowed from the fruits of scientific and engineering knowledge which could be applied in the context of tropical countries and peoples. From the outset I set four basic guidelines or objectives for a project to help fishermen with the development of a new type of working vessel. They were our fishing boat had to be primarily wind powered, but at the same time as fast as most of the motor boats it was to replace construction technologies had to be suitable for building in the tropics, within the communities themselves the primary construction material must be derived from fast growing trees which would be a part of the reforestation projects we intended to promote finally imported components had to be less than twenty percent of the overall costs of the vessel. In this way, by exporting one in five of the vessels built into hard currency countries, input needs could be...

Drought Monitoring Methods

The Rural Development Administration (RDA) provides agricultural weather information to public on a Web site (http ). The daily, monthly, and yearly data in time and space are available for temperature, humidity, radiation, wind speed, precipitation, and so on.

The Penman Monteith ET0 Equation

Assuming a standardized height for wind-speed, temperature, and humidity measurements at 2.0 m (zm zh 2.0 m), and introducing the above parameters into Eq. (5.4), the following aerodynamic resistance results where ra is the aerodynamic resistance (s m-1), and U2 is the wind-speed measurement at 2-m height (ms-1). When wind speed is measured at a height higher than 2.0 m, assuming the logarithmic profile of the wind (Eq. 5.3) the wind speed at 2.0 m (U2) can be obtained from the wind speed at height zm (Uz) by where ET0 is the reference ET (mmday-1) Rn is the net radiation at the crop surface (MJ m-2 day-1) G is the soil heat flux density (MJ m-2 d-1) T is the average temperature at 2-m height ( C) U2 is the wind speed measured at 2-m height (m s-1) (es - ea) is the vapor pressure deficit for measurements at 2-m height (kPa) A is the slope vapor pressure curve (kPa C-1) y is the psychometric constant (kPa C-1) 900 is the coefficient for the reference crop (kJ-1 kg K day-1) resulting...

Case When Wind Speed Data Are Missing

Use of Wind-Speed Data from a Nearby Weather Station. Importing wind-speed data from a nearby station, as for Rs discussed earlier, relies on the fact that airflow above a homogeneous region may have relatively large space variations during the course of a day but small variation over longer periods or even over the day itself. This occurs when air masses are of the same origin or when the same fronts govern airflows in the region where both importing and exporting stations are located. Thus, when a location exists within a given region where wind-speed data are available (U2), it may be possible to utilize the same U2 at a nearby station where wind-speed data are missing. Use of wind-speed data from a nearby weather station is acceptable for daily estimates if climate homogeneity is checked and if daily estimates are to be summed or averaged to several-day periods (7 or 10 days, or time intervals between irrigations) in irrigation scheduling computations. To check validity of...

Areas of High and Low Pressure

A steep pressure gradient and high wind speeds when the systems are farther apart, the wind speeds are lower. A trough line may develop between two low pressure areas, and a ridgeline may develop between two high pressure areas. In general, cloudy or rainy weather is associated with a low pressure center, and clear, sunny weather accompanies areas of high pressure.

Linking Crop Simulation Models To Rs Inputs

The driving variables of crop simulation models are weather inputs comprising daily observations of maximum and minimum temperature, solar radiation, relative humidity, and wind speed as a minimal subset. In a recent review on this subject, Moulin et al. (1998) cited inadequate availability of RS-derived parameters, due to cloud cover problem and intrinsic properties of sensors and platforms, as a major drawback, for adoption of this approach. However, this is a promising area, given the sparse distribution of weather observational network and recent progress in deriving some of these variables from sensors in space. Rainfall, solar radiation and intercepted absorbed PAR have received maximum attention.

Satellite Sensor System

Measure the intensity of the radiation reflected from the object to know the dielectric properties and the roughness of the object. By the use of suitable algorithms these parameters can be translated to the properties of geophysical parameters like soil moisture, ocean surface roughness, ocean surface wind speed, and wind direction, etc. The sensors that use this information are radar, scatterometer, and polarimeters.

Drought Mitigation

Soil evaporation losses and high temperatures can be controlled by applying mulch materials. Shelterbelts are also useful in reducing high evaporation losses. Acacia nilotica spp. Indica shelterbelts have been found useful in controlling wind speeds and thus reducing evaporative losses in the arid regions (Gupta et al., 1983). Shelterbelts of pearl millet provided to summer vegetables modified the crop microclimate and increased the yields of okra and cowpea by 30-40 (Ramakrishna, 1985).

Soil deposition Figure 34 on p 114

High velocity wind can pick up soil particles and keep them airborne until the wind velocity decreases and the soil is deposited back to earth, usually as a fine dust layer. Larger soil particles may also be moved across the ground surface by a process called 'saltation', and again the soil will stop moving either when it comes against an obstruction, or when the wind velocity drops.

Soil Erosion And Processes

Three processes viz. dispersion, compaction and crusting, accelerate the natural rate of soil erosion. These processes decrease structural stability, reduce soil strength, exacerbate erodibility and accentuate susceptibility to transport by overland flow, interflow, wind or gravity. These processes are accentuated by soil disturbance (by tillage, vehicular traffic), lack of ground cover (bare fallow, residue removal or burning) and harsh climate (high rainfall intensity and wind velocity).

Issues on Irrigation Performance

Where P is the pressure (kPa) available at the sprinkler, A P is the variation of the pressure (kPa) in the operating set or along the moving lateral, S represents the spacings (m) of the sprinklers along the lateral and between laterals or spacings between travelers, dn is the nozzle diameter (mm), which influences the sprinkler discharge and the wetted diameter for a given P, WDP represents the water distribution pattern of the sprinkler, and WS is the average wind speed (ms-1). All of the above variables are set at the design stage. The designer, together with the farmer, first has to select the system according to the field, farming characteristics, and crops to be irrigated. Then the designer selects the sprinkler characteristics and spacings. At this stage, variables S, dn, and WDP are set, and the average wind speed WS during operation has been forecasted. Then, the hydraulics calculations are performed to select pipe sizes, pump characteristics, and other system equipment....

C Temperature and moisture control

Vegetation can alter microclimate and create lower temperatures. By shading the areas below them and through the process of evapotranspiration, trees and shrubs produce a cooling effect. They can also regulate temperature by reducing or increasing wind velocity. The placement of vegetation can help cool buildings in summer and allow heat generating sunlight to penetrate in winter (fig. 8-11).

Factors Of Soil Erosion

The soil erosion process is modified by biophysical environment comprising soil, climate, terrain and ground cover and interactions between them (Figure 4). Soil erodibility - susceptibility of soil to agent of erosion - is determined by inherent soil properties e.g., texture, structure, soil organic matter content, clay minerals, exchangeable cations and water retention and transmission properties. Climatic erosivity includes drop size distribution and intensity of rain, amount and frequency of rainfall, run-off amount and velocity, and wind velocity. Important terrain characteristics for studying soil erosion are slope gradient, length, aspect and shape. Ground cover exerts a strong moderating impact on dissipating the energy supplied by agents of soil erosion. The effect of biophysical processes governing soil erosion is influenced by economic, social and political causes (Figure 4).

Windbreaks and Shelterbelts

Windbreaks can be defined as any type of barrier for protection from wind. Commonly, they are associated with mechanical or vegetative barriers for buildings, gardens, orchards, and feedlots. Living windbreaks are known as shelterbelts. These works consist of shrubs and trees that form barriers longer than windbreaks. In addition to reducing wind speed, shelterbelts result in lower evapotranspiration, higher soil temperatures in winter and lower in summer, and higher soil moisture in many cases, these effects can lead to increases in crop yield. A shelterbelt is designed so that it rises abruptly on the windward side and provides both a barrier and a filter to wind movement. Such structures can reduce wind speed to less than half of that in the open, as show in Fig. 4.36 39 . Figure 4.36. Wind velocity distribution (40 cm above ground level) in the vicinity of a windbreak as a percentage of what it would be without the structure. Source 39 . to be effective in filtering the wind and...

Crop Parameters in the Penman Monteith Equation

Assuming thermal neutrality, the wind velocity profile u(z) (ms ') above a plane surface (Fig. 5.2a) can be described by a logarithmic function of the elevation zm (m) above that surface. Figure 5.2. Wind-speed profiles above bare soil (a) and above a cereal-crop canopy (b) when wind speed at 4-m elevation is the same for both conditons. Source 8 . Figure 5.2. Wind-speed profiles above bare soil (a) and above a cereal-crop canopy (b) when wind speed at 4-m elevation is the same for both conditons. Source 8 . where ra is the aerodynamic resistance (s m-1), zm is the height of the measurements of wind velocity (m), zh is the height of air temperature and humidity measurements (m), d is the zero plane displacement height (m), zom is the roughness length relative to momentum transfer (m), zoh is the roughness length relative to heat and vapor transfer (m), uz is the wind velocity at height zm (m s-1), and k is the von Karman constant ( 0.41).

Coordinate Rotation

If the sonic sensor in a covariance system is not well leveled, the covariance calculations will produce errors. One may rotate the data to obtain the accurate ET data. There are different rotation methods. The traditional method is to set the vertical wind velocity (W) to be zero and the mean wind direction to be perpendicular to the W direction (Tanner and Thurtell, 1969 Kaimal and Finnigan, 1994). Other rotation methods were also developed (Lee et al., 2004). The errors (unrotated flux) depend on the instrument tilting level. The larger the tilting angle, the larger the errors (unrotated flux). Usually, the error is about 0-25 _files _frame.htm).


The sensor height, horizontal location, wind speed, and roughness length affect the footprint. One can run a footprint model to find out the appropriate sensor setup location and height for an eddy covariance system. Some footprint models can be found in Horst and Weil (1993), Kristensen et al. (1997), Kormann and Meixner (2001) and online at Figure 3 shows a footprint model results. The model was run under wind speed of 2 m s at 2 m height for an alfalfa field (1-m canopy height). It shows that when the ET sensors are set 0.5 m above the canopy the sources within 150 m contribute 95 of the ET flux measurement when the sensors are 2 m above the canopy sources within a distance of 640 m can contribute 95 of the ET measurement. Figure 3 One footprint model results. Left ET sensors are 2 m above canopy right sensors are 0.5 m above canopy. Wind speed 2 m s at 2 m height, u* 0.1 m s, roughness length 0.1 m (1-m alfalfa field). Figure 3 One footprint model results. Left ET sensors are 2 m...


The behavior of the object is defined by its role in the dialog with other objects. In other words, the behavior of an object represents how the object acts and reacts to the requests of other objects. Object's behavior is represented by a set of messages that the object can respond to. Object Weather should be able to provide solar radiation data to other objects requesting it therefore, it responds to the message getSolarRadiation. Providing weather data such as minimum and maximum temperature, wind speed, rainfall, is part of the behavior of object Weather.

Cultivated Crops

Vegetation is generally the most effective means of wind erosion control. Cultivated crops reduce wind velocity and hold soil against the tractive force of the wind. Woody plants, such as shrubs and trees, can be planted to reduce wind velocities over large areas. Whenever possible, cultural practices should be used before blowing starts, because wind erosion is easier to prevent than to arrest. reduce the surface wind velocity,

XET Rn H G51

The terms on the right side of this equation can be computed from measured or estimated climatic and vegetation factors. The climatic factors include short wave and long wave radiant fluxes from and into the atmosphere (Rn), effects of horizontal air movement (wind speed) and air and surface temperatures on H, and soil heat fluxes (G). Vegetation factors include the resistance to diffusion of vapour from within plant leaves and stems and the resistance to diffusion of vapour from near the vegetation or soil surface upward into the atmosphere.

Design Issues

Uniformity DUor CU, Eq. (5.119) and (5.120) resulting from adjacent sprinklers can be estimated by simulation of the overlap of four adjacent sprinklers in a rectangle, or three in the case of a triangle. The effect of wind can be considered by changing the original circular pattern into an ellipse with radii that vary with the wind speed 91 .

Climate Prediction

The operational use of numerical models in weather forecasting began in the 1960s. Although their usefulness was originally limited, there have been rapid developments since then, and within 10 years the models were able to provide better forecasts of the basic motion field than could be achieved by an unaided human forecaster. These improvements have come about for two reasons. First, the power of computing facilities available has increased enormously. Second, the amount of data available to describe the present atmospheric conditions has greatly increased in recent years. In addition to conventional surface measurements and radiosonde measurements, there are also satellite observations, including satellite soundings and satellite-derived wind speeds obtained from cloud tracking from geostationary satellite images.

Oasis of Tozeur

The field in which we have conducted the experimental protocol is a traditional oasis of about one hectare surrounded by others belonging to other farmers (problem of parcelling out). At the middle of this plot we have installed the 12 m mast with the apparatus to avoid the fetch effect and where the three stories exist and are not traversed by passages or soil canals. This form is repeated in the surrounded oasis. At levels 2, 5 and 12 m of the mast, we fixed three stems of about 2 m length. Every stem included a net pyrradiometer, a pyranomater, a cup anemometer, a temperature probe and a humidity probe. A net pyrradiometer placed 30 cm from the ground to determine the net radiation transmitted across all the oasis and that reaches the soil. The global radiative flux transmitted to the soil is measured by a set of six pyranometers installed arbitrarily to account of horizontal heterogeneity in the canopy structure. The average of the data loggers by those six probes represents the...

Causes of Drought

Cal Convergence Zone (ITCZ), subtropical anticyclones, monsoonal wind systems, tropical cyclones, easterly westerly wave perturbations, subtropical jet streams, East African low-level jet stream, extratropical weather systems, teleconnection with El Ni o Southern Oscillation (ENSO), and quasi-biennial oscillation (Ogallo, 1988, 1991, 1994). In addition, complex physical features such as large inland lakes, mountains, and complex orographic patterns (e.g., the Great Rift Valley) influence rainfall patterns. Lake Victoria in western Kenya is also one of the largest freshwater lakes in the world and has its own strong circulation patterns in space and time. These regional features often induce complex patterns of rainfall anomalies over the region and reduce the chances of extreme positive negative anomalies occurring across the country.

Energy Balance

If the energy is not balanced, there must be problems in one or more of the energy components. Problems in Rn measurements can occur when the sensor is not level or the domes have not been kept clean. Also, the net radiometer must be high enough to represent the average Rn over the canopy cover. Another problem is the measurement of G using soil heat flux plates. The number and distribution of the heat flux plates must be sufficient to give an average value for the canopy conditions. Because measuring the H component with the eddy covariance method involves a simpler technology than does measuring LE, it is assumed that the eddy covariance system measures H accurately except under certain conditions (low wind speed, stable stratification, in high canopies, or in any case when air mixing is significantly reduced or and atmosphere-surface are decoupled. _files _frame.htm). If all the components are measured accurately except LE, then one can calibrate the LE measurements of the eddy...

Renewable Energy Eco Friendly

Renewable Energy Eco Friendly

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable.

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