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Urban environment can be considered a complex system consisting of the engineered pavement physical structure over the buried utilities (water, gas, sewer) network embedded in the background soil environment. Assessment of buried pipeline civil infrastructures using proximal geophysical methods in such instances has to consider possible interferences, difficulties, and incorrect inferences. In this study, we have conducted a numerical modelling investigation to understand and evaluate how electrical resistivity profiling (ERP) and ground penetrating radar (GPR) can be utilised to provide subsurface information that otherwise may not be possible if either one of the techniques is used. A model geometry consisting of a typical pavement structure (asphalt, base/subbase, and background soil) with a single 2 m pipe buried at a depth of 1 m was used. Strong lateral variations in soil type were incorporated over the short pipe section in order to understand the complexities that can arise, especially with ERP measurements. The 3D electrical resistivity measurements were simulated in Comsol using the 4-probe method, while the 2D GPR measurements were simulated in gprMax to obtain the subsurface information. The results from both ERP and GPR were used to develop a practical framework that can be utilised by relevant authorities for proximal condition assessment of their buried assets. It was suggested that ERP can be used as a first level screening tool over the whole pipeline length, followed by discretely selected GPR scans in order to further gain information on the pipe health. This is attractive practically since, following delineations of a large pipe section into shorter subsections, advanced condition assessment approaches that are generally intrusive in nature can then be economically deployed within the subsections suspected of experiencing significant corrosion damage.

Timely monitoring of pavement sub-surface layer thickness and condition evaluation is essential to ensure stable pavement performance and safety under heavy traffic loading. In addition, accurate estimation of pavement layer thicknesses is required for condition evaluation, overlay design/ quality control assurance, and structural capacity evaluation of existing pavements to predict its remaining service life. Traditionally this vital information is ascertained through coring/drilling and visual inspections. In contrast to these current techniques, ground-penetrating radar (GPR) is a non-destructive technique gaining popularity in pavement asphalt layer thickness estimation and structural condition monitoring. Its high-quality data contains vital pavement condition information, and survey costs are reasonably economic. In this work, GPR data were acquired along a toll road in Queensland, Australia, using the GSSI 4-channel SIR30 GPR unit. Asphalt layer thickness information is considered an important input parameter for condition assessment, pavement performance, and lifetime modelling. This work presents an automated segmentation framework to evaluate pavement conditions for a large pavement network. The developed algorithm uses GPR asphalt thickness data as input and generates segments with decision boundaries utilising a cascaded k-means and DBSCAN approach that works in two steps: 1) centroid initialisation using k-means algorithm, 2) clustering using DBSCAN algorithm. Presented in this paper is the workflow of the cascaded method that is applicable to automated analysis of GPR asphalt thickness data. The performance of the cascaded k-means and DBSCAN algorithm was evaluated in terms of entropy compared with traditional k-means and traditional DBSCAN algorithms. The results show that the proposed method outperforms its constituents. Based on the results of this study, the method presented in this paper is cost-effective, economical and robust for segmenting large pavement network with GPR data.

Field evidence revealed that buried cast iron water pipes can deteriorate through large localized corrosion patches with lengths greater than 1 m, formed by a cluster of small pits. This study inve...

Experiments were carried out to characterise the influence of soil water retention properties on the corrosion of a cast iron specimen buried in Fraser River silt. The corrosion rates were measured at different degrees of saturation using standard corrosion tests, along with separate water retention tests for the Fraser River silt. Building on previous work on this topic, a numerical model solving moisture flow, oxygen diffusion, electrical conductivity and their coupled influence on metallic corrosion in unsaturated soil was developed. The experimental data and preliminary numerical modelling results were then used as inputs to a field-scale numerical model to examine climate-induced moisture migration around a pipeline and the resulting levels of corrosion. The time-dependent corrosion mass loss and the resulting loss in pipe wall thickness of a buried pipeline were modelled, and it was demonstrated that the cyclic climatic variations predominantly perturb the corrosion rates during the initial cycles, and subsequently a gradual corrosion rate arises depending on general climatic conditions. Further analysis of the influence of electrical resistivity on the levels of corrosion revealed that a decrease in resistivity due to effects such as seawater intrusion or naturally saline soils may result in a significant increase in the levels of localised corrosion.

Polymeric spray and cured-in-place-pipe liners have attracted the attention of water utilities as alternatives for renovation of deteriorated cast iron pipes. Circumferential defects, in the form of existing gaps, ring fractures or failed joints, may exist in cast iron pipes and they may significantly influence the performance of the lined pipes under applied loads. Literature review showed that limited research has been conducted to investigate the effect of circumferential defects. This paper aims to comprehensively examine the mechanical performance of polymer lined cast iron pipes with circumferential defects, using finite element analyses, and derive equations based on the finite element results for engineering design. Three different failure modes, namely, lining through existing gaps in pressurized host pipes, formation of gaps for pressurized lined pipes subjected to axial movements, and pressurized lined pipes with ring fractures under bending, are comprehensively studied. After validation of the developed numerical models for each of the failure modes, parametric studies were conducted considering different pipe properties, liner properties, loading conditions and interface properties. Equations were then derived based on the numerical results using non-linear regression for the three failure modes to facilitate the use of the results in practice. It was found from this study that for all three modes a reduction in the ratio of the cast iron pipe modulus to liner modulus will result in an increase in the normalized maximum stress, which is defined as the ratio of the maximum stress to internal pressure in the liner. This effect is most significant for formation of gaps for pressurized lined pipes subjected to axial movements and pressurized lined pipes with ring fractures under bending. It was also found that by increasing the friction coefficient or reducing the ratio of liner wall thickness to pipe diameter, the normalized maximum stress in the liner increases. Among the three failure modes, the normalized maximum stress in the liner for formation of gaps for pressurized lined pipes subjected to axial movements was affected the most.

A mechanistic understanding of the process of underground corrosion is important for modeling pipeline deterioration. In this study, a time-dependent multiscale numerical model incorporating electrochemistry and soil hydrology is developed. The model realistically simulates soil moisture and aeration conditions and their influence on anodic/cathodic activity without prior definition. In this manner, both micro- and macrocell corrosion and their evolution with time are simulated along with the effects of differential aeration. The model was validated with low-alloy cast iron corrosion data from the United States National Bureau of Standards corrosion exposure study. The effect of soil aeration in controlling soil corrosiveness was simulated with suitable boundary conditions. It was demonstrated that macrocells arising due to differential aeration can lead to elevated levels of corrosion in pipelines, especially in fairly aerated soils.

A geophysical investigation of a hot spring system located in Rabulu, Fiji, was carried out from October 2014 to March 2015. The investigation covered a survey area of 6075 m2. Self-potential (SP), ground temperature and soil carbon dioxide (CO2) concentrations were measured and investigated for their distribution characteristics and inter-linkages. Results indicated obvious anomalous zone at the hot spring discharge site. The SP profile analysis highlighted thermal water upwelling zones and elevation-driven subsurface groundwater pathways. Measurement of subsurface temperatures up to 1 m depths revealed increasing temperatures, indicating potentially high thermal gradients in the area. Surface soil CO2 distributions also agreed with SP and ground temperature results. The overall result of the study demonstrated that synchronised measurements of SP, ground temperature and soil CO2 can be instrumental in identifying anomalous zones near the hot spring sites. Other parameters such as spring water temperature, discharge rate and energy flux estimates from the spring were calculated and analysed. The high-dense multi-parameter data coverage allowed interpretation of geothermal features at a scale never conducted in Fiji before. The near-surface investigations reported in this study corroborate previously suggested steady geothermal activity in the region, deserving further detailed investigation.

The ability of steel reinforced concrete to withstand long service life is ensured by the strong binding between the concrete and the rebar. Although rebar corrosion deterioration in the presence of chlorides is well known, it is important to note that these anions are never present in isolation, i.e., other cations are also present within the exposed environment. Consequently, a study was conducted to investigate the rebar deterioration due to chlorides in the presence of different cations. A well-controlled laboratory experiment for assessing the corrosivity of sodium chloride, potassium chloride and magnesium chloride was conducted. The galvanostatic pulse technique was used to investigate the concrete-steel interfacial structure, which was modelled after a modified Randles circuit. Analysis revealed influences of the associated cations during the rebar corrosion process. A normalisation approach was used to compare chloride attacks on the rebar due to different salt solutions. Results suggest that chloride attacks in the presence of sodium cations are relatively corrosive.

Periodic inspection of pipeline conditions is an important asset management strategy conducted by water and sewer utilities for efficient and economical operations of their assets in field. The Level 1 pipeline condition assessment involving resistivity profiling along the pipeline right-of-way is a common technique for delineating pipe sections that might be installed in highly corrosive soil environment. However, the technique can suffer from significant perturbations arising from the buried pipe itself, resulting in errors in native soil characterisation. To address this problem, a finite element model was developed to investigate the degree to which pipes of different a) diameters, b) burial depths, and c) surface conditions (bare or coated) can influence in-situ soil resistivity measurements using Wenner methods. It was found that the greatest errors can arise when conducting measurements over a bare pipe with the array aligned parallel to the pipe. Depending upon the pipe surface conditions, in-situ resistivity measurements can either be underestimated or overestimated from true soil resistivities. Following results based on simulations and decoupling equations, a guiding framework for removing pipe influences in soil resistivity measurements were developed that can be easily used to perform corrections on measurements. The equations require simple a-prior information on the pipe diameter, burial depth, surface condition, and the array length and orientation used. Findings from this study have immediate application and is envisaged to be useful for critical civil infrastructure monitoring and assessment.

Polymeric spray lining is a trenchless pipe rehabilitation technique which is rapidly gaining momentum, due to the increasing costs of open trenching or lift-and-relay replacement. An accurate assessment of the effectiveness of polymeric spray-lining products is best conducted on specimens from field spray-liner installations, since field application of the polymer spray varies in application quality and installation length in comparison with laboratory-controlled application. Furthermore, experimental testing on spray-lined pipes needs to be as close as possible to actual field conditions. This paper presents results from a comprehensive testing program intended to evaluate the performance of actual in-service, spray-lined pipes extracted from the field. Material property tests on the liner material and full-scale tests on the lined pipe composites were conducted. Results indicated that despite degradation of the material in comparison to the initial conditions, the lined pipes were able to withstand operational pressures with circular through-wall holes in the host pipe of up to 50 mm diameter. Circumferential cracks in the host pipe were also successfully spanned under water pressure and pipe bending. However, water leakage, which can occur at the interface of the cement mortar liner and the polymeric liner was identified as a major issue that could compromise lined pipe systems. Recommendations for the mitigation of this issue are provided on the basis of the experimental observations.

Cast iron pipes buried between the 1860s and 1980s still account for a significant proportion of the Australian water transmission network, and failure rates of cast iron trunk mains have risen in the past decades. In Australian cities, the manufacturing methods and corrosion mitigation techniques used in cast iron pipes are strongly correlated with the pipeline burial year. This paper introduces an approach to summarise the remaining in service cast iron trunk mains into several cohorts, in order to identify the critical pipelines with high potential of longitudinal fracture in pipe barrels. Despite the various manufacturers and casting moulds used in Australian cast iron pipes, two major cohorts, static and spun cast iron pipes, were identified based on manufacturing methods, material properties, microstructural analysis and wall thicknesses. A statistical analysis confirmed that spun cast pipes have higher burst rates and relatively short life spans than statically cast pipes, evidently due to ...

The constitutive modelling of unsaturated soil behaviour within the MPK framework using data fusion approaches are discussed to envisage a practical approach for the evaluation and monitoring of landslide-prone areas. The present study focuses on improvements in subsurface suction distribution estimations via electrical resistivity tomography (ERT), which can be used to generate quasi-continuous suction profiles (QCSP) for numerical modelling. An explicit petro geophysical transfer function between suction and resistivity is presented herein, which was derived from the Waxman-Smits electrical resistivity model and the Van Genuchten equation for soil water retention curves. For efficient numerical modelling, a selective correction approach (SCA) is presented for petro geophysical transfer function updating procedure. The data acquisition and analysis architecture are envisaged within a data cloud platform, which is highly attractive within the context of internet-of-things (IoT). Although the focus of this work is on suction estimations, a similar approach can be used for estimation of other constitutive variables required within the MPK framework.

Aging infrastructure such as water pipelines is a growing problem that will require urgent solutions within the next few decades. These pipeline assets have been in service beyond their designed service live (50 years) and failures are inevitable. Therefore, water utilities are seeking strategic pipe replacement techniques to prioritise their limited budget and proactive failure prevention methods to avoid catastrophic, costly pipe failures. In this paper, the process of a leak initialising from such a defect, followed by a catastrophic burst within a water supply network is explained and the applicability of Leak-Before-Break (LBB) concept for proactive pipe failure prevention are discussed. Full-scale laboratory experiments and a field case study are utilised to validate the proposed research hypothesis. It is believed that this novel (within the context of water pipes) pipe failure prevention strategy would provide a robust pathway for proactive future water pipe asset management.

This paper presents a reliability-based methodology for failure assessment of reinforced rock slopes subjected to bolt corrosion. Strength failure of the rock bolt, bond failure between the rock bolt and the grout and bond failure between the rock and the grout are considered and their load effects are treated as stochastic processes. The failure probability of each failure mode was evaluated using first passage probability, in which two auto-correlation functions are considered for the load effect processes. The correlations among failure modes are also considered for system reliability analysis. The application of the proposed methodology is demonstrated by a worked example. Sensitivity analysis is also undertaken to identify most influential parameters on slope failure probability. It is found that the type of auto-correlation functions and the correlation length of the load effect processes significantly affect the failure probability of each individual failure while the correlations among the failure modes considerably influence the system failure probability. It is also found that cohesion and friction angle are most influential on the failure probability for all failure modes while the corrosion model and the initial bond strengths are only influential for the bond failure between the rock bolt and the grout and both bond failures respectively.

Time-domain induced polarisation (TDIP) methods are routinely used for near-surface evaluations in quasi-urban environments harbouring networks of buried civil infrastructure. A conventional technique for improving signal to noise ratio in such environments is by using analogue or digital low-pass filtering followed by stacking and rectification. However, this induces large distortions in the processed data. In this study, we have conducted the first application of wavelet based denoising techniques for processing raw TDIP data. Our investigation included laboratory and field measurements to better understand the advantages and limitations of this technique. It was found that distortions arising from conventional filtering can be significantly avoided with the use of wavelet based denoising techniques. With recent advances in full-waveform acquisition and analysis, incorporation of wavelet denoising techniques can further enhance surveying capabilities. In this work, we present the rationale for utilising wavelet denoising methods and discuss some important implications, which can positively influence TDIP methods.

Advancement of knowledge on the behaviour of unsaturated soil through constitutive modelling is an area of active research within the geotechnical community. Given that most of the Earth surface can be considered unsaturated and most of the geotechnical infrastructures constitute of compacted soil, advancements in predictive modelling are needed for reliable management of geo-infrastructures. Moreover, the complex processes of soil collapse, shear failures and excessive soil swelling underneath artificial and (or) natural structures necessitates continuous monitoring or periodic assessment of relevant field parameters. To address this problem, geophysical and proximal optical sensing methods can be utilised for high-density spatial characterisation of relevant soil properties and features for monitoring of geotechnical structures. In this paper, we combined knowledge in unsaturated soil behaviour on the basis of the recent Monash-Peradeniya-Kodikara (MPK) framework and surface/subsurface soil characterisation using proximal soil sensing techniques and discrete sensing for ground-truthing to envisage a combined observation and predictive modelling paradigm for geo-infrastructures. We discussed the concepts by demonstrating its usefulness in predicting potential landslides and slope stability issues. The overarching impact of the ideas discussed in this paper is expected to generate new research priority areas that can be highly beneficial in monitoring geo-infrastructures subjected to climate loading. Furthermore, we identified future research areas that can provide modern benefits of geophysical techniques in geotechnical problems. In particular, we note that developments in pedophysical transfer functions relating soil resistivity to commonly utilised geotechnical soil properties can be highly beneficial to geotechnical practitioners involved in monitoring of critical geo-infrastructures.

Identification of pipe sections prone to corrosion induced failures is essential and in these regards geophysical resistivity methods are normally used to provide assessments of soil corrosivity. Some recent works presented in literature indicate that ground penetrating radar techniques maybe useful for such purpose in addition to its common use - detecting buried utilities. To investigate such possibility we conducted a numerical simulation study to establish the proof of concept that GPR techniques can indeed be used to provide insights on the severity of corrosion damage on pipes; a clear advanced capability over resistivity methods. It was found that 500 MHz GPR systems are suitable for assessing corrosion damage in buried pipes. Most importantly, it was found that pipes sections that have undergone relatively high corrosion can be delineated on the basis of the intensities of the typical hyperbolic reflections, which is significantly perturbed by the characteristic conductivity and permittivity profiles set up around pipes due to corrosion activity. Results from this study indicate that GPR techniques has the potential to provide strong enhancements in capabilities and accuracies at Level 1 pipeline condition assessment programs.

The galvanostatic pulse technique was applied in the soil environment, allowing the characterisation of corrosion rate and the double layer capacitance formed at the metal/soil interface. A well-controlled laboratory framework for assessing potential corrosivity amongst different soil samples was presented. The galvanostatic pulse technique and the suggested framework were used to evaluate the effect of varying clay and chloride contents on corrosion of common ferrous pipeline alloys. A coupled moisture-chloride effect induced by clay was used to explain the features of the electrical double layer. The study provides a reference for calibrating future corrosion experiments in soil media.

Corrosion rates in sand, silt, and clay were investigated at various degrees of saturation (Sr) revealing that all three soil types have a distinct optimum Sr at which the corrosion rate is maximised. Sand, silt, and clay showed maximum corrosion currents at Sr ≈0.5, Sr ≈0.7, and Sr ≈0.8 respectively. We show that the optimum moisture level at which the corrosion rate becomes a maximum for a given soil type corresponds to the air transition point related to its water retention curve. We provide an explanation for this phenomenon elucidating previous observations, and highlight implications to current engineering practice.

In generally, predictive maintenance of induction motors is well suited for small to larger scale industries in order to reduce downtime, increase efficiency and reliability. In this paper, the vibration and temperature of the induction motor is analyzed in order to gather specific information that can predict motor's bearing failure. Well analyzed vibration signal easily shows the difference between the running operation of the healthy and faulty motor. Using IoT, this paper shows Real Time Condition Monitoring System for Industrial Motors.

A systematic study was developed to investigate the quality of air in Suva, the capital city of Fiji Islands. This is the first work of its kind in the South Pacific Islands and was aimed at characterizing the elemental abundances in total suspended particulate (TSP) matter in Suva’s air. Aerosol samples were collected from 11 locations in Suva during the period 2000–2003 using a high-volume sampler. Concentrations of some heavy metals and other trace elements in these atmospheric aerosols were investigated by neutron activation analysis and gamma spectrometry. Concentrations of total suspended particulates for residential, traffic and industrial areas were found to be in the range 9-43, 20-58 and 33-91 μg/m 3 , respectively. The elements sodium, iron and zinc have been observed in relatively higher concentrations than other elements. Moreover, calculated enrichment factors for some elements (such as arsenic, bromine, cobalt, chromium and antimony) reveal possible anthropogenic inputs into air mainly through automobile exhaust emissions.

Studies on hot spring regions in Fiji have been conducted by several workers such as (Cox 1982), (Healy 1960) and (Autar 1996). These studies identified several distributions patterns that require further investigation and analysis. There are almost no published works continued from the efforts of previous workers. In the present work, a geophysical investigation of a hot spring was conducted using advanced geophysical techniques to build upon conclusions from preceding works. The Tavua hot spring site, located in northern Viti Levu within the Nakauvadra range was investigated using several geophysical techniques. Self-potential (SP) and soil temperature profiling were carried out within the hot spring. The SP study provided useful information on subsurface fluid flow, clearly delineating upward and downward flows. Good correspondence between SP and soil temperature was also observed. Other hydrological parameters viz., discharge rate and outflow water temperature were evaluated to determine the energy flux of the hot spring. The present methodological study aims to a) investigate the distribution of various geophysical parameters within this area, and b) provide a baseline investigation so that feasibility of further detailed explorations can be determined. To our knowledge, there is no recent published literature concerning geophysical studies on hot springs making this the first of its kind investigation in Fiji.

Selected results of a study of the metal-insulator transition in n-type nanocrystalline Si:H,F down to T ≈ 30 K are presented. The transition occurs around an electron density of 1 × 10 19 cm −3 . On the insulator side, hopping conduction in a parabolic density of states near the Fermi level dominates below room temperature. On the metallic side, the conductivity reflects electron-electron interactions, with a temperature dependence of T 1 2 at temperatures less than 270 K.

We presented a laboratory method for investigating the spectral induced polarization (SIP) response of soil samples and the implications for overall soil corrosivity. This study was important in order to advance the understanding of soil electrical properties, which can be used diagnostically to assess infrastructure integrity. Presently, isolated measurements of soil resistivity are the only (electrical) parameters that are routinely used to identify soil corrosivity. Our work showed that the low frequency soil spectral properties may lead to better soil corrosivity assessments when coupled effects from clay and salinity were present. In particular, unfolding and interpreting the soil spectral properties using the Cole-Cole model revealed that the normalized chargeability parameter mn was highly appropriate for identifying the character of potentially corrosive soils.

Recent attention on effects of climate change in the Pacific island countries (PIC’s) have focused on a multitude of areas which are at risk in the Pacific region. These include food security, flora and fauna, land accessibility, groundwater contamination and so on. These aspects are essential for sustainable development of the small island states in the Pacific region. One issue, which appears synonymous with climate change in the Pacific is sea-level rise. The rising sea level can have detrimental effects on civil infrastructure since its intrusion further inland can lead to deterioration of nearby civil metallic infrastructure due to corrosion. Since metropolisation of major PIC’s are mainly near the sea or along coast line, this presents a significant problem within the overall paradigm of sustainable development. In this regards, a study was undertaken to investigate the influences of different chloride salts (i.e. NaCl, KCl, MgCl2) on the corrosion of steel re-inforcing bars (rebar’s) in concrete mortars. This study is important to understand structural health conditions, especially for foundations in ground, and to understand the corrosion intensities in the presence of different cations, which can be significantly controlled by groundwater migration. The galvanostatic pulse technique was used to evaluate the effect of varying chloride contents of different salts on rebar corrosion. Results from this study are presented in an attempt to provide a conceptual model for understanding the interaction of aforementioned salts with metallic infrastructure. A holistic discussion is presented which are important for sustainable development in the PIC’s.

Grab sediments, collected from 11 locations from the Pacific Ocean floor in the region between Suva Peninsula and Kadavu Island, Fiji, were investigated for concentrations of 20 elements using neutron activation and high-resolution gamma ray spectroscopy techniques. The sediments were collected at distances between 5-35 km from the mainland and at ocean depths ranging from 500 to 2000 m. A comparison of the elemental abundances of these sediments with those of the Suva lagoon and other nearby locations indicates that the ocean sediments are likely to be derived from sediments washed out to sea from the mainland. The sediments also show no evidence of any metal contamination from the industrial activity in the Suva metropolitan area.

The levels of total suspended particulates (TSP) within the complex of a steel factory (Fletcher Pacific Steel Fiji) have been investigated through high volume air sampling. The levels of TSP inside and outside (in the ambient environment) the factory has been found to be in the range of 121-339 and 33-80 μg m-3 respectively. The levels inside the factory exceed the WHO guideline by a factor of 2-4. The management of the factory was very proactive to determine the air quality for records and to safeguard the health and safety of all the employees, contractors, and visitors. At the request of the factory, the exposed filters were analysed by neutron activation and gamma-ray spectroscopy techniques and the results are presented.

Renewable energy generated as much electric power worldwide in 2005 as one-fifth of the worlds nuclear power plants excluding large hydropower that itself accounts to 16% of world’s electricity (REN 21 2005). Renewable energy is gaining prominence in providing the world’s primary energy needs. Solar, wind, biomass, and geothermal are considered as the premier renewable energy resources that are in direct competition with the conventional fuels. The fastest growing technology has been the photovoltaic (grid connected), however, wind power is steadily growing with an estimated existing capacity of 56 GW by the end of 2005 (REN21 2005). Wind power has been used for many centuries to provide mechanical and electrical power for a variety of uses. Since the beginning of the last century, however, the most important use has been the generation of electricity for supply to rural and remote areas, as well as providing energy into the electrical distribution system, i.e. the national grid. World wind energy capacity has doubled every three years since 1990 and each doubling has been accompanied by a 15% reduction in the price of wind turbines (Milbrow 2005). Turbine size has increased from 600 - 800 kW to 1 - 3 MW with blade diameters from 60 -100 m and the energy costs (c/kWh) has declined by at least 18% and is now half those of 1990. The practical size of a wind turbine is determined by the assessment of annual electrical load, site conditions, wind resource, installed cost, and utility rate (Lodge 2005).The major countries that utilize wind power for electricity generation include the USA, Spain, Germany, India, Britain, Sweden, Netherlands, China, and Denmark. However, Russia, South Africa, Brazil, and Mexico are in the transitional stage to develop large-scale commercial markets. The basic theory of the extraction of energy from a wind turbine is found in any standard textbook on wind energy. The power in the wind varies as the cube of the wind speed. If an obstacle is placed in the path of the wind, the wind’s kinetic energy does work on the obstacle and wind energy is converted to other forms, including the kinetic energy of rotating parts. Thus a turbine or rotor placed in the path of wind, with wind speed