Remote Area Power Supply Research Articles

Direct Power Control of a PWM Rectifier Fed Autonomous Induction Generator for Wind Energy Applications

In this paper, a control strategy for a stand alone induction generator (IG) driven by a variable speed wind turbine for use in remote area power supply is presented. The IG is excited simultaneously by a capacitor bank and a PWM rectifier. During the voltage build up process, there is a variation in the flux linkage of the induction generator. The variation of the magnetising inductance is taken into account due to saturation of the core. To achieve the main goal of the control system, which consists to keeping the DC link voltage constant regardless of the magnitude of the load power, a direct power control (DPC) technique is proposed. In DPC approach, the converter switching states are selected directly by a switching table based on the instantaneous errors between the controlled and estimated values of active and reactive power.The simulation calculation was achieved using MATLAB®-SIMULINK® package and results are presented to support the theoretical discussion.

Design and Research on Wind-Solar-Diesel Hybrid Generating System at High Altitude

At the high altitude, the construction of wind-solar-diesel hybrid power station is a effective measure to solve the problem of power supply in remote areas. Combining with the local natural resources, in order to ensure the reliability of the power supply and heighten the price-performance ratio of the system, designing the wind-solar-diesel hybrid power station in reason is of great significance for increasing the prevalence rate of the wind-solar-diesel hybrid power station.

Standalone Operation of Wind Turbine-Based Variable Speed Generators With Maximum Power Extraction Capability

The application of variable speed wind generators in hybrid remote area power supply (RAPS) systems provides opportunities for improved voltage and frequency control together with maximum power point tracking (MPPT), where limited research outcomes exist. The study presented in this paper covers two such hybrid systems: 1) permanent magnet synchronous generator (PMSG) and 2) doubly fed induction generator (DFIG) as wind turbine technologies together with a battery storage and a dump load. The battery storage system and dump load are able to assist in maintaining the active power balance during over and under generation conditions as well as sudden load changes. Through simulation studies, it has been demonstrated that both RAPS systems are able to regulate the load side voltage and frequency within the acceptable limits while extracting the maximum power from wind, which is an inherent capability of variable speed generators. The two RAPS systems and their associated control strategies have been developed and their performance is investigated using SimPowerSystems blocksets in MATLAB.

Design of a Dynamic Control System for Standalone Solar-Hydrogen Power Generation

Solar-hydrogen systems employing a photovoltaic array and storage of surplus energy in the form of hydrogen are an attractive zero-emission and low-maintenance solution for remote area and other standalone power supplies to replace diesel and PV- battery systems. A number of experimental and demonstration solar-hydrogen systems have been constructed and tested, but little work has been done to date on an overall control unit for such systems. The present paper thus focuses on the design of a control unit for a solar-hydrogen system with hydrogen generation via a proton exchange membrane (PEM) electrolyser, compressed gas or metal-hydride hydrogen storage, and a PEM fuel cell. Particular emphasis is placed on the design of an integrated maximum power point tracker and load splitter that can dynamically supply power to meet the load and divert any surplus to operate the PEM electrolyser and produce hydrogen for storage. Two alternative algorithms for the execution of the load splitting function are outlined. Measurements of the typical variation of solar radiation over a very short time scale, together with typical household load variations, are used to suggest an appropriate unit time interval within which the system operates at selected optimal settings. The main components of a planned experimental program to measure the performance of the control unit for a small standalone solar PV-hydrogen system are presented.

Small Scale Power Generation using Low Grade Heat from Solar Pond

This paper presents the potential of thermoelectric generators as a power generation system using heat from the salinity gradient solar pond. A thermoelectric cell bank module with 16 thermoelectric generators was designed and fabricated. The module was tested under varying temperature differentials to determine its performance characteristics and suitability to generate power from a typical salinity gradient solar pond. The thermoelectric generator system was designed to be powered by the hot and cold water from the salinity gradient solar pond. The system is capable of producing electricity even on cloudy days or at night as the salinity gradient solar pond acts as a thermal storage system. The results obtained have indicated significant prospects of such systems to generate power from a low grade heat for remote area power supply.

Electric power generation from solar pond using combined thermosyphon and thermoelectric modules

Salinity-gradient solar ponds can collect and store solar heat at temperatures up to 80 °C. As a result, these water bodies act as a renewable source of low grade heat which can be utilized for heating and power generation applications. In this paper, design and test result of the combined system of thermosyphon and thermoelectric modules (TTMs) for the generation of electricity from low grade thermal sources like solar pond is discussed. In solar ponds, temperature difference in the range 40–60 °C is available between the lower convective zone (LCZ) and the upper convective zone (UCZ) which can be applied across the hot and cold surfaces of the thermoelectric modules to make it work as a power generator. The designed system utilizes gravity assisted thermosyphon to transfer heat from the hot bottom to the cold top of the solar pond. Thermoelectric cells (TECs) are attached to the top end of the thermosyphon which lies in the UCZ thereby maintaining differential temperature across them. A laboratory scale model based on the proposed combination of thermosyphon and thermoelectric cells was fabricated and tested under the temperature differences that exist in the solar ponds. Result outcomes from the TTM prototype have indicated significant prospects of such system for power generation from low grade heat sources particularly for remote area power supply. A potential advantage of such a system is its ability to continue to provide useful power output at night time or on cloudy days because of the thermal storage capability of the solar pond.

Theory, modelling and performance measurement of unitised regenerative fuel cells

Abstract Unitised Regenerative Fuel Cells (URFCs) based on Proton Exchange Membrane (PEM) technology provide a promising opportunity for reducing the cost of the hydrogen subsystem used in renewable-energy hydrogen systems for remote area power supply. A general theoretical relationship between cell potential and current density of a single-cell URFC operating in both fuel-cell and electrolyser modes is derived using the Butler–Volmer equation for both oxygen and hydrogen electrodes, and accounting for membrane resistance and mass transport losses. Modifying the standard Butler–Volmer equation with a denominator term containing two additional ‘saturation’ parameters to reflect mass transport constraints generates voltage–current curves that are much closer to experimentally obtained polarisation curves in both modes. The theoretical relationship is used to construct a computer model based on Excel and Visual Basic to generate voltage–current curves in both electrolyser and fuel cell modes for URFCs with a range of membrane electrode assembly characteristics. Hence the influence of key factors such as exchange current densities and charge transfer coefficients on cell performance is analysed. Experimental results for voltage–current curves from singe-cell URFCs with a number of different oxygen-side catalysts are reported, and compared to the theoretically modelled curves. Generally values have been found for exchange current densities, charge transfer coefficients, and saturation current densities that give a close fit between the empirical and theoretically generated curves. The values found conform well to expectations based on the catalyst loadings, in partial confirmation of the validity of the modelling approach. The model thus promises to be a useful tool in identifying electrodes with materials and structures, together with optimal catalyst types and loadings that will improve URFC performance.

Remote area power supply system technologies in Western Australia: New developments in 30 years of slow progress

The escalation of the renewable energy capacity growth rate in remote pastoral Western Australian (WA) off-grid stand-alone power supply (SPS) systems over the last decade was extraordinary. The expansion was encouraged by subsidised renewable energy technologies, enabling components and system installation costs. This research quantifies and explores the changes over time of rated outputs of renewable and conventional energy components, and energy demand in SPS systems in pastoral WA over the last 30 years. This research revealed parallel increases in conventional generation unit output ratings, renewable energy capacity, and energy demand over the past decade. Whilst recent developments are encouraging, there remain many technical, social, economic and regulatory barriers to overcome the small-scale renewable energy SPS system industry in WA. A lack of mandatory standards has resulted in a minority of poor SPS systems and some aggravated owners in regions where reliability and reputation are paramount. After investing many tens of thousands of Australian dollars (AUD) on new capital equipment, minor system integration issues are becoming a frustratingly common cause of system failure for remote SPS system owners.

Design and cost analysis of low head simple reaction hydro turbine for remote area power supply

This paper is aimed at exploring the performance characteristics of a simple reaction hydro turbine for power generation. Using principles of conservation of mass, momentum and energy, the governing equations have been identified for an ideal case of no frictional losses. The paper also describes the conception of a cross-pipe rotor for remote area electricity production. Using the ideal governing equations an optimized geometry of the rotor was selected for the working head of 5 m. Theoretical analysis of the self-governing characteristics has been presented. Experiments were carried out for 2, 3, 4 and 5 m head and evaluated against theoretical results. Split pipe turbine model is presented with detail layout, while different methods of experimentation are explored for different output requirements with varied heads. Various losses in the system are discussed, quantified and included in the graphical format. It is also demonstrated that the experimental power outputs do not have the same tendencies as theoretical predictions and decreases due to jet interference beyond a certain rotational speed as it passes the maximum power point.

Optimal coupling of PV arrays to PEM electrolysers in solar–hydrogen systems for remote area power supply

Renewable energy–hydrogen systems for remote applications constitute an early niche for sustainable hydrogen energy. Optimal matching between the photovoltaic (PV) system and the electrolyser is essential for maximum electrical energy transfer and hydrogen production. This paper investigates the possibility of achieving near maximum power transfer between a directly coupled PV array and a proton exchange membrane (PEM) electrolyser stack by finding an optimal configuration of series–parallel connection of both the PV panels and the PEM cells. The application of this procedure to four 75 W PV modules directly coupled to five 50 W PEM electrolyser stacks (250 W in total) predicts an energy transfer of over 94% of the theoretical maximum. Initial experiments indicate an actual energy transfer of around 95%. Clearly, energy-efficient direct coupling is advantageous economically since the costs of an electronic coupling system (around US$ 700 kW - 1 ) are avoided entirely.

Alternative energy facilities based on site matching and generation unit sizing for remote area power supply

This paper presents the decision support technique and influencing factors in the design of an integrated solar-wind power system for stand-alone applications. Results of investigations on application of alternative energy facility like wind, photovoltaic (PV), and Integration of wind–PV power generating systems for Remote Area Power Supply have been presented. A weather model-based site matching of equipment and a simple numerical algorithm for generation unit sizing have been presented. The program has been used to determine the optimum generation capacity and storage needs for a stand-alone Wind, PV, and integrated wind–PV system for a remote site in India (Sukhalai situated near Suktawa in Hoshangabad district of Madhya Pradesh) that satisfies a typical load. Generation and storage units for each system are properly sized in order to meet the annual load demand for the above three scenarios. Annual average hourly values for load, wind speed, and insolation have been used for analysis. The results are used to justify the use of renewable energy source as a reliable option for remote areas.

Development of ultra-battery for hybrid-electric vehicle applications

Transport is one of the largest sources of human-induced greenhouse gas emissions and fossil-fuels consumption. This has lead to a growing demand for hybrid-electric vehicles (HEVs) to reduce air pollution and consumption of fossil fuels. CSIRO Energy Technology has developed the ultra-battery, a new technology that will reduce the cost and boost the performance of batteries in HEVs. The ultra-battery is a hybrid energy-storage device, which combines an asymmetric supercapacitor, and a lead-acid battery in one unit cell, taking the best from both technologies without the need for extra electronic controls. The capacitor will enhance the power and lifespan of the lead-acid battery as it acts as a buffer in discharging and charging. Consequently, this hybrid technology is able to provide and absorb charge rapidly during vehicle acceleration and braking. The ultra-battery has been subjected to a variety of tests. To date, results show that the discharge and charge power of the ultra-battery is ∼50% higher and its cycle-life is at least three times longer than that of the conventional lead-acid counterpart. Furthermore, the ultra-battery is able to be produced as either flooded-electrolyte or valve-regulated designs in the existing lead-acid factory and also able to reconfigure for a variety of applications, such as conventional automobile, power tool, forklift, high-power uninterruptible power supply and remote-area power supply. The prototype ultra-batteries have been constructed and are under laboratory evaluation and field trial. The success of the ultra-battery will obviously make HEVs more affordable and widespread. This, in turn, will reduce greenhouse gas emissions in the urban environment and the consumption of limited supplies of fossil fuels.

Energy storage in remote area power supply (RAPS) systems

Preliminary cost analyses indicate that hybrid RAPS systems are more economically attractive as a means to provide electricity to remote villages than are alternatives such as 24 h diesel generation. A hybrid remote area power supply (RAPS) system is being deployed to provide 24 h electricity to villages in the Amazon region of Peru. The RAPS system consists of modules designed to provide 150 kWh per day of utility grade ac electricity over a 24 h period. Each module contains a diesel generator, battery bank using heavy-duty 2 V VRLA gelled electrolyte batteries, a battery charger, a photovoltaic array and an inverter. Despite early difficulties, the system in the first village has now commenced operation and the promise of RAPS schemes as a means for providing sustainable remote electrification appears to be bright.

Power Converter Line Synchronization Using a Discrete Fourier Transform (DFT) Based on a Variable Sample Rate

Line synchronization of grid connected power converters is a well recognized problem when the grid is weak, or derives from a remote area power supply with poor frequency regulation. Such systems can suffer significant line voltage distortion due to notches caused by power device switching and/or low frequency harmonic content, which can easily corrupt the output of a conventional zero crossing detector. This paper presents a method of filtering the incoming grid voltage using a recursive discrete Fourier transform (DFT). The filter provides a high degree of noise immunity but does produce a phase shift between the incoming grid voltage and the filtered output voltage when the DFT time window does not match the grid period. Two methods of compensating this phase shift are presented, based on tracking the drift in the phase predicted by the recursive DFT. The first method makes a deadbeat adjustment to the time window (thereby changing the sampling rate) while the second approach calculates the phase error based on the linear phase response of the DFT. These compensation algorithms can correct for discrepancies of at least 25% between the DFT time window and the system period, and can track grid frequencies with slew rates as high as 40 Hz/s with negligible phase shift (<2/spl deg/) between the grid voltage input and the filtered output waveforms.

05/00236 Demand side management for remote area power supply systems incorporating solar irradiance model: Al-Alawi, A. and Islam, S. M. Renewable Energy, 2004, 29, (13), 2027–2036

05/00236 Demand side management for remote area power supply systems incorporating solar irradiance model: Al-Alawi, A. and Islam, S. M. Renewable Energy, 2004, 29, (13), 2027–2036

Demand side management for remote area power supply systems incorporating solar irradiance model

This paper presents a technique for generating the daily electricity load profile for remote areas in the Middle East from first principles, using diversified demand. The generated load profile includes the energy required to run a small desalination unit to provide the necessary freshwater. Demand side management (DSM) is used in this study to smooth out the daily peaks and fill valleys in the load curve to make the most efficient use of energy resources. Finally, the load profile is compared with real data for six houses collected from Safri area in the Sultanate of Oman. These data may be used as the basis to obtain load profiles of other remote areas of the Middle East since the weather and social factors are similar. The modified hourly variation factor based on weather and economic and social factors of the Middle East is obtained. A solar irradiance model is incorporated in the system to utilise the solar energy available in the Middle East region.

Advanced management strategies for remote-area power-supply systems

Abstract An operating strategy based on partial-state-of-charge (PSoC) operation has been developed for a remote-area power-supply (RAPS) system in Peru. The facility will power an entire village and comprises a photovoltaic array, a bank of gel valve-regulated lead-acid (VRLA) batteries, a diesel generator, and a sophisticated control system. The PSoC schedule involves operation below a full state-of-charge (SoC) for 28 days, followed by an equalization charge. The schedule has been evaluated by operating a 24 V battery bank under simulated RAPS conditions in the laboratory. It is found that operation between 58 and 83% SoC causes the negative-plate potentials to move to significantly more negative values during charging as the PSoC duty progresses. This behaviour is undesirable, because it can lead to the activation of a preset limit and a subsequent reduction in system efficiency. Lowering the PSoC window to 47–72% SoC or 40–65% SoC during the 28-day cycle is found to stabilize the negative-plate potentials. The behaviour of the negative plates in gel batteries is very similar to that observed for absorptive glass mat (AGM) designs of VRLA batteries operated in hybrid electric vehicles.

Installation and operation of a large scale RAPS system in Peru

In 1997, International Lead Zinc Research Organization Inc. (ILZRO), Solar Energy Industries Association (SEIA), and the Ministry of Energy and Mines (MEM) of Peru signed a Memorandum of Understanding to facilitate the installation of hybrid remote area power supply (RAPS) systems in the Amazon region of Peru. Many remote villages in this vast region have either no or limited electricity supplied by diesel generators running a few hours per day. Subsequently, ILZRO sponsored the engineering design of the hybrid RAPS system and SEIA supported a socio-economic study to determine the sustainability of such systems and the locations for pilot installations. In mid-1998, the Peruvian government approved the design of the system. ILZRO then began efforts to obtain governmental and inter-governmental funding to supplement its own funds to underwrite the cost of manufacture and installation of the systems in two villages in the Amazon region. Additional major funding has been received from the Global Environmental Facility (GEF) administered by the United Nations Development Program (UNDP) and from the Common Fund for Commodities (CFC). Funds have also been received from the US Department of Energy, the International Greenhouse Partnership (Australia) and the Peruvian government.The RAPS system consists of modules designed to provide 150kWh per day of utility grade ac electricity over a 24h period. Each module contains a diesel generator, battery bank using heavy-duty 2V VRLA GEL batteries, a battery charger, a photovoltaic array and an ac/dc inverter. The batteries and electrical components are housed in modified shipping containers. The modules can be installed with a new generator or retrofitted to an existing generator. The charging and discharging regime of the batteries has been recommended by a study carried out by CSIRO, which has simulated the RAPS operation. The system will employ a partial-state-of-charge (PSOC) regime in order to optimize the life of the batteries, which have a projected life of 8–10 years. A remote monitoring system will consist of a satellite link between each of the remote area power systems and one or more central hosts. The system operator will be able to obtain actual operational status of the system and will be able to change set points and to force operation of certain functions in order to test the system.Preliminary cost analyses indicate that such RAPS systems are more economically attractive to provide electricity to remote villages than other alternatives, including 24h diesel generation and grid extension.The past 5 years have provided a number of lessons learned, particularly related to dealing with government agencies in a developing country, overcoming logistical problems such as shipping long distances and dealing with difficult climate and terrain. Despite difficulties encountered, the promise of RAPS systems as a rapidly growing market for lead-acid batteries appears to be bright given the demand for sustainable remote electrification.

Benefits of partial-state-of-charge operation in remote-area power-supply systems

Many people throughout the world are remote from electricity networks and do not have access to reliable power. Remote-area power-supply (RAPS) systems offer a reliable and cost-effective alternative to grid connection. Achieving adequate performance from such systems requires appropriate componentry and well-designed control systems/strategies. A relatively new operating methodology—known as partial-state-of-charge (PSoC) operation—is now finding application in the field. The strategy, which can give a three-fold increase in the lifetime energy-delivery of gelled-electrolyte batteries compared with that obtained using traditional charging procedures, is to be employed in RAPS systems in Peru. The PSoC algorithms will be formulated and trailed in the laboratory, and then installed in the Peru facilities where they will be monitored and controlled remotely via a satellite link-up. This approach allows the algorithms to be fine-tuned in situ, and will ensure that system efficiency and battery lifetime are maximised. Use of the PSoC concept is expected to provide a battery lifetime of 8 years.

ALABC 2000 — the way ahead

Many battery energy-storage applications are currently undergoing a progressive change away from the traditional flooded lead–acid battery to a valve-regulated design which offers convenience both in operation (spill-proof, able to be rapidly recharged) and in reduced maintenance. At the same time, there are large changes in prospect in the applications themselves. In the transport sector, it appears that at least part of the largest of all present markets, the 12/14 V starting, lighting and ignition (SLI) battery, will be replaced by a 36/42 V system. Also, there may be some substitution of electric and/or hybrid electric vehicles for vehicles that employ internal combustion engines alone. There is also, currently, rapid growth in the use of valve-regulated lead–acid batteries for telecommunications and there is enormous potential for future growth in remote-area power supplies (RAPSs). The present paper reviews some of the salient aspects of the research and development programs that are being carried out in order to meet these challenges.