Wind energy in Sudan : Water pumping in rural areas

New and renewable sources of energy can make an increasing contribution to the energy supply mix of developing countries in view of favourable renewable energy resource endowments, limitations and uncertainties of fossil fuel supplies, adverse balance of payments, and the increasing pressure on the environment from conventional energy generation. Among the renewable energy technologies, the generation of mechanical and electric power by wind machines has emerged as an economically viable and cost effective option. Therefore the Sudanese government has begun to pay more attention to the use of wind energy in rural areas in particular as a cost-effective solution to assist in water pumping and irrigation.     

A comparison of diesel,biodiesel and solar PV-based water pumping systems in the context of rural Nepal

Nepal is heavily dependent on the traditional energy sources and imported fossil fuel, which has an adverse impact on the environment and economy. Renewable energy technologies promoted in the country are regarded as a means of satisfying rural energy needs of the country for operating different rural end-uses. In this context, this article is prepared to investigate energy alternatives to pump drinking water in one of the remote rural village of Nepal, which has no means of running water source. Analyses in this article are based on the formulation of three technical scenarios of water pumping using petro-diesel, jatropha-based biodiesel and solar photovoltaic pumps. The technical system design consists of system sizing of prime mover (engine, solar panel and pumps) and estimation of reservoir capacity, which are based on the annual aggregate water demand modelling. With these investigations, detailed financial modelling is carried out in a spreadsheet to compare the alternatives on the basis of the economic parameters; net present value, equivalent annualised cost and levelised cost of water pumping. Analysis is carried out considering different influential parameters; water head, discharge, incentives on the investments, which have effects on the cost of pumped water. Likewise, in case of biodiesel-based system, different yield rate of jatropha plants is also considered in estimating the cost of producing biodiesel. It is found that for operating a biodiesel-based pumping system for the study area, the levelised cost of pumping 1 L of water is higher than that of a solar pump and even higher when compared with diesel, if the seed yield per plant is less than 2 kg and without subsidy on the investment cost of cultivation and processing. With the productivity of 2.5 kg/plant, a biodiesel-based system is more attractive than that of the diesel-based pump, but still remains more expensive than that of solar pump. From the technical perspective (reliability and easiness in operation) and economic evaluation of the technical alternatives, solar pumping system is found to be the most viable solution to pump drinking water in the project area.     

Financial evaluation of renewable energy technologies for irrigation water pumping in India

An attempt to develop a simple framework for financial evaluation of renewable energy technologies (RETs) such as photovoltaic (PV) pump, windmill pump, biogas and producer gas-driven dual fuel engine pumps for irrigation water pumping has been made. The unit cost of water and unit cost of useful energy delivered by the RETs have been estimated. The monetary benefits that accrued to the end-user have been quantified in terms of the amount of diesel or electricity saved. Financial figures of merit for the investments made in the RETs have been estimated. The effect of fuel price escalation on these measures of financial performance has also been evaluated along with the estimation of the break-even prices of fuels likely to be substituted by RETs. Results of some exemplifying calculations are presented and briefly discussed.     

Analysis of a fuel cell micro-grid with a small-scale wind turbine generator

If electric power is supplied using an independent micro-grid connected to renewable energy, it can flexibly match the energy demand characteristics of a local area. And an independent micro-grid is expected to be effective in cutting greenhouse gas discharge and energy costs, as well as in eliminating the need for an emergency power supply system. Since the output of renewable energy is unstable, other energy equipment needs to cover the stability of output. Thus, the operating conditions of an independent micro-grid that supplies power with natural power sources and fuel cells are investigated. The operation conditions of a fuel-cell independent micro-grid with wind power generation were investigated by numerical analysis. Step loads and an apartment house power load model were analyzed using the dynamic characteristics of a fuel cell obtained from experiments. The output of wind power generation and fuel cells is controlled by proportional-integral control of an independent micro-grid for rapid power demand change.     

PV based water pumping system for agricultural irrigation

This paper investigates the operation and analysis of the photovoltaic water pumping system in detail. Power electronic controllers were designed and developed for the water pumping system using a boost converter along with an inverter followed by an induction motor pump set. The proposed system could be employed in agricultural irrigation under any operating condition of varying natures of solar irradiances and temperatures. The configuration and implementation of the system were described in detail. Further, the detailed method of analysis and simulation characteristics of such PV water pumping system was also presented.With the concern of shortage of fossil fuel, global warming and energy security, the proposed PV based water pumping system can meet the significant demand of electricity and serve for the agricultural sector.     

Arrangement plan for distributed fuel cells installed in urban areas

The independent fuel cell micro‐grid that accommodates power and heat independently without connecting with other power systems is expected to back up power supply in an emergency, and at peak cuts of a power plant, and the effective use of exhaust heat is anticipated. Therefore, this paper analyses the cost minimization problem of the arrangement planning of a fuel cell system, and the feeding order of exhaust heat. An analysis programme for operation plan at the time of connecting a distributed fuel cell with an energy network was developed using a genetic algorithm. The fuel cell energy network was optimized in six buildings to minimize operation costs, facility costs, and the installation costs of the facilities. As a result, the analysis method for the arrangement plan for the capacity of each installed fuel cell, boiler, heat storage tank, and hot‐water circulating pump was clarified. If the hot‐water network of the distributed fuel cell is installed, in the winter of a cold district, facility cost is disadvantageous compared with the conventional method. Copyright © 2007 John Wiley & Sons, Ltd.     

Biogas derived from municipal solid waste to generate electrical power through solid oxide fuel cells

Depleting fossil fuels and the pollution resulting from their consumption indicate an urgent need for clean and dependable alternatives such as renewable energies. Biomass is a free and abundant source of renewable energy. Municipal solid waste (MSW) as one of the main categories of biomass has always been an issue for metropolitan cities. It has, however, a high potential for biogas production. In this study, the technical and economic aspects of generating electrical power through solid oxide fuel cells (SOFCs) powered by injecting biogas derived from Tehran's MSW, as a case study, are investigated. The main objectives of the current study are to identify the power generation capability of the process and find out if it can result in a competitive energy resource. The total amount of obtainable methane through anaerobic digestion of MSW and then the achievable power generation capacity by using the obtained biogas are computed using the electrochemical relations inside the SOFC. The economic calculations are carried out to estimate the final price of the generated electricity, taking into account the major capital and ongoing costs of the required equipment. The effect of variations of MSW composition on the power generation capability and final electricity price is also studied. Moreover, the application of a gas turbine (GT) with the SOFC as a hybrid SOFC–GT system to recover the produced heat by SOFC and its effect on the power generation capability and the final electricity price are investigated. Results indicate that around 997.3 tons day^?1 biomethane can be generated using Tehran's MSW. By using the SOFC, the produced biogas can generate 300 MW_AC electrical power with a final cost of Depleting fossil fuels and the pollution resulting from their consumption indicate an urgent need for clean and dependable alternatives such as renewable energies. Biomass is a free and abundant source of renewable energy. Municipal solid waste (MSW) as one of the main categories of biomass has always been an issue for metropolitan cities. It has, however, a high potential for biogas production. In this study, the technical and economic aspects of generating electrical power through solid oxide fuel cells (SOFCs) powered by injecting biogas derived from Tehran's MSW, as a case study, are investigated. The main objectives of the current study are to identify the power generation capability of the process and find out if it can result in a competitive energy resource. The total amount of obtainable methane through anaerobic digestion of MSW and then the achievable power generation capacity by using the obtained biogas are computed using the electrochemical relations inside the SOFC. The economic calculations are carried out to estimate the final price of the generated electricity, taking into account the major capital and ongoing costs of the required equipment. The effect of variations of MSW composition on the power generation capability and final electricity price is also studied. Moreover, the application of a gas turbine (GT) with the SOFC as a hybrid SOFC–GT system to recover the produced heat by SOFC and its effect on the power generation capability and the final electricity price are investigated. Results indicate that around 997.3 tons day^?1 biomethane can be generated using Tehran's MSW. By using the SOFC, the produced biogas can generate 300 MW_AC electrical power with a final cost of $0.178 kWh^?1. By using the hybrid SOFC–GT, the electrical power capacity is increased to 525 MW_AC, and the final electricity cost drops to $0.11 kWh^?1, which indicates its competitiveness with other common energy resources in the near future, especially by considering different governmental subsidy policies that support renewable energy resources. The considerable environmental benefits of the proposed procedure, from both MSW management and CO₂ emission reduction points of view, make it a promising sustainable energy resource for the future. Copyright © 2016 John Wiley & Sons, Ltd.     

Sustainable application of renewable sources in water pumping systems: Optimized energy system configuration

Eighteen years ago, in Portugal, the expenses in a water supply system associated with energy consumption were quite low. However, with the successive crises of energy fuel and the increase of the energy tariff as well as the water demand, the energy consumption is becoming a larger and a more important part of the total budget of water supply pumping systems. Also, new governmental policies, essentially in developed countries, are trying to implement renewable energies. For these reasons, a case-study in Portugal of a water pumping system was analysed to operate connected to solar and wind energy sources.     

喷油泵柱塞偶件密封与润滑的研究与分析

应用油膜理论和缝隙液流理论,分析了喷油泵柱塞偶件的燃油密封与润滑,提出确定柱塞偶件最小间隙的基本理论与分析方法;在此基础上,针对当前典型直列燃油喷射系统,对喷油泵运行过程中柱塞偶件燃油泄漏、缝隙压力、柱塞腔压力、偶件配合间隙及其变化等进行了模拟计算与分析。为柱塞偶件设计和工艺改进提供了理论依据。     

Steps toward the hydrogen economy

The hydrogen economy is defined as the industrial system in which one of the universal energy carriers is hydrogen (the other is electricity) and hydrogen is oxidized to water that may be reused by applying an external energy source for dissociation of water into its component elements hydrogen and oxygen. There are three different primary energy-supply system classes which may be used to implement the hydrogen economy, namely, fossil fuels (coal, petroleum, natural gas, and as yet largely unused supplies such as shale oil, oil from tar sands, natural gas from geo-pressured locations, etc.), nuclear reactors including fission reactors and breeders or fusion nuclear reactors over the very long term, and renewable energy sources (including hydroelectric power systems, wind-energy systems, ocean thermal energy conversion systems, geothermal resources, and a host of direct solar energy-conversion systems including biomass production, photovoltaic energy conversion, solar thermal systems, etc.). Examination of present costs of hydrogen production by any of these means shows that the hydrogen economy favored by people searching for a non-polluting gaseous or liquid energy carrier will not be developed without new discoveries or innovations. Hydrogen may become an important market entry in a world with most of the electricity generated in nuclear fission or breeder reactors when high-temperature waste heat is used to dissociate water in chemical cycles or new inventions and innovations lead to low-cost hydrogen production by applying as yet uneconomical renewable solar techniques that are suitable for large-scale production such as direct water photolysis with suitably tailored band gaps on semiconductors or low-cost electricity supplies generated on ocean-based platforms using temperature differences in the tropical seas.     

The potential of PEM fuel cell for a new drinking water source

The worldwide water scarcity, especially in the developing countries and arid regions, forces people to rely on unsafe sources of drinking water. There is a pressing need for these regions to develop decentralized, small-scale water utilities. However, more than 50% of the total operating costs associated with such small-scale, water-utility operations are the cost of providing electricity to run water pumps. We think that advances in a variety of renewable and sustainable energy technologies offer considerable promise for reducing the energy required for the production and distribution of water by small-scale water utilities. This paper provides a comprehensive review of the potential for using proton exchange membrane (PEM) fuel cells to provide an alternative supply of drinking water. This system can eliminate the excessive energy requirements that are currently associated with water production. Such alternative water production processes are designed to increase the production rate of drinking water by reducing the amount of water required to humidify the reactant gases during stable cell performance. The principal operational components of PEM fuel cells are reviewed and evaluated, including air stoichiometry, pressure, and cell temperature. Hydrogen-fed fuel cell systems provide sufficient water to meet the potable water needs of a typical household. Furthermore, it is concluded that PEM fuel cells have great promise for decentralized, small-scale, water-production applications, because they are capable of generating sufficient quantities of potable water by operating at maximum power and by increasing the number of polymer membranes.     

Breaking the mould: solar water pumping—the challenges and the reality

Solar (photovoltaic) powered water pumping has the potential to bring sustainable supplies of potable water to millions of people in developing countries. Unfortunately, in many cases the application of the pump technology ignores the sociological and economic needs of the users, leading to lack of maintenance, inappropriate financing schemes, inadequate system management and, ultimately, failure of the pump. This paper investigates some of the issues involved in solar water pumping projects, describes the positive and negative effects that they can have on the community and, in proposing an entirely new type of pump, considers what steps could be taken to ensure future sustainability.     

Assessment of H2- and H2O-based renewable energy-buffering systems in minor islands

The paper assesses the energy and environmental performance of two solutions designed to complement renewable energy (RE) technologies, in stand-alone power system (SAPS) configuration typical of minor Mediterranean islands, by converting the available RE surplus. The studied SAPS, based on the Ventotene island demographic, meteorological and load data, features high renewable energy penetration onto the load power demand, i.e. up to 55.25% share of peak power capacity. Transient models have been developed to simulate the storage process of winter renewable energy surplus and the time-dependent matching among SAPS electric demand and the stochastic renewable power contributions combined with energy surplus conversion systems. The study compares a hydrogen-based system and a desalinated water-production system, proposed as two effective alternatives for renewable energy seasonal buffering in an island context. The comparative analysis of the time-dependent system's behaviour has been investigated with an hourly distribution over the period of one reference year, in terms of fuel consumption and hydrogen system energy storage or desalination capacity. The assessment is carried out by taking performance indicators, SAPS fuel savings, as well as stored and dump power data. The study demonstrates the suitability of both the models for the winter renewable energy buffer, in order to improve to the matching of peak energy and water demands.     

Solar and wind opportunities for water desalination in the Arab regions

Despite the abundance of renewable energy resources in the Arab region, the use of solar thermal, solar photovoltaics, and wind is still in its technological and economic infancy. Great potential exists, but economic constraints have impeded more rapid growth for many applications. These technologies have certainly advanced technically over the last quarter century to the point where they should now be considered clean-energy alternatives to fossil fuels. For the Arab countries and many other regions of the world, potable water is becoming as critical a commodity as electricity. As renewable energy technologies advance and environmental concerns rise, these technologies are becoming more interesting partners for powering water desalination projects. We evaluate the current potential and viability of solar and wind, emphasizing the strict mandate for accurate, reliable site-specific resource data. Water desalination can be achieved through either thermal energy (using phase-change processes) or electricity (driving membrane processes), and these sources are best matched to the particular desalination technology. Desalination using solar thermal can be accomplished by multistage flash distillation, multi-effect distillation, vapor compression, freeze separation, and solar still methods. Concentrating solar power offers the best match to large-scale plants that require both high-temperature fluids and electricity. Solar and wind electricity can be effective energy sources for reverse osmosis, electrodialysis, and ultra- and nano-filtration. All these water desalination processes have special operational and high energy requirements that put additional requisites on the use of solar and wind to power these applications. We summarize the characteristics of the various desalination technologies. The effective match of solar thermal, solar photovoltaics, and wind to each of these is discussed in detail. An economic analysis is provided that incorporates energy consumption, water production levels, and environmental benefits in its model. Finally, the expected evolution of the renewable technologies over the near- to mid-term is discussed with the implications for desalination applications over these timeframes.     

水—水热泵替代工质循环性能及其动态可燃特性研究

水－水热泵在建筑能量系统的环境保护,开发和利用余热资源中起着重要作用,为了研究这种热泵的工质替代问题,就目前具有成功实验结果的水－水热泵的替代工质之一：R32／134a进行热力学及循环性能模拟分析,结果发现R32／134a当浓度为（30／70）时作为常规水－水热泵工质具有较大的优势,针对此替代物在生产使用中的重要环节一贮存和运输中的安全性问题,研究其在贮运过程中由于泄漏引起的动态燃爆特性,得出了具有实际应用价值的规律。     

Economic feasibility of solar pumping

Two major questions concerning the economic feasibility of solar pumping are addressed. The first of these is concerned with finding a least-cost solar system by considering the alternative use of either thermal or water storage. The second involves the determination of areas where solar energy would be economically competitive with electricity or fuel as a power source for pumping installations.A linear programming solution is developed to find the optimal combination of thermal and water storage for a solar installation. The formulation is then extended to determine a least-cost system when hybrid systems are considered. A hybrid system may incorporate a combination of solar, electric and fuel power inputs. The concept of a breakeven “critical” distance from existing infastructure for solar installations is developed, and an example problem is provided to illustrate typical values of this distance and to show its sensitivity to the base energy costs and rate of inflation for those costs. It appears that electrical pumping is probably the most economical alternative provided that electric infrastructure is located nearby. Fuel power will also be more economical than solar if there is a source of fuel near the proposed pumping site. However, solar systems may be economically competitive when considered for installation at realistic distances from existing infrastructure.     

Experimental studies on cofiring of coal and biomass blends in India

Concerns regarding the potential global environmental impacts of fossil fuels used in power generation and other energy supplies are increasing worldwide. One of the methods of mitigating these environmental impacts is increasing the fraction of renewable and sustainable energy in the national energy usage. A number of techniques and methods have been proposed for reducing gaseous emissions of NO_x,SO₂ and CO₂ from fossil fuel combustion and for reducing costs associated with these mitigation techniques. Some of the control methods are expensive and therefore increase production costs. Among the less expensive alternatives, cofiring has gained popularity with the electric utility producers. This paper discusses the ‘gaseous emission characteristics namely NO_x,SO₂, suspended particulate matter and other characteristics like specific fuel consumption, total fuel required, actual and equivalent evaporation, total cost of fuel, etc. from a 18.68 MW power plant with a travelling grate boiler, when biomass was cofired with bituminous coal in three proportions of 20%, 40% and 60% by mass. Bagasse, wood chips (Julia flora), sugarcane trash and coconut shell are the biomass fuels cofired with coal in this study.     

Reliability/cost implications of PV and wind energy utilization insmall isolated power systems

The application of renewable energy in electric power systems is growing rapidly due to enhanced public concerns for adverse environmental impacts and escalation in energy costs associated with the use of conventional energy sources. Photovoltaics and wind energy sources are being increasingly recognized as cost effective generation sources in small isolated power systems primarily supplied by costly diesel fuel. The utilization of these energy sources can significantly reduce the system fuel costs but can also have considerable impact on the system reliability. A realistic cost/reliability analysis requires evaluation models that can recognize the highly erratic nature of these energy sources while maintaining the chronology and interdependence of the random variables inherent in them. This paper presents a simulation method that provides objective indicators to help system planners decide on appropriate installation sites, operating policies, and selection of energy types, sizes and mixes in capacity expansion when utilizing PV and wind energy in small isolated systems     

Comparing the cost of electricity sourced from a fuel cell-based renewable energy system and the national grid to electrify a rural health centre in India: A case study

The provision of electricity is a key component in the development of a country’s health care facilities. This study was performed to estimate the cost of powering a rural primary health centre, in India with a decentralised renewable energy system. The costs were also compared between a decentralised renewable energy system and providing electricity from a grid source. The critical or break-even distance that makes electricity from a decentralised renewable energy system cost effective over that from a grid source was determined. The decentralised renewable energy system considered was a hydrogen-based fuel cell for the generation of electricity with hydrogen extracted from biogas obtained from biomass. The software program HOMER was used for the simulation analysis. The cost of a decentralised renewable energy system was found to be between seven times and less than half that of conventional energy, and the break-even distance was between 43.8 km to a negative distance for varying ranges of input component costs. The results of this study indicated that the use of a decentralised renewable energy system to power a rural primary health centre is both feasible and cost effective, and may even be cheaper than using electricity from a grid source.     

An integrated system framework for fuel cell-based distributed green energy applications

The environmental pollution and diminishing conventional fuel sources and global warming problems make it more attractive for considering renewables as alternative energy sources, such as solar, wind and micro hydro, etc. Recent advances in hydrogen and fuel cell technologies further facilitate these energy options to supply electrical power to various communities. Hydrogen fuel cell systems coupled with renewable energy sources stand out as a promising solution. This paper presents an integrated system framework for fuel cell-based distributed energy applications. Five components are included in this framework: a physical energy system application, a virtual simulation model, a distributed coordination and control, a human system interface and a database. The integrated system framework provides a means to optimize system design, evaluate its performance and balance supplies and demands in a hydrogen assisted renewable energy application. It can either be applied to a distributed energy node that fulfills a local energy demand or to an energy-network that coordinates distributed energy nodes in a region, such as a hydrogen highway. The proposed system framework has been applied in the first phase of our multi-phases project to investigate and analyze the feasibility and suitability of hydrogen fuel assisted renewable power for a remote community. Through integration with an available renewable energy profile database, the developed system efficiently assists in selecting, integrating, and evaluating different system configurations and various operational scenarios at the application site. The simulation results provide a solid basis for the next phase of our demonstration projects.