Assessment of pico hydro as an option for off-grid electrification in Kenya

This paper discusses off-grid electrification options for low-income households in rural Kenya, where less than 2% are grid connected. The paper outlines the electrical load priorities of rural households and describes how these are supplied at present through centrally charged automotive batteries and solar home systems. The recent introduction of pico hydro schemes (<5 kW) to Kenya is discussed, including details of the implementation of the two community schemes and the costs involved. A comparison is made between pico hydro and solar home systems and conclusions are presented on the way forward for off-grid electrification in Kenya.     

Utilization of pico hydro generation in domestic and commercial loads

Pico hydro is a term used to distinguish very small-scale hydropower with a maximum electrical output of five kilowatts (5 kW). It is a good technique of providing electricity to the off-grid remote and isolated regions that suffer energy deficit. Typical pico hydro generator is designed and supported by electrical converting system, batteries and safety equipment so that it can be installed at the residential water pipeline. In pico hydro generation, the environmental impact is negligible since large dams are not involved, and the schemes can be managed and maintained by the consumer. This paper is reviewing the application of hydro generation and particularly focusing on the implementation of pico hydro generation system in University Malaysia Pahang (UMP) Campus-Pekan. This system was designed and simulated using the Matalb simulink blocks. The pico hydro generator has been tested in a real application with a pelton turbine design which utilizes a high pressure of water flowing from the main tank into the faculties. The speed of the turbine and alternator depend on the pressure of the water. In this work, a 1.05 kW alternator is used to charge the battery and the DC power output from a battery is converted into 220 V, 50 Hz.     

Sewage plant powered by combination of photovoltaic, wind and biogas on the island of Fehmarn, Germany

The hybrid system using regenerative sources on the island of Fehmarn was constructed by Telefunken systemtechnik with financial support by the Federal Ministry of Research and Technology, the Government of Schleswig-Holstein, the community of Burg on Fehmarn, Daimler Benz and Telefunken Systemtechnik.The energy plant consists of a photovoltaic generator of 140 kW, a wind energy converter of 250 kW by the Husum Shipyard and a biogas system of 30 kW by Daimler-Benz. This sewage treatment plant receives the total amount of sewage from the town of Burg and the holiday centre Burg-Tiefe.     

Feasibility of the green energy production by hybrid solar + hydro power system in Europe and similar climate areas

This paper analyses the hybrid solar and hydro (SHE) system as a unique technological concept of the sustainable energy system that can provide continuous electric power and energy supply to its consumers and the possibilities of its implementation in Europe and areas with similar climate. The sustainability of such system is based on solar photovoltaic (PV) and hydroelectric (HE) energy as renewable energy sources (RES). For the purpose of connecting all relevant values into one integral SHE system, a mathematical model was developed for selecting the optimal size of the PV power plant as the key element for estimating the technological feasibility of the overall solution. Sensitivity analysis (parameter analysis) was made for the model, where local climate parameters were varied: solar radiation, air temperature, reservoir volume, total head, precipitation, evaporation and natural water inflow. It has been established that, apart from total head (which is to be expected), solar radiation, hydro accumulation size and natural water inflow have the biggest effect on the calculated power of the PV power plant. The obtained results clearly show a wide range of implementation of the new energy source (SHE system), i.e. from relatively cold climates to those abundant in solar energy, but also with relatively small quantity of water, because it only recirculates within the system. All this points to the necessity for further development of hybrid systems (RES + HE systems) and to the fact that they could play an important role in achieving climate objectives.     

电力市场环境下风-水电联合优化运行策略研究

为了促进风电场在电力市场环境下的发展,提出了一种风-水电站联合参与电力市场优化运行的策略。该策略综合考虑了从日前能量市场及调节备用容量市场中取得的收益,以期望收益最大化为目标,加入了水电站运行的限制,建立了含全天24个时段的混合整数规划模型,通过求解模型得出了各市场中的最优能量及容量申报,并基于实际的水电站与风电场参数进行了算例仿真。测试结果表明,水电站与风电场联合运行可降低风电出力的随机性对收益的负面影响,经济效益明显;风电出力的波动、能量不平衡的惩罚系数等因素都会对结果造成影响。     

Hydro energy potential of cooling water at the thermal power plant

The hydro energy of the gravity water flow from the coal-fired thermal power plant units to the river in an open cooling system of turbine condensers is determined. On the basis of statistical data for a long time period, the water net head duration curve due to the river annual level change, as well as the reduction of the hydro energy potential due to the thermal power plant overhauls periods, are evaluated in the case study of the Thermal Power Plant “Nikola Tesla B” in Serbia. A small hydro power plant is designed for the utilization of this hydro energy, and the economic benefits of the project are calculated. The internal rate of returns and pay back periods are calculated in dependence of the electricity price and total investment costs. The increase of profitability is assessed, bearing in mind that the plant might be realized as the Clean Development Mechanism project according to the Kyoto protocol. The obtained results show that the project is economically attractive, and it can be carried out with standard matured solutions of hydro turbines available at the market. Even for the relatively low electricity price from small hydro power plants in Serbia of 0.08 €/kW h the internal rate of return and the pay back period are 17.5% and 5.5 years.     

Identification of stakeholders for sustainable renewable energy applications in Cameroon

This paper examined the initiation, funding, realisation and the current state of some renewable energy applications in the West Region of Cameroon. The findings from the study conducted showed that all of the renewable energy applications were initiated by indigenes living outside the beneficiary communities. The lack of fee-for-service tariffs was partly responsible for the failure of a wind electric installation for potable water pumping. Conflicts in a local management committee resulted in the inoperative state of a pico-hydro installation, while the lack of finances accounted for the failure of a PV system of rural Health Centre. Although, some successful results were noted in the activities of African Center for Renewable and Sustainable Technologies (ACREST) involving foreign technical expertise in small scale renewable energy applications, ACREST had difficulties with the implementation of 100 kW micro hydro project. The stakeholders identified for successful renewable energy applications in Cameroon included local management committees, microfinance institutions, Non-Governmental Organisations (NGOs), Renewable Energy Enterprises (REEs) and universities. Local management committees must be in charge of the supervision, operation and maintenance of installed systems as well as revenue collection based on fee-for-service tariffs. Microfinance institutions should grant loans for the acquisition of financially and economically viable off-grid renewable energy systems to communities with monthly installments based on established monthly energy expenditures. NGOs are expected to provide technical assistance for the conception of community projects, the procurement of funding from cooperation partners and for the realisation of projects. REEs should have competence for sizing, installation and post-installation maintenance of renewable energy equipment. Universities must train the technicians and engineers that will be used by NGOs and REEs. This important role has been recognised by the government of Cameroon through the creation of the first Department of Renewable Energy at the University of Maroua in 2008.     

Pico hydro – Reducing technical risks for rural electrification

Very small hydropower (pico hydro) schemes, with an output of less than 5 kW, can be a cost-effective option for the electrification of remote rural communities. Despite the fact that each hydropower site is unique, there is potential for using standardised equipment and low-cost approaches to scheme design. Relatively low equipment costs are possible, particularly if locally manufactured in a developing country, which enable costs per unit of energy output to be lower than small petrol or diesel generators, wind turbines or PV systems.Nevertheless, it is important not to compromise on technical quality of pico hydro schemes, as this may lead to poor efficiency or long periods when the scheme cannot operate, which will affect the financial success of the scheme. In the longer term, inappropriate cost reductions may lead to reduced uptake of the technology. The challenge is therefore to provide engineering designs and implementation methods that can effectively be customised for a wide range of schemes.This paper describes research and development of successful approaches that have been used to enable pico hydropower to be implemented in diverse situations around the globe. It includes an analysis of penstock pipe sizing to achieve optimum economic design.     

A flexible analytical model for operational investigation of solar hydrogen plants

Hydrogen will become a dominant energy carrier in the future and the efficiency and lifetime cost of its production through water electrolysis is a major research focus. Alongside efforts to offer optimum solutions through plant design and sizing, it is also necessary to develop a flexible virtualised replica of renewable hydrogen plants, that not only models compatibility with the “plug-and-play” nature of many facilities, but that also identifies key elements for optimisation of system operation. This study presents a model for a renewable hydrogen production plant based on real-time historical and present-day datasets of PV connected to a virtualised grid-connected AC microgrid comprising different technologies of batteries, electrolysers, and fuel cells. Mathematical models for each technology were developed from chemical and physical metrics of the plant. The virtualised replica is the first step toward the implementation of a digital twin of the system, and accurate validation of the system behaviour when updated with real-time data. As a case study, a solar hydrogen pilot plant consisting of a 60 kW Solar PV, a 40 kW PEM electrolyser, a 15 kW LIB battery and a 5 kW PEM fuel cell were simulated and analysed. Two effective operational factors on the plant's performance are defined: (i) electrolyser power settings to determine appropriate hydrogen production over twilight periods and/or overnight and (ii) a user-defined minimum threshold for battery state of charge to prevent charge depletion overnight if the electrolyser load is higher than its capacity. The objective of this modelling is to maximise hydrogen yield while both loss of power supply probability (LPSP) and microgrid excess power are minimised. This analysis determined: (i) a hydrogen yield of 38–39% from solar DC energy to hydrogen energy produced, (ii) an LPSP <2.6 × 10^?4 and (iii) < 2% renewable energy lost to the grid as excess electricity for the case study.     

Techno-economic review of existing and new pumped hydro energy storage plant

There has been a renewed commercial and technical interest in pumped hydro energy storage (PHES) recently with the advent of increased variable renewable energy generation and the development of liberalized electricity markets. During the next 8 years over 7 GW of PHES capacity will be added to the European network while projects are also planned in the USA and Japan. This paper provides a review of existing and proposed PHES plant and discusses the technical and economic drivers for these developments. Current trends for new PHES development generally show that developers operating in liberalized markets are tending to repower, enhance projects or build ‘pump-back’ PHES rather than traditional ‘pure pumped storage’. Capital costs per kW for proposed PHES in the review region range between €470/kW and €2170/kW, however these costs are highly site and project specific. An emergence has also been observed in recent PHES developments of the use of variable speed technology. This technology, while incurring slightly higher capital costs, offers a greater range of operational flexibility and efficiency over conventional PHES. This paper has primarily been prompted by a lack of detailed information on PHES facilities worldwide and reviews current developments in the context of market and generation mix changes. The most recent large scale review of PHES faculties was undertaken by the American Society of Civil Engineers Hydro Power Task Committee on Pumped Storage in 1996. In the absence of data in the literature on new PHES plant development, this review draws primarily on publicly available information from utilities, government bodies and electricity regulators. In the same context this study is limited to a review region of the European Union, Japan and the United States as information on developments outside these areas is difficult to procure. This paper also gives a review of locations and proposed timelines for new PHES development and provides a thorough up-to-date overview of the development trends of this technology.     

Assessment of the technical usable potential of the TUM Shaft Hydro Power plant on the Aurino River,Italy

Compared to solar and wind powers, micro hydro power is probably the least common of the three readily used renewable energy sources, but it has the potential to produce the most and more reliably power if the plant is placed in the proper location. Furthermore, in the last years the necessity for developing small hydropower plants has increased due to more and more urgent environmental concerns. The Shaft Hydro Power plant developed at the Technical University of Munich (denoted in the following as TUM-SHP plant) is an innovative, environmentally friendly small hydropower plant that has been designed to be installed in the body of a weir with a height between 2 and 10 m and that requires a discharge flow rate of 3 m³/s to achieve the minimum target 50 kW rated power. The purpose of this paper is to present first results of an ongoing research activity aimed at searching proper sites for the installation of the TUM-SHP plant in Italy. The location analysis methodology to search for potential sites is based on the investigation of rivers and weirs with proper features for the installation of the plant and afterwards on the analysis of the protected areas and the already existing water abstractions in the considered territories. The exploitable discharge has been calculated after studying the regional and provincial laws concerning water exploitation and the calculation of the achievable energy has been carried out considering the flow duration curve of the rivers and translating the values at the weirs of interest. The proposed methodology is tested on the key study of the Aurino River that flows in the province of Bolzano, Alto Adige.     

Renewables portfolio standard and regional energy structure optimisation in China

Eastern Coastal areas of China have been developing rapidly since the implementation of reforms and the opening of China's economic markets in 1978. As in most areas of the world, this rapid economic growth has been accompanied by large increases in energy consumption. China's coal-dominated energy structure has resulted in serious ecological and environmental problems. Exploiting renewable energy resources and introducing Renewables Portfolio Standard (RPS) are some of the most important approaches towards optimising and sustaining the energy structure of China. This paper discusses international experiences in the implementation of RPS policies and prospects for using these policies to encourage renewable energy development in China, establishes a concise definition of renewable resources, differentiating between the broad definition (which includes hydro over 25 MW in size) from the narrow definition (which limits the eligibility of hydro to below 25 MW in size), and quantitatively analyses the potential renewable energy target. The research shows that: (1) Under the narrow hydro definition the renewable energy target would be 5.1% and under the broad hydro definition it would be 18.4%. (2) Western China has contributed 90.2% of the total renewable electricity generation in the country (if big and medium hydropowers are not included). Including big and medium hydropower, the figure is 63.8%. (3) Eastern electricity companies can achieve their quota by buying Tradable Renewable Energy Certificates (TRCs or Green Certificates) and by exploiting renewable energy resources in Western China. The successful implementation of the RPS policy will achieve the goal of sharing the benefits and responsibilities of energy production between the different regions of China.     

耦合抽水蓄能的压缩空气储能电站概念研究

[目的]储能是发展新能源、实现碳达峰碳中和目标的基础条件,其中抽水蓄能是最主要的储能方式,但是抽水蓄能依赖地理条件,需要占用大量自然资源,优良的厂址资源十分有限。为了缓解抽水蓄能厂址资源需求与自然资源稀缺的矛盾,提出了一种耦合抽水蓄能的压缩空气储能系统,并从研究思路、概念方案和工程可行性进行分析,从而为抽水蓄能产业发展提供创新解决方案。[方法]围绕提高能量密度,以减小水库容量、降低水库高度差为突破点,运用压缩空气排水的方法,将水泵水轮机替换为压缩机和膨胀机,下库改为封闭结构的承压容器。储能时,压缩机将空气压缩至高压充入下库,并推挤下库内的水至上库。释能时,水从上库返回下库,下库内的压缩空气被推挤出,并经膨胀机释放。这可使相同条件下抽水蓄能的能量转换量提高数倍。为了论证耦合抽水蓄能的压缩空气储能电站的储能效果,设置上、下库高度差300 m,按照低性能和高性能两套设备参数,对40 MW/200 MWh的概念方案进行热力学分析和储能效率计算。[结果]结果表明:在低性能参数条件下,储能效率65.68%,在高性能参数条件下,储能效率70.81%;能量密度1.67 kWh/m³     

压缩空气储能系统的理论分析及性能研究

压缩空气储能技术和抽水蓄能技术是两种最具潜力的电能规模化储存技术。构建了四套压缩空气储能方案,结合热力学第一定律对高压储罐内压缩空气的温度与压力参数的变化规律以及不同储能方案性能进行了比较。研究结果表明,高压储罐在与环境换热较差时,高压储罐的充气过程会经历较为明显的温升现象。200 m3储罐以1.0 kg/s流速充气至10 MPa时,温升幅度为22.46 ℃,储气过程的温升现象降低了储罐的空气容纳能力。在压缩空气储能系统性能方面,四套储能系统的热耗位于4 100 kJ/kW·h至4 200 kJ/kW·h之间,系统效率位于52.30%与56.33%之间。在储能系统效率与对外输出电能总量指标上,高压储罐与环境之间换热性能较好的储能系统均要优于换热条件较差的储能系统。     

Optimal hydro scheduling and offering strategies considering price uncertainty and risk management

Hydro energy represents a priority in the energy policy of Portugal, with the aim of decreasing the dependence on fossil fuels. In this context, optimal hydro scheduling acquires added significance in moving towards a sustainable environment. A mixed-integer nonlinear programming approach is considered to enable optimal hydro scheduling for the short-term time horizon, including the effect of head on power production, start-up costs related to the units, multiple regions of operation, and constraints on discharge variation. As new contributions to the field, market uncertainty is introduced in the model via price scenarios and risk management is included using Conditional Value-at-Risk to limit profit volatility. Moreover, plant scheduling and pool offering by the hydro power producer are simultaneously considered to solve a realistic cascaded hydro system.     

An axial-flux permanent-magnet generator for a gearless wind energysystem

The paper discuses the development of an axial-flux permanent-magnet generator for a gearless wind energy system which aims to demonstrate the feasibility of integrating wind and photovoltaic energy converters for the generation of electricity and to achieve optimum exploitation of the two energy sources. The merits of an axial-flux generator topology are discussed with reference to the particular requirements of an electrical generator for a direct-coupled wind turbine application. The design, construction and test results of a 5 kW, 200 rev/min permanent-magnet generator, to form a 10 kW pilot power plant with a 5 kW photovoltaic array, are presented     

Design and set up of a hybrid power system (PV-WT-URFC) for a stand-alone application in Mexico

The Mexican territory has a large potential for renewable energy development, such as geothermal, hydro, biofuels, wind and solar. Thus, a 2.5 kW hybrid power system (solar, wind and hydrogen) was designed and installed to meet the power demand for a stand-alone application at the University of Zacatecas. The hybrid unit integrates three power energy sources –a photovoltaic system (PV), a micro-wind turbine (WT), a prototype of a unitized regenerative fuel cell (URFC) and energy storage devices (batteries)– in addition to their interaction methodology. The main contribution of this work is the URFC integration to a hybrid power system for the production of H₂ (water electrolyzer mode) and energy (fuel cell mode). These three energy technologies were connected in parallel, synchronized to the energy storage system and finally coupled to a power conversion module. To achieve the best performance and energy management, an energy management and control strategy was developed to the properly operation of the power plant. A meteorological station that has wireless sensors for the temperature, the humidity, the solar radiation and the wind speed provides the necessary information (in real time) to the monitor and control software, which computes and executes the short and mid–term decisions about the energy management and the data storage for future analysis.     

Parametric analysis of a solar energy based multigeneration plant with SOFC for hydrogen generation

Renewable energy-based hydrogen production plants can offer potential solutions to both ensuring sustainability in energy generation systems and designing environmentally friendly systems. In this combined work, a novel solar energy supported plant is proposed that can generate hydrogen, electricity, heating, cooling and hot water. With the suggested integrated plant, the potential of solar energy usage is increased for energy generation systems. The modeled integrated system generally consists of the solar power cycle, solid oxide fuel cell plant, gas turbine process, supercritical power plant, organic Rankine cycle, cooling cycle, hydrogen production and liquefaction plant, and hot water production sub-system. To conduct a comprehensive thermodynamic performance analysis of the suggested plant, the combined plant is modeled according to thermodynamic equilibrium equations. A performance assessment is also conducted to evaluate the impact of several plant indicators on performance characteristics of integrated system and its sub-parts. Hydrogen production rate in the suggested plant according to the performance analysis performed is realized as 0.0642 kg/s. While maximum exergy destruction rate is seen in the solar power plant with 8279 kW, the cooling plant has the lowest exergy destruction rate as 1098 kW. Also, the highest power generation is obtained from gas turbine cycle with 7053 kW. In addition, energetic and exergetic efficiencies of solar power based combined cycle are found as 56.48% and 54.06%, respectively.     

Development of FPGA based power flow monitoring system in a microgrid

In recent decades, smart grid has become increasingly attractive to both energy producers and consumers. Amongst the main challenges for the successful realization of smart grid includes the integration of renewable energy resources, real time demand response and management of intermittent energy resources. Apart from smart grid, the development of micro-grids should take into consideration of issues such as the system performance, modelling, monitoring and controlling of the micro-grids. In particular, the recent advancements in information and communication technologies (ICTs) could facilitate the effective development of the future micro-grid system. The goal of the study is design of a system, based on FPGA, which monitors the power flow of the Microgrids. First of all a MG system installed in the laboratory of Firat University Electrical and Electronics Engineering Department consists of 1.2 kWp grid connected PV system, 5 kW micro hydro turbine, 0.5 kW wind turbine and 0.1 kW fuel cell unit was introduced. Afterwards, for smart-grids, a system of power flow that has a powerful high sampling rate was dwelt upon. During implementations, the data collected from the power system was transmitted to the FPGA cards located in open area by wireless data-monitoring card. This study has contributed to studies of other researchers by means of the monitoring system which has a high sampling frequency.