Site location analysis for small hydropower using geo-spatial information system

Recently, the necessity for developing small hydropower (SHP) plants has emerged due to the increase in environmental concerns. Although there remains an abundant of potential sites for SHP plants in Korea, SHP development has scarcely been performed since the 1990s due to the absence of a suitable approach and economic feasibility. Such a situation encourages decision makers to develop a systematic approach for SHP development. The purpose of this study is to propose a new location analysis methodology to search for potential SHP sites using GSIS (Geo-Spatial Information System). The location analysis in this study focuses on establishing the criteria and methodology for searching for alternative locations rather than selecting the most suitable site among the alternatives. By applying the newly developed methodology, a large area can be precisely surveyed within a short period of time and we expect to be able to use the method in policy making for SHP development by improving the convenience for the user. The newly developed methodology was applied to the upper part of Geum River Basin, in Korea, and found six potential SHP sites. As a fundamental work, this study will be beneficial to the future activation of SHP development.     

Modelling, optimisation and performance evaluation of a parabolic trough solar collector steam generation system

A parabolic trough collector (PTC) system used for steam generation is presented in this paper. PTCs are the preferred type of collectors used for steam generation due to their ability to work at high temperatures with a good efficiency. The modelling program developed called PTCDES is used to predict the quantity of steam produced by the system. The flash vessel size, capacity and inventory determines how much energy is used at the beginning of the day for raising the temperature of the circulating water to saturation temperature before effective steam production begins. Optimisation of the flash vessel presented here uses a simplified version of the program PTCDES. System performance tests indicate that the modelling program is accurate to within 1.2% which is considered very adequate. Finally, the theoretical system energy analysis is presented in the form of a Sankey diagram. The analysis shows that only 48.9% of the available solar radiation is used for steam generation. The rest is lost either as collector or thermal losses.     

计及风电和小水电的发电系统可靠性评估研究

根据分布式电源随机输出功率的特点,利用集群技术,将较多的机组出力状态集合成较少的组群,建立了风电多容量机组可靠性模型和小水电机组改进的双状态模型。针对现有发电系统停运容量模型存在计算繁琐的问题,运用停运容量预备表优化排序,减省计算步骤和时间。将容量模型和日尖峰负荷模型结合,形成新型发电系统的裕度评估体系,采用某含多风电场和遍布小水电的地区的发电系统作为算例,编制MATLAB程序计算了一系列可靠性指标,定量分析了分布式电源对发电系统可靠性的影响。     

Modelling and performance study of a continuous adsorption refrigeration system driven by parabolic trough solar collector

This article suggests a numerical study of a continuous adsorption refrigeration system consisting of two adsorbent beds and powered by parabolic trough solar collector (PTC). Activated carbon as adsorbent and ammonia as refrigerant are selected. A predictive model accounting for heat balance in the solar collector components and instantaneous heat and mass transfer in adsorbent bed is presented. The validity of the theoretical model has been tested by comparison with experimental data of the temperature evolution within the adsorber during isosteric heating phase. A good agreement is obtained. The system performance is assessed in terms of specific cooling power (SCP), refrigeration cycle COP (COP_cycle) and solar coefficient of performance (COP_s), which were evaluated by a cycle simulation computer program. The temperature, pressure and adsorbed mass profiles in the two adsorbers have been shown. The influences of some important operating and design parameters on the system performance have been analyzed.The study has put in evidence the ability of such a system to achieve a promising performance and to overcome the intermittence of the adsorption refrigeration systems driven by solar energy. Under the climatic conditions of daily solar radiation being about 14 MJ per 0.8 m² (17.5 MJ/m²) and operating conditions of evaporating temperature, T_ev = 0 °C, condensing temperature, T_con = 30 °C and heat source temperature of 100 °C, the results indicate that the system could achieve a SCP of the order of 104 W/kg, a refrigeration cycle COP of 0.43, and it could produce a daily useful cooling of 2515 kJ per 0.8 m² of collector area, while its gross solar COP could reach 0.18.     

Modelling and performance of a copolymer solar water heating collector

The performance of a solar flat-plate thermal collector wholly manufactured in a copolymer material is studied. The influence of different parameters of the system such as the insulation thickness, the flow rate and the fluid layer thickness is analysed. Thermal performance, productivity and efficiency of such a solar system is presented for a Mediterranean site. Yearly mean efficiencies are about 56.5% in no wind and about 49.0% for a wind speed of 5 m s⁻¹. The use of polymer materials reduces the collector weight by 50% in comparison with a traditional metal collector, this renders easier installation.     

离网型户用风力发电机性能测试系统的开发

本文为离网型户用风力发电机虚拟仪器性能测试系统的研制 ,利用NI公司推出的软件LabVIEW及相关配套硬件设备 ,设计了风力机基本性能参数的测试系统。通过对风力发电机输出电流、输出电压、大气温度、大气压力、风速等实验数据的分析和处理 ,得到风力发电机输出特性曲线 ,从而为评估和改进风力发电机的性能提供依据     

Thermal performance of a small oil-in-glass tube thermal energy storage system during charging

A very small oil-in-glass tube thermal energy storage (TES) system is designed to allow for rapid heat transfer experiments. An electrical hot plate in thermal contact with a steel spiral coil (SSC) is used to charge the TES system under different hot plate temperatures and under different average charging flow rates. Thermal performance during charging is presented in terms of the axial temperature distribution, the axial degree of thermal stratification, the total energy stored and the total exergy stored. The energy and exergy delivery rates of the energy delivery device (EDD) are also evaluated in relation to the thermal performance of the storage system. Results of charging the storage system under different hot plate temperatures indicate that there is an optimal charging temperature for optimal thermal performance. The results also indicate that exceeding this optimal temperature leads to a degradation of the thermal performance due to increased heat losses. Charging at the same temperature conditions under different flow rate regimes suggests that there is an optimal charging flow rate. This optimal flow rate is a compromise between achieving a greater heat transfer rate in the EDD and achieving a greater degree of thermal stratification in the TES system.     

Municipal water supply dams as a source of small hydropower in Turkey

In Turkey the laws published in recent years succeeded in promoting the utilization of renewable energy for electricity generation. After the publication of Renewable Energy Law on 18 May 2005 in Turkey there occurred a boost in renewable energy projects along with hydropower development. Thus, the economically feasible hydropower potential of Turkey increased 15% and the construction of hydropower plants also increased by a factor of four in 2007 as compared to 2006. From this perspective, this paper was aimed to evaluate the small hydropower potential of municipal water supply dams of Turkey and discussed the current situation of SHP plants in terms of the government policy. It is estimated that the installing small hydropower plants to exiting 45 municipal water supply dams in Turkey will generate 173 GWh/year electric energy without effecting the natural environment. For a case study, Zonguldak Ulutan Dam and its water treatment plant has been investigated in detail.     

Modelling of a new hydro-compressed air-storage system

The interest in energy storage systems is increasing, since it provides an excellent solution to store the low-cost excess energy from the energy sources, which are available at peak demand hours. This paper presents a new compressed-air storage system that combines ambient air and hydraulic oil, in order to store energy in compressed-air form and benefit from the advantages of both pneumatic and hydraulic systems. The process consists of charging and discharging cycles, however, this paper investigates the discharging cycle, where a new technique of Small-Scale Compressed Air Energy Storage (SS-CAES) system is realised. The new idea in RC-CAHES is to obtain higher efficiency in energy conversion machines during charging and discharging processes with numerous advantages over conventional types of energy storage systems. This study demonstrates the effectiveness of this technique by proving that it has higher efficiency than a similar Compressed Air Energy Storage (CAES) systems.     

The trend of small hydropower development in China

The paper makes an analysis of the status quo and existing issues of small hydropower (SHP) in China and based on the logistic growth curve model forecasts the installed capacity of SHP and cost of newly built SHP in the future. It also explores the opportunity of the clean development mechanism (CDM) in SHP projects and puts forward suggestions and recommendations on enhancing the SHP market competitiveness.     

Modelling a hydropower plant with reservoir with the micropower optimisation model (HOMER)

Hydropower with water accumulation is an interesting option to consider in hybrid systems, because it helps dealing with the intermittence characteristics of renewable energy resources. The software HOMER (version Legacy) is extensively used in research works related to these systems, but it does not include a specific option for modelling hydro with reservoir. This paper describes a method for modelling a hydropower plant with reservoir with HOMER by adapting an existing procedure used for modelling pumped storage. An example with two scenarios in southern Brazil is presented for illustrating and validating the method explained in this paper. The results validate the method by showing a direct correspondence between an equivalent battery and the reservoir. The refill of the reservoir, its power output as a function of the flow rate and installed hydropower capacity are effectively simulated, indicating an adequate representation of a hydropower plant with reservoir is possible with HOMER.     

Modelling and simulation of a solar absorption cooling system

A detailed numerical simulation model is developed for a commercially available solar absorption chiller. The model incorporates the performance data of a Yazaki-manufactured water-cooled system. We take into consideration the variation of the COP and cooling water temperature. Using a summer season's meteorological data for an arid location in the Sahara desert, the system performance is computed for different collector types, areas and storage volumes. The results show that an optimum storage volume/collector area ratio exists. Also a high solar fraction can be obtained with relatively small areas of collectors, even when the collectors are of the inexpensive type. The interesting feature was that the system operated at design load conditions with generator temperatures as low as 80°C owing to the fact that very low cooling water temperatures are available in the dry conditions of the Sahara. The study establishes the high potential of solar operated, water-cooled absorption coolers especially for arid conditions.     

Modelling and simulation of the dynamic performance of a natural-gas turbine flowmeter

Installations involving fluids often present problems in terms of the dynamic performances of their different parts. These problems can be analysed and dealt with at the design stage. This means that both the technologists who design the thermohydraulic process and those who carry out the regulation and control must be involved in the process from the early stages of the design.     

Design and performance of a small shrouded cretan windwheel

A Cretan-type windwheel is attractive because of its design simplicity, low cost, durability and ease of construction by semi-skilled labour from a variety of indigenous materials. Utilising a 0·64 m diameter cycle wheel as the structurally strong framework for the windwheel sails provides a rotor that is sufficiently rigid, relatively cheap (especially if the wheel and axle are cannibalised from an abandoned bicycle) and readily available throughout the world. Sail manufacture, assembly and maintenance for a Cretan windwheel can usually be undertaken locally, so eliminating the high costs of importing commercially available wind energy conversion systems. Thus, Cretan-type windwheels are likely to be increasingly used in less developed countries despite their intrinsically poor capabilities for harnessing wind power.Test data for a shrouded version of the ‘cycle wheel’, Cretan system are presented. The use of nine loosely sheeted sails produced a maximum power output of 14 W for an air speed at entry to the rotor of 5 m s^?1, corresponding to a free stream wind of less than 3·5 m s^?1. For this system it was found that tight (rather than loose) sails harnessed relatively little power. The presence of the shroud, which reduced tip losses, led to higher power coefficients being attainable.Two possible applications for a larger version (than tested) shrouded, Cretan type windwheel are described, namely (i) for irrigation and land drainage in undeveloped countries and (ii) for stimulating a peristaltic pump which acts as a gravitational boost to drive solar-heated anti-freeze liquid around a low height, domestic central-heating circuit.     

Working together: Understanding the effects of small hydropower

There is very little real data on the ecological effects of run of river mini hydro schemes. This has led to the problem for hydro developers, where regulators have to take a precautionary view of any new proposed development, particularly on the more ecologically interesting rivers; unfortunately these are often the most potentially viable hydro sites. In this edition of Consultants' Corner, Ian Draisey, Dulas Ltd describes experiences in the development of small hydro schemes and how the company is working together with regulators to better understand the effects of such schemes on river ecology.     

Optimal installation of small hydropower plant—A review

Most of the countries have access to large amounts of water through rivers and canal. With this renewable resource, electricity can be generated without polluting the environment. Because of the increasing in electricity demand, it is important to estimate the future potential of hydropower. It would then be possible to plan development through mix of energy and implement measures to control the development of the electricity market by the use of sustainable small hydropower projects.In the present paper attempt has been made to review the different types of model developed to evaluate the cost of the small hydropower projects. A review on the different types of correlations developed by earlier investigators has also been presented. The present review attempts to cover the benefits such as clean development mechanism (CDM), internal rate of return (IRR) for financial viability of such projects. A review on the different types of optimization techniques is also been presented to minimize the cost of the installation of SHP projects.     

Modelling and performance analysis of an electric heater

Electric heaters are used extensively in many industrial applications. There are several interacting parameters that affect heater performance and contribute to its cost. Such parameters are: coil length, coil diameter, helix diameter, coil pitch, number of turns, coil emissivity, heater wall emissivity, applied voltage, air flow rate, air temperature at the heater outlet, insulation thickness, and the heater dimensions. Three conical heater configurations were selected for preliminary optimization. A conical heater configuration with outer ring coils was found to give the highest heater efficiency, the easiest and least expensive to manufacture, and was selected for detailed modelling. In the simulation model, the heater wall was divided into four annular sections and the continuous heater coil was divided into four segments of four ring coils. Energy and heat transfer equations were written for each ring coil, each section of the wall, and the air past each ring coil. Equations for coil resistance and power, air properties, heater geometry, and configuration factors are added to form a system of 220 nonlinear equations. Engineering equation solver (EES) was used to solve the system of equations. The results were checked by comparing the heater efficiency based on the average inlet and outlet air temperatures, and the heater efficiency based on the heater losses. Both efficiencies matched well in all calculations. The effects of varying the identified heater parameters on the heater performance were studied and discussed. The results indicate that increasing the coil length and airflow rate, while reducing coil emissivity, wall emissivity, and wire diameter could improve heater performance. Copyright © 2004 John Wiley & Sons, Ltd.     

Design and performance evaluation of an innovative small scale combined cycle cogeneration system

This paper deals with an innovative natural gas (NG) combined cycle cogeneration system (150-kW_e, 192 kW_t). The system is made up of a combination of two interconnected combined heat and power (CHP) systems: a reciprocating internal combustion engine cogenerator (ICE CHP) as the topping cycle and a Rankine cycle cogenerator (RC CHP) which operates as the bottoming cycle on the exhaust gases from the ICE. The expander technology chosen for the Rankine cycle prime mover is a reciprocating single expansion steam engine with three cylinders in a radial architecture. The ICE is an automotive derived internal combustion engine with a high part-load electrical efficiency, due to a variable speed operation strategy and reduced emissions.     

小型水电站的设备防雷设计

小型水电站大多地处山区,厂内控制设备遭遇雷击的情况时有发生,特别是采用了计算机控制设备以后,设备耐雷击水平大大降低,但如果在低压母线上布设避雷器,在电源接口加装浪涌电流吸收装置,并采用合理的接地方式,则会在很大程度上缓解雷电波对控制设备的破坏,保证电站设备的正常稳定运行。     

Modelling of a domestic wind power system including storage

A simulation analysis is presented of domestic heating by a wind power system including storage at a location 54°39′ N, 6°13′ W (Aldergrove, Northern Ireland). A simple theoretical model is constructed comprising a house of specified dimensions and heat loss characteristics, an aerogenerator and a thermal store. the data base used is a magnetic tape of hourly wind speed and air temperature readings taken at Aldergrove meteorological station during 1949–75. the results suggest a measure of optimization between store capacity and generator rating based on technical considerations alone, and a simple economic optimization is also presented.