Economics of Ocean Thermal Energy Conversion (OTEC)

Ocean thermal energy conversion (OTEC) has for many years been recognised as a possible energy of the future. Recently, the emphasis has changed towards combination plants offering not only power, but also freshwater, mariculture and other deep ocean water applications (DOWA).The models used in this modified cost-benefit analysis indicate under what economic circumtances OTEC, which is presently only competitive in a few remote islands, may become more widely competitive in the near future. Among the model variables are the plants' capital cost, operation and maintenance costs, the price of oil and desalinated water as well as a hypothetical carbon tax.     

Using the condenser effluent from a nuclear power plant for Ocean Thermal Energy Conversion (OTEC)

There has been increasing interest in clean energy over past few years. Ocean Thermal Energy Conversion (OTEC) power plants have been examined as a viable option for supplying clean energy. This paper evaluated the thermodynamic performance of the OTEC power system. Computer simulation programs were developed under the same conditions but with various working fluids for a closed system, a regeneration system, an open system, a Kalina system, and a hybrid system. The results showed that the regeneration system using R125 showed a 0.17 to 1.56% increase in system efficiency. Moreover, the system can generate electricity when the difference in temperature between the warm and cold seawater inlet temperatures is greater than 15 °C. In addition, the system efficiency of OTEC power plants using the condenser effluent from a nuclear power plant instead of surface water was increased by approximately 2%.     

Thermal power plant efficiency enhancement with Ocean Thermal Energy Conversion

In addition to greenhouse gas emissions, coastal thermal power plants would gain further opposition due to their heat rejection distressing the local ecosystem. Therefore, these plants need to enhance their thermal efficiency while reducing their environmental offense. In this study, a hybrid plant based on the principle of Ocean Thermal Energy Conversion was coupled to a 740 MW coal-fired power plant project located at latitude 28°S where the surface to deepwater temperature difference would not suffice for regular OTEC plants. This paper presents the thermodynamical model to assess the overall efficiency gained by adopting an ammonia Rankine cycle plus a desalinating unit, heated by the power plant condenser discharge and refrigerated by cold deep seawater. The simulation allowed us to optimize a system that would finally enhance the plant power output by 25–37 MW, depending on the season, without added emissions while reducing dramatically the water temperature at discharge and also desalinating up to 5.8 million tons per year. The supplemental equipment was sized and the specific emissions reduction was estimated. We believe that this approach would improve the acceptability of thermal and nuclear power plant projects regardless of the plant location.     

Technical and economic feasibility of Ocean Thermal Energy Conversion

Ocean Thermal Energy Conversion (OTEC) plants will employ the temperature difference (ΔT) between the solar-heated surface layer of a tropical ocean (24–29.5°C) and the water at 500–1200 m depth (7-3.5°C) as the source and sink for a Rankine cycle system to generate electric power. An annual average ΔT near 24°C is available to grazing tropical OTEC plants. The resource is tremendous in terms of suitable ocean siting areas and is available 24 hr per day. It could supply a significant fraction of the world's energy needs in the year 2000. The first commercial plants could be deployed in the mid 1980s, and we believe they will be competitive then with fossil fuel and nuclear energy sources for selected applications. Ammonia (for fertilizers) is a particularly attractive product, because 95 per cent of the ammonia produced in the U.S. is now made from natural gas, our scarcest resource. Direct delivery of electric power to shore may also be competitive for, e.g. the southeastern United States. In the late 1980s or early 1990s, ammonia produced by grazing tropical OTEC plants could also be used as a hydrogen carrier for production of electricity by fuel cells anywhere in the world, and production of other chemicals and metals (aluminum, magnesium) should become attractive. Various OTEC plant-ship concepts, their economics, onboard production plants and some of the environmental considerations are discussed.     

海洋温差发电系统热力学及热经济性分析

以热力学基本原理为基础,建立了海洋温差发电系统仿真模型,对比分析了亚临界状态下R717、R134a和R600三种工质系统在约束蒸发器窄点温差条件下优化目标函数随蒸发温度的变化规律。结果表明:蒸发温度越高,不同系统换热器的热负荷以及冷、热海水泵功率越小,最佳蒸发压力和工质泵功率越大;不同系统的热效率和单位换热面积输出电量与蒸发温度的相关性较大,随蒸发温度的增加近似线性递增。蒸发器的换热面积与循环工质种类的相关性较小,但冷凝器的换热面积与循环工质种类的相关性较大。R717循环更接近于卡诺循环,R717的系统热效率最大,热负荷及泵功率最小,且其热经济性目标函数值在合适的范围内,是海洋温差发电系统较为理想的循环工质。研究结果可为海洋温差发电系统的设计、试验及设备选型提供理论参考。     

海洋温差能发电热力循环技术进展

受传统化石能源日趋枯竭和环境污染的影响,海洋能作为一种清洁可再生能源得到了广泛关注。海洋温差能作为海洋能的重要组成部分,其储量和可转化电能巨大,且发电波动小、能量密度高,积极开发海洋温差能资源对实现科技兴海战略具有重要意义。海洋温差热力循环是海洋温差能开发利用的关键技术,其循环效率的高低直接决定了海洋温差发电系统的技术和经济性。本文综述了海洋温差能发电热力循环技术研究现状,对其基本原理及形式、热力循环构架、循环工质和热力学分析方法进行了详细阐述,并对海洋温差能发电热力循环技术进行了深入分析和展望。     

Ocean thermal energy conversion (OTEC): Social and environmental issues

OTEC converts the solar energy, collected and stored in tropical waters, into electricity. The electricity may be either cabled to shore or used in situ for the manufacture of energyintensive products. Two countries, U.S.A. and Japan, are seriously pursuing OTEC. The development programs in both countries are similar. Presently, the emphasis is on the closed Rankine cycle with ammonia as the working fluid. The power plants are to be housed on floating platforms. If the electricity is to be cabled to shore, the platforms will be moored to the ocean floor. If the plants are to produce chemical products, they will graze from one location to another on the open sea to capture the largest available thermal resource.Technical feasibility of OTEC appears certain. In the near term, OTEC can be economical for U.S. islands, which depend on imported oil for power generation. OTEC can enter the U.S. mainland market in the Southeast if projected capital cost for large plants is realized and high voltage, underwater d.c. transmission is developed beyond current state of the art. The islands market amounts to 8 GW and the U.S. market is estimated to be much larger. Penetration of the island market can begin in the early 1990s and of the mainland market after the year 2000.A potential impediment to OTEC's accelerated deployment is capital. Although there are numerous important environmental and institutional questions, they are secondary to the economic and cost issues.This paper addresses the economic, social and environmental issues pertinent to the commercialization of OTEC. The a priori assumptions are that technical problems can be solved and that in certain locations. OTEC can be competitive with conventional base-load power systems.     

国内太阳能热利用现状与发展

介绍了国内太阳能热利用技术在各个领域的应用现状,重点介绍了太阳能集热器,太阳房,太阳能干燥,太阳能制冷等技术的发展,同时介绍了相关研究单位的示范项目与实例。     

Modeling and Energy Efficiency Analysis of Thermal Power Plant with High Temperature Thermal Energy Storage (HTTES)

This paper presents the recent research on the study of the strategies for the flexible operation of the thermal power plant to meet the requirement of load balance. The study aimed to investigate the feasibility of bringing the High Temperature Thermal Energy Storage(HTTES) to the thermal power plant steam-water cycle, to identify the suitable HTTES in the cold(hot) section of the reheating pipeline and to test the efficiency of the HTTES integration to increase the flexibility of peak shaving ...     

Thermal Energy Storage Performance of Fatty Acids as a Phase Change Material

Thermal energy storage performance of fatty acids and a eutectic mixture as phase change materials (PCMs) has been investigated experimentally. The selected PCMs for this study were palmitic acid, myristic acid, stearic acid, and a mixture of stearic and myristic acids in eutectic combination ratio of 65.7 wt% myristic acid and 34.3 wt% stearic acid. The PCMs have a melting temperature range of 50.0°C to 61.20°C and a latent heat range of 162.0 J/g to 204.5 J/g. The inlet temperature and the mass flow rate of heat transfer fluid (HTF) were selected as experimental parameters to test the thermal energy storage performance of the PCMs. The transition times, temperature range, propagation of the solid-liquid interface, as well as heat flow rate characteristics of the employed cylindrical tube storage system were studied at varied experimental parameters. The experimental results show that the melting front moves to inward in the radial directions as well as in the axial directions from the top toward to the bottom of the PCM tube. It was observed that the convection heat transfer in the liquid phase plays an important role in the melting process. The changes in the studied HTF parameters have more effect on the melting processes than the solidification processes of the PCMs. The average heat storage efficiency calculated from data for all the PCMs is 51.5%, meaning that 48.5% of the heat actually was lost somewhere.     

An analysis of the potential of Wind Energy Conversion Systems

Wind Energy Conversion Systems (WECS) are solar systems because the sun drives the atmospheric circulation. About 20 TW of wind energy flows poleward annually, over land in temperate latitudes, in the 500 m deep atmospheric boundary layer. An average 500 GW of electricity could be generated by massive exploitation of the U.S. Great Plains wind field.There are, however, large fluctuations in available wind power. There are frequent 20% variations in annual supply; annual periodicity brings most wind power during the spring; there are storm cycles; and there is a diurnal cycle. Gusts and turbulence also require filtering to meet normal power requirements. Several schemes are evolving to tame this erratic wind power supply.Modern technology is refining horizontal-axis turbines of a wide size range. Progress is also being made toward producing an economical vertical-axis turbine. Standards for turbine performance evaluation and installation site selection are now being developed. Yet it will be a few years before proven systems can significantly affect national energy supplies.Eventually, mass-produced WECS may cost $1000 per installed, rated kW, but the wind does not often flow at turbine-rated speed. With some storage or filtering, problems with wind variability may be overcome. Then WECS electricity production may be as economical as other electric generators. No serious hazards or environmental impacts should slow WECS development.     

Conversion of a commercial gasoline vehicle to run bi-fuel (hydrogen-gasoline)

Bi-fuel internal combustion engine vehicles allowing the operation with gasoline or diesel and hydrogen have great potential for speeding up the introduction of hydrogen in the transport sector. This would also contribute to alleviate the problem of urban air pollution. In this work, the modifications carried out to convert a Volkswagen Polo 1.4 into a bi-fuel (hydrogen-gasoline) car are described. Changes included the incorporation of a storage system based on compressed hydrogen, a machined intake manifold with a low-pressure accumulator where the hydrogen injectors were assembled, a new electronic control unit managing operation on hydrogen and an electrical junction box to control the change from a fuel to another. Change of fuel is very simple and does not require stopping the car. Road tests with hydrogen fuel gave a maximum speed of 125 km/h and an estimated consumption of 1 kg of hydrogen per 100 km at an average speed of 90 km/h. Vehicle conversion to bi-fuel operation is technically feasible and cheap.     

相变储热研究进展(2)组合相变材料储热与应用潜力

本文从两个方面总结了相变储热（ＬＴＥＳ）的研究现状：①ＬＴＥＳ在太空太阳能动力（ＤＢＰ）发电系统和建筑物围护结构中的应用;②组合相变材料储热系统的研究历程和最新进展。     

Thermal pretreatment of wood (Lauan) block by torrefaction and its influence on the properties of the biomass

The purpose of this study is to investigate the torrefaction behavior of woody biomass (Lauan) blocks and its influence on the properties of the wood. Three different torrefaction temperatures of 220, 250 and 280 °C, corresponding to light, mild and severe torrefactions, and four torrefaction times of 0.5, 1, 1.5 and 2 h were considered. After analyzing the torrefied woods, it was found that the torrefaction temperature of 280 °C was able to increase the calorific value of the wood up to 40%. However, over 50% of weight was lost from the wood. The grindability of the torrefied wood could be improved in a significant way if the torrefaction temperature was as high as 250 °C and the torrefaction time longer than 1 h. Therefore, the torrefaction temperature of 250 °C along with the torrefaction time longer than 1 h was the recommended operation to intensify the heating value and grindability as well as to avoid too much mass loss of the wood. This study also suggested that over 50% of the reacted wood was converted into condensed liquid. The main components in the liquid were monoaromatics; little amount of heterocyclic hydrocarbons were also obtained from the torrefactions, especially at the torrefaction temperature of 280 °C.     

锅炉脱盐水系统变频节能改造

在化工生产中,离心泵使用较为普遍,其出口压力往往要高于生产系统所需压力,常见做法是采用阀门降压,能耗较高.相比而言,变频调速能够降低离心泵出口压力过高问题,且能够节省阀门降压带来的能量损耗.针对兖矿国宏公司脱盐水系统,收集离心泵出口管道阀门前后压力数据,进行相关计算后得出节能效果.结合现场情况和运行经验,编制变频改造方案.改造完成后,再次收集相关数据,经过比较节能效果明显,达到预期目的.     

对水帆机研制原理的探讨

阐明了水帆机能量转化的具体过程和特点,并将伯努利方程应用于水帆机,推导出了基本公司Ｎ＝９．８１Ｑｈ,说明了水帆机仍然遵守这一能量转化的自然界基本规律。