Evaluation of solar aided thermal power generation with various power plants

Solar aided power generation (SAPG) is an efficient way to make use of low or medium temperature solar heat for power generation purposes. The so‐called SAPG is actually ‘piggy back’ solar energy on the conventional fuel fired power plant. Therefore, its solar‐to‐electricity efficiency depends on the power plant it is associated with. In the paper, the developed SAPG model has been used to study the energy and economic benefits of the SAPG with 200 and 300 MW typical, 600 MW subcritical, 600 MW supercritical, and 600 and 1000 MW ultra‐supercritical fuel power units separately. The solar heat in the temperature range from 260 to 90°C is integrated with above‐mentioned power units to replace the extraction steam (to preheat the feedwater) in power boosting and fuel‐saving operating modes. The results indicate that the benefits of SAPG are different for different steam extracted positions and different power plants. Generally, the larger the power plant, the higher the solar benefit if the same level solar is integrated. Copyright © 2010 John Wiley & Sons, Ltd.     

Solar aided power generation of a 300 MW lignite fired power plant combined with line-focus parabolic trough collectors field

Nowadays, conventional coal or gas fired power plants are the dominant way to generate electricity in the world. In recent years there is a growth in the field of renewable energy sources in order to avoid the threat of climate change from fossil fuel combustion. Solar energy, as an environmental friendly energy source, may be the answer to the reduction of global CO₂ emissions. This paper presents the concept of Solar Aided Power Generation (SAPG), a combination of renewable and conventional energy sources technologies. The operation of the 300 MW lignite fired power plant of Ptolemais integrated with a solar field of parabolic trough collectors was simulated using TRNSYS software in both power boosting and fuel saving modes. The power plant performance, power output variation, fuel consumption and CO₂ emissions were calculated. Furthermore, an economic analysis was carried out for both power boosting and fuel saving modes of operation and optimum solar contribution was estimated.     

Optimization study of integration strategies in solar aided coal-fired power generation system

Parabolic trough solar-aided coal-fired power generation system has been developed to achieve efficient use of solar energy resources by coupling conventional coal-fired power plant with solar energy. However, there are no appropriate evaluation criteria about the thermal and economic performance of the system presently. This paper proposes the evaluation standard of the solar aided coal-fired power plant, and then based on this standard an optimization of this system is applied by the genetic algorithm model. According to the optimization research of this system, a series of parameters such as the solar collector area; the way of the coupling the power plant; whether storage is needed and the relevant storage capacity are obtained.     

太阳能辅助燃煤热发电系统的探讨

由于太阳能供给的间歇性,单独投资建造的太阳能热发电系统经常会出现设备成本高、利用率低、收益低等问题。因此,利用太阳能热发电系统与常规燃煤发电系统都有汽轮机部分这一特点,将槽式抛物太阳能集热器集成到常规燃煤发电系统中,寻求改造现有燃煤发电系统的新途径。以某300 MW机组为例,利用弗留格尔公式进行变工况计算,然后进行热经济性分析,为太阳能辅助燃煤热发电混合系统的建立提供理论参考。     

利用计算机模拟太阳能光伏发电

太阳能光伏发电是利用太阳能电池这种半导体电子器件有效地吸收太阳光辐射能,并使之转换成电能的直接发电方式。开发利用太阳能这种可再生的清洁能源发电是解决能源短缺、保护环境的重要途径。本文概述了太阳能光伏发电技术的研究情况,根据传热学及相关知识建立数学模型,并运用Lab VIEW软件对该系统进行动态模拟与仿真。     

Effectiveness analysis of solar replacement scenarios in a typical solar–coal hybrid system

Since the 1990s, solar energy has been hybridized with fossil power plants to improve reliability and efficiency. Hence, this study proposed a methodology to thermodynamically model the solar–coal hybrid system. A conventional 200 MW coal-fired power plant was hybridized with solar heat at approximately 300°C and compared with the Solar Energy Generating Systems VI type. The annual thermal performances of the proposed system were assessed using the established thermodynamic methodology. The appropriate replacement configurations for the system can be determined to enhance solar-to-electricity efficiency. Therefore, this system may utilize solar energy on the utility scale effectively.     

不同容量和地区下光煤混合发电变工况性能研究

在构建系统集成模型的基础上,阐述光煤混合发电系统变工况性能计算方法。以3个地区和4种容量燃煤机组为例,研究集成模型、取代份额、辐射强度、地区和容量对光煤混合发电系统性能的影响规律。结果表明:机组容量和地区一定的情况下,全部取代1级抽汽且辐射强度最大时的系统节能效果最优;同机组不同地区开展混合发电时,太阳能资源丰富地的集热场面积最小,集热场换热效率和太阳能热电转换效率最大,年累计节能减排量大,静态投资回收期最短;同地区不同容量机组开展混合发电时,大容量机组年平均太阳能热电转换效率和年累计节能减排量最大,静态投资回收期最短。     

The performance analysis and evaluation of C‐PV/T aided power generation system

In this paper, a novel solar aided power generation (SAPG) hybrid system based on the structural characteristics of coal‐fired power generation is established. In this system, the extraction steam of No.8 low pressure heater is replaced by the hot water coming from a concentration‐photovoltaic/thermal (C‐PV/T) module. The extraction steam returns into the steam turbine to do work, which increases the output power. And the electricity from the parallel C‐PV/T module goes directly into the power grid, which increases the generated power. The C‐PV/T module coupled with coal‐fired power generation improves the solar energy efficiency and provides hot water. As a case study, the economic calculation is performed with actual operation data extracted from a 600‐MW coal‐fired unit. The results show that the total efficiency increased by 1.3%, the coal fuel consumption is lowered by 11 g/kW·h, and the investment recovery period is approximately 7 years. This study offers a theoretical support to the engineering demonstration.     

太阳能烟囱与垂直轴风机耦合发电可行性分析

通过分析太阳能烟囱热气流发电和垂直轴风力机发电的技术及特点,提出了太阳能热气流烟囱与垂直轴风力机耦合发电的方法。对风力机—太阳能热气流烟囱互补发电系统的可行性进行了分析。互补发电的功率输出持续、稳定,具有大规模并网的良好条件,是实现太阳能与风能综合利用的有效途径。     

Performance assessment of concentrated solar power plants based on carbon and hydrogen fuel cells

In spite of the recent success on the implementation of Concentrating Solar Power (CSP), still this technology needs a substantial enhancement to achieve competitiveness. This paper provides thorough insight after previous analyses on an alternative concept for higher efficiency CSP systems based on the replacement of the power block by an electrochemical conversion system. Concentrating solar energy is herewith used to decompose methane into hydrogen and carbon, which are used in hydrogen and carbon fuel cells for electricity generation. This approach envisages modular, efficient and flexible generation plants. Dispatchability can be achieved by storing the solid carbon. Solar-to-electricity efficiency was calculated assuming thermodynamic equilibrium composition and experimental data available from literature, and compared with those of conventional power generation systems and commercial CSP plants. It is concluded that this new-generation CSP concept is potentially able to produce power more efficiently than the current state-of-the art solar thermal power plants.     

Assessment of solar electricity potentials in North Africa based on satellite data and a geographic information system

Solar thermal power plants will provide a major share of the renewable energy sources needed in the future. STEPS, an evaluation system for solar thermal power stations, was designed to calculate the performance of such power stations as a function of direct solar radiation, geographical conditions (land slope, land cover, distance from cooling water resources, etc.), infrastructure (pipelines, electricity grids, streets etc.) and the configuration and performance of a selected solar thermal power plant concept. A cloud index derived from METEOSAT satellite images is used to calculate the direct solar radiation resource. A geographic information system (GIS) is used to process all the parameters for site assessment. In order to demonstrate the concept, an analysis of Northern Africa was performed with STEPS providing a ranking of sites with respect to the potential and cost of solar thermal electricity for a particular power plant configuration. Results were obtained with high spatial and temporal resolution.     

A distributed energy system integrating SOFC-MGT with mid-and-low temperature solar thermochemical hydrogen fuel production

Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation.     

Performance and cost assessment of Integrated Solar Combined Cycle Systems (ISCCSs) using CO2 as heat transfer fluid

In this paper, a performance and cost assessment of Integrated Solar Combined Cycle Systems (ISCCSs) based on parabolic troughs using CO₂ as heat transfer fluid is reported on. The use of CO₂ instead of the more conventional thermal oil as heat transfer fluid allows an increase in the temperature of the heat transfer fluid and thus in solar energy conversion efficiency. In particular, the ISCCS plant considered here was developed on the basis of a triple-pressure, reheated combined cycle power plant rated about 250 MW. Two different solutions for the solar steam generator are considered and compared.The results of the performance assessment show that the solar energy conversion efficiency ranges from 23% to 25% for a CO₂ maximum temperature of 550 °C. For a CO₂ temperature of 450 °C, solar efficiency decreases by about 1.5–2.0% points. The use of a solar steam generator including only the evaporation section instead of the preheating, evaporation and superheating sections allows the achievement of slightly better conversion efficiencies. However, the adoption of this solution leads to a maximum value of the solar share of around 10% on the ISCCS power output. The solar conversion efficiencies of the ISCCS systems considered here are slightly greater than those of the more conventional Concentrating Solar Power (CSP) systems based on steam cycles (20–23%) and are very similar to the predicted conversion efficiencies of the more advanced direct steam generation solar plants (22–27%).The results of a preliminary cost analysis show that due to the installation of the solar field, the electrical energy production cost for ISCCS power plants increases in comparison to the natural gas combined cycle (NGCC). In particular, the specific cost of electrical energy produced from solar energy is much greater (about two-fold) than that of electrical energy produced from natural gas.     

太阳能热发电厂厂用电率计算方法分析

文章主要解决了太阳能热发电设计领域的厂用电计算思路及方法的问题。太阳能热发电已成为我国新能源发电的重要发展方向,太阳能热发电厂用电率的计算目前还没有相关的规程规范。在研究过程中,采用对太阳能热发电厂的运行模式与火力发电厂运行模式进行对比分析的方法,得出火力发电厂厂用电率的计算方法不适用于太阳能热发电厂的研究结果。通过对槽式太阳能热发电厂集热场系统、吸热传热系统、储热系统、常规岛系统分别进行分析,提出了槽式太阳能热发电厂厂用电量的计算方法,得出了太阳能热发电厂应采用长序列代表年辐照值,逐时计算代表年的发电量和厂用电量,以其比值来计算厂用电率的结论;提出了槽式太阳能热发电厂厂用电率的计算思路和方法,可供塔式太阳能热发电厂参考,对我国太阳能热发电厂的设计发展起到推动作用。     

A novel hybrid oxy-fuel power cycle utilizing solar thermal energy

An advanced oxy-fuel hybrid power system (AHPS) is proposed in this paper. Solar thermal energy is used in the AHPS to produce saturated steam as the working fluid, and natural gas is internally combusted with pure oxygen. It is in configuration close to the zero emission Graz cycle. The thermodynamic characteristics at design conditions of the AHPS are analyzed using the advanced process simulator Aspen Plus. The corresponding exergy loss analyses are also carried out to gain understanding of the loss distribution. The results are given in detail. The solar thermal hybrid H₂O turbine power generation system (STHS) is evaluated in this study as the reference. The comparison results demonstrate that the proposed cycle has notable advantages in thermodynamic performances. For example, the net fuel-to-electricity efficiency of the AHPS is 95.90%, which is 21.61 percentage points higher than that of the STHS. The exergy efficiency (based on the exergy input of fuel and solar thermal energy without radiation) of the AHPS is 55.88%, which is 2.13 percentage points higher than that of the STHS.     

Integration of a solar thermal system in a dairy process

Any analysis of the current energy world scenario draws on the combination of energy efficiency improvement and the use of renewable-type energies. The industrial use of renewable energies is not still well established as they present several problems that generate insecurity in this sector. Some of the renewable energy resources work intermittently (like the sun or wind) and the energy they provide is, often, of low intensity. Solar thermal technology has been successfully introduced in domestic applications and buildings. Many industrial processes work in temperature intervals where solar thermal technology would be able to supply an important amount of the total energy input at an acceptable price. Based on mathematical modeling, this work evaluates the viability of integrating a solar thermal system to the conventional energy structure of a dairy plant in the Atlantic side of Spain. Pinch methodology has been used to develop the integration of the solar subsystem in the energy installation of the plant. In order to determine the potential of the solar thermal energy, several hypotheses and scenarios were analyzed, based on real cases of the productive process. As a result, it could be stated that the solar thermal energy potential for the studied industrial process, operating at low and middle temperatures, was considerable, and must be taken into account as an energy option.     

Energy performance enhancement of solar thermal power plants by solar parabolic trough collectors and evacuated tube collectors-based preheating units

Solar steam power plant is the dominant technology in the category of solar thermal power systems. In steam power cycles, there is usually a couple of steam lines, extracted from medium-pressure and low-pressure turbines, to preheat the working fluid before the boiler. This although leads to an increase in the energy efficiency of the cycle, reduces the contribution of the turbine proportionally. Therefore, finding an alternative method of preheating the working fluid would be effective in further enhancement of the efficiency of the system. In this study, the feasibility of using solar collectors for the preheating process in a solar steam power plant is investigated. For this, parabolic trough solar collectors and evacuated tube solar collectors based on a wide range of different scenarios and configurations are employed. The plant is designed, sized and thermodynamically analyzed for a case study in Saudi Arabia where there is a large solar irradiation potential over the year. The results of the simulations show that, among all the considered scenarios, a power cycle aided by a set of parabolic trough collectors as the preheating unit is the best choice technically. This configuration leads to about 23% increased power generation rate and 6.5% efficiency enhancement compared to the conventional design of the plant.     

New and emerging developments in solar energy

Solar energy can potentially play a very important role in providing most of the heating, cooling and electricity needs of the world. With the emergence of solar photocatalytic detoxification technology, solar energy also has the potential to solve our environmental problems. However, we do not see widespread commercial use of solar energy. Some of the emerging developments in solar may change that situation. This paper describes some of the new and emerging developments, with special emphasis on: (1) nanoscale antennas for direct conversion of sunlight to electricity with potential conversion efficiencies approaching 80–90%; (2) new thermodynamic cycles for solar thermal power, that have the potential to reduce capital costs by 50%; and (3) solar photocatalytic oxidation for cleanup of industrial wastewater, drinking water, soil and air. The paper describes the fundamentals of each of these developments, their potential, present status and future opportunities for research.(1) Nanoscale antenna solar energy conversion: The current photovoltaic technologies rely on the quantum nature of light and semiconductors which are fundamentally limited by the band-gap energies. A revolutionary new approach suggested by Professor Robert Bailey in 1972 revolves around the wave nature of light. Professor Bailey suggested that broadband rectifying antennas could be used for solar to d.c. conversion. These rectennas would not have the fundamental limitation of semiconductor band-gap limiting their conversion efficiencies. Rectennas for solar conversion would have dimensions of the order of the wavelengths of solar radiation which falls mostly in the sub-micron range. The challenges in actually achieving the objectives are many. This paper describes the challenges and approaches to their solution.(2) New thermodynamic cycles for solar thermal power: It is recognized that the capital costs of solar thermal power will have to be reduced by about 50% in the near future in order to make it competitive with fossil fuels (especially natural gas) based power systems. Potential exists for meeting this goal by reducing the costs and improving the thermodynamic performance of power cycles by hybridization and combined cycle approaches and by employing new and innovative ideas in thermal power cycles. This paper describes the new thermodynamic approaches with an emphasis on an innovative new thermodynamic cycle using ammonia and water mixtures as the working fluids.(3) Solar photocatalytic detoxification and disinfection of water and air: Although the potential of solar radiation for disinfection and environmental mitigation has been known for years, only recently has this technology been scientifically recognized and researched. Solar photocatalytic oxidation has been demonstrated to effectively treat groundwater, drinking water, and industrial wastewater. In some applications such as decoloration and reduction of COD it may be the only effective method of treatment. Treatment of indoor air by the photocatalytic method has been demonstrated as the most effective technology for that application. This paper describes the recent developments and identify challenges and future research opportunities.     

Photovoltaics and hydrogen: Future energy options

Solar power is destined to make a significant contribution to world energy supply for reasons of both the finite amount of fossil fuels and environmental damage consciousness. It is emphasized that the global environmental damage caused thermodynamically is more alarming to life on Earth than the risk of exhausting the finite amount of fossil fuels being consumed at the present rate. Solar power plants can be designed and constructed to convert solar radiation into some concentrated form of useful energy first and then into electricity or directly into electricity. The latter kind is comprised of photovoltaic cells. This paper discusses some of the solar energy options and also presents a historical overview, explains the rudimentary physical principles of the technology, the photovoltaic effect, the process to generate electricity in silicon solar cells, thin-film devices and high efficiency cells, and finally, the state-of-the-art of the latest developments in solar cell technology. Finally, the storing of solar energy, collected by a photovoltaic system, is recommended in the form of hydrogen as a future energy option.     

Analysis and characterization of wind-solar-constant torque spring hybridized model

Solar and wind are the most promising renewable energy resources. But their unpredictable and varying nature prevents them from being used as the sole resource for power generation. This paper presents a model of wind and solar thermal hybrid power plant with a spring storage system which is expected to play an efficient role in combating with the drawbacks related to renewable power generation. In the proposed scheme, wind energy is harnessed by a hybrid vertical axis wind turbine, solar energy is utilized by a Stirling engine, and the surplus energy is stored in a winding spring. The paper discusses the working methodologies and analyses the performance of such 2.6 kW hybrid power plant model. It has been observed that the plant is capable of consistently generating 50% of its rated capacity irrespective of limitations in solar and wind resources.