Economic evaluation of the dual mode CAES solution for increased wind energy contribution in autonomous island networks

Wind parks operating in autonomous island grids, such as those encountered in the Aegean Archipelago, face considerable wind energy curtailments, owed to the inability of local electricity networks to absorb the entire wind energy production. On the other hand, plans promoting the natural gas-based electricity generation in big islands (such as Crete) question the future of wind energy. To recover wind energy curtailments and benefit from the introduction of natural gas, the adoption of compressed air energy storage (CAES) systems suggests an appreciable energy solution. Furthermore, to improve the economic performance of the proposed system, it is decided that guaranteed energy amounts should be delivered to the local grid during peak demand periods. In an effort to obtain favourable negotiation conditions – for the selling price of energy delivered – and also improve the economic performance of the system, a dual mode CAES operation is currently examined. Proceeding to the economic evaluation of dual mode CAES configurations that ensure maximum wind energy recovery, the feasibility of the proposed system may be validated. Lower electricity production costs and considerable reduction of fuel consumption achieved – in comparison with the requirements of conventional peak demand power units – illustrate the system's advantages.     

Prediction of some performance characteristics of shale oil in the gas turbine combustor

Measurements of radiation, smoke and temperature in a developed experimental combustor at various air pressures, inlet temperatures and air-fuel ratios have shown the effects of such fuel properties as volatility, boiling range and H percentage mass content on ignition, lean blow-out, liner temperature and exhaust smoke. This study has been extended to cover some of these performance characteristics for shale oil.     

Research and development for steam and gas turbines in low-carbon future

Abstract

Future energy requirements for the UK will need to be met with reduced CO₂ emissions. There is a requirement for 2050 CO₂ emissions to be at 20% of 1990 levels. To achieve this there will need to be considerable investment into the research and development, and construction of renewables technologies. Despite this emphasis on renewable power, fossil fuelled power generation technologies, and in particular turbines, will still have a major role to play in the future. However, the way in which the turbines will be used may change significantly. There will therefore need to be research and development investment for turbines at all levels of technology readiness. The arguments for future R&D investment for steam and gas turbines are reviewed and some directions the R&D may need to take examined.     

Feasibility assessment of Brassica carinata bioenergy systems in Southern Europe

A detailed reliability assessment was made of electricity generation systems in Spain that are based on Brassica carinata cultivation. The assessment considers the following chain of energy generation: biomass cultivation and harvesting, transportation and electricity generation in biomass power plants (10, 25 and 50 MW). Flue gas desulphurisation systems have been included for larger plants following the criteria of the Spanish legislative framework. Six scenarios were analysed in accordance with the following aspects: two crop distributions around the power plant and three power plant sizes. The results show that the cost of biomass delivered at the power plants ranges from 107.81 to 112.54 € Mg⁻¹ dry basis.Sensibility analysis shows that variation in biomass production in the field demonstrates that biomass cost delivered at the plant is notably affected and consequently so is the system's feasibility.Furthermore, the increase of the price of CO₂ emission credits, also considered in sensibility analysis, can help to improve the reliability of systems because of the increase of gross profit for each scenario.This study clears up the Economic uncertainty of B. carinata biomass energy systems based on the single use of this renewable energy resource. Higher crop productivities are needed to ensure an economic reliability of the analysed systems. On the other hand biomass mix can solve SO₂ emission cleaning cost for large power plants, improving the reliability of B. carinata application as fuel.     

Comparison of performance for cascaded humidified advanced turbine with the corresponding combined system

In this paper, the use of a cascaded humidified advanced turbine (CHAT) system instead of a cascaded advanced combined turbine (CACT) system to increase the overall efficiency is discussed. The overall performance is calculated for CHAT and CACT systems.

The working parameters in this study are the overall pressure ratio, ambient temperature, and altitude. Using a specially designed program, the effect of these parameters on the specific power output, specific fuel consumption, engine thermal efficiency, and the overall efficiency is evaluated and compared.

The results showed superior CHAT system performance relative to the CACT system. The specific power output, the specific fuel consumption, and the overall efficiency of the two systems at design point are compared as follows: the specific power output for CHAT system is about 5% more than CACT at design point, the specific fuel consumption for CHAT is about 7% less than CACT at design point, and the efficiency for CHAT system is about 7% more than CACT at design point. Thus the CHAT system demonstrates better performance at higher temperatures and part-load operation. It is interesting to notice that the effect of altitude on both systems is almost the same.     

电转氢技术融入分布式智慧能源的应用模式研讨

从电转氢技术融入智慧能源的应用趋势和方式入手,聚焦其与分布式智慧能源系统融合应用的模式和关键点,并结合应用场景对现有欧美实际案例进行梳理与分析研究。同时,研判电转氢技术应用潜力与阻碍。     

确定热电厂供热成本的热经济学方法

本文利用热经济学的基本理论方法,建立了确定热电厂供热成本的分析模型。编制了相应的计算机软件,并以石景山热厂２００ＭＷ供热机组为例,得到了该机组的主要技术经济指标。该方法具有客观准确、便于计算机处理等特点。     

Energy consumption in Kuwait: Prospects and future approaches

In Kuwait, the consumption of oil, the country's main source of energy, is increasing year by year. In addition to the harsh climate and the rapid economic and construction growth in the country, there are further aspects of energy inefficiency. While 10% of the produced energy was being consumed locally in 1980, this percentage increased to 20% in 2005 and is expected to reach 40% by 2015. If this situation continues, the country will be forced to increase production or reduce exportation. Both options will cause serious problems to the country in meeting future energy demands due to its dependence on oil as a source of income, shortages of other energy resources, and the environmental care of the country.     

Designing cost-effective seawater reverse osmosis system under optimal energy options

Today, three billion people around the world have no access to clean drinking water and about 1.76 billion people live in areas already facing a high degree of water stress. This paper analyzes the cost-effectiveness of a stand alone small-scale renewable energy-powered seawater reverse osmosis (SWRO) system for developing countries. In this paper, we have introduced a new methodology; an energy optimization model which simulates hourly power production from renewable energy sources. Applying the model using the wind and solar radiation conditions for Eritrea, East Africa, we have computed hourly water production for a two-stage SWRO system with a capacity of 35 m³/day. According to our results, specific energy consumption is about 2.33 kW h/m³, which is a lower value than that achieved in most of the previous designs. The use of a booster pump, energy recovery turbine and an appropriate membrane, allows the specific energy consumption to be decreased by about 70% compared to less efficient design without these features. The energy recovery turbine results in a reduction in the water cost of about 41%. Our results show that a wind-powered system is the least cost and a PV-powered system the most expensive, with finished water costs of about 0.50 and 1.00$/m³, respectively. By international standards, for example, in China, these values are considered economically feasible. Detailed simulations of the RO system design, energy options, and power, water, and life-cycle costs are presented.     

火电站锅炉运行可控性能量损失分析

在用反平衡方法对电站锅炉运行进行热效率计算的基础上,从火电站锅炉实际运行的可操作性出发,对电站锅炉进行热经济性分析,并对一些可控性强的影响因素作了能损分析与计算,有利于提高机组的经济运行水平。     

Cycle improvements to steam injected gas turbines

The efficiency and specific power of the steam injected gas turbine is analysed by modelling the thermodynamic cycle. In this model special attention is paid to the blade cooling. The basic cycle as well as cycles with improvements such as intercooling, heat recovery by regenerator and blade cooling using steam are studied. The different cycles are compared with the combined cycle and the intercooled regenerative cycle. The conclusion is that the steam injected cycles have high efficiency and specific power. Adding heat exchangers to the cycle is not beneficial. Using steam as coolant for the blades offers interesting perspectives. Copyright © 2000 John Wiley & Sons, Ltd.     

Modelling of aluminum-fuelled power plant with steam-hydrogen enthalpy utilization

Present paper is devoted to the modelling of aluminum-fuelled power plants which employ an aluminum-water reactor for hydrogen and heat production. We considered two new schemes for power plants with aluminum-water reactors producing high-temperature steam-hydrogen mixture: a power plant with a steam-hydrogen turbine, condenser and air-hydrogen fuel cell and a power plant with a steam-hydrogen turbine, combustion chamber and steam-gas turbine. Parameters of the aluminum-water reactor described in the paper correspond to those of the recently developed and tested aluminum-water reactor: pressure – 15 MPa, temperature – 600 K, steam to hydrogen mass ratio – 40. It was shown that the electrical efficiency can be increased from 12% to 25–30% for the power plant with an air-hydrogen fuel cell and to 18–25% for that with a combustion chamber and steam-gas turbine. The total efficiency of such power plants can reach 80%. Moreover, the efficiency of aluminum-fuelled power plants can be further increased by heat regeneration or heat transfer to the secondary circuit. The proposed calculation method provides high accuracy and can be used to predict the performance of power plants with aluminum-water reactors under different operation conditions. In general, the proposed method can be used to simulate utilization of the enthalpy of high-temperature steam-hydrogen mixture from various sources.     

Quantification and use of forest biomass residues in Maputo province, Mozambique

This article describes a study on the quantification and use of forest biomass residues in Maputo province, in Mozambique. The study was performed based on information from the thematic cartography of soils of Maputo province, provided by the National Direction of Forest and Land of Mozambique, and data for the forest growth rates available in the literature. It was estimated that the total production of forest biomass residues in Maputo province is 1,233,412 ton/year, with a corresponding energy potential of 17,267,771 GJ/year. As a way of making the forest biomass residues profitable, the present work proposes the use of part of the residues as fuel in new power plants to be build in Maputo province. In this part of the study aiming at implanting power plants in Maputo province, it was taken into account the risk of forest fires, number of existing consumers of forest residues, residues availability, protected forests, transport infrastructures and existence of national electric network. It was found that the districts of Magude and Moamba are those that have the best conditions to receive the new biomass power plants. Factors such as the cost of the technology and the degree of pre-treatment of the forest residues have been taken into consideration in choosing the combustion technology for the proposed power plants. In this context, the grate burning technology appears to be the most advantageous from costs/benefits viewpoint. The proposed power plants can produce about 236,520 MWh, which is equivalent to 32% of the energy consumed in Maputo province in 2004.     

Power quality assessment of wind turbines and comparison with conventional legal regulations: A case study in Turkey

Renewable energy sources have been investigated for use instead of conventional fossil fuels in many areas. Among these renewable energy sources, wind energy has come into prominence owing to the fact that it is a clean, sustainable and cost-effective type of energy. However, the connection of large wind farms to the grid may cause problems in terms of power quality due to the variability of the energy extracted from the wind. The mentioned power quality problems are generally taken into consideration after the grid integration of wind farms. However, the precautions that can be taken by means of the assessments before the installation of the turbines represent an easier and more economic way. In this study, the possible effects of the grid connected wind turbines on the power quality characteristics have been defined and the MATLAB based models have been constructed so as to calculate these effects. Particularly, fast voltage variations that are difficult to model due to their relations with the human factor have been analyzed in detail. It has been aimed that the models are suitable for use in practice while utilizing various standards such as IEC 61400-21 and IEC 61000-4-15 in order to setup the models. The analyses of the implementations that represent constraints for exploiting the wind resources in Turkey have been realized in terms of production and consumption with a case study. The realized calculations present the applicability of the model to grid conditions with different characteristics. It is also presented that the wind energy penetration can be increased without deteriorating the power quality of the grid with the use of the proposed model.     

Thermodynamic analysis of a pulse combustion system and its application to gas turbines

The study describes a special construction of a pulsating self-compressing combustion system, which gives nearly constant in- and outflows of gas, and its use in connection with gas turbine power stations. The main idea of the self-compressing combustion chamber is that the pressure at the outflow after combustion is higher than that at the inflow to the combustion chamber. The maximum thermodynamically possible pressure rise in the combustion chamber is solved and calculated for different temperature ratios and combustion processes. The thermodynamic advantage of pulse combustion for gas turbine systems is shown as a function of the self-compression pressure ratio.     

Barriers to improvements in energy efficiency

The growing recognition of the potential energy savings available through improvements in energy efficiency has sparked an increased interest in the actors involved in implementing these improvements and the barriers that they can encounter. This paper identifies these actors and creates a topology for the various barriers that hinder their efforts to achieve better energy efficiencies at the very lowest level of the energy consumer to the very highest level of the global financial agencies. The analysis concludes that four essential factors will help facilitate the dissemination of energy-efficiency improvements: relying on combinations of measures for overcoming each barrier to energy efficiency; using combinations of measures at the strategic level; employing policy-assisted, market-oriented mechanisms and promoting technological innovation as a means for achieving improved energy efficiency.     

Assessment of flicker limits compliance for wind energy conversion system in the frequency domain

Fixed-speed wind turbines produce voltage flicker during switching operations and they also produce flicker during continuous operation. In order to avoid power quality problems to consumers, it would be important to predict flicker emission from wind turbines at a certain site previously to installation. This paper focuses on a method to perform a fast flicker analysis caused by grid-connected fixed-speed wind turbines in continuous operation. The method has been developed completely in the frequency domain, including wind turbines. This method predicts the P_st value for each node system. Applying this method there would be no need to perform measurements in every node, which would be nearly impossible or to simulate the whole model in the time domain, demanding an enormous computational effort and storage capacity. The performance of the frequency domain method is applied to analyze different wind energy generation scenarios to assess their influence in a real power system.     

Basic chemically recuperated gas turbines—power plant optimization and thermodynamics second law analysis

One of the proposals to increase the performance of the gas turbines is to improve chemical recuperated cycle. In this cycle, the heat in the turbine exhaust gases is used to heat and modify the chemical characteristics of the fuel. One mixture of natural gas and steam receives heat from the exhaust turbine gases; the mixture components react among themselves producing hot synthesis gas. In this work, an analysis and nonlinear optimization of the cycle were made in order to investigate the temperature and pressure influence on the global cycle performance. The chemical composition in the reformer was assumed according to chemical equilibrium equations, which presents good agreement with data from literature. The mixture of hot gases was treated like ideal gases. The maximum net profit was achieved and a thermodynamic second law analysis was made in order to detect the greatest sources of irreversibility.     

Design improvements and performance testing of a biomass gasifier based electric power generation system

The objective of the research work, reported in this paper is, to design and develop a down draft gasifier based power generation system of 75 KW_e. A heat exchanger was designed and installed which recycles the waste heat of the hot gas, to improve the efficiency of the system. An improved ash removal system was introduced to minimize the charcoal removal rate from the reactor, to increase the gas production efficiency. A detailed analysis of the mass, energy and elemental balance is presented in the paper. The cold gas efficiency of the system is increased from 75.0% to 88.4%, due to the improvements made in the ash removal method. The Specific Fuel Consumption (SFC) rate of the system is 1.18 kg kWh⁻¹. The energy conversion efficiency of the system, from fuel wood to electric power was found to be 18%. Significant increase in calorific value of the producer gas was achieved by supplying hot air for gasification.     

Analysis of the benefits of carbon credits to hydrogen addition to midsize gas turbine feedstocks

The addition of hydrogen to the natural gas feedstocks of midsize (30–150 MW) gas turbines was analyzed as a method of reducing nitrogen oxides (_NOx)$({\mathrm{NO}}_x)$ and _CO2${\mathrm{CO}}_2$ emissions. In particular, the costs of hydrogen addition were evaluated against the combined costs for other current _NOx${\mathrm{NO}}_x$ and _CO2${\mathrm{CO}}_2$ emissions control technologies for both existing and new systems to determine its benefits and market feasibility. Markets for _NOx${\mathrm{NO}}_x$ emissions credits currently exist in California and the Northeast States and are expected to grow. Although regulations are not currently in place in the United States, several other countries have implemented carbon tax and carbon credit programs. The analysis thus assumes that the United States adopts future legislation similar to these programs. Therefore, potential sale of emissions credits for volunteer retrofits was also included in the study. It was found that hydrogen addition is a competitive alternative to traditional emissions abatement techniques under certain conditions. The existence of carbon credits shifts the system economics in favor of hydrogen addition.