Geothermal power production in future electricity markets—A scenario analysis for Germany

Development and diffusion of new renewable energy technologies play a central role in mitigating climate change. In this context, small-scale deep geothermal power has seen growing interest in recent years as an environmentally friendly, non-intermittent energy source with large technical potential. Following the first successful demonstration projects, the German geothermal industry is currently experiencing an internationally unparalleled growth. In this study we explore the factors driving this development, and the role geothermal power production could play in the future of the German electricity market. For this, we apply the scenario technique, based on literature analysis and interviews with companies operating actively in the field. Our findings highlight the importance of political support and framework conditions in the electricity market, with the best prospects in a decentralised energy system based on renewable energy sources, where high investment costs and the risk of discovery failure are balanced by the benefits of low-carbon base load power.     

Exploring the hypothetical limits to a nuclear and renewable electricity future

This article evaluates whether the world can transition to a future global electricity system powered entirely by nuclear power plants, wind turbines, solar panels, geothermal facilities, hydroelectric stations, and biomass generators by 2030. It begins by explaining the scenario method employed for predicting future electricity generation, drawn mostly from tools used by the International Energy Agency. The article projects that the world would need to build about 7744 Gigawatts (GW) of installed electricity capacity by 2030 to provide 37.2 thousand terawatt‐hours (TWh). Synthesizing data from the primary literature, the article argues that meeting such a projection with nuclear and renewable power stations will be difficult. If constructed using commercially available and state‐of‐the‐art nuclear and renewable power stations today, the capital cost would exceed $40 trillion, anticipated negative externalities would exceed $1 trillion per year, and immense strain would be placed on land, water, material, and human resources. Even if nuclear and renewable power technologies were much improved, trillions of dollars of investment would still be needed, millions of hectares of land set aside, quadrillions of gallons of water used, and material supplies of aluminum, concrete, silicon, and steel heavily utilized or exhausted. Because of these constraints, the only true path towards a more sustainable electricity system appears to be reducing demand for electricity and consuming less of it. Copyright © 2009 John Wiley & Sons, Ltd.     

Techno‐economic analysis of an integrated biorefinery system for poly‐generation of power,heat, pellet and bioethanol

Bioethanol is an alternative to fossil fuels in the transportation sector. The use of pellet for heating is also an efficient way to mitigate greenhouse gas emissions. This paper evaluates the techno‐economic performance of a biorefinery system in which an existing combined heat and power (CHP) plant is integrated with the production of bioethanol and pellet using straw as feedstock. A two‐stage acid hydrolysis process is used for bioethanol production, and two different drying technologies are applied to dry hydrolysis solid residues. A sensitivity analysis is performed on critical parameters such as the bioethanol selling price and feedstock price. The bioethanol production cost is also calculated for two cases with either 10 year or 15 year payback times. The results show that the second case is currently a more feasible economic configuration and reduces production costs by 36.4%–77.3% compared to other types of poly‐generation plants that are not integrated into existing CHP plants. Copyright © 2013 John Wiley & Sons, Ltd.     

An experimental study on multi‐purpose desiccant integrated vapor‐compression air‐conditioning system

In this paper, a multi‐purpose hybrid desiccant integrated vapor‐compression air‐conditioning system of a small capacity is experimentally investigated. The system, referred as hybrid desiccant‐assisted air conditioner (HDAC), is designed to meet the cooling load of spaces having large latent heat portions and at the same time to extract water from atmospheric air. The system is mainly consisted of a liquid‐desiccant dehumidification unit integrated with a vapor‐compression system (VCS). The dehumidification unit uses lithium chloride (LiCl) solution as the working material. The effect of different parameters, such as desiccant solution flow rate, process airflow rate, evaporator and condenser temperatures, strong solution concentration and regeneration temperature on the performance of the system, is studied. This system has a water recovery rate of 6.7 l/h TR (1.91 l/h kW) of pure water at typical north Egyptian climate (20–30°C dry bulb and 35–45% relative humidity). The HDAC system has a COP as high as 3.8 (an improvement of about 68% over the conventional VCS). The system offers a total cooling capacity of about 1.75 TR (6.15 kW) using a 0.75 TR (2.6 kW) VCS unit. Finally, the proposed system is found to have a payback time of about 10 months without any considerable extra capital cost compared with the known split air‐conditioning system. The results emphasize the potential benefits of the HDAC system. Copyright © 2010 John Wiley & Sons, Ltd.     

Thermal‐economic analysis of a transcritical Rankine power cycle with reheat enhancement for a low‐grade heat source

A thermal‐economic analysis of a transcritical Rankine power cycle with reheat enhancement using a low‐grade industrial waste heat is presented. Under the identical operating conditions, the reheat cycle is compared to the non‐reheat baseline cycle with respect to the specific net power output, the thermal efficiency, the heat exchanger area, and the total capital costs of the systems. Detailed parametric effects are investigated in order to maximize the cycle performance and minimize the system unit cost per net work output. The main results show that the value of the optimum reheat pressure maximizing the specific net work output is approximately equal to the one that causes the same expansion ratio across each stage turbine. Relative performance improvement by reheat process over the baseline is augmented with an increase of the high pressure but a decrease of the turbine inlet temperature. Enhancement for the specific net work output is more significant than that for the thermal efficiency under each condition, because total heat input is increased in the reheat cycle for the reheat process. The economic analysis reveals that the respective optimal high pressures minimizing the unit heat exchanger area and system cost are much lower than that maximizing the energy performance. The comparative analysis identifies the range of operating conditions when the proposed reheat cycle is more cost effective than the baseline. Copyright © 2012 John Wiley & Sons, Ltd.     

Low‐cost mounting arrangements for building‐integrated wind turbines

Micro‐generation is being widely promoted as a way for householders in the UK and elsewhere to take part in ‘the Green Revolution’. Building‐integrated wind turbines (BIWTs) provide a way to do this, enabling people to reduce their contribution to the problems of both climate change and decreasing fossil fuel availability. Although energy yields from BIWTs for many householders have been shown to be low, there are still situations where such turbines can make a useful contribution to electricity generation, e.g. in windier areas and for isolated detached buildings. The standards for the installation of BIWTs are still being developed including those for the safe mounting of turbines on domestic buildings. This paper investigates the current trend for mounting small wind turbines on the walls of domestic premises and compares this with an approach which uses roof timbers. It identifies the main characteristics of building construction which affect the integrity of such installations. European and British standards have been used to calculate wind and gravitational loads. Finite element models are used to derive working stresses and, hence, some basic principles of good design. The likely costs of wall and roof mounting are then compared. Installation and health and safety issues are also examined briefly. Copyright © 2010 John Wiley & Sons, Ltd.     

太阳能与燃煤机组集成发电系统的研究现状

介绍了太阳能与燃煤机组集成发电系统的发展背景、国内外发展状况以及集成方式,对太阳能与回热系统集成等三种集成方式进行了比较,分析了几种提高集成发电系统经济性的优化方式,指出了发展中存在的一些问题及发展前景。     

An Integrated Feasibility Analysis of a Stand‐alone Wind Power System,including No‐energy Fulfillment Cost

Autonomous wind power systems are among the most interesting and environmentally friendly technological solutions for the electrification of remote consumers. However, the expected system operational cost is quite high, especially if the no‐load rejection restriction is applied. This article describes an integrated feasibility analysis of a stand‐alone wind power system, considering, beyond the total long‐term operational cost of the system, the no‐energy fulfilment (or the alternative energy coverage) cost of the installation. Therefore the impact of desired system reliability on the stand‐alone system configuration is included. Accordingly, a detailed parametric investigation is carried out concerning the influence of the hourly no‐energy fulfilment cost on the system dimensions and operational cost. Thus, by using the proposed method, one has the capability–in all practical cases–to determine the optimum wind power system configuration that minimizes the long‐term total cost of the installation, considering also the influence of the local economy basic parameters. Copyright © 2003 John Wiley & Sons, Ltd.     

考虑供热系统热储能特性的电-热综合系统随机优化调度模型研究

热电联产机组、热泵等装置的应用促进了电-热综合系统间的耦合关系,为风电的消纳提供了新途径。文章考虑了供热系统热储能动态特性,采用多场景法模拟风电出力不确定性,搭建了电-热综合能源系统随机优化调度模型。首先,针对供热管道传输时延动态特性,研究分析了其储热能力;其次,以电-热综合能源系统购能费用最低为目标函数,以热网约束、电网约束为约束条件,提出了综合系统能量最优化调度方案;最后,在IEEE33节点和6节点热网上进行算例分析,验证了模型的有效性。     

Highly integrated post‐combustion carbon capture process in a coal‐fired power plant with solar repowering

While post‐combustion carbon capture (PCC) technology has been considered as the ready‐to‐retrofit carbon capture solution, the implementation of the technology remains hampered by high costs associated with the large energy penalty incurred by solvent regeneration. This paper presents a highly integrated PCC process for a coal‐fired power plant with solar repowering that features significantly enhanced energy efficiency. Validated process models are developed for the power, capture, and solar thermal plants and simulated in a model superstructure to evaluate the possible improvements in power plant energy efficiency and power output penalty reductions. A 660‐MW power plant is taken as the case study. Three cases are used in this simulation analysis: (a) base case consisting of 660‐MW power plant integrated with a PCC plant, (b) the base case extended to incorporate solar repowering, and (c) a highly integrated case that extends on the previous case to include CO₂ gas compression unit heat integration. This study also highlights and discusses the role and interaction of various PCC and solar plant variables (e.g., solar field size, steam extraction flow rate, and twin LP turbine pressures) in the integration with power plant parameters. In particular, the power plant deaerator conditions play an important role in determining the total solar thermal energy required from the solar plant, thus dictating the solar field size. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermodynamic analysis of representative power generation cycles for low‐to‐medium temperature applications

This study is focused on the analysis of representative thermodynamic cycles for power generation at low‐to‐medium temperatures (with the highest cycle temperature from 450 to 700 K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450–500 K among the 10 representative cycles, while regenerative Brayton cycle shows better behavior for 550–700 K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low‐to‐medium temperature power cycles are summarized. It is hoped that the results can be of help for related power generation system designs. Copyright © 2014 John Wiley & Sons, Ltd.     

ECLIPSE: An integrated energy-economy model for climate policy and scenario analysis

This paper describes the development of the Energy and Climate Policy and Scenario Evaluation (ECLIPSE) model—a flexible integrated assessment tool for energy and climate change policy and scenario assessment. This tool builds on earlier efforts to link top-down and bottom-up models, and combines a macroeconomic energy demand model and a consumer-budget transport demand model with the technology-rich bottom-up energy and transport system model Energy Research and Investment Strategy (ERIS), and solves the models iteratively. Compared to previous efforts, ECLIPSE includes many new features, such as a more disaggregated production function, improved calibration and parameterization and separate modeling of passenger transport demand. The separate modeling of transportation makes ECLIPSE particularly well-suited to analyzing interactions between the transport sector and the broader energy market and economy. This paper presents results illustrating some features of the integrated model, compares technology deployment results with ECLIPSE and the bottom-up ERIS model, and briefly describes illustrative baseline and greenhouse gas mitigation scenarios to highlight some of the features of the framework outlined in this paper. A number of modeling and policy insights arising from this scenario analysis are discussed.     

Integrated energy balance analysis of a stand‐alone wind power system for various typical Aegean Sea regions

The wind power industry is nowadays a mature energy production sector disposing to market commercial wind converters from 50 W up to 5 MW. In the present work the possibility of using stand‐alone electricity production systems based on a small wind turbine in order to meet the electricity requirements of remote consumers is analysed for selected Aegean Sea regions possessing representative wind potential types. The proposed configuration results from an extensive long‐term meteorological data analysis on a no‐load rejection condition basis during the entire time period examined. Accordingly, an integrated energy balance analysis is carried out for the whole time period investigated, including also the system battery depth‐of‐discharge distribution versus time. Finally, the predicted optimum system configuration is compared to other existing technoeconomic alternatives on a simplified total production cost basis. The results support the viability of similar solutions, especially for areas of high or medium wind potential. Copyright © 2002 John Wiley & Sons, Ltd.     

Synthesis of carbon nanomaterials for dye‐sensitized solar cells

In this paper, it was demonstrated that Na₂O can react with CO to produce carbon nanofibers at 500 °C and carbon nanosheets at 550 °C. Furthermore, the nanosheets exhibited excellent performance as a counter electrode for a dye‐sensitized solar cell (DSSC), leading to a high power conversion efficiency of 7.57%. The efficiency is larger than that (4.72%) of a DSSC with the carbon nanofiber counter electrode and even comparable with that of an expensive Pt‐based DSSC. Copyright © 2015 John Wiley & Sons, Ltd.     

Life-cycle energy analysis of building integrated photovoltaic systems (BiPVs) with heat recovery unit

Building integrated photovoltaic (BiPV) systems generate electricity, but also heat, which is typically wasted and also reduces the efficiency of generation. A heat recovery unit can be combined with a BiPV system to take advantage of this waste heat, thus providing cogeneration. Two different photovoltaic (PV) cell types were combined with a heat recovery unit and analysed in terms of their life-cycle energy consumption to determine the energy payback period. A net energy analysis of these PV systems has previously been performed, but recent improvements in the data used for this study allow for a more comprehensive assessment of the combined energy used throughout the entire life-cycle of these systems to be performed. Energy payback periods between 4 and 16.5 years were found, depending on the BiPV system. The energy embodied in PV systems is significant, emphasised here due to the innovative use of national average input–output (I–O) data to fill gaps in traditional life-cycle inventories, i.e. hybrid analysis. These findings provide an insight into the net energy savings that are possible with a well-designed and managed BiPV system.     

Narrative scenario development based on cross-impact analysis for the evaluation of global-warming mitigation options

Social, technological, economic and environmental issues should be considered comprehensively for the evaluation of global-warming mitigation options. Existing integrated assessment models include assessment of quantitative factors; however, these models do not explicitly consider interactions among qualitative factors in the background – for example, introductions of nuclear power stations interact with social acceptability. In this paper, we applied a technological forecasting method – the cross-impact method – which explicitly deals with the relationships among relevant factors, and we then developed narrative scenarios having consistency with qualitative social contexts. An example of developed scenarios in 2050, assuming the global population and the gross domestic product are the same as those of the A1 scenario of the IPCC Special Report on Emissions Scenarios, tells us that: (1) the Internet will be extensively used in all regions; (2) the global unified market will appear; (3) regional cultures will tend to converge; (4) long-term investments (of more than 30 years) will become difficult and therefore nuclear-power stations will not increase so remarkably; (5) the self-sufficient supply and diversification of primary energy sources will not progress so rapidly; and (6) due to the widespread use of the Internet, people will be more educated in global environmental issues and environmental costs will be more socially acceptable.     

Evaluation of Mg‐MOF‐74 for post‐combustion carbon dioxide capture through pressure swing adsorption

This paper presents a computational study of an energy‐efficient technique for post‐combustion CO₂ capture using novel material, namely, Mg‐MOF‐74, using pressure swing adsorption (PSA) processes. A detailed one‐dimensional, transient mathematical model has been formulated to include the heat and mass transfer, the pressure drop and multicomponent mass diffusion. The PSA model has been further extended by incorporating a heat regenerating process to enhance CO₂ sequestration. The heat dissipated during adsorption is stored in packed sand bed and released during desorption step for heating purpose. The model has been implemented on a MATLAB program using second‐order discretization. Validation of the model was performed using a complete experimental data set for CO₂ sequestration using zeolite 13X. Simulation of the PSA experiment on fixed bed has been carried out to evaluate the capacity of Mg‐MOF‐74 for CO₂ capture with varying feed gas temperature of 28 and 100 °C, varying pressurization and purge times and heat regeneration. It was discovered that the PSA process with heat regeneration system might be advantageous because it achieves equivalent amount of CO₂ sequestration in fewer PSA cycles compared with PSA without heat regeneration system. Based on the simulated conditions, CO₂ recovery with Mg‐MOF‐74 gives high percentage purity (above 98%) for the captured CO₂. Copyright © 2015 John Wiley & Sons, Ltd.     

Thermodynamic analysis of high‐ash coal‐fired power plant with carbon dioxide capture

A thermodynamic analysis of a 500‐MWe subcritical power plant using high‐ash Indian coal (base plant) is carried out to determine the effects of carbon dioxide (CO₂) capture on plant energy and exergy efficiencies. An imported (South African) low‐ash coal is also considered to compare the performance of the integrated plant (base plant with CO₂ capture plant). Chemical absorption technique using monoethanolamine as an absorbent is adopted in the CO₂ capture plant. The flow sheet computer program “Aspen Plus” is used for the parametric study of the CO₂ capture plant to determine the minimum energy requirement for absorbent regeneration at optimum absorber–stripper configuration. Energy and exergy analysis for the integrated plant is carried out using the power plant simulation software “Cycle‐Tempo”. The study also involves determining the effects of various steam extraction techniques from the turbine cycle (intermediate‐pressure–low‐pressure crossover pipe) for monoethanolamine regeneration. It is found that the minimum reboiler heat duty is 373 MW_th (equivalent to 3.77 MJ of heat energy per kg of CO₂ captured), resulting in a drop of plant energy efficiency by approximately 8.3% to 11.2% points. The study reveals that the maximum energy and exergy losses occur in the reboiler and the combustor, respectively, accounting for 29% and 33% of the fuel energy and exergy. Among the various options for preprocessing steam that is extracted from turbine cycle for reboiler use, “addition of new auxiliary turbine” is found to be the best option. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance analysis on industrial refrigeration system integrated with encapsulated PCM‐based cool thermal energy storage system

Cool thermal energy storage (CTES) is an advanced energy technology that has recently attracted increasing interest for industrial refrigeration applications such as process cooling, food preservation and building air conditioning systems. An experimental investigation on the performance of an industrial refrigeration system integrated with encapsulated phase change material (PCM)‐based CTES system is carried out in the present work. In the experimental set‐up a vertical storage tank is integrated with the evaporator of the vapour compression refrigeration system. Effect of the inlet temperature of heat transfer fluid (HTF) on the temperature variation of the PCM and the HTF in the storage tank and the performance parameters namely average rate of charging, energy stored, specific energy consumption (SEC) of the chiller with and without storage system are studied in detail. The effect of porosity variation in the storage tank is also studied. A 1°C decrease in evaporator temperature results in about 3–4% increase in SEC and 1°C decrease in condensing temperature leads to 2.25–3.25% decrease in SEC. The range of HTF inlet temperature and porosity values for optimum performance is reported. Copyright © 2007 John Wiley & Sons, Ltd.     

Analysis of the current methods used to size a wind/hydrogen/fuel cell‐integrated system: A new perspective

As an alternative to the production and storage of intermittent renewable energy sources, it has been suggested that one can combine several renewable energy technologies in one system, known as integrated or hybrid system, that integrate wind technology with hydrogen production unit and fuel cells. This work assesses the various methods used in sizing such systems. Most of the published papers relate the use of simulation tools such as HOMER, HYBRID2 and TRNSYS, to simulate the operation of different configurations for a given application in order to select the best economic option. But, with these methods one may not accurately determine certain characteristics of the energy resources available on a particular site, the profiles of estimated consumption and the demand for hydrogen, among other factors, which will be the optimal parameters of each subsystem. For example, velocity design, power required for the wind turbine, power required for the fuel cell and electrolyzer and the storage capacity needed for the system. Moreover, usually one makes excessive use of bi‐parametric Weibull distribution function to approximate the histogram of the observed wind to the theoretical, which is not appropriate when there are bimodal frequency distributions of wind, as is the case in several places in the world. A new perspective is addressed in this paper, based on general system theory, modeling and simulation with a systematic approach and the use of exergoeconomic analysis. There are some general ideas on the advantages offered in this method, which is meant for the implementation of wind/hydrogen/fuel cell‐integrated systems and in‐situ clean hydrogen production. Copyright © 2009 John Wiley & Sons, Ltd.