Hydrogen production from solar energy powered supercritical cycle using carbon dioxide

A hydrogen production method is proposed, which utilizes solar energy powered thermodynamic cycle using supercritical carbon dioxide (CO₂) as working fluid for the combined production of hydrogen and thermal energy. The proposed system consists of evacuated solar collectors, power generating turbine, water electrolysis, heat recovery system, and feed pump. In the present study, an experimental prototype has been designed and constructed. The performance of the cycle is tested experimentally under different weather conditions. CO₂ is efficiently converted into supercritical state in the collector, the CO₂ temperature reaches about 190 °C in summer days, and even in winter days it can reach about 80 °C. Such a high-temperature realizes the combined production of electricity and thermal energy. Different from the electrochemical hydrogen production via solar battery-based water splitting on hand, which requires the use of solar batteries with high energy requirements, the generated electricity in the supercritical cycle can be directly used to produce hydrogen gas from water. The amount of hydrogen gas produced by using the electricity generated in the supercritical cycle is about 1035 g per day using an evacuated solar collector of 100.0 m² for per family house in summer conditions, and it is about 568.0 g even in winter days. Additionally, the estimated heat recovery efficiency is about 0.62. Such a high efficiency is sufficient to illustrate the cycle performance.     

Use of solar energy to reduce carbon dioxide

It is thermodynamically possible to decompose carbon dioxide to carbon and oxygen by means of thermochemical cycles analogous to cyclic processes for decomposing water. Highly concentrated solar energy can supply the necessary energy at temperatures that permit short, efficient cycles. The reduced carbon can be converted to fuels that are dense, convenient, and require no major changes in the consuming sector of the economy.     

Analysis and forecast of the Tianjin industrial carbon dioxide emissions resulted from energy consumption

This paper analyses the carbon dioxide emissions caused by industrial energy consumption of Tianjin from 2005 to 2012. The carbon emissions decomposition illustrated that the scale of production factor played a major role in the growth of Tianjin industrial carbon emissions and the average contribution of carbon emissions is up to 220.8975% in the statistical period; the intensity of energy factor played an important role in slowing down the growth of industrial carbon dioxide emissions. The average contribution of carbon emissions was ?136.1994% in the statistical period. The prediction model based on carbon emissions data from industrial energy consumption from 2003 to 2012 reached a high accuracy, with an average error of 1.78% for stochastic impacts by regression on population, affluence, and technology (STIRPAT) model, 2.41% for the Logistic regression model and an average error of 1.54% for the grey model. This research can contribute to predict the carbon emission and through it some suggestions can be made.     

Negative carbon intensity of renewable energy technologies involving biomass or carbon dioxide as inputs

Conventional fossil fuel-based energy technologies can achieve efficiency in energy conversion but they are usually completely inefficient in carbon conversion because they generate significant CO₂ emissions to the atmosphere per unit energy converted. In contrast, some renewable energy technologies characterized by negative carbon intensity can simultaneously achieve efficiency in the conversion of energy and in the conversion of carbon. These carbon negative renewable energy technologies can generate useful energy and remove CO₂ from the atmosphere, either by direct capture and recycling of atmospheric CO₂ or indirectly, by involving biofuels. Interestingly, the deployment of carbon negative renewable energy technologies can offset carbon emissions from conventional fossil fuel-based energy technologies and thus reduce the overall carbon intensity of energy systems.The current review analyzes two groups of renewable energy technologies involving biomass or CO₂ as inputs. The discussions focus on useful techniques which enable to achieve negative carbon intensity of energy while being technologically promising in near-term as well as cost-effective. These analyzes include advanced carbon sequestration concepts such as soil carbon sequestration and CO₂ recycling to useful C-rich products such as fuels and fertilizers. The 'drop-in' of renewable energy is achieved by allowing bioenergy and renewable energies in the form of renewable electricity, renewable thermal energy, solar energy, renewable hydrogen, etc. The carbon negative renewable energy technologies are analyzed and perspectives and constraints of each technology are expounded.     

利用环境再冷的二氧化碳储能热电联产系统及其热力学分析

为提升光电出力特性及灵活性,构建光储协同系统成为改善光电可调度性与减少弃光的主流趋势.本文基于光伏电场运营环境特点,提出一种利用夜间环境冷量再冷的二氧化碳储能热电联产系统,重点分析了不同运行模式下系统性能随关键参数的变化规律.结果表明:太阳能集热系统单独工作模式下,增大蓄冷回热器最小温差、夜间环境温度和低压罐压力会导致...     

太阳能技术对我国未来减排CO2的贡献

1世界对可再生能源减排作用的估计可再生能源不但是重要的后续能源,而且对未来减排CO2将发挥重要作用。国际上许多组织和国家预测,本世纪中叶可再生能源在一次性能源消耗中将超过50%。最近20年来,各种可再生能源技术的日趋成熟和生产规模的不断扩大,对能源的贡献也日渐增大。可以预料,随着可再生能源的快速发展,对未来CO2减排的贡献会越来越大。为加速发展中国家可再生能源的发展,1996年世界银行通过全球环境基金(GEF)项目,对未来CO2的排放作了如下估计:如果不采取措施,50年后,大气中CO2的含量就是现在的3.5倍,如果积极采取各种清洁能…     

超临界二氧化碳布雷顿循环发电系统热力学分析

为了对超临界二氧化碳布雷顿循环发电系统热力学进行分析,首先构建了分流再压缩和一次再热耦合的超临界二氧化碳布雷顿循环系统主要关键部件的数学分析模型,并基于Matlab软件进行计算分析。分别讨论了系统主要关键参数对系统循环效率的影响。从仿真结果可以看出存在最佳的分流系数,最优的压缩机入口温度、压力和再热压力,使得循环系统具有较高的循环效率。最后为能够全面地反映系统综合性能,引入了遗传算法作为优化分析方法,研究多参数对系统循环效率的综合影响,得到最高效率点的最优关键参数。     

Study on solidification of carbon dioxide using cold energy of liquefied natural gas

The present paper deals with solidification characteristics of carbon dioxide around the gas feed nozzle of the flue gas from a thermal energy power plant. The present experiment was carried out under dioxide contents between 3 and 50 vol%. The results obtained indicate that the solidification fraction of carbon dioxide increased with a decrease in cooling temperature. The solidification fraction of carbon dioxide was expressed as a function of the nondimensional temperature and concentration of the carbon dioxide. © 2000 Scripta Technica, Heat Trans Asian Res, 29(4): 249–268, 2000     

The energy efficiency of carbon dioxide fixation by a hydrogen-oxidizing bacterium

Fixing carbon dioxide (CO₂) with solar hydrogen (H₂) is a novel alternative to conventional photosynthesis of plants and microalgae. The energy efficiency of CO₂ fixation by a hydrogen-oxidizing bacterium was investigated in a closed reactor system. The molar ratio of consumed H₂ and CO₂ was measured under mass transfer limitation in atmospheres of sufficient H₂, low CO₂, and a broad range of O₂. The energy efficiency, ranging from 10% to 60%, was primarily affected by the oxygen concentration (6–30 mol%). The research revealed a clear trend that a low oxygen concentration gave high energy efficiency, but slow gas consumption. A high energy efficiency of 50% was measured under a moderate oxygen concentration (10 mol%). Based on 10% solar hydrogen efficiency, a 5% overall efficiency from solar energy to biomass can therefore be achieved.     

Solar energy fixation of carbon dioxide via cadmium sulphide and other semiconductor photocatalysts

Aqueous carbon dioxide is photochemically reduced in the presence of semiconductor suspensions and colloids. Experiments have been performed using CdS, ZnO, SiC, Ba TiO₃, and SrTiO₃, dispersions. Product analysis showed the formation of formic acid formaldehyde, sometimes methanol and in the presence of tetramethylammonium chloride, two-carbon products such as glyoxylic and acetic acids and sometimes acetaldehyde. Product yields and photochemical yields were studied as a function of pH, solution composition, added sacrifical electron donors and catalysts, irradiation intensity and irradiation time. A demonstration experiment with a flat-bed solar collector showed the formation of formic acid and formaldehyde using direct sunlight.     

The photo-electrochemical production of c-c bonds from carbon dioxide

It is shown that solar light can be used to reduce CO₂ to C? C bonds with electricity as a by-product.     

Performance modelling of a carbon dioxide removal system for power plants

In this paper, a carbon dioxide removal and liquefaction system, which separates carbon dioxide from the flue gases of conventional power plants, was modelled. The system is based on an amine chemical absorption stripping system, followed by a liquefaction unit to treat the removed CO₂ for transportation and storage. The effect of the main parameters on the absorption and stripping columns is presented. The main constraints set for the model are a capture efficiency of 90% and the use of an aqueous solution with a maximum 30% amine content by weight. The goal of this study is to remove the CO₂ with minimum energy requirements for the process when it is integrated in a fossil fuel fired power plant. Results of the simulation are compared to experimental and literature data from feasibility studies and existing plants.

The power plant to which the removal system is connected is a 320 MW steam power plant with steam reheat and 8 feedwater heaters. Two different fossil fuels were considered: coal and natural gas. The effect of the modifications necessary to integrate the CO₂ removal system in the power plant is also studied.

The capital cost of the removal and liquefaction system is estimated, and its influence on the cost of generated electricity is calculated.     

Hydrogen production from methane hydrate with sequestering of carbon dioxide

Methane hydrate exists in large amounts in certain locations, in sea sediments and the geological structures below them and below artic regions permafrost, at low temperature and high pressure. It has recently been shown that there are suitable methods for producing methane, perhaps on a floating platform. There it could be reformed in an endothermic process to produce hydrogen and carbon dioxide. Some of the methane could be used to provide heat energy for a power plant on the platform to provide all needed power and support for the reforming process. After separation, hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform could be separated from other gases and then sequestered, in one of several possible forms. In this way, hydrogen could be made available without the release of carbon dioxide to the atmosphere and the hydrogen could be an enabling step toward a world hydrogen economy, free of particles and carbon dioxide pollution.     

跨临界CO2热泵热水器的应用研究

分析CO2在热泵热水器中跨临界循环的原理及特点,阐述了CO2用于热泵热水器的优势,概述了国内外跨临界CO2热泵热水器的应用情况及关键零部件的研究开发。     

Determinants of carbon dioxide emissions: Empirical evidence from 69 countries

This study investigates the determinants of carbon dioxide emissions (CO₂) for a global panel consisting of 69 countries using a dynamic panel data model. To make the panel data analysis more homogenous, we also investigate the determinants of CO₂ emissions for a number of sub-panels. These sub-panels are constructed based on the income level of countries. In this way, we end up with three income panels; namely, high income, middle income, and low income panels. The time component of our dataset is 1985–2005 inclusive. Our main findings are that trade openness, per capita GDP, and energy consumption, proxied by per capita electric power consumption and per capita total primary energy consumption, have positive effects on CO₂ emissions. Urbanisation is found to have a negative impact on CO₂ emissions in high income, middle income, and low income panels. For the global panel, only GDP per capita and per capita total primary energy consumption are found to be statistically significant determinants of CO₂ emission, while urbanisation, trade openness, and per capita electric power consumption have negative effects on the CO₂ emissions.     

Online analysis of carbon dioxide from a direct ethanol fuel cell

Carbon dioxide yields from a direct ethanol fuel cell have been monitored by using a commercial infrared CO₂ monitor. The time dependence is reported as a function of temperature, current density, and anode catalyst (Pt vs. PtRu). Yields increased strongly with temperature, with a Faradaic yield of 76% being obtained at 100 °C with a Pt black anode. PtRu gave lower yields than Pt by a factor of ca. 3 at 80 and 100 °C, but higher yields than Pt at ambient temperature. The superior ability of PtRu to strip adsorbed CO is important at low temperatures, but not a key factor at 100 °C.     

Production of precipitated calcium carbonate from calcium silicates and carbon dioxide

The possibilities for reducing carbon dioxide emissions from the pulp and paper industry by calcium carbonation are presented. The current precipitated calcium carbonate (PCC) production uses mined, crushed calcium carbonate as raw materials. If calcium silicates were used instead, carbon dioxide emissions from the calcination of carbonates would be eliminated. In Finland, there could, thus, be a potential for eliminating 200 kt of carbon dioxide emissions per year, considering only the PCC used in the pulp and paper industry. A preliminary investigation of the feasibility to produce PCC from calcium silicates and the potential to replace calcium carbonate as the raw material was made. Calcium carbonate can be manufactured from calcium silicates by various methods, but only a few have been experimentally verified. The possibility and feasibility of these methods as a replacement for the current PCC production process was studied by thermodynamic equilibrium calculations using HSC software and process modelling using Aspen Plus^®. The results from the process modelling showed that a process that uses acetic acid for extraction of the calcium ions is a high potential option for sequestering carbon dioxide by mineral carbonation. The main obstacle seems to be the limited availability and relatively high price of wollastonite, which is a mineral with high calcium silicate content. An alternative is to use the more common, but also more complex, basalt rock instead.     

Grey relation performance correlations among economics,energy use and carbon dioxide emission in Taiwan

This study explores the inter-relationships among economy, energy and CO₂ emissions of 37 industrial sectors in Taiwan in order to provide insight regarding sustainable development policy making. Grey relation analysis was used to analyse the productivity, aggregate energy consumption, and the use of fuel mix (electricity, coal, oil and gas) in relation to CO₂ emission changes. An innovative evaluative index system was devised to explore grey relation grades among economics, energy and environmental quality. Results indicate that a rapid increase in electricity generation during the past 10 years is the main reason for CO₂ emission increase in Taiwan. The largest CO₂ emitting sectors include iron and steel, transportation, petrochemical materials, commerce and other services. Therefore, it is important to reduce the energy intensity of these sectors by energy conservation, efficiency improvement and adjustment of industrial structure towards high value-added products and services. Economic growth for all industries has a more significant influence, than does total energy consumption, on CO₂ emission increase in Taiwan. It is also important to decouple the energy consumption and production to reduce the impacts of CO₂ on economic growth. Furthermore, most of the sectors examined had increased CO₂ emissions, except for machinery and road transportation. For high energy intensive and CO₂ intensive industries, governmental policies for CO₂ mitigation should be directed towards low carbon fuels as well as towards enhancement of the demand side management mechanism, without loss of the nation's competitiveness.     

The performance of the Norwegian carbon dioxide,capture and storage innovation system

In order to take up Norway's twin challenge of reducing CO₂ emissions, while meeting its growing energy demand with domestic resources, the deployment of carbon capture and storage (CCS) plays an important role in Norwegian energy policies. This study uses the Functions of Innovation Systems approach to identify key policy issues that need to be addressed in order to prolong Norway's international leadership position in the development of CCS. The analysis shows that Norway has been successful in building an innovation system around CCS technology. The key determinants for this achievement are pinpointed in this article. However, the evolution of the innovation system seems to have entered a critical phase that is decisive for a further thriving development of CCS in Norway. The results provide a clear understanding of the current impediments in the CCS innovation system and stress the need to direct policy initiatives at the identified weak system functions—i.e. entrepreneurial activity and market formation—to improve the performance of the system. We discuss how policymakers can use these insights to develop a coherent set of policy instruments that would foster the deployment of CCS concepts related to power production and enhanced oil recovery in Norway.