Bioenergy from forest thinning: Carbon emissions,energy balances and cost analyses

The growing demand for bioenergy in Sweden has drawn attention to the potential of forest thinning as bioenergy feedstock. There are, however, concerns regarding the cost effectiveness and environmental challenges of harvesting and processing forest thinnings into bioenergy. It is against this background that cost, energy and carbon balances were analysed to evaluate some of the economic and environmental sustainability issues of forest thinning based bioenergy systems. Primary data was collected from two thinning operations in two forest plots comprising spruce and birch stands. One operation involved the use of the conventional two machines (one separate machine for cutting or felling and another for forwarding felled trees) for the thinning work. The second operation involved a harwarder, which combines tree felling/cutting and forwarding in one unit machine. The results showed that forest thinnings provide a potential resource for the sustainable production of bioenergy.     

Comparison study on different ITM‐integrated MCFC hybrid systems with CO2 recovery using sweep gas

Previous study shows the ITM (oxygen ion transfer membrane)‐integrated MCFC (molten carbonate fuel cell) hybrid system with CO₂ recovery can maintain high efficiency; however, the oxygen partial pressure on the ITM permeate side is usually 1 atm, which requires a very high pressure ratio of the ITM air compressor in order to separate the oxygen; using the sweep gas can solve this problem. In this paper the ITM‐integrated MCFC hybrid systems with CO₂ recovery using different sweep gases are studied. With the Aspen plus software, two systems with different sweep gases are established, and their performances are compared with the benchmark system without sweep gas; the effects of key parameters on the optimum system performance are also investigated. Results show that compared with the benchmark system, the efficiencies of the systems with sweep gases are increased and the pressure ratios of the air compressors are decreased; the system using pure CO₂ as sweep gas can improve the system efficiency by 1.25%, which is superior to the system using the mixture gas of CO₂ and H₂O as sweep gas. Achievements from this paper will provide a valuable reference for CO₂ recovery from the MCFC hybrid power system with lower energy consumption. Copyright © 2016 John Wiley & Sons, Ltd.     

A comparative analysis of energy and CO2 taxes on the primary energy mix for electricity generation

In many countries, economies are moving towards internalization of external costs of greenhouse‐gas (GHG) emissions. This can best be achieved by either imposing additional taxes or by using an emission‐permit‐trading scheme. The electricity sector is under scrutiny in the allocation of emission‐reduction objectives, not only because it is a large homogeneous target, but also because of the obvious emission‐reduction potential by decreasing power generation based on carbon‐intensive fuels. In this paper, we discuss the impact of a primary‐energy tax and a CO₂ tax on the dispatching strategy in power generation. In a case study for the Belgian power‐generating context, several tax levels are investigated and the impact on the optimal dispatch is simulated. The impact of the taxes on the power demand or on the investment strategies is not considered. As a conclusion, we find that a CO₂ tax is more effective than a primary‐energy tax. Both taxes accomplish an increased generation efficiency in the form of a promotion of combined‐cycle gas‐fired units over coal‐fired units. The CO₂ tax adds an incentive for fuel switching which can be achieved by altering the merit order of power plants or by switching to a fuel with a lower carbon content within a plant. For the CO₂ tax, 13 €/tonCO₂ is withheld as the optimal value which results in an emission reduction of 13% of the electricity‐related GHG emissions in the Belgian power context of 2000. A tax higher than 13 €/tonCO₂ does not contribute to the further reduction of GHGs. Copyright © 2005 John Wiley & Sons, Ltd.     

节能减排可再生能源有大作为

在刚刚闭幕的两会上,节能减排引起了代表们的广泛关注。温总理在《政府工作报告》中坦承"去年全国没有实现年初确定的单位国内生产总值能耗降低4%左右,主要污染物排放总量减少2%的目标。"实际上"十一五"开局之年,我国单位GDP能耗仅下降1.23%,而COD和CO_2排放量不降反升,分别增长1.9%和2.4%。可见节能减排形势严峻,任重道远。需要下大力气,有新的大举措。     

CO2 emissions,energy consumption and economic growth in Turkey

This paper examines the long run and causal relationship issues between economic growth, carbon emissions, energy consumption and employment ratio in Turkey by using autoregressive distributed lag bounds testing approach of cointegration. Empirical results for Turkey over the period 1968–2005 suggest an evidence of a long-run relationship between the variables at 5% significance level in Turkey. The estimated income elasticity of carbon emissions per capita is ?0.606 and the income elasticity of energy consumption per capita is 1.375. Results for the existence and direction of Granger causality show that neither carbon emissions per capita nor energy consumption per capita cause real GDP per capita, but employment ratio causes real GDP per capita in the short run. In addition, EKC hypothesis at causal framework by using a linear logarithmic model is not valid in Turkish case. The overall results indicates that energy conservation policies, such as rationing energy consumption and controlling carbon dioxide emissions, are likely to have no adverse effect on the real output growth of Turkey.     

Heat integration,energy management,CO2 capture and heat transfer enhancement

This editorial introduces and provides an overview of a Special Issue dedicated to the 9th conference Process Integration, Modelling and Optimisation for Energy Saving and Pollution Reduction – PRES 2006. It contains eleven selected papers covering various field of thermal engineering focusing on recent development in heat integration, energy management, CO₂ capture and sequestration, and various aspects of heat transfer and its enhancement, optimisation and fouling minimisation. It covers several interesting applications in the food industry, district cooling, fuel cells, and burner optimisation.     

Energy and economic evaluation of cooling,heating, and power systems based on primary energy

Cooling, Heating, and Power (CHP) systems have the potential to make better use of fuels than other technologies because of their ability to increase the overall thermal energy efficiency. Feasibility of CHP systems is generally driven by economic savings. In addition, economic evaluation of CHP systems is based on site energy use and cost, which could lead to misleading conclusions about energy savings. Since energy savings from CHP systems only occurs in primary energy, the objective of this investigation is to demonstrate that feasibility of CHP systems should be performed based on primary energy savings followed by economic considerations. This paper also evaluates the effect of the power generation unit (PGU) efficiency over the primary energy reduction when a CHP system is utilized. The advantages of operating CHP systems under a primary energy operational strategy, such as the proposed Building Primary Energy Ratio (BPER) strategy, are also discussed. Results show that for some cases economic savings are attained without the corresponding primary energy savings. However, the use of the BPER operational strategy guarantees better energy performance regardless of economic savings. Regarding to the PGU efficiency, an increase of the efficiency reduces the primary energy use more than proportionally. For example, increasing the PGU efficiency from 0.25 to 0.35 (increase of 40%) can reduce the primary energy use from 5.4% to 16% (increase of 200%).     

不同培养模式对能源微藻生物质产率的影响

以普通小球藻(Chlorella vulgaris)为研究对象,利用模拟烟道气(15%CO2+85%N2)分别研究批次、流加和半连续3种不同培养模式对普通小球藻生长的影响。研究结果表明,普通小球藻对15%的CO2具有很好的耐受性,生物量明显增加;流加氮源(硝酸钠)可以提高小球藻的生物量,比批次培养高0.355g/L;采用半连续培养模式,更新率为1/4,1/3时,小球藻的生物质产率分别为253mg/(L·d),198mg/(L·d),均高于批次培养的产率。说明通过采用不同培养模式利用烟道气CO2培养普通小球藻提高生物量是完全可行的,为微藻规模培养奠定了理论基础。     

Analysis of combined cooling,heating, and power systems based on source primary energy consumption

Combined cooling, heating, and power (CCHP) is a cogeneration technology that integrates an absorption chiller to produce cooling, which is sometimes referred to as trigeneration. For building applications, CCHP systems have the advantage to maintain high overall energy efficiency throughout the year. Design and operation of CCHP systems must consider the type and quality of the energy being consumed. Type and magnitude of the on-site energy consumed by a building having separated heating and cooling systems is different than a building having CCHP. Therefore, building energy consumption must be compared using the same reference which is usually the primary energy measured at the source. Site-to-source energy conversion factors can be used to estimate the equivalent source energy from site energy consumption. However, building energy consumption depends on multiple parameters. In this study, mathematical relations are derived to define conditions a CCHP system should operate in order to guarantee primary energy savings.     

The effect of capillary-trapped CO2 on oil recovery and CO2 sequestration during the WAG process

This study investigated capillary-trapped CO₂ depending on the consideration of hysteresis effect in relative permeability for various water-alternation-gas (WAG) operating conditions to ascertain the oil production process. From the simulation results of CO₂ WAG flooding method, the trapped CO₂ led to prevent water-flow, in which CO₂ acts as a gas blocker near the well. It caused the injection pressure increase during water injection period. As the trapped CO₂ in pores increased, the reservoir pressure was also increased and maintained above minimum miscibility pressure (MMP). Ultimately, it was concluded that the reservoir was kept under miscible conditions throughout WAG process, reducing residual oil and increasing oil recovery.     

The renewable energy,CO2 emissions,and economic growth: VAR model

This paper provides an empirical analysis of CO₂ emissions and economic growth, renewable energy consumption, and energy consumption over the period 1975–2014 in Germany. This paper uses the autoregressive distributed lag (ARDL) approach of cointegration test and vector error-correction models. The unit root and cointegration tests show that the long-run relationship between CO₂ emissions and its determinants. The empirical results show that the findings do not support the environmental Kuznets curve between real GDP and CO₂ emissions. To estimate the shocks of renewable energy consumptions, the study applies the dynamic test of Impulse Response Function (IRF) under the VAR method. The increasing portion of renewable energy consumption in electricity generation would have no impacts on the environment. However, the hikes of renewable energy sources would incur more cost to electricity producers and shrivel up the growth of economies through the expansionary effect of industry’s consumption and private capital spending in the Germany’s economy.     

Assessing long-term impacts of increased crop productivity on atmospheric CO2

A full assessment of the impacts of land clearance and crop production on atmospheric CO2 requires a systems approach. By considering long-term soil carbon changes and fossil fuel energy inputs, we show that increased crop productivity will alleviate CO2 release to the atmosphere primarily by preventing additional land cultivation. Each hectare of cropland undergoing a simulated threefold crop productivity increase here prevents a net release on the order of 150-200 Mg C to the atmosphere over 100 years by avoiding additional land cultivation which would otherwise be required. This effective carbon sink would slowly diminish with time due to fossil fuel energy input requirements. However, future self-containment of the energy needs of high-yield crop production may displace on the order of 1.0 Pg C per year of fossil fuel carbon, in addition to the carbon sink attributable to avoided land cultivation. By avoiding land cultivation, high yield crop systems also preserve natural ecosystems.     

Urbanization,energy use,and CO2 emissions: A provincial-level analysis of China

Most previous studies have studied the relationship among urbanization, energy use, and CO₂ emissions. In this paper, Ordinary Least Square (OLS), Fixed Effects (FE), Prais–Winsten (PW), and First Differenced (FD) regression model approaches are applied to analyze the correlation among urbanization, energy use, and CO₂ emissions in the interior provinces and eastern/coastal provinces of China. The results show that the impact of urbanization on CO₂ emissions is not homogenous for all provinces. The eastern/coastal provinces have a different elasticity with respect to per capita Gross Domestic Product (GDP) and urbanization than the interior provinces. Also, it’s possible an Environmental Kuznets Curve (EKC) exists for the eastern provinces but not for China as a whole.     

A new optimization approach to energy network modeling: anthropogenic CO2 capture coupled with enhanced oil recovery

To meet next generation energy needs such as wind‐ and solar‐generated electricity, enhanced oil recovery (EOR), CO₂ capture and storage (CCS), and biofuels, the US will have to construct tens to hundreds of thousands of kilometers of new transmission lines and pipelines. Energy network models are central to optimizing these energy resources, including how best to produce, transport, and deliver energy‐related products such as oil, natural gas, electricity, and CO₂. Consequently, understanding how to model new transmission lines and pipelines is central to this process. However, current energy models use simplifying assumptions for deploying pipelines and transmission lines, leading to the design of more costly and inefficient energy networks. In this paper, we introduce a two‐stage optimization approach for modeling CCS infrastructure. We show how CO₂ pipelines with discrete capacities can be ‘linearized’ without loss of information and accuracy, therefore allowing necessarily complex energy models to be solved. We demonstrate the new approach by designing a CCS network that collects large volumes of anthropogenic CO₂ (up to 45 million tonnes of CO₂ per year) from ethylene production facilities and delivers the CO₂ to depleted oil fields to stimulate recovery through EOR. Utilization of anthropogenic CO₂ has great potential to jumpstart commercial‐scale CCS while simultaneously reducing the carbon footprint of domestic oil production. Model outputs illustrate the engineering challenge and spatial extent of CCS infrastructure, as well as the costs (or profits) of deploying CCS technology. We show that the new linearized approach is able to offer insights that other network approaches cannot reveal and how the approach can change how we develop future energy systems including transporting massive volumes of shale gas and biofuels as well as electricity transmission for wind and solar energy. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Processing and sorting forest residues: Cost,productivity and managerial impacts

Feedstocks generated from processing forest residues have traditionally been considered as a low value product. The economic potential of these materials can be enhanced by emerging biomass conversion technologies, such as torrefaction, briquetting, and gasification; however, these systems require higher quality feedstock. The objective of this study was to determine the cost of processing and sorting forest residues to produce feedstock, so that the best comminution machines (i.e. chipper vs. grinder) could be used to better control feedstock size distribution. The tree tops left from sawlog processing and small-diameter trees were delimbed and separated from the slash pile. Three harvest units were selected and each unit was divided into three sub-treatment units (no-, moderate, and intensive sorting). Results showed that the cost of operations were higher for the sorted sub-units when compared to the non-sorted. The total cost of operation (felling to loading) for sawlogs was lowest at 40.81 $ m⁻³ in the nosorting treatment unit, followed by moderate (42.25 $ m⁻³) and intensive treatment unit (44.75 $ m⁻³). For biomass harvesting, the cost of operation (felling to delimbing and sorting) ranged from 27 to 29 $ oven dry metric ton⁻¹. The most expensive operational phase was primary transportation; therefore, cost of treating the forest residues had less impact on the overall cost. The cost increase (1150 $ ha⁻¹) of sorting forest residues could offset cost savings from avoided site preparation expenses (1100 $ ha⁻¹), provided that the forest residues were utilized.     

Updated band model parameters for H2O,CO2, CH4 and CO radiation at high temperature

Statistical narrow-band (SNB) model parameters for H₂O, CO₂, CH₄ and CO, and correlated-k (CK) parameters for H₂O and CO₂ are generated from line by line calculations and recently improved spectroscopic databases in wide temperature and spectral ranges. Results from the new parameters are compared to direct line by line calculations and to results from earlier model parameters [A. Soufiani, J. Taine, High temperature gas radiative property parameters of statistical narrow-band model for H₂O, CO₂ and CO and correlated-k (ck) model for H₂O and CO₂, Int. J. Heat Mass Transfer 40 (1997) 987–991] in terms of band averaged spectral transmissivities, Planck mean absorption coefficients, and total emissivities. The comparisons show first a good agreement between updated SNB, CK and LBL results. Significant improvements on earlier parameters are observed for H₂O and CO₂, especially at very high temperatures and path lengths. Model parameters and computer programs illustrating their implementation are provided as Supplementary data.     

A review of heat pipe systems for heat recovery and renewable energy applications

Advancements into the computational studies have increased the development of heat pipe arrangements, displaying multiphase flow regimes and highlighting the broad scope of the respective technology for utilization in passive and active applications. The purpose of this review is to evaluate current heat pipe systems for heat recovery and renewable applications utility. Basic features and limitations are outlined and theoretical comparisons are drawn with respect to the operating temperature profiles for the reviewed industrial systems. Working fluids are compared on the basis of the figure of merit for the range of temperatures. The review established that standard tubular heat pipe systems present the largest operating temperature range in comparison to other systems and therefore offer viable potential for optimization and integration into renewable energy systems.     

给力节能减排 促进低碳发展——泰豪“两会”媒体交流会在京召开

合同能源管理(简称EMC)是20世纪70年代在西方发达国家开始发展起来的一种基于市场运作的全新节能机制。在我国蹒跚数十年来,终于迎来了行业发展的春天——继2010年4月初国务院转发《关于加快推行合同能源管理促进节能服务产业发展的意见》后,不久,中央财政就下拨20亿元补贴该行业的发展,而配套政策将陆续出台。而大力发展EMC正是一位政协委员在2010年两会上的一个提案,只是这位委员当时根本没有想     

CO2 abatement and CH4 recovery at vehicle exhausts: Comparison and characterization of Ru powder and pellet catalysts

The catalytic conversion of CO₂ to CH₄ (Sabatier reaction) has been studied to develop an after-treatment process at vehicles exhausts. Three different formulations of Ru commercial catalysts, two in powder and one in pellets shape, were tested and characterized by means of X-ray powder diffraction, scanning electron microscopy (SEM-EDX), N₂ adsorption at −196 °C and temperature-programmed reduction (TPR).Experimental results show a high CO₂ conversion (X_CO2 = 0.96 @ T = 280 °C) for one powder catalyst formulation whereas the other one has maximum CO₂ conversion = 0.69. In both cases a high CH₄ selectivity is measured. High CO₂ conversion (X_CO2 = 0.92 @ T = 300 °C) is obtained also with pellet catalysts but only at lower GHSV values. The different behavior of the catalysts was ascribed to the different physicochemical properties and the key parameters for the application development of the process were identified. In particular, the possibility to use pellets or monolithic reactors, thus minimizing the pressure drops in the reactor, makes possible a commercial application in the treatment of vehicles exhausts.     

The relationship between CO2 emissions,energy consumption and economic growth in Italy

This study examines the relationship between CO₂ emissions, energy consumption and economic growth in Italy over the period 1970–2006. Results of unit root tests show that all variables are non-stationary in their level form, but stationary in first differences form. The causal relationship between variables is examined using causality test in a vector autoregressive framework. Our empirical results show that CO₂ emissions, energy consumption and economic growth are not cointegrated. Moreover, the Toda and Yamamoto Granger non-causality test shows a bidirectional causality between CO₂ emissions and economic growth, as well as between CO₂ emissions and energy consumption. Forecast error variance decompositions evidence that the errors in real per capita GDP are mainly due to uncertainty in GDP itself, while the errors in predicting the energy consumption and the CO₂ emissions are sensitive to disturbances in the other two equations.