Emissions and energy efficiency assessment of baseload wind energy systems

The combination of wind energy generation and energy storage can produce a source of electricity that is functionally equivalent to a baseload coal or nuclear power plant. A model was developed to assess the technical and environmental performance of baseload wind energy systems using compressed air energy storage. The analysis examined several systems that could be operated in the midwestern United States under a variety of operating conditions. The systems can produce substantially more energy than is required from fossil or other primary sources to construct and operate them. By operation at a capacity factor of 80%, each evaluated system achieves an effective primary energy efficiency of at least five times greater than the most efficient fossil combustion technology, with greenhouse gas emission rates less than 20% of the least emitting fossil technology currently available. Life-cycle emission rates of NOx and SO2 are also significantly lower than fossil-based systems.     

造纸工业的节能与增能大有作为

概述了中国造纸工业节能和增能的途径和方法。     

麦当劳即将推出新一代全球包装

<正> 麦当劳自2008年11月起推出新一代全球包装,首度全面展现该品牌历史。未来两年内,麦当劳进驻的118个国家和地区均将参加此次包装推广计划,重点围绕该品牌食品质量的故事,并每天直接传递至约5600万顾客的手中。     

Atmospheric lifetime and global warming potential of a perfluoropolyether

Perfluoropolyethers (PFPEs) are a family of perfluorinated fluids used mainly in industrial applications. Lower molecular weight commercial PFPE fractions have boiling points ranging between 55 and 270 degrees C, and have the potential to escape into the atmosphere. To improve our understanding of the atmospheric chemistry of PFPEs, a distilled fraction of a commercial mixture containing perfluoropolymethylisopropyl ethers (PFPMIEs) was introduced into an atmospheric chamber system. Relative rate techniques were used to determine upper limits for the rate constants for reactions of OH and Cl with PFPMIE in 700 Torr of air at 296 K. The reactivity of PFPMIE with Cl was less than 2 x 10(-17) cm3 molecule(-1) s(-1), while the reactivity with OH was less than 6.8 x 10(-16) cm3 molecule(-1) s(-1), indicating low reactivity in the troposphere. Consequently, the lifetime of PFPMIE should be limited bytransport to the mesosphere, where photolysis by Lyman-alpha radiation at 121.6 nm will be efficient. By analogy to perfluorinated alkanes, the lower limit for the total atmospheric lifetime is 800 years. PFPMIE was shown to have instantaneous radiative forcing of 0.65 W m(-2) ppb(-1), which corresponds to a global warming potential on a 100 year time scale of 9000 relative to CO2 and 1.95 relative to CFC-11.     

Emissions impacts of wind and energy storage in a market environment

This study examines the emissions impacts of adding wind and energy storage to a market-based electric power system. Using Texas as a case study, we demonstrate that market power can greatly effect the emissions benefits of wind, due to most of the coal-fired generation being owned by the two dominant firms. Wind tends to have less emissions benefits when generators exercise market power, since coal-fired generation is withheld from the market and wind displaces natural gas-fired generators. We also show that storage can have greater negative emissions impacts in the presence of wind than if only storage is added to the system. This is due to wind increasing on- and off-peak electricity price differences, which increases the amount that storage and coal-fired generation are used. We demonstrate that this effect is exacerbated by market power.     

42份非木本油料植物资源的能源利用潜力评价

通过对42份非木本油料植物资源的种子（或块茎）舍油量、脂肪酸组成分析,发现舍油量差异很大,92．9％资源中含有C16和C18链长的脂肪酸。对资源的产量、舍油量、脂肪酸组成、适应性、抗逆性等进行综合评价认为,油莎豆、续随子、苍耳等是适合我国国情,适宜在边际地种植,油脂适合作生物柴油原料,是发展潜力较好的新型能源油料植物。     

Wanted: institutions for balancing global food and energy markets

The increasing demand for biomass for energy use is further escalating existing food security risks. Managing these risks is a task for global institutions. These should ensure timely investment in the world’s capacity for producing biomass and balance the use of this biomass for foods and for non-foods. To achieve this, institutional arrangements for global food markets must fulfil two important goals: reduce the short-term price instability of food markets and prevent a structural scarcity of food in the long term. This paper analyses how agro-food markets, energy markets and biofuel markets are currently regulated. As this regulation is ill-suited to manage food price instabilities and balance food and non-food use of biomass, new institutions need to be put in place. A coordinated system of global commodity management — not unlike the Commodity Control Organization proposed by Keynes for the post-WWII era — is proposed to deal with these coming challenges.     

Cost of wind energy: comparing distant wind resources to local resources in the midwestern United States

The best wind sites in the United States are often located far from electricity demand centers and lack transmission access. Local sites that have lower quality wind resources but do not require as much power transmission capacity are an alternative to distant wind resources. In this paper, we explore the trade-offs between developing new wind generation at local sites and installing wind farms at remote sites. We first examine the general relationship between the high capital costs required for local wind development and the relatively lower capital costs required to install a wind farm capable of generating the same electrical output at a remote site,with the results representing the maximum amount an investor should be willing to pay for transmission access. We suggest that this analysis can be used as a first step in comparing potential wind resources to meet a state renewable portfolio standard (RPS). To illustrate, we compare the cost of local wind (～50 km from the load) to the cost of distant wind requiring new transmission (～550-750 km from the load) to meet the Illinois RPS. We find that local, lower capacity factor wind sites are the lowest cost option for meeting the Illinois RPS if new long distance transmission is required to access distant, higher capacity factor wind resources. If higher capacity wind sites can be connected to the existing grid at minimal cost, in many cases they will have lower costs.     

The global potential of bioenergy on abandoned agriculture lands

Converting forest lands into bioenergy agriculture could accelerate climate change by emitting carbon stored in forests, while converting food agriculture lands into bioenergy agriculture could threaten food security. Both problems are potentially avoided by using abandoned agriculture lands for bioenergy agriculture. Here we show the global potential for bioenergy on abandoned agriculture lands to be less than 8% of current primary energy demand, based on historical land use data, satellite-derived land cover data, and global ecosystem modeling. The estimated global area of abandoned agriculture is 385-472 million hectares, or 66-110% of the areas reported in previous preliminary assessments. The area-weighted mean production of above-ground biomass is 4.3 tons ha(-1) y(-1), in contrast to estimates of up to 10 tons ha(-1) y(-1) in previous assessments. The energy content of potential biomass grown on 100% of abandoned agriculture lands is less than 10% of primary energy demand for most nations in North America, Europe, and Asia, but it represents many times the energy demand in some African nations where grasslands are relatively productive and current energy demand is low.     

Reducing the energy penalty costs of postcombustion CCS systems with amine-storage

Carbon capture and storage (CCS) can significantly reduce the amount of CO(2) emitted from coal-fired power plants but its operation significantly reduces the plant's net electrical output and decreases profits, especially during times of high electricity prices. An amine-based CCS system can be modified adding amine-storage to allow postponing 92% of all its energy consumption to times of lower electricity prices, and in this way has the potential to effectively reduce the cost of CO(2) capture by reducing the costs of the forgone electricity sales. However adding amine-storage to a CCS system implies a significant capital cost that will be outweighed by the price-arbitrage revenue only if the difference between low and high electricity prices is substantial. In this paper we find a threshold for the variability in electricity prices that make the benefits from electricity price arbitrage outweigh the capital costs of amine-storage. We then look at wholesale electricity markets in the Eastern Interconnect of the United States to determine profitability of amine-storage systems in this region. Using hourly electricity price data from years 2007 and 2008 we find that amine storage may be cost-effective in areas with high price variability.     

不同保守力势能函数的计算及讨论

对重力势能、弹性势能、静电势能等常见的保守力势能所对应的函数进行了计算与讨论，认为势能零点及坐标原点的选取不影响两点间功的计算，但影响计算的繁简程序，因而应尽量选取默认的势能零点及坐标原点。因需要而改变坐标原点或势能零点时，仍需使用势能的一般计算表达式。     

Power-law relationships for estimating mass, fuel consumption and costs of energy conversion equipments

To perform life-cycle assessment studies, data on the production and use of the products is required. However, often only few data or measurements are available. Estimation of properties can be performed by applying scaling relationships. In many disciplines, they are used to either predict data or to search for underlying patterns, but they have not been considered in the context of product assessments hitherto. The goal of this study was to explore size scaling for commonly used energy conversion equipment, that is, boilers, engines, and generators. The variables mass M, fuel consumption Q, and costs C were related to power P. The established power-law relationships were M = 10(0.73.. 1.89)P(0.64.. 1.23) (R(2) ≥ 0.94), Q = 10(0.06.. 0.68)P(0.82.. 1.02) (R(2) ≥ 0.98) and C = 10(2.46.. 2.86)P(0.83.. 0.85) (R(2) ≥ 0.83). Mass versus power and costs versus power showed that none of the equipment types scaled isometrically, that is, with a slope of 1. Fuel consumption versus power scaled approximately isometrically for steam boilers, the other equipments scaled significantly lower than 1. This nonlinear scaling behavior induces a significant size effect. The power laws we established can be applied to scale the mass, fuel consumption and costs of energy conversion equipments up or down. Our findings suggest that empirical scaling laws can be used to estimate properties, particularly relevant in studies focusing on early product development for which generally only little information is available.     

磁力做功与磁场中的势能

根据磁力做功的特点 ,在非保守场———磁场中也可以引入势能的概念 .通过计算发现 ,磁场中的势能不同于通常意义的势能 ,它既可以是位置坐标的函数 ,也可以是时间的函数     

Estimating the global costs of vitamin A capsule supplementation: a review of the literature

BACKGROUND: Vitamin A supplementation reduces child mortality. It is estimated that 500 million vitamin A capsules are distributed annually. Policy recommendations have assumed that the supplementation programs offer a proven technology at a relatively low cost of around US$0.10 per capsule. OBJECTIVES: To review data on costs of vitamin A supplementation to analyze the key factors that determine program costs, and to attempt to model these costs as a function of per capita income figures. METHODS: Using data from detailed cost studies in seven countries, this study generated comparable cost categories for analysis, and then used the correlation between national incomes and wage rates to postulate a simple model where costs of vitamin A supplementation are regressed on per capita incomes. RESULTS: Costs vary substantially by country and depend principally on the cost of labor, which is highly correlated with per capita income. Two other factors driving costs are whether the program is implemented in conjunction with other health programs, such as National Immunization Days (which lowers costs), and coverage in rural areas (which increases costs). Labor accounts for 70% of total costs, both for paid staff and for volunteers, while the capsules account for less than 5%. Marketing, training, and administration account for the remaining 25%. CONCLUSIONS: Total costs are lowest (roughly US$0.50 per capsule) in Africa, where wages and incomes are lowest, US$1 in developing countries in Asia, and US$1.50 in Latin America. Overall, this study derives a much higher global estimate of costs of around US$1 per capsule.     

Comparison of the energy performance of pulse generation circuits for PEF

Pulse shaped voltages are required for preservation of food with PEF. Several pulse forms generated by a variety of circuits are compared with respect to required energy. The analysis includes square pulses, trapezoidal pulses, exponential decay pulses and oscillatory and over-damped oscillatory pulses. The base of comparison is the establishment of a certain minimum voltage level during certain minimum time. The comparison concerns the dissipation in a resistive load, which is considered to be representative for a category of loads, including PEF. Furthermore, the ratio between initial capacitor voltage and corresponding threshold voltage is compared as this parameter reflects the required hold voltage of the switch in the circuit. The analysis shows that the efficiency approaches 100% for hard switched circuits and circuits with transmission lines. For highly damped RLC-circuits with capacitor C, inductor L and load resistance R the maximum obtainable efficiency is between 37 and 47% where the capacitor C has to be charged to 1.6–1.8 times the desired threshold voltage. For oscillating damped sinusoids the maximum efficiency is between 47 and 52%, however, the capacitor has to be charged to 1.8–3 times the threshold voltage. Graphs with an example are provided to determine circuit parameters from a certain pulse specification.     

Growth and energy generation by Enterococcus faecium FAIR-E 198 during citrate metabolism

Citrate metabolism by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in various growth media containing citrate either in the presence of glucose, or as the sole carbon source, both under aerobic and anaerobic conditions. In de Man-Rogosa-Sharpe (MRS) broth with increasing citrate concentrations, cometabolism of citrate and glucose took place. Glucose was stoichiometrically converted into lactate, while citrate into acetate. Glucose consumption and biomass yield were enhanced with increasing initial citrate concentrations, even though maximum specific growth rate was not. When citrate was used as the sole carbon source in increasing initial concentrations, the main end product was acetate. Small amounts of lactate, formate, ethanol, and acetoin were also produced. In all cases, no significant differences were observed between aerobic and anaerobic conditions. However, when citrate was used as sole carbon source, formate production was favored in the absence of oxygen. The present work shows that E. faecium is able to utilize citrate in synthetic media, either in the presence of glucose or as the sole carbon source, resulting in energy production and the formation of aroma compounds.     

Evaluation of potential prebiotics: a review

Prebiotics are any undigested food ingredients that are selectively fermented and allow for specific changes in the gut microbiota, thus improving the hosts’ health. In order to assess the potential of a food component to be considered as a prebiotic ingredient, several in vitro and in vivo experimentations need to be performed to provide scientific substantiation. In vitro studies are widely used because they are faster, cheaper, and more ethical compared to in vivo studies. However, in vitro studies faced difficulties in simulating the highly complex physiological and physiochemical events occurring in animal and human digestive tracts. Therefore, it is recommended that the results of in vitro studies be justified with in vivo experimentations to support their specific methodologies. Devised standard procedures for the evaluation and validation of prebiotic ingredients will boost confidence among the scientific community, approval of regulators, and acceptance from consumers on prebiotics and functional food science.     

Evaluation of Photoshop software potential for food colorimetry

This paper presents a simple method that shows how digital imaging and software analysis can be combined for color measurement. The results showed that L^∗, a^∗ and b^∗ values from Hunter colorimeter and the digital imaging method had appropriate correlation with R² of greater than 0.98, however color values obtained from digital imaging method can be used only to monitor the trend of color changes and relative comparison and there is a noticeable difference between L^∗, a^∗ and b^∗ from digital imaging and values of Hunterlab colorimeter. By using equations presented in this paper, L^∗, a^∗ and b^∗ values obtained from digital imaging method can be successfully converted to Hunterlab color values. Changes in color of Mazafati date during ripening by hot acetic acid solution were monitored by use of this method. L^∗, a^∗, and b^∗ values of the samples decreased during ripening.