Possible future scenarios for atmospheric concentration of greenhouse gases: A simplified thermodynamic approach

Most of the increase in concentrations of greenhouse gases in the Earth's atmosphere is mainly due to anthropogenic activities. This is particularly significant in the case of CO₂. The atmospheric concentration of CO₂ has systematically increased since the Industrial Revolution (260 ppm), with a remarkable raise after the 1970s until the present day (380 ppm). If this increasing tendency is maintained, the last report of the Intergovernmental Panel on Climate Change (IPCC) estimates that, for the year 2100, the CO₂ concentration can augment up to approximately 675 ppm. In this work it is assumed that the quantity of anthropogenic greenhouse gases emitted to the Earth's atmosphere is proportional to the quantity of heat rejected to the environment by internal combustion heat engines. It is also assumed that this increasing tendency of CO₂ due to men's activity stems from a mode of energy production mainly based on a maximum-power output paradigm. With these hypotheses, a thermoeconomic optimization of a thermal engine model under two regimes of performance: the maximum-power regime and the so-called ecological function criterion is presented. This last regime consists in maximizing a function that represents a good compromise between high power output and low entropy production. It is showed that, under maximum ecological conditions, the emissions of thermal energy to the environment are reduced approximately up to 50%. Thus working under this mode of performance the slope of the curves of CO₂ concentration, for instance, drastically diminishes. A simple qualitative criterion to design ecological taxes is also suggested.     

A theoretical analysis of the capture of greenhouse gases by single water droplet at atmospheric and elevated pressures

Gas absorption by droplets is an important route to reduce greenhouse gas emissions, especially for carbon dioxide. To recognize the fundamental absorption processes of greenhouse gases by single droplets, the mass transport phenomena of greenhouse gas uptake by a quiescent water droplet at atmospheric and elevated pressures are analyzed theoretically and four common greenhouse gases of CO₂, N₂O, CH₄ and O₃ are taken into consideration. On account of piecewise function encountered at the droplet surface, it is impossible to obtain a fully analytical solution for describing the mass transfer process. Instead, a semi-analytical method is developed to predict the mass diffusion between the gas phase and the liquid phase. The obtained results indicate that, by virtue of the four greenhouse gases characterized by low mass diffusion number, the entire mass transfer is controlled by the liquid phase. A unified formula has been successfully established to aid in estimating the dimensionless solute uptake process and the dimensionless aqueous diffusion time of 0.45 is sufficiently long the implement the absorption process. For the ambient temperature and pressure in the ranges of 280–350 K and 1–20 atm, respectively, it is found that increasing the two parameters will intensify the solute absorption amount significantly and the absorption process can be accelerated by increasing temperature.     

Degradation of [D-Leu]-Microcystin-LR by solar heterogeneous photocatalysis (TiO2)

The present study investigates the use of solar heterogeneous photocatalysis (TiO₂) for the destruction of [D-Leu]-Microcystin-LR, powerful toxin of widespread occurrence within cyanobacteria blooms. We extracted [D-Leu]-Microcystin-LR from a culture of Microcystis spp. and used a flat plate glass reactor coated with TiO₂ (Degussa, P25) for the degradation studies. The irradiance was measured during the experiments with the aid of a spectroradiometer. After the degradation experiments, toxin concentrations were determined by HPLC and mineralization by TOC analyses. Acute and chronic toxicities were quantified using mice and phosphatase inhibition in vitro assays, respectively. According to the performed experiments, 150 min were necessary to reduce the toxin concentration to the WHO’s guideline for drinking water (from 10 to 1 μg L^?1) and to mineralize 90% of the initial carbon content. Another important finding is that solar heterogeneous photocatalysis was a destructive process indeed, not only for the toxin, but also for the other extract components and degradation products generated. Moreover, toxicity tests using mice have shown that the acute effect caused by the initial sample was removed. However, tests using the phosphatase enzyme indicated that it may be formed products capable of inducing chronic effects on mammals. The performed experiments indicate the feasibility of using solar heterogeneous photocatalysis for treating contaminated water with [D-Leu]-Microcystin-LR, not only due to its destruction, but also to the significant removal of organic matter and acute toxicity that can be achieved.     

Potential for large-scale solar collector system to offset carbon-based heating in the Ontario greenhouse sector

In the Ontario greenhouse sector the misalignment of available solar radiation during the summer months and large heating demand during the winter months makes solar thermal collector systems an unviable option without some form of seasonal energy storage. Information obtained from Ontario greenhouse operators has shown that over 20% of annual natural gas usage occurs during the summer months for greenhouse pre-heating prior to sunrise. A transient model of the greenhouse microclimate and indoor conditioning systems is carried out using TRNSYS software and validated with actual natural gas usage data. A large-scale solar thermal collector system is then incorporated and found to reduce the annual heating energy demand by approximately 35%. The inclusion of the collector system correlates to a reduction of about 120 tonnes of CO₂ equivalent emissions per acre of greenhouse per year. System payback period is discussed considering the benefits of a future Ontario carbon tax.     

Pilot-plant treatment of olive mill wastewater (OMW) by solar TiO2 photocatalysis and solar photo-Fenton

Olive mill wastewater (OMW), a highly polluted wastewater from the olive oil industry, was treated by solar photocatalysis and solar photo-Fenton. Among the tested systems the application of titanium dioxide alone was not successful. The addition of peroxydisulphate as an electron acceptor had only limited effect on degradation performance and led to high salt concentrations (30 g/l sulphate generated) and a pH value near zero. The photo-Fenton method successfully removed up to 85% COD and up to 100% of phenol index of OMW with different initial concentrations and from different sources. Two solar photocatalytic pilot-plant reactors were used; one of conventional CPC type and an open non-concentrating Falling Film Reactor. The latter, newly designed reactor worked properly and yielded comparable results to the CPC in terms of degradation rate referred to incident UV radiation energy per solution volume. The suspended solids in the OMW hinder light from entering the reactor. Therefore, flocculation induced by a commercial flocculation agent was successfully applied to remove suspended solids. Application of this pre-treatment led to considerable increase of degradation rates and decrease of hydrogen peroxide consumption.     

On the potential change in wind power over the US due to increases of atmospheric greenhouse gases

Wind power (WP) is a likely source of renewable energy to reduce fossil CO₂ atmospheric emissions. However, WP availability might be affected by climate changes induced by such emissions. In this study a refined regional climate model, appropriate for resolving near-surface flows, was used to generate WP climatologies for the US consistent with present and mid-21st century enhanced atmospheric CO₂ level. In both cases the regional climate simulation was forced by lateral boundary conditions based on simulations of the Hadley Centre general circulation model. Simulated present WP showed reasonable general agreement with patterns observed in most locations. In most of the US the enhanced CO₂ simulation showed a trend of decreased daily average WP availability in the range of 0–30%. However, in limited areas in the southern and northwestern US, an increase in WP, peaking at 30%, was simulated. Under the enhanced CO₂ climate scenario, the present relatively high WP availability in northern Texas and western Oklahoma, as well as in the northwest US, are almost unaffected. A decline in WP is simulated in the north–central US and the western mountainous region.     

现代农业技术--太阳能温室设施农业

＠吴静怡＠王如竹一、太阳能温室设施农业及其关键技术农作物的生长发育，一方面决定于作物本身的遗传特性，另一方面决定于外界环境条件。太阳能温室设施农业是在不适宜露地栽培农作物的季节或地区，利用特定的太阳能温室设施创造出适于农作物生长发育的人工小气候环境，从而达...     

东北型节能日光温室--辽沈Ⅰ型温室地下热交换系统试验研究

温室的地下热交换系统是为提高太阳能的利用率,达到节能增温的目的而研究设置的,本文运用传热学的基本理论,通过对日光温室地下热交换系统土壤温度场的分析。提出了日光温室地下热交换系统的设计原理,地下热交换系统的设计的一般方法,并结合测试结果进行分析。     

Considerations for the calculation of greenhouse gas reduction by photovoltaic solar energy

A CO₂ comprehensive balance within the life-cycle of a photovoltaic energy system requires careful examination of the CO₂ sinks and sources at the locations and under the conditions of production of each component, during transport, installation and operation, as well as at the site of recycling. Calculations of the possible effect on CO₂ reduction by PV energy systems may be incorrect if system borders are not set wide enough and remain on a national level, as can be found in the literature. For the examples of Brazil and Germany, the effective CO₂ reductions have been derived, also considering possible interchange scenarios for production and operation of the PV systems considering the carbon dioxide intensity of the local electricity grids. In the case of Brazil also off-grid applications and the substitution of diesel generating sets by photovoltaics are examined: CO₂ reduction may reach 26,805 kg/kW_p in that case. Doing these calculations, the compositions of the local grids and their CO₂ intensity at the time of PV grid injection have to be taken into account. Also possible changes of the generation fuel mix in the future have to be considered: During the operation time of a PV system, different kinds of power plants could be installed that might change the CO₂ intensity of the grid. In the future also advanced technologies such as thin films have to be considered.     

温室技术在太阳热水器的应用

利用物体表面对太阳辐照的表面积累效廊设计，多霞温摩，使受光面积远超过太阳能热水器的集热面积，大幅度地提高了集热器的环境温度，减小了太阳热水器与环境的温差，提高了热水器的使用效果。此方法代替了现已应用的真空技术、蜂窝技术等抑制太阳能集热板（管）顶部散热的方法。提出了利用“矮墙多重温室法”产生廉价热水的技术方案。     

日光温室节能墙体的选择

为探讨日光温室墙体对室内热环境的影响，对两组温室室内外温度进行了测试对比，并针对目前常见的单一材料墙体及异质复合墙体，在厚度相同的情况下进行了传热分析。测试结果显示，异质复合墙体温室内的夜间温度比单一材料墙体温室夜间温度高3℃左右。在考虑墙体的蓄热和传热情况下，温室墙体以内部砖外部聚苯板异质复合墙体为宜。     

德国大型太阳能装置在工业中的应用

太阳能作为一种开发潜力巨大的可再生能源,早已引起世界各国的广泛关注。德国是世界上太阳能利用市场规模最大的国家。据德国太阳能工业协会2009年底发表的统计数字,截至2008年底,德国共有约200家太阳能企业,约7.8万名从业人员,全年销售额达110亿欧元,共有170万个     

An assessment of large-scale solar hydrogen production in Canada

This study presents an assessment on the hydrogen production using a central receiver system coupled to either an electrolyser plant or a thermochemical plant. Systems which are capable of producing 10⁵ and 10⁶ GJ per year thermal energy or about half of this as hydrogen were developed at four locations in Canada: Fort McMurray, London, Moncton and Victoria. For central receiver systems of 10⁵ and 10⁶ GJ per year thermal energy capacity, heliostat fields arranged to the north of the receiver and tower were developed. A code consisting of optical and thermodynamic performance models was developed to simulate the system. For chemical plants, both electrolysis and thermochemical, codes were developed to simulate their thermodynamic performances. Cost models were developed for each subsystem based on the data published in the literature. Two scenarios were used for the heliostat prices: the first with a limited time and production capacity and the second with a quasi-optimized production capacity and production time. Estimates for the costs of hydrogen were then developed. The results indicated that levelized thermal energy costs ranged from $ 17 to $ 55 per GJ, electricity costs ranged from $ 0.2 to $ 0.5 per kWh and hydrogen costs from $ 57 to $ 157 per GJ.     

Parameter optimisation of a greenhouse solar heating and climatisation system

A solar heating and climatisation system based on selective absorption of solar energy by a selective collector was developed at the I.A.V. (Morocco). The experimental study shows that the performance of this system depends on several parameters: the nature of the caloporter fluid, the flow of the fluid circulation, the collector's surface area and the circulation mode (opened circulation or closed circulation).The system was tested inside a greenhouse which contained a strawberry crop. A clear improvement of the performance has been achieved for an open circulation with appropriate working parameters. The experimental results showed a precocity of 13 days of the strawberry crop in comparison to a standard greenhouse.     

Transient analysis of a winter greenhouse integrated with solar still

The present work deals with a simple transient analysis of a winter greenhouse integrated with a solar still. Explicit expressions for the temperatures of still cover, brine (basin-water), basin of the still/roof of the greenhouse, greenhouse air, plants and floor of the greenhouse have been developed so as to study the transient thermal performance of the system. The effect of several parameters, namely relative humidity, ventilation/infiltration, heat capacity of basin water and plants, etc. has been incorporated in the analysis. On the basis of numerical calculations, some interesting conclusions have been made.     

Olympic Games promote the reduction in emissions of greenhouse gases in Beijing

Global climate change is one of the most serious global environmental problems faced by humankind at present. Serious attention should be paid and precautions should be taken before disasters occur. The amount of CO₂ emissions in China has increased during the past few years and the Chinese government and people have attached great importance to this phenomenon and treated it seriously. With the instruction of scientific development viewpoint, Beijing has made significant progress in emissions reduction through technological innovation, industrial structure adjustment, promoting energy efficiency and utilization of renewable energy, and absorption of CO₂ using forest and wetland, since bidding for Olympic Games. At the same time, energy conservation and emissions reduction measures taken in the construction of Beijing Olympic stadiums just incarnate the Beijing Green Olympics.     

Investigation of a new solar greenhouse drying system for peppers

Solar drying is the oldest preservation technique of agricultural products using several types of solar crop dryers based mostly on solar energy, which is abundant, renewable and sustainable. This study aimed to modeling a new solar greenhouse drying system (SGDS) for the drying of red peppers. The proposed mixed-mode (SGDS) consists of two main parts, namely a flat plate solar air collector and an experimental greenhouse. A mathematical model is developed using the TRNSYS simulation program to predict the change in the drying kinetics during the drying process under our proposed (SGDS). The experimental part consisted in testing the solar air collector to investigate its performance. The test showed that this solar air collector has a good performance; its efficiency varies between 0, 5 and 0, 65. The model was validated with the observed data and showed good agreement with experimental values. The influence of the area of the product to be dried, airflow rate and collector area, on moisture content changes, air temperature and humidity inside the greenhouse was studied. For the case study of this SGDS, the results obtained from simulation showed that the optimum values of area of the product to be dried, the exhaust airflow rate and the collector area were found to be 40 m², 250 kg/h and 2 m², respectively.     

Degradation of lincomycin in aqueous medium: Coupling of solar photocatalysis and membrane separation

The photocatalytic oxidation of a common antibiotic, the lincomycin was carried out in aqueous suspensions of polycrystalline TiO₂ Degussa P25 irradiated by sunlight. In order to improve the performance of the lincomycin degradation a hybrid system consisting of a solar photoreactor with the photocatalyst in suspension coupled with a membrane module, used to confine both photocatalyst and pollutants in the reaction environment, was tested.A preliminary study was carried out in order to determine some kinetics parameters of the drug photodegradation. The influence of initial substrate concentration on the lincomycin photooxidation rate was investigated. The photooxidation rate follows a pseudo-first order kinetics with respect to the lincomycin concentration under the used experimental conditions. The presence of the membrane reactor allows the catalyst separation and to operate in continuous mode as the membranes rejection for lincomycin and its oxidation products was quite high.     

The impracticability of large-scale generation of hydrogen from water photolysis by utilization of solar radiation

The possibility of using solar radiation for the generation of hydrogen by the photolysis of water is discussed in relation to requirements of large-scale generation which would be needed in a hydrogen economy or in coal gasification. Although the point is conceded that solar energy is, for all practical purposes, an infinite source, the conclusion is that solar radiation is not available on the surface of the plant in energy densities which would allow large-scale hydrogen generation without overwhelming technical and economic difficulties. The particular restriction lies in the large ground areas required for generation of reasonably large quantities of hydrogen, since the volume of hydrogen at atmospheric pressure which can be generated per square metre of surface is only of the order of 0.2–0.4 m³/day.