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Abstract The kinetics of methane hydrate decomposition was studied using a semibatch stirred-tank reactor. The decomposition was accomplished by reducing the pressure on a hydrate slurry in water to a value below the three-phase equilibrium pressure at the reactor temperature. The data were obtained at temperatures from 274 to 283 K and pressures from 0.17 to 6.97 MPa. The stirring rates were high enough to eliminate mass-transfer effects. Analysis of the data indicated that the decomposition rate was proportional to the particle surface area and to the difference in the fugacity of methane at the equilibrium pressure and the decomposition pressure. The proportionality constant showed an Arrhenius temperature dependence. An estimate of the hydrate particle diameters in the experiments permitted the development of an intrinsic model for the kinetics of hydrate decomposition.

Photoexcitation and charge carrier thermalization inside semiconductor photocatalysts are two important steps in solar fuel production. Here, photoexcitation and charge carrier thermalization in a silicon wafer are for the first time probed by a novel, yet simple and user-friendly Attenuated Total Reflectance Infrared spectroscopy (ATR-IR) system.

The South is likely to suffer more from climate change than the North due to its already vulnerable situation and lack of the necessary resources to adapt to change. But do the interests of men and of women differ as regards climate change and does this have a South-North dimension? This paper attempts to establish whether gender issues need to be addressed in the climate change debate. Towards this goal, a number of different issues within the climate change debate, in particular the instruments proposed, are analysed. These include responsibility for emission of greenhouse gases (GHGs), studies on vulnerability to the effects of climate change, mitigation of emissions, capacity building for participation in flexible mechanisms and adaptation to climate change. We conclude that while there are many gender angles related to the climate change convention and the instruments therein, some are more strategic than others. There is little to be gained by looking at the responsibility for emissions on a gendered basis. But in mitigation activities, Clean Development Mechanism (CDM), capacity building, technology transfer, vulnerability studies and projects for adaptation, the poor, the majority of who are women, should be targeted and active participants in decision-making.

A sudden and sharp rise in the C-14 content of the atmosphere, which occurred between ca. 850 and 760 calendar yr BC (ca. 2750-2450 BP on the radiocarbon time-scale), was contemporaneous with an abrupt climate change. In northwest Europe (as indicated by palaeoecological and geological evidence) climate changed from relatively warm and continental to oceanic. As a consequence, the ground-water table rose considerably in certain low-lying areas in The Netherlands. Archaeological and palaeoecological evidence for the abandonment of such areas in the northern Netherlands is interpreted as the effect of a rise of the water table and the extension of fens and bogs. Contraction of population and finally migration from these low-lying areas, which had become marginal for occupation, and the earliest colonisation by farming communities of the newly emerged salt marshes in the northern Netherlands around 2550 BP, is interpreted as the consequence of loss of cultivated land. Thermic contraction of ocean water and/or decreased velocity and pressure on the coast by the Gulf Stream may have caused a fall in relative sea-level rise and the emergence of these salt marshes. Evidence for a synchronous climatic change elsewhere in Europe and on other continents around 2650 BP is presented. Temporary aridity in tropical regions and a reduced transport of warmth to the temperate climate regions by atmospheric and/or oceanic circulation systems could explain the observed changes. As yet there is no clear explanation for this climate change and the contemporaneous increase of C-14 in the atmosphere. The strategy of C-14 wiggle-match dating can play an important role in the precise dating of organic deposits, and can be used to establish possible relationships between changing C-14 production in the atmosphere, climate change, and the impact of such changes on hydrology, vegetation, and human communities.

Abstract Thermal energy storage (TES) systems are growing to a relevant role in solar cooling applications. Hence, high energy density is a desirable property of the TES system. Phase change materials (PCM) helps to increase this characteristic. A high temperature pilot plant able to test different types of TES systems and materials was designed and built at the University of Lleida (Spain). This pilot plant is composed mainly of three parts: heating system, cooling system, and different storage tanks. Two identical storage tanks based on the shell-and-tubes heat exchanger, one of them including 196 squared fins in the bundle of the tubes and the other without, were experimentally tested. Hydroquinone was selected as the storage material, having a latent heat of 205 kJ/kg and a phase change temperature between 168 and 173 °C. The aim of this paper is to test experimentally, and compare the average effectiveness of the TES systems analyzed using PCM for solar cooling and refrigeration applications. It was found out that for the same tank configurations (shell-and-tubes) even changing drastically the dimensions of the tank or the number and the diameter of the tubes, the average effectiveness curve proposed in the literature fits well with the results showed here.

The presented article will describe an 'effect-cause' model for the purpose of simulating the energy consumption of DC fed light rail vehicles. The model will assess the advantages of hybrid vehicles in terms of energy consumption, network power and voltage variations, line current and losses; and will help sizing and designing a supercapacitor based energy storage system (ESS) for both on-board, and stationary applications. The proposed modeling needs to allow the ESS sizing according to the objective that needs to be achieved, being braking energy recovery, voltage drop compensation and peak power shaving the most common goals of ESS use in hybrid vehicles. The needed power and energy levels will vary in function of the vehicle features and the driving cycle followed. This all can be determined by the quasi-static simulation tool to ease the design process. Another objective of the modeling tool is to evaluate the behaviour of the vehicle power flow controller, which manages the power from/to the ESS in function of the state of several variables.

It is well known that the efficiency of PV modules decreases with increasing module temperatures. Many studies have paid attention to the development and validation of heuristic models to calculate the PV module temperature in higher latitudes, however only a few focus on the thermal behaviour of PV modules in tropical regions of the world, where constantly high temperatures prevail. Also, little is known about the effect of including wind speed in these thermal models. This study evaluates three of such models - one that excludes wind, and two others including the wind influence - using hourly data for two tropical locations. Results show that the average hourly wind speeds in Singapore and Jayapura (Indonesia) are low and therefore the influence of the wind on the PV module temperature is minor. The three evaluated models produce about the same results with RMSE between 1.5-3.8 °C during daytime, which corresponds to a deviation in power output in the range of 0.3-1.6 %, depending on the PV module technology.

Saving energy in greenhouses is an important issue for growers. Here, we present a method to minimize the total energy that is required to heat and cool a greenhouse. Using this method, the grower can define bounds for temperature, humidity, CO2 concentration, and the maximum amount of CO2 available. Given these settings, optimal control techniques can be used to minimize energy input. To do this, an existing greenhouse climate model for temperature and humidity was expanded to include a CO2 balance. Heating, cooling, the amount of natural ventilation, and the injection of industrial CO2 were used as control variables.Standard optimization settings were defined in order to compare the grower's strategy with the optimal solution. This optimization resulted in a theoretical 47% reduction in heating, 15% reduction in cooling, and 10% reduction in CO2 injection for the year 2012. The optimal control does not need to maintain a minimum pipe temperature, in contrast to current practice. When the minimum pipe temperature strategy of the grower was implemented, heating and CO2 were reduced by 28% and 10% respectively.We also analyzed the effect of different bounds on optimal energy input. We found that as more freedom is given to the climate variables, the higher the potential energy savings. However, in practice the grower is in charge of defining the bounds. Thus, the potential energy savings critically depend on the choice of these bounds. This effect was analyzed by varying the bounds. However, because the effect can be demonstrated to the grower, the outcome has value to the grower with respect to decision making, an option that is not currently available in practice today.