Experimental investigation on a dual-mode thermochemical sorption energy storage system

A dual-mode seasonal solar thermochemical sorption energy storage system using working pair of expanded graphite/SrCl2-NH3 was constructed and investigated. Solar thermal energy is transformed into chemical bonds in summer, and the stored energy is released in the form of chemical reaction heat in winter. Two working modes are performed to produce heat with expected temperature according to the different ambient temperatures in winter. The direct heating supply mode is adopted at a relatively high ambient temperature. The effective energy storage density is higher than 700kJ/kg and the corresponding system COP is 0.41 when the heat output temperature and ambient temperature are 35oC and 15oC, respectively. The specific heating power increases with the decrease of heat output temperature for a given ambient temperature. The temperature-lift heating supply mode is adopted to upgrade the heat output temperature at a low ambient temperature below 0oC. It can produce heat with a temperature above 70 oC although the ambient temperature is as low as -15oC. It is desirable to further improve the system performance using low mass ratio and high global conversion. Experimental results showed the advanced dual-mode thermochemical sorption energy storage technology is feasible and effective for seasonal solar thermal energy storage

Ground-state properties of tubelike flexible polymers

In this work we investigate structural properties of native states of a simple model for short flexible homopolymers, where the steric influence of monomeric side chains is effectively introduced by a thickness constraint. This geometric constraint is implemented through the concept of the global radius of curvature and affects the conformational topology of ground-state structures. A systematic analysis allows for a thickness-dependent classification of the dominant ground-state topologies. It turns out that helical structures, strands, rings, and coils are natural, intrinsic geometries of such tubelike objects

An analytical model of a clamped sandwich beam under low-impulse mass impact

An analytical model is developed to examine a low impulsive projectile impact on a fully clamped sandwich beams by considering the coupled responses of the core and the face sheets. Firstly, based on the dynamic properties of foam cores, the sandwich beam is modeled as two rigid perfectly-plastic beams connected by rigid perfectly-plastic springs. Different from the previous sandwich beam model, the transverse compression and bending effects of the foam core are considered in the whole deformation process. Based on this model, different coupling mechanism of sandwich beams are constructed so that an analytical solution considering small deformation is derived. The coupled dynamic responses of sandwich beams with different core strengths are investigated. The results indicate that this model improves the prediction accuracy of the responses of the sandwich beams, and is available for the situation when the sandwich beam undergoes moderate global deformation

The effect of size and composition on structural transitions in monometallic nanoparticles

Predicting the morphological stability of nanoparticles is an essential step towards the accurate modelling of their chemophysical properties. Here we investigate solid–solid transitions in monometallic clusters of 0.5–2.0 nm diameter at finite temperatures and we report the complex dependence of the rearrangement mechanism on the nanoparticle’s composition and size. The concerted Lipscomb’s Diamond-Square-Diamond mechanisms which connects the decahedral or the cuboctahedral to the icosahedral basins, take place only below a material dependent critical size above which surface diffusion prevails and leads to low-symmetry and defected shapes still belonging to the initial basin

Precision Measurement of the Proton Flux in Primary Cosmic Rays from Rigidity 1 GV to 1.8 TV with the Alpha Magnetic Spectrometer on the International Space Station

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.</p

Derivation of Land Surface Albedo at High Resolution by Combining HJ-1A/B Reflectance Observations with MODIS BRDF Products

Land surface albedo is an essential parameter for monitoring global/regional climate and land surface energy balance. Although many studies have been conducted on global or regional land surface albedo using various remote sensing data over the past few decades, land surface albedo product with a high spatio-temporal resolution is currently very scarce. This paper proposes a method for deriving land surface albedo with a high spatio-temporal resolution (space: 30 m and time: 2-4 days). The proposed method works by combining the land surface reflectance data at 30 m spatial resolution obtained from the charge-coupled devices in the Huanjing-1A and -1B (HJ-1A/B) satellites with the Moderate Resolution Imaging Spectroradiometer (MODIS) land surface bidirectional reflectance distribution function (BRDF) parameters product (MCD43A1), which is at a spatial resolution of 500 m. First, the land surface BRDF parameters for HJ-1A/B land surface reflectance with a spatial-temporal resolutions of 30 m and 2-4 day are calculated on the basis of the prior knowledge from the MODIS BRDF product; then, the calculated high resolution BRDF parameters are integrated over the illuminating/viewing hemisphere to produce the white-and black-sky albedos at 30 m resolution. These results form the basis for the final land surface albedo derivation by accounting for the proportion of direct and diffuse solar radiation arriving at the ground. The albedo retrieved by this novel method is compared with MODIS land surface albedo products, as well as with ground measurements. The results show that the derived land surface albedo during the growing season of 2012 generally achieved a mean absolute accuracy of +/- 0.044, and a root mean square error of 0.039, confirming the effectiveness of the newly proposed method

Renewable energy in Kenya: Resource potential and status of exploitation

This paper presents an assessment of renewable energy resource potential and the current status of exploitation in Kenya. As an importer of petroleum fuels, Kenya spends a substantial amount of foreign reserves to import oil. The oil import bill in 2008 consumed 55% of the country's foreign exchange earnings from exports. On the other hand, there is a high dependence on wood biomass energy, leading to an imbalance in its supply and demand. This has exerted considerable pressure on the remaining forest and vegetation stocks, thereby accelerating the processes of land degradation. Moreover, despite the abundance of potential and a strong growth in demand for electricity, the country faces constraints in satisfying electricity demand. At the national level, only 18% of the households have access to grid electricity. The access is much lower in rural areas where only 4% of the households have grid electricity. Kenya has a liberalized energy sector and has made significant progress in the recent past in formulation of renewable energy policies. What is more, Kenya's electricity power mix is among the most sustainable in the world, with 80% of electricity coming from renewable sources. However, a substantial proportion of renewable energy resources are unexploited. Of the potential renewable sources, Kenya has harnessed only about 30% of its hydropower sources, approximately 4% of the potential geothermal resources and much smaller proportions of proven wind and solar power potentials. Furthermore, a large potential exists for the development of biomass based energy such as biogas, biodiesel and power generation form baggasse. The strong growth in energy demand provides excellent opportunities for private investors to invest in renewable energy power generation.Renewable energy Review Kenya Africa

Performance study of a consolidated manganese chloride-expanded graphite compound for sorption deep-freezing processes

A consolidated composite sorbent made from manganese chloride and expanded graphite was produced for sorption deep-freezing processes and used for cold production at a temperature as low as -35 °C. Experimental results showed that the addition of a porous graphite matrix can prevent the agglomeration and the attenuation of sorption capacity of reactive salt. The composite sorbent could incorporate 0.537 kg of ammonia per kg of reactive salt and the average specific cooling power (SCP) obtained varied between 200 W kg-1 and 700 W kg-1 when the evaporation temperature ranged from -35 °C to 0 °C. The analysis of the data suggested that the heat transfer characteristic in the composite sorbent was strongly influenced by chemical reaction and the conversion rate was very sensitive to the constraint temperatures. The SCP and coefficient of performance (COP) of a simple sorption deep-freezing system were 350 W kg-1 and 0.34, respectively, at the generation temperature of 180 °C, the heat sink temperature of 25 °C and the evaporation temperature of -30 °C.Sorption Deep-freezing Composite sorbent Heat transfer Sorption characteristics

Ab initio study on the adsorption of oxygen on Co(111) and its subsurface incorporation

The adsorption of oxygen on Co(111) and its subsurface incorporation is studied by density-functional theory calculations. Calculated adsorption energies, geometries and electronic structures are discussed in comparison with that of O/Co(0001). The results indicate that oxygen adsorption in hcp-hollow sites on Co(111) are the most preferred in a coverage range of 0.11–1.0 ML, and the surface electronic structure modifications for O/Co(111) points to a consistent picture of Hammer-Nørskov model. In addition, present calculations show that oxygen atoms incorporate into the first subsurface layer forming an O-Co-O trilayer on top Co(111), which possibly undergoes conversion to cobalt oxides. The behaviors of oxygen on Co(111) are similar to that of O/Co(0001)