Upper limits to absorption enhancement in thick solar cells using diffraction gratings

The application of diffraction gratings to solar cells is a promising approach to superseding the light trapping limits of conventional Lambertian structures. In this paper a mathematical formalism is derived for calculating the absorption that can be expected in a solar cell equipped with a diffraction grating, which can be applied to any lattice geometry and grating profile. Furthermore, the formalism is used to calculate the upper limit of total absorption that can theoretically be achieved using a diffraction grating. The derived formalism and limits are valid when the solar cell thickness is greater than the coherence length of the illuminating solar spectrum. Comparison is made to the upper limit achievable using an angularly selective Rugate filter, which is also calculated. Both limits are found to be considerably higher than the Lambertian limit within the range of sunlight concentration factors practically employed in photovoltaic systems (1–1000×). The upper limit of absorption using the diffraction grating is shown to be equal to the thermodynamic limit for all absorbances and concentration factors. The limit for the Rugate filter is generally lower, but tends to the thermodynamic limit for lower cell absorbances. Copyright © 2011 John Wiley & Sons, Ltd.     

Galactose derivative immobilized glow discharge processed polyethersulfone membranes maintain the liver cell metabolic activity

New strategies aimed to surface modification of polymeric membranes are crucial to optimise cell-biomaterial interactions in vivo and in vitro biohybrid systems. In this paper, we investigated the surface modification of Polyethersulfone (PES) membranes by plasma polymerisation of acrylic acid monomers (PES-pdAA) and by immobilization of galactonic acid through a hydrophilic "spacer arm" molecule (PES-pdAA-SA-GAL). The modification steps were characterised by high resolution X-ray photoelectron spectroscopy. The performance of modified and unmodified membranes was evaluated by assessing the expression of liver specific biotransformation functions of pig and human hepatocytes. Human liver cells cultured on PES-pdAA-SA-GAL membranes displayed an enhanced albumin production, urea synthesis and protein secretion for 24 days of culture. The immobilisation of galactose derivative units on the membrane allowed specific interactions with hepatocytes biomimicking the cellular microenvironment and produced an improvement of the long-term maintenance and differentiation of human hepatocytes.     

Cooperating CoScheduling: A Coscheduling Proposal Aimed at Non-Dedicated Heterogeneous NOWs

Implicit coscheduling techniques applied to non-dedicated homogeneous Networks Of Workstations （NOWs） have shown they can perform well when many local users compete with a single parallel job. Implicit coscheduling deals with minimizing the communication waiting time of parallel processes by identifying the processes in need of coscheduling through gathering and analyzing implicit runtime information, basically communication events. Unfortunately, implicit coscheduling techniques do not guarantee the performance of local and parallel jobs, when the number of parallel jobs competing against each other is increased. Thus, a low efficiency use of the idle computational resources is achieved.
In order to solve these problems, a new technique, named Cooperating CoScheduling （CCS）, is presented in this work. Unlike traditional implicit coscheduling techniques, under CCS, each node takes its scheduling decisions from the occurrence of local events, basically communication, memory, Input/Output and CPU, together with foreign events received from cooperating nodes. This allows CCS to provide a social contract based on reserving a percentage of CPU and memory resources to ensure the progress of parallel jobs without disturbing the local users, while coscheduling of communicating tasks is ensured. Besides, the CCS algorithm uses status information from the cooperating nodes to balance the resources across the cluster when necessary. Experimental results in a non-dedicated heterogeneous NOW reveal that CCS allows the idle resources to be exploited efficiently, thus obtaining a satisfactory speedup and provoking an overhead that is imperceptible to the local user.     

Correction to: A model of checkpoint behavior for applications that have I/O

The Journal of Supercomputing -     

Some Results of the EUCLIDES Photovoltaic Concentrator Prototype

A photovoltaic concentration array prototype of 60·4 m² of aperture is described. It uses reflecting linear optics kept in focus by means of horizontal single-axis tracking. All its cells are connected in series so as to avoid laborious field interconnection work. This prototype is being followed by a demonstration plant of 3479 m² of aperture. The prototype performances are presented and fitted to a model that allows their prediction under conditions different from those of measurement. On the basis of this model the demonstration plant performances are anticipated. A cost analysis is presented based on our best estimates after the erection of the present prototype. It shows that the cost of the electricity, in medium or large size installation, should be strongly reduced with respect to that produced by flat modules. © 1997 John Wiley & Sons, Ltd.     

A metallic intermediate band high efficiency solar cell

The theory of a novel type of solar cell is presented that contains a base made of a semiconductor with a metal‐like intermediate band (IB). The behavior of the IB and of the entire cell is studied taking into account photon recycling, that is, the emission of luminescent photons that may be subsequently absorbed. The results show that, in ideal conditions, this device is more efficient than the best two‐junction series‐connected tandem cells. This advantage might be maintained for less ideal cases. Although the material needed to achieve this device is yet unknown, some hints are given in the paper concerning its synthesis. Copyright © 2001 John Wiley & Sons, Ltd.     

The MONOCHESS project: Goals and results to date

The MONOCHESS consortium, formed in the framework of the JOULE programme of the European Union, is presented. Its goal is the cooperation between laboratories and companies for the development of cheaper monocrystalline silicon 1-sun and concentration cells. Objectives and key results already achieved are described.