Primary optics for efficient high-brightness LED color mixing

In SSL general illumination, there is a clear trend to high flux packages with higher efficiency and higher CRI addressed with the use of multiple color chips and phosphors. However, such light sources require the optics provide color mixing, both in the near-field and far-field. This design problem is specially challenging for collimated luminaries, in which diffusers (which dramatically reduce the brightness) cannot be applied without enlarging the exit aperture too much. In this work we present first injection molded prototypes of a novel primary shell-shaped optics that have microlenses on both sides to provide Köhler integration. This shell is design so when it is placed on top of an inhomogeneous multichip Lambertian LED, creates a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is located in the same position with only small increment of the size (about 10-20%, so the average brightness is similar to the brightness of the source). This shell-mixer device is very versatile and permits now to use a lens or a reflector secondary optics to collimate the light as desired, without color separation effects. Experimental measurements have shown optical efficiency of the shell of 95%, and highly homogeneous angular intensity distribution of collimated beams, in good agreement with the ray-tracing simulations.

Inhomogeneous source uniformization using a shell mixer Köhler integrator

High flux and high CRI may be achieved by combining different chips and/or phosphors. This, however, results in inhomogeneous sources that, when combined with collimating optics, typically produce patterns with undesired artifacts. These may be a combination of spatial, angular or color non-uniformities. In order to avoid these effects, there is a need to mix the light source, both spatially and angularly. Diffusers can achieve this effect, but they also increase the etendue (and reduce the brightness) of the resulting source, leading to optical systems of increased size and wider emission angles. The shell mixer is an optic comprised of many lenses on a shell covering the source. These lenses perform Kohler integration to mix the emitted light, both spatially and angularly. Placing it on top of a multi-chip Lambertian light source, the result is a highly homogeneous virtual source (i.e, spatially and angularly mixed), also Lambertian, which is located in the same position with essentially the same size (so the average brightness is not increased). This virtual light source can then be collimated using another optic, resulting in a homogeneous pattern without color separation. Experimental measurements have shown optical efficiency of the shell of 94%, and highly homogeneous angular intensity distribution of collimated beams, in good agreement with the ray-tracing simulations.

1000x shadow-free mirror-based Köhler concentrator

A new design for a photovoltaic concentrator, the most recent advance based on the Kohler concept, is presented. The system is mirror-based, and with geometry that guaranties a maximum sunlight collection area (without shadows, like those caused by secondary stages or receivers and heat-sinks in other mirror-based systems). Designed for a concentration of 1000x, this off axis system combines both good acceptance angle and good irradiance uniformity on the solar cell. The advanced performance features (concentration-acceptance products ?CAP- about 0.73 and affordable peak and average irradiances) are achieved through the combination of four reflective folds combined with four refractive surfaces, all of them free-form, performing Köhler integration 2 . In Köhler devices, the irradiance uniformity is not achieved through additional optical stages (TIR prisms), thus no complex/expensive elements to manufacture are required. The rim angle and geometry are such that the secondary stage and receivers are hidden below the primary mirrors, so maximum collection is assured. The entire system was designed to allow loose assembly/alignment tolerances (through high acceptance angle) and to be manufactured using already well-developed methods for mass production, with high potential for low cost. The optical surfaces for Köhler integration, although with a quite different optical behavior, have approximately the same dimensions and can be manufactured with the same techniques as the more traditional secondary optical elements used for concentration (typically plastic injection molding or glass molding).

Wide-angle, high-concentration photovoltaics to compete with flat plate systems

A novel photovoltaic concentrator enables highly uniform irradiance on a small number of efficient solar cells. The maximum electrical power of a photovoltaic (PV) energy installation depends on three factors: the available irradiance, the size of the systems collecting sunlight, and the rate at which the device transforms light into electricity (the conversion efficiency). Developers can maximize the irradiance by carefully selecting the site and orientation of the solar facility. But they can only expand their sunlight collection systems for standard flat plate PV devices by increasing the number of solar cells, at greater cost. Here, we consider the advantages of an alternative PV system that produces more energy without increasing the number of cells used (actually, reducing it), by improving the conversion rates.We also present a new device that may enhance the commercial viability of such technologies.

VentanaTM power train features and performance

Most CPV systems are based on Fresnel lenses. Among these, LPI-patented Fresnel-Köhler (FK) concentrator outstands owing to performance and practical reasons. The VentanaTM power train is the first off-the-shelf commercial product based on the FK and comprises both the primary (POE) lenses (a 36-units 1×1 m2 acrylic panel manufactured by EVONIK and 10×) and glass (or Savosil) secondary optics (SOE). This high concentration optical train (Cg=1,024×, ~250mm optical depth) fits with 5×5 mm2 (at least) solar cells. The optical train is the fruit of a 1-year development that has included design, modeling, prototyping and characterization, and through the process LPI had the opportunity to find out how well the actual performance correlates with models, but also learned practical aspects of a CPV system of this kind, some of which have very positive impact on system performance and reliability.

Performance of UV-enhanced PMMA fresnel lenses and impact on LCOE

Tiny increases in the transmittance of optical materials within a CPV module can have an important impact on the economy of a plant. This is certainly true in systems comprising multi-junction solar cells, whose high performance, based on a balanced photocurrent generation among the series-connected junctions, is very sensitive to spectrum variations. Every efficiency point gained causes not only an increase in the kilowatts hour produced, but a higher benefit on it, since the difference between electricity tariff and Levelized Cost of Electricity (LCOE) rises. This work studies the impact on the LCOE of a plant based on modules comprising PMMA lenses of two different types, standard UV blocking grade which is normally used for outdoor applications at high DNI climate and a specialty stabilized UV-enhanced transmittance acrylic (see Figure 1). Energy production will be compared for these two systems throughout the year at different sites to analyze when (season, time of the day) and where the usage of the enhanced PMMA is justified.

Field experiment of 800× off-axis XR-Köhler concentrator module on a carousel tracker

This paper presents the design and preliminary experimental results of a concentrator-type photovoltaic module based on a free-form off-axis 800×XR-Köhler concentrator. The off-axis XR-Köhler concentrator is one of the advanced concentrators that perform high concentration with a large acceptance angle and excellent irradiance uniformity on a solar cell. As a result of on-sun characterization of the unglazed single-cell unit test rig, the temperature-corrected DC module efficiency was 32.2% at 25 °C without an anti-reflective (AR) coating on the secondary optics, and the acceptance angle was more than ±1.0°. In addition, the non-corrected DC efficiency of an individual cell in a glazed 8-cell unit module mounted on a carousel tracking system was measured. The individual efficiency deviated in the range of 24.3-27.4%, owing to the mirror shape and alignment errors. The resultant series-connected efficiency was approximately 25% at direct normal irradiation (DNI) of 770 W/m2.

The influence of antiferroelectric compounds on helical pitch of orthoconic W-1000 mixture

The influence of six antiferroelectric compounds on the helical pitch of mixture W-1000, which was reported as long pitch orthoconic antiferroelectric liquid crystalline mixture, was checked by spectrophotometry and polarimetry methods. The electro-optical properties for the mixture with the longest pitch were measured. An improvement in electro-optical response due to the long pitch is reported. The novelty in electro-optical properties is the good symmetry response.

El fenómeno del dopaje desde la perspectiva de las Ciencias Sociales Odile

En este libro se recoge una selección de las comunicaciones presentadas en el IV Congreso Internacional ‘Deporte, Dopaje y Sociedad’ que se celebró en Madrid del 26 de febrero al 1 de marzo de 2014 y que fue organizado conjuntamente por la Universidad Politécnica de Madrid y la Agencia Española de Protección de la Salud en el Deporte. Los textos están escritos en español, francés e inglés y abordan el estudio del fenómeno del dopaje desde el ámbito especifico de las Ciencias Humanas y Sociales a través de disciplinas como Historia, Derecho, Sociología, Psicología, Economía, Ciencias de la Información y otras disciplinas relacionadas.

Targeting peptide nucleic acid (PNA) oligomers to mitochondria within cells by conjugation to lipophilic cations: implications for mitochondrial DNA replication, expression and disease

The selective manipulation of mitochondrial DNA (mtDNA) replication and expression within mammalian cells has proven difficult. One promising approach is to use peptide nucleic acid (PNA) oligomers, nucleic acid analogues that bind selectively to complementary DNA or RNA sequences inhibiting replication and translation. However, the potential of PNAs is restricted by the difficulties of delivering them to mitochondria within cells. To overcome this problem we conjugated a PNA 11mer to a lipophilic phosphonium cation. Such cations are taken up by mitochondria through the lipid bilayer driven by the membrane potential across the inner membrane. As anticipated, phosphonium–PNA (ph–PNA) conjugates of 3.4–4 kDa were imported into both isolated mitochondria and mitochondria within human cells in culture. This was confirmed by using an ion-selective electrode to measure uptake of the ph–PNA conjugates; by cell fractionation in conjunction with immunoblotting; by confocal microscopy; by immunogold-electron microscopy; and by crosslinking ph–PNA conjugates to mitochondrial matrix proteins. In all cases dissipating the mitochondrial membrane potential with an uncoupler prevented ph–PNA uptake. The ph–PNA conjugate selectively inhibited the in vitro replication of DNA containing the A8344G point mutation that causes the human mtDNA disease ‘myoclonic epilepsy and ragged red fibres’ (MERRF) but not the wild-type sequence that differs at a single nucleotide position. Therefore these modified PNA oligomers retain their selective binding to DNA and the lipophilic cation delivers them to mitochondria within cells. When MERRF cells were incubated with the ph–PNA conjugate the ratio of MERRF to wild-type mtDNA was unaffected, even though the ph–PNA content of the mitochondria was sufficient to inhibit MERRF mtDNA replication in a cell-free system. This unexpected finding suggests that nucleic acid derivatives cannot bind their complementary sequences during mtDNA replication. In summary, we have developed a new strategy for targeting PNA oligomers to mitochondria and used it to determine the effects of PNA on mutated mtDNA replication in cells. This work presents new approaches for the manipulation of mtDNA replication and expression, and will assist in the development of therapies for mtDNA diseases.

Las habilidades sociales de los niños y las niñas con Trastorno por Déficit de Atención con o sin Hiperactividad (TDA-H)

El Trastorno por Déficit de Atención con o sin Hiperactividad (TDA-H) es actualmente la patología más común entre la población infantil y juvenil. Los/as niños/as que presentan este trastorno, entre otras muchas necesidades, muestras notables dificultades en sus relaciones interpersonales. Por ello, este documento recoge información sobre qué es el TDA-H, sus características principales y especialmente, su influencia en el desarrollo de las habilidades sociales del alumnado. Una vez contemplados estos datos, se propone una propuesta de intervención y materiales que pueden emplear los/as docentes para trabajar el área social con los/as estudiantes con TDA-H.

Kazakhstan's attitude towards integration with Russia: less love, more fear. OSW Commentary No. 137, 29.05.2014

Russia’s annexation of Crimea and destabilization of Ukraine have created a new context for Kazakhstan’s foreign and domestic policy. The ongoing crisis in the relations with Russia and the West has also changed the current order in the entire post-Soviet area. From Astana’s perspective, the Kremlin’s policy towards Ukraine can be considered dangerous since it shows Russia’s determination to interfere with the domestic affairs of its neighbours in the pursuit of its own interests. Furthermore, this policy reveals and raises the price a country needs to pay for its potential attempts to break free from the Russian zone of influence. At present the biggest challenge for the authorities in Astana is the accelerated implementation of the idea of the Eurasian Union promoted by Moscow, which is to be another stage in the integration of post-Soviet states (presently Russia, Kazakhstan and Belarus). The signing of the Eurasian Union’s founding documents planned for late May 2014 and the launch of this organisation (scheduled for January 2015) is sure to bring Kazakhstan closer to Russia and simultaneously limit its economic and political independence. Nevertheless, Astana’s position in relations with Moscow will to a large extent depend on the new shape of the relations between Russia and China. China is pursuing its own strategic interests in Central Asia (including in the energy sector) and its main partner in the region is Kazakhstan. At the domestic level, Russia’s actions in Ukraine made the authorities in Astana fear that measures similar to those used in Ukraine could be applied towards Kazakhstan. On the one hand this has led to increased efforts aimed at consolidating the state and strengthening its structures, and on the other hand it has brought about a revision of those aspects of domestic policy which Russia could interpret as a pretext for interfering.

Azerbaijan-a growing problem for the West. OSW Commentary No. 146, 15.09.2014

Azerbaijan’s cooperation with the West, launched two decades ago, has helped it become a relatively strong and ambitious actor on the international stage. It has become a key country in the region from the Western (USA and the EU) and Turkish points of view, as well as an important partner in the energy sector. The strategic EU concept of the Southern Gas Corridor, also supported by the United States, is among the initiatives based on cooperation with Azerbaijan. Surprisingly, however, Azerbaijan’s increased ambition and importance have caused its policy to diverge ever farther from the expectations and plans formulated by the West. The changes in the balance of power in the South Caucasus, occurring in the context of the conflict in Ukraine, have forced Azerbaijan to revise its assessment of its position in the region. The main impetus for Azerbaijan’s actions is fear of Russia, as well as the weakness of the West which has become particularly apparent in the recent stages of the Ukrainian crisis. Azerbaijan’s actions so far have displayed its tendency to deepen its self-isolation in foreign affairs and consolidate its authoritarian system. This comes as a challenge to the West, whose ability to shape its relations with Azerbaijan has weakened considerably. This state of affairs poses the threat that in the current situation, the Southern Gas Corridor concept, which Azerbaijan amended in 2012 in its own favour, might become totally blocked.

Between energy security and energy market integration. Guidelines for the future development of the EU’s external energy policy in Europe’s neighbourhood. OSW Report, June 2011

For many years the European Union has been improving the efficient use of energy resources and yet the demand for energy in the EU continues to increase. When Europe belonged to one of the world’s key energy markets with relatively easy access to energy resources, growing energy needs were not seen as a source of concern. Today, however, as the competition for energy resources is intensifying and the global position of the EU energy market is being challenged by growing economies in the developing countries, above all China and India, the EU needs to adopt bold policies to guarantee the sustainable supply of energy. This report argues the EU needs to develop a fully-fledged external energy policy; i.e. a common, coherent, strategic approach that build bridges between the interests and needs of the EU integrated energy market on the one hand and supplier countries on the other. The EU’s external energy policy has two main objectives. The first one is to ensure a sustainable, stable and cost-effective energy supply. The second is to promote energy market integration and regulatory convergence with neighbouring countries (often but not always this supports the achievement of the first objective). However, in order to improve its effectiveness, the EU’s external energy policy needs to be seen in a broader economic and political context. Any progress in energy cooperation with third countries is contingent upon the EU’s general stance and offer to those countries.

China vs. Central Asia. The achievements of the past two decades. OSW Study 45/2013

The collapse of the USSR brought about conditions conducive to the dynamic development of relations between Central Asia and China. These relations have evolved from deep mistrust to the continually growing Chinese presence primarily in the region’s economy but also increasingly in its politics. Central Asia is playing a growing role in those areas of the economy which China sees as strategic (in particular in energy and communications). China’s ambitions and capabilities with regard to new areas and its geopolitical competitors are also being tested here. For the time being, it can be said that China has achieved vast success: its offer is appealing for the region, and Beijing has outpaced its Western rivals and has seriously challenged Russia’s position in the region. It remains, however, an open question whether China will be able to maintain and secure its present achievements and trends, which will be a serious challenge given the eternal instability in the region and Russia’s reintegration ambitions.