Andreas Gombert

• PhD
• CEO at Rheintacho

The Concentrix CPV technology was developed over the last ten years from a laboratory scale to an industrial scale with fully automized production lines and installed in multi MW CPV power plants. This paper describes the R&D work which was required to proceed from first prototypes to industrial products. Highlighted are significant steps to improv...

A Concentrator photovoltaic (CPV) power plant with Concentrix Technology consists essentially of a group of CPV Systems cabled together in an electrical building block. The main criteria for selecting a suitable region for a CPV installation should be, of course, a high DNI level and a DNI/GNI ratio higher than 0.85. The development of the standard...

Soitec Solar GmbH started 2005 as a spin off from the Fraunhofer Institute for Solar Energy Systems ISE and developed the ConcentrixTM module technologies to industrial mass production in order to gain a significant share of the PV market. The three key drivers which had to be addressed by the development are increasing efficiency, cost reduction a...

The purpose of this paper is twofold: Firstly, we define three performance metrics to evaluate Concentrator Photovoltaic (CPV) power plants, namely performance ratio, performance index and availability. Secondly, we apply these metrics to analyze more than six years of field data from two-long running, small power plants, and some weeks of field da...

The purpose of this paper is twofold: Firstly, we define three performance metrics to evaluate Concentrator Photovoltaic (CPV) power plants, namely performance ratio, performance index and availability. Secondly, we apply these metrics to analyze more than six years of field data from two-long running, small power plants, and some weeks of field da...

Written by renowned experts in the field of photon management in solar cells, this one–stop reference gives an introduction to the physics of light management in solar cells, and discusses the diff erent concepts and methods of applying photon management. The physics, principles, concepts, technologies, and methods used are explained to show how t...

An overview of the fundamentals, the optimization strategies, and specific optical designs of concentrators for concentrated photovoltaic (CPV) systems is given. Several designs of secondary optical element (SOE) were compared with respect to their CAP and the achievable photocurrent densities. When using silicone on glass (SOG) Fresnel lens primar...

In this work CPV modules based on Fresnel lenses and using refractive secondary optical elements (SOEs) are investigated. Pure silicone as well as glass SOEs glued on top of the solar cells are explored in prototype modules. They are differently manufactured in respect to how the secondary optics was assembled. For example, units with secondary sil...

During the last years SOITEC has co-developed a 4-junction solar cell (SmartCell™) with world record conversion efficiency. To verify suitability for concentrator application in SOITEC’s Concentrix™ CPV module, early long-term outdoor performance monitoring was initiated. To date, some module prototypes have been already exposed for more than one y...

A network model for multi-junction solar cells has been combined with ray tracing and finite element simulations of a Fresnel lens in order to interpret experimentally derived measurement results. This combined model reveals a good agreement between simulation and measurement for advanced four-junction solar cells under a Fresnel lens when the cell...

CPV systems using 3-junction solar cells have proven good performance and reliability. As the performance of 3-junction cells is saturating [1], the logical next step is the introduction of 4-junction (4-J) solar cells into CPV modules. The current world record for cell efficiency under concentrated light of 46.0% was achieved using a wafer bonded...

This paper examines the long term reliability of Soitec's CPV technology by analyzing a total of 68 months of AC energy and Direct-Normal Irradiance data acquired at Puertollano, Spain. The reliability of the module performance is quantified using the AC Performance Ratio. The results are verified by repetitive indoor measurements of seven modules...

The purpose of this paper is twofold: Firstly, we define three performance metrics to evaluate Concentrator Photovoltaic (CPV) power plants, namely performance ratio, performance index and availability. Secondly, we apply these metrics to analyze more than six years of field data from two-long running, small power plants, and some weeks of field da...

Environmental testing following the draft of the IEC62817 standard has been carried out at ISFOC using a Soitec Solar tracker drive. The objective of this work is twofold; first to assure that the tracker design can perform under varying conditions and survive under extreme conditions and secondly to test the viability and usefulness of the tests d...

A six-parameter formula is proposed for describing the hourly alternating current performance of a grid-connected, passively cooled concentrator photovoltaic (CPV) system. These system parameters all have physical meanings, and techniques are described for deriving their numerical values. The predictions of the model are compared with the measured...

Within the EU funded project NACIR a Concentrating Photovoltaic (CPV) stand-alone system is developed to provide electric power for water pumping, desalination and irrigation application. The system design requires only small sized battery storages to secure power supply for the measurement and control equipment as well as for the motors of the tra...

This paper examines the reliability and the predictability of Soitec's CPV technology by analyzing a total of 149 months of AC energy and Direct-Normal Irradiance data acquired at three CPV power plants. Two of the plants are located in Spain and have been in operation since 2008. The third plant is located in South Africa and has been in operation...

A formula is proposed that characterizes the hourly AC power output of a passively-cooled Concentrator Photovoltaic (CPV) system in terms of 6 easily-determined system parameters and 4 measured or computed environmental variables. The model was tested on a grid-connected Soitec CPV system at Sede Boqer in the Negev Desert of Israel and found to be...

Highly concentrating photovoltaic systems (HCPV) based on III-V multi-junction solar cells entered the PV market recently. Since 2008, HCPV power plants operate in various countries and valuable experiences could be gained. Reliability and durability of CPV power plant components are very much impacting the overall life cycle costs of a CPV power p...

The design of control systems of concentrator photovoltaic power plants will be more challenging in the future. Reasons are cost pressure, the increasing size of power plants, and new applications for operation, monitoring and maintenance required by grid operators, manufacturers and plant operators. Concepts and products for fixed-mounted photovol...

Luminescent solar concentrators (LSC) are used in photovoltaic applications to concentrate direct and diffuse sunlight without tracking. We employed 2D FDTD simulations to investigate the concept of a photonic LSC (PLSC), where the luminescent material is embedded in a photonic crystal to mitigate the primary losses in LSCs: the escape cone and rea...

One remote sensing and two in-situ methods for quantifying the spectral distribution of the direct normal irradiance and its impact on multi-junction solar cells are compared for three different sites in Southern Europe, on the Arabian Peninsula and in the South West of the USA. For each method, the uncertainty is assessed. The spectral parameter Z...

Forecast DNI values in hourly resolution for one day ahead are evaluated by a comparison with pyrheliometer ground measurements. Three months of such day ahead forecasts from four different providers for a site close to Questa, NM, USA are analyzed firstly by calculating the RMSE and the mean bias error. Secondly, cumulative distributions of the DN...

In 2008, Soitec started to launch a 32m2 CPV system which included 90 modules per tracker. In order to realize the fast installation of multi-MW power plants the CPV module CX-M500 with an aperture area of 7,84 m2 was developed together with the new tracker CX-T030 which is optimized for carrying 12 of the new modules. This paper gives an overview...

Reliability and durability of all CPV power plant components is very important since long-term operation in a harsh environment is required. The last three Concentrix CPV Module generations have all been certified according to IEC 62108:2007. Based on field experience to date, there is no indication of where and how to improve Soitec's Concentrix™...

A 4-parameter formula is proposed for describing the hourly AC performance of a grid-connected, passively-cooled CPV system. The formula is validated against data from a pair of Soitec systems in the northern and southern hemispheres and found to be accurate to at least +/- 10% at all times of the year.

Highly concentrating photovoltaic systems (HCPV) based on III-V multi-junction solar cells entered the PV market recently. Since 2008, HCPV power plants operate in various countries and valuable experiences could be gained. This paper gives an overview on Soitec's experiences, the lessons learned and the perspective on the cost competitiveness of H...

Luminescent solar concentrators (LSC) are used in photovoltaic applications to concentrate direct and diffuse sunlight without tracking. We employed 2D FDTD simulations to investigate the concept of a photonic LSC (PLSC), where the luminescent material is embedded in a photonic crystal to mitigate the primary losses in LSCs: the escape cone and rea...

Soitec's CPV technology is based on a module with a glass cover and receiver plate, triple junction solar cells, a Fresnel lens array with a relatively small aperture of the primary lens and metal sheet as a heat sink. The first volume production of modules took place in 2007 and in power plants on four continents valuable filed experience could be...

Recent investigations of silicone‐on‐glass (SoG) Fresnel lens concentrator optics have shown a dependence of the optical efficiency and module performance on lens temperature. It was shown that the temperature dependence is dominated by a reduction of the refractive index with increasing temperature and a deformation of the lens structure due to th...

This paper presents the new module generation (CX‐75‐III), which was developed in an all‐embracing cost optimization. The single primary lens was refined for optical efficiency and its size increased to 5.7×5.7 cm 2 , thus dramatically reducing the part count. Thermal simulations were used in order to dimension the heat spreader and ensure t...

The accuracy of the two‐stage PVSyst model for the Concentrix CPV Technology is determined by comparing modeled to measured values. For both stages, i) the module model and ii) the power plant model, the underlying approaches are explained and methods for obtaining the model parameters are presented. The performance of both models is quantified usi...

The field performance of Concentrix CPV installations is studied for several locations and with respect to the climatic conditions. Four locations are addressed and two locations with very different climatic conditions are studied in detail. The performance of the CPV systems is very similar on both sides. The analyzed data include DNI, ambient tem...

An initial analysis of short term electricity storage for CPV power plants is performed with respect to its functions ``power output smoothing'' and ``end of day energy production''. First, the different storage technologies are shortly discussed. Then charge and discharge of the storage device of a model CPV plant is studied by using measured DNI...

Concentrix modules are based on III-V triple-junction cells, a Fresnel lens array with a relatively small single lens aperture of 5 square inches, and a cover and bottom plate made out of glass. The first power plants were built in Europe in 2008, later installations followed in the US, in the Middle and Far East and in Africa. This paper gives an...

Concentrix modules are based on III-V triple junction cells, a Fresnel lens array with a relatively small single lens aperture of 5 square inch, and a cover and bottom plate made out of glass. The first installations were conducted in 2008 in Europe, later installations followed in the US, in East Asia, in the Arabian Peninsula, and in Africa. This...

To improve two-step metallization processes for silicon solar cells, the influence of different seed layers and surface textures on the light-induced plating (LIP) deposition behaviour at different plating rates has been studied. Typical seed layers of screen- and aerosol printed silver paste have been tested on alkaline (random pyramid) and acidic...

This paper describes an approach of making the FLATCON® CPV technology compatible with standard photovoltaic simulation software like PVSYST and INSEL in order to facilitate yield estimations for potential power plant sites. Due to the use of triple-junction cells, the FLATCON® CPV module efficiency is more sensitive to changes in the solar spectru...

In this paper, a short introduction in design considerations of FLATCON® CPV module and field data of the system technology over up to two years are presented as well as field experiences with the operation of the systems. FLATCON® modules are based on III–V triple junction cells, a Fresnel lens array, and a glass cover and bottom plate. In 2008, C...

Concentrating photovoltaics (CPV) require large areas of optical components that concentrate incident sunlight effectively onto a solar cell. Fresnel lenses are often used as primary optical component providing this concentration. When applied in the field, varying conditions during operation lead to variations in lens temperature which has a stron...

Concentrating photovoltaic (CPV) systems based on III-V semiconductors entered the photovoltaic market recently. Concentrix Solar deploys the FLATCON® CPV module technology originally developed at the Fraunhofer Institute for Solar Energy Systems ISE. This paper gives a short introduction in design considerations of FLATCON CPV module and provides...

The FLATCON® concentrator photovoltaic (CPV) technology is presented. The first system in the US was installed in 2009 and shows an AC power efficiency of 25% and an AC energy efficiency of 22%.

Present developments of the lattice-matched In0.50Ga0.50P/In0.01Ga0.99As/Ge triple-junction solar cell incorporating a high bandgap top cell achieve average efficiencies of up to 40%. Metamorphic cell structures will further raise efficiencies above 40%. Both developments reduce the cost for CPV by increasing the performance of today's CPV systems....

In this paper, a review of the recent progress in concentrator photovoltaics (CPV) is given. In the first part, an introduction to CPV includes the concepts of solar concentration and the specific advantages of CPV. Then, the various optical designs are presented and discussed. In the second part, the recent success in bringing this technology to m...

Fresnel lenses are often used as primary optical components in concentrating photovoltaics (CPV). When applied in the field, varying conditions during operation lead to variations in lens temperature which has a strong impact on the optical efficiency of the lenses. A setup for indoor characterization with the ability to heat lens plates allows for...

In solar applications microstructured polymer surfaces can be used as optically functional devices. Examples are antireflective surfaces, daylighting, sun protection systems, concentrator photovoltaic modules and light trapping structures in organic solar cells. The examples and the principles of function of the respective microstructures are descr...

The historical developments of artificial “moth-eye” structures as anti-reflective surfaces are described. In theory, “moth-eye” structures are regarded as zero-order diffraction gratings as the relation of the grating period to the wavelength is such that only zero-order diffracted waves can propagate. The optical properties of the grating can be...

IntroductionBuried NanoelectrodesOrganic Photovoltaic Devices on Functional Microprism SubstratesAnode Wrap-Through Organic Solar CellSummaryReferences

In the framework of the NACIR project, the most advanced European Concentrating Photovoltaic (CPV) technologies are being installed in Morocco and Egypt. Concentrix Solar is installing in Egypt a 25 kWp stand-alone CPV system to be used for water pumping and irrigation purposes. For this project Fraunhofer-ISE is developing a specifically improved...

In this paper we report on research activities at the Fraunhofer Institute for Solar Energy Systems (ISE) and Concentrix Solar in the area of secondary optics for FLATCON^® modules. This concentrator photovoltaic (CPV) technology is based on Fresnel-lenses as primary optics, passive heat spreaders and triple-junction III-V solar cells. I...

The European Commission has subsidized the Project NACIR on CPV's for the next four years beginning on 1st January 2009. The main goal of this project is to join together the owners of the most advanced European CPV technology12, with respect to the state of the art, in order to research from their leading position new applications for CPV systems....

Highly efficient concentrator photovoltaic systems (CPV) use an optical concentrator to concentrate the solar radiation onto multi-junction solar cells (MJC) based on III-V semiconductors. Such cell have a record efficiency of 41% under concentration. In order to exploit the high cell efficiency a careful optimisation of the whole CPV system has to...

This paper gives an overview on photonics for photovoltaic systems. Starting from the spectral and angular distribution of the electromagnetic radiation from the sun, many important optical approaches how to improve the efficiency of solar cells are presented and discussed. Topics include antireflective coatings, various light trapping structures,...

One key problem in optimizing organic solar cells is to maximize the absorption of incident light and to keep the charge carrier transport paths as short as possible in order to minimize recombination losses during the charge carrier extraction. The large versatility of organic semiconductors and compositions requires specific optimization of each...

Directional and energy selective optical surface structures attached to solar cells may result in both, enhancement or deterioration of photovoltaic performance of a solar cell. On the one hand, restricting the cell acceptance to the small incidence angle of direct and circumsolar irradiation enhances the maximum path length of the light in a solar...

In this study we present a theoretical and experimental analysis of the application of photonic band stop filters on top of photovoltaic fluorescent concentrators in order to increase the photon collection efficiency. The light guiding effect of the fluorescent concentrator relies on total internal reflection. The escape cone of total internal refl...

Photon Management in Solar Cells By definition, photovoltaics is the transformation of the electro‐magnetic energy of solar light into electricity. Thus, photons stand at the beginning and electrons stand at the end of this value creation chain, respectively. Thus, photovoltaics investigates and optimizes all processes taking place in‐between the a...

A study was conducted to demonstrate ultrahigh photovoltages with organic photovoltaic nanomodules. It was demonstrated that grid lines are needed for the parallel interconnection of the photovoltaic module elements, to extract electrical power from the module. It was also demonstrated that low conductive grid lines can be used to extract electrica...

In this paper we present a high throughput testing setup for organic solar cells that is necessary for an efficient analysis of their behaviour. The setup comprises process parameter logging, automated measurement data acquisition and subsequent data management and analysis. Utilising this setup the reproducibility of solar cells and the effect of...

We report on the development of two types of organic solar cell modules one for energy autonomous systems and one for large area energy harvesting. The first requires a specific tailoring of the solar cell geometry and cell interconnection in order to power an energy autonomous system under its specific operating conditions. We present an organic s...

The Yablonovitch limit for light trapping in solar cells with Lambertian surfaces can be increased using angle selective absorbers thereby exploiting the limited incidence angle of solar radiation. We simulate the efficiency gain or loss caused by an angular and energy selective filter on top of the absorber, compared to a Lambertian and a flat abs...

One promising option for commercialisation of concentrating photovoltaics is the use of Fresnel lenses for concentrating sunlight on the solar cell. The effects of temperature on the efficiency of solar cells are a well known topic. In contrast, the influence of varying temperatures during operation on concentrator optics has rarely been discussed....

A nondestructive method for assessing the thickness of the photoactive layer in poly(3-hexyl-thiophene):1-(3-methoxy-carbonyl)propyl-1-phenyl-(6,6)C61 (P3HT:PCBM) solar cells is reported. In the approach the absorption spectrum of the solar cell as derived by optical simulations is fitted to the corresponding measured spectrum, varying only the P3H...

We prepared thin films of magnesium nickel with a wide compositional range from pure magnesium to the intermetallic compound Mg2Ni by e-beam evaporation. Capped with a thin Pd film such layers act as switchable mirrors upon exposure to gases containing hydrogen and oxygen. We investigated the reaction kinetics by measurement of the transmittance, a...

The current–voltage characteristic and the performance of organic bulk-heterojunction solar cells are very sensitive to small variations in the production steps or environmental influences. In our experiments, we found a large variation of the short-circuit current, which does not correspond to the device thickness as one might expect. The fill fac...

Organic solar cells have the potential to make cheap photovoltaic devices feasible. In order to achieve this, material and production costs have to be minimised by using device architectures, which are suited to tap the full potential of reel-to-reel production.The inversion of the layer sequence in organic bulk-heterojunction solar cells is motiva...

A novel cell architecture for organic solar cells is presented which is based on a functional microprism substrate. In contrast to the most widely used planar cell architecture with a transparent indium tin oxide (ITO) electrode, the microstructure results in a folded solar cell. Of benefit are the light trapping effect and the substitution of the...

Export Date: 17 October 2012, Source: Scopus, Art. No.: 4013890

IntroductionFabrication of microstructured surfaces by interference lithography Interference lithographyReplication and subsequent substrate processingActive materials for organic photonic crystal lasersLasing in two dimensional polymeric photonic crystalsSemiclassical theory of lasing in surface relief structures Semiclassical laser theory in stru...

We investigated organic bulk-heterojunction solar cells based on an absorber blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) by electrical impedance spectroscopy (EIS). A strong neck in the modulus plot of the EIS-spectra indicates that the absorber is divided into two regions of different conductivities...

One key problem in optimizing organic solar cells is to maximize the absorption of incident light and to keep the charge carrier transport paths as short as possible in order to minimize transport losses. The large versatility of organic semiconductors and compositions requires specific optimization of each system. We investigate two model systems,...

The production process of organic solar cells (OSCs) is investigated and the effects of parameter variations on experimental results are analysed with the Principal Component Analysis (PCA). This statistical method is applied to an exemplar data set, in which the materials' concentration in the absorber solution and the spincoating speed of the abs...

In solar control devices based on total internal reflection and microstructured surfaces, the Goos-Hänchen shift can lead to a significant decrease in the geometrical optical solar shading effect. The knowledge of the maximal size of the Goos-Hänchen shift for a specific geometry is an important information to estimate its effect on the desired fun...

In this paper we present detailed optical simulations of organic bulk-heterojunction solar cells built with inverted layer sequence as compared to the commonly used setup which is based on indium tin oxide (ITO) covered glass or plastic substrates and where the metal electrode is evaporated on top of the active absorber blend. The inverted setup ma...

Cited By (since 1996): 2, Export Date: 17 October 2012, Source: Scopus, Art. No.: 61970Z

New developments in large-scale micro-structuring of surfaces offer a wide range of applications in glazings with solar-control and light-redirecting properties. In many cases, e.g. when using prism or compound parabolic concentrator (CPC) arrays, the geometry of these structures allows or requires single facets of the structure to be selectively c...

This paper reports on the development of nanostructured, multifunctional TiAlN- and TiO2-coatings where the multifunctionality stems from their nanoscale surface topography. The coatings were sputter-deposited on silicon and steel substrates by a reactive RF-magnetron-process. For both types of coatings deposition parameters which led to a columnar...

This paper is to report on the development and investigation of a specific type of growth mode and surface morphology of PVD-coatings, namely a columnar growth mode where the individual columns are terminated by pyramid-shaped tips. TiAlN was chosen as a representative of the cubic crystal system, TiO2 as a representative of the tetragonal crystal...

We measured the electrical impedance spectra of organic bulk-heterojunction solar cells based on an absorber blend of poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester. Comparing the spectra of the non-treated device and after two consecutive treatments with applied forward bias voltage at 110 °C, we observed a region in the sem...

Along with efficiency and lifetime, costs are one of the most important aspects for the commercialization of organic solar cells. Thinking of large scale production of organic solar cells by an efficient reel-to-reel process, the materials are expected to determine the costs of the final product. Our approach is to develop functional substrates for...

Interference lithography is a manufacturing technique which allows the origination of various types of microstructures on large areas. Micro-structured surfaces with optical functions are useful for radiation power management applications as well as light management applications in displays and in solar energy systems. This paper presents the inter...

With surface-relief structures, optical functions that are required for radiation power management such as antireflection, light trapping, or light distribution and redirection can be obtained for new applications in solar energy systems and in displays. There, structures with submicrometer features must be distributed over large areas homogeneousl...

A range of surface finishing techniques have long been used on an industrial scale, to create an optimal surface coating and finish for solar energy systems. A novel approach is based on a micro-patterned plastic surface formed by a replication method. Such surfaces are mainly intended for solar protection systems, and allow the use of diffuse dayl...

An overview of diffractive optical elements for radiation power management in solar applications is given. Design and manufacturing techniques of the proposed elements are described and the suitability of the elements is discussed.

Linear micro-reflector arrays are used in various lighting applications where the selectivity between high reflectance for a defined range of angles of incidence and transmittance for other angles of incidence is most interesting. One goal is to miniaturize the unit elements in order to make the devices thinner and to give them a more homogeneous a...

The design of the front surface of a display, the interface to the viewer, requires careful selection of materials and coatings. The most prominent requirements for the front surface material are reflection or glare treatment, scratch resistance and of course a good optical appearance. Different types of optical films and coatings are available wit...

One limiting factor to the efficiency of the bulk heterojunction solar cell is the weak absorbance of the thin photoactive layer. The thickness is restricted by the small charge carrier mobility. Two cell concepts—light trapping with diffraction gratings and buried nano-electrodes—were investigated. Optical simulations based on rigorous coupled wav...

Export Date: 17 October 2012, Source: Scopus

An overview of diffractive optical elements for radiation power management in solar applications is given. Design and manufacturing techniques of the proposed elements are described and the suitability of the elements is discussed.

By surface-relief structures optical functions like anti-reflection, light trapping or light distribution and re-direction can be realized. New applications in solar energy systems and in displays require structures with sub-micron features which are homogeneously distributed over large areas. This paper addresses the design and the whole experimen...

Antiglare AG and low- or anti-reflection LR, AR are important optical features of the front surfaces of flat panel displays and other information displays. New types of holographic surface relief microstructures have been developed on large areas showing very good optical properties. Holographic exposure techniques give the freedom to carefully des...

Radiating surfaces at typical temperatures in the range of 1200 - 2000 K are the source of energy which is incident on the PV cells of TPV systems. The radiators or emitters may have very pronounced or weak spectrally selective properties on which TPV system efficiencies depend very much. This paper gives an overview of existing emitter technologie...

Microstructured films as optical components have become more and more important for information displays recently. Such films can act as light management components, that distribute light uniformly in LC displays or on rear projection screens. Glare control and AR can be achieved using microstructures on the front surface of displays. Recently deve...