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Papers by Teodora Stoyanova Lyubenova

The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in ... more The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in recent years thanks to their increased performance in comparison to conventional monofacial PV modules. Nonetheless, due to the multiple variables that influence the performance of such devices, their characterization lacks consistency. In particular, when it comes to bifacial systems operating under real operating conditions there are voids to be filled in order to guarantee meaningful characterization for the long-term energy yield assessment. This can be achieved by the analysis of field data for different technologies, rack configurations and climates [1, 2]. Based on previous work on single bifacial modules this work extends the analysis of the behaviour of the rear-side irradiance of outdoor bifacial test arrays and their energy yield during one year. The rear irradiance non-uniformity (NU) analysis is crucial for long-term degradation rate and bifacial gain predictions (and hence ...

The aim of this paper is to study the optical properties of thin films with composition Cu 0.9 (I... more The aim of this paper is to study the optical properties of thin films with composition Cu 0.9 (In 0.7 Ga 0.3)Se 2 (CIGS) for a photovoltaic solar cell absorber. Samples with different film thicknesses were prepared using the doctor blade technique of previously co-precipitated aqueous precursors. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). For the first time, the optical properties of the thin layers with this composition, obtained using the doctor blade technique, were investigated. The optical properties were studied by transmittance and reflectance measurements in the infrared region and are correlated with film thickness. The dependence of the absorption coefficient on wavelength and the energy gap was found to be affected by the layer depth. The greater absorption coefficient is related to thinner CIGS layer. The refractive index results in an abnormal dispersion. The optical band gap was also determined in accordance with the sample chemical composition.

38th European Photovoltaic Solar Energy Conference and Exhibition

The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in ... more The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in recent years thanks to their increased performance in comparison to conventional monofacial PV modules. Nonetheless, due to the multiple variables that influence the performance of such devices, their characterization lacks consistency. In particular, when it comes to bifacial systems operating under real operating conditions there are gaps to be filled in order to guarantee meaningful characterization for the long-term energy yield assessment. This can be achieved by the analysis of field data for different technologies, rack configurations and climates. Based on previous work on single bifacial modules, this work extends the analysis of the behaviour of the rear-side irradiance of outdoor bifacial test arrays and their energy yield during one year. The rear irradiance non-uniformity (NU) analysis is crucial for long-term degradation rate and bifacial gain predictions (and hence bankability) in medium and large utility-scale solar systems with high-efficiency bifacial modules.

8th World Conference on Photovoltaic Energy Conversion, 2022

A double-sided solar simulator based on an existing large-area long pulse flash solar simulator a... more A double-sided solar simulator based on an existing large-area long pulse flash solar simulator and a low-cost LED-based rear bias light has been developed at European Solar Test Installation (ESTI) (Joint Research Centre, European Commission) for studying and validating the double-side indoor testing approach for current-voltage (I-V) characterization of bifacial modules. "Self-reference" methodology is applied using an accredited reference values (ISO/IEC 17025) obtained by single-side illumination. The proposed approach and prototype LED simulator for full size modules has demonstrated adequate performance in comparison with the single-side measurements based on a commercial Class AAA simulator using validated standard methodology. The electrical performance expressed in similar current-voltage (I-V) curves and power output reveals the suitability of the method for characterization of bifacial devices. The LED bias light source could be classified as a "Class C" solar simulator. The analysis of different representative bifacial PV devices available on the market shows different electrical behaviour according to their bifaciality factor.

Publications Office of the European Union, 2022

The European Green Deal set out key actions in the promotion and deployment of renewable energies... more The European Green Deal set out key actions in the promotion and deployment of renewable energies in order to realize the EU target of energy transition to a carbon neutral energy system. Photovoltaic solar energy is one of the key technology renewable energy sources to enable this transition. The European Commission’s JRC with its PV Energy project and the dedicated European Solar Test Installation Laboratories has been working to support the development and deployment of innovative, dependable and reliable photovoltaic solar energy solutions. This report presents the contribution of the European Solar Test Installation to enable this transition. The document describes the activities carried out in support of innovation concerning new materials from universities and research centres, dissemination activities of best practice for measurement and testing to peer laboratories in the international community and the application of the knowledge generated to improve international standards for characterising and assessing photovoltaic technologies. In addition, we report how the expert knowledge of the JRC is contributing with our partner DG’s to develop appropriate transition methods as part of the regulation for Ecodesign and Energy Labelling for PV modules, inverters and systems.

Universitat Jaume I, 2009

Los oxidos conductores transparentes (TCO, transparent conductive oxide) son materiales opticamen... more Los oxidos conductores transparentes (TCO, transparent conductive oxide) son materiales opticamente transparente y electricamente conductores. Se empelan en celulas solares fotovoltaicas en forma de peliculas y actuan como una ventana para que la luz pase a traves del material activo (absorbedor) y como contacto ohmico para transporte de portadores de carga.

El proceso de vitrificacion es un metodo de procesamiento adecuado para inertizar residuos toxico... more El proceso de vitrificacion es un metodo de procesamiento adecuado para inertizar residuos toxicos, a traves del concepto de economia circular, y se adapta perfectamente a los requerimientos de la industria ceramica mas tecnificada, industria 4.0. Con la transformacion de los vidrios de partida despues de la vitrificacion en materiales vitroceramicos, mediante un tratamiento termico controlado, es posible lograr la inmovilizacion de una amplia gama de desechos industriales (residuos minerales, lodos de vertederos, escorias, cenizas...). Ademas, el bajo coste y la gran disponibilidad de residuos hace que estos materiales vitroceramicos sean muy atractivos desde un punto de vista economico y tecnologico.

Advances in Science and Technology, 2006

Ceramic pigments with Cr-doped sphene structure (CaSn1-xCrxSiO5, CaTi1-xCrxSiO5) were synthesized... more Ceramic pigments with Cr-doped sphene structure (CaSn1-xCrxSiO5, CaTi1-xCrxSiO5) were synthesized by both spray drying an aqueous solution of precursor salts plus further calcining the resulting powders and conventional ceramic method. The thermal evolution of products was studied by X-Ray Powder Diffraction (XRPD). The powder morphology and chemical composition were analyzed by SEM-EDX. The color efficiency of pigments was evaluated by colorimetric analysis (CIELab system). Results showed that the spray drying process decreased the maximum firing temperature and increased the color efficiency of Cr-doped sphene pigments therefore enhancing a higher reactivity of powders compared with the solid state process.

Ceramic Forum International, Aug 4, 2014

Chemie der Erde - Geochemistry, 2014

Chromium-doped titanite and malayaite samples, which were synthesised to evaluate their performan... more Chromium-doped titanite and malayaite samples, which were synthesised to evaluate their performance as ceramic pigments, show remarkable photoluminescence behaviour. Emissions of centres related to traces of trivalent rare-earth elements (REE) are observed exclusively from chromium-free samples. Their Cr-doped analogues (containing the same REEs on the same concentration levels), in contrast, only show broad-band Cr 3+ emission whereas all REE emissions are suppressed. This behaviour is assigned to quenching of REE emissions by chromium centres (i.e., REE 3+ → Cr 3+ energy transfer).

Solar, 2021

Doped ZnO are among the most attractive transparent conductive oxides for solar cells because the... more Doped ZnO are among the most attractive transparent conductive oxides for solar cells because they are relatively cheap, can be textured for light trapping, and readily produced for large-scale coatings. Here, we focus on the development of alternative Na and K-doped ZnO prepared by an easy low-cost spray pyrolysis method for conducting oxide application. To enhance the electrical properties of zinc oxide, alkali-doped Zn1−x MxO (x = 0.03) solid solutions were investigated. The resulting layers crystallize in a single hexagonal phase of wurtzite structure with preferred c-axis orientation along a (002) crystal plane. Dense, well attached to the substrate, homogeneous and highly transparent layers were obtained with great optical transmittance higher than 80%. The optical energy band gap of doped ZnO films increase from 3.27 to 3.29 eV by doping with Na and K, respectively. The electrical resistivity of the undoped ZnO could be decreased from 1.03 × 10−1 Ω.cm to 5.64 × 10−2 Ω.cm (K-d...

2018 6th International Renewable and Sustainable Energy Conference (IRSEC), 2018

CZTSSe semiconductor has been deposited and crystallized onto alternative substrates using low-co... more CZTSSe semiconductor has been deposited and crystallized onto alternative substrates using low-cost and easy processing method of synthesis in order to investigate possible substitutes of conventional glass for building integrated photovoltaics. Soda-lime glass, ceramic laminates and stainless steel have been used as a photovoltaic substrates. SEM, Raman and XRD characterization techniques have been used in order to study the influence of each substrate in CZTSSe crystallization. CdS and i-ZnO/ITO have been deposited in order to complete the photovoltaic devices. Around 2% efficiency was obtained using soda-lime glass and ceramic laminates and 0,8% efficiency in stainless steel devices.

The authors kindly acknowledges the financial support from Ministry of Education and Science, Bul... more The authors kindly acknowledges the financial support from Ministry of Education and Science, Bulgarian National Science Fund, project DFNI T-02-27 under the project “Multi-functional and innovation coatings for construction and metals”.

Síntesis y depósito de capas fotoabsorbentes tipo cigs para dispositivos fotovoltaicos-UJI

38th European Photovoltaic Solar Energy Conference and Exhibition

The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in ... more The bifacial crystalline silicon (Si) photovoltaic (PV) module market has grown significantly in recent years thanks to their increased performance in comparison to conventional monofacial PV modules. Nonetheless, due to the multiple variables that influence the performance of such devices, their characterization lacks consistency. In particular, when it comes to bifacial systems operating under real operating conditions there are gaps to be filled in order to guarantee meaningful characterization for the long-term energy yield assessment. This can be achieved by the analysis of field data for different technologies, rack configurations and climates. Based on previous work on single bifacial modules, this work extends the analysis of the behaviour of the rear-side irradiance of outdoor bifacial test arrays and their energy yield during one year. The rear irradiance non-uniformity (NU) analysis is crucial for long-term degradation rate and bifacial gain predictions (and hence bankability) in medium and large utility-scale solar systems with high-efficiency bifacial modules.

8th World Conference on Photovoltaic Energy Conversion, 2022

Publications Office of the European Union, 2022

Universitat Jaume I, 2009

Advances in Science and Technology, 2006

Ceramic Forum International, Aug 4, 2014

Chemie der Erde - Geochemistry, 2014

Solar, 2021

2018 6th International Renewable and Sustainable Energy Conference (IRSEC), 2018

Síntesis y depósito de capas fotoabsorbentes tipo cigs para dispositivos fotovoltaicos-UJI

Agri Photovoltaics Achieving its full potential in the EU Energy Transition, 2022

Agri-Photovoltaics (Agri-PV), the combination of agricultural use of land with the production of ... more Agri-Photovoltaics (Agri-PV), the combination of agricultural use of land with the production of electricity from photovoltaics, has the potential to make a major contribution to achieving the targets set in the European Green Deal (EGD). Plans for photovoltaics to reach the Terra watt scale by 2050 imply that finding suitable space can be a challenge. Already for 2030 its estimated that about 1 million hectares of land currently designated arable (approx. 1%) would be needed for ground mounted PV systems. Dual use via Agri-PV can help gain public acceptance and directly benefit farmers and rural communities. Currently, 90% of PV market is covered by the Si technology. Among the conventional monofacial panels exist another more advanced variant called bifacial that highlight with high module efficiencies and low prices, the same as the monofacial ones. It is forecasting that will reach 35% on the panel market in 2030. The bifacial technology is mainly ground-mounted and it is very attractive approach for Agri-PV application. The presentation describes the potential of this technology in the field of agriculture.