Review of the legislative framework for the remuneration of photovoltaic production in Spain: a case study

Spain is among the European countries with the greatest photovoltaic potential. During the first decade of the 2000s, Spain was a European leader in installed photovoltaic power and job creation in the renewable energy sector, strongly influenced by a very favorable regulatory framework and public subsidies at a time of economic growth. That situation would be completely reversed with the regulatory changes introduced in 2012 to combat the tari deficit and the instability in the electricity supply system, problems accentuated by the economic crisis. The main objective of this study is to present an exhaustive review of the legislative changes that have a ected photovoltaic energy in Spain. Using real data on electricity production and the remuneration of a typical photovoltaic plant, we show that there was a very significant fall in the economic returns that investors had come to expect, within a system that prioritized, first and foremost, the initial investment rather than the levels of electricity production. The changes to the legislative framework a ecting a typical 100 kWp photovoltaic (PV) facility that entered into service before 2007 provoked a significant decrease of 8.7% in expected revenues, calculated from real data of production and income. These economic losses can be even higher, with a drop in revenue of almost 25% if the entire period of the installation’s useful life is analyzed. Public support for renewable energy is important for its introduction into the electricity market, but so is regulatory stability that o ers investment security and predictability for maintaining investment and development in the renewable energy sectorRegional Government of Castilla y León under the “Support Program for Recognized Research Groups of Public Universities of Castilla y León” (ORDEN EDU/667/2019) and the Spanish Ministry of Science, Innovation, and Universities under the I + D + i state program “Challenges Research Projects” (Ref. RTI2018-098900-B-I00

Real energy payback time and carbon footprint of a GCPVS

Grid connected PV systems, or GCPVS, produce clean and renewable energy through the photovoltaic e ect in the operation stage of the power plant. However, this is the penultimate stage of the facilities before its dismantlement. Before starting generating electricity with zero CO2 emissions, a negative energy balance exists mainly because of the embodied energy costs of the PV components manufacturing, transport and late dismantlement. First, a review of existing studies about energy life cycle assessment (LCA) and Carbon Footprint of PV systems has been carried out in this paper. Then, a new method to evaluate the Real Energy Payback Time (REPBT), which includes power looses due to PV panels degradation is proposed and di erences with traditional Energy Payback Time are analysed. Finally, a typical PV grid connected plant (100 kW nominal power) located in Northern Spain is studied in these sustainability terms. This facility has been firstly completely modelled, including PV modules, inverters, structures and wiring. It has been also considerated the energy involved in the replacement of those components with shorter lifespan. The PV panels degradation has been analysed through the comparison of normalised flash test reports on a significant sample of the installed modules before and 5 years after installation. Results show that real PV degradation a ect significantly to the Energy Payback Time of the installation increasing slightly a 4:2% more the EPBT value for the case study. However, along a lifespan of 30 years, the GCPVS under analysis will return only 5:6 times the inverted energy on components manufacturing, transport and installation, rather than the expected 9:1 times with the classical estimation

Photosynthetic active radiation, solar irradiance and the CIE standard sky classification

Plant growth is directly related to levels of photosynthetic photon flux density, Qp. The improvement of plant-growth models therefore requires accurate estimations of the Qp parameter that is often indirectly calculated on the basis of its relationship with solar irradiation, RS, due to the scarcity of ground measurements of photosynthetic photon flux density. In this experimental campaign in Burgos, Spain, between April 2019 and January 2020, an average value of the Qp/Rs ratio is determined on the basis of measurements at ten-minute intervals. The most influential factor in the Qp/Rs ratio, over and above any daily or seasonal pattern, is the existence of overcast sky conditions. The CIE standard sky classification can be used to establish an unequivocal characterization of the cloudiness conditions of homogeneous skies. In this study, the relation between the CIE standard sky type and Qp/Rs is investigated. Its conclusions were that the Qp/Rs values, the average of which was 1.93 0.15 mol J�����1, presented statistically significant di erences for each CIE standard sky type. The overcast sky types presented the highest values of the ratio, while the clear sky categories presented the lowest and most dispersed values. During the experimental campaign, only two exceptions were noted for covered and partial covered sky-type categories, respectively, sky types 5 and 9. Their values were closer to those of categories classified as clear sky according to the CIE standard. Both categories presented high uniformity in terms of illumination.Spanish Ministry of Science and Innovation, grant number RTI2018-098900-B-I00 and Consejería de Educación, Junta de Castilla y León, grant number BU021G1

Experimental analysis of a novel PV/T panel with PCM and heat pipes

A new design for the use of photovoltaic and thermal (PV/T) technology with thermal storage is reported in this work. In the new design, a phase change material (PCM) tank is added to the backside of the photovoltaic panel. The advantages of this design are the storage of thermal energy and the efficiency improvement of the photovoltaic (PV) panel as a result of the temperature control of the PV cell during the phase change process. In addition, a perimeter with a black surface surrounds the PV panel to increase the absorption of thermal energy. The thermal energy is then transferred to the backside of the PCM tank by heat pipes. One prototype with lauric acid as PCM was tested under two different operating configurations and resulted in an overall daily efficiency of 50% coulding be improve by controlling the PCM temperature during the day.Regional Government of Castilla y León, Spain (Ref. BU034U16) and the Spanish Ministry of Science, Innovation & Universities under the I+D+i state program “Challenges Research Projects” (Ref. RTI2018-098900-B-I00

New device for the simultaneous measurement of diffuse solar irradiance on several azimuth and tilting angles

A device is proposed for the measurement of diffuse solar irradiance on tilted surfaces pointing-to as well as fixed on the equatorial direction. Most commercial devices are not designed for this purpose. Here, we present a specific design for a system based on a single multi-lobe shadow-ring that allows us to measure diffuse irradiance with several tilted pyranometers – from 60 to 90 degrees from the horizontal plane – and on different azimuth angles. This first prototype allows us to measure in the four cardinal directions. The ring is designed to minimize the covered celestial dome observed by each sensor. Moreover, the complete device needs a very small installation area and its simplicity means it is inexpensive and easy to operate. The measurements have subsequently to be corrected with a geometrical correction factor that takes into account the portion of the sky vault blocked by the shadow-ring. These measurements are essential for estimating solar potential on tilted surfaces – such as building façades – and for improving current anisotropic solar models, among many other applications.Spanish Government (grant ENE2011-27511

Implementation of PV plants in Spain: a case study

The implementation process of a photovoltaic system and its connection to the national grid in Spain is examined from an economic, an administrative and a legal standpoint. In the first place, this case study describes the solar farm, and it goes on to examine the economic aspects of electricity production, its associated costs, and relevant grants and financial subsidies. Finally, problems related to the administration of the project and the issuing of permits by local and regional authorities are discussed.project BU019A08 supported by the Department of Culture and Education of the Regional Government of Castilla y León, Spai

About a case report of giant hydronephrosis

Introduction. Our objective is to report a case of an infrequent entity as the giant hydronephrosis. Case Report. We report the case of an 82-syear-old male referred for a poor general condition. A radiological study revealed a great left hydronephrosis secondary to an urothelial carcinoma. The patient died due to his poor general condition. A histological diagnosis revealed a transitional cell carcinoma of renal pelvis and ureter and atrophic renal parenchyma. Conclusion. Giant hydronephrosis represents a very often entity to be taken into account in cases with big cystic abdominal masses in absence of unilateral or bilateral kidney. Simple nephrectomy is the treatment of choice in most cases. Nevertheless, in cases of nonsubsidiary surgery, percutaneous drainage may be necessary

Benchmarking of meteorological indices for sky cloudiness classification

Sky classification is a complex problem, due in part to such abstract conceptual definitions as clear, intermediate, and overcast, as well as other intermediate ranges. The CIE (Commission Internationale de L’Éclairage) Standard classification offers a solution to this problem, although its application requires data on the luminance distribution of the whole sky that are less commonly available. A benchmarking and classification system of ten meteorological indices is introduced in this study to classify the sky types from overcast to clear. The indices can be calculated from measurements of global, diffuse, and direct irradiance that are widely available from meteorological ground stations. The classification system uses confusion matrices, a machine-learning tool that generates a visual display of the results of supervised-learning algorithms. The CIE Standard skies classification, applied to half hourly sky-scanner measurements in Burgos (Spain), over the period June 2016 - May 2017, is used in this study as a baseline reference for a comparative review of the results from the meteorological indices and their results. They are classified by four performance ratings: Accuracy, Jaccard, Cohen, and Matthews, which feature both classification similarity and the randomness of any agreement. All meteorological indices yielded a high average degree of accuracy - close to 80% - in a detailed review of their classification. Neverthless, the results suggested that Perez’s Clearness Index based on global, diffuse and direct radiation measurements offered the most precise classification of the skies, followed closely by the Klucher Clearness Index and the Perraudeau Nebulosity Index.Regional Government of Castilla y León under the “Support Program for Recognized Research Groups of Public Universities of Castilla y León” (ORDEN EDU/667/2019) and the Spanish Ministry of Science, Innovation & Universities under the I + D + i state programme “Challenges Research Projects” (Ref. RTI2018-098900-B-I00

Spanish photovoltaic solar energy: institutional change, financial effects, and the business sector

Spain is a country with a high dependence on fossil fuels. For this reason, in 2007, it implemented a bonus system that aimed to encourage the production of renewable energies, particularly photovoltaic solar energy. These production bonuses, guaranteed by the Spanish government, led to an exponential increase in the number of companies in the market and, consequently, the MWh produced. However, in 2012, given the excessive budgetary burden involved in maintaining this “feed-in tariff” system and after several years of institutional instability, the aforementioned system of incentives for phoyovoltaic (PV) energy was eliminated. This paper has tried to analyze the consequences of this institutional change, a clear example of the “hold up” problem. For this purpose, a sample of 5354 companies, which was divided, geographically, into Spanish regions and, temporarily, into three different periods, has been taken, considering diverse economic and financial variables. The results show a notable weakening of the sector that, due to the effects of the regulatory change, has lost attractiveness and profitability for investors and is consequently suffering from stagnation, which has led to the disappearance of many companies in the sector.Raquel Fernández González gratefully acknowledge the financial support provided by the Xunta de Galicia under Grants ED431C2018/48 and ED431E2018/07 and the Ministry of Economy and Competitiveness under Grant RTI2018-099225-B-100. This research was funded by Regional Government of Castilla y León under the “Support Program for Recognized Research Groups of Public Universities of Castilla y León” (ORDEN EDU/667/2019) and the Spanish Ministry of Science, Innovation & Universities under the I + D + i state program “Challenges Research Projects” (Ref. RTI2018-098900-B-I00)

Solar Ultraviolet Irradiance Characterization under All Sky Conditions in Burgos, Spain

Solar Ultraviolet Radiation (UVR), which is identified as a major environmental health hazard, is responsible for a variety of photochemical reactions with direct effects on urban and aquatic ecosystems, human health, plant growth, and the deterioration of industrial systems. Ground measurements of total solar UVR are scarce, with low spatial and temporal coverage around the world, which is mainly due to measurement equipment maintenance costs and the complexities of equipment calibration routines; however, models designed to estimate ultraviolet rays from global radiation measurements are frequently used alternatives. In an experimental campaign in Burgos, Spain, between September 2020 and June 2022, average values of the ratio between horizontal global ultraviolet irradiance (GHUV) and global horizontal irradiance (GHI) were determined, based on measurements at ten-minute intervals. Sky cloudiness was the most influential factor in the ratio, more so than any daily, monthly, or seasonal pattern. Both the CIE standard sky classification and the clearness index were used to characterize the cloudiness conditions of homogeneous skies. Overcast sky types presented the highest values of the ratio, whereas the clear sky categories presented the lowest and most dispersed values, regardless of the criteria used for sky classification. The main conclusion, for practical purposes, was that the ratio between GHUV and GHI can be used to model GHUV.This research was funded by the Spanish Ministry of Science and Innovation, grant numbers RTI2018-098900-B-I00 and TED2021-131563B-I00, and Junta de Castilla y León, grant numbers INVESTUN/19/BU/0004 and INVESTUN/22/BU/0001