Viabilidad económica de sistemas de riego fotovoltaico de alta potencia en la región de ECOWAS

Este artículo presenta una evaluación económica de sistemas de riego fotovoltaico de alta potencia (del orden de los cientos de kWp) en la región de ECOWAS, considerando sólo la inversión necesaria para sustituir (en sistemas de riego ya existentes) la red eléctrica o grupos diésel por un generador fotovoltaico. El estudio compara 7 países y dos modos de operación distintos: contra balsa y a presión constante. Los indicadores económicos obtenidos son muy favorables: TIR entre 8-47%, VAN entre 0.33-41.5x105 $, PRI entre 2.1-10 años. El LCOE está entre 4.5-17.4$cents/kWh, lo cual supone ahorros de 30-84% en comparación con sistemas alimentados por la red o por grupos diésel

Economics of stand-alone large PV irrigation systems in the ECOWAS region.

Solar PV generators coupled to water pumps represent an attractive option for reducing the economic cost and the environmental impact associated to irrigation applications. Prior studies have already evaluated the technical and economic viability of PV water pumping, but they all refer to systems with relatively small PV nominal power (up to 30 kW). The European project MASLOWATEN has recently reported technical and economic validations for 5 large demonstrators (with PV powers in the range of 40-360 kWp) in the South of Europe, but these results are highly site-dependent and it would be interesting to extend them to other regions of the planet

Photovoltaic heat-pumps for cooling applications

In the light of the exhaustion of fossil fuels and of the fight against the climatic change, it is necessary to increase the penetration rates or renewables energies in the energetic system, as well as its electrification. This situation offers a variety of new niches for photovoltaic systems. In particular, heat pump systems powered by photovoltaic generators permit to supply the heating and cooling thermal demands with a technology that only consumes electricity. Furthermore, this electricity comes from a renewable source. Cooling applications are especially favorable for this technology because of the better matching between generation and demand, which permits to reduce or even eliminate the storage needs. This work presents a new technical solution for photovoltaic heat pump systems, with a stand-alone configuration without batteries. This way, electric storage can be substituted (if needed) by thermal storage, which generally is cheaper and more reliable. This solution has been validated with an experimental prototype, where two different control algorithms have been implemented for the compressor of the heat pump. One of them has the objective of maximizing the photovoltaic utilization; the other one has the objective of maintaining a constant temperature in a room. With the data obtained from the tests implemented in this prototype, a series of indicators, some of them proposed specifically in this work, have been calculated. These indicators permit to evaluate separately the performance of the heat pump unit (thorough the EER and the SPF), of the photovoltaic generator (thorough the PR, the PRPV,STC,ref and three utilization ratios for identifying the causes of hypothetical low PR values), the integration of both components (thorough the SPFPV-HP,STC.ref) and how renewable the system is (thorough the SFPV and the SCR for not stand-alone configurations). The analysis of the results shows the good performance of the prototype, and how it could be improved. It has also been evaluated the stability of the system against solar power fluctuations due to cloud-passing. A total of 75% of the cloud-passing events during the tests have been resisted. Finally, an economic feasibility assessment has been performed, comparing the stand-alone solution developed in this work with a self-consumption configuration and an only grid-powered system. This evaluation shows a high economic profitability of photovoltaic heat pump systems. The stand-alone solution allows to reduce the electricity costs, not only for the consumption but especially because the power access term can be eliminated. Thanks to this, the economic profitability of installing a photovoltaic system would be higher than for a self-consumption solution. The technical solution developed and validated in this work is particularly relevant for industrial applications, where it is feasible to power the compressor of the heat pump directly with a photovoltaic generator and a frequency converter. Some examples of cooling applications are the conservation of food and medicines or the control temperature in industrial ambiences. Additionally, this solution is also valid for heating applications like food drying (cereals, carnic products…), which makes it feasible for a big amount of market opportunities. ----------RESUMEN---------- Debido al agotamiento de los combustibles fósiles y a la lucha contra el cambio climático, se impone la necesidad de aumentar la penetración de las energías renovables en el sistema eléctrico y de electrificar el mismo. Esta situación abre un amplio abanico de nuevos nichos para los sistemas fotovoltaicos. Las bombas de calor alimentadas con generadores fotovoltaicos permiten cubrir las demandas de energía térmica con una tecnología que sólo consume electricidad, siendo esta además de origen renovable. En particular, las aplicaciones de frío son especialmente ventajosas por el mejor ajuste entre generación y demanda, reduciéndose e incluso eliminándose la necesidad de sistemas de acumulación. Este trabajo presenta una nueva solución técnica desarrollada para sistemas de bomba de calor fotovoltaicos, autónomos y sin baterías. De esta forma, la acumulación eléctrica puede sustituirse (en caso de hacer falta) por acumulación térmica, en general más barata y fiable. Esta solución ha sido validada en un prototipo experimental, en el que se han implementado dos lógicas de control para el compresor de la bomba de calor: una que busca maximizar la utilización de la generación fotovoltaica y otra que busca mantener una temperatura constante en un espacio. Con los datos obtenidos de los ensayos con este prototipo se han calculado una serie de indicadores de rendimiento, algunos de ellos propuestos en este trabajo. Estos indicadores permiten evaluar por separado el rendimiento de la bomba de calor (mediante el EER y el SPF), del generador fotovoltaico (mediante el PR, el PRPV,STC,ref y tres factores de utilización, que permiten identificar las causas de posibles valores bajos del PR), la calidad de la integración de ambos componentes (mediante el SPFPV-HP,STC.ref) y cuánto de renovable energéticamente es el sistema (mediante el SFPV y el SCR, para configuraciones no autónomas). Mediante el análisis de los valores obtenidos, se ha demostrado el correcto funcionamiento del prototipo y se han identificado las principales vías de mejora. También se ha evaluado la estabilidad ante fluctuaciones de potencia por paso de nube, de las cuáles se han soportado un 75% durante los ensayos. Finalmente, se ha realizado una evaluación económica comparativa entre esta solución, una de autoconsumo y un sistema alimentado sólo con la red eléctrica, aplicadas a la climatización de dos granjas industriales localizadas en el norte de España. Esta evaluación muestra una gran rentabilidad económica de las bombas de calor fotovoltaicas. La solución autónoma permite reducir los costes de electricidad, no sólo en el término de consumo si no principalmente porque elimina el término de potencia, lo cual hace que la inversión de instalar un sistema fotovoltaico ofrezca una mayor rentabilidad económica que para un sistema de autoconsumo. La solución técnica aquí desarrollada y validada es especialmente relevante para aplicaciones industriales, donde sea factible alimentar directamente el compresor con el generador fotovoltaico a través de un variador de frecuencia. Ejemplos de aplicaciones de frío son la conservación de alimentos y medicinas, o el control de temperatura en procesos industriales. Además, esta solución también es válida para aplicaciones de calor de baja temperatura, como el secado de alimentos (cereales, productos cárnicos…). En definitiva, es viable para una gran cantidad de oportunidades de mercado

Economics of stand-alone large PV irrigation systems in the ECOWAS region.

Solar PV generators coupled to water pumps represent an attractive option for reducing the economic cost and the environmental impact associated to irrigation applications. Prior studies have already evaluated the technical and economic viability of PV water pumping, but they all refer to systems with relatively small PV nominal power (up to 30 kW). The European project MASLOWATEN has recently reported technical and economic validations for 5 large demonstrators (with PV powers in the range of 40-360 kWp) in the South of Europe, but these results are highly site-dependent and it would be interesting to extend them to other regions of the planet

Characterization of a stand-alone PV cooling/heating system

Recently, the environmental objectives set by the European Union to reduce CO2 emissions and to increase the renewable share, together with the reduction of PV prices since 2010, have motivated a great interest in PV heat pump systems for heating and cooling applications. This papers describes the initial characterization test and results of a stand-alone PV heat pump prototype installed in Madrid (Spain), using a water tank as thermal storage instead of batteries as electricity storage (a more expensive and technically complex solution). This initial test has the objective of characterizing the response of the converter that operates the compressor of the heat pump. Such converter was powered by a constant frequency input (the electric grid), in order to quantify the variable frequency output that the compressor demands. In future work, the converter will be powered by a PV array (which means a variable frequency input) and programmed to provide the required output without overcoming any limit value of the system. This way, the heat pump system will be operated completely stand-alone

Performance indicators of photovoltaic heat-pumps

In the last few decades, the demand for reversible heating and cooling systems has increased significantly, together with the need to generate energy in a more efficient and sustainable way. Consequently, the concept of solar photovoltaic (PV) powered heat pumps (HP) has become very attractive in order to match the heating/cooling demand with a renewable and environmentally-friendly energy source. This paper presents a review of the different solutions for PV-HP systems that have been studied theoretically and/or experimentally tested, and of the Key Performance Indicators (KPIs) that were mainly used. An analysis of these traditional KPIs has been performed and their boundaries were identified. As a result, new KPIs (PR25, PRref,25, SPFPV-HP and SPFPV-HP,ref,25) were proposed for trying to mitigate such limitations, as well as for evaluating not only the quality of the HP and the PV system, but also the quality of their integration and the renewable character of the whole PV-HP system. This paper is aimed to be framed in the common effort of the PV-HP research community to reach a set of KPIs that allow comparing the different future works and, therefore, a set of recommendations and future research lines are also proposed

Technical evaluation of a stand-alone PV heat pump system for space heating/cooling applications without batteries

In the last years, the concept of solar photovoltaic (PV) powered heat pumps (HP) has become very attractive, in order to match the increasing heating/cooling demand with a renewable and environmentally-friendly energy source. The objective of this work is to technically validate a stand-alone PV-HP system for space heating/cooling applications. This paper describes the prototype system installed in Madrid (Spain) for this purpose, together with the definition of the validation tests to be performed. Finally, some modifications are proposed for the performance indicators that are traditionally used for comparing HP and PV systems, in order to achieve a characterization that is more specific to PV-powered systems

Evaluación técnica de una bomba de calor fotovoltaica autónoma sin baterías

El objetivo de este trabajo es efectuar la evaluación técnica de una bomba de calor fotovoltaica, autónoma y sin baterías. Para ello, se ha instalado un prototipo de pequeña potencia (bomba de calor de 1,5 kW y un generador FV de 2,2 kW) en Madrid (España) y se han realizado unos ensayos de caracterización. En este artículo se describe dicho prototipo y se muestran brevemente los resultados de los primeros ensayos. Finalmente, se proponen unos indicadores de rendimiento específicos para bombas de calor fotovoltaicas (PRBC-FV, COPBC-FV y EERBC-FV), adaptando los indicadores utilizados tradicionalmente. Abstract: The objective of this work is to perform the technical evaluation of a photovoltaic heat pump system, operating stand-alone and without batteries. For achieving this purpose, a small-power prototype (heat pump of 1.5 kW and PV generator of 2.2 kW) has been installed and characterized in Madrid (Spain). In this paper, such prototype is described and the results of the preliminary characterization tests are shown. Finally, specific performance indicators are proposed for evaluating PV heat pump systems (PRBC-FV, COPBC-FV y EERBCFV), modifying the traditional ones

Evaluación técnica de una bomba de calor fotovoltaica autónoma sin baterías

El objetivo de este trabajo es efectuar la evaluación técnica de una bomba de calor fotovoltaica, autónoma y sin baterías. Para ello, se ha instalado un prototipo de pequeña potencia (bomba de calor de 1,5 kW y un generador FV de 2,2 kW) en Madrid (España) y se han realizado unos ensayos de caracterización. En este artículo se describe dicho prototipo y se muestran brevemente los resultados de los primeros ensayos. Finalmente, se proponen unos indicadores de rendimiento específicos para bombas de calor fotovoltaicas (PRBC-FV, COPBC-FV y EERBC-FV), adaptando los indicadores utilizados tradicionalmente. Abstract: The objective of this work is to perform the technical evaluation of a photovoltaic heat pump system, operating stand-alone and without batteries. For achieving this purpose, a small-power prototype (heat pump of 1.5 kW and PV generator of 2.2 kW) has been installed and characterized in Madrid (Spain). In this paper, such prototype is described and the results of the preliminary characterization tests are shown. Finally, specific performance indicators are proposed for evaluating PV heat pump systems (PRBC-FV, COPBC-FV y EERBCFV), modifying the traditional ones

Uncertainties on the outdoor characterization of PV modules and the calibration of reference modules

This paper presents the IES-UPM experience in the outdoor characterization of PV modules. On days with clear sky conditions, a rather simple device consisting of a thermally-insulated wooden box allows the STC characteristics and the thermal coefficients of PV modules to be measured with low expanded uncertainty (±1.87% in power (k = 2)). Particular attention has been paid to the calibration of the reference cell used for measuring the irradiance and making our measurements traceable to the International System of Units (S.I.). Furthermore, the uncertainty on the irradiance and module temperature measured by the reference PV modules calibrated with the help of this box has also been analyzed in relation to the angle of incidence of the direct irradiance. We think this experience is particularly interesting for local measurements in many countries currently incorporating PV plants in their electric grid, but lacking in specialized PV laboratories equipped with expensive solar simulators