Impact of Small-scale Storage Systems on the Photovoltaic Penetration Potential at the Municipal Scale

AbstractHigh penetration of grid-connected roof-top photovoltaic power plants (GCRT-PV) is restricted by electric energy grid quality requirements and available storage capacities. This study evaluates how far small-scale storage systems can contribute to increment GCRT-PV penetration at municipal scale. To accomplish this, the GCRT-PV potential of a municipality is calculated in high spatiotemporal resolution and various scenarios of storage systems penetration are evaluated with a series of indicators. The adoption of a low share of storage systems improves energy utilisation, variability and reliability indicators; while an increased penetration of storage systems only marginally improves these indicators

Simulation of long-term time series of solar photovoltaic power: is the ERA5-land reanalysis the next big step?

Modelling long time series of photovoltaic electricity generation in high temporal resolution using reanalysis data has become a commonly used alternative to assess the viability of systems with high shares of renewables, their risks of failure and probability of extreme events. While there is a considerable amount of literature evaluating the accuracy of the original solar radiation and temperature variables in these data sets, the validation of the calculated output of photovoltaic installations is scarce and usually limited to locations in Europe. This work combines the new ERA5-land reanalysis data set and PV_LIB to generate hourly time series of photovoltaic electricity generation for several years and validates the results using individual data of 57 large photovoltaic plants located in Chile. Results are also compared with PV output for these locations calculated using renewables.ninja, a platform relying on MERRA-2, a global reanalysis with five times lower spatial resolution. Accuracy and bias indicators are satisfactory for plants that do not present severe anomalies in their generation profiles and where basic plant characteristics such as size and orientation match our model assumptions. However, the improvements in indicators over results obtained with renewables.ninja from MERRA-2 are minor. The validation process serves not only to confirm the suitability of the proposed workflow to model the output of individual photovoltaic plants, but also to list and discuss data quality and availability issues. Efforts towards availability and standardization of data of individual installations are necessary to improve the basis for further developments.Comment: 16 pages, 6 figures, 3 Tables, Annex A and B with 1 additional table and 2 figure

Simulation of multi-annual time series of solar photovoltaic power: Is the ERA5-land reanalysis the next big step?

The simulation of multi-annual time series of photovoltaic electricity generation in high temporal resolution using reanalysis data has become a common approach. These time series are crucial to assess the viability of electricity systems with high shares of variable renewable generation. Our work combines the new ERA5-land reanalysis data set and PV_LIB to generate hourly time series of photovoltaic electricity generation for several years and validates the results using individual data of 23 large photovoltaic plants located in Chile. We use a clustering algorithm to differentiate between fixed and tracking systems, as meta-information on installation type was not available. Results are compared with photovoltaic output for these locations calculated using MERRA-2, a global reanalysis with five times lower spatial resolution, which is one established source for modelling photovoltaic generation time series. Accuracy and bias indicators are satisfactory for all plants, i.e. correlations are above 0.75 for all installations and above 0.9 for more than half of them, while the mean bias error is between -0.05 and 0.1 for all instalations. However, the improvements in simulation quality over results obtained with MERRA-2 are minor. From our assessment of generation data quality, we conclude that efforts towards availability and standardization of data of individual installations are necessary to improve the basis for future validation studies

Is social cohesion decisive for energy cooperatives existence? A quantitative analysis

Energy Cooperatives (ECoops), the most prominent example for Energy Communities, are attributed great importance for the energy transition both through the engagement of energy end-consumers and the increase of local renewable energy sources. We conducted an exploratory (spatial) data analysis to study which indicators of the European Social Progress Index and Quality of Life Index co-occure with the presence of ECoops. Results show that these indexes and most of their sub-components present values significantly better at the regions where the ECoops are located compared to all EU regions. While correlation and regression coefficients between the number of ECoops per region and the indexes are relatively small, the individual indicator “Life-long learning” reaches the highest correlation and explanatory values. Additionally, Global moran statistics show that the concentration of ECoops and their relation to the indexes in space are rather random but a local analysis shows clusters emerging throughout the continent

Comparación de fuentes satelitales, de re-análisis y métodos estadísticos para el mapeo de la radiación solar en el Valle de Lerma (Salta-Argentina)

La radiación solar global es el factor más importante para la determinación del potencial de producción de energía de plantas fotovoltaicas y otras aplicaciones de energía solar. En la Argentina los datos de radiación solar global medidos en tierra son escasos o inaccesibles para el público en general. En muchos casos se recurre a métodos estadísticos o imágenes satelitales para proporcionar un aproximado de la radiación solar global en alguna locación deseada en el país. En el presente trabajo se busca determinar una fuente de datos de radiación solar global para el valle de Lerma con la mejor resolución temporal y espacial posible. Con este fin se estudian los datos de radiación de re-análisis ERA-INTERIM del “European Centre for Medium-Range Weather Forecasts” (ECMWF) y los proporcionados por la “Land Surface Analysis Satellite Applications Facility” (LSA- SAF) que son generados a partir de imágenes de MeteoSat de segunda generación (MSG). Estos datos son comparados entre ellos, con mapas generados por técnicas estadísticas y mediciones de un piranómetro. Los resultados demuestran que los valores LSA-SAF presentan un mejor ajuste a las mediciones en terreno y por su alta resolución espacial y temporal se convierten en una alternativa satisfactoria para compensar la escasa disponibilidad de datos para el área de estudio.Global solar radiation is the most important factor to determine the energy generation potential of photovoltaic plants. In Argentina only a small number of ground measured data of global solar radiation exists. Researchers have to use statistical methods or satellite imagery to handle this lack of information and provide an estimation of solar global radiation in a certain location in the country. In this paper we explore global radiation data sources for the Valle de Lerma in order to define a data set for future studies of photovoltaic energy generation potential in the best possible spatial and temporal resolutions. We evaluate the global solar radiation data set from the ERA-INTERIM reanalysis provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Meteosat second generation (MSG) derived data set from the Land Surface Analysis Satellite Applications Facility (LSA-SAF). These are compared with each other, with maps generated using statistical methods and with data from a piranometer. The results show that the data from LSA-SAF fit better to the ground measurements. This together with a high spatial and temporal resolution makes the LSA-SAF data a satisfactory alternative to compensate the lack of global solar radiation data available for the study area.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES

Many Actors Amongst Multiple Renewables: A Systematic Review of Actor Involvement in Complementarity of Renewable Energy Sources

Although complementarity achieved by combining multiple renewable energy sources (RES) is an important method to increase shares of RES, it is often overlooked in policy prescriptions supporting an energy transition. Complementarity can be implemented by multiple actors, however there has been little attention to which actors are involved, and their roles. We conducted a systematic review to provide an overview of the state of academic literature on the topic of combinations of multiple RES and the involvement of multiple associated actors. The sample included 78 articles using a range of methodologies to analyze varying combinations of wind, solar, bioenergy, hydro, geothermal, and ocean energy, alongside combinations of traditional, new, and supporting energy actors. Studies included contextualized (location specific) agent-based, techno-economic, economic, business model, and qualitative analyses, and decontextualized reviews, agent-based, and optimization models. Multi-actor complementarity is being addressed by diverse disciplines in diverse contexts globally, across a range of geographic scales. The majority of studies focus on solar-wind, although more diverse RES combinations were found in contextualized studies. New actors usually participate alongside traditional system actors. More attention to supporting actors is required. Findings highlight the need for further research beyond the technical benefits of combining multiple RES, to explore the roles of various actors. This can be accomplished by incorporating more context in studies, for example, using the substantial existing body of data and research, and by including a greater range of RES combinations, and incorporating more perspectives of associated actors

Safe reinforcement learning for multi-energy management systems with known constraint functions

Reinforcement learning (RL) is a promising optimal control technique for multi-energy management systems. It does not require a model a priori - reducing the upfront and ongoing project-specific engineering effort and is capable of learning better representations of the underlying system dynamics. However, vanilla RL does not provide constraint satisfaction guarantees — resulting in various potentially unsafe interactions within its environment. In this paper, we present two novel online model-free safe RL methods, namely SafeFallback and GiveSafe, where the safety constraint formulation is decoupled from the RL formulation. These provide hard-constraint satisfaction guarantees both during training and deployment of the (near) optimal policy. This is without the need of solving a mathematical program, resulting in less computational power requirements and more flexible constraint function formulations. In a simulated multi-energy systems case study we have shown that both methods start with a significantly higher utility compared to a vanilla RL benchmark and Optlayer benchmark (94,6% and 82,8% compared to 35,5% and 77,8%) and that the proposed SafeFallback method even can outperform the vanilla RL benchmark (102,9% to 100%). We conclude that both methods are viably safety constraint handling techniques applicable beyond RL, as demonstrated with random policies while still providing hard-constraint guarantees

Evolutionary scheduling of university activities based on consumption forecasts to minimise electricity costs

This paper presents a solution to a predict then optimise problem which goal is to reduce the electricity cost of a university campus. The proposed methodology combines a multi-dimensional time series forecast and a novel approach to large-scale optimization. Gradient-boosting method is applied to forecast both generation and consumption time-series of the Monash university campus for the month of November 2020. For the consumption forecasts we employ log transformation to model trend and stabilize variance. Additional seasonality and trend features are added to the model inputs when applicable. The forecasts obtained are used as the base load for the schedule optimisation of university activities and battery usage. The goal of the optimisation is to minimize the electricity cost consisting of the price of electricity and the peak electricity tariff both altered by the load from class activities and battery use as well as the penalty of not scheduling some optional activities. The schedule of the class activities is obtained through evolutionary optimisation using the covariance matrix adaptation evolution strategy and the genetic algorithm. This schedule is then improved through local search by testing possible times for each activity one-by-one. The battery schedule is formulated as a mixed-integer programming problem and solved by the Gurobi solver. This method obtains the second lowest cost when evaluated against 6 other methods presented at an IEEE competition that all used mixed-integer programming and the Gurobi solver to schedule both the activities and the battery use

Sustainable Astronomy: A comparative Life Cycle Assessment of Off-grid Hybrid Energy Systems to supply large Telescopes

Purpose Supplying off-grid facilities such as astronomical observatories with renewable energy-based systems (RES) instead of diesel generators can considerably reduce their environmental impact. However, RES require oversized capacities to counter intermittency and comply with reliability requirements, hence shifting the environmental impact from operation to construction phase. We assess whether 100% RES scenarios are favorable from an environmental point of view, and discuss the trade-offs in systems with backup fossil generators versus 100% renewable ones. Methods In this comparative life cycle assessment (LCA), we study various RES supply systems to power a new telescope in the Atacama desert, Chile. We compare six setups, including 100% RES scenarios, namely photovoltaics (PV) with batteries and hydrogen energy storage; high-renewable scenarios, with fossil fuel power generation next to RES and storage; and a system combining PV with diesel generation. We base system sizing on a techno-economical optimization for the start of operation in 2030. Foreground data stem from recent life cycle inventories of RES components and 2030 electricity mix assumptions of production places. We assess environmental impact in the categories climate change, mineral resource depletion and water use. Results and discussion We find that 100% RES and high-renewable scenarios result in emissions of 0.077-0.115kg CO2e/kWh supplied, compared to 0.917kg CO2e/kWh in the reference case with solely diesel generation. 100% RES scenarios have a lower CO2e impact than high-renewable scenarios. However, the latter lower the mineral resource depletion and water use by about 27% compared to 100% RES scenarios. Applying hybrid energy storage systems increases the water use impact, while reducing the mineral resource depletion. Conclusions None of the six energy systems we compared was clearly the best in all environmental impacts considered. Trade-offs must be taken when choosing an energy system to supply the prospective off-grid telescope in Chile. We find high-renewable systems with some fossil generation as the better option regarding power reliability, mineral resource depletion and water use, while inducing slightly higher greenhouse gas emissions than the 100% RES scenarios. As remote research facilities and off-grid settlements today are mainly supplied by fossil fuels, we expect to motivate more multifaceted decisions for implementing larger shares of RES for these areas. To advance the LCA community in the field of energy systems, we should strive to incorporate temporal and regional realities into our life cycle inventories. To ease the path for upcoming studies, we publish this work’s inventories as detailed activity level datasets

Cogeneración en Chile: capacidades, desarrollo y perspectivas

En Chile, el proyecto de cogeneración más antiguo data de 1930 y operó hasta el año 1997. Sin embargo, pese a que la tecnología lleva introducida largo tiempo, pocos son los estudios que han analizado el potencial de CHP y su evolución. Un primer paso para el estudio del potencial del país es la creación de un catastro que incluya la capacidad instalada. El interés de este ejercicio radica en el potencial de integración de mayores cantidades de CHP en el sistema eléctrico con el objetivo de hacer frente a la intermitencia de fuentes de energía no convencionales. Además, las plantas CHP pueden ayudar a alcanzar los objetivos de eficiencia energética gracias a la posibilidad de los generadores de volcar a la red tanto la electricidad como calor no consumido en los procesos productivos. Sin embargo, para que esto ocurra es necesario el desarrollo de un marco regulatorio acorde a las capacidades y características de las plantas de CHP. El objetivo de este artículo es precisamente identificar las características de las instalaciones en industrias específicas, así como su evolución, con el objetivo de extrapolar los datos al resto de la economía y obtener un potencial de CHP para el país. Para ello, se han hecho consultas de catastros anteriores, así como entrevistas con empresas para conocer el estado actual del parque de plantas de CHP en el país.1997. However, although the CHP technology has been introduced for a long time, few studies have analysed its potential and evolution. The development of a cadastre that includes all installed capacity and their characteristics is the first step to analyse the country's potential. The importance of this exercise lies in the potential integration of greater CHP capacities in the electric system as a mean to address the intermittence of non-conventional energy sources. In addition, due to the possibility to transfer both the electricity and heat not consumed in the production processes into the grid, CHP plants can help achieve energy efficiency objectives. However, for this to happen it is necessary the availability of a regulatory framework designed according to the capacities and characteristics of the CHP capacities installed. This article aims to identify the characteristics of the CHP capacities in specific industries as well as their evolution during time, in order to extrapolate the data to the rest of the economy and obtain a CHP potential for the country. For this purpose, previous cadastres have been consulted and the information complemented with interviews with companies to know the current status of the CHP plants in the country.Asociación Argentina de Energías Renovables y Medio Ambiente (ASADES