First-hand experience of solar photovoltaic grid-connection in Malta

The paper presents the design, set-up and commissioning of the first grid-connected solar photovoltaic system in Malta. Some preliminary results are also included. The aim of this project was to study the state-of-affairs of such systems when they are interfaced with the local electricity grid. This would lead to a better understanding of such interfaces thus enabling the formulation of definite policies and guidelines in preparation for the wide-spread application of such systems in the near future.peer-reviewe

Performance of a 1.2 kWp stand-alone photovoltaic system in Malta

The paper presents the results of the performance of a 1.2 kWp stand-alone photovoltaic (PV) system under local conditions, during two years of operation. The sizing and construction of the system were described elsewhere. This is the first PV system to be tested locally. Monitoring and analysis of data as well as presentation of results were performed in accordance with the guidelines set by the Joint Research Centre - Ispra Establishment. The mean daily PV energy production was 3.034 kWh/kWp/day and the mean final yield was 1.89 kWh/kWp/day, with a performance ratio of 0.37. Empirical equations relating the power produced to solar radiation are presented for future use. The accumulation of dust on the PV modules during summer did not contribute to more than 2% drop in power production while wind speeds higher than 2 m/s had a cooling effect on the PV modules. The major causes for drop in efficiency were shading and the deviation of the performance from the maximum power curve, caused by the accumulation of electric charge in the storage batteries.peer-reviewe

Analysis of photovoltaic projects in a Mediterranean island

The paper presents an analysis of the four grid-connected systems installed in Malta and monitored by the Institute for Energy Technology of the University of Malta. The systems have varying power ratings, orientation and tilts. Three systems had stationary solar modules, while the fourth one used an active tracking device. The purpose of this study was to evaluate the performance of different systems under the local weather conditions of a typical Mediterranean country. Comparison to other systems in EU countries was made and answers to frequently asked questions were found. The mean monthly Performance Ratio of the systems ranged between 0.51 and 0.80, while the final yield was reported to be between 2.76kWh/kWp/day and 3.61kWh/kWp/day. The final efficiency was also found to be between 5.1% and 7.1%. This compared favourably with results reported by European researchers such as in the Thermie Project. The inverters proved to be safe and did respond as expected during times of grid disturbance. In view of Malta’s new membership in the European Union, this study will be an essential tool to support future widespread applications of solar electric systems in Malta.peer-reviewe

Hybrid and Intelligent Energy Storage Systems in Standalone Photovoltaic Applications.

Remote systems such as communication relays or irrigation control installations cannot usually be powered by the electrical grid. One of the alternatives is to power these systems through solar panels, in what is known as standalone photovoltaic applications.Most of these systems need a continuous operation, but a standalone photovoltaic installation cannot be powered during the night. For this reason, they use batteries to store excess energy during the day. These storage systems have been traditionally based on Valve Regulated Lead Acid (VRLA) batteries, but some effects can alter their performance in terms of reliability, operation cost and maintenance. One of the key issues that alter the energy behavior of the photovoltaic off-grid systems is the Partial State of Charge (PSoC) effect: Batteries cannot be completely charged as manufacturers indicate due to the day-night cycle. This gets the battery into an intermediate state of charge that effectively reduces its capacity, even halving it in some cases. To mitigate the impact of these effects on the installation, batteries tend to be oversized with some security margins. These oversizing factors can be incredibly high and have a huge impact on the deployment and maintenance cost of the facility.The first part of this thesis highlights some of these key concepts, analyzing which of them are critical in specific design cases, modeling them into a simulation tool, and as an outcome, establishing optimal sizing regions for the installations. After the analysis, different ways of improving the performance of the installations are proposed. One idea to mitigate PSoC is to combine different storage technologies in a Hybrid Energy Storage Systems (HESS). HESSs have traditionally combined high energy density elements as batteries with high power density elements as ultracapacitors. An iteration of this idea is carried out throughout this thesis, where different types of batteries are combined. Each of them is best fitted to different power patterns in the application, such as daily cycles or emergency periods. It is possible to further increase the performance by using intelligent algorithms to improve the functionalities of the Battery Management Systems embedded in these applications. To this end, failure prediction and health estimation algorithms are proposed as contributions of this work. These new algorithms endow the HESS with tools to predict possible energy disruption events and to anticipate aging, and thus, act accordingly.<br /

An operational bidding framework for aggregated electric vehicles on the electricity spot market

Fluctuating electricity prices offer potential economic savings for the consumption of electricity by flexible assets such as Electric Vehicles (EVs). This study proposes an operational bidding framework that minimizes the charging costs of an EV fleet by submitting an optimized bid to the day-ahead electricity market. The framework consists of a bidding module that determines the most cost-effective bid by considering an electricity price and an EV charging demand forecast module. In this study we develop and evaluate several regression and machine learning models that forecast the electricity price and EV charging demand. Furthermore, we examine the composition of a most optimal operational bidding framework by comparing the outcome of the bidding module when fed with each of the forecast models. This is determined by considering the day-ahead electricity price and imbalance costs due to forecast errors. The study demonstrates that the best performing self-contained forecast models with the objective of electricity price and EV charging demand forecasting, do not deliver the best overall results when included in the bidding framework. Additionally, the results show that the best performing framework obtains a 26% cost savings compared to a reference case where EVs are charged inflexibly. This corresponds to an achieved savings potential of 92%. Consequently, along with the developed bidding framework, these results provide a fundamental basis for effective electricity trading on the day-ahead market

The UK solar energy resource and the impact of climate change

AbstractSolar energy use in the UK is increasing dramatically, providing both heat energy and generation of electricity. This trend is expected to continue due to solar technologies becoming cheaper and more readily available along with low carbon government legislation such as the Renewable Heat Incentive (RHI) and Feed in Tariffs (FiTs) supporting solar energy deployment. However, the effects of climate change on the solar resource remain largely unstudied. Climate change affects cloud cover characteristics and consequently directly affects the performance of solar energy technologies.This paper investigates the UK solar irradiation resource for both the present and future climates.The present solar irradiation level was assessed through the conversion of 30 years of observed historical monthly average sunshine duration data. The method and results are validated by comparing the converted solar irradiation levels to actual solar irradiance measurements at weather stations with significant historical records of solar irradiance data.The impact of climate change is investigated across different regions of the UK by using the UKCP09 probabilistic climate change projections.We find that the current average UK annual solar resource is 101.2 Wm−2, ranging from 128.4 Wm−2 in the south of England to 71.8 Wm−2 in the northwest of Scotland. It seems likely that climate change will increase the average resource in the south of the UK, while marginally decreasing it in the Northwest. The overall effect is a mean increase of the UK solar resource, however it will have greater seasonal variability and discrepancies between geographical regions will be reinforced

Solar polar orbiter : a solar sail technology reference study

An assessment is presented of a Solar Polar Orbiter mission as a Technology Reference Study. The goal is to focus the development of strategically important technologies of potential relevance to future science missions. The technology is solar sailing, and so the use of solar sail propulsion is, thus, defined a priori. The primary mission architecture utilizes maximum Soyuz Fregat 2-1b launch energy, deploying the sail shortly after Fregat separation. The 153 × 153 m square sail then spirals into a circular 0.48-astronomical-unit orbit, where the orbit inclination is raised to 90 deg with respect to the solar equator in just over 5 years. Both the solar sail and spacecraft technology requirements have been addressed. The sail requires advanced boom and new thin-film technology. The spacecraft requirements were found to be minimal because the spacecraft environment is relatively benign in comparison with other currently envisaged missions, such as the Solar Orbiter mission and BepiColombo

Solar Irradiance Ramp Forecasting Based on All-Sky Imagers

Solar forecasting constitutes a critical tool for operating, producing and storing generated power from solar farms. In the framework of the International Energy Agency’s Photovoltaic Power Systems Program Task 16, the solar irradiance nowcast algorithms, based on five all-sky imagers (ASIs), are used to investigate the feasibility of ASIs to foresee ramp events. ASIs 1–2 and ASIs 3–5 can capture the true ramp events by 26.0–51.0% and 49.0–92.0% of the cases, respectively. ASIs 1–2 provided the lowest