The renewable energy potential of the Maltese Islands

The potential of renewable energies is presented for the territory of the Republic of Malta. These are in the main sun, wind and biogas. Taking the base year 2003 for comparing the percentage contribution of electricity generated from renewables to that generated from fossil-fuelled power stations, it was found that rooftop solar photovoltaic systems could produce 9.1%, onshore wind farms could offset 5.4% and the offshore wind potential lies in the region of 3.4%. Energy from waste could contribute another 5.6%, while widespread solar water heating in domestic buildings could offset 4.8%. Economic analysis of applying renewable energy power systems under the present constraints is carried out. A range of barriers to the use of renewable energy devices is described. The currently available incentives are listed and a number of measures that could be implemented to allow widespread applications of renewable energies are suggestedpeer-reviewe

Increasing the value of offshore wind by integrating on-board energy storage

Energy storage technologies are considered a promising solution for overcoming one of the most pertinent hurdles to high renewable energy penetration: the mismatch between energy supply and consumer demand. The intermittent nature of variable renewable energy technologies at high penetration rates leads to a loss of value for each unit of energy produced. Generationside energy storage can allow wind turbines to alter their generation strategies and derive additional value through improved market participation. On-board storage leads to more efficient use of space and a potential for cost reductions. In the present work, a brief review of existing work on these aspects was undertaken, followed by a time-series analysis of an offshore 6 MW wind turbine coupled to an energy storage system. The performance of the wind+storage system was simulated using one year of data from the Egmond aan Zee offshore wind farm site. A statistical analysis was undertaken to estimate the required charge/discharge cycles and establish the required storage capacity under different operating conditions. A lithium-ion battery was then considered as the competing energy storage technology, and a cumulative damage model was applied based on the depth-of-discharge characteristics. Findings indicate that despite their competitive capital costs, battery technologies would have a limited lifetime resulting from high charging/discharging cycles. A more viable approach in the long-term could be to opt for technologies that are less dependent on charge/discharge cycles and which have a lifetime that can match that of the wind turbine itself.peer-reviewe

The Eco-Gozo concept : from a sustainable energy perspective

The Eco Gozo 2015 Vision of the Ministry for Gozo aims at making the Island of Gozo eco-friendly, supporting a sustainable society, while improving the quality of life of citizens and reducing the Island’s carbon footprint [1]. This paper aims at addressing the Eco-Gozo Concept from a sustainable energy point of view. Gozo, being a small island that fully depends on the main Island of Malta for the provision of energy supplies and electricity, would have to become more self-sufficient in terms of renewable energy generation, thus reducing power transmission losses and its associated carbon emissions, and increasing the island’s autonomy and energy diversification. Studies showed that for the immediate future, there is a good potential for the use of solar and wind energy systems on the island. The use of bio-energy and alternative fuels for vehicles would increase energy options for transport fuel, and in the longer run, there might be possibilities for using wave energy for electricity production. The paper also shows significant savings that could be achieved by applying roof insulation to buildings. Although the paper has not exhaustively dealt with all energy saving, energy efficiency and renewable energy options, the results presented here should be useful to all entities who may be directly or indirectly involved in planning for the Eco-Gozo initiative, and may also support the formulation of sustainable action plans that would be necessary to achieve the full aims of the Eco-Island concept. This study also showed that the Island of Gozo could potentially even become a net exporter of green electricity.peer-reviewe

Wind monitoring on the island of Gozo

This research article reports salient wind characteristics resulting from field work carried out on one of the islands in the Maltese archipelago. Wind data gathered at Kerċem on the island of Gozo was processed using two analytical methods and the results were compared in order to present an indicative snapshot of this location’s wind conditions. The average wind speeds at 10 metres and 18 metres above ground level were 4.92 m/s (average power density of 143 W/m2) and 5.90 m/s (average power density of 244 W/m2) respectively for a 30 calendar month time frame. Records indicated a predominant wind blowing from the West North West (between 285° and 315°) that was independent of the period of the year. Seasonal and diurnal variations were also assessed in order to provide a basis for wind turbine energy production estimates. These findings should throw more light on site-specific wind conditions on this small central Mediterranean island.peer-reviewe

Analysis of a novel offshore platform with integrated energy storage operating in Central Mediterranean waters

A thermodynamic model of a novel energy storage device is described and simulated in the context of a central Mediterranean climate. The device uses a hydro-pneumatic concept to store energy as compressed air. It is designed to be integrated into an offshore floating platform. The thermodynamic model illustrates the behaviour of the compression process and the heat exchange with the surrounding environment. Different rates of compression are simulated, and it can be observed that faster compression rates lead to higher gas temperatures and pressures. The sensitivity to climatic conditions is also investigated, however this effect was seen to be minimal. A simplified Black-Box Model is also developed, with its parameters obtained through a curve-fitting process. Finally, a stochastic input is fed to both models and a comparison is made. The simplified model results in a minor over-prediction of the efficiency.peer-reviewe

Validation of wind measurements from a multirotor RPAS-mounted ultrasonic wind sensor using a ground-based LiDAR system

The aim of this research was to establish the validity of wind measurements from on board a multirotor Remotely Piloted Aircraft System (RPAS) for the purposes of wind monitoring applications. A custom-built hexacopter RPAS recorded wind speed and direction by means of an onboard ultrasonic wind sensor, whilst operating in the inherently highly stochastic nature of open field atmospheric conditions. Experimental data were collected during open field hovering flights subject to different ambient conditions with free stream horizontal wind speeds reaching up to 12 m/s. Flights were conducted at different altitudes above ground level and in proximity to a Light Detection and Ranging (LiDAR) remote wind measurement unit that was used as a low-resolution reference meteorological station. Very good correlation was obtained between the RPAS and LiDAR unit for both wind speed and wind direction measurements across all hovering flight altitudes. The RPAS-based wind speed measurements were found to have a consistent 1 m/s positive offset, whilst the RPAS-based wind direction readings had a 6.16◦ negative offset. These were potentially caused by differences in the localized wind fields between the LiDAR and RPAS measuring positions, as well as by localized RPAS rotor-induced air flows for wind speed measurements and potential slight misalignments in the instruments’ reference datum for wind direction readings.peer-reviewe

Cost modelling of floating wind farms with upscaled rotors in Maltese waters

The technical viability of offshore wind projects depends upon a number of factors such as the site-specific wind resource, sea depth, seabed composition, distance to the shore and climatic conditions amongst others. The Mediterranean is characterised by deep seas relatively close to the shore and only a reasonable wind climate if compared to conditions in countries that are forerunners in the offshore wind sector. The development of floating wind turbine support structures will allow wind farms in deeper waters and will be a catalyst for the wider diffusion and larger-scale implementation of offshore wind farms on a global level. This study investigates the prospects for a hypothetical 100 MW floating offshore wind farm well to the west of the island of Malta. The study models three upscaled turbines having rotor diameters of 126, 145 and 170 m. The study shows that the rotor upscaling process can improve the economic viability of offshore wind turbines with the improved energy yield counterbalancing the higher investment costs required for such a project and thus resulting in a lower cost of energy. The levelised cost of electricity is estimated to be in the 21.0 to 23.6 €cent/kWh range which, although still well above the current market prices of electricity generated by conventional means, is expected to drop considerably over the coming years as new international players enter the offshore wind market. Increasing levels of competition, new concepts coming to fruition and wider and larger-scale diffusion of new technologies will help bring down costs of energy for the offshore wind farms of the future.Bajada New Energy, General Membrane, EcoGroup, Econetique, Energy Investment, JMV Vibro Blocks, Solar Engineering, Solar Solutionspeer-reviewe

Analysis of a novel offshore platform with integrated energy storage operating in Central Mediterranean waters

A thermodynamic model of a novel energy storage device is described and simulated in the context of a central Mediterranean climate. The device uses a hydro-pneumatic concept to store energy as compressed air. It is designed to be integrated into an offshore floating platform. The thermodynamic model illustrates the behaviour of the compression process and the heat exchange with the surrounding environment. Different rates of compression are simulated, and it can be observed that faster compression rates lead to higher gas temperatures and pressures. The sensitivity to climatic conditions is also investigated, however this effect was seen to be minimal. A simplified Black-Box Model is also developed, with its parameters obtained through a curve-fitting process. Finally, a stochastic input is fed to both models and a comparison is made. The simplified model results in a minor over-prediction of the efficiency.peer-reviewe