• Energy Research

The behavior of a photovoltaic (PV) panel submerged in water is studied. A sizeable increase of electric power output is found for shallow water. Experiments have been carried out for single crystalline silicon panels. Results are discussed and the increase in efficiency is investigated and understood. Operating problems are analyzed and the advantages of using underwater solar panels are pointed out.

Abstract A photovoltaic panel with a heat extraction system is studied. The solution we suggest consists in superimposing a water layer on the PV panel: the water layer absorbs the infrared radiation leaving the visible part almost unaffected. This allows a good PV efficiency and heat production. This particular setup is called Thermal Electric Solar Panel Integration (TESPI) and it is discussed in detail both for the electric and the thermal part. The engineering problems are briefly analyzed and results of an experimental campaign are given. A definition of the global thermal-electric efficiency is given.

The integration of floating a PV plant (FPV) with a Hydroelectric Power plant (HPP) is studied and it is shown that several advantages come from this hybridization. The FPV power potential is analysed for the first 20 largest HPPs in the world and it is shown that when covering 10% of the HPP basin surfaces the HPP energy production is increased by 65%. The experience of China Longyangxa basin and of its connected PV power plant is examined together with the suggestion to install a FPV whose rated power is equal to HPP rated power. This hypothesis is applied to an analysis of the geographic potential worldwide and it is shown that covering 2.4% of the existing HPP basin surfaces the energy produced by HPP will be increased by 35.9%. The advantages of the coupling of the two power production technologies are discussed.

Abstract In isolated or weakly connected power systems, the maximum exploitation of renewable intermittent energy sources can be obtained by means of cost-effective storage technologies. In this paper hydroelectric gravity storage is extended to the deep ocean context. A sturdy cavity full of water is submerged at great depth and the hydraulic work carried out when emptying it and recovered when filling it, constitutes the storage system. The possibility of using this technique, named DOGES: Deep Ocean Gravitational Energy Storage, as well as its costs and technical aspects are discussed. Atolls and oil platforms supplied with floating Photovoltaic (PV) or wind systems connected to DOGES are also discussed.

Abstract Solar energy can be used to produce thermal energy, by means of thermal solar panels and electrical energy, using photovoltaic (PV) modules. In urban and suburban areas, because of a limited number of surfaces apt for installation of solar systems, the full development of both technologies can be limited. The integration of solar, thermal, and PV modules into a single unit, the so-called photovoltaic thermal (PV-T) module, could be a possible solution to generate electrical energy and heat simultaneously on the same surface. Many technical solutions are currently available; however, in this study, the analysis is limited to liquid-cooled nonconcentrating PV-T collectors where c-Si cells are used. In particular, the experimental results of two pilot plants, based on patented panels, named TESPI – thermal electric solar panel integration, are presented. The main advantage of these modules is that they represent a retrofit of existing PV plants. In fact, they can be installed on top of conventional PV modules as they are based on the infrared filtering effect of water on solar radiation. A standard test for hybrid PV-T systems for developing new solutions and measuring their performance was designed. In order to improve the design of modules and check their behavior in typical domestic hot water systems, two different PV-T solutions, but with identical PV modules, were analyzed without the heat transfer system. The prototypes are made of two systems (PV and PV-T) installed on two Italian sites, Enna (Sicily) and Pisa (Tuscany), characterized by typical Mediterranean climate. In this study, PV-T systems were analyzed at a PV string level. Different operating conditions were tested and electrical and thermal critical operating conditions were detected.

Abstract Roundabouts became popular worldwide as a tool to reduce the number of car accidents and the EU encourages and promotes this technology as a solution to the problems of urban and extra-urban traffic. RAST (Roundabout Solar Tracking) systems are designed to exploit the available space in roundabouts, which are already equipped and monitored, in order to produce electricity with a photovoltaic single axis tracking system. The energy produced can be used directly by the surrounding facilities or stored and consumed later or channelled to nearby car charge points. The amount of energy that can be produced on a single roundabout is limited by the land size and is normally in the range 100-400 kWp, but the number of suitable roundabouts in cities is high. Therefore, RAST could make an important contribution to the energy production.

The possibility to use photovoltaic (PV) modules under a water layer has been explored under different forms: submerged, covered by a water layer, and under a transparent box that contains water. All these test conditions have in common the use of water as a filter for solar radiation to reduce the warming of the PV cells. The effect of the change of the solar spectrum impinging on the PV cells depends highly on the PV technology. A numerical analysis to evaluate the photoelectric efficiency of different PV cells under water is given. Further indoor experimental measurements of PV cells stroked by the artificial light of a halogen lamp that passes through the water-flow-lens (WFL) system are also presented. The connection between the band gap, intensity of light, and distribution of light for a different approach for filtering solar radiation is discussed. The influence of light intensity, halogen spectrum, as well as the WFL system used and their influence on the short-circuit current ( I SC) and the open-circuit voltage ( V OC) are also investigated.

This paper elaborates different hybrid energy scenarios for applications in small or medium residential building facilities in typical Mediterranean climate conditions. Proposed hybrid energy solutions are based on the split air conditioning units as they are the most used individually energy sources able to cover heating and cooling demands in residential building facilities in considered climate conditions. Four different hybrid energy options have been analysed as they represent highly efficient energy solutions that could reduce overall energy consumption as well as also carbon dioxide emissions from residential sector. For each proposed energy solution a technical aspect was addressed, as well as also an economic aspect through obtained LCOE analysis. Therefore, the proposed and analysed hybrid energy concepts turned out to be a viable energy solution for residential applications as calculated LCOE was competitive with current retail prices of electricity on the EU market. The calculated LCOE ranged from 0.036 €/kWh up to 0.159 €/kWh, depending from the considered hybrid energy solution. The solution with the modified split heat pump system turned out to be most favourable. However, as each solution is characteristic one an additional evaluation framework was developed. Finally, the results of this study could be useful as examples of good practice as well as also a useful guidance for policy makers.

Abstract The Venetian Villas are an historic body of 3782 buildings in Veneto and Friuli from the XVI century to the XVIII century. UNESCO has certified 24 villas of Andrea Palladio as World Heritage Sites. The Regional Institute for the protection of these sites has launched a competition to find innovative technological solutions that contribute to the energy needs of the villas without interfering with the architectural and landscape quality of the same. The paper illustrates the technological solution that won the competition. The possibility of powering the historical Venetian Villas with renewable energy sources is explored. The realization of submerged PV plants integrated with existing water basin is suggested as the best solution. Energy yield is adequate and landscape quality is conserved. Technical details and architectural layouts are discussed.