A novel renewable polygeneration system for a small Mediterranean volcanic island for the combined production of energy and water: Dynamic simulation and economic assessment

This paper investigates the integration of solar and geothermal energy in a novel polygeneration system producing simultaneously: electricity, thermal energy, cooling energy and fresh water. The polygenera- tion system under analysis includes concentrating photovoltaic/thermal solar collectors (CPVT), a Geothermal Well (GW) a multi-effect distillation (MED) system for seawater desalination, a single-stage LiBr–H2O absorption chiller and additional components, such as: storage tanks, heat exchangers and balance of plant devices. The CPVT produces simultaneously electrical energy and thermal energy, at a maximum temperature of about 100 °C. The electrical energy is delivered to the grid, whereas the ther- mal energy can be used for different scopes. First, the thermal energy can be used for heating purposes and/or Domestic Hot Water production. As an alternative, solar thermal energy can be used to drive an absorption chiller, producing chilled water for space cooling. Finally, solar energy, in combination with the thermal energy produced by low-enthalpy (about 80 °C) geothermal wells, may be used by the MED system to convert seawater into desalinated water. Geothermal energy is also used to produce Domestic Hot Water at 45 °C. The system is dynamically simulated by means of a zero-dimensional transient simulation model. The simulation model also includes detailed control strategies, for the man- agement of the different technologies included in such a complex system. The system is assumed to be operated in some of the several small volcanic islands in the Mediterranean Sea, assuming Pantelleria (Trapani, Italy) as main case study. Here, the availability of solar and geothermal energy is high whereas the availability of fresh water is scarce and its cost consequently high. Results show an excellent ener- getic performance of the system under investigation. From the economic point of view, the profitability of the system dramatically increases when user Domestic Hot Water demand is high

Technical and ecnomic analysis of a cogeneration plant fuelled by biogas produced from livestock biomass

AbstractThis technical report illustrates an anaerobic digestion plant for the production of biogas designed to be powered by livestock biomass, combined with a 330 kWe CHP unit co-generator, installed in a cattle farm located in the province of Reggio Emilia. The plant consists essentially of a pre-treatment system of the effluents to the load, two anaerobic continuously stirred tank reactors and heated under mesophilic regime sheltered with gasometric coverings with double membrane; at the end of the process of fermentation, the digestate converges in a solid-liquid separation system with helical compression and a storage tank of the clarified fraction, sheltered with a covering for the containment of residual gaseous emissions into the atmosphere. The produced biogas is collected in gasometers placed above the tanks and, after desulfurization, dehumidification and cooling, it fuels the co-generator. The report is determined to illustrate the experimental results for the first 12 months of operation of the plant that confirmed, both in terms of energy and from a financial perspective, the efficiency of biogas plants fueled only by livestock effluents

Thermal integration of a SOFC power generator and a Na–NiCl2 battery for CHP domestic application

In this study the integration of a Solid Oxide Fuel Cell (SOFC) prime mover and a high temperature electrochemical Sodium Nickel Chloride (SNC) battery as storage has been investigated. The aim is to fulfil a domestic user energy demand and to reduce the primary energy consumption in comparison with a reference conventional scenario, thereby, to enhance the total efficiency in a Î1⁄4-CHP (Combined Heat and Power) application on a yearly basis. A realistic operational sequence of the SOFC-battery integration has been calculated using simple logic conditions. Both thermal and electric integration have been considered, where the innovative thermal integration has been proposed in order to exploit the SOFC residual heat for the battery stand-by feeding. The key advantage of this system architecture is that the SOFC is operated without major load variations close to constant load, resulting in longer lifetime and thus reducing total costs of operation. The thermal integration provides additional advantages, as calculated in this study. Eventually, a comparison with alternative Î1⁄4-CHP technologies has been carried out, highlighting the potential of the system based on the SOFC. Benefits are mainly shown in terms of primary energy savings and admissible costs