This paper describes the study of the impact of energy absorption by wave farms on the nearshore wave climate and, in special, the influence of the incident wave conditions and the number and position of the wave farms, on the nearshore wave characteristics is studied and discussed. The study was applied to the maritime zone at the West coast off Portugal, namely in front of Sao Pedro de Moel, where it is foreseen the deployment of offshore wave energy prototypes and farms between the 30m and 90m bathymetric lines, with an area of 320Km2. In this study the REFDIF model was adapted in order to model the energy extraction by wave farms. Three different sinusoidal incident wave conditions were considered. Five different wave farm configurations, varying the position of the wave farm, its number and the width of the navigation channels at each wave farm were analysed. The results for each configuration in terms of the change of the wave characteristics (wave height and wave direction) at the nearshore are presented, compared and discussed for three representative wave conditions.

The impact of wave energy farms in the shoreline wave climate

Integrated electricity and gas system modelling with hydrogen injections and gas composition tracking

Wave-to-wire models of Wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea

The multi-chamber Oscillating Water Column (OWC) device has recently become more attractive due to its potential high efficiency. In this paper, the hydrodynamic performance of a single-, dual- and triple-chamber OWC-breakwater are investigated experimentally. In the first instance, quantitative comparisons are implemented to understand the hydrodynamic performance of multi-chamber OWC-breakwaters. Specific attention has been dedicated to the hydrodynamic performance of capture width ratio (CWR), reflection coefficient, transmission coefficient, dissipation coefficient and effective frequency bandwidth. The investigation identified various findings that can be summarized as follows: i) hydrodynamic interactions between chambers in the multi-chamber OWC device has improved wave power extraction characteristics; ii) comparing with the conventional pontoon breakwater, the multi-chamber OWC-breakwater showed better wave attenuation performance in longer waves; iii) wave steepness is important for evaluating the performance of the multiple-chamber OWC-breakwater device; and iv) the implementation of the multi-chamber scheme broadens the effective frequency bandwidth (satisfied the condition of KT   0.2) of OWC-breakwater.

Experimental investigation on the hydrodynamic performance of a multi-chamber OWC-breakwater

An engine drove by wave has a piston like device composed by an active cell and a stator relatively reciprocate moving in straight. The active cell composed by dozens of permanent magnet and magnetic conductor arrayed in SN-JS-SN-NSiiis inserted into a stator column which is formed by U shape coil set or T shape magnetic conductor ring. When wave drive the floating box moving up and down, the floating box drives the active cell moves reciprocating, the changing of the magnetic flux induced by the coil on the stator generates electricity. Vis-?n-vis, active cell composed by coil set and magnetic conductor ring with stator composed by permanent magnet and magnetic conductor work in the same way.

Wave activated generator

Steady-state analysis of a natural gas distribution network with hydrogen injection to absorb excess renewable electricity

Oscillating water column (OWC) systems are among the most credited solutions for an effective conversion of the notable energy potential conveyed by sea waves. Despite a renewed interest, however, they are often still at a demonstration phase and additional research is required to reach industrial maturity. Within this framework, this study provides a wave-to-wire model for OWC systems based on an impulse air turbine. The model performs a comprehensive simulation of the system to estimate the attendant electric energy production for a specific sea state, based on analytical models of the primary (fixed chamber) and secondary (air turbine) converters coupled with the tertiary converter (electric generator). A rigid piston model is proposed to solve the hydrodynamics, thermodynamics, and hydrodynamics of the chamber, in a coupled fashion with the impulse turbine aerodynamics. This is solved with a novel method by considering the cascades as sets of blades, each one consisting of a finite number of airfoils stacked in the radial direction. The model was applied for two Mediterranean sites located in Tuscany and Sardinia (Italy), which were selected to define the optimal geometry of the turbine for a specified chamber. For each system, the developed analytical wave-to-wire model was applied to calculate the performance parameters and the annual energy production in environmental conditions typical of the Mediterranean Sea. The selected impulse turbines are able to convert 13.69 and 39.36 MWh/year, with an efficiency of 4.95% and 4.76%, respectively, thus proving the interesting prospects of the technology.

/pdf/wave-to-wire-model-of-an-oscillating-water-column-wave-55vsalksaf.pdf

Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots

This paper presents an off-design analysis of a gas turbine Organic Rankine Cycle (ORC) combined cycle. Combustion turbine performances are significantly affected by fluctuations in ambient conditions, leading to relevant variations in the exhaust gases’ mass flow rate and temperature. The effects of the variation of ambient air temperature have been considered in the simulation of the topper cycle and of the condenser in the bottomer one. Analyses have been performed for different working fluids (toluene, benzene and cyclopentane) and control systems have been introduced on critical parameters, such as oil temperature and air mass flow rate at the condenser fan. Results have highlighted similar power outputs for cycles based on benzene and toluene, while differences as high as 34% have been found for cyclopentane. The power output trend with ambient temperature has been found to be influenced by slope discontinuities in gas turbine exhaust mass flow rate and temperature and by the upper limit imposed on the air mass flow rate at the condenser as well, suggesting the importance of a correct sizing of the component in the design phase. Overall, benzene-based cycle power output has been found to vary between 4518 kW and 3346 kW in the ambient air temperature range considered.

https://www.mdpi.com/1996-1073/13/5/1105/pdf

Off-Design Performances of an Organic Rankine Cycle for Waste Heat Recovery from Gas Turbines

The removal of heat from electronic components, increasingly miniaturized with high power dissipation per unit volume, is a significant industrial problem to be resolved, to avoid failures due to excessive temperatures and besides to maintain performance and operating conditions. This article describes the development of a one-dimensional thermodynamic model to simulate the cooling of electronic chips belonging to inverters for stationary PV solar arrays; these are typically located in very different environments, including deserts or very hot areas, so the operating life of theirs inverter units are strongly affected by changes in external environmental conditions. Results have shown that the model allows, with very low calculation times, to quantify the effects of cooling performance and thermal load of electronics both in design and off-design conditions: the working temperature of the components was monitored as the effectiveness of the main heat exchanger vary with the exposure to the external environment over time, in terms of fouling and as the ambient air temperature changes; in this case a simple control system was simulated to limit the maximum temperature of the chips and the air flow rate of the fans. The thermal performances of two types of glycol-based refrigerant fluids have been compared.

/pdf/modelling-and-analysis-of-a-liquid-cooled-system-for-thermal-1pzdlyi37v.pdf

Lapo Cheli

Papers

Steady-state analysis of a natural gas distribution network with hydrogen injection to absorb excess renewable electricity

Wave-to-Wire Model of an Oscillating-Water-Column Wave Energy Converter and Its Application to Mediterranean Energy Hot-Spots

Wave-to-wire models of Wells and impulse turbines for oscillating water column wave energy converters operating in the Mediterranean Sea

Off-Design Performances of an Organic Rankine Cycle for Waste Heat Recovery from Gas Turbines

Modelling and analysis of a liquid-cooled system for thermal management application of an electronic equipment