Special issue "Smart Urban Lighting Systems"

The design and operation of multifunctional infrastructures for public lighting as well as their impact on the urban environment and citizens' life is today of great interest. The cost of energy for public lighting is often an issue for the budget of municipalities. Furthermore, researchers' and designers' attention is increasingly focused on aspects of public lighting not directly valuable through economic factors. Starting from the "quality" of the light environment, looking at citizens' visual comfort, the light has to be considered as an instrument to improve the urban context and objects therein (including buildings). Indeed, urban degradation (lack of infrastructures, maintenance, services, etc.) is linked to the poor quality of everyday issues, such as traffic, pollution, noise, lack of information, long times to access focal points, and the lack of safety. Simultaneously, in many areas, the potential related to the valorization of historical heritage is often underexploited. The installation of efficient lighting systems coupled with the implementation of ICT solutions can provide economic, social, and health benefits, energy efficiency, and visual comfort. On the other hand, as for indoor lighting, these systems can be expensive, not easy to maintain, and not as efficient as expected. The aim of this Special Issue was to investigate the problems and advantages of smart urban lighting systems in more detail. This Special Issue included 6 papers of the 10 submitted papers

Numerical evaluation on performances of AHU equipped with a cross flow heat exchanger in wet and dry operation

In this paper the comparison between the performance of a cross flow heat exchanger in wet and dry operation for air handling process has been investigated. In addition, a case study of application of the component to perform indirect evaporative cooling in a AHU was studied with the software TRNSYS. Using experimental data and an appropriate analytical method, energy saving performances of the system has been evaluated through the entire cooling season for a typical Mediterranean site. Results show that high energy saving potential can be obtained if the component is operated in wet operation in term of reduction of electricity consumption

Comparison between the performances of daylight linked control system at two different latitudes

The aim of this work is to compare the performance of a daylight-linked control system installed and tested in two different case studies by means of a set of indices. The two case studies are characterized by different geometry, location and windows orientation. The first one is located at the ENEA premises in Lampedusa (IT, 35° 30' N); the second one is located in Palermo (IT, 38°6' N) on the third floor of the building 9 of the Department of Engineering if the University of Palermo. In both cases, the indices were calculated by using the same daylight-linked control system and the same end-use (office). The results were reported and analysed in order to demonstrate as the performances of the control system can be different from the ideal performance and that they can be different according to the installation. Furthermore, according to the first outcomes, it results that a detailed analysis of the space before the installation of the control system is a necessary practice

Short term wind speed prediction using Multi Layer Perceptron

Among renewable energy sources wind energy is having an increasing influence on the supply of energy power. However wind energy is not a stationary power, depending on the fluctuations of the wind, so that is necessary to cope with these fluctuations that may cause problems the electricity grid stability. The ability to predict short-term wind speed and consequent production patterns becomes critical for the all the operators of wind energy. This paper studies several configurations of Artificial Neural Networks (ANN), a well-known tool able to estimate wind speed starting from measured data. The presented ANNs, t have been tested through data gathered in the area of Trapani (Sicily). Different models have been studied in order to determine the best architecture, minimizing statistical error. Simulation results show that the estimated values of wind speed are in good accord with the values measured by the anemometers

Is the NZEB benchmarking approach suitable for assessing energy retrofit design?

Currently, many effort have been done to enable energy saving issues in building design and many definitions have been introduced for most performing constructions based on energy balance between energy demand and supply. Recently, the Net Zero Energy Building theory has bypassed old Passive House concept but many questions still remain open. Present work aims to estimate how NZEB requirements matching could be affected by the choice of their definition and the choice of weighting factor system, to be count in the energy balance. NZEB concept is mainly referred to new buildings design. Its application to existing buildings is for sure an hard task provided the architecture and physical constraints are often problematic. Nevertheless, the benchmarking approach able to assess the building performance according to the NZEB objective can be utilized for other two purposes. The first one is to assess how an existing building is far from the performances of a NZEB. The second one is to assess the contribution of a conventional retrofit in improving its energy balance

Method for size optimisation of large wind\u2013hydrogen systems with high penetration on power grids

Wind power generation is growing rapidly in many locations around the world. Power systems are able to absorb large amounts of wind capacity, but operational problems arise when the wind power penetration becomes high. Such factors as voltage dips, frequency variations, low power system stability, low reactive power and power flow imbalances reduce the economic value and represent a barrier to the unlimited development of wind energy. Hydrogen production from wind power that is not matched with hourly electricity demand appears to be an attractive storage option capable of providing a balancing service to the electricity generators and suppliers for mitigation of the negative impacts due to the random nature of wind. Because of its multi-functionality, hydrogen can be used directly as a fuel, mixed with methane, or transmitted through pipelines to the users. The aim of this paper is to produce useful suggestions for the planning, development and sizing of wind\u2013hydrogen systems by taking into account the local and regional resources, demands, constraints and opportunities. This study considers both the economic and technological variables and describes an optimisation method (OM) for analysing power systems in which part of the electricity generated by a grid-connected wind plant is used to produce hydrogen by electrolysis. An example application of this OM has been developed for a specific geographical area located in central Sicily. Our results identify the potential and the limitations connected to cases that use excess wind power to produce hydrogen for civil applications

Dynamic simulation of a 4th generation district heating network with the presence of prosumers

District Heating Network is identified as a promising technology for decarbonizing urban areas. Thanks to the surplus of heat available from distributed renewable energy plants, a typical heat consumer of the network could become an energy producer during the day (typically referred to as a “prosumer”). Most of the models for thermal grids developed during past years usually assumed a centralized production of the consumed heat. The increasing presence of prosumers will require accurate dynamic modelling to monitor the changes induced in the thermohydraulic parameters of the network. To fill this knowledge gap, this paper aims at developing a model of a thermal grid with prosumers in the TRNSYS environment. The model allows for the dynamic monitoring of the main thermohydraulic parameters of the network. To show these capabilities, a ring-shaped network serving a cluster of 10 residential users located in Palermo (Italy) was assumed as the case study. Different scenarios are investigated based on the presence of solar collectors, prosumers along the network, and cooling by an absorption chiller. The achievable energy and emissions savings are calculated. The results of the study show that even only decreasing the operating temperature can significantly reduce heat losses via the network pipes. In particular, a temperature drop from 100 °C to 80 °C can reduce heat losses by 27.1%. Furthermore, the heat losses can be decreased by up to 52.8% when the network temperature is lowered from 100 °C to 60 °C. Additionally, the presence of prosumers and the solar field could lead to a 31.3% reduction in the energy produced by the centralized plant and a 17.6% reduction in energy consumed for pumping