Water-energy and GHG nexus assessment of alternative heat recovery options in industry: A case study on electric steelmaking in Europe

In the last few years, the water-energy nexus concept has emerged as a global issue. However, studies on European countries are relatively few, and often focused on agriculture. Cooling purposes represent the main part of industrial water demand, and waste-heat recovery is a main strategy to improve resource efficiency. This paper presents a real case study of low-temperature waste-heat recovery in an electric steelmaking industry and evaluates the impact of feasible interventions on primary energy and water consumption, as well as on CO2 equivalent emissions. Based on a Europe wide review of energy and water prices, of energy sources and corresponding resource efficiency indicators, a Monte Carlo model was developed to undertake a generalization of the case study to the EU-15. It was found that solutions with the lowest primary energy demand and the lowest CO2 equivalent emissions demonstrate the greatest water footprint. This is the case of some southern European countries, where heat recovery projects with the highest water intensity are feasible due to high electricity and low water prices. As increasing carbon prices may exacerbate this phenomenon, inducing a switch to water intensive technologies, incentives to carbon emission reduction should be carefully designed

Water-energy and GHG nexus assessment of alternative heat recovery options in industry: A case study on electric steelmaking in Europe

In the last few years, the water-energy nexus concept has emerged as a global issue. However, studies on European countries are relatively few, and often focused on agriculture. Cooling purposes represent the main part of industrial water demand, and waste-heat recovery is a main strategy to improve resource efficiency. This paper presents a real case study of low-temperature waste-heat recovery in an electric steelmaking industry and evaluates the impact of feasible interventions on primary energy and water consumption, as well as on CO2 equivalent emissions. Based on a Europe wide review of energy and water prices, of energy sources and corresponding resource efficiency indicators, a Monte Carlo model was developed to undertake a generalization of the case study to the EU-15. It was found that solutions with the lowest primary energy demand and the lowest CO2 equivalent emissions demonstrate the greatest water footprint. This is the case of some southern European countries, where heat recovery projects with the highest water intensity are feasible due to high electricity and low water prices. As increasing carbon prices may exacerbate this phenomenon, inducing a switch to water intensive technologies, incentives to carbon emission reduction should be carefully designed

Free-cooling potential in shopping mall buildings with plants equipped by dry-coolers boosted with evaporative pads

Shopping malls are often characterized by high internal thermal loads due to occupancy, lighting, electrical devices, and solar radiation entering through the large skylights. The aim of this study is the evaluation of the energy saving reachable adding a cooling evaporative pad upstream a dry cooler. In particular, two different cooling plant configurations has been investigated: a cooling plant with a chiller equipped with a dry cooler (C-DC), that can be used as condenser of refrigeration system or to work with free-cooling mode and the previous system equipped with an evaporative cooling pad upstream the dry cooler (C-E-DC) in order to enlarge the range of temperatures suitable for free cooling. A building model of a typical shopping mall and two cooling plant has been modeled by means of TRNSYS simulations carried out in several European cities. Simulation results show that the C-E-DC configuration allows a greater energy saving amount than C-DC configuration for all the cities considered. It can be noted that the locations with a hot or moderate climate have a higher reduction in chiller electrical consumptions. Further investigations will be carried out taking in to account more extensively the moisture content of the air for the different locations considered

Hygrothermal modelling of building enclosures: reference year design for moisture accumulation and condensation risk assessment

Interstitial condensation and water accumulation risk in building envelopes could be assessed with methods and models base d on moisture migration through porous media coupled to heat transfer. One of the difficulties in evaluating the boundary conditions for the heat and mass transfer model is the choice of an appropriate weather file. The most advanced models, described by the standard EN 15026:2007, require the hourly values of rain, wind, radiation, temperature and relative humidity to compute the water content in the porous materials. In this contribution, the method described by the standard EN ISO 15927-4:2005, typically used to design Moisture Reference Years (MRY), has been extended to the design of 34 typologies of representative weather files. The generation criteria have been base d on the assumption that the simulation results are influenced by rain deposition on the considered wall. The procedure has been followed considering 5 different wall exposures that lead to different MRY. The years of the climate of Turin (Italy) between 2002 and 2016 have been considered for the generation of the reference years. Finally, the annual mean moisture contents for two common wall types have been calculated using the obtained MRY and compared to the annual mean moisture contents obtained with the measured weather data, and the effects of the selection of the weather parameters is presented

Evaporative cooling systems to improve internal comfort in industrial buildings

Several studies were carried out to determine how hot or cold environments can affect task performance and can influence productivity. Usually, HVAC plants are exactly designed in order to guarantee comfortable internal conditions inside built environments, but not all kind of buildings are equipped with a heating or cooling plant, like for example, some industrial buildings. These buildings are often characterized by high internal thermal loads. For those buildings the ability of different plant configurations to improve indoor thermal conditions was considered taking into account the influence of several parameters, like weather conditions, internal gains, thermal transmittance, ventilation air flow rate, etc. Simulation results are compared in terms of energy savings and thermal comfort. \ua9 2017 The Author(s)

Analysis of water droplet evaporation through a theoretical-numerical model

An analytical model previously defined and numerically transposed via a Runge-Kutta 4-th order method is here employed to thoroughly describe a water droplet travelling in air from a sprinkler nozzle down to the ground. The study, aimed at a realistic description of the process, is completed by a number of analysis parameters which contribute to fully describe the system, the phenomenon and the mutual affections that characterise the study in relation to the droplet travel distance, the droplet time of flight, and the final droplet temperature. The few assumptions superimposed do not alter the reliable picture arrived at. The results, provided in the form of figures and comments, enable the reader to well understand the phenomenon and to realise which parameters prove more effective on conditioning the whole process. A general applicability of such results to define rational irrigation policies appears extremely evident and is supported by the treating provided

Exploring the Water-Energy-GHG NEXUS in Process Waste Heat Recovery Projects

In the last few years, the water–energy nexus concept emerged as a global issue in the international research community. However, studies on European countries are relatively few, and often focused on the energy sector and agriculture, even though industry dominates water uses in many European countries. Cooling purposes represent the main part of industrial water demand, and waste heat recovery is perceived as a main strategy to improve industrial resource efficiency. In this paper, we consider a real case study of low-temperature waste-heat recovery in a process industry and evaluate the impact of feasible interventions on primary energy and water consumption, as well as on CO2 equivalent emissions. Based on a Europe wide review of energy and water prices, of energy sources and corresponding resource efficiency indicators, a Monte Carlo model is developed to attempt a generalization of the case study to the EU-15. It is found that market factors, particularly water prices, mainly determine the economic optimum, but policy instruments, such as carbon prices, may also play a role in some countries, causing a shift towards more water intensive configurations

MULTICRITERIA ANALYSIS FOR THE SELECTION OF SPACE HEATING SYSTEMS IN AN INDUSTRIAL BUILDING

Decisions on space heating of industrial buildings involve several conflicting objectives and solutions prospected by economic optimization (e.g. life cycle cost minimization) models may be far from the real preferences of decision makers. To overcome this limit, multi-criteria decision analysis which has hardly been used at single building level, especially in industrial contexts, could be a helpful methodology. This paper presents the application of a well-known multi-criteria approach, the Analytic Hierarchy Process (AHP), to the selection of space heating systems for an industrial building. We discuss the technologies available for industrial heating, criteria elicited from the decision maker and the ranking of alternatives identified with our AHP model. As very little is reported in literature about industrial energy system choices, our study, although focused on an individual case, may shed some light on decision making in this sector. To this end, we also compare our results with evidence on residential heating systems choices derived from literature. Investment costs are the most important criterion for industry, whereas qualitative attributes and operational costs are most important for homes. Qualitative attributes also significantly affect industrial heating system choices and, as the AHP is particularly effective in handling these aspects, we suggest it could be used for tactical energy planning models

SIMULAZIONE FLUIDODINAMICA DI UN DIFFUSORE A QUATTRO VIE

Il calcolo della diffusione dell\u2019aria negli ambienti rappresenta uno dei principali problemi nella progettazione dei sistemi di ventilazione. Grazie alla cresciuta capacit`a di calcolo degli elaboratori elettronici attualmente `e possibile utilizzare tecniche avanzate quali la simulazione numerica (CFD) per caratterizzare il comportamento fluidodinamico dei diffusori d\u2019aria. La differenza di scala tra le geometrie dei diffusori e gli ambienti da ventilare impongono una soluzione separata dei due problemi e soprattutto una corretta imposizione delle condizioni al contorno per l\u2019analisi completa di un ambiente caratterizzata da una griglia meno raffinata. In questo lavoro si `e analizzato il comportamento di un diffusore a soffitto a quattro vie di uso comune nella ventilazione e nel condizionamento di locali tipo ufficio. Il diffusore `e caratterizzato da una geometria particolarmente complicata ed `e stato quindi necessario effettuare una analisi fluidodinamica dettagliata. Il campo di moto risultante nei pressi del diffusore impedisce l\u2019utilizzo di condizioni al contorno banali per l\u2019analisi fluidodinamica di ambiente, pertanto `e stato necessario sviluppare una metodologia alternativa confronto la soluzione ottenuta con le usuali formule dei getti

Efficiency and Energy Savings Evaluation for Dry-Cooler Equipped Plants

The problem of the high energy requirements for the building climatization is well known. Some significant energy savings may be achieved by means of indirect free cooling. The aim of this work is to analyze the possibility to exploit this systems to cool down water of fan coil plants, in some kind of buildings taking into account different climate conditions and internal gains. The water supplying the plant terminals is cooled in the Dry-Cooler or in the chiller: an external air-water heat exchanger. The external climate conditions can guarantee a free cooling effect in order to reduce the load absorbed by the chiller. First of all, the thermal loads of two kind of buildings (a shopping centre and an office block) have been evaluated through the simulation of their behaviour during a whole year, with a hourly time-step, for different climate conditions, using the software Energy Plus. Realistic working conditions, suggested by Dry Coolers manufacturers, have been imposed. For each hour during the simulation period, it has been determined the external maximum temperature that lets the Dry Cooler balance the cooling load while the chiller is off. Then it has been possible to verify the sharing out of the thermal load between Dry Cooler and Chiller