• Energy Research

District heating and cooling networks represent a compelling energy system solution due to their capacity to integrate renewable energies and leverage local surpluses of thermal resources. The meticulous design and optimization of network infrastructure are imperative to fully exploiting the potential of these energy systems. The Life Cycle Assessment of district heating and cooling networks for the purpose of environmental sustainability is a crucial and increasingly demanded aspect, particularly in light of the progressively stringent European regulations. The Life Cycle Assessment methodology could offer an evaluation throughout the entire life cycle of such networks. The proposed review scrutinizes the application of the Life Cycle Assessment methodology to evaluating the environmental profile of district heating and cooling systems. The methods, findings, and challenges are examined through a literature review and case study analysis. The results highlight variations in the climate profile influenced by the network generation type and multifunctionality approaches. The analysis revealed a range of emission factors, spanning from 11 gCO2eq/kWhth to 470 gCO2eq/kWhth for district heating and 6 gCO2eq/kWhth to 64 gCO2eq/kWhth for district cooling. The discussion emphasizes integrating district heating and cooling network management considerations and addressing methodological challenges. This study concludes by proposing future research directions for developing a universal LCA-based tool for district heating and cooling network analysis.

Abstract In Mexico efforts are being made to promote the use of solar energy for cooling in the Agro-Food Industries (AFI), 120 industries were contacted in order to assess the solar cooling potential application in the sector. One case study was selected among the visited potential end users according to the size of the facility, the information available and their willingness to collaborate in the present project. Data from the industry was used to select the appropriate solar cooling concept and therefore the collector’s typology, and the absorption cooling system. Moreover, the operation of the system was simulated in order to define the optimal size of the collector field required. The proposed cooling system was composed by a Fresnel concentrating collector field to activate a series of air cooled single-effect ammonia–water absorption chillers. The cooling system simulation was carried out with the Transient Systems Simulation Programme (TRNSYS) which allowed to model the collector system that fulfill the required load. The calculated saved electricity was around 19% of the total consumption, this small fraction is due to the fact that the selected facility is operating continuously with very large refrigeration capacities. The specifications of the simulated solar cooling system are presented.

Net-zero climate districts are gaining wide attention at the European and international levels. Urban regeneration competitions have been launched recently to stimulate development; nevertheless, the literature does not yet provide a shared scope definition (i.e., product system). Using the process-based life cycle assessment method, the authors evaluate the climate profile of a new district in Milan (14 buildings with 36,000 m2 of gross surface area in total) aiming to become the first net-zero social housing project in Italy. The authors show in the results section how climate neutrality is achieved on the part of the real estate operator by varying the scope. The most conservative scenario (including all the emission sources considered in the analysis) indicates that the net-zero climate target is reached only by purchasing voluntary carbon credits. The authors also highlight: (i) a district composed of nearly-zero energy buildings is far from the definition of a net-zero climate emissions district; (ii) a net-zero climate emissions district may not be a positive energy district and vice-versa; and (iii) constraints linked with the lack of space in a densely populated city due to insufficient area to install renewables on site.

The process of achieving decarbonization and greenhouse emissions’ reduction goals is facilitated and accelerated by the implementation of renewable-based DH rather than multiple individual renewables systems. This work presents an application case that demonstrates how an energy system based on conventional and carbon-emitting heat supply sources can be converted in a fully renewable network.In its current configuration, the city under study, located in Northern Italy, gets 40% of the total 160GWh of heat demand of the DH from a waste-to-energy plant, 9% from a biomass-fuelled ORC, 33% from natural gas cogeneration and 18% from natural gas boilers. In order to support the city’s municipality in developing decarbonization measures through the modernization of the current district heating network, the aim of this work is to investigate in detail the possibility to integrate local renewable and excess heat sources, whose availability and synergy with the heat demand has been highlighted by a recent mapping-based project developed with the Italian DH Association, AIRU, on the whole Italian territory. The present work can be therefore seen as a validation case study of the methodology developed at large-scale level in the latter project. The results of that analysis show that there are the conditions to meet 90% of the heating needs of the DH with renewables and waste heat recovery from two already existing plants, namely a wastewater treatment plant (WWTP) and a steelwork. The approach used in this work, in which different scenarios of integration are simulated in energyPRO, brought to the definition of the energy mix which evidenced a favourable cost–benefits ratio: 59% of thermal energy from the steelwork, 31% from the WWTP, 5% from the natural gas CHP and 5% from the boilers.

AbstractDirect Steam Generation (DSG) Concentrated Solar technology, based on Linear Fresnel Reflectors (LFR) and aimed at supplying saturated steam to industrial processes, is a promising application; nevertheless, nowadays few case studies and very few installations have been developed. A methodology for the design optimization of a MW solar DSG plant is presented in this article and applied to a real case study of a Brazilian tire manufacturing facility. A steady-state model, with spatial discretization of the ordinary equations, allows characterizing the physical phenomena such as pressure drop and heat transfer, and therefore to determine the pressure and specific enthalpy trend along the recirculation loop. For each receiver tube of the solar collectors, the occurring single or two-phase flow pattern is calculated based on specific empirical equations developed for evaporation in horizontal tubes. Two reference operating conditions have been identified for the present case study, at which the optimal field layout results to be a series connection of all the collectors, and the optimal nominal flow rate to avoid possible harmful operating conditions for the absorber tubes is 1.0kg/s.

In this work, novel composite silicone-SAPO-34 foams have been prepared and experimentally characterized for application in desiccant open cycles. Water adsorption isotherms of several samples have been measured by a gravimetric dynamic vapour sorption analyser at 30°C and 70°C up to the relative humidity RH= 75%, representing typical process and regeneration air conditions in desiccant evaporative cooling cycles. Adsorbent foams manufactured with 20%, 40% and 60% weight fraction of SAPO-34 have been compared with the pure SAPO-34 powder. Results highlighted that the prepared foams adsorb a significant amount of water, according to the initial mass fraction of zeolite used in the compound. Moreover, the tested foams exhibited sufficiently fast water sorption rate for practical application in a desiccant open cycle system.

Abstract The steady-state mathematical modelling of advanced absorption cycles can be time-consuming and error-prone. In this work, a computer tool based on a modular approach and supported by a comprehensive methodology is described. The solver automatically eliminates redundant mass and species balance equations, detects the existence of paired interconnections, and identifies the nature of the missing auxiliary conditions. To illustrate the tool's capabilities, two advanced refrigeration cycles are modelled, double-lift and resorption. For each cycle, two different embodiments are discussed in consideration of the volatility of the absorbent. With reference to cooling applications driven by low temperature heat, the performance of three cycles are compared: NH3-LiNO3 double lift (DL1), NH3-H2O double lift (DL2), NH3-H2O resorption (R2). DL1 and DL2, despite their lower thermal COPc can achieve a maximum value of EER (about 7.7) only slightly lower than that achieved by R2 (about 7.9) with a much lower driving temperature.

The hydrogen vector stands as a potentially important tool to achieve the decarbonization of the energy sector. It represents an option to store the periodic excesses of energy generation from renewable electrical sources to be used as it is as a substitute for fossil fuels in some applications or reconverted into electricity when needed. In this context, hydrogen can significantly decarbonize the building sector as an alternative fuel for gas-driven devices. Along with hydrogen, the European strategic vision indicates the electrification of heat among the main energy transition pathways. The potential environmental benefits achievable from renewable hydrogen in thermally-driven appliances and the electrification of residential heat through electric heat pumps were evaluated and compared in this work. The novelty of the research consists of a consequential comparative life cycle assessment (16 impact categories) evaluation for three buildings (old, old retrofitted, and new) supplied by three different appliances (condensing boiler, gas absorption heat pump, and electric heat pump), never investigated before. The energy transition was evaluated for 2020 and 2030 scenarios, considering the impact of gaseous fuels (natural gas and European green hydrogen) and electricity based on the pathway of the European electricity grid. (27 European member states plus the United Kingdom). The results allowed to compare the environmental profile in deterministic and stochastic approaches and confirm if the increase of renewables reduces the impact in the operational phase of the appliances. The results demonstrate that despite the increased renewable share, the use phase remains the most significant for both temporal scenarios, contributing to 91% of the environmental profile. Despite the higher footprint in 2020 compared to the electric heat pump (198-200 vs. 170-196 gCO2eq/kWhth), the gas absorption heat pump offered a lower environmental profile than the others in all the scenarios analyzed.