Domestic hot water systems: environmental performance from a life cycle assessment perspective

Four types of commercially-available domestic hot water (DHW) systems (natural gas instantaneous, electric instantaneous, electric storage and heat pump) were analysed and compared from a life cycle assessment (LCA) perspective and their environmental hotspots (stages and processes) were determined. In addition, the influence of the origin of the energy consumed during their usage was analysed and their environmental performance was compared with that of new DHW systems recently developed. A cradle-to-grave analysis was adopted by employing data provided by the manufacturer and supplemented with secondary data from Ecoinvent. The ReCiPe 2016 (hierarchist perspective) method was used to perform the impact assessment. Regardless of the type of water heater, the use stage (due to high energy consumption) was clearly the main responsible for the environmental damage by DHW systems, but the stage of production of raw materials was also important. A comparative analysis of the four current water heating systems showed that the heat pump caused the least impacts (by litre of heated water provided per year), followed by gas-fired, electric storage, and electric instantaneous in that order. The environmental burdens are highly influenced by the country in which the DHW systems are installed because the origin of the energy source used varies. New water heaters developed by manufacturer demonstrated a trend to an environmental improvement compared to the current ones, although improvements with respect to materials consumed are still required.publishe

Environmental assessment of central solar heating plants with seasonal storage located in Spain

Renewable energies can play a very important role in the development of a new energy model contributing effectively towards a more sustainable development in the mid and long term. In this context Central Solar Heating Plants with Seasonal Storage (CSHPSS) are able to provide space heating and Domestic Hot Water (DHW) to residential buildings with high solar fractions (>50%). These systems are already being used in Central and Northern Europe, as well as in Canada, where there is an important experience in district heating systems. The study presented herein presents an environmental assessment, applying the Life Cycle Assessment (LCA) method, of a CSHPSS, which should cover the space heating and DHW demand of 500 dwellings of 100 m2, located in Zaragoza, Spain. Environmental burdens through the life cycle of the system are estimated based on greenhouse gas emissions, and comprehensive environmental indicators as the ReCiPe and Cumulative Energy Demand (CED). These indicators allow to evaluate the reduction of the environmental load achieved by the CSHPSS analyzed with respect to conventional space heating and DHW systems, as well as to identify the most critical aspects from the environmental perspective. In this article, the environmental behavior of the CSHPSS is decoupled into the two demands covered, heating and DHW, in order to quantify the environmental impact of each generation system. A detailed life cycle inventory is presented with the aim of promoting the development of increasingly efficient technologies from the environmental point of view, not only in the operation phase but also in the construction of the equipment. Furthermore, an in-depth analysis is performed to evaluate the variation of the environmental impact depending on the climatic conditions. The CSHPSS is also dimensioned in different Spanish cities and a LCA is carried out for nine locations. The results can help different stakeholders to make decisions in order to optimize the renewable energy generation systems taking in account its whole life cycle and to point out the necessity to evaluate the environmental impact essentially in the production phase for all renewable energy systems

Water Footprint of Forest and Orchard Trees: A Review

The measurement of water consumption by trees is fundamental for detecting potential opportunities to mitigate water resource depletion. The water footprint (WF) is a tool to address the environmental effects related to water use, identifying ways to reduce overall water consumption. This work presents a review, updating the information on how WF is being addressed when applied to forest and orchard trees, identifying the methodological trends of the WF studies, and highlighting the main challenges that deserve further research for a consistent WF assessment of these trees. A sample with 43 publications selected based on keyword screening criteria was comprehensively reviewed, showing that most of the studies focus on orchard trees (mainly olive and citrus trees). The bulk of the studies only presented accounting or inventory results (i.e., water volumes consumed) and disregarded their sustainability or impact. This review highlights that a robust WF assessment of forest and orchard trees requires further research for harmonising the quantification of the green water scarcity footprint, and puts key challenges to the WF practitioners, such as the selection of the most adequate method to estimate ET considering trees specificities and climatic parameters, and the adoption of high spatial and temporal resolution for the WF assessment

Water Footprint of Forest and Orchard Trees: A Review

The measurement of water consumption by trees is fundamental for detecting potential opportunities to mitigate water resource depletion. The water footprint (WF) is a tool to address the environmental effects related to water use, identifying ways to reduce overall water consumption. This work presents a review, updating the information on how WF is being addressed when applied to forest and orchard trees, identifying the methodological trends of the WF studies, and highlighting the main challenges that deserve further research for a consistent WF assessment of these trees. A sample with 43 publications selected based on keyword screening criteria was comprehensively reviewed, showing that most of the studies focus on orchard trees (mainly olive and citrus trees). The bulk of the studies only presented accounting or inventory results (i.e., water volumes consumed) and disregarded their sustainability or impact. This review highlights that a robust WF assessment of forest and orchard trees requires further research for harmonising the quantification of the green water scarcity footprint, and puts key challenges to the WF practitioners, such as the selection of the most adequate method to estimate ET considering trees specificities and climatic parameters, and the adoption of high spatial and temporal resolution for the WF assessment