Effective strategic purchasing and supplier selection in companies provides businesses with leverage in acquiring goods and services. Thus, companies are in a better position to negotiate prices, discounts, delivery times and logistic channels. Also, strategic purchasing allows for performing a risk assessment to ensure the company’s profitability. This research aimed to identify the key currently deliberated by SMEs for supplier selection, considering such purchasing strategies as (1) cost reduction, (2) risk management, (3) global sourcing, (4) total quality management, (5) sustainable management and (6) supplier management. Also, it aimed to identify the emerging issues related to purchasing strategies. This research work performed a content analysis following a literature review. The Scopus indexation database was selected to conduct the document search. After the refinement process, based on 59 analysed documents, bibliometric assessment tools were applied to identify the key criteria for supplier selection. The TOP6 highest ranked criteria, which corresponds to 80 % of the most referred criteria, include: (1) the quality of goods; (2) compliance with the delivery times; (3) price/cost; (4) supplier reputation and/or market positioning; (5) geographical location; and (6) supplier performance history. The goal of strategic purchasing is to support the companies in achieving long-term goals through its integration into the company’s strategic planning process. It should be identified by the managers as an important resource. Several factors elevate the importance of strategic purchasing, namely, environmental protection, technology advances related to logistics 4.0, and risk assessment related to global sourcing and sustainability. The present research is in line with the findings of the referred literature, i.e., the application of prioritised criteria for the procurement and supplier selection operations in the industrial context, aiming to reduce lead times and logistic costs. The criteria must be aligned with the purchasing strategies adopted by the companies. The manuscript aims to demonstrate that the fundamentals of strategic purchasing strategies can contribute to the improvement of the SME supply process with the application of simple and cost-effective approaches.

Paper aims This research has two main objectives, firstly to analyze the level of implementation of lean and green practices of a set of companies and secondly to analyze the relationship between lean and green initiatives in an industrial context. Originality The use of Structural Equation Modelling (SEM) allows a better analysis of the interlinkage of lean and green towards sustainable gains. The developed model offers conceptual contribution to the arena of the logistics, sustainability, lean and green. Research methods The methodology used in this study was carried out resorting an inquiry. Firstly, aiming to understand the level of these practices (lean and green) practices in the North of Portugal, a case study was considered. The sample taken is a convenient one, due to time and budget constraints. Secondly, in order to assess the possibility to combine lean ad and green initiatives, a statistical approach was used to develop a SEM for lean and green practices. Main findings The results demonstrated that the level of implementation of lean and green practices on Portuguese companies are not properly addressed and formalized. The statistical analysis also showed that lean environmental practices and green practices are positively associated. The research showed that lean and green has also a positive impact on the logistics processes of companies. Implications for theory and practice This research brings some contributions to both academy and companies. Firstly, a further discussion about the benefits of combining lean and green towards sustainability. Secondly, the development of a structural model for lean and green practices was presented, this model contributes to a better understanding of these practices, which can lead companies to develop strategic initiatives towards sustainability.

Solar thermal systems have been widely used to increase energy efficiency in the building sector, since the use of renewable energy sources became one of the top priorities to meet environmental targets. The main objective of this study is the thermo-economic optimization of solar thermal systems for residential building applications, considering a multi-objective approach. The simulations were performed through a MatLab code by implementing an elitist variant of Non-dominated Sorting Genetic Algorithm-II (NASGA-II). The solar collection area and the linear loss coefficient as well as the tank storage volume were defined as decision variables. A two-dimensional Pareto front was obtained, considering as objective functions the minimization of the annualized investment cost and the maximization of the solar collection efficiency. Based on the best trade-off between both objectives and considering that the solar thermal systems can operate for a period of at least 15 years, the Pareto analysis led to the conclusion that a system with an annualized investment cost between 270 and 280 €/year allows reaching a collection efficiency of 60%. After the analysis of the optimal solution points, a configuration was selected to estimate the system total purchasing cost: a panel with a solar area of 4.17 m² and with a linear coefficient loss of 3.684 W/m².K; a storage volume of 0.275 m³; and a pump flow rate of 0.1364 m³/h. For this configuration, we estimated a total purchasing cost of 2545.0 €, whereas the solar collector and the storage tank are the most expensive components, representing a share of 42% and 43%, respectively. These results represent a specific cost of 610.3 €/m² per solar collection area.