• Energy Research

Hemp shives is a lightweight material known for its insulating properties. Associating these bio-fibers with plant-based matrix instead of a mineral binder in insulation applications is of ecological interest. This article describes the study of a low environmental impact 100% plant-based material made solely from wheat starch and hemp shives. The hemp/starch ratio (H/S) influence and hemp shive size are studied. Samples are evaluated in terms of physical properties, mechanical behaviour and hygrothermal properties through an experimental approach. Results show that increasing 0–5 mm hemp shive proportion from 15% to 30% leads to a significant enhancement of the mechanical and hygric characteristics due to the load transfer and porosity. However, when the H/S ratio increases, mechanical and hygrothermal characteristics decrease slightly. Finally, the hemp-starch agro-material with H/S equal to 8 and 30% of 0–5 mm hemp shive seems to be the optimal composition between the studied samples.

Due to climate change and hot summers in most of Algeria’s regions, air conditioning has become a thorny issue, resulting in excessive energy consumption. This research focuses on the implementation of dew point evaporative coolers as an alternative to conventional air conditioners. The desirability function approach is used to predict the optimal operating parameters and compare the thermal performance and water consumption of two dew point cooler configurations (counter flow-regenerative cooler and combined parallel–regenerative cooler) under different climatic conditions in Algeria. A numerical model is developed and validated using literature data for regenerative and combined dew point evaporative systems. Parametric analysis and multi- to single-objective optimization simulations were performed with the GenOpt simulation software, identifying the most influential parameters and predicting the optimal conditions for both configurations. The findings suggest that the optimal channel spacing, working air ratio, and primary air velocity are identical for both technologies.However, the cooling capacity and the coefficient of performance of the combined parallel–regenerative cooler are higher in drier climates. When both technologies are compared at nearly equal dew point efficiency, the combined configuration improves cooling capacity by 5%, while increasing water consumption by about 40%. This study provides a useful method for assessing cooling capacity and adapting suitable dew point technology to various climates and cities.

This paper aims to find an optimal maximum allowable temperature for a cooling system of a photovoltaic panel. As the operating temperature of a photovoltaic cell increases, its efficiency significantly decreases. Overheating due to excessive solar radiation is one of the main obstacles faced by photovoltaic panels, especially in hot and arid regions. This is why, several cooling systems have recently been integrated into photovoltaic panels. The power consumption of the cooling systems affects the total amount of energy harvested, whereas the goal is to increase it by reducing the operating temperature. It is therefore, necessary to find an optimal value for the maximum allowable temperature which can reduce the cooling system energy consumption while maintaining thermal efficiency at acceptable levels. The maximum allowable temperature is the threshold at which the cooling system activates and reduces the operating temperature to the ambient temperature, where it is deactivated. The activation/deactivation frequency increases when the maximum allowable temperature is low and vice versa. Experimental measurements of the net harvesting energy validated by analytical calculation shows that 45 °C the optimal value of the maximum allowable temperature for the studied system. The procedure proposed in this paper will increase the net efficiency of the photovoltaic panel equipped with such a cooling system. The originality of this paper lies in the fact that it takes into account the negative contribution of the power consumption of a cooling system coupled with a PV panel.

Abstract Energy efficiency and the reduction of greenhouse gas emissions are actual key issues in all the economic sectors and, in particular, in buildings which is acknowledged worldwide as one of the most energy-consuming. In this context, it would be desirable to duly address those issues by searching for and assessing proper solutions and strategies: the usage of eco-friendly construction materials can be considered as one of those. This paper reports upon the performance of three facades containing sustainable products that are manufactured using natural resources and, alternatively, post-consumer waste based materials; those are: hemp-concrete; and Recycled PolyEthylene Terephthalate (R-PET), respectively. The energy performance of each facade was assessed in terms of cooling and heating demands, electrical consumptions and indoor thermal comfort including indoor temperature and relative humidity. Additionally, a Carbon Footprint (CF) assessment was carried out considering both the estimated energy demands and the life-cycle emission factors associated with the energy mix of the countries where the facades were located, i.e. France and Italy. Based upon the findings of the study, the R-PET facade represented the most performing solution between the three facades in all the scenarios considered and, moreover, the humidity-sensitive flow rate ventilation system came out as a solution able to reduce the electricity consumptions. Finally, considering the Carbon Footprint results, the energy country mix emerged as a key issue, making the Italian case study the worst one, though the total electrical energy consumption were comparable with those of the other case studies.