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• Technical, economic and environmental modeling frameworks are proposed. • Economic and environmental optima of hybrid renewable energy systems are different. • Local climatic conditions highly influence the impacts and the optimal design. • Single- and multi-objective optimization both have advantages and disadvantages. • Installing photovoltaics is the cheapest way to decrease environmental impacts. The rapid spread of renewables made it essential to design optimal hybrid renewable energy systems (HRES) with the distinctive economic and environmental impacts of each technology in mind. According to a comprehensive literature review, very few studies consider life-cycle environmental impacts in small-scale hybrid renewable energy system optimization. This paper aims to fill this gap by providing a multi-objective design framework for household-scale systems based on the technical modeling of several typical components. Solar photovoltaic, wind turbine, solar heat collector, heat pump, heat storage, battery, and as a novelty, heat insulation thickness are considered. Backup power is either drawn from the grid or produced by a diesel generator in grid-connected and off-grid scenarios, respectively. Single objective optimization using genetic algorithm resulted in the least cost and the least environmental footprint options in a case study of three different locations across Europe. Then, Pareto-optimal solutions between the two extremities were explored with a multi-objective genetic algorithm. Single objective results show substantial differences between environmental and economic optima, while multi-objective optimization proved to be an efficient tool to investigate the trade-offs between the two conflicting goals. Solar photovoltaics is proved to be the most competitive technology to reduce environmental impacts in the case of grid-connected systems. Off-grid systems, however, benefit the most from a balanced mix of different renewable energy sources. Life-cycle impacts in the design of systems involving renewables is proven to be relevant while potential applications of the framework are also revealed. Further research areas, as well as the limitations of the methodology are identified in the conclusion. [ABSTRACT FROM AUTHOR]

From both environmental and energy-saving points of view, solar heating and cooling systems have recently proven themselves in the commercial world as the environmentally friendly and sustainable energy systems which can replace the systems powered by conventional sources of energy such as fossil fuels and electricity. In the present paper, the research contributions conducted on solar absorption cooling systems, integrated with different auxiliary energy devices, are comprehensively reviewed and discussed. Also, various cooling systems integrated with solar technologies, i.e., flat-plate collector, evacuated tube collector, compound parabolic collector and parabolic trough collector, are reviewed. The survey and comparison are carried out in terms of some crucial parameters such as coefficient of performance, annual energy consumption and payback period. Further, this work briefly presents and discusses some possible opportunities for future works from the efficiency viewpoint. [ABSTRACT FROM AUTHOR]