LAUSR

Energy has been a vital commodity for sustaining the life and economic activities and assuring the quality of life and techological advancements. The global picture is not as rossy as expected. One needs to note that at present, a total of 13% of the global population still does not have access to basic electricity. Furthermore, 3 billion people still supply their energy need for cooking and heating from coal, wood, or animal waste, ending up in millions of deaths every year due to indoor air pollution. Therefore, it is crucial to provide access to clean, affordable, and sustainable energy for all. In this regard, the United Nations Assembly in 2015 presented Sustainable Development Goal 7 (SDG 7) that defines five objectives to be achieved by 2030. All proposed pathways for the energy transition to provide electricity, heating, cooling and power for transportation for people and their comfort are expected to consider sustainable energy sources and technologies as solutions to problems rising from hydrocarbon-based fuel consumption. Energy applications, including production, storage, conversion, and utilization, becomes the primary contributor to the currently in-action climate change by covering more than 70% of global greenhouse gas emissions. Therefore, sustainable energy technologies are essential to achieve a nature-friendly energy transition for a cleaner and more peaceful environment. Sustainable energy is energy generated and consumed in a manner that supplies the present demand without preventing future generations from meeting the energy demand of their time. In general, it is thought that sustainable energy and renewable energy have the same meaning, and they are used instead of each other. However, it should be noted that some particular “renewable energy” projects might not be totally sustainable. For instance, the use of agriproducts or clearing off forests for biofuel production might damage the environment more than conventional methods. Therefore, instead of end products, energy systems should be analyzed from the extraction of the resources to disposal to decide either sustainable or not. This approach is also known as the life cycle assessment (LCA) method. Furthermore, energy systems should also be analyzed in terms of environmental impacts through an LCA methodology since the operational emissions might not reflect the system's real impact on the environment. For instance, in the operation phase, electricity consumption does not emit any harmful fumes; therefore, electricity is a carbon-free substance. However, this term might change 180 with the production method of electricity. If electricity is supplied from a coal-based power plant, such electricity consumption will make a significant indirect contribution to climate change. The importance of sustainable energy for humankind can be expressed 3-fold; energy security, environment, and economy. Sustainable energy provides diversification in power supply, which increases energy security, lower the need for imported energy sources, and prevents the depletion of nations' natural energy resources. Compared to conventional fuels, sustainable energy emits lower, in some cases, net-zero, greenhouse gases that make a significant contribution to battling climate change. Furthermore, sustainable energy sources do not entail fuel costs or require long-distance transportation, providing better price stability than conventional fuels. According to the International Energy Agency (IEA), sustainable/ renewable energy demand will increase by 1% by the end of 2020 compared to the 2019 level. Moreover, despite delays in the supply chain and construction chain due to Covid-19, sustainable/renewable electricity generation will grow by 5% by which it will consist of 30% of global electricity generation. In sustainable/renewable-based electricity generation breakdown, hydropower accounts for 60%. Since it does not produce direct greenhouse gases, one might consider nuclear, which produces 10% of global electricity, as sustainable as well, so that the share of sustainable/renewable in global power generation reaches up to around 40%. Canada currently has substantial renewable energy resources to produce 17% of its primary energy. Furthermore, Canada has a unique and well-structured nuclear industry that produces around 15% of its electricity. Canada's sustainability picture looks promising in electricity generation, but the image is not the same for transportation, heating, and cooling. Despite having all these abundant nature-friendly energy sources and getting Received: 2 October 2020 Accepted: 6 October 2020