Editorial: Emerging Technologies for Sustainable Development: From Smart Cities to Circular Economy

It is projected that about 60% of the world’s population is expected to live in cities by 2050 and investment in smart city technology is expected to grow to $135 billion by 2021. Nowadays, major metropolitan areas consume around 65% of available primary energy and contribute around 70% of greenhouse gas emissions for heating and cooling, illumination and transport. In addition, over 720 billion tons of waste is produced every year in worldwide cities. Hence, innovative solutions for the energy-environment are needed to develop sustainable cities. These include smart and carbon-free transport, the use of renewable energy, effective greenhouse gas emissions management to reduce carbon footprint and pollutants to improve air and soil quality as well as waste management through and recycling by transforming conventional linear economy to circular economy. The research topic on the emerging technologies for sustainable development: From smart cities to circular economy consists of seven articles from various authors which offer solutions for renewable energy and clean water. The article research topic span from investment planning for complex urban energy systems, syngas production using palm kernel shells, solar desalination with Fresnel lens, energy business in Thailand, impact of El Nino-southern oscillation to the wind and solar data in Malaysia, microgrid policies in Thailand and aluminium-air battery. Mixed-integer linear programming formulations using time slices is commonly used for the design and optimization of urban multi-energy systems. Bornand et al. used mixed-integer linear programming to investigate the various energy supply and demand, heating and cooling requirements and resource availability for the hospital. Space heating, cooling and ventilation account for almost one-third of the energy consumption for hospitals in central Europe. The investigation results indicate that priority should be given to retrofit the building with a large aspect ratio to reduce the thermal load and supply temperature of the hydronic network. This is important to reduce the energy consumption in the hospital. Dechapanya et al. used biochar produced from the pyrolysis of mangosteen and durian peels as tar removal and NiO/CaO-based catalysts in the palm kernel shells syngas production. The results show that increasing the NiO amounts in the catalyst will increase the production of methane and carbon dioxide concentrations in the syngas. On the other hand, incorporation of the biochar in the syngas production will lead to an increase of the catalytic unit to about 9 times compared to syngas production without biochar. Choong et al. investigated the production of potable water from saline water through the solar desalination process. Flat radial Fresnel lenses were used in the study due to its high achievable temperature and focal point. Compared to a single Fresnel lens, multiple Fresnel lenses will offer Edited and reviewed by: Simone Bastianoni, University of Siena, Italy