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The arrival of the hydrogen (H2) economy has been the subject of many studies. Earlier articles were over-optimistic about the timing and extent of global H2 uptake, and predicted private vehicles as leading the way to a H2 economy. The recent strong rise in the global electric vehicle fleet has inevitably led to a reassessment of the prospects for H2, at least for transport. This review paper examines how researchers over recent decades have envisaged how the H2 economy would arrive, and why it was desirable, or even inevitable; it also looks at the future prospects for the H2 economy. The key findings are as follows: ? Among the leading energy forecasting bodies, particularly the International Energy Agency (IEA), even the most optimistic scenarios predict under 10% H2 penetration by 2050. ? IEA forecasts are very optimistic about the prospects for the introduction of carbon dioxide removal technologies and growth of dispatchable sources of low-carbon energy. ? More realistic IEA forecasts would increase the need for the growth of intermittent energy sources such as wind and solar. The subsequent requirement for energy storage would in turn help the case for H2 adoption. ? No new technologies are on the horizon to decisively tip the balance in favor of H2. ? It is concluded that a global H2 economy is still distant, but it could arise in energy-poor countries such as Japan and South Korea, and it could find a niche in freight transport. [ABSTRACT FROM AUTHOR]

The building and transportation sectors are responsible for the greatest proportion of energy consumption in cities. While they are intrinsically interlinked with urban built form and density, climate change and technological innovation are having an effect on their relative contributions. This paper aims to develop an optimisation framework to facilitate the identification of the most energy-efficient urban built forms and urban geometry for the future built environment that can be adapted to the changing climate and ongoing technological development. It examines future scenarios for the city of London as a temperate climate zone (as a case study), in 2050, and contrasts it with the present situation. Specifically, the impact of climate change along with the penetration of electric vehicles into the transportation system that can be charged via rooftop photovoltaics is investigated. This study initially develops the geometrical models of four selected urban built forms and, secondly, analyzes their energy performance using an urban energy simulation software. The results, showing the impact of future scenarios on building energy performance, urban built form and density, demonstrate that court and tunnel-court built forms show better energy performance for future development. It is therefore recommended that for future urban developments in London, deep plan court and tunnel-court buildings with a lower number of storeys and a large cut-off angle are more advantageous in terms of building energy to accommodate the expected climate change. Finally, results of simulation trials indicate that the total building energy demand in 2050 is considerably higher than in the present climate as a result of additional cooling load and electric vehicle charging load. [ABSTRACT FROM AUTHOR]

The arrival of the hydrogen (H2) economy has been the subject of many studies. Earlier articles were over-optimistic about the timing and extent of global H2 uptake, and predicted private vehicles as leading the way to a H2 economy. The recent strong rise in the global electric vehicle fleet has inevitably led to a reassessment of the prospects for H2, at least for transport. This review paper examines how researchers over recent decades have envisaged how the H2 economy would arrive, and why it was desirable, or even inevitable; it also looks at the future prospects for the H2 economy. The key findings are as follows: ● Among the leading energy forecasting bodies, particularly the International Energy Agency (IEA), even the most optimistic scenarios predict under 10% H2 penetration by 2050. ● IEA forecasts are very optimistic about the prospects for the introduction of carbon dioxide removal technologies and growth of dispatchable sources of low-carbon energy. ● More realistic IEA forecasts would increase the need for the growth of intermittent energy sources such as wind and solar. The subsequent requirement for energy storage would in turn help the case for H2 adoption. ● No new technologies are on the horizon to decisively tip the balance in favor of H2. ● It is concluded that a global H2 economy is still distant, but it could arise in energy-poor countries such as Japan and South Korea, and it could find a niche in freight transport.