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Current assessments of the commercial viability and productivity potential of microalgae biofuels have been forced to extrapolate small-scale research data. The resulting analyses are not representative of microalgae cultivation and processing at industrial scale. To more accurately assess the current near-term realizable, large-scale microalgae productivity potential in the USA, this paper presents a model of microalgae growth derived from industrial-scale outdoor photobioreactor growth data. This model is combined with thermal models of the photobioreactor system and 15 years of hourly historical weather data from 864 locations in the USA to more accurately assess the current productivity potential of microalgae. The resulting lipid productivity potential of Nannochloropsis is presented in the form of a map that incorporates various land availability models to illustrate the near-term feasible cultivation locations and corresponding productivity potentials for the USA. The discussion focuses on a comparison of model results with productivity potentials currently reported in literature, an assessment demonstrating the scale of Department of Energy 2030 alternative fuel goals, and a critical comparison of productivity potential in several key regions of the USA. Keywords Biofuels . GIS . Microalgae . Model . Productivity potential Abbreviations PAR Photosynthetic active radiation PFD Photon flux density GIS Geographic information system PBR Photobioreactor ORP Open raceway pond DOE Department of Energy NLCD National Land Cover Database Nomenclature c p Specific heat of water (kJ kg −1 K −1 ) E a Activation energy carboxylation Rubisco (J mol −1 ) G bottom Solar energy reaching the bottom (W m −2 ) G n Solar energy reaching node n (W m −2 ) G sur Solar energy reaching the surface (W m −2Thermal conductivity of water (W m −1 K −1 ) L n Distance between nodes (m) m n Total mass represented by node n (kg) Q i Energy stored/released by ground (W m −2 ) R Universal gas constant (J K −1 mol −1 )Electronic supplementary material The online version of this article (

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Benefits of increasing the renewable energy (RE) share in the total energy mix include better energy security, carbon dioxide emission reductions and improved human health. This paper identifies the potential of RE technologies and role of innovation to double the global RE share from 18% to 36% between 2010 and 2030. As a first step, a Reference Case is developed based on national energy plans of 26 countries which increases the RE share to 21% by 2030. Next, the realizable potential of RE technologies is estimated beyond the Reference Case at country and sector levels. By aggregating country potentials, this paper reveals that the global RE share can double to 36% by 2030. Despite differences in starting points and resource potentials, there is a role for each country in achieving a doubling. For many countries their Reference Cases result in low RE shares and many countries are just beginning to explore ways to increase RE use. The paper identifies action areas where innovation can increase technology development and improve cost-effectiveness, thereby accelerating global RE deployment. More research is required to specify these action areas for individual countries and specific technologies, as well as to identify policy needs to address them.

Energy sector decarbonization to limit the temperature rise to well-below 2 degrees Celsius will result in stranded assets and capital stock replacement before its technical lifetime ends. In this paper, stranded assets in the global power sector are quantified based on a simplified bottom-up analysis that considers the capital stock turnover of fossil fuel-fired power plants in the G20 countries between 2015 and 2050. Power sector transformation starting now based on accelerated deployment of renewables results in US dollar (USD) 927 billion of global power sector stranded assets by 2050. Stranded coal assets would represent around three-quarters of total stranded assets value and China alone would represent 45% of the total. Delaying action to mitigate climate change until 2030 doubles stranded asset value. Countries should consider assets' age profile characteristics in their decision making. Early action and avoidance of investments in new carbon-intensive assets can minimize stranded asset risks.