Toward a sustainable global energy supply infrastructure : net energy balance and density considerations

This paper complements previous work on the economics of different energy resources by examining the growth potential of alternative electricity supply infrastructures as constrained by innate physical limits. Coal-fired generation meets the criteria of longevity (abundance of energy source) and scalability (effective capability to expand to the multi-terawatt level) which are critical for a sustainable energy supply chain, but it carries a very heavy carbon footprint. Renewables and nuclear power meet both the longevity and climate friendliness criteria. However, they vary in terms of their ability to deliver net energy at a scale needed for meeting a huge global energy demand. The low density of renewable resources for electricity generation and the current intermittency of many renewables limit their ability to achieve high rates of growth. And a significant global increase in nuclear power deployment could engender serious risks related to proliferation, safety, and waste disposal. Unlike renewable sources of energy, nuclear power is an unforgiving technology because human lapses and errors can have ecological and social impacts that are catastrophic and irreversible. The transition to a low carbon economy is likely to prove much more challenging than some optimists have claimed.Energy Production and Transportation,Climate Change Mitigation and Green House Gases,Energy and Environment,Environment and Energy Efficiency,Energy Demand

Towards a Sustainable Global Energy Supply Infrastructure: Net Energy Balance and Density Considerations

This paper employs a framework of dynamic energy analysis to model the growth potential of alternative electricity supply infrastructures as constrained by innate physical energy balance and dynamic response limits. Coal- red generation meets the criteria of longevity (abundance of energy source) and scalability (ability to expand to the multi-terawatt level) which are critical for a sustainable energy supply chain, but carries a very heavy carbon footprint. Renewables and nuclear power, on the other hand, meet both the longevity and environmental friendliness criteria. However, due to their substantially di¤erent energy densities and load factors, they vary in terms of their ability to deliver net excess energy and attain the scale needed for meeting the huge global energy demand. The low power density of renewable energy extraction and the intermittency of renewable ows limit their ability to achieve high rates of indigenous infrastructure growth. A signi cant global nuclear power deployment, on the other hand, could engender serious risks related to proliferation, safety, and waste disposal. Unlike renewable sources of energy, nuclear power is an unforgiving technology because human lapses and errors can have ecological and social impacts that are catastrophic and irreversible. Thus, the transition to a low carbon economy is likely to prove much more challenging than early optimists have claimed.dynamic energy analysis; alternative electricity supply; coal; nuclear energy

Silver as a constraint for a large-scale development of solar photovoltaics? Scenario-making to the year 2050 supported by expert engagement and global sensitivity analysis

In this study we assess whether availability of silver could constrain a large-scale deployment of solar photovoltaics (PV). While silver-paste use in photovoltaics cell metallization is becoming more efficient, solar photovoltaics power capacity installation is growing at an exponential pace. Along photovoltaics, silver is also employed in an array of industrial and non-industrial applications. The trends of these uses are examined up to the year 2050. The technical coefficients for the expansion in photovoltaics power capacity and contraction in silver paste use have been assessed through an expert-consultation process. The trend of use in the non-PV sectors has been estimated through an ARIMA (auto-regressive integrated moving average) model. The yearly and cumulative silver demand are evaluated against the technological potential for increasing silver mining and the estimates of its global natural availability, respectively. The model implemented is tested with a quasi-random Monte Carlo variance-based global sensitivity analysis. The result of our inquiry is that silver may not represent a constraint for a very-large-scale deployment of photovoltaics (up to tens TW in installed power capacity) provided the present decreasing trend in the use of silver paste in the photovoltaics sector continues at an adequate pace. Silver use in non-photovoltaic sectors plays also a tangible influence on potential constraints. In terms of natural constraints, most of the uncertainty is dependent on the actual estimates of silver natural budget

Pathway to oxide photovoltaics via band-structure engineering of SnO

The prospects of scaling current photovoltaic technologies to terawatt levels remain uncertain. All-oxide photovoltaics could open rapidly scalable manufacturing routes, if only oxide materials with suitable electronic and optical properties were developed. A potential candidate material is tin monoxide (SnO), which has exceptional doping and transport properties among oxides, but suffers from a low adsorption coefficient due to its strongly indirect band gap. Here, we address this shortcoming of SnO by band-structure engineering through isovalent but heterostructural alloying with divalent cations (Mg, Ca, Sr, Zn). Using first-principles calculations, we show that suitable band gaps and optical properties close to that of direct-gap semiconductors are achievable in such SnO based alloys. Due to the defect tolerant electronic structure of SnO, the dispersive band-structure features and comparatively small effective masses are preserved in the alloys. Initial Sn1-xZnxO thin films deposited by sputtering exhibit crystal structure and optical properties in accord with the theoretical predictions, which confirms the feasibility of the alloying approach. Thus, the implications of this work are important not only for terawatt scale photovoltaics, but also for other large-scale energy technologies where defect-tolerant semiconductors with high quality electronic properties are required

The Resource Demand of Terawatt-Scale Perovskite Tandem Photovoltaics

Photovoltaics (PV) is the most important energy conversion technology for cost-efficient climate change mitigation. To reach the international climate goals, the annual PV module production capacity must be expanded to multi-terawatt scale. Economic and resource constraints demand the implementation cost-efficient multi-junction technologies, for which perovskite-based tandem technologies are highly promising. In this work, the resource demand of the emerging perovskite PV technology is investigated, considering two factors of supply criticality, namely mining capacity for minerals, as well as production capacity for synthetic materials. Overall, the expansion of perovskite PV to a multi-terawatt scale may not be limited by material supply if certain materials, especially cesium and indium, can be replaced. Moreover, organic charge transport materials face unresolved scalability challenges. This study demonstrates that, besides the improvement of efficiency and stability, perovskite PV research needs also to be guided by sustainable materials choices and design-for-recycling considerations

Towards long term sustainability of c-Si solar panels: the environmental benefits of glass sheet recovery

The cover glass in a silicon solar panel accounts for about 2/3 of the device's weight. Recycling these devices at their end-of-life is fundamental to reducing the industry's environmental impact. Here we investigate the recovery of these glass sheets by a heat-assisted mechanical process. A panel was delaminated, and we have utilized Fourier-transform infrared, Raman, and energy-dispersive spectroscopies to confirm the composition of the remaining components and identify aging signals. The results demonstrate that the panel's design was similar to most Silicon solar panels in the market, and we concluded that it would be feasible to recover the glass in most of these devices. Due to its chemical and mechanical strength, this glass would be ready to be reused without the need to melt it again, bringing substantial savings in its energy content and carbon emission related to its production. The glass sheet would be ready to be used as cover glass in another solar panel or architecture material. Our estimates showed that this could be a pathway to reducing the photovoltaic industry's carbon emissions by more than 2 million tonnes per year.Comment: 11 pages, 5 figure

Speaking Truth To Power: Why Energy Distribution, More Than Generation, Is Africa's Poverty Reduction Challenge

This paper revisits the roles that energy plays in poverty reduction. First, while energy does not reduce poverty itself, it delivers energy services. These services can improve poor people's welfare both directly by enhancing their own productivity, education and health, and indirectly by changing the economy around them. The paper provides a simplified framework for thinking about these energy services, and then reviews the literature on their importance to poverty reduction. From this framework, we draw a series of three important conclusions about energy priorities and their implications for poverty reduction and development.Tackling energy poverty will have less to do with ambitious expansion of electricity capacity, and more to do with ambitious distribution of energy services to poor people.Expansion in centralized power generation serves industry, the services sector and already-connected households, before it serves the poor.Distributed, clean energy interventions are best suited to tackling energy poverty -- and poverty more generally