Material constraints related to storage of future European renewable electricity surpluses with CO2 methanation

The main challenges associated with a growing production of renewable electricity are intermittency and dispersion. Intermittency generates spikes in production, which need to be curtailed when exceeding consumption. Dispersion means electricity has to be transported over long distances between production and consumption sites. In the Directive 2009/28/EC, the European Commission recommends sustainable and effective measures to prevent curtailments and facilitate transportation of renewable electricity. This article explores the material constraints of storing and transporting surplus renewable electricity by conversion into synthetic methane. Europe is considered for its mix of energy technologies, data availability and multiple energy pathways to 2050. Results show that the requirements for key materials and land remain relatively low, respecting the recommendations of the EU Commission. By 2050, more than 6 million tons of carbon dioxide might be transformed into methane annually within the EU. The efficiency of renewable power methane production is also compared to the natural process of converting solar into chemical energy (i.e. photosynthesis), both capturing and reenergizing carbon dioxide. Overall, the production of renewable methane (including carbon dioxide capture) is more efficient and less material intensive than the production of biofuels derived from photosynthesis and biomass conversion. (C) 2016 Elsevier Ltd. All rights reserved.

Integrated Solid Oxide Fuel Cell

Emanuele Facchinetti

Distributed power generation and cogeneration of heat and power is an attractive way toward a more rational conversion of fossil and bio fuels. Solid oxide fuel cell (SOFC) – gas turbine (GT) hybrid systems are emerging as the most promising candidates enabling the achievement of a cleaner and more efficient conversion of a large variety of resources across a broad power range covering from small to medium scale applications. This thesis introduces an innovative concept of SOFC-GT hybrid system that allows reaching efficiencies higher than the state of the art while enabling the carbon dioxide separation and avoiding fuel cell pressurisation technical issues. Several hybrid system design alternatives based on this concept are analysed through a thermodynamic optimisation approach combining process modelling, advanced process integration techniques and multi-objective optimisation. A number of optimal hybrid system configurations are determined for different design targets. The results consistently demonstrate the higher energy conversion performance and flexibility enabled with respect to the state of the art. The innovative concept analysis is extended to two applications for which SOFC-GT hybrid cycles are expected to provide the most significant impact toward sustainability: the small scale distributed generation and the conversion of renewable resources. A simplified version of the new hybrid system layout is especially developed for small scale distributed generation, typical of residential building applications (5-10 kWel). Experimental data are used to prove the technical feasibility of the system and to assess the performance potentially achievable with currently feasible technologies. The results of the analysis underline that energy conversion efficiencies higher than traditional centralised power generation can be achieved even at such a small scale. A systematic process integration and optimisation approach is used to assess the energy conversion performance of the original SOFC-GT hybrid cycle fuelled with hydrothermally gasified wet waste biomass. The analysis highlights the considerable potential of the integrated system that allows for converting wet waste biomass into electricity with First Law efficiency higher than 60% while simultaneously enabling the separation of the biogenic carbon dioxide.

EPFL2012

Investment and production costs of synthetic fuels - A literature survey

Guillaume Boissonnet, Emanuela Peduzzi

Synthetic fuels, or synfuels, can be produced from gas, coal and biomass. The conversion of gas and coal is well established but lignocellulosic biomass conversion is slow to develop. This paper addresses the issue of the production cost of second generation biofuels via the thermo-chemical route, biomass to liquids (BtL). Techno-economic studies help identify promising conversion processes, but also introduce a false confidence in the technology that may lead to ill fated decisions. A large number of techno-economic studies have been published since the year 2000 showing a large variability in the results. This paper analyses the published data and presents causes of the observed variability, including a comparison with coal and gas to liquids. Large uncertainties remain however with regard to the precision of the economic predictions. It will be shown that the spread in the economic source data accounts for much of the spread in the predictions. These uncertainties affect both CtL and BtL cost predictions. It will be shown however that the results are relatively coherent and that most of the differences between the costs of synthetic fuels can be traced back to economies of scale considering mature technology. (C) 2014 Elsevier Ltd. All rights reserved.

Elsevier2014

Thermo-environomic evaluation of the ammonia production

François Maréchal, Matthieu Perrenoud, Laurence Tock

Within the global challenge of sustainable energy supply and greenhouse gas emissions mitigation, carbon capture and storage and the deployment of renewable resources are considered as promising solutions. In this study the production of ammonia mainly used in the fertilizer industry and responsible for around 2-3% of the world greenhouse gas emissions is analyzed. Considering natural gas and biomass as a resource and the option of CO2 capture and storage, different process configurations are systematically compared with regard to energy, economic and environmental considerations. A consistent thermo-environonomic optimisation approach combining flowsheeting, process integration techniques, economic performance evaluation, life cycle assessment and multi-objective optimisation is applied for the conceptual process design and competitiveness evaluation. It is highlighted that the quality of the process integration is a key factor for improving the performance by valorizing the heat excess through electricity cogeneration. Including CO2 mitigation in the ammonia production allows to reduce the emissions, but leads to a slight efficiency decrease due to the energy consumption for the CO2 compression. For the natural gas fed process yielding an energy efficiency around 65%, the overall life cycle emissions can be reduced to 0.79kgCO2/kgNH3 with CO2 capture compared to 1.6kgCO2/kgNH3 without capture. Considering the biogenic nature of the carbon in the biomass, the emissions drop to -1.79kgCO2/kgNH3 for the biomass process having an energy efficiency of 50%. The economic competitiveness highly depends on the resource price and the introduction of a carbon tax. This study reveals the potential of the decarbonisation of the fertilizer industry. This article is protected by copyright. All rights reserved

Wiley-Blackwell2015

Integrated Solid Oxide Fuel Cell

Emanuele Facchinetti

EPFL2012