Dataset concerning the hourly conversion factors for the cumulative energy demand and its non-renewable part, and hourly GHG emission factors of the Swiss mix during a one-year period (2016 and 2017)

The provided data are the hourly CO2-eq emission factors, and the hourly conversion factors for the cumulative energy demand and its non-renewable part for the Swiss electricity mix over one year (2016 and 2017). These data have been assessed on the base of an inventory of the technology used for electricity generation and an attributional life-cycle approach according to the methodology presented in [1]. Compared with [2], electricity imports from Italy to Switzerland are not neglected anymore, and lead to more accurate output data. The utility of the proposed data lies in the multiple possible applications. The presented data are necessary for conducting a life cycle assessment of all processes and products using electricity in Switzerland. Moreover, the presented data could serve as a sustainable benchmark of electricity when implementing renewable energy systems and energy storage. Because of their temporal accuracy, the hourly conversion factors enable the development of energy management strategies taking into account the time-dependent life cycle impacts. Finally, they can be used for the quantitative follow-up of the decarbonization process of the grid electricity at the national level over a given lapse of time.

Redox dual-flow battery for combined electricity storage and hydrogen production

Danick Reynard

The energy transition towards a carbon-neutral and sustainable economy is one of the greatest challenges of the 21st century to combat global warming and pollution. The decarbonization process is affecting every sector of the economy (electricity, transportation, industrialâŠ). For power generation, renewable energy resources are realistic alternatives to replace fossil resources such as gas and coal. However, the intermittent nature of wind and solar power limits their penetration into the conventional grid and increases the need for energy storage (battery, hydrogen storageâŠ) for smoothing out fluctuations between electric supply and demand. In this context, the concept of the redox dual-flow battery was introduced to propose a hybrid storage solution that can store electrical energy both electrochemically and in the form of hydrogen fuel. The system differs from a traditional redox flow battery by including a secondary energy platform, in which the electrolytes can be discharged chemically in external catalytic reactors through redox-mediated water electrolysis to produce clean hydrogen. The dual storage feature improves the flexibility and enhances significantly the capacity of the system by storing energy beyond the capacity of the electrolytes in the form of hydrogen. Additionally, the redox-mediated water electrolysis offers several advantages over conventional electrolysis in terms of safety, durability and purity. In this thesis, the proof-of-concept of a dual-flow circuit using a vanadium-manganese redox flow battery for combined electricity storage and hydrogen production is demonstrated. The redox flow battery employs vanadium sulfate (V3+/V2+) and manganese sulfate (Mn3+/Mn2+) dissolved in concentrated sulfuric aqueous solution as negative and positive electrolyte, respectively. The galvanic cell achieves energy efficiency of 68% at a current density of 50 mAÂ·cmâ2 (cell voltage =1.92 V) and a relative battery energy density 45% higher than the conventional all-vanadium RFB in the same conditions. Once charged, the electrolytes can be spontaneously discharged through redox-mediated oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in RuO2 and Mo2C catalytic reactors, resulting in an energy consumption for hydrogen production of ca. 50 kWh/kg H2. The system provides a competitive alternative for large-scale energy storage in renewable energy and transport applications.

EPFL2022

Thermoeconomic Analysis of a Solar Enhanced Energy Storage Concept Based on Thermodynamic Cycles

Samuel Henchoz

Large scale energy storage may play an increasingly important role in the power generation and distribution sector, especially when large shares of renewable energies will have to be integrated into the electrical grid. Up to now pumped-hydro is the only technology that has been widely used for that purpose. However the spread of this technology is limited by geographic constraints. In the present work, a particular implementation of the storage concept based on thermodynamic cycles, as introduced by ABB Switzerland ltd. Corporate Research, has been analysed thermoeconomically. This concept can be scaled up to a GWh range of stored energy, and is site independent. The underlying idea is to use electricity to power a heat pump transferring heat from a cold source to a hot source (charging mode), while storing the heat and the cold at both sources. Subsequently the energy that has been stored/removed to/from the hot/cold sources can be used to run a heat engine, hence re-delivering the electricity when it is needed (discharging mode). In the implementation presented here, using the ambient temperature as the hot source for both the heat pump and the heat engine allows taking benefit from daily variations of the atmospheric temperature. Indeed, the heat-pump can operate with a higher Coefficient of Performance (CoP) during the night and the heat-engine at higher efficiency during the day. This results in an effective increase of the ratio between the redelivered electricity (discharge) and the stored electricity (charging), compared to a situation where the hot source of both cycles are at the same temperature. The use of solar collectors is a further way to enhance this ratio by increasing the hot source temperature above the ambient temperature during the day. In charging mode, the system consists in an ammonia based Rankine heat pump interfaced at the evaporator with a latent heat cold storage, and at the condenser to the ambient through aircoolers. In discharging mode an ammonia based Rankine heat-engine is interfaced at the condenser with the latent heat cold storage, and the evaporator(boiler) of the thermal engine is interfaced with hot water produced by a field of flat plate solar collectors. A steady state multiobjective optimization of a 50 MW power output plant was carried out, with the objectives of minimizing the investment costs, and maximizing the ratio between electricity output and input. Several types of cold storage substances have been implemented in the formulation and two different types of solar collector were investigated. A storage efficiency of 57% at a cost of 1200 USD/kW was calculated for an optimized plant using solar energy. Finally, a computation of the behaviour of the plant along the year was carried out, reaching a yearly availability of 84.4%.

Pergamon-Elsevier Science Ltd2011

Sustainable energy systems, a process system engineering perspective

François Maréchal

According to the International Energy Agency, CO2 emissions have to be cut by a factor 2 if one wants to mitigate the effect on the climate change to an acceptable limit. To reach this target, efficient use and conversion of energy resources is expected to count for more than 50% of the mitigation effort, while renewables and CO2 capture will take an additional 30% . In its recommendation to governments, efficiency is therefore declared by the IEA as being the hidden fuel of the future energy system and will be the 21st century challenge for engineers. At the level of the sustainable energy system design, one could define the challenges as corresponding to the following actions : efficient energy use and reuse to supply energy services and products, efficient energy conversion with CO2 capture, sequestration or valorisation, the proper integration of renewable energy resources and the large scale energy system integration. Process system engineering is an engineering method that supports decision for the process design. In the talk, we will discuss how such techniques can be adapted for the design of sustainable energy systems. We will first discuss how system design methodology has to be adapted to incorporate sustainability indicators by considering life cycle assessment methods. We will then discuss the application of process integration and system engineering techniques to design more sustainable energy systems. We will first analyse the problem of the efficient energy usage and conversion in industrial processes. Examples show that adopting a holistic approach considering heat requirement, energy conversion and waste management can reach very high energy savings. For the process designs, the method is using multi-objective optimisation techniques to generate innovative integrated process designs. Applied to the development of fuel cells systems, innovative designs with electrical efficiencies as high as 82 % can be reached opening new perspectives for cogeneration, CO2 capture and biomass conversion. The design and the integration of biomass conversion processes to produce biofuel , electricity and heat is another example of the application of process system engineering techniques. Synthetic natural gas production with efficiencies as high as 75 % can be obtained. Such plants can also be used as a way to convert power to fuel or as long term renewable electricity storage. The large scale system integration considers the industrial processes and energy conversion unit as decentralised and interconnected combined heat and power plants with connections to smart electrical, heating and cooling district grids. The ultimate system integration considering the use of process system engineering methods to develop industrial ecology concepts will then be presented. In industrial ecology concepts the goal is to reveal synergies between mobility, living, products and waste management services, energy conversion technologies integration and endogenous renewable resources at the level of a community.

2013