Copper battery for heat to power conversion and energy storage

An important part of the electricity production relies on heat conversion. Indeed power plants burn fuels like natural gas, coal or use nuclear fission to produce heat that can be transformed into electricity through a thermodynamic cycle and the mechanical work of a turbine. However, with such methods, high efficiencies are only reached with high temperatures according to the Carnot theory. Large amounts of waste heat or low-temperature heat are not converted into electrical power during these processes and are usually simply not exploited. Therefore, there is an opportunity to improve the way in which the heat is used and especially for electricity production, if waste heat can be recovered. Low-grade heat (below 200 â) is available in vast quantities from industry, but also from renewable sources such as solar thermal or geothermal energy. As renewable energies are often available intermittently during specific time of the day or according to the season, the storage of the low-temperature heat coming from these sources is particularly interesting for a more efficient distribution and consumption. However, production of electric power from these heat sources is challenging with existing technologies. Thermally regenerative batteries allow both the conversion and the storage of thermal energy into electric power, but they suffer from low operation voltages and low output powers. Here, we propose a thermally regenerative flow battery based on copper complexation with acetonitrile in non-aqueous solutions operating at voltages above 1V. Cu(I) complex can be destabilized by removal of acetonitrile by distillation, leading to production of solid copper and Cu(II) in a solution of propylene carbonate, thereby charging the battery. With this reaction, we demonstrate the electricity production at power densities up to 200 WÂ·mâ2, and estimate the theoretical efficiency of the full system between 5-14%. The results demonstrate a proof-of-concept for producing and storing electricity from low-quality heat.

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

Thermally regenerative copper nanoslurry flow batteries for heat-to-power conversion with low-grade thermal energy

Hubert Girault, Sunny Isaïe Maye, Pekka Eero Peljo

Low-grade heat (below 200 °C) is available in vast quantities from industry, or from standard roof-top solar thermal collectors. However, the production of electric power from these heat sources is challenging with existing technologies. Thermally regenerative batteries allow both the conversion and the storage of thermal energy into electric power, but they suffer from low operation voltages and low output power. Here, we propose a thermally regenerative nanoslurry flow battery based on copper complexation with acetonitrile in non-aqueous solutions operating at voltages above 1 V. The Cu(I) complex can be destabilized by the removal of acetonitrile by distillation, leading to the production of solid copper nanoparticles and Cu(II) in solution, thereby charging the battery. We demonstrate the electricity production at average power densities of 90 W m−2 and peak-power densities up to 150 W m−2, and estimate the theoretical efficiency of the full system at 2%. The results demonstrate a proof-of-concept for harvesting and storage of electricity from low-quality heat.

2020

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.