Effects of time resolution on finances and self-consumption when modeling domestic PV-battery systems

When modeling a renewable energy system, the timestep to use is an important consideration. Timestep, or time resolution, can have an impact on results, influencing the sizing of the system and whether or not to invest at all. In this work, real measured data for an entire year at 15-s resolution from a rooftop PV array and 8 household loads in the UK are used. The PV and load time series are averaged to lower resolution: 1-min, 5-min, 30-min and 1-h, and the results from using them as input to a 25-year simulation of PV-only and PV-battery systems are compared to the 15-s resolution results. Load resolution is confirmed to be more important than PV resolution for improving accuracy of self-sufficiency and cost metrics; the presence of a battery is confirmed to reduce the errors of using low resolution compared to PV-only. However, these findings only apply to the commonly tested Greedy algorithm but not the newly developed Emissions Arbitrage algorithm. A wider range of metrics are calculated here than in previous work, finding consistency in that low resolution overstates the benefits of PV-battery, but variation in percentage difference across the metrics used. Further aspects not studied before include: the diminishing returns in computation speed when time resolution is lowered, and the effect of time resolution on the tipping point when certain configurations become more attractive propositions than others. Time resolution of input data and modeling are issues not only for researchers in academia and industry, but from a consumer protection perspective too

Rotor eddy current power loss in permanent magnet synchronous generators feeding uncontrolled rectifier loads

Analytical methods and transient finite element analysis (FEA) with rotating mesh are used to calculate rotor eddy current power loss in a permanent magnet synchronous generator (PMSG) connected to an uncontrolled bridge rectifier. Two winding and rectifier topologies are considered: a 3-phase winding with a 3-phase bridge rectifier and a double 3-phase winding with a 3-phase rectifier each, connected in series. Both magnet flux tooth ripple and stator MMF harmonics are considered in the calculation of rotor loss; the harmonics are added vectorially. Good agreement is observed between analytical and FEA for constant dc link current and constant voltage loads. The machine with double 3-phase windings was found to have considerably lower rotor losses that the machine with one single 3-phase winding

A dynamic unit cell model of the all-vanadium redox flow battery

n this paper, a mathematical model for the all-vanadium battery is presented and analytical solutions are derived. The model is based on the principles of mass and charge conservation, incorporating the major resistances, the electrochemical reactions and recirculation of the electrolyte through external reservoirs. Comparisons between the model results and experimental data show good agreement over practical ranges of the vanadium concentrations and the flow rate. The model is designed to provide accurate, rapid solutions at the unit-cell scale, which can be used for control and monitoring purposes. Crucially, the model relates the process time and process conditions to the state of charge via vanadium concentrations

The continuing development of Magnéli phase titanium sub-oxides and Ebonex® electrodes

Magnéli phase titanium sub-oxides were identified (via x-ray diffraction) in the 1950s as a distinct series of electrically conducting compounds having the general formula TinO2n-1 where 3 < n < 10. Early research on the characterisation of materials based on TinO2n-1 has been well documented. This concise review, which is illustrated by data from the literature and our own laboratory, concerns more recent research on Magnéli phase titanium oxide materials. A brief overview of chemical and physical properties is followed by the applications of electrode materials based on these titanium oxides. Energy conversion technologies (particularly batteries and fuel cells) are shown to be a continued area of research that particularly suits the relatively high electrical conductivity and chemical stability inherent in these materials

Electrodeposition of composite coatings containing nanoparticles in a metal deposit

Recent literature on the electrodeposition of metallic coatings containing nanosized particles is surveyed. The nanosized particles, suspended in the electrolyte by agitation and/or use of surfactants, can be codeposited with the metal. The inclusion of nanosized particles can give (i) an increased microhardness and corrosion resistance, (ii) modified growth to form a nanocrystalline metal deposit and (iii) a shift in the reduction potential of a metal ion. Many operating parameters influence the quantity of incorporated particles, including current density, bath agitation (or movement of work piece) and electrolyte composition. High incorporation rates of the dispersed particles have been achieved using (i) a high nanoparticle concentration in the electrolyte solution, (ii) smaller sized nanoparticles; (iii) a low concentration of electroactive species, (iv) ultrasonication during deposition and (v) pulsed current techniques. Compositional gradient coatings are possible having a controlled distribution of particles in the metal deposit and the theoretical models used to describe the phenomenon of particle codeposition within a metal deposit are critically considered

An environmental perspective on developing dual energy storage for electric vehicles - a case study exploring Al-ion vs. supercapacitors alongside Li-ion

Much focus of dual energy storage systems (DESS) for electric vehicles (EVs) has been on the cost reduction and performance enhancement. While these are important in the development of better systems, environmental impacts of system and component level choices should not be overlooked. Current interest in EVs is primarily motivated by environmental reasons such as climate change mitigation and reduction of fossil fuel use, so it is important to develop environmentally sound alternatives at the design stage. Assessing the environmental impact of developmental and mature chemistries provides valuable insights into which technologies to select now and which to develop for the future. This paper presents a cradle-to-gate (i.e., all raw material and production elements are considered however the ‘use’ phase and recycling are not) lifecycle assessment of a DESS with Li-ion and aqueous Al-ion cells, and one with Li-ion cells and supercapacitors. These are also compared to a full Li-ion EV battery in terms of their environmental impact for both a bus and car case study. Key findings show that the use of a DESS overall reduces the environmental impacts over the vehicle lifetime and provides an argument for the further development of aqueous Al-ion cells for this application