Internal resistance

Résumé

In electrical engineering, a practical electric power source which is a linear circuit may, according to Thévenin's theorem, be represented as an ideal voltage source in series with an impedance. This impedance is termed the internal resistance of the source. When the power source delivers current, the measured voltage output is lower than the no-load voltage; the difference is the voltage drop (the product of current and resistance) caused by the internal resistance. The concept of internal resistance applies to all kinds of electrical sources and is useful for analyzing many types of circuits. Battery A battery may be modeled as a voltage source in series with a resistance. These types of models are known as equivalent circuit models. Another common model being physiochemical models that are physical in nature involving concentrations and reaction rates. In practice, the internal resistance of a battery is dependent on its size, state of charge, chemical properties, age,

Source officielle

https://en.wikipedia.org/wiki/Internal_resistance

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Ce cours propose une introduction à l'électrotechnique. Les lois fondamentales de l'électricité et différents composants d'un circuit électrique linéaire seront étudiés. L'analyse élémentaire des circuits en régime continu et sinusoidal sera aussi couverte.

Le cours aborde les bases des circuits électriques composés d'éléments linéaires, en régime continu. Une série de méthodes de transformations sera traitée. Le régime alternatif est traité en fin de semestre (calcul complexe). De nombreux exemples ainsi que des démonstrations illustrent le cours.

Ce cours vise à transférer les concepts théoriques et les savoir-faire nécessaires à la réalisation de mesures de bonne qualité. Les contenus méthodologiques et technologiques seront exposés sous forme ex-cathedra et les savoir-faire seront entrainés lors des travaux pratiques.

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22.6 A fully integrated counter-flow energy reservoir for 70%-efficient peak-power delivery in ultra-low-power systems

Yao Shi

Recent advances in circuits have enabled significant reduction in the size of wireless systems such as implantable biomedical devices. As a consequence, the battery integrated in these systems has also shrunk, resulting in high internal resistances (~10kΩ). However, the peak-current requirement of power-hungry components such as radios remains in the mW range, and hence cannot be directly supplied from the battery. Therefore, duty-cycled architectures such as pulsed-based radios have been proposed that transmit a short burst (~1μs) of high power (~10mW) supplied by an internal energy storage capacitor [1-3]. The capacitor is then recharged using a current limiter to protect the battery from excessive droop. This paradigm raises two challenges: 1) to supply sufficient energy, very large capacitance (>50nF) is often needed (200mV droop, for 10mW and 5μs), leading to large die area or bulky off-chip discrete components; 2) only a small fraction (~5%) of energy stored in the capacitor is actually delivered to the high power components since the capacitor can only be discharged by a few 100s of mV while maintaining proper circuit operation (Fig. 22.6.1).

IEEE2016

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A Fully Integrated Counter Flow Energy Reservoir for Peak Power Delivery in Small Form-Factor Sensor Systems

Yao Shi

We present a fully integrated energy reservoir unit using a counter flow method for peak power delivery in space-constrained sensor systems. Recent advances in circuits have enabled significant reduction in the size of wireless systems such as implantable biomedical devices. As a consequence, the batteries integrated in these systems have also shrunk, resulting in high internal resistances (~10 kQ). However, the peak current requirement of power-hungry components such as radios remains in the milliwatt range and hence cannot directly be supplied from the battery. Therefore, an energy reservoir with high output power but small size is required. We present an efficient energy reservoir that dynamically reconfigures a storage capacitor array using a so-called counter flow approach. By creating a voltage gradient on capacitor arrays and moving the capacitors along the slope of the gradient, the supply voltage can be maintained while the energy stored in the reservoir is delivered efficiently to the load. The counter flow energy reservoir delivers 65% of stored energy before recharging is needed which allows up to a 12× reduction in overall capacitor size compared with our implementation of the previous method. The design supplies up to 13.6-mW output power for 1 μs. We demonstrate the proposed concept with a pulsed radio, showing an 11.5× increase in pulse length compared with the previous method.

IEEE2017

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Scale-up of phosphate remobilization from sewage sludge in a microbial fuel cell

Christos Comninellis, Thomas Egli, Fabian Fischer, Alain-François Grogg, Marc Sugnaux, Géraldine Zufferey

Phosphate remobilization from digested sewage sludge containing iron phosphate was scaled-up in a microbial fuel cell (MFC). A 3 litre triple chambered MFC was constructed. This reactor was operated as a microbial fuel cell and later as a microbial electrolysis cell to accelerate cathodic phosphate remobilization. Applying an additional voltage and exceeding native MFC power accelerated chemical base formation and the related phosphate remobilization rate. The electrolysis approach was extended using a platinum-RVC cathode. The pH rose to 12.6 and phosphate was recovered by 67% in 26 h. This was significantly faster than using microbial fuel cell conditions. Shrinking core modelling particle fluid kinetics showed that the reaction resistance has to move inside the sewage sludge particle for considerable rate enhancement. Remobilized phosphate was subsequently precipitated as struvite and inductively coupled plasma mass spectrometry indicated low levels of cadmium, lead, and other metals as required by law for recycling fertilizers. (C) 2015 Elsevier Ltd. All rights reserved.

Elsevier Sci Ltd2016

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