September 3rd

Can LED lighting deliver?

Incandescent lamps are cheap but tend to have short lifetimes. The light emitted by incandescent sources is perceived as particularly pleasant because these hot radiators generate a continuous (or full) emission spectrum. But this very fact means that they waste much of the electrical energy supplied to them. Compact fluorescent lamps (CFLs) are actually the least compact of all the various lamps commercially available at present (Figure 1).

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Harmonic Domain Modelling of Transformer Core Nonlinearities Using the DIgSILENT PowerFactory Software

This paper demonstrates the results of implementation and verification of an already existing algorithm that allows for calculating saturation characteristics of singlephase power transformers. The algorithm was described for the first time in 1993. Now this algorithm has been implemented using the DIgSILENT Programming Language (DPL) as an external script in the harmonic domain calculations of a power system analysis tool PowerFactory [10]. The algorithm is verified by harmonic measurements on a single-phase power transformer.

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September 2nd

Exploitation of renewable power sources for local consumers reservation

Rapid growth of Latvian economy resulted in rapid growth of electricity demand in cities and rural regions. Consumers’ reliability requirements are increasing, but improvement of reliability is directly related to electricity supply reservation possibilities in case of one or more network components failure. This article describes conditions for independent operation of decentralized renewable power supply sources, evaluates its exploitation possibilities and feasibility for local consumers’ reservation.

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Interharmonics

Interharmonics are voltages or currents with a frequency that is a non-integral multiple of the fundamental supply frequency, while each harmonic frequency is an integral multiple of the supply frequency.  Interharmonics, always present in the power system, have recently become of more importance since the widespread use of power electronic systems results in an increase of their magnitude.

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August 29th

Concentrating photovoltaics - Industry views

Concentration photovoltaics (CPV) offers one of the most promising utility-scale, renewable energy technology options. Many companies are testing their CPV products and some have already launched commercial offers.

This documentary presents interviews with some industry representatives present at ISFOC (CPV Institute in Puertollano, South of Spain).

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August 28th

Power Quality Monitoring System—Voltage Dips, Short Interruptions and Flicker

The Israel Electric corp. deployed a nationwide Power Quality Monitoring System (PQMS). The PQMS monitors the quality of supply of all of its high voltage costumers, as well as a sample of its medium voltage customers. The PQMS monitors both the voltages and the currents. The PQMS has been operational since October 2005. The paper presents preliminary measurement results obtained from the PQMS.

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Climate change: pay now or ask for credit?

An ethical as well as an economic question

If we continue business-as-usual, climate change — according to both the worst prognoses and the more optimistic ones — will confront humanity with serious consequences and a high price tag. However, the cost to society of mitigating climate change by reducing greenhouse gas emissions is also high. So inevitably, the question arises: what we should do? Pay today for mitigating climate change or pay later to deal with its consequences?

This question is most often presented as a mere economic problem. Not so, says John Broom in the Scientific American article 'The ethics of climate change'. The answer, he maintains, also entails ethical decisions.

John Broom refers to the 'Stern Review on the Economics of Climate Change' by Nicolas Stern and the UK Treasury, and to the studies of William Nordhaus at Yale University. While Stern concludes that urgent action to control Greenhouse Gas emissions is required, Nordhaus’s position is that the need to act is not acute. Broom identifies and explains the premises at the basis of this contradictory outcome.

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August 22nd

Distributed Generation and Renewable Energy Sources in Poland

Nowadays, in many countries the increase of generating capacity takes place in small units of so-called distributed generation (DG), and among them in hybrid power (generating) systems (HPS). They use primary energy conventional sources as well as renewable energy sources (RES), and in many cases produce electricity and heat (CHP). It is very often that definition of distributed generation is connected with definition of renewable energy sources.

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Control of a DFIG-based wind system in presence of large grid faults: analysis of voltage ride through capability

In this paper, the authors study a variable speed wind generation system based on Doubly Fed Induction Generator (DFIG) in case of large balanced voltage dip and analyzed a remedial solution that allows for the turbine to stay connected and helps grid recovery through reactive power injection, by supplying the grid with reactive power during faults. Simulation results show the effectiveness of the solution in different operating points of the four working regions of the power-speed turbine characteristic.

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August 21st

The contributions of American cities to global warming

A ranking according to carbon footprint per capita

As centres of energy consumption, the US metropolitan areas should play a leadership role in fighting climate change. That was the starting point for the report 'Shrinking the Carbon Footprint of Metropolitan America' by The Brookings Institution. The report investigates

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