By Hans De Keulenaer / Published on Tue, 2010-02-02 13:49
In order to combat global warming, a detailed knowledge of the greenhouse gas (GHG) emissions associated with different energy conversion technologies is important. For nuclear energy, GHG emissions result from different process stages of the whole fuel cycle. A life-cycle assessment offers the opportunity to properly calculate these emissions. In the past, both indirect energy use and GHG emissions were studied by many researchers. Most of the studies result in low indirect emissions comparable to windturbines.
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By Hans De Keulenaer / Published on Fri, 2006-10-27 13:34
This study analyses the auctions organised by power exchanges in Europe. Power exchanges are institutions that facilitate wholesale trade in electric energy. Most exchanges organise separate auctions day ahead for every hour of the next day. Generators, large consumers, suppliers and traders fine-tune their portfolios via these trading platforms.
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By Hans De Keulenaer / Published on Sun, 2006-06-18 13:18
The optimal placement for distributed generation units
An increasing number of Distributed Generation units, using renewable sources or not, is connected to the distribution grid. That requires new concepts for developing those grids. The influence on grid stability is already well studied. The following paper from KULeuven's ESAT/Electa group tackles the optimal placement of the DG units on the grid, decision strategies and the correlation with real-time control.
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By Hans De Keulenaer / Published on Sun, 2006-05-14 12:55
A new paper from KULeuven gives an overview of the regulations in 6 European countries on periodic inspection of electricial installations, finding major differences in the designation of authorised electricians, control mechanisms, statutory regulations, conditions for connection, periodic controls, kind of inspection and tax benefits
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By Bruno De Wachter / Published on Mon, 2006-04-17 05:15
An important effect on the distribution system
The output of photovoltaic (PV) systems is variable. It has daily and seasonal variations according to the position of the sun. In moderate climates, short term fluctuations in solar irradiance caused by moving clouds are just as important. What is the impact of these variations on the voltage level of the distribution grid? A major question bearing future large-scale application of embedded PV Systems in mind. A new paper by KU Leuven investigates this impact.
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By Hans De Keulenaer / Published on Tue, 2006-03-21 11:13
A SWOT analysis by the KULeuven (Belgium) On the grid, an instantaneous balance between electricity production and highly variable demand needs to be maintained. In the past, it was not economically feasible to make widespread use of storage systems to relieve this stringent requirement, but times have changed. Since the liberalisation of the energy market and the increasing use of (variable) renewable energy sources, the role of the grid and its power quality has gained importance, creating new market opportunities for storage systems.
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By HDK / Published on Thu, 2006-03-16 13:02
Electricity markets of the EU member states are too weakly integrated to create a truly European market. That is the point of view of the following paper by the ESAT-Electa group of the KULeuven. It explains how the current situation has come about, before proposing a step-by-step plan to link national markets. The latter is crucial to stabilize prices, avoid local market power abuse, and consolidate best practices.
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By Hans De Keulenaer / Published on Thu, 2006-02-16 18:07
During the last decades, wind power has known an immense growth over the world, and particularly in Europe. The traditionally mentioned advantages are the infinite availability of the ‘fuel’ (wind), and the fact that wind turbines produce electricity without emitting carbon dioxide or other toxic gases.But can wind power be installed without limits, in a country like Belgium? Except for the lack of space, there is the difficulty that wind power is never as reliable as conventional power plants, because wind can never be predicted with unlimited accuracy, let alone controlled.
However, accurate prediction and control is necessary. The European electricity grid is divided in a number of control areas. The grid operator in each control area (e.g. Elia in the control area Belgium – Luxembourg) makes sure that the instantaneous power production in its area is always equalto the total consumption. Otherwise, the grid becomes instable, with severe disturbances resulting from it. Because the grid operator can never know in advance the exact amount of total power consumption in its control area, an amount of ‘regulatingpower’ is needed: this consists of power plants that can control their output power or that can be put into service within a very short timeframe, to immediately respond to load fluctuations.
With an increasing number of wind turbines connected to the grid, more regulating power is required. While the variation of power consumption in a control area is well predictable, because it shows the same pattern every day, the power production by wind turbines is much less predictable. When the wind speed is high and all wind turbines are operating at full power, the risk that the wind speed suddenly drops must always be taken into account. In that case, the system depends on the regulating power. Regulating power consists of e.g. turbojets, well controllable but consuming a lot of fossil fuel. With high penetration of wind power in a control area, the uncertainty of power production becomes an order of magnitude higher than was previously the case. The turbojets will operate more, as a consequence the total fuel consumption and carbon dioxide emissions of all power plants together will possibly be higher than for a scenario with less wind power.
What if the wind turbines are geographically well spread over the control area, rather than all turbines installed close to each other in large wind farms? Is there then a high probability that always somewhere in the control area there will be much wind, and somewhere else not, making sure that the fluctuations of total power production by the aggregated wind park are limited? The answer is no. The correlation between wind speeds in Belgium is very high, or, when the wind speed changes in the coastal region, the probability is high that de wind speed changes to the same extent at the same hour in Brussels or elsewhere. The advantage of spatially distributing wind turbines over the control area is only relevant when large areas can be considered, e.g. Western Europe. Unfortunately, it is at this moment technically not feasible for a large region such as Western Europe to operate permanently as a single control area. This would result in large and unpredictable power flows between the actual control areas, requiring high investment costs for reinforcement of the many congested high voltage lines connecting the different control areas.
Then how far can you go with wind power in Belgium? The conclusion of the thesis is that in Belgium there is space – from the electrotechnical point of view – for 500 to 700 MW of wind power, or 250 to 350 medium-sized turbines. From then on, the negative effect of the extra required regulating power becomes relevant. Considering that nearly 200 MW is installed in Belgium by now, and 216 MW will possibly be constructed offshore in a near future, this limit is already relatively near. Meanwhile, it is worth the effort to look for alternatives for responding to the increased demands of regulating power. ‘Demand side management’ (actively controlling the power consumption, as a function of the available power) is a very promising option for this.
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By Hans De Keulenaer / Published on Mon, 2006-01-23 18:29
Date: February 16, 2006 - 14h00 Europe Standard time
Duration: 1 hour
Speaker: Joris Soens, KULeuven
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By Hans De Keulenaer / Published on Thu, 2006-01-12 14:29
Efficiency of induction motors is very much debated these days. Different standards are used in the world, making actual manufacturer numbers hard to compare. Therefore, in 1997-1998 18 motors of 11, 55 and 75 kW have been tested in the laboratory of the Electrical Engineering department at the KULeuven.
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