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Renewable Energy penetration: the upcoming challenges for TSOs April 4, 2008

Posted by Hans De Keulenaer in grids, reliability, renewable electricity, wind.
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40.8% of the overall electricity demand was supplied on real time basis by wind power some days ago in the Spanish electricity system. This record constitutes a real challenge for transmission system operators (TSOs).

In more general terms, renewable energy penetration strongly depends on the ability of TSO to evolve towards a new way of operating the system: dedicated predictability for renewable generation, voltage dip management and managing the power balance.

The big issue for the coming years (especially taking into account the targets set by the EU Directive on the use of energy from renewable sources) is balancing the transmission system in the presence of high renewable power penetration. This not only requires to redesign grid codes, but also a deep revision of power reserve policy. Along with renewable sources growth, a market for upgraded reserves is becoming necessary.

This paper shows some good practices from the Spanish TSO, REE, leading to better integration of renewable generation: commissioning a dedicated centre for renewable energy management, grid code evolution, development of specific applications to maximize renewable generation and provide production limits to each renewable energy plant, voltage control and congestion management.

Howto manual – photovoltaics April 2, 2008

Posted by Hans De Keulenaer in distributed generation, electricity, photovoltaics, renewable electricity, renewables.
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“I heard about feed-in tariffs for photovoltaics: would it make sense to install panels in my roof ?”. “I have troubles with the power coming from the grid. How can I make more reliable the power supply?”.

This manual explains how a photovoltaic system works, what is the most suitable solution in your case and, if it makes sense, how to start planning and building your small scale photovoltaic installation.


The current promotion by governments of distributed and renewable generation creates opportunities for individuals and small scale developers. This manual is part of a series dedicated to small scale renewables.

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Finding good sites for wind turbines is not so easy January 5, 2007

Posted by Hans De Keulenaer in renewable electricity, wind.
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Wind farms in England and Wales are failing to generate the predicted amount of electricity

A study by the Renewable Energy Foundation shows that England and Wales are not windy enough to generate electricity at the rates projected for them. Government targets are based on wind farms running at 30% of capacity. But most farms in England and Wales are generating only around 25%. The two poorest performers have rates of no more than 7.7% and 8.8% respectively.

In the UK, only the wind farms in Scotland and those on the Orkney and Shetland isles run above 30% of capacity. But those sites face other problems. They are far from the main consuming areas, so significant amounts of electrical power are lost in transmission. Moreover, they are often located in ecologically sensitive areas. One example is the projected wind farm on the Isle of Lewis in the Outer-Hebrides. The site is controversial since it is located near important bird sanctuaries (see article in the Sunday Times).

This illustrates how difficult it has become to find acceptable sites for wind farms in Europe. The Renewable Energy Foundation has concluded that the most effective sites for wind energy are off-shore near major cities.


Article on Telegraph.co.uk

Electricity maps of UK June 22, 2006

Posted by Hans De Keulenaer in renewable electricity.
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Courtesy Deloitte & Touche LLP, an electricity map of UK, showing major power stations (>500 MW) and transmission infrastructure.
uk electricity

From the same source, also a renewables map of UK, showing the single offshore wind farm in the UK at North Hoyle, but some more in an advanced stage of construction. However, a lot more seems to be in progress on hydro-power and biomass.

uk renewables

Pathways to 2050 – towards an ‘all’ electrical society May 10, 2006

Posted by Hans De Keulenaer in carbon management, efficiency, nuclear, renewable electricity, roadmap, security.
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Challenging climate change caused by carbon emissions is such a many-sided problem, involving many actors from all over the world, that it is absolutely necessary to set clear and realistic goals. That is what the World Business Council for Sustainable Development (WBCSD) did in its paper Pathways to 2050 (pdf – 3 MB).

The WBCSD unites 180 international companies who share the commitment to sustainable development through economic growth, ecological balance and social progress. In their paper on energy and climate change (December 2005), they describe three paths to 2050.

emission paths

Business as usual

If we don't react, global carbon emissions will rise from 7.8 Gigatons in 2002, to some 12 Gt in 2030 and 15-16 Gt by 2050. In that case, the atmospheric CO2 concentration will rise up to 1,000 ppm. The resulting temperature rise cannot be predicted accurately, but it might be as high as 3-4°C by 2100 and up to 6°C by 2300. It goes without words that such an enormous temperature rise will have far-reaching consequences.

An optimistic scenario

A figure that is sometimes postulated is to reduce the global carbon emissions to half of its current value. In that case, the carbon concentration is expected to rise to 450 ppm, causing a temperature rise of 1 up to 2.5 degree C by 2100. Bearing in mind that the global energy demand will at least double, even if we put a lot of effort in energy efficiency, this is clearly an optimistic scenario that would require far more drastic measures than the ones we are applying today.

A realistic scenario

More realistic would be – according to the WBCSD – to bring back the carbon emissions to the current value by 2050. This would limit the atmospheric concentration to 550 ppm and the temperature rise to 1,5 up to 3° C by 2100. It would allow carbon emissions to increase in the medium term, and require a global downturn by 2025, followed by a continuous decline. Realistic but ambitious, this scenario would still require sectorial shifts and significant changes in energy production and use.

The energy mix for electricity production

In the realistic scenario, the WBCSD sees the share of electricity in the total energy consumption double by 2050. The growing importance of electricity is the result of following trends:

  • improvements in electrical applications, and substitution of fossil fuels in end use
  • increasing number of electrical appliances
  • information technology and the internet
  • urbanisation

energy share

Since the total energy consumption itself is expected to double by 2050, this means that the electricity production should quadruple. The energy mix for the power generation could be as follows:

energy mix

Source % in mix Growth compared to 2002
Wind (+ geothermal, tidal, and wave energy) 25% x 160
Solar 12% x 300
Biomass and waste 5% x 18
Hydro 8% x 2
Nuclear 10% x 2
Natural Gas 20% x 3
Coal with Carbon Capture and Storage 20% x 2

Half of the electricity production will come from renewable sources. To realize this, solar, wind and biomass should see a very steep and continuous growth. Mind that coal fired power stations are still in the mix, but are equipped with Carbon Capture and Storage (CCS) systems. Also nuclear energy is still growing according to this scenario, meaning that the currently operating plants will have to be replaced and new capacity should be installed.

Voltage fluctuation caused by PV Systems April 23, 2006

Posted by Hans De Keulenaer in photovoltaics, power quality, renewable electricity.
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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. The input consists of pseudorandom time series of solar irradiance values, based on measurements. Power-flow calculations determine the impact of solar irradiance variations on the grid voltage. The results allow assessing in which case super-capacitors to mitigate fluctuations are worth the cost.