By Bruno De Wachter / Published on Tue, 2009-09-15 05:30
Integrating road networks and power networks
The US Department of Transportation has awarded funding for building a 'solar highway' prototype. A solar highway contains photovoltaic (PV) modules covered with bulletproof glass as a road surface. The surface also contains a grid of LEDs that can light the roadway, draw lines, and flash warnings that react to traffic sensors. Apart from supplying power for the LEDs and sensors, the energy generated by the PV modules will also be used to heat the highway when required. The remaining energy can be used for houses and businesses alongside the road. If this systems works as projected, it could well make power stations and power lines superfluous. According to an article on Matter Network, covering all American roads with this system would produce an annual yield of energy three times as large as the entire U.S. energy consumption in 2006.
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By HDK / Published on Sat, 2009-09-05 09:30
In this project, we propose a new methodological framework for assessing the economic impact of transmission investment. This framework improves on the current state of art by explicitly modeling strategic responses of generators to transmission investments. Using an economic measure of social benefit, results show that transmission planning should lead rather than follow generation investments. As a result, transmission investments should be treated as infrastructure development in the same general way that roadway investments are used for regional development.
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By Roman Targosz / Published on Fri, 2009-06-05 16:30
The CNEE is a conference that was initiated and sustained by Society of Power Engineers in Romania (SIER) and it is taking place ones at every two years.
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By Peter Vaessen / Published on Wed, 2009-01-28 19:37
Several European countries have policies to encourage the development of renewable energy sources. This is identified in, for example, the European green paper Energy strategy for a sustainable, competitive and secure energy supply (March 2006).
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By Hans De Keulenaer / Published on Wed, 2008-10-15 13:01
A recent report from IEA explores how variable renewables can be integrated on a large-scale into the electricity system.
The report proposes to replace the term 'intermittency' with 'variability'. Calling renewables intermittent is misleading, since wind or solar power do not drop from full power to zero and vice versa - they are available at some level much of the time, and ramp up or down following gradients dictated by weather.
The main theme of the report is that hosting capacity of the electricity system for variable renewables can be much larger than previously reported, provided that a number of
measures are taken to increase system flexibility. The approach
recognises the problem, but offers solutions.
A number of
strategies are presented to smooth the effect of variability or to
increase flexibility of the electricity system to absorb it.
Smoothing factors:
- system-wide aggregation: aggregating wind or solar power over a wider area reduces variability
- Aggregation of the output of different generation technologies
- Better forecasting
Flexibility sources:
- Fast-response capacity in the generation portfolio
- Availability of storage
- Stronger interconnections of transmission systems
- Demand-side management and response
While there is no intrinsic ceiling to hosting variable renewables,
current networks may be inadequate for large-scale incorporation.
Substantial changes to networks and system operation will be needed.
And whatever the mix of above solutions adopted, there remains large
uncertainty on the cost and reliability of the resulting system.
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By Hans De Keulenaer / Published on Mon, 2008-09-08 07:46
Digital simulation is a powerful mean to predict the voltage dip performance of a power network. Voltage dip characteristics can be accurately reproduced using present simulation tools and a stochastic prediction procedure that could incorporate the random nature of the voltage dip causes and the behaviour of sensitive equipment during this type of events.
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By Bruno De Wachter / Published on Thu, 2008-06-26 05:30
And what must be done to ensure the future security of supply?
Experts seem to agree on the fact that the current U.S. electric grid has room for improvement. The rise in the number of blackouts in the US over the last twelve years clearly demonstrates this fact (see my post of 2 June.) However, opinions differ on how dramatic the situation really is.
In an opinion article in the Energy Bulletin, Gail Tverberg paints a very dark picture. If a major upgrade of the grid is not undertaken, it will be necessary to seriously downscale expectations concerning the free trade of electric power, renewable energy, and plug-in vehicles. She even foresees a situation in which some areas of the country may be forced into planned blackouts. In my experience, things are rarely as bad as they may seem at first, but consider this an interesting thought experiment from her pessimistic point of view. It reminds us of the fact that we should not take the high reliability of electric supply for granted, neither in the US, Europe, nor any developed region.
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By Bruno De Wachter / Published on Thu, 2008-06-19 05:30
Extreme weather conditions might increase failure rate
How will higher temperatures due to climate change influence the efficiency of electricity transmission and distribution? Last April, Nastaran Rahimi posed this interesting question in the Leonardo Energy forum. Stefan Fassbinder replied by making the rough estimate that a temperature rise of 2°C would increase network losses by 0.04% of the total throughput. This conclusion, if correct, is a fairly negligible effect compared to other network losses. The idea that ‘climate change increases network losses, increasing climate change in their turn’ does not hold.
This conclusion does not mean that climate change will have no influence on the electrical system. The main negative consequence will be operation and maintenance issues due to extreme weather conditions. A relatively small global temperature increase can change local climates, leading to a significant increase of days with potentially harmful extreme weather.
One such extreme condition is summer drought. Sergio Ferreira has already reported that in the summer of 2007, ‘several nuclear and other power plants had to be shut down due to very hot ambient and river water temperatures in Western Europe (particularly in France)’. A study in 2007 by the Finnish research institute VTT shows that many other climate issues could affect the reliability of the electrical system.
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By Hans De Keulenaer / Published on Wed, 2008-06-18 13:10
By G Blajszczak
The paper describes importance of the reactive power control basing on the failures and control problems in the Polish transmission networks in summer 2006. A detailed description of the operational difficulties is provided. Conclusions, repairs and prevention undertaking are also described.
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By Hans De Keulenaer / Published on Wed, 2008-06-11 00:00
By Sompop Pattanariyankool and Lester B. Lave
Northeastern United States whose capacity factors are 29-34%, we calculated the optimal size of the transmission line connecting the wind farms to distant customers. For a distance of 500 miles, the optimal transmission capacity is about 86 %; for a 1,000 mile separation, the optimal transmission capacity is 75 %. Building a line at full capacity would increase transmission cost almost 15 % while transmitting only about 4% more electricity to the customer.
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By Hans De Keulenaer / Published on Tue, 2008-02-19 18:20
This page is a live document to support the discussion webinar on the above topic before and after the event. We look forward to reading your comments on this page.
This webinar will discuss the European Commission's Proposal for a Directive on the Promotion of the Use of Energy from Renewable Sources. The webinar starts with a briefing on the proposal, followed by a discussion on its strong and weak points.
Indicative list of discussion points (other points may arise depending on participants):
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By Bruno De Wachter / Published on Thu, 2008-01-17 08:30
The NERC 2007 Long-term Reliability Assessment
Last October, the North American Electric Reliability Corporation published its '2007 Long-term Reliability Assessment'. The conclusions of this study are more than a little alarming. The North-American grid is ageing rapidly and it is no longer adequate to cope with today’s energy landscape, containing large quantities of renewable energy systems. Transmission capacity continues to lag behind demand and will need to increase by more than 10 per cent over the next 10 years. According to the Assessment, there is also the need to develop reliable storage capacity to better manage demand.
The cost of building a high capacity, integrated, and smart grid system is estimated to be $100-150 billion. However, the economic impact associated with a failing grid would quickly amount to the same order of magnitude.
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By Hans De Keulenaer / Published on Thu, 2008-01-03 14:22
By D Ilisiu
Transelectrica is the Romanian Transmission and System Operator (TSO). In the company's activities, the Power Quality aspects are very actual and important.
First part of the paper contains the standards and technical requirements regarding the Power Quality aspects included in Romanian technical code of the Electricity Transmission Grid. The reference concerns only the high voltage grid.
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By Bruno De Wachter / Published on Thu, 2007-11-15 08:30
Removing bottlenecks to allow free trade
Enhancing the European transmission grid is important for three closely interwoven reasons:
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To allow power transport to compensate for the intermittent output of renewable energy systems
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To enable free trade in electrical power within the EU
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To ensure a continuous power supply throughout the EU
In spite of the importance of these changes, grid enhancement is progressing very slowly. There are several reasons for this. First, current European regulations do not allow Transmission System Operators to build up the necessary investment capital to undertake large scale infrastructure works. Second, the environmental impact assessments of overhead lines take a great deal of time. The European landscape is already densely built, so it is normal that each new construction project must be thoroughly investigated regarding its necessity.
While many involved parties have recently been urging faster grid enhancement, this does not mean that no progress is being made at all.
New cross-border transmission lines
This month, the new 700 MW subsea interconnector between Norway and the Netherlands will be inaugurated.
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By Bruno De Wachter / Published on Thu, 2007-09-27 13:09
The mixed blessings of Distributed Generation (DG)
There are two probable paths that can lead to favouring distributed generation (DG):
- When DG is seen as an ideal in itself which we should aim at for technical and/or socio-economical reasons. The fact that many DG systems make use of renewable energy is seen as just one of the overall advantages.
- Or when the reduction of CO2 emissions is the ultimate goal. Renewable energy and cogeneration systems that reduce CO2 emissions are typically small scale, which leads automatically to a more distributed generation.
That last argument is becoming far less convincing as renewable energy farms continue to grow in size and output. The largest renewable energy plants are reaching the size of fossil fuel power plants. Texas hosts a wind farm with a capacity of 735 MW. A PV plant of 11 MW is operating in Portugal, one of 40 MW is being built in Germany, and one of 300 MW is planned in New Mexico. So to what degree generation should be distributed or centralized is a choice we have to make, even for renewables. And both concepts seem to present mixed blessings.
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