A sustainable and reliable
electricity system
Inevitable and challenging
Inaugural address
Professor Mart A.M.M. van der Meijden
10 February 2012
Cover image:
A sustainable and reliable
electricity system
Inevitable and challenging
Inaugural address
Professor Mart A.M.M. van der Meijden
Delivered in an abbreviated form on 10 February 2012 upon accession to the office of Professor of
Large Scale Sustainable Power Systems
in the faculty of Electrical Engineering, Mathematics and Computer Science of Delft University of Technology
Contents
The demand for energy is growing 5
Limits to growth 6
A sustainable energy supply is inevitable 6
European ambition 7
Trend scenarios 8
The power of the sun 9
The power of wind 9
The power of imagination (Pathway to 2050) 10
Electricity as the energy carrier par excellence 12
Development of the electricity system in the case of large-scale introduction of
renewable energy 14
Developments in the electricity infrastructure 15
Local 15
National and international (centralised) 16
TenneT Transmission System Operator 17
Developments in transmission systems onshore 17
Developments in offshore transmission systems 20
Keeping balance 24
System integration 27
Conclusion 29 References 31
Rector Magnificus, Sir,
Members of the Executive Board,
Fellow professors and other members of the university community, Highly esteemed audience,
Ladies and gentlemen,
My inaugural address is a unique opportunity to share with you how generating elec-tricity from renewable sources on a large scale in the future could affect our elecelec-tricity grids. I argue that the use of the abundantly available renewable energy sources is inevitable, both locally and on a large scale.
My address concerns the necessary electricity transmission system of the future and the challenges that our future engineers will face if we want to guarantee a sustainable and reliable electricity system in the long term.
You may be wondering why renewable energy wouldn’t be reliable. During this inaugural address I will address this in detail and explain that the problem is highly complex. A system is reliable if it satisfies the user’s requirements. If the system’s possi-bilities deviate from those requirements, it becomes unreliable. So ensuring that the electricity system remains reliable requires measures with regard to electricity genera-tion (improving the predictability of the supply), transmission (ensuring flexibility and controllability) and customers (promoting energy awareness).
The demand for energy is growing
Energy consumption in Europe has grown tremendously in the last 150 years (see Figure 1) [ECF 2010]. This growth has sped up since the Second World War. The first energy crisis in 1973 and the second energy crisis in 1979 are merely visible as dips.
The question is: How will energy consumption in Europe evolve in the future? Energy consumption is growing worldwide. The world population reached 7 billion last year, and is expected to climb to 9 billion by 2050. There are currently 1.3 billion people without access to electricity [IEA 2011a]. The standard of living is improving in China, India and (hopefully also in the future) in Africa, with more and more people entering the middle class. This means that the demand for energy is increasing substantially. The demand for energy is expected to rise by one-third between 2010 and 2035 [IEA 2011b], and is even expected to double worldwide between now and 2050 [Shell 2011].
Limits to growth
We all know that raw materials and fuels are finite resources, even if new discoveries are made in the future. There are limits to the emission of pollution and greenhouse gases.
These messages have been given to us numerous times, for example by the Club of Rome in 1972 with “The Limits to Growth” [Meadows1975], the Brundtland Commission in 1987 with “Our Common Future” [Brundtland 1987], the Intergovernmental Panel on Climate Change (IPCC) in 1988 stating that global warming is caused by the emission of greenhouse gases [IPCC 2007] and Al Gore in 2006 with his film “An Inconvenient Truth” [Gore 2006].
Figure 2: Sustainable development
A sustainable energy supply is inevitable
The Brundtland Commission’s definition concerning sustainable development is an important source of inspiration for me: “Humanity has the ability to make development sustainable – to ensure that it meets the needs of the present without compromising the ability of future generations to meet their own needs” (Figure 2). For me the definition essentially answers the question: What is it about?
Not exhausting the raw materials and fuels of future generations.
Although we do not have an energy shortage in this fossil fuel age, there is a surplus of natural resources that we are not using today. The Stone Age did not end because there were no more stones. So what it’s about is taking a different approach to the energy issue.
How can we handle our need for energy in a responsible manner? How can we mini-mise the consequences for the environment? How can we reduce CO2 emissions? Trias Energetica has a very concise answer to these questions:
1. first, save energy (for example through thermal insulation),
2. then use renewable energy sources (such as solar, wind and biomass energy), 3. and supplement this with the efficient use of fossil fuels where necessary.
European ambition
A sustainable and reliable energy supply does not stop at our Dutch borders, but is an Europe-wide issue. I therefore welcome the long-term view of the European Commission, as it gives us a common long-term direction – a point on the horizon (Figure 3). The European Commission aims to achieve a low-carbon economy by 2050. In other words, an 80-95% reduction in CO2 emissions by 2050 compared to 1990. Saving energy and using renewable energy sources play an important role in this ambition.
The European Commission’s ambition 20-20-20 targets by 2020
80%-95% C02 reduction by 2050 (reference: 1990)
Figure 3: European long-term ambition
Before addressing the consequences of moving towards a low-carbon economy, I would like to say something about future scenarios.
Trend scenarios
The future of the energy supply is difficult to predict, particularly when it comes to the long term. Aiming to achieve a low-carbon economy, as mentioned above, is an example of a target scenario. However, there are numerous developments in progress, which reinforce or counteract one another. This is a complex matter, on the basis of which the effects on the electricity supply and the associated demand for electricity transmission and energy services must be determined. Within my company TenneT we therefore work with different trend scenarios (Figure 4). Trend scenarios are not predic-tions, but descriptions of possible futures, and a way of testing assumptions. They are also a way of being better prepared for the future.
The scenarios are differentiated by the direction in which a development progresses. The first degree of freedom (on the vertical axis) is the environment, with the develop-ment towards a sustainable society at one end of the scale and a society whose energy economy continues to rely on fossil fuels at the other.
The second degree of freedom (on the horizontal axis) is often a combination of market forces and geographic orientation, with a completely free global market at one end of the scale and a strictly regulated regionally or locally oriented market at the other.
The blocks describe the playing field in which possible future scenarios take place. This is described in more detail in Visie2030 [TenneT 2008]. This method will also be introduced within ENTSO-E1 in the near future as a basis for long-term studies. I am unable to predict the degree and rate at which renewable energy will develop. I think it is more important to understand what this potential development signifies for the electricity transmission system. During my speech I will therefore pay attention to the potential of renewable energy sources and their influence on the electricity trans-mission system. By way of illustration, I would now like to focus on two examples of large renewable energy sources.
The power of the sun
If we were to place a collector in the Sahara that could ideally collect all the thermal solar energy needed to meet the electricity demand for the whole world, what would its surface area be? The German Aerospace Centre (DLR) has calculated that a surface area of 300 km by 300 km would be sufficient in terms of energy2,3 [DLR 2009]. Just imagine the power of the sun.
Figure 5: The power of the sun (source: German Aerospace Centre)
The power of wind
There are many ambitions and plans in Europe for the generation of electricity from wind energy. For example, for EU-27 the European Wind Energy Association (EWEA) foresees an installed capacity of 400,000 MW by 2030 and an installed wind capacity of 600,000 MW by 2050. See Table 1. The current peak in the European electricity demand 1 ENTSO-E is the European network of 41 Transmission System Operators for electricity.
2 We are talking about energy here, without taking the conversion into power into account.
is 521,000 MW [ENTSO-E 2010]. The European Wind Energy Association expects 50% of the electricity energy demand to be met by wind energy by 2050. In addition to wind on land, a substantial proportion of wind capacity from the North Sea is anticipated: 150,000 MW by 2030 and 350,000 MW by 2050. To put things into perspective: China is not sitting idly by. With support from the International Energy Agency (IEA), a China Wind Energy Development Roadmap has been developed for China, outlining a plan for an installed wind power capacity of 1,000,000 MW by 2050 [IEA 2011b].
Table 1: EWEA wind scenario [EWEA 2010], [GEWEC 2011]
2010 2020 2030 2050
Installed wind capacity 84 GW 230 GW 400 GW 600 GW
Of which offshore capacity 3 GW 40 GW 150 GW 350 GW
Percentage of wind productie 4,8% 14% 33% 50%4
Figure 6: Ambitious development of onshore and offshore wind energy in Europe
The power of imagination (Pathway to 2050)
In 2009, I was involved in the development of the Pathway to 2050 of the European Climate Foundation (ECF). The European Climate Foundation set out a pathway to 2050 in which it implements the European Commission’s ambition to achieve a low-carbon economy (80-95% CO2 reduction by 2050 compared to 1990) in different ways. Besides energy conservation, the degree to which renewable energy sources are utilised for electricity (40%, 60% and 80%, respectively) was studied.
4 For EU-27, the EWEA assumes a total electricity consumption of 4,000 TWh on the basis of substantial
Figure 7: “Pathway to 2050” of the European Climate Foundation (ECF)
The report concludes that the long-term social costs of a fossil fuel economy and a low-carbon economy are of a similar magnitude [ECF 2010]. The low-carbon economy is primarily characterised by the high capital costs compared to the high operating costs of the fossil fuel economy. The generation of electricity from wind and solar energy requires more up-front investments compared to coal and gas-fired power plants. But once the solar panels and wind turbines are in place, except for maintenance costs, operating costs are relatively low . The wind and the sun are free, whereas fuel must be purchased constantly for coal and gas-fired power plants.
A low-carbon economy makes society less dependent on fossil energy sources from politically unstable countries, protects the environment, creates jobs and increases competitiveness in the long term5.
Renewable energy sources in Europe and northern Africa
In 2009, the Desertec Foundation presented the following image showing renewable energy sources throughout Europe and northern Africa [DLR 2009]. Concentrating Solarthermal Power6 (CSP) in northern Africa and southern Europe, building-integrated PV panels in central and southern Europe, wind energy in coastal areas and in the North 5 “The Roadmap 2050 shows that the benefits of the low-carbon transition by far outweigh the challenges
and that a commitment now to a systemic low-carbon transformation of the energy sector is ultimately the winning economic strategy for competitiveness, jobs and low-carbon prosperity. Achieving the 80% GHG reductions target in 2050 based on zero carbon power generation in Europe is technically feasible and makes compelling economic sense.” [ECF 2010]
6 Concentrating Solar-thermal Power (CSP) is a technology for collecting solar energy in the desert. It involves
the use of solar heat to power steam turbines and generate electricity. This heat can also be stored in heat storage tanks so that electricity is available on demand, even at night.
Sea, the Irish Sea and the Baltic Sea. Geothermal energy in southern Europe, hydroelec-tric power in Norway, the Alps, the Pyrenees and the Atlas Mountains.
Biomass in central and eastern Europe. Europe’s strength lies in the diversity of renew-able energy sources, each with its own characteristics. In the future the European trans-mission network will be able to change the direction of the electricity flows, depending on the supply of renewable energy. For example, wind from the North Sea or solar energy from southern Europe and the northern part of Africa.
Figure 8: Renewable energy sources in Europe and northern Africa (source: Desertec Foundation)
Electricity as the energy carrier par excellence
The demand for energy is growing, and the demand for electricity is growing even faster. The share of electricity in the total global demand for energy is also increasing. The International Energy Agency (IEA) has estimated that the share of electricity will increase from 16% in 2006 to 18% in 2015 (Table 2). In the Netherlands the share of electricity in 2006 was 14% due to the amount of gas available. In its reference scenario the IEA expects electricity to make up approximately 21% of the total global demand for energy in 2030.
Table 2: Global final energy consumption by sector in Mtoe (IEA reference scenario) [IEA 2008]. 1980 2000 2006 2015 2030 2006-20307 Industry 1779 1879 2181 2735 3322 1.8% Coal 421 405 550 713 838 1.8% Oil 474 325 329 366 385 0.7% Gas 422 422 434 508 604 1.4% Electricity 297 455 560 789 1060 2.7% Other 165 272 307 359 436 1.5% Transport 1245 1936 2227 2637 3171 1.5% Oil 1187 1844 2105 2450 2915 1.4% Biofuels 2 10 24 74 118 6.8% Other 57 82 98 113 137 1.4% Residential, services and agriculture 2006 2635 2937 3310 3918 1.2% Coal 244 108 114 118 100 -0.5% Oil 481 462 472 493 560 0.7% Gas 346 542 592 660 791 1.2% Electricity 273 613 764 967 1322 2.3% Other 661 910 995 1073 1144 0.6% Non-energy use 348 598 740 876 994 1.2% Total 5378 7048 8086 9560 11405 1.4%
Electricity is one of the fastest growing forms of energy in the end use of energy world-wide. The European Commission’s aim for a low-carbon economy is also leading to a greater use of electricity in the final energy demand. In its low-carbon scenario, the European Commission expects the share of electricity in the total final energy demand to grow to 36%-39% in 20508 (see Figure 9) [EC 2011] – a doubling of the current share. There are a number of reasons for this. The growth of information technology is leading to increased use of new information and communication devices. More and more elec-trical devices are purchased as the economy grows. Saving energy on heating/cooling buildings generally leads to a greater use of electricity. For example, gas-fired central heating boilers are being replaced by high-efficiency electric heat pumps (which involve a lower use of fossil fuels in the total chain). Electrically powered passenger cars and light trucks are replacing traditional cars powered by fossil fuels. In transportation this form of energy saving leads to a greater use of electricity. Improved efficiency in indus-trial processes is also leading to more, and more efficient, applications of electricity.
7 Average annual rate of growth
8 According to the current trend scenarios the European Commission expects at the shape of sustainable
Share (%) of electricity in the total final energy demand 2005 2010 2015 2020 2025 2030 2035 2040 2045 20% 15% 25% 30% 35% 2050 40%
Range for low-carbon scenarios
Range for current scenarios
In the generation of energy many renewable sources can be unlocked most efficiently in the form of electricity.
Figure 9: Share of electricity in Europe in the current trend and in the low-carbon scenarios [EC 2011]
Development of the electricity system in the case of
large-scale introduction of renewable energy
I will provide examples of changes in the electricity system associated with the large-scale introduction of sustainable energy based on four different angles:
1. Developments in the electricity infrastructure 2. Developments in transmission systems on land 3. Developments in offshore transmission systems 4. Maintaining balance (creating flexibility)
Developments in the electricity infrastructure
Today the electricity supply is still essentially one-way traffic (see Figure 10), from the power plant to the customer.
Figure 10: One-way distribution [Sluis 2011] / illustration: Eric Verdult
In the transition towards tomorrow’s low-carbon economy we see two different, seem-ingly contradictory developments in the extensive development of renewable energy sources at the local level and at the national and international level. What influence does this have on the electricity infrastructure?
Local
A low-carbon economy requires a substantial increase in the local production of elec-tricity among consumers and businesses (roof-integrated solar PV, small wind genera-tors, combined heat and power generation, fuel cell electric cars connected to the grid). Consumers who produce their own electricity are also referred to as prosumers. This means that the end user increasingly feeds back into the electricity grid (two-way traffic) (see Figure 11). The electricity distribution system will have to be adapted to this in the future with the addition of new network technologies and new intelligence. My position is this: there are tremendous opportunities for locally produced energy, with efficient production of both heat and electricity. However, not all electricity can be generated locally in the future.
Figure 11: Two-way distribution [Sluis 2011] / illustration: Eric Verdult
National and international (centralised)
The electricity transmission system already uses two-way traffic and is already charac-terised by a high level of intelligence. What effect would a low-carbon economy have on the electricity transmission system? An important property of natural flow sources (such as solar, wind, tidal and wave energy) is that the energy density is relatively low. These sources are characterised by a wide geographical distribution, as I have already shown on the map of Europe.
Renewable electricity is generated where the natural resources are found. Low energy density means that large surface areas are needed in order to provide electrical energy. For example, large wind energy farms are built in less populated areas or at sea, so at greater distances from population centres (see Figure 11). This results in more elec-tricity transmission over a greater distance. A number of other developments are under way that are leading to an increase in electricity transmission in high volumes and/or over great distances. I will give three examples. The increase in cross-border transmis-sion as a result of the integration of European electricity markets (market coupling). Building traditional power plants at greater distances from electricity consumption centres (for example, new coal, biomass and gas-powered plants can be planned for the Dutch North Sea coast, due to the availability of cooling water, favourable climate for establishing businesses and the presence of ports for the supply of fuels). Phasing out power plants in the vicinity of electricity consumption centres, with old power plants not replaced on site, but at greater distances from where the electricity is consumed. At this point I would like to introduce my employer TenneT.
TenneT Transmission System Operator
Nowadays TenneT is an international Transmission System Operator (TSO) for the transmission of electricity (see Figure 12). With approximately 20,000 km of high-voltage lines and 36 million end users in the Netherlands and Germany, TenneT ranks among the top 5 electricity grid operators in Europe. TenneT is working hard to facilitate the European market integration for electricity, the safeguarding of the security of supply and the integration of renewable energy sources. TenneT is currently working on the development of 9 “power sockets” in the North Sea to connect offshore wind farms with a total capacity of 5000 MW.
Figure 12: TenneT 400 kV (red) and 220 kV (green) transmission network
Developments in transmission systems onshore
The highest voltage level of the European transmission grid is currently standardised at 400 kV (Figure 13). As capacity increases, the transmission distance for High Voltage Alternating Current (HVAC) transmission systems becomes a limitation. The voltage differences in high-capacity transmissions in long AC connections increase, resulting in a risk of instability in the electricity system.
Figure 13: Lattice tower HVAC 400 kV2 x 2000 MVA (photo: TenneT)
Higher transmission capacity can be achieved by increasing the AC voltage, for example from 400 to 750 kV. Higher voltage is accompanied by sections with higher towers. Corridors with higher towers for the higher AC transmission voltage in Europe are expected to be met with great resistance from the public.
Furthermore, large-scale transmission over one single connection is associated with higher risks with regard to the reliability of the electricity supply. Any failures for what-ever reason must be able to be absorbed. Research is needed on the risks of large-scale transmissions over great distances.
High Voltage Direct Current (HVDC) connections have smaller voltage differences than AC connections and the transmission distances for HVDC connections are unlimited in theory.
The classic Current Source Converter High Voltage Direct Current (CSC-HVDC) can only provide point-to-point connections. The above-ground version can transmit great capacities over great distances (Figure 14 shows an 800 kV HVDC line in China with a capacity of 5000 MW). These towers are taller than the current Donau towers. Due to the maximum transmission capacity of the connecting cables, the capacity of the underground version is limited (to 1000-1500 MW). If part of a grid fails, the CSC-HVDC cannot start itself up again, as a result of which this technology is not suitable for inte-gration in the AC grid.
Figure 14: Lattice tower 800 kV HVDC, China, 5000 MW (photo: Siemens)
The new VSC HVDC can start itself up again if a section of the grid fails. VSC HVDC can be implemented with branches (multi-terminal), which is desirable for the efficient inte-gration of HVDC into the transmission grids. The incorporation of multi-terminal VSC HVDC into the meshed AC system requires research on matters such as DC breakers, the use of ICT, security concepts, control algorithms and control concepts.
VSC HVDC provides opportunities for voltage support on the AC grid, as a result of which this technology can contribute to grid stability. Further research is also required in this area.
A possible development in the long term is that HVDC systems are used primarily for the national and international transmission of bulk electricity over long distances, while HVAC systems are increasingly used to transmit electricity regionally.
The large-scale integration of renewable variable sources in the electricity system, the complementation of the internal electricity market and ensuring reliability require the necessary adjustments to the electricity transmission system at the national, cross-border and European levels. So there is still plenty of interesting research to be done by universities and the industry.
Developments in offshore transmission systems
We will consider three alternative technologies for the connection of offshore wind farms [ENTSO-E 2011a] (Figure 15).
Figure 15: Diagram of three offshore transmission technologies
High Voltage Alternating Current (HVAC) transmission systems are used to connect offshore wind farms near the coast to the mainland transmission grid by means of submarine cables. In general AC cables are used for short distances. An example is the connection of the Princess Amalia Wind Farm located 23 kilometres off the coast of IJmuiden (Figure 16). An important limitation for all types of AC cables is formed by their high electrical capacitive properties: the cable acts as a capacitor. This means that the capacitive charging current becomes considerable for longer cable lengths. This results in a reduction in the possibility of transmitting active power. The negative effect of these cable charging currents increases as the voltage increases. For practical purposes the maximum length of AC connection is between 60 and 100 km. This has led to the use of HVDC technology in longer offshore connections. HVDC cables are not affected by the charging current limitations that affect AC cables, and in theory the transmission distances for HVDC cables are unlimited.
Figure 16: Offshore Princess Amalia Wind Farm (photo: Eneco)
As indicated earlier, there are two more possible technologies within HVDC. Current Source Converter High Voltage Direct Current (CSC HVDC) transmission systems, also known as conventional HVDC. These have been applied since the 1970s for the offshore connection of synchronous grids between different countries. An example is the NorNed interconnector between the Netherlands and Norway (Figures 17 and 18).
Figure 18: NorNed HVDC converter station (photo: TenneT)
A characteristic of this technology is that the AC/DC converter stations require a large surface area thus taking up a large amount of the scarce space available.
An important limitation of this conventional HVDC is that the system must be connected to a strong AC network on both sides. Therefore CSC HVDC is not suitable for the radial connection of offshore wind farms to the mainland transmission grid. Furthermore, CSC HVDC connections are usually point-to-point connections, to which it is difficult to connect wind farms in between.
Voltage Source Converter High Voltage Direct Current (VSC HVDC) transmission systems are relatively new (in use since 1997) and are used to connect offshore wind farms located far from the coast to the mainland transmission grid by means of submarine cables.
An important characteristic of this technology is that the system does not have to be connected to a strong AC network on both sides. Therefore VSC HVDC is suitable for the radial connection of offshore wind farms to the mainland transmission grid. Because they require fewer filters, the VSC HVDC converter stations are much smaller than the conventional converter stations. Thanks to the limited weight and volume of the converter stations this technology is suitable for use on offshore platforms (Figure 19). The new VSC HVDC can be implemented in multi-terminal networks, which provides the possibility of connecting multiple offshore wind farms to a single connection.
The multi-terminal facility enables the smart combination of connections of offshore wind farms and interconnectors between two countries. This is an important property for being able to optimise the architecture of the transmission grid.
The image in Figure 20 shows a schematic example of a possible development of the future offshore grid in the North Sea. There are currently several HVDC interconnectors, such as NorNed between Norway and the Netherlands and BritNed between Great Britain and the Netherlands. The first wind farms will be connected to the national grid individually, starting with the coastal locations, and further inland later on. Multiple interconnectors will be installed between North Sea countries in stages. The wind energy farms will be built further and further from the coast and the connections will be combined with interconnectors by means of the multi-terminal VSC HVDC. This is part of TenneT’s vision.
I think it is important to consider the development of the international exchange of elec-tricity, offshore renewable energy generation and the development of the grid onshore in an integral manner.
I conducted a long-term study with a number of my ENTSO-E colleagues. ENTSO-E published the results in the spring of 2011 – an initial long-term vision for 2030 in which the advantages of the integrated development of the offshore electricity infrastructure [ENTSO-E 2011 b] were made visible. An increase in transmission capacity for the cross-border market with a 10% reduction in investments.
Keeping balance
Electricity cannot be directly stored on a large scale. The supply and demand of elec-tricity on the elecelec-tricity grid must be in balance. If this balance is disrupted for too long, this can result in a blackout. A regional balance must also be maintained. The perma-nent monitoring, maintenance and restoration of the balance in the Netherlands is one of the tasks of TenneT Transmission System Operator.
Figure 21: Electricity must always be in balance
Balancing supply and demand / flexibility in the Netherlands today
In the Netherlands parties are free to purchase or sell electrical energy to whomever they like. Parties enter into purchase and sales contracts for these transactions. These transactions lead to transmissions via the electricity grid. In practice the actual produc-tion and/or consumpproduc-tion do not always proceed in line with the agreements. Therefore a system is needed to manage the differences between forecasts and actual usage. In the Netherlands we currently have a system of programme responsibilities, in which a limited number of large parties, such as major electricity producers, large industrial customers, traders and electricity suppliers (Figure 22) play a crucial role. This system of programme responsibility (“production follows consumption”) works well in the
Netherlands, because only a limited amount of electricity is generated from variable energy sources (solar and wind) in proportion to the total adjustable production system. In principle, the parties responsible for the programme can even out the fluctuations with their own generation units or through contracts. There is sufficient flexibility in the current system in the Netherlands.
Figure 22: Traditional adjustable capacity for balancing supply and demand
Balancing supply and demand / flexibility in the future
Balancing supply and demand becomes a challenge when electricity is increasingly generated from variable renewable energy sources that are non-adjustable or only adjustable to a limited extent and for which the actual production volume is difficult to predict far in advance.
Greater demands will be placed on the flexibility of the energy system and on the flexibility of the electricity system in particular. The current method based on “produc-tion follows consump“produc-tion” will no longer suffice in that case. This brings about a new challenge. New solutions and new parties (local, national and international) will be necessary. Figure 23 gives several examples (not exhaustive) in which it is assumed that all electricity grids are suitable for two-way traffic. Local storage with batteries in the distribution grid, in the meter cupboard or through the smart charging of electric car batteries. Controlling the electricity used by heat pumps for space heating where heat storage provides the necessary regulating margin for the heat pump. Locally some of the load, for example in cold stores, is geared to the supply (Demand Side Response, DSR). Electricity is stored virtually in either warm water or in frozen products tempo-rarily. Controlling electricity production with cogeneration at horticultural companies, with heat storage providing the necessary regulating margin here too.
Figure 23: New forms of flexibility in the future for the large-scale incorporation of renewable energy sources
Water reservoirs (pumped hydro), such as those in Norway and the Alps, can be used to provide flexibility through international electricity transmission connections (intercon-nectors) (Figure 24). Ideas from the Netherlands, such as an energy island off the coast of Walcheren (PAC) can also contribute to flexibility in the future. There will be a need for flexible traditional power generation units with rapid upward adjustment possibil-ities. Improved accuracy of predictions of electricity from wind and solar sources and aggregation of these predictions from a larger area will reduce the demand on reserve capacity and flexibility.
Each solution has its own characteristics, regulating margin, investment level, develop-ment process, interest/niche and price.
In my opinion it would be extremely difficult to control and manage all of this from a single centralised location. A system based on market mechanisms [Meijden, 2010], [Bosch, 2010] and price incentives would provide more scope and opportunities for solutions. It is good that the market mechanisms being developed facilitate optimal access to both decentralised small and large-scale solutions for the use of short and long-term flexibility functions. The online exchange of information plays an impor-tant role in designing markets. A lot of research from different angles and disciplines (market mechanisms, technology, regulation, economics, behaviour) is needed in order to find a good solution.
It is clear that the electricity system is not yet sufficiently equipped for these long-term developments and that a lot of research is required with regard to system integration, with flexibility being an important design parameter.
Figure 24: TenneT grid connects large-scale energy storage in Norway (hydro), the Alps (hydro) and the Dutch province of Groningen (gas)
System integration
The Department of Electrical Sustainable Energy of the faculty of Electrical Engineering, Mathematics and Computer Science within which my chair is situated has built up a wealth of experience and scientific knowledge in important areas such as system stability, system reliability, grid architecture, development of simulation modules, integration of DC and AC, transient phenomena and protection, system performance monitoring, system control and hardware in the loop real-time simulation.
My personal expertise concerns the influence of new technologies on grid architecture with the large-scale incorporation of local and concentrated forms of renewable energy. This expertise is based on my background in industrial process automation and many years of experience in energy distribution and electricity transmission.
For my chair in Large Scale Sustainable Power Systems the key word is system integration.
The research questions that arise from the future requirements for a reliable and sustainable energy system are diverse and complex.
I consider there to be two important drivers for my chair: – The large-scale integration of renewable energy sources;
– New network technologies and the application of information & communications technology.
I distinguish two focus areas:
– Planning of the electricity transmission system; – Operation of the electricity supply system.
This results in four fields of research (see Figure 25) for system integration.
Figure 25: Research topics relevant to system integration
I will provide a number of examples of research questions. As a result of the limited time of my part-time role, I must confine myself to a small number of research ques-tions. I will therefore specify the PhD work in which I am involved and for which Dr Madeleine Gibescu, Dr José Rueda and Dr Marjan Popov provide the day-to-day supervision.
- In what way do new grid concepts for the large-scale integration of renewable energy sources influence the reliability and stability of the electricity system?
PhD candidate Bart Tuinema: “Reliability Evaluation of Offshore Wind Energy Networks and the Dutch Power System”.
- Which new planning methods and analysis tools contribute to the effective integration of renewable energy sources while maintaining a reliable security of supply?
PhD candidate Ana Ciupuliga: “Transmission Expansion Planning with Large Scale Wind Power Integration”. (Dr since 1 December 2014.)
PhD candidate Shahab Shariat Torbaghan: “Developing a Transnational Electricity Infrastructure Offshore: Design, Operations and Regulatory Solutions”. (Dr since 5 February 2016.)
- What are the possibilities offered by new network technologies and information and communications technology on the planning of sustainable European transmission grids and what is their influence on the performance of the electricity system?
- Which security and control concepts are necessary to reliably integrate the multi- terminal VSC HVDC in the HVAC transmission grid?
PhD candidate Arjen van der Meer: “Offshore VSC-HVDC Networks – and their Influence on Transient Stability of AC Transmission Systems”.
- How can the flexibility and controllability of a transmission system be increased? - In what way can the renewable energy sources themselves be expected to contribute
(with ancillary services) to system performance and system stability?
PhD candidate Jens Bömer: “Stability Analysis of Transmission and Distribution Systems with Distributed Generation”.
- How can network simulations and market simulations be integrated efficiently under cross-border grid congestion conditions?
PhD candidate Ana Ciupuliga: “Round-the-year Security Analysis with Bottleneck Ranking for Interconnected Power Systems with Large-Scale Wind Power”.
- How can new HVDC technologies, intelligent protection and Wide Area Measurement contribute to improved performance (transmission capacity, reliability, grid stability) of the European electricity transmission system?
My commitment is to further expand knowledge on system integration within TU Delft and to help train highly-educated engineers in order to achieve and safeguard a sustain-able and relisustain-able electricity system in the future.
Conclusion
I consider it a privilege to be able to contribute to education and research in the academic setting. I have the unique opportunity to link two worlds, namely science and industry, and this is where I feel I am at my best. As an international electricity trans-mitter, TenneT is involved in current issues such as the integration of large-scale renew-able sources, facilitation of market development, dealing with public acceptance of new connections, facilitating large-scale expansion of fossil generation units on the North Sea coast and responding to the phasing-out of nuclear energy in Germany. My fellow professionals in the Netherlands and Germany are a rich source of inspiration for me, which also benefits the TU Delft community. In addition to the transfer of knowledge from our company within the university, TenneT also continues to learn from students, PhD candidates and scientists.
I would like to thank the Executive Board of TU Delft and the management of the faculty of Electrical Engineering, Mathematics and Computer Science for my appointment and for their confidence in me.
I am very grateful to the Management Board of TenneT for giving me the opportunity to take up this part-time chair. It was TenneT’s CEO Mel Kroon who approached me about this position at the time, and I appreciate the company’s trust and support.
Several of my colleagues at TenneT are willing to take over some of my duties so that I can hold this part-time position alongside my other work. I greatly value the genuine interest in what is happening at this university and the active involvement in research and the supervision of internship students and graduating students.
I would like to thank Prof. Michel Antal for his wise counsel and support.
I am grateful to Prof. Ronnie Belmans for our inspiring discussions and exchanges of views.
I thank my fellow professors at Delft University of Technology and my other colleagues in the Netherlands and abroad for their positive responses to my appointment here in Delft. I look forward to a fruitful collaboration in the future.
I am grateful to my fellow professors Prof. Bram Feirrera, Prof. Lou van der Sluis, Prof. Johan Smit and Prof. Miro Zeman, assistant professors Dr Madeleine Gibescu and Dr Marjan Popov, the staff and secretary’s office within the department of Electrical Sustainable Energy for their practical support during my induction and their pleasant cooperation thus far.
My predecessor Prof. Kling and my – I feel I can now say – colleague, dear Wil. You share your enthusiasm for the field with the students and PhD candidates. I look forward to a good working relationship with you and the members of your capacity group Electrical Energy Systems in Eindhoven.
Finally, I would like to address the students. In my inaugural address I wanted to indi-cate that electricity will become an increasingly important part of our society. A changing energy mix with more renewable energy, integration of the European electricity market, society’s increasing dependence on electricity and that same society’s increasing resistance to visible large infrastructural projects all mean that new uncon-ventional solutions have to be developed in order to respond to the issues of the future. Substantial investments in international electricity infrastructure are expected in the coming decades and there is plenty of interesting work to be done. Ensuring a sustain-able and relisustain-able electricity system is a real challenge for the future generation of engi-neers. Never a dull moment.
I thank you all for your attention. Ik heb gezegd.
References
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February 2011
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- [IPCC 2007] “Climate Change 2007: Synthesis Report, Summary for Policymakers”, An Assessment of the Intergovernmental Panel on Climate Change, approved at IPCC Plenary XXVII, Valencia, Spain, 12-17 November 2007
- [Meadows1975] “De grenzen aan de groei” (“The Limits to Growth”), Club of Rome, Meadows, Dennis / 9th edition, 1975, published by Het Spectrum, ISBN 9027452466
- [Meijden, 2010] M.A.M.M. van der Meijden, I.J. Tigchelaar, FJ.C.M. Spaan, P.G.H Jacobs, “Longterm grid planning in the Netherlands”, CIGRE session, Paris 2010, paper C1-303
- [Shell 2011] ENERGYFUTURE, an initiative of Shell Nederland, 2011
- [Sluis 2011] Lou van der Sluis, “Opgewekt door de Buurt” (“Generated by the Neighbourhood”), TU Delft Library, 2011, ISBN 978-94-6186-009-5
- [TenneT 2008] “Vision2030, TenneT’s long term vision on the 380 kV and 220 kV electricity transmis-sion grid”, report on www.tennet.eu, Arnhem, February 2008
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