INFOSAM 2020

 

POSITION PAPER ON ELECTRIC ENERGY

 

PREPARED BY:

Professor Arne Nysveen (coordinator)

Professor Olav Fosso

Professor Robert Nilssen

Professor Tore Undeland

Assoc. professor Eilif Hugo Hansen

PhD-student Michael Belsvik

 

ABOUT THIS PAPER

This paper presents the results from the working group on “Electrical Energy” within the Infosam-2020 project. The overall aim of this project is to chart the future to the Faculty of Information Technology, Mathematics and Electrical Engineering (IME) the next 15-20 years.

Electrical Energy is a vast technical area, and this paper does not cover all areas in the same depth. The topic Electrical Energy plays an important role in international and national debates on the future energy mix, such as inclusion of renewables instead of using gas fired power plants or use of hot water vs. electricity for heating of buildings. This is very important issues, but in the context of Infosam 2020 we have focused more on power technologies and power delivery systems itself.

INTRODUCTION

The working group has assessed how changes due to new technologies, new demands, new regulations and increased focus on sustainability impacts generation and use of electrical energy.

 

One of the authoritative sources for this paper is the “Electricity Technology Roadmap” made by the Electric Power Research Institute (EPRI). In addition organizations as Conseil International des Grandes Reseaux Electriques (CIGRE) and Institute of Electrical and Electronic Engineers (IEEE) have organized activities on future electricity technology.

 

Distributed (or embedded) generation and storage, smart devices and buildings and advanced regimes for power system operation are aspects that the working group has considered. Advances in computational engineering and material science (e.g. nanotechnology, magnetics and polymers) open new possibilities for design, analysis and operation. New requirements and possibilities given by information technology on electricity generation and consumption are discussed. 

 

THE VALUE OF ELECTRICAL ENERGY

Energy in form of electricity represents the most controllable, precise, convertible and flexible energy source for our modern society. Electrical energy is used to power “everything” from small devices requiring only microwatts to large factories and plants requiring 100 megawatts and more. Power grids cover whole countries and continents and make electrical energy available as a utility service we all take for granted in the western world. Electrical engineering has its basis in electrodynamics, material science and mathematics. Electrical energy provides the “muscle” and energy in automation.

 

Electrical energy possesses some unique features making it highly valuable in modern society:

• Conversion into work with (almost) 100% efficiency. Exergy content is 100%.
• Processing, storage and transmission of information.
• Conversion in to light.
• Electrometallurgy – e.g. production of aluminium.
• Necessary energy carrier in extracting useful energy from renewable sources as hydro, wind and sun.

 

THE POWER SYSTEM IN 2020

Introduction

The political and public debate on electric power is often related to how to provide new power and/or reducing the power consumption. Less attention is paid on how and which values does the electric power create. The emerging information society (or digital society) put new requirements on the power delivery system. By failing to response to this, the underlying productivity growth with reduced power density (ratio of electricity use to gross domestic product) and increased standard of living can be reduced. In the US, EPRI has formed the “Consortium for Electric Infrastructure to Support a Digital Society” – CEIDS to provide science and technology to power a digital economy and to integrate users and markets.

 

In order to satisfy future demands, provide electricity in an environmentally acceptable way and to operate in commercial power markets, several predictions need to be considered:

 

·        More diversification of the power delivery system.

o       Increased use of distributed (embedded) power generation and storage. Wind power, small hydro, micro-turbines, bio and even photovoltanics.

o       Mix of primary energy source for the Scandinavian power market. Hydro, coal, gas, nuclear and new renewables.

o       Traditional vertical utility companies are replaced by independent power producers, energy service providers, transmission and distribution network owners and system operators.

·        The need for premium power. Premium power is a term used for ultra reliable, high quality electric energy service. Requires embedded production and storage facilities.

·        Information system making end customers responsive to real time production costs. System making automatic changes in end consumers power demand. Today prices are only present in the wholesale market.

·        Increased efficiency by more intensive use of (power) electronics to control load. On a global basis, about 50% of all electricity is used by non controlled motors.

·        Advanced tools for planning and operation of the system.

Power production

The future demands for electricity depends on several factors such as technological development, economic growth, social development and political decisions. However, in order to facilitate an economy based on increased productivity with more intensive use of information technology and automation, electricity is needed. In North America, the UN forecast an increase of 1.3% per year the next 50 years. In Norway, mean annual increase in power demand from 1991 to 2000 was 1.5% per year. Gross consumtion including grid losses was about 122 TWh in 2000. Annual production 118 TWh. Towards 2010, NVE expects an increase in power demand of about 14 TWh from the year 2000.

 

The new production can be provided from several sources: Wind, hydro, gas, bio and the sun. Future production mix depends on political decisions, such as tax and regulations, cost and technology advances. Current policy is to provide 3 TWh from wind power in 2010 and to introduce more power from small hydro power plants. Gas fired power plants are under consideration (3 specific projects are approved by the authorities) but no decision on investment has been made. Uncertainties related to gas price, investment cost for pipelines and CO₂ emissions (tax, re-injection) are some of the reasons.

 

While power generation in the beginning was dominated by manually performed control tasks, this has changed a lot over the years. Today hydropower plants runs on remote control. This remote control covers: generation level on each unit, automatic startup and shutdown of units, switching operation and measurement of key values. Remote handling of the power plant also required that condition monitoring of equipment became centralized.

 

One of the big challenges is to make the control and state monitoring systems cheap enough to deal with distributed resources. In the past, few but large units made the information volume easy to handle. With many small units maybe in magnitude 1000:1 compared with the traditional plant size, one faces a tremendous growth in data volume. At the same time the distributed system must work with information highways of lesser reliability than for large power plants, the system must not commonly fail due to shutdown of data channels.

 

On top of this, value measurements needed for accountancy and condition monitoring adds to the data volume. Routines for handling data series with gaps in an acceptable way are a necessity.

 

Advances in power electronics will play a major role in a successful inclusion of distributed generation. Large wind-mill, micro turbines, photovoltaics, full cells and energy storage units all need power electronics for grid connection. This gives rise to new challenges, but does alto open up new possibilities. Reduced cost and increased efficiency of power electronics is necessary.

 

System planning and operation

 

Two major challenges will be dominating the system planning and operation:

 

• The availability of peak capacity
• The expansion of the transmission system

 

The most successful restructuring of the power supply system took place in systems with excess of production capacity at the time of restructuring. Excess of a commodity is a requirement for competition to work. However, many of these countries are now experiencing smaller margins between the peak load and the peak capacity. As it is today the generation must take place simultaneously with the consumption. The physical generation facilities must therefore be present. The peak load has a very short duration and the units covering this load are often expensive to operate. The market prices are not high enough to cover the investment in new production facilities. New generation capacity will in a competitive environment not show up before the prices are high enough and this will be too late.

 

Very little expansion takes place in the transmission system. It is difficult to get permission to build new lines and generally the focus on cost reduction is very strong. Only smaller expansions are done in order to enhance the use of the existing system that will imply smaller margins.

 

Operating closer to the limits will be a major challenge to the system planning and operation. Smaller margins call for better information and the time to react will be shorter. Competition between the different actors in the power market will reduce the information available that could support the system planning and operation.

 

The transmission systems have become more meshed and interconnections that mainly were built for reliability purposes are now used for heavy power transfer.  The result is that significantly larger systems must be analysed to evaluate the impact within own system. The long-distance power exchange will increase the need for coordination between the system operators. In the large disturbance in USA 2003, a major problem showed up to be lack of coordination.

 

The power production sources will in the future be a mix with different characteristics. Some of the renewable resources may have lower availability that traditional sources, but will still be an important contribution to the total production capability. An example will be large wind parks where integration within the existing system is challenging.

 

The flexibility of the demand side will in the future be very important for power balance. Reducing peak load is better than investing in units for providing peak capacity.

 

The future system planning and operation will have to deal with many different sources and with different characteristics to provide balance between supply and demand as well as smaller margins in the transmission system operation. Advanced sensors and monitoring techniques will make the system “smart”, enabling better real time estimation of the state of the system and to continuously update contingency plans. Online analysis and control will become a critical element for a safe future operation of the system. Real time access of data and the capability to analyse and interpret the results in due time in order to counteract in case of disturbances are mandatory.

 

Power Transmission

 

After restructuring of, transmission is still defined as a monopoly and separated from the sectors with competition. The situation has introduced several challenges for the transmission system operation. The need for transmission capacity has been steadily increasing after the liberalization started. Power exchange over long distances is quite common and the power flow in the system may show paths that the system was not built for. These challenges arise in a situation with decreasing investments in new transmission facilities and with a significant reduction in expenditures on maintenance.

 

A major motivation for the restructuring has been cost reduction, and the transmission system operators are forced to reduce the operation costs and also to justify the maximum transfer capacity on important transmission corridors in the system. It is also very difficult and time-consuming to get permission to build new transmission lines.  Operating closer to physical limits is the main topic.

 

There are different phenomena limiting the transfer capability. The thermal limits of the individual circuits define the maximum flow on the line. However, the stability of the system is often more limiting for the maximum transfer. Stability is associated with the dynamic behaviour of the system. The system must also be operated with certain margins in case of unexpected disturbances.

 

Power electronic equipment (e.g. FACTS) is now introduced in the system with the purpose to better utilize the existing transmission infrastructure and to improve flexibility of the system operation. Some of these components address the power flow distribution while others address the dynamics. Increasing capacity and lower price will cause these to be widely used. A major challenge will then be coordination between all the dynamic elements in the system where the collecting and interpretation of real-time information will be crucial.

 

The data network becomes very important for a secure operation of the power transmission system. Both the protection system and the decision support tools need reliable data. However, disturbances in the power system will often cause problems in the data network. Other infrastructures are also dependent of the power transmission. Degradation of the system’s present performance can therefore be extremely expensive. Widespread disturbances as observed in 2003 are very expensive for the society and will easily in short time exceed the amount saved by restructuring and competition.

 

Improved cables and superconducting devices are likely to be widely used in the future power transmission systems. These will permit higher transfer capacity.

 

Distributed generation will also be an important contribution for the future power transmission system. Local generation close to the consumer will reduce the transfer requirements while penetration of large wind farms will introduce other challenges. A breakthrough on storage technology will become very important for the utilization of distributed and renewable generation.

Power distribution system

Medium voltage systems

The distribution system operates on the medium voltage level (6 kV – 36 kV) where 12kV and 24 kV are dominant in Norway. In power distribution, power flow direction is unidirectional, from the transmission network to end-consumers connected to the low voltage level. Some industry users connect directly to the medium voltage level. In future to accommodate the needs for increased reliability, quality, service and customization, distributed resources are foreseen. This will alter the power flow in the distribution system. New means of protection, power management/planning and new hardware are needed.

 

In Norway, with no gas distribution system, distributed resources near load centres are most likely introduced for premium power purposes, i.e. to provide a secure supply in case of disturbances in the main grid. New concepts such as islanding of self-sustained micro grids will be introduced for customers with high power quality requirements.

 

Today’s medium voltage system is operated as a radial network with very simple power flow patters. In order to increase reliability, outage time and load ability more meshed topologies will be present. This calls for new devices to handle fault situations. New devices based on power electronics combined with advanced protection system can respond to abnormal situations in less than one millisecond. Today’s mechanical systems typically need 30-50 milliseconds to act. Large industry stakeholders as ABB and Siemens have already demonstrated some concepts on this route. Outage times can be reduced from typically one hour to some milliseconds. Power electronics are also foreseen to be introduced for inclusion of distributed generation, power flow control and power conditioning. Generally, power electronics will move from being more or less absent in medium voltage, to play a dominant role in some specific networks.

 

 

POWER APPARATUS AND DEVICES – TECHNOLOGY ADVANCES

Power electronics

 

At NTNU the possibilities opened with power electronics were identified early, just when the technology was introduced. A Licentiate disputation on induction motor drives with invertergrade thyristors took place  in 1966, only 7 years after the (standard type) thyristor was invented by General Electric in the USA.

 

The power electronics technology spread fast in Norway to a large number of production industries. With help from NFR, Norway is still a leading country in power electronics, especially in telecom represented by the two companies Power-One and Eltek. In railway applications, locomotives got inverters for speed control of the induction traction motor (Flytoget, Signatur and Agenda all have this technology and all make use of the Undeland-snubber for voltage and current stress relief during switching).

 

Power electronics can help the transmission capacity and the quality of power. This means that the increasing demand of electrical power can be supplied without building new lines. Also electric power by cables to Denmark, Germany, Netherlands, UK and offshore platforms is only possible with power electronics using the HVDC technology.

 

New power semiconductors

In early 1970’s the different types of power transistors as the BJT, the MOSFET and the IGBT started to replace the thyristor. The cost went down, and new markets opened up like inverters that have revolutionised heat pumps in the resent years.

 

Digital control

Until early 1990’s analogue technologies were used in the control due to the high speed demands. Now DSPs and FGPAs are used all over, even for Pulse Width Modulation and the fast inner current loop. Today we can not imagine control of machines in applications from wind energy to wheelchairs without utilising the digital hardware and software.

 

Innovative ideas for new applications and new markets

The new power components and user-friendly digital control make prototype development quite easy. Thus establishing new spin off companies where power electronics is a part of the product is not so costly and time consuming as before.

 

Electric machinery

Introduction

Electrical machinery is used both as generators of electrical power and motors where electrical energy is converted into mechanical energy. In OECD countries, motors consumes about 60% of all electrical power. Norwegian industry has traditionally been a manufacturer of large generators for hydro power generation. Lately the focus of Norwegian industry has been on advanced motor drives in traditional industry, shipping and offshore applications.

 

Improved performance of induction machines

The induction machine is the industry standard, used in most fixed speed applications. Due to relatively low overall cost and no need for power electronics control in fix speed application, this machine will still be one of the volume products in the future. The research on induction machines focus on energy efficiency, and is not performed in Norway.

 

Increased use of advanced variable speed motor drives

The flexibility and performance of power electronics has revolutionized electrical motor drives. Variable speed and high quality torque control is now available at acceptable cost for industry applications. A large number of process applications utilize these new motor drives to make new energy efficient industry plants. Similarly are a lot of large modern electric drives used in ship propulsion and compressor and pump offshore applications.

Research on modern motor drives including power electronics and advanced control systems is to be continued into 2020. Reduction in cost and simplification in installation/programming causes a penetration of motor drives in the constant speed market of today.

 

New Permanent Magnet materials are used in new electrical machine concepts.

The new low cost materials with exceptional performance have resulted in an international research on new machine concepts. The application of transversal flux and axial flux machines have demonstrated that compact machines with very high efficiency can be manufactured at a compatible cost. The possibility for cost effective fabrication of tailor made machines due to new materials and fabrication methods, opens up the arena for new stakeholders than high volume machine manufactures. Access to a large capital base and large production facilities becomes less important in these new markets.

 

Our research in the coming years will focus on the new machines concepts. In close connection with advanced users, special purpose machines such as wind generators, ship propulsion motors and actuators will be designed.

 

 

Breakers and switchgear

In the next 15-20 years, most new developments are foreseen for medium voltage and low voltage systems, due to introduction of power electronics and new insulation systems. For high voltage, the voltage and power rating are still too high for power electronics to be competitive. However, due to a general wish of less visibility, more use of compact GIS-systems can be foreseen, especially in city centres.

 

For medium voltage systems, several new developments are foreseen:

·        Power electronics for connection of distributed resources

·        Breakers using power electronic devices for fast and precise operation.

·        Ultra compact switchgear that can be buried in the streets (no visibility)

·        New, low cost solid insulation systems (thermoplastics)

·        Automation and communication system for remote metering, power flow control and operation of distributed resources.

 

Cables

The dominant insulation material of today is cross-linked polyethylene (XLPE). In order to increase the power capacity and size, higher field stresses and operating temperature are needed. Maximum field strength in normal service is 20 kV/mm (peak value). Theoretical breakdown strength is about 1000 kV/mm. Improvement in manufacturing and new material additives are needed to come closer to this theoretical value. XLPE cables for DC systems are available today. In 2020, cables for DC will be a mature product. Use of nanotechnology to make specialised materials of will be introduced. Prototypes for outdoor high voltage insulators have already been presented.

For city centres with a very high power load density, superconducting cables offer the possibility of supplying a high amount of power in existing cable ducts. Nexans AS in Norway has already received an order for a superconducting cable to be delivered to New York City. Development of new low cost insulation for low temperatures and cryostat will speed up the use of superconducting cables.

 

SPECIAL APPLICATIONS WITH HIGH NATIONAL IMPORTANCE

This section describes some applications/sectors which are not a part of traditional power supply industry but plays an important role in our national power industry.

Offshore and ship power systems

Norway delivers about 10% of all electrical power equipment and systems to commercial ships.

The flexibility in design of cruise liners, ferries, supply ships and fishing trawlers is a driver to use electric propulsion. New innovate electric machine design and system integration will advance the propulsion and manoeuvring of these types of ships. For cruise liners and ferries, comfort and manoeuvreability is essential.

 

The offshore oil industry sets very challenging requirements to the power industry. Today’s platforms are large industrial sites with advanced power systems. In order to recover oil from mature reservoirs, smaller and complex reservoirs and reservoirs at deeper water, electric power is needed at the sea bed.

·        Subsea processing plants with power requirement above 100 MW

·        Voltage levels of 132 kV for power supply from land or remote platforms

·        Subsea frequency converters with power rating of 50 MW at 1000 meters water depth.

·        Reliable power delivery systems with transformers, switchgear and cables.

·        Electric actuators, motors and power electronic converters to operate complex subsea processing units.

Power supply for telecommunication

11 % of the electric energy in industrialised countries are used to supply the infrastructure for computers and communication. It is no doubt that the number of short outages able to disturb computers increase. Even worse, long lasting blackouts are experienced more now than before. In the power supply industry, this is discussed a lot. We are invited to plan a large research project in DC distribution in houses and office buildings. DC will make standby power with a much higher reliability than the present day ac supply. In areas like California and Ireland the high tech industry declares they will move if the power supply is not reliable enough.

 

National partners

SINTEF Energy Research (former EFI) has since its foundation in 1953 been a major partner for research on electrical energy. The shift from “electricity research” to “energy research” reflects the broadening also in our research in this field. Within the fields of power systems and high voltage engineering the co-operation is comprehensive and integrated.

 

SINTEF MARINTEK is a recognized world class institution within its field. Co-operation on electric systems on ships, e.g. the NFR founded project “All-Electric Ship”.

 

NFR (Norwegian Research Foundation) supports long and short term research within our technical field. NFR has newly launched the RENERGI program.

 

Statkraft and Statnett. Statkraft is Europe’s second largest hydropower producer. Statkraft has also ambitious plans for wind power. Statnett is owner of the transmission grid and power system operator.

 

Nexans AS (former STK) is one of the worlds leading manufacturers of high voltage cables. The research on insulation materials has been a continuous activity for almost 40 years. Materials for superconductors and for higher temperatures are new topics.

 

PowerOne (former Powec) and Eltek are major manufacturers of power supplies for telecommunication on a global basis. PowerOne is a direct result of R&D at our department in 1960s and 1970s on power electronics.

 

ABB, Siemens and Aker. These are manufacturers and suppliers of electrical equipment and systems in Norway. For some products these companies have production facilities and engineering departments in Norway with world marked responsibility.

 

Oil companies (Statoil, Hydro). Development of new technology for power supply to sub sea production facilities.

 

 

 

References

[1]               Electric Power Research Institute (EPRI), “Electricity Technology Roadmap. 1999 Summary and Synthesis”, Doc. no., C1-112677-V1, July, 1999.

[2]               Electric Power Research Institute (EPRI), “Electricity Technology Roadmap: 2003 Summary and Synthesis”, Doc. no., 1009321, November, 2003.

[3]               A. Grübler et. al., “Dynamics of energy technologies and global change”, Energy Policy, pp. 247-280, vol. 27, 1999.

[4]               K. E. Yeager, “Electricity for 21^st century: digital electricity for a digital economy”, Technology in Society, article in press, 2004.

[5]               C. W. Gellings and R. J. Lordan, “The Power Delivery System of the Future”, The Electricity Journal, pp. 70-80, no. 1, vol. 17, 2004.

[6]               J. S. Graves and John D. Clapp, “The Future of Electric Transmission”, The Electricity Journal, pp. 11-21, no. 12, vol. 14, 2001.

[7]               J. D. Kueck and B. J. Kirby, “The Distribution System of the Future”, The Electricity Journal, pp. 78-86, no. 5, vol. 16, 2003.

[8]               V. S. Budhrija, “The Future Electricity Business”, The Electricity Journal, pp. 54-90, no. 9, vol. 12, 1999.