Enabled by High Power Electronics - Energy efficiency ... - IEEE Xplore

4 downloads 6882 Views 763KB Size Report
support the major trends in energy efficiency, renewables integration and smart grid. High power electronics will continue to innovate itself due to the substantial.
The 2010 International Power Electronics Conference

Enabled by High Power Electronics - Energy efficiency, Renewables and Smart Grids P. K. Steimer, Fellow IEEE ABB Ltd., Power Electronics and MV Drives, 5300 Turgi, Switzerland

Abstract-- The global demand for electrical energy is growing continuously, at double the growth rate of primary energy consumption. A clear transition to more electric energy systems is mandatory as energy efficiency from primary fuel to the enduser and the integration of renewables are the future key challenges. This transition to more electrical energy systems requires the transformation of today’s electric power system to a smarter future grid. High power electronics is the key technology to build the next generation of the more electrical energy systems to support the major trends in energy efficiency, renewables integration and smart grid. High power electronics will continue to innovate itself due to the substantial improvement of conventional silicon devices and their packaging technologies reaching higher junction temperature and voltage levels. New wide band-gap material with substantial application benefit will enter niche markets. Multiple new multi-level topologies will change high power electronics fundamentally to support energy efficiency and the direct connection of standard power equipment. Energy efficiency is the most important topic: A real step change in regards of efficient use of primary energy is needed. Energy efficiency requires focus on efficient electrical power generation including mandatory use of waste heat, hybrid and pure electrical transportation and increased industrial process efficiency. We need to create an energy-efficient culture - from primary energy to end user supported by global regulations. As energy as such will increase in value, efficient use will get attractive. The fast transition to more renewables energy sources is the other important topic. The energy of fifty hours of sunshine hitting the earth is equivalent to the energy stored in coal reserves globally. Therefore the future dominant role of the most important renewables, i.e. solar and wind, is actually unquestionable. The question mark lies on the speed of the transition. Especially solar power, as simple technology in the application, will develop much faster than expected. Its speed in the last years has always exceeded expectations. The same is valid for wind power since more than a decade. Again this important change needs to be supported by strong global regulations to achieve speed and competitiveness in the market place in this transition phase. And last but not least: To harvest all the investments done in our AC grids, the transition to a smarter grid is mandatory. Such a smart grid will be based on two key ingredients: Intelligence and High power electronics. Intelligence will allow a better utilization of existing assets and will increase the stability margin of the conventional AC grid. High power electronics will mainly add new DC grids and AC Var sources at the transmission and distribution level, serving as backbones and additional stability pillars to existing AC grids. Index Terms— Energy efficiency, high power electronics, multi-level converters, renewables

978-1-4244-5393-1/10/$26.00 ©2010 IEEE

I. INTRODUCTION The global demand for electrical energy is growing continuously. A clear transition to more electric continues as energy efficiency and renewables are of growing importance. For 2030 the installed electrical power generation capacity will grow by 100%, whereas the worldwide primary energy demand will grow respectively by 55% only (see [1]). High power electronics is the key technology to radically transform today’s electric power system to a much smarter future grid. Such a grid will be able to control higher power flows, increase the existing infrastructure utilization and allow the integration of a fast growing amount of less predictable renewables. New DC grids will be added as transmission and distribution backbones to existing AC grids. II. MAYOR TRENDS FOR FUTURE HIGH POWER ELECTRICAL ENERGY SYSTEMS A. High power electronics High power electronics is the key technology to build the next generation of the electrical power system. New wide band-gap material with substantial application benefit will need some time to enter the high power markets. The substantial improvement of conventional silicon (Si) devices with junction temperature reaching levels of 150°C to 200°C and voltage levels up to 10 kV will first impact high power electronics. Si

[kV]

SiC unipolar

20

10

10 kV 20 kHz

10 kV

2

1 5

SiC bipolar

Mature technology 1

5

20

[kHz]

Figure 1. Trends in high power semiconductors

Multiple new multi-level topologies will change high power electronics fundamentally. Basic passive filtering equipment will be reduced substantially and standard power equipment can be connected. An example of future

11

The 2010 International Power Electronics Conference

possibilities is shown for the example of a 5-level inverter.

Huge differences with regards to energy efficiency exist in the electric power generation. Newest combined cycle power plants are capable reaching of efficiency levels above 60%. The use of the remaining process heat can further boost the overall efficiency above 80%. In transmission and distribution the change to higher voltages, preferably DC, will allow a much more efficient transmission and distribution and allow the transportation of more electrical energy or over larger distances. On the demand side the application of power electronics to control the speed, especially in pump and fan applications, has a huge energy saving potential. For fossil fuel based transportation systems, substantial energy savings can be achieved by means of hybrid system based on power electronics.

TABLE I. FUTURE MULTI-LEVEL TOPOLOGIES

Topology 2-level NPC / ANPC

Silicon Level C (excl. Cdc) 100% 2 100 / 3 150% ANPC5L 150% 5 1 M2LC5L 200% 5 8 Gen. structure 250% 5 6 Note: N° of C with Ud/4 voltage rating, excl. Cdc

C. Integration of Renewables Hydro power contributes today globally about 15% to the total electrical power generation. The integration of distant new large hydro power stations needs to be solved. Additionally in 2030 worldwide 10 to 20% of the electrical power will be generated by windpower. Other renewables, most important solar power, will further increase the share of renewables. This will require transmission backbones, which can support the needed wide-area power exchanges.

Figure 2. Five-Level Active Neutral Point Clamped Inverter (ANPC5L)

Figure 3. Five-Level Modular Multi-Level Inverter (M2LC5L)

Depending on the application the optimum multi-level solution is selected depending on required costs level, efficiency and harmonic performance. B. Energy efficiency Increasing energy efficiency has a potential to save 20% of the primary energy. Energy efficiency needs to be understood with regards to the total chain from electrical power generation over transmission and distribution down to the end-users.

Figure 5. A vision of future integration needs of renewable energies for Europe

It can be assumed, that in 2030 up to 15 to 30% of the generated electrical power will come from renewables sources. This will not resolve the dependency from fossil or nuclear fuels, as in the same time the needed electrical power has grown to more than 200% of the initial value in the year 2007. After 2030 the change to more renewables and more electric will continue and accelerate until the end of the century.

Power Electronics is a cross-cutting technology that allows saving energy across all steps of converting primary energy into goods and life quality Useful energy

primary primary energy energy (e.g. coal, transport oil, gas, hydro, wind)

electrical conversion efficiency

line losses

production processes

equipment efficiency

Figure 4. Energy Efficiency from primary energy to end user

12

D. The Smart grid The overall grid stability will be further challenged with the higher power flows and the growing integration of intermittent renewables. The secure supply of future Mega Cities is an additional technical challenge, as huge amounts of electrical energy need to be supplied with strong space limitations.

The 2010 International Power Electronics Conference -

Carbon capture and storage (CCS) solutions is another future option (see [6]). - Utilization of nuclear energy With regards to the overall energy efficiency it is mandatory to utilize the remaining low-temperature heat for heating or industrial processes. Additionally the efficiency of auxiliaries may be improved by means of variable speed drives (for pumps and fans).

High power electronics will change fundamentally the electrical power systems in the next few decades. To manage the clear demands for increased electrical power transportation, integration of renewables and optimized utilization of the existing infrastructures a strong growth of high power electronics applications in this field is mandatory. The intelligent co-existence of intelligent AC grids and new DC grids will allow solving these issues. Due to their inherent advantage with regards to power flow control, grid stability and infrastructure utilization DC grids are the future choice for new grid infrastructure projects from medium voltage to ultra-high voltage levels.

Over all industrial processes the application of power electronics to pumps and fans has the biggest energy saving impact. It is in that respect important to know, that the motor driving pumps and fans are in at least 30% of the applications oversized due to the uncertainty with regards to flow and pressure sizing. The overall global energy saving is huge as can be seen in Table IV.

ENERGY EFFICIENCY

With regards to energy efficiency it is important to look along the whole value chain, i.e. over the following power conversion steps: - Primary energy transport - Electrical energy conversion efficiency - Transmission and distribution losses - Production processes - Equipment efficiency With regards to the efficient use of the primary energy, which is dominantly fossil fuel based today, each power conversion step needs to be as high efficient as possible (creating as low losses as possible). The different steps should be looked at in detail.

12'000

8'000

10% extra flow 10% extra pressure

1 80

60

0

40

0

A. Primary energy transport The energy transport is often requesting a compressor stage either to compress the natural gas for the transport by sea or for the transport by means of a dedicated pipeline. If a conventional approach of a gas turbine driven compressor is chosen an overall efficiency of only 25% can be achieved [5]. In the case that the electrical variable speed driven compressor solution is chosen an overall efficiency of more than 36% can be achieved. In that case it is important, that the electric power is generated by means of an efficient state-of-the-art bulk power generation station.

2 160

2'000

140

3

4'000

4

120

6'000

100

Pressure

10'000

20

III.

C. Industrial processes With regards to industrial processes and related energy efficiency again power electronics can make a considerable contribution ([7]).

Flow

Figure 6. Figure 3: Design of typical pump or fan application with reserves in flow in pressure resulting in 50% oversized motor. TABLE II. YEARLY SAVINGS IN PUMP AND FAN APPLICATIONS

Saving of Medium Voltage Drives - Only 4% are variable speed today

B. Conventional electrical energy generation It is preferable to for generation of electrical energy based on fossil fuel to select the bulk power generation option. Gas turbine based power generation in the 100 MW class and above can achieve a primary to electrical energy conversion efficiency of - of 47% in a typical arrangement - up to 55% and higher in a combined cycle plant and - of more than 80% in triple cycle (for example for district heating or water desalination plant) Further improvement with regards to C02 emissions can be achieved by - changeover from coal to natural gas, which has inherently lower C02 emissions

Yearly Savings 227 TWh

- 30% of pumps / fans converted to VSD Saving of Low Voltage Drives - 10 x the installed power of MV motors

1655 TWh

- Already 30% are variable speed today - 30% of pumps / fans converted to VSD Total savings of Variable Speed Drives

1882 TWh

To put this energy saving into a context, we can say that it would correspond to more than 22 Itaipu Hydro power stations (equivalent to 275 GW of installed capacity with its average asset utilization degree of 75%).

13

The 2010 International Power Electronics Conference TABLE III. PREDICTION OF WINDPOWER FOR 2017 AND 2030

D. Transportation For fossil fuel based transportation systems, i.e. cars, buses, trains, airplanes and ships again the application of power electronics can substantially increase the energy efficiency due to - higher efficient variable speed power generation - energy savings for acceleration and deceleration by means of energy storage. In this approach the DC-linked based power system is the ultimate approach for the highest efficiency. Based on this concept the following improvements can be achieved: - 20-30% improvements on the fossil fuel energy engine - 20-30% improvements due to the hybrid system with energy storage. Overall energy savings for example for fossil-fuel based engines in the range of 30 to 50% can be achieved by means of power electronics in combination with energy storage [8]. The hybrid system will be an intermediate step to the full electrical vehicle, where a further substantial energy efficiency improvement is possible due to the much higher efficiency of bulk power electrical generation.

Yearly growth rate Average asset utilization Added capacity Added produced energy Contribution of windpower in total production

Windpower 2017 2030 20% …10% 25% 114 GW 250 TWh (32%) 6%

390 GW 850 TWh (67%) 21%

Total 2017

2030 3.3% 50%

180 GW 790 TWh (100%) 100%

290 GW 1270 TWh (100%) 100%

An added capacity of multiple 100 GW per year needs a corresponding amount of power electronics converters and a substantial improvement of the AC grid infrastructure, strengthened with high power DC links.

High wind areas

Figure 8. Grid extensions to achieve the 20% windpower contribution in the US by 2030 ([7])

Example of power electronics in this field are - converter for windturbines (DFIG or PMG used as electrical machines) - hydro-pump storage applications - HVDC transmission of distant renewable energy sources, i.e. offshore wind

Figure 7. DC-link based power system

IV. INTEGRATION OF RENEWABLES A. Windpower, an important future contribution The most important options for the future are the renewable energies to generate clean electrical power. Especially the utilization of wind power has proven to be already a mature and a global option. In 207 the contribution in newly added electrical energy capacity by windpower per year has already reached 8% in 2007, whereas worldwide the contribution with regards to the total electrical power generation by windpower is at only 1%. With a realistic growth rate of 20% per year for the windpower business the values shown in Table II will be achieved in 2017 [9] and may be predicted with a considerable uncertainity for 2030.

B. Solar power, a simple technology in the application With regards to solar power it is interesting to discuss the area of needed land. In that respect it is interesting to have a look at one of the largest hydro power generation plants, i.e Itaipu in Brazil. The installed power is 12.6 GW, with an utilization factor of 72%. This delivers appr. 80 TWh per year. The needed land is appr. an area of 1400 km2, which is covered by water behind the large dam. If we would use the same area of land, i.e. 1400 km2 for solar power in southern Europe, where we have an average solar irradiation of 5kWh/m2 per day we would achieve a nearly 6 times higher value of 500 TWh (assuming solar cells with an efficiency of 20%). It is clear, that solar power is a strong future option. The electricity may be either generated by photovoltaic cells or by solar thermal power plants. In 2007 appr. 3 GW of solar power plants have been added and the typical

In general it can be expected, that the investment in windpower generation plants will continue to grow considerably and that by 2030 worldwide at least 20% of the power is generated by windpower.

14

The 2010 International Power Electronics Conference

to get electrical, wherever possible with the first option for trains. It is quite clear, that a major shift to renewables as sources of future electrical energy will happen. Renewables (Wind, Solar, ..) are important future contributors and solar power (photovoltaic or thermal) needs to be taken very serious. It may develop much faster than expected. At the end it is a simple technology in the application.

annual growth rate of 50% will change the picture fast [11]. TABLE IV. PREDICTION OF SOLAR POWER FOR 2017 AND 2030

Yearly growth rate Average asset utilization Added capacity Added produced energy Contribution of windpower in total production

Solar 2017 2030 50%…20% 20% 130 GW 228 TWh (29%) 2%

500 GW 1050 TWh (80%) 20%

Total 2017

2030 3.3% 50%

180 GW 790 TWh (100%) 100%

VI.

290 GW 1270 TWh (100%) 100%

In 2030 the contribution of solar power will get closer to windpower and from then onwards it will start to be the dominant future electrical energy power source.

3000 km

Figure 6: Solar energy supply in the long-term ([9]).

REFERENCES

[1]

WEA outlook 2007 by International Energy Agency

[2]

Active Neutral-Point-Clamped Multilevel Converters, Barbosa, P.; Steimer, P.; Meysenc, L.; Winkelnkemper, M.; Steinke, J.; Celanovic, N.; PESC '05.

[3]

Modulares Stromrichterkonzept für Netzkupplungsanwendungen bei hohen Spannungen, Rainer Marquardt, Anton Lesnicar, Jürgen Hildinger, ETG 2002

[4]

A generalized multilevel inverter topology with self voltage balancing, F. Z. Peng, Industry Applications, IEEE Transactions on, vol. 37, no. 2,, Mar/Apr 2001.

[5]

All electric LNG plants, ABB Ltd. , Document Nr. 3BHT 490 537 R001

[6]

Shell Szenarieon, Ralph Stalder, Energietrialog Schweiz, Juni 2007, http://www.zerogen.com.au/

[7]

Impact of motordrives on energy efficiency, Peter Barbosa, Christoph Haederli, Per Wikstroem, ABB Switzerland, Switzerland, Matti Kauhanen, Jukka Tolvanen, Akseli Savolainen, ABB Oy, Finland, PCIM Europe 07

[8]

B. Destraz, Assistence energetique pour un vehicule a base the stockage supercapacitif, EPFL report, 2003

[9]

BTM Consult ApS, World Market Update 2007 and Forecast 2008-2012, March 2008

[10] AEP Interstate Transmission Vision for Wind Integration

As transportation of the solar energy in electrical energy form has the highest efficiency (better than 90% over 3000 km), long distance UHVDC transmission lines over very long distances will be added to our future electrical grid systems. To cover all the needed energy of the world we would need just 380’0000 km2 of land, which is less than 4% of the area of the USA. To cover all the energy of Europe we would need just 25’000 km2 or 0.3% of the area of the desert Sahara.

[11] 2000-2003 Strategies Unlimited, EPIA “solar generation” 2006, 2010 Rogol, LBBW Report 2007 [12] Clean Power from Deserts for the World, G. Knies, DESERTEC, EMPA 08

V. CONCLUSIONS With regards to energy efficiency we need to focus on efficient bulk power generation including the mandatory use of waste heat for district heating or process industries. Variable speed drives have to replace overall inefficient industrial gas turbines drivers. Another 30% of pump and fan applications need to be converted to variable speed drives to get an average of 40% energy saving in these applications. With regards to transportation up to 30-50% fuel / energy consumption reduction can be achieved with the DC-link based power system to enable efficient hybrid and in the longer term pure electrical solutions in transportation (cars, buses, trains,..). Transportation needs

15