GLOBAL ENERGY SUPPLY POTENTIAL OF CONCENTRATING
SOLAR POWER
Christian Breyer1,2 and Gerhard Knies1
E-mail: christian., Phone +49 40 32 507 795, Fax +49 3212 10 10 860
1 DESERTEC Foundation – An Initiative of the Club of Rome, Ferdinandstr. 28-30, D-20095 Hamburg, Germany
2 Q-Cells SE, Sonnenallee 17-21, D-06766 Bitterfeld-Wolfen OT Thalheim, Germany
Abstract
This paper prents the global energy supply potential of concentrating solar thermal power (CSP). Bad on the DLR-ISIS data for global direct normal irradiance, an estimate is derived for global potential CSP areas and their electricity supply potential. Assumptions are included for land u restrictions and land u efficiency. Including data of global distribution of population distances of centers of CSP electricity supply to human electricity demand are estimated. Performance characteristi
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cs of high voltage direct current (HVDC) power transmission is ud for analysing global energy supply potential of CSP. Results are shown for different regions in the world, different distances to potential CSP areas and for electric and non-electric energy needs. The outcome clearly shows that CSP has the potential to become a major source of global energy supply. This supports an important assumption in the DESERTEC concept, which assigns large fraction of power supply to CSP.
Keywords: concentrating solar power, solar thermal electricity generation, solar energy resource asssment, solar energy supply potential, dertec
Introduction
Anthropogenic climate change concerns [1, 2] and ongoing depletion of fossil energy resources [3] created a strong momentum for market diffusion of renewable energy sources and their respective conversion technologies. In order to convert solar energy in energy forms usable for human needs there are veral thermodynamic pathways.[4] In general, heat, kinetic energy, electric energy and chemical energy can be provided via solar energy conversion. Concentrating solar thermal power (CSP) plants convert direct solar irradiance into electricity.[5] Suitable sites for CSP plants are located all around the world. Nevertheless, CSP is still a niche application for today’s global energy s
upply but installations of new CSP plants show high growth rates.[6] On basis of satellite data, potential CSP sites are classified and a worldwide distribution of high quality potential CSP sites is derived. Taking into account population distribution on earth and high voltage direct current (HVDC) power transmission, the global energy supply potential of CSP technology is estimated in the following. In addition to CSP, recent rearch indicates that large scale photovoltaic (PV) power plants in MENA region may lead to comparable electric and economic characteristics referring to conventional CSP plants.[7]
Geographic distribution of direct normal irradiance
Radiation data ud in this work are bad on the DLR-ISIS (Irradiance at the Surface derived form International Satellite Cloud Climatology Project (ISccp) data) of the German Aerospace Center (DLR).[8, 9] The DLR-ISIS data is subdivided into a 280 km x 280 km equal area grid on grid boxes of 72 latitude steps of 2.5°. The ud datat for the direct normal irradiance compris monthly values for 1984 to 2004. The annual 21 year mean value for every grid box is refined on a 1° grid by applying distance weighted mean values of the DLR-ISIS data in order to enable a correlation to the population density.[10]
Solar resource maps for CSP asssment are visualid by direct normal irradiance (DNI) per area and year, normally in units of kWh/m²/y which are suitable to CSP requirements. The unit kWh/m²/y describes the sum
of solar energy irradiated on the area of one square meter in a year. The global distribution of DNI shown in Figure 1 predominantly overlaps with the derts of the world (data for Greenland have to be ignored due to satellite constraints for regions in the far North).
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The largest areas in the world for CSP u are located in North Africa, South Africa, Middle East, India, Australia, North America and South America. Different from most natural resources, solar energy in form of direct normal irradiance is allocated around the world and nearly all populated areas may be connected to the areas of excellent solar conditions.
Figure 1: Global direct normal irradiance. Data are bad on DLR-ISIS [9] of German Aerospace Center (DLR) and are derived from International Satellite Cloud Climatology Project. Areas of at least 2000 kWh/m²/y are needed for CSP plants due to economic constraints.[12]
Geographic distribution of world population
The energy supply potential of CSP can be assd if the geographic distribution of the world population is taken into account. The Center for International Earth Science Information Network (CIESIN) of the Columbia University, New York, makes data available about the global population density. The data chon for the investigation of this work are in the resolution of a 1° grid, suitable to the recalculated radiation data. The datat is now available in the third version, “Gridded Population of the World Version 3” (GPWv3), updated to the year 2000 with a world population of 6.05 billion people.[11] The population density data are depicted in Figure 2.
High and very high population densities shown in Figure 2 are given for India, China, parts of South East Asia, Japan, most parts of Europe, a few parts of North America, the Caribbean and generally for islands. A comparison of the Figures 1 and 2 illustrates, that most of the areas with excellent solar resources exhibit a low population density, for instance in derts like Sahara dert, Namib dert or Western Australia. Global energy supply potential
The global distribution of DNI (Figure 1) is ud to identify potential CSP sites. The solar radiation quality limit of potential sites is t to a direct normal irradiance of at least 2000 kWh/m²/y due to economic constraints.[12] Today’s projects are commercially developed for at least 2000 kWh/m²/y. Nevertheless, future plants may be built in areas of at least 1800 kWh/m²/y, as lower costs for the solar field, would improve profitability. CSP plants at sites with restricted access to water can be operated by using dry air cooling towers which slightly lowers the overall conversion efficiency. The identified coherent potential CSP areas range from a minimum of about 9,000 km² (which was t to the lower limit) to more than 31 million km² (before exclusion of not suitable sites for CSP plants). The regional aggregation of the single sites is
summarid in Table 1.
Figure 2: Global population density for the year 2000. Areas coloured yellow show a high and orange and red a very high population density. The unit for population density is persons/km². Data are provided by Center for International Earth Science Information Network (CIESIN).[11]
Electricity generated in CSP areas can be transported via high voltage direct current (HVDC) power lines over veral thousands of kilometers.[13] HVDC transmission loss can be kept in the range of 3%/1000 km plus HVDC terminal loss of 0.6% per inlet and outlet station. Power transmission over distances up to 3,000 km counts for transmission loss of not more than 10%, whereas high voltage alternating current (HVAC) would cau power loss higher than 20% and investment cost per km significantly higher than HVDC power lines.[13] It should be noted that if generation costs of electricity are low, the increa in transmission cost will not be significant.
Identified potential CSP areas are shown in Figure 3. Regions which might be in reach of respective CSP areas by applying HVDC power lines for electricity transmission are indicated by surrounding areas of multiples of 900 km. Power lines might not be built in the shortest possible distance between centers of demand and supply due to land restrictions, therefore multiples of 900 km are taken instead of 1000 km. The energy supply potential of CSP can be assd if the geographic distribution of the world population is taken into account. Population living clo to CSP areas and within multiples of 900 km is shown in Figure 4 and Table 2. A regional breakdown of CSP supply potential shows that North and South America could be completely supplied within 2,000 km of potential CSP areas and the world region Africa/ Europe/ Asia could power 3.5 billion people via CS
P within 2,000 km. As shown by Figure 4 and Table 2 energy supply potential of CSP technology for the world population living within 3,000 km distance to potential CSP areas exceed 90% of world population.
Power potential for electricity supply is calculated assuming an exclusion of 30% of the area which fulfill the solar quality conditions but not land availability constraints, e.g. natural resorts, slopes, water, shifting sands, human dwellings, roads, agricultural u, etc. In the potential CSP areas it is assumed that the solar radiation potential accounts for a respective power potential by applying a land u efficiency of 10%, i.e. for generating one MWh el/y at a DNI of 2000 kWh/m²/y 5 m² suitable ground is needed.[12] Higher exclusion of area or lower land u efficiency, respectively, would lead to lower power potential of CSP areas. A similar asssment of global potential of CSP prented in this conference shows land u efficiencies ranging
resultbetween 2.5% and 20% but calculates with an average land u efficiency of 4.5% for recently built CSP plants and higher land exclusions.[14] Total global power potential of CSP estimated in this paper and by Trieb et al [14] differs by a factor of four due to a stricter land exclusion and lower assumed land u efficiency. For the general estimate of energy supply potential of CSP technology in this paper a transfer of today’s CSP rearch results to the market is expected in the years and de
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cades to come.
Figure 3: Global potential CSP areas (dark red) with enlarged boundaries within reach of HVDC power lines. Potential CSP areas are shown classified by a direct normal irradiance better than 2,000 kWh/m²/y and larger than 9,000 km².
Figure 4: Energy supply potential of CSP in the world versus distance to CSP sites. Data for world population of 6.05 billion people are for the year 2000.[11]
potential CSP area solar radiation
potential
average DNI
quality
alloy
power
potential
[mio km²] [1000 TWh rad/y] [kWh/m²/y] [1000 TWh el/y]
North America 4.9 11,500 2410 1,150
South America 5.9 13,500 2330 1,350
Africa/Europe/ Asia 32.3 73,500 2600 7,350
Pacific 6.8 23,000 2950 2,300
Total 49.9121,500 12,150
Table 1: Global aggregated potential CSP area, solar radiation potential, average DNI quality and power potential limited to sites of at least 2000 kWh/m²/y DNI. 70% of all identified areas are classified as potential CSP areas. Land u efficiency of 10% is assumed.
potential CSP area
power
potential site 900km 1,800km 2,700km 3,600km 4,500km
[mio km²]
[1000
TWh el/y]
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North America 4.9 1,150 160 400 460 470 470 470 South America 5.9 1,350 160 310 360 370 370 370 Africa/ Europe/ Asia 32.3 7,350 1,610 2,730 3,510 4,400 4,840 5,120 Pacific 6.8 2,300 20 190 260 430 740 1,800 Interction Asia/Pacific 0 0 0 130 520 1,75026个英文字母音标
Total 49.9 12,150 1,950 3,630 4,590 5,540 5,900 6,010 Table 2: Segmentation of world population into world regions and their distance to potential CSP sites. According to figures and tables in this ction 900 km enlargement steps of the potential CSP areas are taken into account. Due to an interction of potential supply areas out of Asia and the Pacific rim the population of the interction area is given.
Contribution potential of CSP to global energy demand
guineapigAccording to Table 1 global aggregated CSP energy supply potential adds up to about 12 million TWh el/y. Annual energy needs for electric and non-electric supply are in the world in total 16,100 TWh el and 76,500 TWh th, which relates to 2.7 MWh el/capita and 12.7 MWh th/capita in the world and 6.7 MWh el/capita and 26.5 MWh th/capita in Europe, respectively, bad on data for the year 2000.[15] Annual growth rate of primary energy demand is expected to be 1.6% p.a.
Bad on the CSP energy supply potential (Table 1) and the energy demand for human needs suppl
y coverage of CSP can be estimated. Several assumptions have to be incorporated. HVDC power lines could interconnect centers of CSP supply and energy demand. Power loss of HVDC power transmission is included and accounts for 3%/1000 km plus HVDC terminal loss of 0.6% per inlet and outlet station. Taking all assumptions into account electricity demand of world population on European consumption level would be approximately 44,000 TWh/y.[10]
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Noteworthy, if all humans lived at European electricity consumption level, 0.4% of the electricity potential of worldwide potential CSP area could supply more than 90% of the world population connectable per grid to derts. In every world region (Table 1) this number stays well below 0.7%, including only sites of a radiation quality of at least 2000 kWh/m²/y in the calculations. It would be possible to supply 6 billion people with nearly threefold the electricity generation of today and using only CSP. Every other renewable energy source, i.e. wind power, hydro-electric power, photovoltaic power, geothermal power and biomass, at sites not ud for CSP generation would even improve access to energy around the world.
