Photovoltaic Solar Energy in Portugal State-Of-The-Art and Perspectives of Development
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PHOTOVOLTAIC SOLAR ENERGY IN PORTUGAL STATE-OF-THE-ART AND PERSPECTIVES OF DEVELOPMENT SUMMARY Global energy supply has become a major issue for the world’s development. Since the industrial revolution (1860), our lives have become increasingly more dependant on the use of energy, and more particularly on electricity. Global warming, together with its increasingly harmful effects, is a direct consequence of this dependency. In this scenario, solutions that could provide a clean, sustainable and unlimited power source are needed. Photovoltaic technology (PV) is among those that show the best potential to provide that so much needed clean energy. The energy source (the sun) is virtually endless: every hour the earth surface receives more energy than humans produce in an entire year. Although its expression in the global energy mix is still very limited, photovoltaics has been growing at a rate of 30% per year, and studies show that in the mid term it can achieve a 30% penetration rate in the global electricity mix. This fact shows the enormous importance that the world photovoltaic industry could have in less than 30 years, and the tremendous business opportunities that lay before those who can position themselves better in the market. This thesis aims at showing that photovoltaics really is a viable option to overcome the new challenges facing worldwide energy production, and that Portugal can and must actively participate in the construction of a strong cluster in the field. Presentation of Photovoltaics: The photovoltaic effect is not new to the scientific community. In fact, it was first observed by Edmond Becquerel in 1839. In 1877, the first photovoltaic device was put in place (0,5% efficiency conversion). Since then, many scientific developments have allowed PV to be an economically and technically viable solution for many applications, from satellites to remote telecommunication systems and pocket calculators. These are called autonomous systems, since they produce electricity for one specific need, with no other input needed. Such systems are composed of photovoltaic cells wired in series or parallel to form modules. Metallic terminals concentrate the electricity produced from the sun radiation converted, and then send it to an inverter, where DC is turned into AC. Batteries can then be placed to ensure the availability of electricity when there is no sun. A charge controller is also required, to ensure that batteries are not overloaded or totally unloaded. The technological scenario for PV is complex: many technological options are under use or development, and they all present similar efficiency/cost ratios. They are also far from technological maturity, and all present very significant cost reduction opportunities. As a consequence, there is a dispersion of efforts in R&D between all the options, as it is still not clear which technologies will have the best characteristics in the future. Present technologies can be divided into three main groups: - Crystalline silicon cells (1st Generation): they dominate the market, with a 90% market share worldwide. The single crystal silicon was the first technology, and still dominates the market. It typically presents efficiencies in the range of 15% to 18%, and is used in all kinds of medium to big terrestrial applications. The multicrystaline (or polycrystalline) silicon is a cheaper but also less performing option, and can be photosensitive in two sides (Power cells); - Thin film cells (2º Generation): responding to the need of reducing silicon consumption, thin film cells are also lighter, allowing new applications in facade buildings. The most important technology is amorphous silicon, used in professional electronics and solar watches or calculators. A 5% to 7% conversion efficiency is compensated by a lower unit cost, and the ability to absorb diffuse lightning. CIS and CdTe are other technological options, but contain dangerous materials like cadmium; - New solar cells concepts (3º Generation): they promise higher efficiencies and lower costs, but are still at an early development stage, and should have a small relevance for the overall market in the next 10 to 15 years. Nanocrystalline technologies belong to this group. The number of applications for autonomous systems is constantly increasing, due to a spectacular reduction in the production costs. As a result, some of those markets are already mature. Nonetheless, their part in the world energy consumption is infinitesimal. The new and bigger challenge facing PV is now related to its use in mass electricity production, in connection to the common electrical grid. Technically, the only difference to the autonomous systems is a connection to the grid, instead of the use of batteries. Economically, the barriers that must be overcome are still high: it is still very expensive to produce photovoltaic electricity, when compared to other mass electricity sources. Nevertheless, it is generally agreed that those same levels of cost can be achieved in the mid term. Perspectives for mass electricity production: A country’s energy production capacity relies on different technologies, each having unique characteristics. The comprehension of the importance of a balanced electricity mix is essential for determining the significance that PV could have in the future. PV produces electricity when the sun shines. It is therefore a variable source, its typical load diagram responding to the peak industrial and commercial demand. Its main competitors are electricity sources that produce for peak loads, which typically present higher generation costs. Wind energy, usually linked to PV, is actually complementary: the high initial investment makes it compulsory that all the electricity produced is sold to the grid. Therefore, wind cannot supply peak demands, but only complement the base needs. With higher than average generation costs, but lower investment costs, gas energy is the most used power source for peak loads. A gas power plant can quickly be switched on and off, and typical plant size is smaller than for fuel or coal. The final target for PV is therefore to present costs that are competitive with gas power. Dams with storage reservoir can also supply peak loads, but the unpredictability of rains in Portugal and their high share in the national electricity mix make it important to use a source with a different pattern of variability. Only having these two main options proves that there is room for a new electric power source, with the characteristics of sun power. A new, more serious and direct competitor to PV is under development: solar thermoelectricity. It produces electricity by concentrating solar light onto a point or axis, where a fluid is heated. The fluid is then used as in a conventional thermoelectric power plant. Although it is still at an early development stage, this option already presents lower costs than PV, in the range of two to three Euros per watt, or even below in big CLFR plants (50 MW). The counterpoints are that it presents a much more limited development and cost reduction potential (most of the technology -turbines- is already mature), higher operation and maintenance costs, and it can not be so efficiently used for microgeneration. Therefore, grid parity is not enough for this technology to be a viable option, and competitiveness with mass production technologies must be targeted. Nevertheless, solar thermoelectric technology can still have a role in the future of electricity generation, and should be further studied. Prevision for IEA Countries – Advanced International Policy Scenario Unit: TWh 2001 2010 2020 2030 2040 Total Consumption IEA 15578 19973 25818 30855 36346 Biomass 180 390 1010 2180 4290 Large Hydro 2590 3095 3590 3965 4165 Small Hydro 110 220 570 1230 2200 Wind 54,5 512 3093 6307 8000 Photovoltaic 2,2 20 276 2570 9113 Solar Thermoelectric 1 5 40 195 790 Geothermal 50 134 318 625 1020 Marine (Waves, Tides) 0,5 1 4 37 230 Total RES 2988,2 4377 8901 17109 29808 Percent RES 19,2 % 21,9 % 34,5 % 55,4 % 82,0 % Source: EREC, 2005 Knowing how mass electricity production works, it can also be understood that PV can only be part of the solution: the security and reliability of electricity supply will always demand several sources, having different characteristics and load patterns. International organizations such as EPIA and IEA are very optimistic though. IEA estimates that its member countries will have an 82% renewable electricity penetration in 2040, with 25% of the total coming from PV. Those numbers imply that PV will reach grid parity before 2020, and that it will be the electricity source with the most remarkable cost reduction. The use of dams with reverse pumping systems associated to big PV installations can be a solution to minimize the impact of the unpredictability of this source. Reducing costs: The study above shows that photovoltaics can have a very significant role in the construction of a new scenario of electricity production. But that will only happen if generation costs can be brought to an economically viable level. That means, in a first stage, reaching grid parity for small system sizes, the stage where photovoltaic electricity costs the same for the domestic producer as the electricity bought to the grid. This already happens in extreme cases, where grid electricity is very expensive (Hawaii), sun conditions are perfect (Sicily), or the market is already very mature (Japan). In most cases however, system costs still have to decrease almost 40%. The second stage will be to reach parity at an industrial level, in competition to the traditional power sources. That will presumably only happen in the medium to long term. Those cost reduction objectives can mainly be achieved by a significant reduction in materials cost, an increase in the cells conversion efficiencies, or an overall cost reduction due to economies of scale in the industry and a mature and competitive market.