ROLE OF TECHNOLOGY IN INDUSTRIALIZATION OF PHOTOVOLTAIC

Transcription

1 ROLE OF TECHNOLOGY IN INDUSTRIALIZATION OF PHOTOVOLTAIC Ravi Khanna, CEO, Moser Baer Photovoltaic Limited, India INTRODUCTION Richard E. Smalley, Professor of Physics and Chemistry at Rice University and recipient of Nobel Prize in 1996 for the discovery of Buckministerfullerene (C60), at the 2004 Materials Research Society Fall Meeting in Boston mentioned ENERGY as the top-most problem human race has to confront in this century. Water, food, environment, poverty, terrorism, disease, education, democracy, population being the other global concerns, in the order of priority, to be tackled. Energy plays a key role in solving the other problems mentioned here. The conventional sources of energy, namely, oil, gas, coal and uranium are limited. As per an estimate, the oil, gas, coal and uranium would last for 50, 65, 250 and 60 years, respectively. Concomitant with dwindling fossil fuel resources, the percentage of carbon dioxide in the atmosphere has been rising. For instance, the carbon dioxide concentration in atmosphere has gone up from 280 ppm in the year 1900 to 380 ppm in the current millennium. Rising level of carbon dioxide has impending risk of bringing about ecological changes. This problem is only going to get worse with the increasing world population. It is expected that the world population will stabilize around 10 billion by The developed countries have per capita annual electricity consumption in the range of kwh, whereas for developing countries the consumption is in the range of kwh. In the road to prosperity the developing countries are likely to follow the consumption pattern of developed countries and hence the demand of energy is likely to grow significantly. As per one estimate the current energy demand of the world is 13 Tera Watt-year (I Tera Watt = 1012 Watt). This is expected to grow to TW by 2050 and TW by Since fossil fuels alone may not be able to meet the entire requirement, renewable sources of energy are likely to play a crucial role. Wind, biofuel, hydro, geothermal, solar electric and solar thermal are the main sources of renewable energy. Wind power is approaching competitiveness with the conventional power. The total potential of wind energy is 50 TW. However, total wind energy potential that can be tapped is reported to be in the range of 2-4 tera Watt. The gross theoretical potential of Hydroelectric is 4.6 TW, but environment feasible potential is mere 0.9 TW. The other alternatives are Geothermal and Biomass but each of them suffer from some limitations. For example, geothermal wells have relatively short life and large land area is required for biomass energy. Compared to the above mentioned alternatives Photovoltaic provides immense opportunity. Even though the theoretical potential is huge at 1.2x 105 TW, practical on shore potential is 60 TW at 10% average conversion efficiency. In 2006, 1500 clean tech companies opened and more than 4000 US patents were filed on clean technologies with solar and bio-fuels leading. Interest in solar energy is due to its abundant availability and distributed nature. The only impediment in the large-scale popularization is its present high (25-40 US Cents/unit) energy cost. The energy cost of renewable options is compared with fossil fuels in fig.1. The high- energy cost is owing to high capital cost and low conversion efficiencies. Solar cells, the basic energy conversion unit, typically have an efficiency of 15-16%. The installed cost of Photovoltaic is presently USD per kilo Watt. To compare it with other energy sources the cost of combined cycle gas turbine is USD/kW, coal based plant is USD/kW and on-shore wind installation is USD/kW. GLOBAL MARKET The total sales revenue of photovoltaic products was 15 billion dollars in The market is experiencing a growth of 40% CAGR. The sales revenue is projected to be 36 billion dollars in

2 The break-up of the photovoltaic value chain revenue is given in table 1. The total production in 2006 was 2.4 GW, which is projected to be GW by 2010 depending upon the pessimistic or optimistic view of the poly-silicon availability and growth of thin film and concentration technology. It is recognized that one single technology will not provide the lowest cost energy in the different geographies of the world. One of the leading photovoltaic companies, has mapped the globe based on solar insolation and identified the most optimal technology for different regions. The map identifying the technology for different regions is given in fig.2. It is evident that crystalline silicon modules are optimally suited for the regions were sun light is of diffused nature. Thin film is applicable to hot and humid climatic conditions. Concentrator PV has an edge in regions where direct sunlight constitutes the majority of solar insolation. Realizing that different technologies will give the lowest cost solution in diverse geographies, Moser Baer has multiple business verticals ranging from crystalline silicon to concentrators. It may also be mentioned that as the volumes grow and efficiency of the solar systems increase the cost of PV energy will reduce and will come within the shooting range of the grid power. Higher throughput, thinner wafers and reduction in material cost due to volumes will make this happen. This is enumerated in the fig.3. Thin film has the greatest potential to reduce the cost of PV. Among all the thin film technologies amorphous silicon is the most mature and has potential to scale up. Manufacturing line is an integral part of supply chain and amorphous silicon has an edge over its counterparts. Amorphous silicon is benefited from the developments in the field of display technology where the deposition technique on large area glass substrate is very well developed. Studies at NREL show that it is possible to achieve sub dollar costs in thin film modules as shown in fig.4. CHALLENGES IN INDUSTRIALIZATION OF PV Photovoltaic industry is experiencing an unprecedented growth and it has put the supply chain under strain. While scarcity of poly-silicon is well known other raw materials which choke the supply chain are Tedlar and glass. Scarcity of raw materials adversely impacts the cost reduction of PV which is so essential for the growth of PV. The choice of materials is limited and it takes far too much time to qualify a material for PV application. Whereas there is a paucity of raw materials, lines of higher output are being installed. In order to utilize the line capacity and meet the market demand, one has to depend upon multiple sources of raw material, which poses the challenge of adjusting the process for different raw materials on a continual basis. Scarcity of poly-silicon has motivated wafer manufacturers to maximize output by reducing the wafer thickness. Thinner wafers pose challenge in handling, processing and packaging. The challenge is more severe for manufacturers having older process equipment. Thinner wafers also require process improvement in achieving efficiency at same levels as thick wafer. Processes like light trapping and back surface passivation assume greater importance for obtaining higher efficiencies. Additionally, thinner solar cells call for changes in module process as well. In order to maximize the output from the manufacturing facility, the industry is moving to faster lines having high throughput. High throughput has changed the requirement of the response time to process drift. It, therefore, calls for development of in-line characterization tools which can capture data in real time and assist in taking decisions for tweaking the process on the fly. Owing to unprecedented growth even the testing and certification infrastructure has come under strain. There is significant waiting period for testing the modules for certification of design and safety. Often there is a gap between the start of production and certification of the product. The value realization of uncertified modules is relatively low and carries a potential failure risk of field failure. 219

3 There is a need to develop accelerated test methods to shorten the testing time. Moreover, the present IEC tests are meant to qualify the design of the modules. There is very poor correlation between the performance of modules in the IEC test sequence and in-field performance. This calls for developing reliability models to accurately predict the life of modules. A few failure modes which are observed in the field do not show up in the IEC test and this indicates that IEC test in its present form is not sufficient and need revision. At present the entire PV infrastructure is geared to cater to the needs of crystalline silicon and thin film industry as they are more evolved. However, the second generation technologies such as concentrator and nanotechnology are on the horizon. The present solar simulators work on the principle of total incident irradiance. They do not separate the direct and diffuse component of light. In order to test the performance of concentrator modules, particularly in the high concentration regimes, it is important to design the simulators which have direct component of light equivalent to the Sun. Similarly, the IEC test in its present form is analogues to the flat plate modules and qualifies the design of the concentrator modules. However, the high concentrator modules invariably require tracking and hence the reliability and design qualification of tracker is as essential as that of modules. At present the modules are sold based on wattage, i.e. $/W. The wattage delivered by the modules is based on a short duration Sun Simulator test. However, the entire economics for the user is dependent on the energy (kwh) delivered by the modules over its life time. Even if two modules have the same wattage it does not guarantee same energy output. The energy output is dependent on thermal schemes of the modules. There is a need for paradigm shift from $/W to $/kwh. Industry has grown rapidly and it has created shortage of trained manpower worldwide. Academic institutions can help tide over this crisis by initiating specialized courses and training programs. R&D programs in consultation with industries will also be mutually beneficial and rewarding. This will not only help develop technologies but will also create a pool of trained manpower in some specific areas of technology. MOSER BAER'S FORAY IN PHOTOVOLTAIC Moser Baer India limited (MBIL), a leading manufacturer of optical storage discs, decided to diversify into photovoltaic based on the synergy between the optical disc making process and solar cell processes. Moser Baer Photovoltaic (MBPV) is a subsidiary of MBIL and leverages the MBIL's strength in high volume manufacturing and prowess in managing the supply chain and logistics to bring down the product cost. MBPV at present has three business verticals, namely, crystalline cells and module, thin film PV and Concentration PV. Besides, MBPV has made strategic investments and agreements in specific areas. It has tied up with a couple of California based companies for manufacture of low and high concentration PV. Realizing the importance of silicon in the manufacture of cells, it has signed agreements with the wafer manufacturers like REC and DeutscheSolar. It has made strategic investments in SolarValue for securing low-cost solar grade silicon. While taking care of the present business it has not ignored the future and upcoming technologies. Investment in the nano-technology for photovoltaic application corroborates its conviction to bring the state-of-the-art technology to India and for the benefit of the market. It is continuously evaluating new proposals and prospects meant to grow the business organically as well as inorganically. We are committed to provide clean and low-cost energy solutions to the world and India in coming years. CONCLUDING THOUGHTS Photovoltaic industry is on the cusp of change because of unprecedented growth in the recent past. Industry infrastructure, be it delivery time of manufacturing lines, or supply chain, or the testing, has 220

4 come under strain due to fast growth. There is a need to leverage the developments in the other PV areas as has been done in the amorphous thin film module manufacturing where the infrastructure of TFT technology is being exploited. While fast growth creates opportunities it has the added risk of sub-standard quality in the various stages of value chain. Since the size of the industry is going to be big enough to impact the business and social environment, it is important to pay attention and reexamine the established practices. Academia has an important role to play in this growth by creating a pool of trained manpower in this discipline. Needless to say, the quality of decision and innovation coming out of the trained manpower will be far more superior and robust. INDEX OF FIGURES AND TABLES FIGURE 1 Energy cost of various energy sources FIGURE 2 Global map of technology based on solar Insolation FIGURE 3 Cost reduction projections for thin film and crystalline silicon modules FIGURE 4 Cost projections by NREL for amorphous silicon thin film modules TABLE 1 Present and projected sales revenue (in 100 million USD) of Photovoltaic industry across value chain (Materials One ) Fig.1 Energy cost of various energy sources. 221

5 Fig.2 Global map of technology based on solar insolation as worked out by SHARP Fig.3 Cost reduction projections for thin film and crystalline silicon modules. Fig.4 Cost projections by NREL for amorphous silicon thin film modules 222

6 Table 1: Present and projected sales revenue (in 100 million USD) of Photovoltaic industry across value chain (Materials One ) Components of value chain Poly-silicon Silicon wafer Cell Module Inverter 9 22 Other Parts 9 19 Installation Others (services, after sales, etc) Total **** 223