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"Cold" eyes on the sidelines of solar cell market circles, something wrong - [business news]2011-08-23
"Cold" eyes on the sidelines of solar cell market circles, something wrong
Introduction: the German "Handelsblatt" reported on the 18th, two years of international silicon prices have fallen sharply, from 500 per kilogram to $ the current less than $ 50. All this seems to have originated from an oversupply of polysilicon industry the past two years, "excess capacity", "cost-benefit", "prospects" and once again become the solar photovoltaic industry focus.
Polysilicon is a "true excess" or "to be excessive."
Under the State Council issued "on the inhibition of excess capacity and duplication of the notice", the wind power equipment and two new major energy industry polysilicon was first included in the repeated construction of the column. Ever since, the original mission to promote industrial restructuring, new energy has become the object of being adjusted; and environmental protection for the purpose of the original Fengjie to polycrystalline silicon photovoltaic materials to be labeled anti-high energy consumption, high pollution, the label - for a time, China's new energy industry, as if trapped in a Gogol-style satire.
Production of silicon solar cells as the main raw material supply bottlenecks occur in 2007-2008, due to surge in demand for solar energy industry, silicon became a scarce resource. But the financial crisis and other factors, on the one hand the current solar industry growth than expected, Germany and Spain began to cut subsidies for solar power, solar power in 2009 new peak in 2008 was only 1 / 4. On the other hand, launched two years ago, rush silicon production project has been put into operation one after another, the output is growing, contributing to the current oversupply of silicon. Market analysis firm iSuppli to a study in 2009, the actual needs of the global silicon production more than 44,000 tons. With the more projects into production, silicon oversupply will worsen. While Italy, the United States and other countries will be the new solar energy market, but still not enough to offset the expansion of silicon production capacity. iSuppli predicts 2011 global production will exceed 200,000 tons of silicon, silicon needs of 14 million tons of surplus production increased to 60,000 tons.
Ministry of Commerce will limit polysilicon processing trade exports and open a "medicine." However, even if long been branded a "surplus" mark, the polysilicon industry, "is excess" argument is heard.
NDRC Energy Research Institute, Centre for Renewable Energy Development Ren Dongming, Deputy Director: "From the future development, the polysilicon is not necessarily true surplus, China has not yet form a complete solar power price mechanism, the domestic market does not start, solar cell applications prospects are not clear. "
Strategic Research Institute under the Ministry of Science and research shows that while polysilicon capacity expansion soon, but because of the construction cycle and the reasons for fluctuations in the market, has been in short supply, large gaps still need to rely on imports to fill. Semiconductor equipment and materials from the National Standardization Technical Committee data show that in 2009 actual production of polysilicon is only 14,000 tons, and imports were flat.
Broker is expected to show that the mainland's polysilicon production in 2010 up to 45,000 tons, semiconductor and solar cell totaling 44,960 tons of polysilicon, polysilicon supply and demand balance; domestic battery production in 2011 will grow 40 percent to 7168MW, at 7.5g / w calculated take 53,760 tons of polysilicon, assumed to be polycrystalline semiconductors up 25% to reach 5,000 tons, the total domestic demand for polysilicon to 58,760 tons, domestic production is expected to reach 800 million tons, the pressure of oversupply.
For the emerging understanding of the industry should not be the same in some mature industries, for their 'surplus' should be taking a tolerant attitude. Capacity growth of new industries, for a perspective means that the attention and access to capital, this just shows there is a breakthrough development of the industry and upgrade possible.
Polysilicon prices are no longer return to the old value of profits is inevitable
The price of polysilicon in 2008 are crazy hard, and gradually return to the value of the industry's consensus. It is reported that the domestic tax price of 410,000 -42 yuan / ton, is expected to slow as demand for photovoltaic cells, the urgency of the demand for silicon material decline in the second half of the silicon material price pressure. The brokers report that, with the polysilicon production technology breakthrough, the domestic silicon material costs will decline; photoelectric conversion efficiency as well as silicon materials cutting technology, the battery unit will reduce the amount of silicon, the long-term prices will return to value.
Second, the new energy technology revolution there are many variables. For example, crystalline silicon cell industry expected conversion rate in recent years from 17% to 20%, such as the use of new technologies and new materials, the efficiency of even this can be increased to 30-50%.
The conversion rate of solar cells increased by one percentage point each, the cost will drop 7%. Just think, if the next breakthrough in the field of photovoltaic technology innovation, and its cost has dropped significantly to the price even lower than the thermal power with thermal power costs, the resulting active market capacity will be "infinity."
Long-term view, then, today Jiang Yi's production capacity will then develop into tomorrow's bottleneck?
Moore's Law in the solar cell industry
Little knowledge of the IT people will not be bound to the world-famous Moore's Law, Intel founder Moore gains, the fact that, Moore's Law still has vitality today, but not limited to the IT industry, representatives from the solar The same applies to the new energy industry.
According to Moore's Law, with the advancement of technology, industrial technology matures, the cost of solar power will become more affordable, and ultimately achieve even without subsidies can also be competing against traditional fossil fuels situation.
However, the chip and solar panels on the surface but there are similarities. Both involve silicon and electricity, some processing techniques are the same. However, the production of solar panels is much simpler, and high yield. A factory can produce 3000 per hour, usually silicon wafers, each wafer to form a solar cell. By contrast, the modest size of a semiconductor plant may be a year to produce 200,000 chips. This is a high accuracy of the industry, because each chip can be made of 10 million chips.
Photovoltaic power generation is the use of solar cells solar energy into electrical energy, can be used independently, but also to the grid. The rapid development of China PV industry in 2000, only 3 MW solar cell production, the end of 2007 to 1088 megawatts, ranking first in the world.
Stock market: the new energy sector prospects
China's economy in the long run, the theme of the new energy sector is very obvious characteristics, duration and space longer.
Recent fundamental changes in the new energy sector, we believe that policy is still more obvious bullish signal, expected volatility of investment opportunities. The new energy sector in the A-share market is relatively large plate, cover wind, solar, nuclear, energy-saving materials and other fields. New energy as China's economy to achieve the promise of low-carbon development goals important force in recent years has been attached great importance to the national level, the relevant industrial policies intensive. The present stage, we believe that the new energy vehicles, new energy battery two segments may be a greater chance of volatility, the policy faced many benefits can be expected.
New energy battery will benefit from new energy vehicles, electronics tech and other long-term benefits of technological innovation. Online Chinese government published a "State Council on further intensify its efforts to ensure the realization of" five "emission reduction targets," which pointed out the need to continue to work out a new energy vehicle demonstration. Relevant to the end of May before the introduction of specific implementation details, this time limit is approaching. New energy official launch of the automotive market, both in terms of the whole industry chain development opportunity. As the future mainstream car battery lithium ion battery industry will face more background to promote interest. We are optimistic about the potential for species in which the volatility of the opportunity. Such as the Vosges stake Corun, Desai battery billion Wei Li and so on. The reason we are concerned with the volatility of the opportunity stage, mainly on account of the overall market will continue to be weak, but the policy context of profitable opportunities for the species is more volatile performance of the probability of large.
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Bac2's ElectroPhen fuel cell materials by the European Patent
Bac2 Company (Southampton) ElectroPhen conductive polymer material of European material has been patented. Currently, the material scope of the patent covering Germany, France, Spain, Italy and the UK. Japan, Canada, the United States, South Korea, India and China, the right to use the material patents pending.
According to reports, Bac2 phenolic polymer prepared by the company invented a new method of electrical conductors. ElectroPhen and other phenolic polymers difference is ElectroPhen resin in the water is removed and replaced with the resin compatible solvents, which greatly helped to play its dual effect of the catalyst, on the one hand play a catalytic resin polymerization role, one can transmit a positive electrical properties.
Raw materials ElectroPhen conductive properties than other polymers is 10 billion times, and manufacturers can add other ingredients for the material (such as: graphite, metal powder, plasticizers and enhancers, etc.), it is widely used in other areas. Meanwhile, Bac2 company has also developed a process of aggregation delay implicit acid catalyst - CSR10. It helps pre-polymer mixture in the polymerization reaction occurs even before being transported to be stored up to several months, thus greatly improving the flexibility of the production process, and thus reduce the cost. ElectroPhen inherent conductivity make it the fuel cells and other energy storage devices the ideal choice, radio show and will be used for ESD protection, and the heating element and heat sink production.
Bac2 CEO Michael Costa can (MikeStannard) said: In the present case, the private company for a new patent can be granted the basic material is very difficult. It demonstrates our expertise in reserves, and by the Ge Leie.'s Development team led by Dr. Bromley's innovative capacity. Before us is a great application potential future market. Our next focus will be on green technology, ElectroPhen characteristics of the product will make it a low-cost production of fuel cell components of an ideal material.
About Bac2 Company:
Bac2 Founded in 2002, its founder is Gelei E. Dr. Bromley. Bac2 company is committed to the development of commercial-scale conductive polymer composites. Mike Stannard joined Bac2 in 2005 as CEO, helping companies in the fuel cell market and the electronics industry business development. Bac2 is a privately held company, and has been successful in London Seed Capital (LondonSeedCapital), London Business Angels (LondonBusinessAngels) and other investors in the financing. In addition, Bac2 company from the Carbon Fund Association (CarbonTrust) and the British Trade and Industry (DTI) to help get the project section.
German solar energy demand in 2010 will continue to boom
German solar energy demand in 2010 will continue to boom, according to the German Solar Industry Association (German Solar Industry Association, BSW-Solar) in May 2010 released at the end of the forecast, in 2010 the German solar facility will be double-digit rates of growth. As of 2009, the German solar power industry and its suppliers have sales of more than 100 million euros, are now directly engaged in the photovoltaic industry, the total number reached 60,000.
In 2009, the German solar facility needs increased substantially, according to Federal Network Agency statistics new set of photovoltaic power generation capacity of 3.8 GW. Now with the German power grid to set the total amount of PV has reached nearly 10GW.
In view of the German Bundestag in May 2010 by the Renewable Energy Law (Renewable Energies Act, EEG), expected 2010, the solar industry will once again achieve significant market growth. The bill from July 1, 2010 onwards will significantly reduce the solar tax, and implementation began in 2011. This includes roof-mounted system reduces the tax of 16%, ground-mounted systems and other facilities to reduce taxes by 15%.
Since the end of 2009 the total installed capacity of more than 9.8GW, so Germany is still the world's largest solar energy market.
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Silicon wafer solar cell factory to be up the next offer will strike back - [business news]2011-07-28
Silicon wafer solar cell factory to be up the next offer will strike back
Silicon wafer for solar energy in June, according to the original plan to hike the proposed offer, the solar cell industry believes that this strategy is "Mao Yin food grain", once in July the German solar subsidy cut, expected demand shocks will therefore, if silicon wafer to the last moment not to give up prices, weak demand encountered in the follow-up battery factory, or if the oversupply situation will slow the pace of expansion and lower capacity utilization, the silicon wafer will experience more powerful client counterattack.
Solar industry confirmed that the solar silicon shortage is still the situation continued to show and also verbally inform the silicon wafer will raise prices again in June. Industry said that if June is still in short supply of silicon, silicon wafer does in accordance with the requirements of the purchase price increase to the module in response to customer demand, and a final sprint.
Solar industry said that many Silicon wafer demand estimates are based on the battery factory capacity to estimate, so that the silicon wafer is how to expand total capacity battery than the total capacity, however, it has been difficult to fully satisfy that wafers battery factory needs.
However, the solar industry said that regardless of the battery, or silicon or polysilicon, that form the world's total production capacity of view, the total demand are too high, indicates the existence of effective supply-side or supply problems, the final demand must be demand estimates are based on the terminal.
In other words, if the battery factory experienced weak demand or oversupply situation will inevitably slow down the pace of expansion and lower capacity utilization, the relative demand for silicon wafers will follow the lower, then cut the price of materials is inevitable, silicon fab subsidies in Germany last month insisted prices, customers in the future will lead to the battery can not be soft and more time haggling, Strategies silicon wafer prices in June as "Mao Yin eat food."
Battery industry frankly, if weak demand, a stronger bargaining power of buyers, the seller must buy, especially after the second half of the German cut subsidies under the incidence of higher prices if the success of solar silicon in June, is with the battery factory into? Part of the battery factory frankly, do not rule out the follow-up response to rising costs.
But part of the battery plant is disclosed, in May there has been a standard battery offer no further hike in June will be dynamic, as do the environment assessment is still not dare change the price.
Zhang coat film becomes attached mobile phone charger
Yu Qiakuai this year's signing of project results, once again confirms the capital of the industry is keen to change. Yesterday's news from the organizing committee, and real estate projects in previous years to play the main difference is that this year, new energy, IT, carbon and other emerging industries sought after popular global capital from various quarters, to become the highlight of contract.
Perhaps people see in American movies, such a scenario - a soldier in camouflage posted a few films, even if the body in the jungle, the film also can be used to collect solar energy for the computer and cell phone charger, so that timely reporting of information. The near future, such products can be achieved, "Chongqing made" up.
Yesterday, Jiangjin and Yi Yang (Hong Kong) Co., Ltd. Yu Qiakuai on the contract, which will invest $ 10 billion, the largest building in the area of thin film solar cell project.
Construction of production bases to open in June
It is understood that, compared with conventional solar cells, thin film solar cells are smaller, the conversion rate of solar energy is also higher. This product is also used extensively for automotive, mobile computer charging, the roof heating and so on.
According to the agreement signed yesterday, Yi-yang (Hong Kong) Co., Ltd. in Chongqing Investment thin film solar cells production base, located in Jiangjin double blessing, with a total construction scale of 1GW (gigawatt). "This will be the largest thin film solar cell manufacturing base." Shuangfu New Area Administrative Committee, said Zhou Chao, deputy director of the project a construction start in June this year, will also simultaneously launch headquarters and global R & D center in Chongqing project .
Investors are prepared behind the scenes
10 billion yuan investment is not a small number of investment companies are backing? Yesterday, the reporter through the multi-query, still can not understand Yi Yang (Hong Kong) Limited for more information.
Zhou Chao said, Yi-yang (Hong Kong) Limited is actually a thin-film solar cell technology team, the real investors are three natural persons. One of Shaanxi people this year, more than 40 years old, he engaged in food and capital market operation, very low key. Yu Qiakuai in yesterday's signing ceremony, attended the mystery investors left the venue immediately after the ceremony, stay does not exceed 10 minutes.
"According to our understanding of the situation, the project's funding comes mainly from three investors, private equity funds will also be introduced together." Zhou Chao said early before deciding to invest in Chongqing, the mystery investors invited in Jiangsu thin-film solar cell technology R & D team, the sample is expected to come out in September.
Annual sales value of up to 20 billion
It is understood that Jiangjin film solar cell projects are expected to be fully operational in 2014, the project put into production, the annual sales value of 20 billion revenue over 20 billion yuan.
Zhou Chao said in October last year, the project investors started investing in the country study. Sichuan, Shaanxi, Liaoning and other provinces of the cities into the options. Optimistic about the country as a result of the five cities of Chongqing, one of the development prospects of the low labor cost factors, will eventually lock eyes Chongqing.
Bark generating 500 million Liangping signed the largest single
In addition to thin-film solar cell project, there are a number of companies targeting the new energy industry, yesterday, the Singapore Green Branch Holdings signed an agreement with Liangping, plans to invest 500 million yuan investment in the industrial park development Liangping biomass power generation projects; Yubei the introduction of Yangtze River Kang (Dipu Sen) company, invested 500 billion yuan to build new energy R & D base.
It is understood that Liangping biomass power generation project will make full use of Liangping existing waste biomass resources, such as bark, etc. to build power plants. Currently, waste biomass resources Liangping holdings of 30 million to 50 million tons / year. The power project is expected to achieve annual output value of 500 million yuan, profits of 050 million yuan, to resolve labor force 300.
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Amorphous silicon thin film solar cell and module production line to start building - [business news]2011-06-27
Amorphous silicon thin film solar cell and module production line to start building
An investment of 1.2 billion, the city's first 60MW of amorphous silicon thin film solar cell and module production line started yesterday in the dual stream. An Chengxin former State Department Deputy Secretary-General, former political commissar of the Beijing Garrison asked Roy Tan Hardy, deputy secretary Tangchuan Ping, vice president of Federation of Chinese private enterprises Dibing Kai, Vice Mayor Bai Gang attended the ceremony.
For a positive role in promoting industrial upgrading
The total 450 acres of land for construction planning, which projects an investment of 1.2 billion yuan, covers an area of 180 acres, the annual output of 60MW of amorphous silicon thin film solar cell and module production line put into operation in late 2010, is expected to put into operation The annual sales income of 1.08 billion yuan to solve the employment of 500 local people.
According to the plan, two projects will expand the 150-200MW and amorphous silicon thin film solar module production line, while building 1-2 of TCO coated glass production line. Project is put into the annual sales income of 5.0 billion, more than 2,000 people to address local employment.
Responsible person, the two-Solar Technology Co., Ltd. Chengdu Xu 60MW amorphous silicon thin film solar cell and module production line in the dual stream successfully started production of its construction projects in Sichuan Province and the city is bound to play an active industrial upgrading role.
Production of the world's leading technology and product performance
According to reports, Solar Energy Technology Co., Ltd. Chengdu Xu double by Chengdu Xihanggang Construction Investment Co., Ltd., Chengdu Industrial Investment Group Co., Ltd., Hebei Yuk Investment Group Co., Ltd. and Beijing Tai Yi Si Solar Technology Co., Ltd. joint venture established to develop , manufacturing, sales amorphous silicon thin film solar cells and related technical services to provide high-tech companies.
Project controlling shareholder Hebei Yuk Investment Group is currently the only company with R & D, design, manufacturing and technical support, a full set of independent intellectual property rights of FPD glass substrate manufacturing enterprises. The company's amorphous silicon thin film solar cells and modules are developed independently, with independent intellectual property saving products, production process using equipment of international advanced level of maturity, high yield, and operable, production processes and product performance reached world leading level.
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Rooftop solar power demonstration area will be built in Chengdu
Sichuan Provincial Development and Reform Commission recently released the "Sichuan PV industry development and construction planning environmental impact assessment notice" display: 2015 and 2020, respectively, of solar generating capacity of 30 MW and 100 MW, Chengdu, Panzhihua and other places will be built solar building integration and application of photovoltaic products, demonstration area.
According to the plan, said Sichuan will develop solar module production while increasing the proportion of thin-film solar cells. 2015 solar cell production reached 3,000 MW, 5,000 MW by 2020. Among them, the proportion of thin-film solar cells is about 50%.
And based on the original foundation and industry to consider the advantages of convenient transportation, the layout of the city Shuangliu film solar cell manufacturing base. Focus on building new film cadmium telluride, cadmium sulfide solar cell production line and amorphous silicon thin film solar cell production line.
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Passive direct methanol fuel cell performance influencing factors
Constraints of the passive direct methanol fuel cell (passive DMFC) performance factors. Battery by measuring the polarization curves, power density curve, the long discharge curve means of a passive fuel cell cathode feed at different ways for different anode material way, different catalyst load, temperature and other conditions, different battery discharge characteristics. The results show that: the cathode causes the oxygen diffusion rate is slow passive less battery performance a major factor in feeding the cathode when the cell by active compared to passive DMFC performance increased by 23.5%, maximum power density of 8.4 mW? Cm? 2 . Cathode flooding problems and constraints of the passive DMFC performance of the long discharge. Improve the anode and cathode catalyst loading can significantly improve the cell performance, anode and cathode catalyst loading was 4.0 mg? Cm? 2, the maximum power density of 11.4 mW? Cm? 2. However, the improvement of catalyst loading time will affect the battery discharge performance, in particular, to improve the cathode catalyst loading can significantly increase the battery temperature, so the battery can be significantly improve performance.
Direct methanol fuel cell (Direct Methanol Fuel Cell, DMFC) with methanol as wide variety of sources, easy to carry, store, add convenience, volume and quality than high energy, simple structure, without external reforming equipment and so on [1 ~ 5], and In the portable power and small civil power, and so has broad application prospects. Particularly in recent years passive direct methanol fuel cell (referred to as passive DMFC), is considered the most market potential and the most portable electronic device battery requirements for the development of a fuel cell [6,7]. The structure of passive DMFC shown in Figure 1 can be seen from the figure, the passive DMFC anode feed methanol and oxygen feed are not using cathode outer circulation pump, the anode chamber with a methanol storage, rely entirely on the supply of methanol, methanol molecules from the methanol self-diffusion to the electrode chamber; cathode oxygen supply is totally dependent on oxygen in the air by concentration diffusion and transfer in the form of air convection diffusion to the cathode catalyst layer for electrochemical reduction reaction. Therefore, in addition to methanol, passive DMFC to peristaltic pumps, air pumps and other auxiliary equipment, and battery heated humidification devices, which reduces the battery's own energy consumption, more streamlined structure of the fuel cell system, the battery weight and volume of the system to better meet the portable power supply requirements. Many domestic and foreign researchers of the passive DMFC were related research. Zhao [8], Jiang [9], Faghri [10,11] and other researchers studied the different operating conditions of methanol concentration on passive DMFC cell performance and battery efficiency. Chen [12], Kim [13], who features for passive DMFC Development of a new type of electrolyte membrane and membrane electrode structure. Yang [14], Chen [15], who detailed study of passive DMFC, anode and cathode collector materials and structures. However, passive DMFC restrain the major factor in the practical application is still relatively low active DMFC performance at room temperature, the maximum power density of active DMFC generally only 1 / 3 to 1 / 2 between [10]. As for the various factors on the performance of passive DMFC has not studied in detail. Lead to lower performance of passive DMFC generally have the following reasons: (1) slow diffusion rate of methanol anode; (2) slow diffusion rate of air cathode; (3) low temperature; (4) cathode of water flooding problems. This paper will begin the four factors to find the impact of passive DMFC performance of the main factors.
2 Experimental
2.1 The membrane electrode (MEA) preparation
This experiment made use of the catalyst was the catalyst [16]. Anode catalyst was 40% (wt) Pt-Ru (atomic ratio 1:1) / C; cathode catalyst was 40% (wt) Pt / C. Preparation of cathode and anode: carbon paper (Toray TGP-H-090) on the coating layer of 1.0 mg? Cm? 2 Vulcan XC-72 carbon black and 20% (wt) PTFE (20% (wt) Nafion solution) as anode and cathode diffusion layer, and then in the inert gas diffusion layer 340 deg under the protection of sintered 30 min. A certain amount of catalyst into the isopropyl alcohol, add a certain amount of Nafion solution for several hours after the ultrasonic dispersion to form a homogeneous slurry, to scratch the surface in the diffusion layer. Nafion content in the catalyst layer was 30% (wt), the metal loading was 2.0 mg? Cm? 2. Finally, on the pretreated Nafion membrane between the anode and cathode, in the 80 kg? Cm? 2,135 deg, 2 min under the conditions of pressing into the MEA, the work area of 鈥嬧€? cm2.
2.2 Battery Performance Test
Direct methanol fuel cell polarization curve for using Arbin fuel cell test system (Arbin Instrument Corp.), Passive DMFC testing, the anode chamber with methanol 2.0 mol? L? 1 passive feeding methanol and water, using air-breathing cathode inlet material. Active DMFC testing, the anode side of the pass into the aqueous solution of methanol concentration 2.0 mol? L? 1, flow rate 5.0 mL? Min? 1, the cathode side of the pass into the atmospheric air flow rate of 300 mL? Min? 1. Long battery constant current test was carried out under a constant current density of the test. Cathode photo collection using a digital camera to take pictures. Ambient temperature is 30 deg.
3 Results and discussion
3.1 Mass Transfer
Different feeding methods on the performance of the battery shown in Figure 2. It can be seen, when the anode and cathode are used actively feeding, the battery has the highest performance, maximum power density of 11.5 mW? Cm? 2, and the highest open-circuit voltage, this time using atmospheric air into the cathode material. The battery anode and cathode used in all passive performance when feeding the lowest maximum power density of 6.8 mW? Cm? 2. Yin and Yang are changed very active feeding mode, the battery performance has improved significantly, indicating that passive DMFC slower and slower diffusion rate of oxygen diffusion rate of methanol caused a performance degradation. In particular, when the passive into the cathode material, anode active feeding, although the anode to improve the mass transfer rate of methanol, but the performance of the battery anode and cathode are used with passive feed less, the maximum power density of 7.4 mW ? cm? 2. Conversely, when the anode feed using passive, active feeding the cathode, the battery performance although the more active there are still large gap between the battery, but the relative performance of passive cells increased 23.5%, maximum power density of 8.4 mW? Cm ? 2. Further investigated using a variety of feeding mode the battery under the constant current long-running performance. Figure 3 shows the constant current of 33.3 mA? Cm? 2 long under the discharge curve. Methanol in the test chamber in the methanol solution was 10 mL, while the anode using active feed, to ensure the total amount of methanol 10 mL. It can be seen from the figure, with the continuous consumption of alcohol, continue to lower until the battery voltage is about 0V. When the anode feed using passive, active cathode material into the discharge during a longer time and more stable discharge platform. The other two operating mode similar to the discharge time and discharge plateau is slightly tilted. In order to study the causes of this phenomenon, we have the battery constant current discharge of water generated in the cathode side of the situation, and so the observation. Figure 4 is 33.3 mA? Cm? 2 60 min, constant current discharge passive (a) and cathode passive (b) cathode side of the water content of the photo. As can be seen from Figure 4, both passive (a) and cathode passive (b) of the cathode side, there are many small water droplets in the cathode diffusion layer surface. As the discharge time, the phenomenon of the cathode will be increasingly more severe flooding. This limits the mass transfer of oxygen in the cathode side, resulting in oxygen diffusion layer can not be passed to reach the catalyst layer, involved in electrochemical reaction. So with the continuous accumulation of water leads to the continuous decline in battery performance, making the discharge platform tilt. In contrast, when only the use of passive feeding the anode, due to the cathode air is constantly moving around, and can continue to be generated inside the battery out of the water from, less flooding problem situation, so the more stable discharge platform.
Temperature for the DMFC performance of larger. With increasing temperature, the catalytic activity increased, the performance of the battery will gradually increase. Figure 5 shows the passive DMFC at different temperatures and active DMFC polarization and power density curve. It can be seen from the figure as the temperature rises, the battery's open circuit voltage gradually increased, due to the rise in battery temperature, the catalytic activity increased, resulting in a higher open circuit voltage. For the same reason, at the highest power density values at the voltage increases as the temperature gradually increased. In order to study in detail the temperature increase for the passive DMFC anode and cathode mass improvement, with the same temperature, the performance of active DMFC are compared in Table 1. As can be seen from the table, at a lower temperature, passive and active DMFC performance of DMFC is not much difference, and between 20 deg to 40 deg, the rate of increase in performance between the two are small. But when the temperature is raised to 60 deg, the active DMFC's performance has improved significantly, improving the performance of passive DMFC is not obvious. At a lower temperature, the activity of the electrode is not very high, passive
Still capable of methanol and oxygen supply to meet the requirements of the battery reaction, the different ways of feeding did not produce a greater impact. At higher temperatures increased the catalytic activity of the electrode, the methanol and oxygen transmission rate requirements increase. In a passive DMFC, the oxygen and methanol supply entirely on free diffusion, slow diffusion rate and temperature can not fully play the role for improving battery performance.
Figure 6 for different anode catalyst loading of the catalyst layer thickness. It can be seen, with the catalyst layer to increase the amount of catalyst contained in the catalyst layer thickness increases almost linearly. Passive DMFC with different anode catalyst loadings on the performance of the battery shown in Figure 7. In the cell polarization curve, the low current density area is mainly controlled electrochemical reaction zone, the same current density, voltage level representative of the general level of electrochemical activity. In the high current density areas, battery performance mainly reflects the characteristics of mass transfer within the electrode. Figure 7 (a) can be seen in the low current density area, the same current density, with the anode and cathode catalyst loading increased, the battery voltage is gradually increased, indicating that increasing the catalyst loading increased the electrochemical activity of the battery . In the high current density areas, the same current density, when the PtRu and Pt loading to 4.0 mg? Cm? 2 when the polarization minimum, to further improve the PtRu and Pt loading, the battery voltage drops. Increased catalyst loading will increase the thickness of the catalyst layer, the reactants and products of the mass transfer resistance will increase, increasing the concentration polarization overpotential, the battery voltage is decreased. Figure 7 (b) can be seen, when the anode and cathode catalyst loadings were 4.0 mg? Cm? 2, the performance of the highest, reaching 11.4 mW? Cm? 2. The anode and cathode catalyst loading, respectively, 6.0 mg? Cm? 2, due to increased concentration polarization, the performance declined. See Figure 7 (b) when different catalyst load the highest power density mapping 8. It can be seen from Figure 8, the increase in the cathode catalyst loading on the battery performance improved greatly help. When the anode catalyst loading increased to 4.0 mg? Cm? 2, the battery maximum power density increased by 47.4% to 8.4 mW? Cm? 2. The cathode catalyst loading increased to 4.0 mg? Cm? 2, the battery maximum power density increased by 70.2%, reaching 9.7 mW? Cm? 2. In order to study the causes of this phenomenon in the open circuit test the battery under load with different catalyst temperature when the battery shown in Figure 9. Can be found from Figure 9, when the anode catalyst loading increases, the battery temperature is not significantly increased, and when the cathode catalyst loading increases, the battery temperature is significantly higher, when not using cathode electrode catalyst layer of the test, found that the battery temperature is not
Have changed. Battery temperature for two main reasons: (1) electrochemical reaction heat; (2) the oxidation of methanol permeation to the cathode reaction heat. Anode and cathode catalyst loading can accelerate the increase of the electrochemical reaction rate, so as to enhance the battery temperature. The increase in cathode catalyst loading on the one hand can reduce the methanol poisoning of the cathode to improve battery performance; the other hand, increase the oxidation rate of methanol in the cathode, increase the battery temperature. Therefore, the improvement of cathode catalyst loading greater impact on battery performance.
Anode and cathode catalyst loading of the different time of discharge performance of battery shown in Figure 10. As can be seen from Figure 10 with the anode and cathode catalyst loading increases, the battery voltage gradually increased, due to the increase of catalyst loading and improve the battery performance, so in constant current discharge process has a higher discharge platform. For the active catalysts for DMFC increased load will increase the battery discharge stability [17], but the passive DMFC material transfer rate is slower, increasing the catalyst loading resulted in increasing the thickness of the catalyst layer, and further deterioration of the battery mass transfer rate, resulting in lower discharge performance for a long time. In particular, when the cathode catalyst loading increases, the discharge time was significantly shortened. This is due to the improvement of the cathode catalyst loading, the cell temperature was increased to accelerate the penetration of methanol to the cathode diffusion rate and the rate of the atmosphere, making the consumption of alcohol increases, affecting the battery discharge time.
4 Conclusion
(1) to improve the rate of oxygen diffusion cathode can substantially improve the performance of passive DMFC. Slow diffusion rate of oxygen led to a passive DMFC is the main reason for lower performance.
(2) cathode limits the flooding problems of mass transfer of oxygen in the cathode side, resulting in oxygen diffusion layer can not be passed to reach the catalyst layer, involved in electrochemical reaction, affecting the long passive DMFC discharge performance.
(3) the performance of passive DMFC with the battery temperature rises gradually increased.
(4) anode and cathode catalyst loading changes on the performance of passive DMFC have significant impact. The increase of cathode catalyst loading can improve the penetration rate of oxidation of methanol in the cathode, the role of the cell temperature was increased, the improvement of battery performance have a greater role in promoting.
(5) improve the anode and cathode catalyst loading time will reduce battery discharge performance. The improvement of cathode catalyst loading was significantly increased battery temperature will accelerate the penetration of methanol to the cathode diffusion rate and the rate of the atmosphere, making the loss of methanol increases, leading to the shortest discharge time.
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