Human society is facing a crisis of exhaustion of coal, oil, natural gas and other energy sources. For this reason, in the past 20 years, the Chinese government has attached great importance to the protection, development and utilization of energy resources, and scientists are also accelerating the search for inexhaustible renewable energy to solve the serious shortage of non-renewable energy and ensure it Economic and social development needs.
Biophotovoltaic (BPV) uses microorganisms (such as cyanobacteria) as photoelectric conversion materials, and has the characteristics of carbon neutrality, good environmental compatibility and potential low cost. According to recent media reports, in order to improve the BPV photoelectric conversion efficiency, the Li Yin research group of the Institute of Microbiology of the Chinese Academy of Sciences took a different approach and designed and created a synthetic microbiome with directional electron flow to solve the problem of weak direct electricity production activity of cyanobacteria, which is expected to become more environmentally friendly. Friendly new generation solar power generation technology.
The research results have aroused great concern from the global industry. So, what are the main principles of traditional photovoltaic power generation, and what are the negative problems? In addition to the photoelectric conversion efficiency, what are the indicators for evaluating photovoltaic power generation efficiency and environmental performance? What is the principle of bio-photovoltaic power generation, and what problems still exist in its bio-photovoltaic technology? What are the innovations in the new technology?
Traditional photovoltaic power generation has time and geographical restrictions
Industry insiders told reporters that humans have long relied on renewable energy sources in the historical process, such as fuel wood, straw and other biomass energy sources. Most of these energy sources come from the conversion of solar energy and are renewable energy resources.
"Traditional photovoltaic power generation mainly uses the photovoltaic effect of semiconductors. Specifically, when light hits the semiconductor surface, the light energy that meets the conditions will be absorbed to generate negatively charged electrons and positively charged holes in the semiconductor. The two are collectively called carriers. "Xi Xi, an associate researcher in the Department of Optoelectronic Information Science and Engineering at the School of Science of Jiangnan University, said in an interview with reporters that if we find a way to export these carriers, we can convert light energy into electrical energy. Output.
Xi Xi believes that at present, photovoltaic power generation still has a relatively large advantage in the field of renewable energy. Relative to wind energy, the installation of photovoltaic power generation can be distributed to all households, as long as there is a certain site for every ordinary person, a photovoltaic power generation system can be installed more or less; ordinary people can not install wind power generation.
"However, photovoltaic power generation systems also have time and geographical restrictions. The main limitations of the time domain are: photovoltaic power generation systems can only generate electricity during the day and cannot be used at night; even when the north is covered with snow and sand, the power generation during the day is also It will be limited; at the same time, there is great uncertainty in the light intensity during the day. Sometimes it floats over a cloud and is sometimes shaded by trees, which will affect the amount of power generation. Therefore, if the entire photovoltaic power generation system is connected to the grid, it will impact the power grid. Larger, it is necessary to do a good job of photovoltaic power generation system control and power grid regulation. "Xi Xi said.
But Xi Xi said that the currently widely used silicon-based solar cells will produce such as acid, alkali, metal waste water and exhaust gas, etc. Although the product itself is environmentally friendly, it is necessary to strictly treat and control the waste discharge in the production process, and its recycling , Separation and reuse also face many environmental challenges.
Bio-PV has higher conversion efficiency
Experts generally believe that biophotovoltaic has a higher conversion efficiency than traditional photovoltaics, which will be more conducive to the sustainable development of the environment and energy.
Biomass energy mainly refers to the energy that plants convert solar energy into chemical energy through chlorophyll photosynthesis and store it inside the biomass. It is second only to coal, oil and natural gas and ranks fourth in the world's total energy consumption. It occupies an important position in the entire energy system.
Biophotovoltaic uses photosynthetic microorganisms (such as cyanobacteria) as photoelectric conversion materials, and has the characteristics of carbon neutrality, good environmental compatibility and potential low cost. But the biggest problem of bio-photovoltaic power generation is that the output power of BPV system is very low, which is more than 3 orders of magnitude lower than that of solar photovoltaic. The main reason is that although photosynthetic microorganisms such as cyanobacteria have a high photosynthetic efficiency, the electricity-generating activity is weak. In the direct transformation of cyanobacteria to enhance its electrical production activity, there is still no breakthrough and it is difficult to apply it.
The reporter learned that the microbiome successfully synthesized by Li Yin's research team consists of an engineering cyanobacteria that can store light energy in d-lactic acid and a Shewanella that can efficiently use d-lactic acid to generate electricity. In this group of synthetic microorganisms, d-lactic acid is an energy carrier between two microorganisms.
Li Yin said that cyanobacteria absorbs light energy and fixes carbon dioxide to synthesize energy carrier d-lactic acid, and Shewanella oxidizes d-lactic acid to generate electricity, thereby forming a directional electron flow from photons to d-lactic acid to electrical energy. The energy conversion process from light energy to chemical energy to electrical energy.
Overcome the problem of physiological incompatibility between two microorganisms
The reporter learned that the innovation of Li Yin's research team is that through the design, modification and optimization at the genetic, environmental and device levels, they effectively overcome the problem of physiological incompatibility between the two microorganisms. The dual-bacteria biophotovoltaic system created in this way can achieve efficient and stable power output, and its maximum power density is generally more than 10 times higher than that of the current single-bacteria biophotovoltaic system.
According to the data, the research team of Li Yin adopts continuous fed-batch cultivation method, so that the dual-bacterium biophotovoltaic system can stably achieve power output of more than 40 days, and the average power density reaches a high level, the power generation time and the output of a single device The power has reached the highest level of the current BPV system.
It is particularly worth mentioning that this is the first time in the world that a synthetic microbiome with directional electron flow has been used to create a biophotovoltaic system, and it is also the first biophotovoltaic prototype device in China. Studies have shown that the synthetic microbiome can significantly improve the BPV photoelectric conversion efficiency, breaking people's inherent understanding of the difficulty in improving the biophotovoltaic efficiency and life, and laying an important foundation for further improving the BPV photoelectric conversion efficiency.
Experts believe that although biophotovoltaics provides a biological path for solar energy utilization, this is a brand new interdisciplinary subject. It should be said that bio-photovoltaic is still in the research and development stage in China, and it still has a long way to go before it can truly be applied on a large scale. (Reporter Guomin Zhong correspondent Lu Minzhi)
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