A brief history of AC surge arresters

Since the beginning of AC transmission, approximately 100 years ago, lightning protection of transmission equipment has been provided by gaps and by nonlinear resistors, alone or in various combinations. Protection during the early part of the period (1892-1908) was provided by simple air gaps from line to ground. During the period 1908 to 1930, nonlinear resistors based on puncturing and reforming of films came in to use. Further developments were oxide film arresters (1920-1930), silicon carbide nonlinear resistors with nonactive gaps (1930-1954), and silicon carbide nonlinear valve elements with active gaps (1954-1976). Current limitations of the types of arresters and the requirements imposed by 500 and 800 kV systems are discussed. The zinc oxide arresters that have been used from 1976 to the present are then considered. An approximate table of sparkovers, discharge voltages, and arrester height is given     

Sustainable hydrogen production options and the role of IAHE

In this paper, some potential sustainable hydrogen production options are identified and discussed. There are natural resources from which hydrogen can be extracted such as water, fossil hydrocarbons, biomass and hydrogen sulphide. In addition, hydrogen can be extracted from a large palette of anthropogenic wastes starting with biomass residuals, municipal wastes, plastics, sewage waters etc. In order to extract hydrogen from these resources one needs to use sustainable energy sources like renewables and nuclear. A total of 24 options for sustainable hydrogen production are then identified. Sustainable water splitting is the most important method of hydrogen production. Five sustainable options are discussed to split water, which include electrolysis, high temperature electrolysis, pure and hybrid thermochemical cycles, and photochemical/radiochemical methods. Other 19 methods refer to extraction of hydrogen from other materials than water or in conjunction with water (e.g., coal gasification with CO₂ capture and sequestration). For each case the achievable energy and exergy efficiency of the method were estimated based on state of the art literature screening for each involved process. In addition, a range of hydrogen production capacity is determined for each of the option. For a transition period to hydrogen economy nuclear or solar assisted coal gasification and fossil fuel reforming technologies – with efficiencies of 10–55% including CO₂ sequestration – should be considered as a viable option. Other “ready to be implemented” technology is hydro-power coupled to alkaline electrolysers which shows the highest hydrogen generation efficiency amongst all electrical driven options with 60–65%. Next generation nuclear reactors as to be coupled with thermochemical cycles have the potential to generate hydrogen with 40–43% energy efficiency (based on LHV of hydrogen) and 35–37% exergy efficiency (based on chemical exergy of hydrogen). Furthermore, recycling anthropogenic waste, including waste heat, waste plastic materials, waste biomass and sewage waters, shows also good potential as a sustainable option for hydrogen production. Biomass conversion to hydrogen is found as potentially the most efficient amongst all studied options in this paper with up to 70% energy efficiency and 65% exergy efficiency.     

A review on process modeling and design of biohydrogen

The current energy supply depends on fossil fuels which have increased carbon dioxide emissions leading to global warming and depleted non-renewable fossil fuels resources. Hydrogen (H₂) fuel could be an eco-friendly alternative since H₂ consumption only produces water. However, the overall impacts of the H₂ economy depend on feedstock types, production technologies, and process routes. The existing process technologies for H₂ production used fossil fuels encounter the escalation of fossil fuel prices and long-term sustainability challenges. Therefore, biohydrogen production from renewable resources like biomass wastes and wastewaters has become the focal development of a sustainable global energy supply. Different from other biohydrogen production studies, this paper emphasizes biohydrogen fermentation processes using different renewable sources and microorganisms. Moreover, it gives an overview of the latest advancing research in different biohydrogen process designs, modeling, and optimization. It also presents the biohydrogen production routes and kinetic modeling for biohydrogenation.     

Steady-state and dynamic modeling of biohydrogen production in an integrated biohydrogen reactor clarifier system

Steady-state operational data from the integrated biohydrogen reactor clarifier system (IBRCS) during anaerobic treatment of glucose-based synthetic wastewater at HRT of 8 h and SRT ranging from 26 to 50 h and organic loading rates of 6.5–206 gCOD/L-d were used to calibrate and verify a process model of the system developed using BioWin. The model accurately predicted biomass concentrations in both the bioreactor and the clarifier supernatant with average percentage errors (APEs) of 4.6% and 10%, respectively. Hydrogen production rates and hydrogen yields predicted by the model were in close agreement with the observed experimental results as reflected by an APE of less than 4%, while the hydrogen content was well correlated with an APE of 10%. The successful modeling culminated in the accurate prediction of soluble metabolites, i.e. volatile fatty acids in the reactor with an APE of 14%. The calibrated model confirmed the advantages of decoupling of the solids retention time (SRT) from the hydraulic retention time (HRT) in biohydrogen production, with the average hydrogen yield decreasing from 3.0 mol H₂/mol glucose to 0.8 mol H₂/mol glucose upon elimination of the clarifier. Dynamic modeling showed that the system responds favorably to short-term hydraulic and organic surges, recovering back to the original condition. Furthermore, the dynamic simulation revealed that with a prolonged startup periods of 10 and 30 days, the IBRCS can be operated at an HRT of 4 h and OLR as high as 206 gCOD/L-d without inhibition and/or marked performance deterioration.     

A review of advanced optimization strategies for fermentative biohydrogen production processes

The inability of statistical optimization to represent the dynamic interaction of the biohydrogen process, which is highly non-linear and complicated, has been identified. However, incorporating a data-driven black-box model could overcome the limitations of conventional methods to provide correct responses rapidly and cost-effective modeling. Despite significant reports on the optimization of hydrogen production from fermentation, fewer studies have been made for the case using artificial intelligence algorithms. As a result, critical and extensive analyses of previous works are conducted to develop a general methodological framework for advanced response optimization.     

Photofermentation of malate for biohydrogen production— A modeling approach

A kinetic model for photofermentative biohydrogen production is developed in this study to predict the dynamics of the process. The proposed model contains 17 parameters to describe cell growth, substrate consumption, and hydrogen evolution as well as inhibition of the process by biomass, light intensity, and substrate. Batch experimental results from the literature were used to calibrate and validate the model with malic acid as a model substrate, using Rhodobacter sphaeroides as a model biomass. Temporal hydrogen evolution and cell growth predicted by the proposed model agreed well with the experimentally measured data obtained from four literature reports, with statistically significant correlation coefficients exceeding 0.9. Based on sensitivity analysis performed with the validated model, only six of the 17 parameters were found to be significant. Model simulations indicated that the range of optimal light intensity for maximum hydrogen yield from malate by R. sphaeroides was 150–250 W/m².     

A critical review on limitations and enhancement strategies associated with biohydrogen production

The potential to operate energy efficient and less expensive production methods are important in biohydrogen production. Biological hydrogen production is often constrained by less productivity. However, to obtain industrial level implementation, greater productivity is essential. Researches on various bioreactors configurations and influencing factors were deeply investigated in this regard. The bioreactors operated in batch mode are appropriate for preliminary optimization whereas industrial level execution needs continuous mode. The main objective of this review is to recap the limitations and constraints associated with bioreactor operation and to list out the enhancement approaches that are currently investigated for improved biohydrogen generation. Recent approaches designed towards biohydrogen production enhancement such as substrate pre-treatments, inhibitors removal, bioaugmentation, immobilization, effluent recycling, buffering capacity maintenance, exploitation of by-products etc., are reviewed thoroughly.     

光伏界的一次盛会

中国第七届光伏会议于１０月２４—２６日在杭州举行，来自国家机关、大专院校、研究院所、厂矿企业及我国台湾、香港的光伏界人士２５０余人出席了会议。这次会议规模较大，结合“阳光发电论坛”和“太阳能利用展览会”同时举行，内容丰富、形式多样，深受与会人员的赞赏。浙江省人大、政协、省科技厅、杭州市人大等有关领导同志到会祝贺。国家科技部秘书长石定寰出席了这次会议，作了“中国光伏事业发展的思考”的专题报告。出席这次会议的还有中国可再生能源协会会长朱俊生、中科院和中国工程院严陆光院士、阙端麟院士、汪生院士以及海外…     

Integration of biohydrogen,biomethane and bioelectrochemical systems

Anaerobic bioprocesses such as Anaerobic digestion (AD), fermentative biohydrogen (BioH₂), and Bioelectrochemical system (BES), converting municipal, agro-industrial wastes and crops to energy have attracted accelerating interest. Anaerobic digestion (AD) however, still requires optimisation of conversion efficiency from biomass to methane. Augmenting methane energy production with simultaneous BioH₂ and bioelectrochemical stage(s) would increase process efficiencies while meeting post treatment effluent quality. Pre-treatment of feedstock increase bacterial accessibility to biomass, thus increasing the conversion yield to target product, but an alternative is separating the acidogenic/hydrolytic processes of AD from methanogenesis. Acidogenesis can be combined with BioH₂ production, prior to methanogenesis. Depending on operating conditions and without further treatment after digestion, the methanogenic stage may discharge a digestate with significant organic strength including volatile fatty acids (VFAs). To meet wastewater discharge consents; adequate use of digestates on land; to minimise environmental impact and; enhance recovery of energy, VFAs should be low. Concatenating bioelectrochemical systems (BES) producing hydrogen and/or electricity can facilitate effluent polishing and improved energy efficiency. Various configurations of the BioH₂, methanogenesis and BES are plausible, and should improve the conversion of wet biomass to energy.     

A two-stage modelling and optimization of biohydrogen production from a mixture of agro-municipal waste

A two-stage modelling and optimization of biohydrogen production is reported. A mixture design was used to determine the optimum proportions of bean husk (BH), corn stalk (CS), and organic fraction of solid municipal waste (OFSMW). The optimum operational setpoints for substrate concentration, pH, temperature and hydraulic retention time (HRT) were further investigated using the box-behnken design. The quadratic polynomial model from the mixture design had a coefficient of determination (R²) of 0.9427 and the optimized mixtures were in the ratio of OFSMW:BH:CS = 30:0:0 and OFSMW:BH:CS = 15:15:0 with yields of 56.47 ml H₂/g TVS and 41.16 ml H₂/g TVS respectively. Optimization on physico-chemical process parameters on the improved substrate gave the setpoints of 40.45 g/l, 7.9, 30.29 °C, 86.28 h for substrate concentration, pH, temperature and HRT respectively having a predicted H₂ yield of 57.73 ml H₂/g TVS. Model validation gave 58.62 ml H₂/g TVS, thus an improvement of 3.8% on the optimized mixture. Biohydrogen production can be significantly enhanced by a suitable mixture of agro-municipal waste and operational optimal setpoints.     

Market and patent analysis of commercializing biohydrogen technology

In the face of world-wide energy price fluctuation, energy supply security, and the energy crisis, it becomes an urgent issue to search for alternative methods for energy generation and to close the gap between the supply and demand of global energy. The current method of energy supply in Taiwan is through a centralized electronic power system, which is generated by a few large electronic power plants. Hydrogen fuel cell (HFC) has a characteristic of de-centralized electronic power supply system, which provides electronic power more reliably, efficiently and economically. Based on the output of Taiwan’s sewage, sludge, kitchen waste and biohydrogen technology, the preliminary market for biohydrogen fuel cell (BHFC) is positioning itself toward the supply of public electronic power within the housing communities. Based on the patent analysis of BHFC, this study finds that Taiwan pays more attention to the front-end manufacturing of raw materials and emphasizes the development of biohydrogen technology, while America and Japan mainly pay more attentions to rear-end product application and emphasize the application of hydrogen and fuel cells by integrating industrial opinions. Based on the market analysis of BHFC, this study finds that the product attributes, consumers’ characteristics and external variables strongly influence consumer’s purchase intention of biohydrogen technology products.     

中国太阳能向外启示录(1)

世上本没有路,走的人多了,也便成了路。——鲁迅序言太阳能作为一种清洁、环保的新能源,在世界范围内越来越受到重视,但产业化的过程却发展     

Strategies for improvement of biohydrogen production from organic-rich wastewater: A review

Biohydrogen can be produced from organic wastewater but the process is limited by low production yields. The aim of this review is to summarize the production strategies which are recently researched for enhancing biohydrogen yield and productivity from organic wastewater. The survey of published work indicates that the dark hydrogen fermentation is the most promising production mode. Current strategies geared towards improving biohydrogen production include: microbial culture immobilization, bioreactor modifications, the optimization of process conditions (temperature, pH, OLR and HRT), culture selection and enrichments, substrate choice, and the metabolic engineering of biohydrogen specialists. Comparative analysis of energy recovery from anaerobic digestion using vinasse-related substrates indicates that the production of methane has a higher energy yield than production of hydrogen. A sequential combination of biohydrogen and biomethanation production phases has the potential for even higher bioenergy recovery from organic wastewater.     

A patent analysis on advanced biohydrogen technology development and commercialisation: Scope and competitiveness

The need of developing renewable energy to reduce the impact on the global environment and climate change of the increasing industrial development has fostered the use of biological processes to produce biofuel from biohydrogen. The present work made a patent analysis of advanced hydrogen production techniques comparing it with similar prior art in China, Japan, the Republic of Korea, the European Union and the United States (U.S.) The aims were to find the scope, competitiveness of prior art, as well as the technology trend on biohydrogen production methods. The patents value was assessed its geographic scope and competitiveness indicators such as green image, low cost, energy efficiency and equipment design. It was found that most of the hydrogen production methods and associated technologies are developed by academic institutions, however their patents are reduced to a local level, and few are patented at international level, which reduces their competitiveness. The China (P.R.C.) is the biggest patent contributor worldwide in terms of hydrogen production methods by academic institutions. Japan is a huge patent contributor, in terms of methods aiming rear-end products application of hydrogen by private companies. The biggest amount of prior art found that the most popular methods of pre-treatment and dark fermentation produced coincide with the time of energetic crisis and the green movement to find alternative fuels. Finally, patent analysis of this study can help to discern the current technology trend and to develop the next generation of biohydrogen processes and associated technologies.     

中国太阳能向外启示录(2)

全面整合:国际化并不只是占有国际市场太阳雨在国际市场开拓方面取得了初步的成功,也许许多人认为这就是太阳雨所谓的国际化,这就是太阳雨作为中国太阳能热水器产业国际化示范的看点。其实,这正是笔者所要着重说明的。太阳雨的国际化绝不是或绝不仅仅是其在国际市场的表现,而是在于其在"市场、技术、人才、资金、信息、管理、思维"等等诸多     

Impact of pretreatment on food waste for biohydrogen production: A review

Food waste (FW) can be utilized as a raw material to produce energy such as hydrogen via fermentation, which is a more attractive and environmentally friendly approach compared to incineration and land-filling. Food waste must be pretreated before being used in various biological processes. The choice of the pretreatment method usually depends on the composition of the food waste. Therefore, various pretreatment methods generally employed to treat FW, including physical, physiochemical, chemical and biological pretreatments, are summarized in this review. The different pretreatment methods are compared in terms of their efficiency and biohydrogen yield. Additionally, the energy efficiencies of the various pretreatment methods are compared, thereby leading to the selection of the most efficient pretreatment method.     

Mathematical model of biohydrogen production in microbial electrolysis cell: A review

Microbial electrolysis cell (MEC) is a promising reactor. However, currently, the reactor cannot be adapted for industrial-scale biohydrogen production. Nevertheless, this drawback can be overcome by modeling studies based on mathematical equations. The limitation of analytical instrumentation to record the non-linearity of the dynamic behavior for biohydrogen processes in an MEC has led to the introduction of computational approach that has the potential to reduce time constraints and optimize experimental costs. Reviews of comparative studies on bioelectrochemical models are widely reported, but there is less emphasis on the MEC model. Therefore, in this paper, a comprehensive review of the MEC mathematical model will be further discussed. The classification of the model with respect to the assumptions, model improvement, and extensive studies based on the model application will be critically analyzed to establish a methodology algorithm flow chart as a guideline for future implementation.     

The early history of Wairakei (with brief notes on some unforeseen outcomes)

In the 40 years prior to commissioning the first stage of Wairakei, the use of natural heat for power production had been suggested on several occasions. The first was in 1918, a bare 2 years after Larderello No. 1 Station was commissioned. However, although one of these suggestions was closely examined, none came to fruition because alternative sources of energy were considered sufficient to meet needs for the foreseeable future. Over the 1940s there was a growing realization that the situation was changing. This came to a head at the end of the decade when the unhappy state of the electricity supply system resulted in Government, among other measures, agreeing to investigate the potential of the geothermal resources of the country. The first investigation wells were drilled in 1950. In spite of the initial difficulties following the war years, by 1953, results were sufficient to justify the installation of a 20 MW power plant. At this point, the proposal to use geothermal energy in the production of heavy water was introduced. However, after a substantial effort had been made towards a combined project, the heavy water proposal had to be dropped and Wairakei Stage I was completed as a stand-alone power station of 69 MW installed capacity. While this, in effect, marks the coming of age of geothermal power development in New Zealand, the effort did not stop there, Wairakei's generation capacity was increased, other New Zealand fields were investigated and, in due course, developed and the flow on effects extended to other countries. Fifty years on, the full outcome of their early endeavors would have gratified but probably not surprised the men who overcame those initial difficulties to drill the first wells.