斜生栅藻产微生物油脂的研究

微藻类微生物可以产生油脂,油脂可以转化为生物柴油。以废蔗渣中的含碳有机物作为原料培养斜生栅藻,通过对比实验和分析斜生栅藻的生长量、产油量、产油率,得出斜生栅藻产油率最高的水解液含量,通过正交实验,得出产油率最高的环境条件。实验结果表明,pH值对斜生栅藻产油的影响最大,当pH值为7.0、光照时长为18.0 h、氮含量100.0 mmol/L时斜生栅藻的产油脂率达到最大,为44.35%。     

低氮胁迫对两种魏氏藻生长和油脂积累的影响

为了评价低氮胁迫对真眼点藻纲的两株高产油微藻(斧形魏氏藻和点状魏氏藻)的生长和油脂积累的影响,实验设计中将原改良BG-11培养基中的硝酸钠浓度降低为3.6 mmol/L(0.3 g/L)。结果表明:在此浓度下斧形魏氏藻和点状魏氏藻的最高生物量分别为8.21 g/L和9.07 g/L;两者的总脂、中性脂和总脂肪酸含量(占干重)都随着培养时间的延长而不断增加,培养至第18天时分别达到56.4%,64.7%;54%,63.3%;43.5%,45.5%。这两种微藻的主要脂肪酸都含有豆蔻酸、棕榈酸、棕榈油酸、油酸、亚油酸、花生四烯酸和二十碳五烯酸,均适合于生物柴油的生产。它们的总脂、中性脂和总脂肪酸的单位体积产率分别为0.257 g/(L·d),0.326 g/(L·d);0.246 g/(L·d),0.319 g/(L·d)和0.198 g/(L·d),0.229 g/(L·d)。这说明两种微藻在低氮胁迫下都能够获得较高的油脂产率。     

光合产氢细菌优势菌群富集及其产氢实验研究

利用特殊培养基从光照充裕、有机质含量高的猪场粪便排放处的污泥中富集培养光合细菌混合产氢菌群,对该混合菌群的产氢培养基进行优化,并研究混合菌群的产氢特性。实验结果表明,此菌群的最佳产氢培养基配方为:氯化铵0.4g/L,氯化镁0.2g/L,酵母膏0.1g/L,磷酸氢二钾0.5g/L,氯化钠2.0g/L,谷氨酸钠3.5g/L。此菌群以1%的葡萄糖为基质时,产氢时间长达204h,最大产氢量为3.41L/L,最大产氢速率为44.17mL/(L.h),最高氢气含量为46.73%,具有工业化应用价值。     

光强与氮源对绿球藻GN38生长和油脂积累的影响

光强与氮源是影响微藻生长与物质积累的重要因子,文章研究了光强、氮源、氮源浓度对一株自然条件下分离的绿球藻GN38的生长和油脂积累的影响。实验通过在不同光照强度(179μmol/m2·s-1和84μmol/m2·s-1)条件下,分别以具浓度梯度(1N,1/3N,1/5N)的NaNO3和CO(NH2)2为氮源培养绿球藻,获得了GN38生长与产油的较佳条件。结果表明,较高光强能促进GN38生长和总脂积累;CO(NH2)2有利于GN38积累油脂;不同氮源均表现出氮源浓度与生物量成正比,无氮组除外;179μmol/m2·s-1光强、1/5N时GN38的总脂含量最高。综合考虑,产油微藻GN38的最佳培养条件为179μmol/m2·s-1光强和0.528 g/L CO(NH2)2,在此条件下干重达到6.7g/L,总脂含量为38%,总脂产量为2.54 g/L,脂肪酸成分中C16和C18含量高达95.15%。实验为该藻的后续深入研究及产业化培养奠定了基础。     

活性炭脱毒甘蔗渣稀酸水解液用于酵母油脂的合成

在利用木质纤维素稀酸水解液发酵生产微生物油脂的过程中,水解液须经过脱毒处理,以除去其中抑制菌体生长的有毒物质.采用活性炭对甘蔗渣稀酸水解液进行吸附脱毒,通过响应面中心复合设计(CCD)试验,研究了不同因素对活性炭脱毒的影响,并优化了活性炭脱毒的条件.在活性炭用量为3%(质量分数),温度为80℃,pH=2的条件下脱毒50 min,可以除去超过90%的酸溶木素及木素降解产物.用Ca(OH)2中和水解液后作为碳源.在限氮条件下采用圆红冬孢酵母菌(Rhodosporidium tomloides AS 2.1389)发酵生产油脂.结果表明,脱毒后的水解液可以很好地用于菌体生物量合成,其油脂含量为32.99%,油脂得率系数(油脂/糖)为12.48 g/100g.     

硅藻生长优化富集油脂的促进机理

为了促进硅藻生长富集油脂并转化制取生物柴油的能力,以纤细角毛藻和新月菱形藻为代表,研究了硅藻生长条件（pH值、氮浓度、硅浓度、收获时间）对其富集油脂的影响规律和促进机理,发现在缺硅缺氮条件下适当延长收获时间能够显著提高油脂含量,纤细角毛藻的油脂含量和产油能力明显高于新月菱形藻。当培养基中硅浓度（Na2SiO3.9H2O）由200 mg/L降低到0、氮浓度（NaNO3）由12.0 mmol/L降低到0.5 mmol/L、收获时间由8 d延长到32 d时,纤细角毛藻的干燥生物质中油脂含量由13.25%提高到31.74%（达到2.4倍）,细胞产油能力达到39.62 mg/L。     

产木聚糖酶菌株的筛选及产酶条件优化

通过透明圈法从土壤中筛选到两株产木聚糖酶菌株CS-1和CS-2,CS-2产木聚糖酶的酶活力优于CS-1。CS-2产木聚糖酶最佳发酵培养条件:碳源(甘蔗渣)3.0 g/ml,氮源(NH4Cl)0.5 g/ml,接种量为10%,250 ml三角瓶装液量50 ml,pH=8.0,温度为55℃,转速为160 r/min,发酵时间为3 d。在此发酵条件下,CS-2产木聚糖酶的酶活力达到7.980 U/ml。     

聚球藻自相发酵产氢研究

研究了培养基的pH值、盐度和氮源等对聚球藻生长及自相发酵产氢的影响。发现聚球藻在弱碱性时(pH=7.5~8)不能正常生长,当pH值高于8.5时藻才能实现富集,当碱性进一步增强到pH值9.5时藻生长状态最佳。收获藻液置于黑暗厌氧条件下利用自身氢酶进行自相发酵产氢,单位干重的产氢量达到22.25mL/g。聚球藻无法适应高盐度环境,在盐度较低情况下(0.154 mmol/L)才能迅速生长,得到自发酵产氢最大值为25.68 mL/g。加入无机氮源能明显提高聚球藻的生长速率及生物质产量,但对随后产氢效果有抑制作用。     

普通小球藻产油性能研究

以普通小球藻(Chlorella vulgaris)为研究对象,考察了培养时间、培养温度、起始p H、不同碳源、氮源以及不同碳氮组合对其生物量和油脂产率的影响。结果表明:当培养温度为28℃、起始p H为8,最优碳氮源分别是浓度为20 g/L的葡萄糖和浓度为1.0 g/L的尿素时,培养15 d收获,普通小球藻油脂产率可达到156.4mg/(L·d),比优化前提高51%,为今后扩大培养小球藻、提高其油脂产率奠定了理论基础。     

戊糖发酵产油酵母菌的筛选及油脂组成分析

从土壤中筛选到一株能够转化戊糖的高产油脂酵母菌株LY17,该菌株在以木糖为唯一碳源的限氮培养基中进行发酵时,菌体油脂含量为35.06%,油脂产量达到4.73 g/L.常规鉴定和26S rDNA D1/D2区域序列分析表明,菌株LY17属于胶红酵母(Rhodotorula mucilaginosa).脂肪酸组成分析结果表明,菌株LY17以木糖为碳源发酵时,菌体内积累的油脂富含饱和及低度不饱和长链脂肪酸,其中油酸、亚油酸和棕榈酸之和占总脂肪酸组成的90%以上,脂肪酸组成分布类似于常见的植物油.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

The Solar Office in context

The goal of sustainability in buildings can only hope to be realised if buildings are designed to both conserve and generate energy. The Solar Office at Doxford International is designed to minimise the use of energy while its external fabric is designed to replace such energy that is used. The recently completed building is now subject of a comprehensive monitoring programme. The programme covers both the performance of the 73 kW_p photovoltaic installation and the environmental conditions within the building as a whole. Hour by hour findings are posted on a dedicated web site. Photovoltaics could have the same impact on building form and layout as the invention of the passenger lift at the end of the last century.     

Hydrogen recovery from the photovoltaic electroflocculation-flotation process for harvesting Chlorella pyrenoidosa microalgae

In this paper, an integrated process using photovoltaic power to harvest microalgae by electro-flocculation (EF) and hydrogen recovery is presented. It is mainly favorable in regions with high solar radiation. The electro-flocculation efficiency (EFE) of Chlorella pyrenoidosa microalgae was investigated using various types of electrodes (aluminum, iron, zinc, copper and a non-sacrificial electrode of carbon). The best results regarding the EFE, and biomass contamination were achieved with aluminum and carbon electrodes where the electrical energy demand of the process for harvesting 1 kg of algae biomass was 0.28 and 0.34 kWh, respectively, while the energy yield of harvested hydrogen was 0.052 and 0.005 kWh kg^?1, respectively. The highest harvesting efficiency of 95.83 ± 0.87% was obtained with the aluminum electrode.The experimental hydrogen yields obtained were comparable with those calculated from theory. With a low net energy demand, microalgae EF may be a useful and low-cost technology.     

Electrochemical behavior of Mg–Li,Mg–Li–Al and Mg–Li–Al–Ce in sodium chloride solution

Mg–Li, Mg–Li–Al and Mg–Li–Al–Ce alloys were prepared and their electrochemical behavior in 0.7 M NaCl solutions was investigated by means of potentiodynamic polarization, potentiostatic current–time and electrochemical impedance spectroscopy measurements as well as by scanning electron microscopy examination. The effect of gallium oxide as an electrolyte additive on the potentiostatic discharge performance of these magnesium alloys was studied. The discharge activities and utilization efficiencies of these alloys increase in the order: Mg–Li < Mg–Li–Al < Mg–Li–Al–Ce, both in the absence and presence of Ga₂O₃. These alloys are more active than commercial magnesium alloy AZ31. The addition of Ga₂O₃ into NaCl electrolyte solution improved the discharging currents of the alloys by more than 4%, and enhanced the utilization efficiencies of the alloys by more than 6%. It also shortened the transition time for the discharge current to reach to a steady value. Electrochemical impedance spectroscopy measurements showed that the polarization resistance of the alloys decreases in the following order: Mg–Li > Mg–Li–Al > Mg–Li–Al–Ce. Mg–Li–Al–Ce exhibited the best performance in term of activity, utilization efficiency and activation time.     

Temperature dependence of the enthalpy of formation of metal hydrides characterized by an excess volume

A universal framework to calculate the temperature dependence of the excess enthalpy present in regions characterized by an excess volume is calculated for metals and metal hydrides. At high temperatures, the different contributions from the pressure–volume, heat capacity, entropy and work associated with the thermal expansion are studied separately and their magnitudes and signs are compared. It is found that the pressure–volume contribution opposes and dominates the other three contributions at both high temperature and excess volume, and it is thus found that this contribution becomes the leading temperature dependent contribution to the enthalpy of a material. The conditions under which a temperature change will reduce the enthalpy of formation of metal hydrides are also given and the Mg/MgH₂ system is studied as an example. Excluding the heat capacity contribution, an increase in temperature tends to offset the effect of the excess volume on the enthalpy of formation. It is also demonstrated that the impact of temperature will be more favorable to a reduction of the enthalpy of formation if a large fraction of the metal hydride is in a state of small excess volume compared to a small fraction of the hydride in a state of high excess volume.     

The effect of electrode infiltration on the performance of tubular solid oxide fuel cells under electrolysis and fuel cell modes

The electrochemical performance of two different anode supported tubular cells (50:50 wt% NiO:YSZ (yttria stabilized zirconia) or 34:66 vol.% Ni:YSZ) as the fuel electrode and YSZ as the electrolyte) under SOFC (solid oxide fuel cell) and SOEC (solid oxide electrolysis cell) modes were studied in this research. LSM (La_0.80Sr_0.20MnO_3−δ) was infiltrated into a thin porous YSZ layer to form the oxygen electrode of both cells and, in addition, SDC (Sm_0.2Ce_0.8O_1.9) was infiltrated into the fuel electrode of one of the cells. The microstructure of the infiltrated fuel cells showed a suitable distribution of fine LSM and SDC particles (50–100 nm) near the interface of electrodes and electrolyte and throughout the bulk of the electrodes. The results show that SDC infiltration not only enhances the electrochemical reaction in SOFC mode but improves the performance even more in SOEC mode. In addition, LSM infiltrated electrodes also boost the SOEC performance in comparison with standard LSM–YSZ composite electrodes, due to the well-dispersed LSM nanoparticles (favouring the electrochemical reactions) within the YSZ porous matrix.     

Tailored solar optics for maximal optical tolerance and concentration

Recently identified fundamental classes of dual-mirror double-tailored nonimaging optics have the potential to satisfy the pragmatic exigencies of concentrator photovoltaics. Via a comprehensive survey of their parameter space, including raytrace verification, we identify champion high-concentration high-efficiency designs that offer unprecedented optical tolerance (i.e., sensitivity to off-axis orientation) - a pivotal figure-of-merit with a basic bound that depends on concentration, exit angle, and effective solar angular radius. For comparison, results for the best corresponding dual-mirror aplanatic concentrators are also presented.