Economic impact of performances degradation on the competitiveness of energy storage technologies – Part 2: Application on an example of PV production guarantee

In this paper, the newly developed techno-economic assessment platform Odyssey introduced in Part 1 of this two-part series of papers is applied to an application example: the call for tenders from the French Energy Regulation Commission on PV installations greater than 250 kWp. In this context, two storage systems are studied: a bank of lead-acid batteries and a PEM hydrogen chain (PEM electrolyzer, H₂/O₂ PEM fuel-cell, H₂ and O₂ storages under pressure at 30 bars). The objective pursued in the study of this application case is to assess the economic value of these two energy storage technologies and to focus on different influencing factors. Therefore, in the context of this application case, it is shown how a suitable control strategy can considerably help in improving economic results. The influence of the reference meteorological year is also investigated showing that the variations of economic indicators between two different years are greater than the variation of the annual insolation. Furthermore, the investigation on the influence of the simulation time step shows that the use of large time step (30 min, 1 h) may lead to unsuitable sizing and inaccurate estimations of economic performances. Finally systems sizing have been optimized considering different aging modeling which has shown that the influence of aging on the optimal sizing may be important.     

Biodiesel resources and production technologies – A review

The environmental concern and availability of fuels are greatly affecting the trends of fuels for transportation vehicles. Biodiesel is one of the options as alternative transport fuel. This can be produced from straight vegetable oils (SVOs), oils extracted from various plant species and animal fats. Amongst many resources, availability and cost economy are the major factors affecting the large scale production of the biodiesels. The transesterification is one of the production processes for biodiesel, but incomplete esterification of all fatty acids in the starting material, lengthy purification methods such as water washing, relatively long reaction times, contamination and separation difficulties associated with co-production of glycerol and saponification of the starting material under certain reaction conditions are still being major challenges in the biodiesel production. Technological advancement and enhanced production methods are the demand of present time for large scale and sustainable production of biodiesel. In the present paper, comprehensive review on its production process, feed stock and its applications have been made. From many case studies it was concluded that engine performance with B20 biodiesel blends, and mineral diesel were found comparable.     

Economic impact of performances degradation on the competitiveness of energy storage technologies – Part 1: Introduction to the simulation-optimization platform ODYSSEY and elements of validation on a PV-hydrogen hybrid system

In this paper, a newly developed assessment platform Odyssey is introduced. This platform is dedicated to perform comprehensive techno-economic assessments of energy systems comprising renewable energy sources and energy storage units. The major strengths of this platform are described and it is then illustrated on an application example with the objective to provide elements of validation of the platform. This application case is related to the electrical energy supply of a weather station by the mean of a PV-hydrogen hybrid energy system combining PV modules and a hydrogen chain. Experimental results obtained on the fuel cell and electrolyser systems are confronted to simulation results.     

Hydrogen storage of the Mg–C composites

The effect of different kinds of carbon on the hydrogen sorption kinetics by magnesium–carbon composites was analyzed. To prepare magnesium-based composites by ball milling, graphite and carbon nanomaterials (hereinafter CNM) obtained by the electroexplosion technique were used. Phase composition and structure state of the as-milled and hydrogenated magnesium–carbon and magnesium–nickel–carbon composites have been investigated. It was found the crystallite size in the Mg–CNM composite is smaller in comparison with the magnesium–graphite and magnesium–graphite–nickel mixtures. The CNM additives to magnesium essentially improve the hydrogen sorption kinetics. It results in a reduction of hydrogen sorption temperature. The noticeable hydrogen absorption took place already at a temperature of 363 K. The hydrogen capacity was about 5 wt% for magnesium ball milled with CNM additives.     

Levelized cost of storage — Introducing novel metrics

The increasing share of variable renewable generation capacity leads to a growing interest in electricity storage technologies and a summarizing cost metric to analyze the economic viability of such electricity storage units. For conventional generation technologies, the levelized cost of electricity (LCOE) is a well-known metric. In the context of electricity storage however, such LCOE-like metrics are only limitedly applicable as the finite energy storage capacity can limit the charge and discharge scheduling decisions of the storage operator. In addition, the “fuel”, i.e., charged electricity, and “generated electricity”, i.e., discharged electricity, is one and the same commodity which provides the opportunity to use an adapted levelized cost metric. This work analyzes three different levelized cost metrics and their application to electricity storage units used for electric energy arbitrage. The strengths and shortcomings of these storage cost metrics are analyzed in order to determine how they can be applied correctly. This analysis results in the following recommendations. First, it is recommended to use a levelized cost metric in combination with an analysis of a representative price profile upon which the storage operator will act. This allows a more accurate estimation of the number of charging and discharging hours and the associated charging cost and discharging revenue, given the energy storage capacity constraints of the storage unit. Second, when a number of different representative price profiles, hence with different charging costs, is available, it is recommended to use a cost metric which is independent of the charging cost as this single metric can be compared to each price profile, thereby facilitating the interpretation of the results. The results and conclusions from this work provide a framework on how to use levelized cost metrics in the context of electricity storage. Such metrics may help policy makers and investors in prioritizing energy storage investment decisions.     

Hydrogen storage properties of Mg–Ni–C system hydrogen storage materials prepared by hydriding combustion synthesis and mechanical milling

Mg–Ni–C composite hydrogen storage materials were prepared by first ball milling the powder mixtures of carbon aerogel and nano-Ni, and then mixed with magnesium powder followed by hydriding combustion synthesis (HCS). The HCS product was further treated by mechanical milling for 10 h. The effect of Ni/C ratio on the structures and hydrogen absorption/desorption properties of the materials were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure–composition–temperature (PCT) measurements. It is found that 90Mg–6Ni–4C system shows the best hydriding/dehydriding properties, which absorbs hydrogen at a saturated capacity of 5.23 wt.% within 68 s at 373 K and desorbs 3.74 wt.% hydrogen within 1800 s at 523 K. Moreover, the dehydriding onset temperature of the system is 430 K, which is 45 K lower than that of 90Mg–10Ni system or 95 K lower than that of 90Mg–10C system. The improved hydriding/dehydriding properties are related greatly to the Ni/C ratio and the structures of the composite systems.     

Hydrogen storage in thin film metal hydride—a review

During the last decade hydrogen has attracted world wide interest as a secondary energy carrier resulting in a lot of research work on its production, storage and use. The incorporation of hydrogen into thin film form discussed in this article is a relatively new field of research. The main advantages of thin film metal hydrides are that these provide large surface area with fast charging discharging rate for hydrogen, pulverization is slower, both critical pressure and critical temperature are significantly lower, better heat transfer arrangements, protective surface coating could be done to stop poisoning by oxygen and activation of thin film hydrides is possible by coating with a layer of catalytic material.     

Ternary compounds in the magnesium–titanium hydrogen storage system

Mg–Ti–H samples were mechano-chemically synthesized by ball milling in argon atmosphere or under elevated hydrogen pressure. The detailed reaction mechanism during hydrogen release and uptake during continuous cycling was investigated by in-situ synchrotron radiation powder X-ray diffraction (SR-PXD) experiments. The thermal behaviour of the samples and hydrogen desorption properties were examined by simultaneous thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and mass spectrometry (MS) measurements. A ternary Ti–Mg–H compound with a fcc lattice form during mechano-chemical sample preparation in hydrogen atmosphere using metal powders, but not using metal hydrides as reactants. The amount of β-MgH₂ increases during the first hydrogen absorption cycle at 300 °C at the expense of the high-pressure polymorph, γ-MgH₂ and the amount of β-MgH₂ remain constant during the following hydrogenations. This study reveals that the ternary compound tends to absorb increasing amounts of magnesium in the dehydrogenated state during cycling. A strong coupling between the amounts of magnesium in the ternary Ti–Mg–H phase and the formation of magnesium and magnesium hydride during hydrogen release and uptake at 300 °C is observed. The composition and the amount of the Ti–Mg–H phase appear to be similar in the hydrogenated state. Fast absorption–desorption kinetics at 300 °C and lower onset temperatures for hydrogen release is observed for all investigated samples (lowest onset temperature of desorption T_on = 217 °C).     

A synthetical evaluation of developing low-carbonized coal-fired power technologies in China

This study is attempted to analyze the integrated effects of low-carbonized developments for Chinese coal-fired power industry in two cases by extending a hybrid energy-economic model. The first case is energy efficiency improvement without CCS introduction. The second case is direct carbon removal with CCS technology, while coal controlling policy scenario is set as a baseline for comparison. Here oxy-fuel combustion has been selected as the only carbon capture technology due to its great potential in commercialization. Then the ecological co-benefits, environmental benefits, macroeconomic impacts and water saving effects of CO₂ abatement from Chinese coal-fired power industry are analyzed. Simulation results show that energy saving and coal controlling policy can create huge ecological, environmental and water saving benefits. However, coal controlling policy also will cause great macroeconomic losses. But due to extra energy consumption, the large-scale commercialization of oxy-fuel CCS technology if without CO₂ reuse will cause certain decrease of GDP growth rate and increase water consumption in China. Only when combined with resource usage of the captured CO₂, oxy-fuel CCS introduction in China can have some practical application value.     

Hydrogen storage properties of Nb–Hf–Ni ternary alloys

The hydrogen storage properties of Nb_xHf_(1−x)/2Ni_(1−x)/2 (x = 15.6, 40) alloys were investigated with respect to their hydrogen absorption/desorption, thermodynamic, and dynamic characteristics. The PCT curves show that all the specimens can absorb hydrogen at 303 K, 373 K, 423 K, 473 K, 523 K, 573 K, and 673 K, but they couldn't desorb hydrogen below 373 K. The maximum hydrogen absorption capacity reaches 1.23 wt.% for Nb_15.6Hf_42.2Ni_42.2 and 1.48 wt.% for Nb₄₀Hf₃₀Ni₃₀ at 303 K at a pressure of 3 MPa. When the temperature was increased, the hydrogen absorption capacities significantly decreased. However, the hydrogen equilibrium pressure increased. When the temperature exceeded 523 K, the hydrogen equilibrium pressure disappeared. When niobium content was increased, the kinetic properties of hydrogen absorption/desorption improved. The results from the microstructure analysis show that both alloys consist of the BCC Nb-based solid solution phase, the B_f-HfNi intermetallic phase, and the eutectic phase {B_f-HfNi + BCC Nb-based solid solution}. When the Nb content was increased, the volume fraction and Nb content in the Nb-based solid solution phase increased. Thus, the improved kinetics is related to the increase in the primary BCC Nb-based solid solution in the Nb₄₀Hf₃₀Ni₃₀ alloy. The kinetic mechanisms of hydrogen absorption/desorption in these two alloys are found to obey the chemical reaction mechanism at all temperatures tested.     

Does electricity price matter for innovation in renewable energy technologies in China?

Though the development of renewable energy is rapid, innovation in renewable energy technologies is relatively weak due to the late commencement of renewable energy in China. In addition, renewable energy is mainly introduced into the supply mix of electricity generation, which increases the costs of electricity generation. Higher electricity price will make renewable energy more competitive and call forth renewable energy technological innovation. Based on FMOLS and DOLS models, as well as PMG model, this paper investigates the induced long and short run effects of electricity price, funding support, and economic growth on innovation in renewable energy technologies at the provincial level in China during the period 2006–2016. The Conclusions drawn were: (1) R&D expenditure and economic growth have positive impacts on innovation in renewable energy technologies in the long and short run; (2) Electricity price only has a long run effect on patenting in renewable energy technologies; (3) In the long run, a 1% increase in electricity price can lead to a 0.7825%–1.0952% increase in the patent counts of renewable energy technologies; (4) Electricity pricing system in China does not play any role in driving renewable energy technological innovation in the short run.     

New La–Fe–B ternary system hydrogen storage alloys

The new La₈Fe₂₈B₂₄-, La₁₅Fe₇₇B₈- and La₁₇Fe₇₆B₇-type alloys have multiphase structures including LaNi₅, La₃Ni₁₃B₂ and (Fe, Ni) phases. The amount of La₃Ni₁₃B₂ phase increased and that of (Fe, Ni) phase decreased with an increasing La/(Fe + B) atomic ratio. The measurement of P–C–I curves revealed that the maximum hydrogen capacity exceeded 1.12 wt% at 313 K in the pressure range of 10⁻³ MPa–2.0 MPa. The alloys exhibited good absorption/desorption kinetics at room temperature, and electrochemical experiments showed that all of the alloy electrodes exhibited good activation characteristics, high-rate dischargeability (HRD) and low-temperature (233 K) dischargeability (LTD).     

Self-ignition combustion synthesis of TiFe1−xMnx hydrogen storage alloy

The paper describes the self-ignition combustion synthesis (SICS) of the hydrogen storage alloy TiFe_1?xMn_x (X = 0, 0.1, 0.2, 0.3, and 0.5) in a hydrogen atmosphere, where the hydrogenation properties of the products are mainly examined. In the experiments, the well-mixed powders of Ti, Fe, and Mn in the molar ratio of 1:1-X:X were uniformly heated up to 1473 K, and then were cooled naturally in pressurized hydrogen at 0.9 MPa. All products were successfully synthesized by utilizing the exothermic reaction, which occurred at around 1358 K. The XRD analysis showed that SICS generated TiFe_1?xMn_x in the range of X value from 0 to 0.3. All SICSed products absorbed hydrogen smoothly at 298 K at an initial pressure of 4.1 MPa. Most significantly, TiFe_0.8Mn_0.2 improved the dual plateau property. The results revealed that SICS was quite effective for producing the hydrogen storage alloy TiFe_1?xMn_x.     

Hierarchical nanostructured Au–SnO2 for enhanced energy storage performance

Electrode materials with high energy and power density are mostly essential to overcome traditional fossil fuel use. Herein, we demonstrate the synthesis of Au decorated self-assembled SnO₂ nanoflowers consisting of nanorods by a cost-effective and eco-friendly solvothermal process. The as-synthesized SnO₂ based materials were employed as electrode material in the energy storage system, which delivered considerably high specific capacitance of 634.3 F/g at a current density of 1 A/g. The electrode material also exhibits excellent cycle stability of 83.52% after 4000 galvanostatic charge–discharge (GCD) cycles. The high specific capacitive value is attributed to the hybrid performance of battery and supercapacitor, more active sites, and higher surface area. A solid state asymmetry device was fabricated using Au–SnO₂ and activated carbon (AC) as positive and negative electrodes. The asymmetry device shows an excellent energy density of 168.9 Wh/kg at a power density of 1 kW/kg with an applied current density of 1 A/g.     

Degradation mechanisms of Ti–V-based multiphase hydrogen storage alloy electrode

The degradation mechanisms of the Ti–V-based multiphase hydrogen storage electrode alloy (Ti_0.8Zr_0.2)(V_0.533Mn_0.107Cr_0.16Ni_0.2)₂ during electrochemical cycling in alkaline electrolyte have been studied systematically by using XRD, SEM, XPS, AES and EIS measurements. The results show that the irreversible hydrogen absorbed in the alloy increases with cycling. The pulverization and oxidation/corrosion of the alloy during cycling are two main factors responsible for the fast degradation of the electrode. It was found that a passive Ti oxide film formed on the alloy surface, leading to an increase in charge transfer resistance on the alloy surface and a decrease in exchange current density I₀.     

Superior electrochemical hydrogen storage properties of binary Mg–Y thin films

Mg–Y thin films capped with Pd have been prepared by direct current magnetron co-sputtering system. It is found that Mg alloyed with Y in film state forms ultrafine nanocrystalline intermetallic compounds. The structure together with the catalytic effect of Y gives rise to a high electrochemical hydrogen storage capacities and superior activation properties. It is worthy to note that Mg₇₈Y₂₂ film achieves a high discharge capacity of 1590 mAh g⁻¹ without requiring activation process. Moreover, Mg alloyed with Y effectively improves the cyclic stability of Mg-based films ascribing to the anti-corrosion role of Y. For Mg₃₇Y₆₃ film, more than 92％ of the maximum discharge capacity can be maintained after 100 charge–discharge cycles.     

Study of hydrogen production and storage based on aluminum–water reaction

The rate and yield of hydrogen production from the reaction between activated aluminum and water has been investigated. The effect of different parameters such as water–aluminum ratio, water temperature and aluminum particle size and shape was studied experimentally. The aluminum activation method developed in-house involves 1%–2.5% of lithium-based activator which is diffused into the aluminum particles, enabling sustained reaction with tap water or sea water at room temperature. Hydrogen production rates in the range of 200–600 ml/min/g Al, at a yield of about 90%, depending on operating parameters, were demonstrated. The work further studied the application in proton exchange membrane (PEM) fuel cells in order to generate green electric energy, demonstrating theoretical specific electric energy storage that can exceed batteries by 10–20 folds.     

The potential of transition metal–methylidynes as high-capacity hydrogen storage media

With respect to density functional predictions, TM–methylidynes (TM = Sc, Ti, V, and Cr) bind high-density hydrogen at ambient conditions. TM–methylidyne complexes can adsorb up to seven hydrogen molecules. The predicted maximal retrievable hydrogen storage density is 16.7 wt% for ScCH, a record high value so far, larger than the 16.0 wt% for TiCH, 13.2 wt% for VCH, and 13.0 wt% for CrCH. Dimerization and oligomerization of scandium–methylidyne lower the hydrogen storage capacity to 9.2 wt% for the dimer and to 7.9 wt% for the hexamer. These predictions provide useful guidance for designing novel hydrogen storage materials with optimal gravimetry and kinetics and for devising possible schemes by which the hydrogen/host material interactions can be manipulated.