Giant cane (Arundo donax L.) for biogas production: The effect of two ensilage methods on biomass characteristics and biogas potential

Arundo donax L. is a perennial plant that can substitute for traditional energy crops to produce biogas, reducing costs because of its high biogas yield per Ha cultivated and low agronomic and energetic inputs. Nevertheless, Arundo donax biomass needs to be ensiled to be preserved and used. Because no full-scale data exist about A. donax ensilage and the effect of this process on potential biogas production, in this work two different ensiling techniques, i.e. trench and silo-bag ensiling, were performed at full scale, and the processes studied for 200 days. Results obtained indicated that A. donax could be successful ensiled by using the two approaches. Ensilage proceeded by fermentation of organic acids already present in the biomass, i.e. malic and oxalic acids that were degraded, giving volatile fatty acid accumulation. This was different from corn ensiling characterized by starch fermentation to lactic acids. Biological processes determined a loss of the potential biomethane production, namely −20.1% and −7.6% for trench and silo-bag, respectively. Taking into consideration biomethane yield per Ha and ensilage losses, potential biomethane losses of 5000 Nm³ CH₄ Ha⁻¹ for trench silage and of 2000 Nm³ CH₄ Ha⁻¹ for silo bag, were estimated, respectively. Nevertheless, taking into consideration the higher biomass and biomethane yields Ha⁻¹ in comparison with the other energy crops, A. donax still remained more efficient and cheaper than traditional energy crops in producing biogas.     

The response of Arundo donax L. (C3) and Panicum virgatum (C4) to different stresses

In this work, two perennial rhizomatous grasses (Arundo donax L. (giant reed; C₃) and Panicum virgatum L. (switchgrass; C₄)) considered as promising energy crops have been subjected to four different types of stress in two experiments: (i) both species were subjected to four salinity and water stress treatments [well-watered with non-saline solution (WW S−), low-watered with non-saline solution (WS S-), well-watered with saline solution (WW S+) and low-watered with saline solution (WS S+)]; and (ii) both species were subjected to three temperature and light treatments [ambient temperature and light (C), ambient temperature and darkness (AD) and cold temperature and darkness (CD)]. Photosynthetic and physiological parameters as well as biomass production were measured in these plants. It can be hypothesized that a higher photosynthesis rate (A_sat) was be observed in switchgrass as a consequence of its C₄ metabolic pathway. However, our results indicated a similar A_sat at the beginning of the experiment for both species. This could be due to switchgrass being an NAD-ME C₄ type whereas giant reed has been reported as a C₃ species with a high photosynthetic rate. We showed that switchgrass seems to be more resistant to stresses such as water stress, salinity and cold than giant reed in our greenhouse conditions.     

Long-term water balance and sustainable production of Miscanthus energy crops in the Loess Plateau of China

Sustainable production of second-generation energy crops on marginal land holds a great potential for renewable energy development. Because a vast area of marginal land is located in the arid and semiarid regions of the world, water shortage is the most serious environmental limitation. In this study, we developed a water balance model to address the question of whether Miscanthus energy crops can be sustainably produced in the Loess Plateau of China, a region of more than 60 million hectares particularly abundant in semiarid marginal land. The simulation of 20-year soil water content in bare soil, the winter wheat field, and the Miscanthus field across the Loess Plateau suggested that the long-term production of Miscanthus would not cause water depletion in deep soil. This finding addressed a serious concern that growing high-biomass plants in the Loess Plateau might lead to deep-soil water depletion, which was suggested to be the cause of previous failure of afforestation. Planting Miscanthus was effective in reducing surface runoff and consequently preventing water and soil loss in this heavily eroded region. The model and analyses illustrated where in the Loess Plateau this perennial energy crop could be produced with stable and sufficient yield.     

Power to change: Analysis of household participation in a renewable energy and energy efficiency programme in Central Australia

The Australian government funded a national Solar City program (2008–2013) to support communities to increase adoption of energy efficiency measures and renewable energy technology. One community was Alice Springs, a town with about 9000 households in the geographic centre of Australia. The programme offered a package of support: free energy audits, discounts for the purchase of renewable energy technology and energy efficiency measures, and ongoing information. Households that adopted solar hot water and photovoltaic systems reduced their electricity usage immediately after adoption by 10% and 34% respectively, and this was maintained in the long term. A small rebound effect of 15% was observed in the photovoltaic adopters. It was observed that, on average, households that adopted only energy efficiency measures did not have a significant reduction in their electricity usage over the long term. However, consistent with expectations, this study did show that there was a significant correlation between the number of energy efficiency measures adopted and the greatest household reduction in electricity usage. These contrary results indicate that there are additional factors involved. The connection between the effective use of measures, coincident behavioural change or increased energy awareness and greater energy reduction is discussed.     

Towards a sustainable energy balance: progressive efficiency and the return of energy conservation

We argue that a primary focus on energy efficiency may not be sufficient to slow (and ultimately reverse) the growth in total energy consumption and carbon emissions. Instead, policy makers need to return to an earlier emphasis on “conservation,” with energy efficiency seen as a means rather than an end in itself. We briefly review the concept of “intensive” versus “extensive” variables (i.e., energy efficiency versus energy consumption) and why attention to both consumption and efficiency is essential for effective policy in a carbon- and oil-constrained world with increasingly brittle energy markets. To start, energy indicators and policy evaluation metrics need to reflect energy consumption, as well as efficiency. We introduce the concept of “progressive efficiency,” with the expected or required level of efficiency varying as a function of house size, appliance capacity, or more generally, the scale of energy services. We propose introducing progressive efficiency criteria first in consumer information programs (including appliance labeling categories) and then in voluntary rating and recognition programs such as ENERGY STAR. As acceptance grows, the concept could be extended to utility rebates, tax incentives, and ultimately to mandatory codes and standards. For these and other programs, incorporating criteria for consumption, as well as efficiency, offers a path for energy experts, policymakers, and the public to begin building consensus on energy policies that recognize the limits of resources and global carrying capacity. Ultimately, it is both necessary and, we believe, possible to manage energy consumption, not just efficiency, in order to achieve a sustainable energy balance. Along the way, we may find it possible to shift expectations away from perpetual growth and toward satisfaction with sufficiency.

浙江省建筑与交通领域节能分析

对浙江省建筑领域和交通领域的能源利用及其效率的现状进行了深入的研究,并在此基础上,分析了浙江省建筑和交通这两大领域的节能潜力,并提出了关于节能措施的建议。     

Uncertainty in the learning rates of energy technologies: An experiment in a global multi-regional energy system model

The diffusion of promising energy technologies in the market depends on their future energy production–cost development. When analyzing these technologies in an integrated assessment model using endogenous technological learning, the uncertainty in the assumed learning rates (LRs) plays a crucial role in the production–cost development and model outcomes. This study examines the uncertainty in LRs of some energy technologies under endogenous global learning implementation and presents a floor-cost modeling procedure to systematically regulate the uncertainty in LRs of energy technologies. The article narrates the difficulties of data assimilation, as compatible with mixed integer programming segmentations, and comprehensively presents the causes of uncertainty in LRs. This work is executed using a multi-regional and long-horizon energy system model based on “TIMES” framework. All regions receive an economic advantage to learn in a common domain, and resource-ample regions obtain a marginal advantage for better exploitation of the learning technologies, due to a lower supply-side fuel-cost development. The lowest learning investment associated with the maximum LR mobilizes more deployment of the learning technologies. The uncertainty in LRs has an impact on the diffusion of energy technologies tested, and therefore this study scrutinizes the role of policy support for some of the technologies investigated.     

Promotion of geothermal energy in Switzerland: a recent programme for a long-term task

In 2001, a 10-year programme called “SwissEnergy” was initiated by the Swiss Federal Office of Energy, mainly devoted to a more efficient use of energy, with specific tasks such as energy saving, reduction of CO₂ emissions and a definitive increase in the contribution of renewable energies. The Swiss Geothermal Society (SGS) was therefore given a mandate to promote the application of geothermal energy at a national level. The main objectives of their programme are to develop a sound image for geothermal energy in general, to disseminate information on the various technologies already in use all over the country and to illustrate the future potential of this sector. All entities involved in the energy sector are to be called on to collaborate in the programme, including the Federal Office of Energy, local utility companies and energy agencies, as well as the various networks present in the field of renewable energy (geothermal, sun, wind and biomass). The programme covers all the geothermal resources and technologies available in Switzerland, such as borehole heat exchangers, groundwater wells, foundation piles, thermal springs, deep aquifers and warm tunnel drainage waters. The programme is organised into five activity modules, i.e. Information, Basic and continuous education, Marketing, Quality insurance, and Consulting services. Three Regional Promotion Centres (RPC) have also been set up in the three linguistic regions of Switzerland, one in the German-speaking region, one in the French-speaking region and one in the Italian-speaking region. The staff consists of 13 part-time experts. The strong interest and favourable reception given to all aspects of the Swiss geothermal promotion programme during its first 2 years of activity have confirmed how important it is to disseminate information on energy matters.     

Monthly and seasonal assessment of wind energy characteristics at four monitored locations in Liguria region (Italy)

The aim of this paper is to investigate the monthly and seasonal variation of the wind characteristics in term of wind energy potential using the wind speed data collected between 2002 and 2008 for four meteorological stations in Liguria region, in Northwest of Italy, namely Capo Vado, Casoni, Fontana Fresca and Monte Settepani. The results show that Capo Vado is the best site with a monthly mean wind speed between 2.80 and 9.98 m/s at a height of 10 m and a monthly wind power density between 90.71 and 1177.97 W/m², while the highest energy produced may be reached in December with a value of 3800 MWh. This study may provide information for developing wind energy sites and planning economical wind turbines capacity for the electricity production in Liguria region, as well as an example of how, deepening the analysis at monthly and seasonal scale, the characteristics of the sites might fall in quite different classes of power density.     

Effects of foreign investors on energy firms' innovation: Evidence from a natural experiment in China

Based on a natural experiment of foreign investment access relaxation, this paper investigates impacts of foreign institutional investors (FIIs) on energy firms' innovation. It is still unclear the real effect of FIIs on energy firms' innovation in the literature. We detect a significantly positive relationship between foreign institutional investors and innovation outputs of energy firms using firm-level data. Three possible mechanisms driving our findings are explored. Foreign institutions increase the proportion of R&D expenditures in revenues, limit the scale of related party transactions to improve corporate governance, and widen the pay gap within firms to stimulate the efficiency of human capital. Our main findings are weakened in state-owned companies with high financing constraints. Jointly, our findings offer clear policy implications to emerging markets by identifying the effects of FIIs on energy firms' innovation.     

Achievements and trends of solid oxide fuel cells in clean energy field: a perspective review

The main concerns in the world today, especially in the energy field, are subjected to clean, efficient, and durable sources of energy. These three aspects are the main goals that scientist are paying attention to. However, the various types of energy resources include fossil and sustainable ones, but still some challenges are chasing these kinds from energy conversion, storage, and efficiency. Hence, the most reliable and considered energy resource nowadays is the utilized one which is as highly efficient, clean, and everlasting as possible. So, in this review, an attempt is made to highlight one of the promising types as a clean and efficient energy resource. Solid oxide fuel cell (SOFC) is the most efficient type of the fuel cell types involved with hydrogen and hydrocarbon-based fuels, especially when it works with combined heat and power (CHP). The importance of this type is due to its nature of work as conversion tool from chemical to electrical for generation of power without noise, pollution, and can be safely handled.     

Electric energy storage systems in a market-based economy: Comparison of emerging and traditional technologies

Unlike markets for storable commodities, electricity markets depend on the real-time balance of supply and demand. Although much of the present-day grid operate effectively without storage technologies, cost-effective ways of storing electrical energy can make the grid more efficient and reliable. This work addresses an economic comparison between emerging and traditional Electric Energy Storage (EES) technologies in a competitive electricity market. In order to achieve this goal, an appropriate Self-Scheduling (SS) approach must first be developed for each of them to determine their maximum potential of expected profit among multi-markets such as energy and ancillary service markets. Then, these technologies are economically analyzed using Internal Rate of Return (IRR) index. Finally, the amounts of needed financial supports are determined for choosing the emerging technologies when an investor would like to invest on EES technologies. Among available EES technologies, we consider NaS battery (Natrium Sulfur battery) and pumped-storage plants as emerging and traditional technologies, respectively.     

Assessing complementarity of wind and solar resources for energy production in Italy. A Monte Carlo approach

Wind and solar energy are expected to play a major role in the current decade to help Europe reaching the renewable energy penetration targets fixed by Directive 2009/28/EC. However, it is difficult to predict the actual production profiles of wind and solar energy as they depend heavily on variable meteorological features of solar radiation and wind speed. In an ideal system, wind and solar electricity are both injected in a fast reacting grid instantaneously matching supply and demand. In such a system wind and solar electricity production profiles should complement each other as much as possible in order to minimise the need of storage and additional capacity. In the present paper the complementarity of wind and solar resources is assessed for a test year in Italy.To achieve this goal we employ data at high spatial and temporal resolution data for both solar radiation and wind speed in Italy obtained from running two state of the art models (PVGIS and MINNI). Hourly profiles for solar and wind energy produced are compared in each 4 × 4 km² grid cell in Italy for 2005, and hourly, daily and monthly correlation coefficients are computed in order to assess the local complementarity of the two resources. A Monte Carlo approach is also developed to estimate how large-scale wind and solar energy productions could be potentially involved to complement each other in a scenario with up to 100 production sites across Italy. The results show how local complementarity can be very interesting with monthly correlation coefficients reaching values lower than −0.8 in several areas. Large-scale complementarity is also relevant with nation-wide monthly correlation coefficients showing values between −0.65 and −0.6. These model results indicate that in this sample year of 2005, wind and solar energy potential production have shown complementary time behaviour complementary, favourably supporting their integration in the energy system.     

Optimisation of the regional energy supply network: a multi-objective analysis in the province of Florence (Italy)

This work presents an integrated method for the optimisation of a regional wood-energy supply network. The model is based on a scalar system that comprises a demand point (district heating plants (DHP)) and bio-energy sources (supply basin (SB)), each of which is related to a biomass terminal. The objective of optimisation is based on both technical-logistics and environmental parameters. An SB is defined by the anisotropic weighted Voronoi tessellation methodology. The parameters are then aggregated to a multi-objective analysis that includes the optimisation of variables and compromise programming approach. Results permit the identification of the best supply chain organisation and the determination of the agro-forest energy districts where rural policy and intervention could be applied. The model was tested in the province of Florence (central Italy) to depict efficient scenarios for the fuelling of DHPs.     

Spatial distribution of temperature in the low-temperature geothermal Euganean field (NE Italy): a simulated annealing approach

The spatial distribution of groundwater temperatures in the low-temperature (60–86 °C) geothermal Euganean field of northeastern Italy has been studied using a geostatistical approach. The data set consists of 186 temperatures measured in a fractured limestone reservoir, over an area of 8 km². Investigation of the spatial continuity by means of variographic analysis revealed the presence of anisotropies that are apparently related to the particular geologic structure of the area. After inference of variogram models, a simulated annealing procedure was used to perform conditional simulations of temperature in the domain being studied. These simulations honor the data values and reproduce the spatial continuity inferred from the data. Post-processing of the simulations permits an assessment of temperature uncertainties. Maps of estimated temperatures, interquartile range, and of the probability of exceeding a prescribed 80 °C threshold were also computed. The methodology described could prove useful when siting new wells in a geothermal area.     

Appliance energy labels and consumer heterogeneity: A latent class approach based on a discrete choice experiment in China

Given the growing concerns about environmental protection, a focus on energy label behavior is of particular public interest, as labels can communicate to consumers the sustainability of products. Based on a discrete choice experiment, we measure consumers' awareness and attitudes regarding refrigerators and washing machines. A mixed logit model is specified to quantify the attributes consumers look for when choosing the two electrical appliances. In the latent class model, four classes are observed. The results of the study reveal that the energy label program in China is effective. However, consumers do not always choose the energy efficient appliances, and their failure to do so is often related to an energy efficiency gap. Interestingly, both the largest groups for the refrigerator (33.17%) and washing machine (36.6%) tend to prefer the two electrical appliances with the lowest price. Both are foreign brands, with low energy label and larger overall capacity. Consumers are also willing to pay more for an improved energy grade label on the refrigerator (731.16 yuan) than on the washing machine (424.76 yuan). Suggestions regarding how to increase the probability of consumers choosing energy efficient appliances are also given in this paper.     

An international comparison of energy use in industry: United Kingdom,West Germany,and Italy

The paper presents an investigation on the relation between energy use and economic activity in eight industrial sectors in the United Kingdom, West Germany, and Italy. The approach relies on the analysis of time-series data. In the first section, we point to the role of energy in its interrelationship with the structural characteristics of the national economies. Subsequently, having observed that unit energy requirements vary in the same sector across the three countries, the analysis focuses on possible explanations. The different unit energy consumption pattern, as exhibited by most of the Italian sectors when compared with both the British and the West German ones, is not related to different unit labour and unit capital utilisation patterns. The lack, in the Italian sectors, of a large coal consumption share in the first post-war decade provides an intuitively plausible explanation for the observed unit energy consumption. We test the hypothesis that interfuel substitution alone can account for increased energy productivity. From the results obtained, we deduce that, for a small subset of our sectors, the tested hypothesis turns out to be a meaningful one. In a subsequent section, we analyse and compare the substitution characteristics and the price elasticities of consumption for four fuels. We also take account of the price of labour. Our results support the conclusion that electricity tends to be used as a complement to the other fuels, while the fossil fuels substitute for each other.     

意大利热电联产现状:能源政策、法规及市场自由化的影响

热电联产在意大利的应用比较普遍，但中小型热电机组的发展则比较缓慢。介绍了意大利的能源政策、法规及市场自由化对热电联产的影响，还介绍了意大利环境方面法规，意大利在热电(冷)联产方面的激励措施等。     

调节阀内部流场数值模拟及能量损失分析

针对小流量单座调节阀,首先应用三维建模软件对其该阀进行宾体建模与造型,其次基于计算流体力学技术对阀门内部三维粘性流场进行数值模拟,从而获得了调节阀的流动特性参数,并对数值模拟计算结果进行了分析,得到了调节阀流道内能量损失的原因,最后以降低流动损失为目的,对能量损失严重的部位进行流道优化,并对优化后流道进行模拟计算.计算结果表明,与优化前的流道相比较,在满足原有调节性能的同时流动得到改善,能量损失明显降低.     

Effect of lattice strain on nanomaterials in energy applications: A perspective on experiment and theory

Nanostructured semiconducting materials such as nanoparticles, quantum dots, nanowires, nanorods, nanotubes, nanobelts, nanoribbons, nanosheets, nanolayers, nanofilms, etc have gained tremendous attention within the past decade due to their fascinating physical properties and potential technological applications in electronic and optoelectronic devices. Semiconducting materials are able to be altered with strain-inducing from tunable sizes and shapes due to quantum confinement effects. Lattice strain is found to be very useful as well as very economical methods for improving the performance of energy devices by modifying band structure of nanostructured materials. The use of strain in design of nanostructured semiconducting materials is now a standard technique for modulating their electronic structures to enhance both electron and hole mobilities. There are mainly three effects of strain on nanostructures: (i) electronic band modulation, (ii) buckling, and (iii) phase transformations. In this review, we mainly focus on both experimental and theoretical achievements for effect of strain in nanostructured materials. Finally, the review is concluded with perspectives regarding the effect of strain in low dimensional nanostructured semiconducting materials, particularly zero-, one-, and two-dimensional nanostructures in future.