Heat release and engine performance effects of soybean oil ethyl ester blending into diesel fuel

The engine performance impact of soybean oil ethyl ester blending into diesel fuel was analyzed employing heat release analysis, in-cylinder exergy balances and dynamometric tests. Blends with concentrations of up to 30% of soybean oil ethyl ester in volume were used in steady-state experiments conducted in a high speed turbocharged direct injection engine. Modifications in fuel heat value, fuel-air equivalence ratio and combustion temperature were found to govern the impact resulting from the addition of biodiesel on engine performance. For the analyzed fuels, the 20% biodiesel blend presented the best results of brake thermal efficiency, while the 10% biodiesel blend presented the best results of brake power and sfc (specific fuel consumption). In relation to mineral diesel and in full load conditions, an average increase of 4.16% was observed in brake thermal efficiency with B20 blend. In the same conditions, an average gain of 1.15% in brake power and a reduction of 1.73% in sfc was observed with B10 blend.     

The outlook for renewable energy in Navarre: An economic profile

This paper describes the outlook and development of renewable energy in Navarre (Spain), which has become one of the leading regions in renewables over the last 10 years. This paper focuses its attention on the key features of the energy policy in Navarre, where there has emerged a dynamic enterprise sector. This sector has enormously increased its employment rates in the region. The success of renewable energy in Navarre is the result of the joint impact of decisive institutional support, industrial initiatives and consensus among social agents with regard to renewables. Tax incentives and local investment programs designed to break down the reluctance of local authorities and a campaign to obtain public support have, moreover, proven more efficient than the prior feed-in tariffs scheme, designed to develop the renewable energy sector and create international companies within it. The paper culminates in a detailed prognosis based on the SRN2003 survey of employment and installed power, which covers the majority of the firms operating in the Navarre renewables sector. Findings, however, suggest that the future of the sector in Navarre could be held back by the shortage of trained workers. This article might serve as a pertinent example for the deployment of renewables at regional level worldwide.     

Enhancing information for solar and wind energy technology deployment in Brazil

Brazil's primary energy matrix is based on more than 47% of renewables, and more than 85% of its electricity is generated by hydro power sources. Despite this large fraction of renewable energy resources, less than 0.3% of the national energy supply comes from solar or wind sources. This paper presents a diagnostic review on the penetration of the solar and wind energy technologies in Brazil. It also includes a survey of the latest government policies and incentives for renewable energies deployment by entrepreneurs, industry and commercial and residential consumers. In addition, the paper analyses how to best meet the requirements for policy support and information technology to boost the deployment of solar technology and wind energy in Brazil. This study was mostly based on results of a widely distributed survey covering key issues, and also by personal interviews carried out with key stakeholders in order to better understand the issues highlighted in the survey responses. The study pointed out some of the main obstacles to effectively promote and improve government policies and actions for investment in solar and wind energy market in Brazil.     

Modeling long-term dynamics of electricity markets

In the last decade, many countries have restructured their electricity industries by introducing competition in their power generation sectors. Although some restructuring has been regarded as successful, the short experience accumulated with liberalized power markets does not allow making any founded assertion about their long-term behavior. Long-term prices and long-term supply reliability are now center of interest. This concerns firms considering investments in generation capacity and regulatory authorities interested in assuring the long-term supply adequacy and the stability of power markets. In order to gain significant insight into the long-term behavior of liberalized power markets, in this paper, a simulation model based on system dynamics is proposed and the underlying mathematical formulations extensively discussed. Unlike classical market models based on the assumption that market outcomes replicate the results of a centrally made optimization, the approach presented here focuses on replicating the system structure of power markets and the logic of relationships among system components in order to derive its dynamical response. The simulations suggest that there might be serious problems to adjust early enough the generation capacity necessary to maintain stable reserve margins, and consequently, stable long-term price levels. Because of feedback loops embedded in the structure of power markets and the existence of some time lags, the long-term market development might exhibit a quite volatile behavior. By varying some exogenous inputs, a sensitivity analysis is carried out to assess the influence of these factors on the long-run market dynamics.     

Short-term optimal wind power generation capacity in liberalized electricity markets

Mainly because of environmental concerns and fuel price uncertainties, considerable amounts of wind-based generation capacity are being added to some deregulated power systems. The rapid wind development registered in some countries has essentially been driven by strong subsidizing programs. Since wind investments are commonly isolated from market signals, installed wind capacity can be higher than optimal, leading to distortions of the power prices with a consequent loss of social welfare. In this work, the influence of wind generation on power prices in the framework of a liberalized electricity market has been assessed by means of stochastic simulation techniques. The developed methodology allows investigating the maximal wind capacity that would be profitably deployed if wind investments were subject to market conditions only. For this purpose, stochastic variables determining power prices are accurately modeled. A test system resembling the size and characteristics of the German power system has been selected for this study. The expected value of the optimal, short-term wind capacity is evaluated for a considerable number of random realizations of power prices. The impact of dispersing the wind capacity over statistical independent wind sites has also been evaluated. The simulation results reveal that fuel prices, installation and financing costs of wind investments are very influential parameters on the maximal wind capacity that might be accommodated in a market-based manner.     

Photoelectrochemical properties of rhodamine-C18 sensitized p-CuSCN photoelectrochemical cell (PEC)

Surface states in p-type Cu^I thiocyanate (CuSCN) were detected from I−V characteristics, diffuse reflectance spectra, and photocurrent action spectra. The p-CuSCN films are sensitized by rhodamine with octadecyl-alkyl chain, and the sensitized photocurrent is observed with the visible light illumination. In spite of the surface states in p-CuSCN, the maximum photocurrent quantum efficiency (gf_max) at λ = 560 nm, in 1 × 10⁻⁴ M KI + I₂ solution, pH = 6, reached 8.6%, where the surface dye concentration of photocathode Cu/p-CuSCN/Dye was 1.1 × 10¹⁴ molecules cm⁻². Photocathodes were biased at −0.25 V versus AgCl/Ag to give a zero dark current. From the variation of φ values with the reduction potential of electron acceptors, the cathodic sensitization mechanism presented is further confirmed.     

Photoproduction of H2 by wildtype Anabaena PCC 7120 and a hydrogen uptake deficient mutant: from laboratory experiments to outdoor culture

We have analyzed the filamentous cyanobacterium Anabaena PCC 7120 (wildtype) containing one nitrogenase, one uptake hydrogenase and one bidirectional hydrogenase and its hydrogen uptake deficient mutant AMC 414 for their H₂ production capacities. Anabaena PCC 7120 and AMC 414 had similar growth rates in turbidostat mode with increased growth rates at higher light intensity. Rates of C₂H₂ reduction were similar for both strains. In contrast to the wildtype, AMC 414 produced H₂ in a PhotoBioReactor (PhBR) using air as the lifting gas. The rate of H₂ production increased with light intensity and was not even saturated at 456 μEm⁻² s⁻¹. H₂ production increased significantly when replacing the air with argon. The maximal H₂ production during outdoor conditions was recorded using AMC 414 with a peak at 14.9 ml H₂ h⁻¹ l⁻¹. Despite the relatively high production, maximal efficiency of solar energy to H₂ conversion was only 0.042%. A molecular method was developed to analyze the relative abundancies of weight and mutant in competition experiments in the PhBR.     

Steam reforming of ethanol over bimetallic RhPt/La2O3: Long-term stability under favorable reaction conditions

Recently, the steam reforming of biofuels has been presented as a potential hydrogen source for fuel cells. Because this scenario represents an interesting opportunity for Colombia (South America), which produces large amounts of bioethanol, the steam reforming of ethanol was studied over a bimetallic RhPt/La₂O₃ catalyst under bulk mass transfer conditions. The effect of temperature and the initial concentrations of ethanol and water were evaluated at space velocities above 55,000 h⁻¹ to determine the conditions that maximize the H₂/CO ratio and reduce CH₄ production while maintaining 100% conversion of ethanol. These requirements were accomplished when 21 mol% H₂O and 3 mol% C₂H₅OH (steam/ethanol molar ratio = 7) were reacted at 600 °C. The catalyst stability was assessed under these reaction conditions during 120 h on stream, obtaining ethanol conversions above 99% during the entire test. The effect of both H₂ and air flows as catalyst regeneration treatments were evaluated after 44 and 67 h on stream, respectively. The results showed that H₂ treatment accelerated catalyst deactivation, and air regeneration increased both the catalyst stability and the H₂ selectivity while decreasing CH₄ generation. Fresh and spent catalyst samples were characterized by TEM/EDX, XPS, TPR, and TGA. Although the Rh and Pt in the fresh catalyst were completely reduced, the spent samples showed a partial oxidation of Rh and small amounts of carbonaceous residue. A possible Rh–Pt–Rh₂O₃ structure was proposed as the active site on the catalyst, which was regenerated by air treatment.     

Adhesion and debonding kinetics of photovoltaic encapsulation in moist environments

Debonding of photovoltaic (PV) encapsulation in moist environments is frequently reported but presently not well understood or quantified. Temperature cycling, moisture, and mechanical loads often cause loss of encapsulation adhesion and interfacial debonding, initially facilitating back‐reflectance and reduced electrical current, but ultimately leading to internal corrosion and loss of module functionality. To investigate the effects of temperature (T) and relative humidity (RH) on the kinetics of encapsulation debonding, we developed a mechanics‐based technique to measure encapsulation debond energy and debond growth rates in a chamber of controlled environment. The debond energy decreased from 2.15 to 1.75 kJ m⁻² in poly(ethylene‐co‐vinyl acetate) (EVA) and from 0.67 to 0.52 kJ m⁻² in polyvinyl butyral when T increased from 25 to 50°C and 20 to 40°C, respectively. The debond growth rates of EVA increased up to 1000‐fold with small increases of T (10°C) and RH (15%). To elucidate the mechanisms of environmental debonding, we developed a fracture‐kinetics model, where the viscoelastic relaxation processes at the debonding‐tip are used to predict debond growth. The model and techniques constitute the fundamental basis for developing accelerated aging tests and long‐term reliability predictions for PV encapsulation. Copyright © 2015 John Wiley & Sons, Ltd.