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Abstract Sweet sorghum, a C4 plant, is known to be a unique, versatile, and potential energy crop that can be separated into starchy grains, soluble sugar juice, and lignocellulosic biomass. The fermentable sugars in the juice (53–85% sucrose, 9–33% glucose, and 6–21% fructose) can be directly fermented into ethanol. The grain is primarily starch (62–75%), which can be hydrolyzed and fermented into ethanol. The bagasse, a fibrous lignocellulosic material, can be used to produce cellulosic ethanol, heat and/or power co-generation. In this review, the potential of sweet sorghum for bioenergy production (of various forms) using recently developed cultivars with improved agronomic performance was discussed. In addition, sweet sorghum was compared with other starch, sugar, and lignocellulosic feedstocks. Studies have been conducted on alternative pathways to convert whole sweet sorghum stalks and bagasse into bioenergy. However, very little review of the techno-economic analysis of bioenergy production and co-products from sweet sorghum has been published. The aim of this research was to review the current knowledge of agronomic requirement for cultivating sweet sorghum, the productivity of recently developed cultivars for bioenergy production, and pathways of converting sweet sorghum crop into bioenergy as well as the techno-economic feasibility of using sweet sorghum for bioenergy.

Abstract Vietnam is a tropical country, stretching from latitude 6 to 23 on the Northern parallels. Its land area is around 320,000 km2, its population about 73 million. Vietnam is also a member of the ASEAN countries. The Renewable Energy Sources in Vietnam are very abundant and diverse such as Solar Energy, Micro-Hydro Power, Wind Energy, Geothermal, Biogas, Biomass, Tide and Wave Energy etc. Evaluation of the potential of these Energy Sources for its application for the people who live in the remote areas is the subject of this paper.

Abstract Renewable energy sources and especially solar energy may be the answer to the increasing demand for energy, leading to the reduction of fossil fuel consumption and its associated negative environmental impact. An attractive solution to this problem could be the combination of renewable and conventional energy sources technologies such as the integrated solar combined cycle power plants (ISCCP). In this paper the operation of a 50 MW ISCCP with natural gas and parabolic trough solar collectors was simulated using TRNSYS software. The proposed power plant performance, fuel consumption and solar contribution were analyzed through six different simulation scenarios for different collector area. Two different modes of operation, namely power boost and fuel saving, were considered. Also, an economic analysis shows the optimal contribution rate of solar field taking into consideration the results of various simulation scenarios.

Small-scale wind turbine operations within the urban environment are exposed to high levels of gusts and turbulence compared to flows over less rough surfaces. There is therefore a need for such systems to not only cope with, but to thrive under such fluctuating flow conditions. This paper addresses the potential importance of gust tracking technologies within the urban environment via the analysis of the additional energy present in the gusty wind resource using high resolution measurements at two urban roof-top locations. Results demonstrate significant additional energy present in the gusty wind resource at high temporal resolution. This energy is usually under-represented by the use of mean wind speeds in quantifying the power in the wind over longer averaging times. The results support the promise of capturing a portion of this extra energy through gust tracking solutions. The sensitivity of this “additional” wind energy to averaging time interval is also explored, providing useful information for the design of gust tracking or dynamic control algorithms for small-scale turbines. Relationships between turbulence intensity and excess energy available are drawn. Thus, an analytical model is proposed which may prove useful in predicting the excess energy available across wide areas from, for example, boundary layer turbulence models.

Efficient design of wave energy converters requires an accurate understanding of expected loads and responses during the deployment lifetime of a device. A study has been conducted to better understand best-practices for prediction of design responses in a wave energy converter. A case-study was performed in which a simplified wave energy converter was analyzed to predict several important device design responses. The application and performance of a full long-term analysis, in which numerical simulations were used to predict the device response for a large number of distinct sea states, was studied. Environmental characterization and selection of sea states for this analysis at the intended deployment site were performed using principle-components analysis. The full long-term analysis applied here was shown to be stable when implemented with a relatively low number of sea states and convergent with an increasing number of sea states. As the number of sea states utilized in the analysis was increased, predicted response levels did not change appreciably. However, uncertainty in the response levels was reduced as more sea states were utilized.

Abstract This paper addresses the importance of the probabilistic analysis in determining the wave energy potential to support the design of electrical generators for wave energy conversion. The irregular activity of ocean waves induces variable frequencies and amplitudes of operation for point absorbers electrical generators, which may lead to the construction of inefficient electrical machines. Applying probabilistic models to describe the ocean wave's behavior allows the determination of the values most likely to be sampled for ocean-state parameters. Knowing these values, the most expected ocean wave potential can be determined and a proper device design can be performed. This work also refers to the importance of using the joint probability models instead of the marginal ones. Seven locations at the Portuguese coast are evaluated in order to determine their wave energy resource potential.

Abstract A small reverse osmoisis (RO) plant supplied by a photovoltaic (PV) power supply has been installed at the island of Gran Canaria. On behalf of this system the feasibility of small PV-RO systems (1 m3/d) is investigated. The RO-plant is described in detail concerning its technical specifications, its operation constraints and its energy demand. Furthermore the photovoltaic power supply is described in detail. With simulations it is shown how the system is designed to guarantee a reliability of more than 96% in the water supply. A brief economic analysis shows that the water production costs are still high (about 16 $/m3) but can be lowered in future.

Six corrosion protection systems for offshore wind power constructions have been subjected to offshore conditions on a test site in the North Sea in three different exposure zones, namely splash zone, intermediate zone, and underwater zone. The systems included single- and multiple-layered organic coatings, metal-spray coatings, and duplex coatings. Special testing specimens were designed and manufactured and exposed to an offshore environment for three years in order to characterize particular constructive details for different corrosivity zones. The following target parameters were investigated: intensity of fouling, anti-corrosive effect, coating adhesion, coating integrity, flange corrosion, coating performance over welds, and condition of screw connections. Fouling was an issue in the underwater zone and in the intermediate zone, but it did not affect the coating corrosion protection capacity. It was found that duplex systems, consisting of Zn/Al spray metallization, intermediate particle-reinforced epoxy coating, and polyurethane top layer, provided the highest anti-corrosive effect. Mechanical damage to the coatings initiated coating delamination and substrate corrosion. Effective coating systems should be either very resistant to impact or able to compensate for corrosion of the steel. Flange connections were found to be critical structural parts in the splash zone in terms of corrosion. Notable crevice corrosion was observed at places. Except for one coating system, welds have been protected well. Welds, however, affected the corrosion of the steel inside the uncoated internal sections in the underwater samples. Coating integrity on difficult-to-coat structural parts was satisfactory for all systems.

A full three-dimensional, non-isothermal computational fluid dynamics model of a tubular-shaped proton exchange membrane (PEM) fuel cell has been developed. This comprehensive model accounts for the major transport phenomena in a PEM fuel cell: convective and diffusive heat and mass transfer, electrode kinetics, and potential fields. In addition to the tubular-shaped geometry, the model feature an algorithm that allows for more realistic representation of the local activation overpotentials which leads to improved prediction of the local current density distribution. Three-dimensional results of the species profiles, temperature distribution, potential distribution, and local current density distribution are presented. The model is shown to be able to understand the many interacting, complex electrochemical, and transport phenomena that cannot be studied experimentally.