Manfred Lenzen
Review: Current State of Development of Electricity-Generating Technologies: A Literature Review
Energies 2010, 3(3), 462-591; doi:10.3390/en3030462 - published online 18 March 2010
Show/Hide AbstractAbstract: Electricity is perhaps the most versatile energy carrier in modern economies, and it is therefore fundamentally linked to human and economic development. Electricity growth has outpaced that of any other fuel, leading to ever-increasing shares in the overall mix. This trend is expected to continue throughout the following decades, as large—especially rural—segments of the world population in developing countries start to climb the “energy ladder” and become connected to power grids. Electricity therefore deserves particular attention with regard to its contribution to global greenhouse gas emissions, which is reflected in the ongoing development of low-carbon technologies for power generation. The focus of this updated review of electricity-generating technologies is twofold: (a) to provide more technical information than is usually found in global assessments on critical technical aspects, such as variability of wind power, and (b) to capture the most recent findings from the international literature. This report covers eight technologies. Seven of these are generating technologies: hydro-, nuclear, wind, photovoltaic, concentrating solar, geothermal and biomass power. The remaining technology is carbon capture and storage. This selection is fairly representative for technologies that are important in terms of their potential capacity to contribute to a low-carbon world economy.

Roberto Capata and Antonino Coccia
Article: Procedure for the Design of a Hybrid-Series Vehicle and the Hybridization Degree Choice
Energies 2010, 3(3), 450-461; doi:10.3390/en3030450 - published online 15 March 2010
Show/Hide AbstractAbstract: For years, the interest of the UDR1 research group has focused on the development of a Hybrid Series (HS) vehicle, different from the standard one thanks to the use of a Gas Turbine set (GT) as a thermal engine. The reason for this choice resides in the opportunity to reduce weight and dimensions, in comparison to a traditional Internal Combustion Engine (ICE). It is not possible to use the GT engine set directly for the vehicle traction, therefore the UDR1 HS configuration shows the GT set connected with the electric generator only. The result is that the traction is purely electric. The resulting engine configuration is a commonly defined Hybrid Series. Many efforts are spent in the definition of a generic scientific method to define the correct ratio (Degree of Hybridization) between the installed power of the battery pack and that of the GT electric generator, which simultaneously guarantees the life of the battery pack and the capacity of the vehicle to complete a common mission without lack of energy or stopping. This article reports a method to define the power ratio between battery pack and GT generator, applied to a recent commission for the development of a mini city bus.

Takeharu Hasegawa
Article: Gas Turbine Combustion and Ammonia Removal Technology of Gasified Fuels
Energies 2010, 3(3), 335-449; doi:10.3390/en3030335 - published online 12 March 2010
Show/Hide AbstractAbstract: From the viewpoints of securing a stable supply of energy and protecting our global environment in the future, the integrated gasification combined cycle (IGCC) power generation of various gasifying methods has been introduced in the world. Gasified fuels are chiefly characterized by the gasifying agents and the synthetic gas cleanup methods and can be divided into four types. The calorific value of the gasified fuel varies according to the gasifying agents and feedstocks of various resources, and ammonia originating from nitrogenous compounds in the feedstocks depends on the synthetic gas clean-up methods. In particular, air-blown gasified fuels provide low calorific fuel of 4 MJ/m³ and it is necessary to stabilize combustion. In contrast, the flame temperature of oxygen-blown gasified fuel of medium calorie between approximately 9–13 MJ/m³ is much higher, so control of thermal-NOx emissions is necessary. Moreover, to improve the thermal efficiency of IGCC, hot/dry type synthetic gas clean-up is needed. However, ammonia in the fuel is not removed and is supplied into the gas turbine where fuel-NOx is formed in the combustor. For these reasons, suitable combustion technology for each gasified fuel is important. This paper outlines combustion technologies and combustor designs of the high temperature gas turbine for various IGCCs. Additionally, this paper confirms that further decreases in fuel-NOx emissions can be achieved by removing ammonia from gasified fuels through the application of selective, non-catalytic denitration. From these basic considerations, the performance of specifically designed combustors for each IGCC proved the proposed methods to be sufficiently effective. The combustors were able to achieve strong results, decreasing thermal-NOx emissions to 10 ppm (corrected at 16% oxygen) or less, and fuel-NOx emissions by 60% or more, under conditions where ammonia concentration per fuel heating value in unit volume was 2.4 × 10² ppm/(MJ/m³) or higher. Consequently, principle techniques for combustor design for each IGCC were established by the present analytical and experimental research. Also, this paper contains some findings of the author’s previously published own works and engages in wide-ranging discussion into the future development of gasification technologies.

Pang-Leen Ong and Igor A. Levitsky
Review: Organic / IV, III-V Semiconductor Hybrid Solar Cells
Energies 2010, 3(3), 313-334; doi:10.3390/en3030313 - published online 5 March 2010
Show/Hide AbstractAbstract: We present a review of the emerging class of hybrid solar cells based on organic-semiconductor (Group IV, III-V), nanocomposites, which states separately from dye synthesized, polymer-metal oxides and organic-inorganic (Group II-VI) nanocomposite photovoltaics. The structure of such hybrid cell comprises of an organic active material (p-type) deposited by coating, printing or spraying technique on the surface of bulk or nanostructured semiconductor (n-type) forming a heterojunction between the two materials. Organic components include various photosensitive monomers (e.g., phtalocyanines or porphyrines), conjugated polymers, and carbon nanotubes. Mechanisms of the charge separation at the interface and their transport are discussed. Also, perspectives on the future development of such hybrid cells and comparative analysis with other classes of photovoltaics of third generation are presented.

Maria C. Lechmann, Dominik Koll, Daniel Kessler, Patrick Theato, Wolfgang Tremel and Jochen S. Gutmann
Article: Comparison of Hybrid Blends for Solar Cell Application
Energies 2010, 3(3), 301-312; doi:10.3390/en3030301 - published online 5 March 2010
Show/Hide AbstractAbstract: In blended hybrid systems distinct micro- or nanostructured materials can be formed by phase separation. Network structures of particles or rods in a polymer matrix can be developed via self-assembly. We use this blending approach to compare active materials for application in solar cell devices. Blends were fabricated from either poly(hexylthiophene) P3HT or poly(triphenylamine) PTPA mixed with nanocrystalline TiO₂ rods. In this manner, we compare two different hole conducting polymers in their performance in photovoltaic devices, while experimental conditions are kept identical. We find that the choice of solvent and photovoltaic characterization conducted in inert atmosphere is of importance for blends prepared from P3HT/TiO₂ blends, but not for PTPA/TiO₂ blends. Even though prepared with the same TiO₂ rods, solar cells prepared from PTPA blends showed an enhanced efficiency when measured under ambient conditions. Furthermore, the PTPA/TiO₂ showed higher long-term stability.

Xiaohua Liu, Yongjing Lin, Sa Zhou, Stafford Sheehan and Dunwei Wang
Review: Complex Nanostructures: Synthesis and Energetic Applications
Energies 2010, 3(3), 285-300; doi:10.3390/en3030285 - published online 26 February 2010
Show/Hide AbstractAbstract: Connected through single crystalline junctions, low dimensional materials such as nanowires and nanorods form complex nanostructures. These new materials exhibit mechanical strengths and electrical conductivities superior to their constituents while maintaining comparable surface areas, an attribute ideal for energetic applications. More efficient solar cells, higher capacity batteries and better performing photoelectrochemical cells have been built using these materials. This article reviews this exciting new class of materials and covers topics from controlled syntheses to applications in photovoltaics, chemical energy conversion and electrical charge storage. Mechanisms responsible for the improved performance are discussed. The prospect of their applications in a broader energy-related field is analyzed.