Band 1, Heft 5-6

For several years, low-emission energy systems have been asked for. It is all the more astonishing that an almost zero-emission method of power generation was invented more than 150 years ago but has not been successfully established yet. Fuel cells have been gaining ground since the new millennium, especially in Germany and Japan. Following the Japanese Government's decision to significantly reduce emission rates of the insular state, the economy has started to develop and refine fuel cell technology. Due to the planned nuclear phase-out, this new energy concept has started to come into focus in Germany as well. The new technology is designed for stationary and mobile applications alike and can hence provide power for domestic housing as well as for vehicles. There are, however, still supply chain deficiencies that impede a more widespread commercialisation.

Extensive energy conversion of solar energy can only be achieved by large-scale collection of solar flux. The technology that satisfies this requirement must be as simple as possible to reduce capital cost. Overall water splitting by powder-form photocatalysts directly produces a mixture of H 2 and O 2 (chemical energy) in a single reactor, which does not require any complicated parabolic mirrors and electronic devices. Because of its simplicity and low capital cost, it has tremendous potential to become the major technology of solar energy conversion. Development of highly efficient photocatalysts is desired. This review addresses why visible light responsive photocatalysts are essential to be developed. The state of the art for the photocatalysts for overall water splitting is briefly described. Moreover, various fundamental aspects for developing efficient photocatalysts, such as particle size of photocatalysts, cocatalysts, and reaction kinetics are discussed.

In this work we report the properties and characteristics of a pitch carbon-coated lithium sulfide material. We show that this material behaves as a very promising electrode in liquid glyme-based and in solid poly(ethylene oxide) PEO-based electrolyte lithium cells. Particular relevant is the response obtained in the solid-state configuration where a capacity approaching the theoretical value of the full Li 2 S conversion process, i.e. 1200 mAh is obtained at a C/10 rate with no signature of ohmic polarization. The solid-state cell cycles at a C/3 rate with a stable capacity of 500 mAh , i.e., a value about three times higher than that offered by conventional intercalation lithium metal oxide electrodes. This unique performance makes the pitch carbon-coated lithium sulfide electrode a good candidate for the development of high energy density, lithium-metal free-sulfur superbatteries to be addressed to the electric vehicle market.

Application of artificial roughness on underside of absorber surface has been found to be effective technique to improve thermo hydraulic performance of solar air heaters. In progression to the previous researches, the present study discloses the effect of broken V-rib roughness combined with staggered ribs on heat transfer and friction in a flow through artificially roughened solar air heater duct. The experimentations were performed to collect the data on heat transfer and friction by varying the Reynolds number (Re) between 3000 and 17,000, relative gap position ( s ′/ s ) from 0.2 to 0.8, for the fixed values of relative staggered rib pitch p ′/ p = 0.6, relative staggered rib size r / e = 1, relative roughness pitch p / e = 10, relative roughness height e / D h = 0.043, relative gap size g / e = 1, and angle of attack α = 60°. The present roughness geometry with relative gap position ( s ′/ s ) of 0.6 corresponding to flow Reynolds number (Re) of 13,150 yields the best thermohydraulic performance.

Hybrid organic-inorganic solar cells from poly(3-hexylthiophene) (P3HT) and freestanding silicon nanocrystals (Si-ncs) combine the advantages of silicon-based photovoltaics with the cost-efficient solution processing technique. At present, the microwave-plasma synthesis of Si-ncs that allows for a future upscaling to industrial demands is at the expense of the Si-nc surface quality and the number of charge-trapping defects. Here, we present an enhancement of the solar cell performance by identifying the major factors which are limiting the device efficiency. With the help of low-cost post-growth treatments of the Si-ncs and the optimization of various device parameters, P3HT:Si-ncs bulk heterojunction solar cells with an efficiency up to 1.1% are achieved. In particular, etching of the Si-ncs with hydrofluoric acid to remove the surface oxide shells and surface defects has a strong impact on the solar cell performance. An intermediate Si weight ratio of around 60% is found to lead to the highest current densities. For Si-ncs with very small diameters, an additional enhancement of the open circuit voltage was observed. Moreover, we show that the structural order of P3HT has a strong influence on the efficiency, which can be explained by an improved charge carrier separation at the P3HT/Si-ncs interface in combination with an enhanced charge transport in the P3HT phase.

The various possible replacements for gasoline in our future are briefly reviewed. The most suitable alternative seems to be connected with methanol. Normal methanol is not recommended. It should be methanol that is synthesized from hydrogen and CO 2 – which is taken “from the atmosphere.” Biomass has been created from CO 2 and water in the atmosphere, so burning biomass will provide the CO 2 “from the atmosphere.” This CO 2 then should be combined with hydrogen to make the methanol. The advantages of this fuel are many. The basic ingredients are water and biomass together with a renewable source (such as wind) is all that is needed. These are inexhaustible and nonpolluting. I propose that methanol “from the atmosphere” should be the fuel to replace gasoline throughout the world. Our cars would not need any change. Methanol is a reasonable fuel for fuel cells in our electric cars

Sudan is an agricultural country with fertile soil and ample water resources, as well as livestock and forestry resources, and agricultural residues. Energy is one of the key factors in the development of Sudan's national economy. We present an overview of the energy situation in Sudan, with reference to its end uses and its regional distribution. We separate energy sources into two main types: conventional energy (biomass, petroleum products, and electricity) and non-conventional energy (solar power, wind energy, hydro-electric, etc.). Sudan has a relatively high abundance of sunshine and solar radiation, and has moderate biomass, hydro-electric and wind energy resources. Exploiting the available new and renewable energy sources to provide part of the local energy demand, as alternatives to conventional fossil energy, has become a major issue in Sudan's strategic planning of future energy policies. Sudan presents an important case study with respect to renewable energy, as it has a long history of meeting its energy needs by use of renewable sources; Sudan's portfolio is broad and diverse, due in part to the country's wide range of climates and landscapes. Like many African frontrunners in the utilisation of renewable energy, Sudan has a well-defined commitment to continue research, development, and implementation of new technologies. Sustainable low-carbon energy scenarios in the new century emphasize the importance of exploiting the untapped potential of renewable resources. Sudan's rural areas in particular, can benefit from this transition. The increased availability of reliable and efficient energy services will stimulate the development of new alternatives. We conclude that using renewable, environmentally friendly energy must be encouraged, promoted, implemented, and demonstrated by full-scale energy plants or collection devices, in particular for use in remote rural areas.