• Energy Research

The methods of the nanofluid flows modeling are analyzed. In the first part of the paper, methods for simulating flows of gas nanosuspensions are systematically considered. It is shown when they should be described by kinetic or continuum equations. Particular attention is paid to situations in which the nanofluid flows need to be described by a mixed kinetic-hydrodynamic method. In the second part the thermophysical properties (viscosity and thermal conductivity) of nanofluids are discussed in detailed. It was shown that the transport coefficients of nanofluids depend not only on the volume concentration of the particles but also on their size and material. The viscosity increases with decreasing the particle size while the thermal conductivity increases with increasing the particle size. The last part of the paper deals with modeling the mixing in micromixure and convection heat transfer in the tube. In conclusion, we discuss the applicability of various commonly used similarity criteria, such as Reynol...

Quasi‐linear theory predicts that ions in resonance with transverse ion cyclotron waves suffer merely pitch angle diffusion while conserving their total kinetic energy in the frame moving with the wave phase speed. For the first time, direct observational evidence from Helios plasma data is shown for the occurrence of this pitch angle diffusion of solar wind protons, induced by resonance with parallel ion cyclotron waves propagating away from the Sun. Parts of the isodensity contours in velocity space are well outlined by a sequence of segments of circles centered at the adapted wave phase speed, which is assumed to vary slightly and to be due to dispersion smaller than the local Alfvén speed. This observation confirms the validity of basic concepts of resonant wave‐particle interactions as described by quasi‐linear theory. The solar wind proton velocity distributions show a “plateau” defined by a vanishing pitch angle gradient in the resonant regime, implying marginal stability of the distribution function. The implications of these results for solar wind ion heating and kinetic transport are discussed.

AbstractFixed‐film, fluidized‐bed bioreactors have been used successfully to treat dilute synthetic and actual wastewaters for long periods of time.

Energy generation through wind energy conversion systems (WECS) is expected to supply a considerable amount of electricity in the world's generation matrix. In this context, variable-speed wind turbines equipped with full-scale power electronic converters allow a WECS to be operated close to its maximum power point at each time instant. Furthermore, modern power converter guarantee high power quality, high conversion efficiency levels, reliability and flexibility. This work reviews and compares two types of modulation schemes to two novel ones that are able to drive a Δ-switch rectifier. The presented theoretical analysis is based on a WECS application. Circuit simulation and experimental results verify the operation with the considered strategies. It is shown that one of the novel sub-optimal modulation patterns presents very high performance without the need of a precise sector identification scheme.

Higher participation levels of wind power in power systems will increase the need for flexible back-up generation to balance the differences between predicted and realized wind power production. This is often an expensive solution. With distributed energy resources and more ICT at the demand side, novel, and possibly cheaper, ways for imbalance minimization arise. Micro combined heat-and-power (micro-CHP) is a novel domestic-level generation technology, producing heat and power simultaneously. Clusters of micro-CHPs can function as flexible virtual power plants (VPPs). This paper presents the design of an online coordination scheme that can substantially reduce the imbalance volumes and the associated costs for wind power traders by actively controlling a VPP comprising micro-CHP systems. It is shown that the imbalance volume and associated cost can be reduced by 73 % and 38 %, respectively.

A greenhouse pot experiment was undertaken to ascertain the efficiency of some organic materials on decreasing the mobility of heavy metals in soil and subsequent rates of their absorption by growing plants. An alluvial clay soil was amended with each of compost, biogas manure or humic acid, at doses of 0.5 & 1.0 %C. Faba bean (Vicia faba), as a leguminous winter crop, and maize (Zea mays), as a cereal summer crop, were planted in the amended soil. A mixture of Zn+ Pb + Cu was added at the permissible safe level of each mineral and double that permissible level. Controls of no organic or mineral addition were included. Rates of Zn, Pb & Cu uptake by plants had been measured at two plant growth periods, i.e. 45& 90 days for faba bean and 30 & 60 days for maize. Total and bioavailable amounts of those minerals were also determined in the cultivated soil at termination of the experiment. The obtained results indicated that humic acid was superior as to handicap the activity of heavy metals in soil, and thus diminished their uptake by plants, greatly at the higher rate of application, and followed descendingly by biogas manure and compost; that was the case at the first detection time. However, at the later growth period, humic acid had moved back to exchange the position with compost. Capacity of plant absorption for such metals showed the order: Zn> Cu>Pb. Faba bean took up higher amounts of the assigned minerals than maize. Contents of the heavy metals in soil oppositely reflected the position revealed in the grown plants.

Energy is an essential input for social development and economic growth. At present, globally the demand for energy is increasing in consonance with socio-economic development, though in developing countries it increases a little bit more quickly than developed countries. Energy consumption in developed countries grows at a rate of approximately 1% per year, and that of developing countries, 5% per year.

In this work we implement the type II seesaw mechanism into the framework of the $U(1)_{B-L}$ gauge model. As main gain, the right-handed neutrinos of the model get free to play the role of the dark matter of the universe. As side effect, the model realizes Higgs inflation without problem with loss of unitarity. Comment: minor changes, 19 pages, 9 figures

Offshore wind energy is considered to have tremendous potential for Germany's future electricity supply. Due to the technology's capital intensity, however, offshore wind energy has so far been considered the domain of large utilities. Municipal utilities on the contrary traditionally have strong ties to their community and conduct low risk business models at the regional and local level. Recently, however, German municipal utilities started to invest in offshore wind energy. Based on a series of interviews with municipal utility executives, the present study identifies two innovative business models and ten key drivers for municipal utilities' engagement in offshore wind energy. It is found that the new business models may have significant further potential and help to stimulate the German market. The present study contributes to the industry debate by identifying business model blueprints for offshore wind and to the academic debate by suggesting three generic types of business model innovation with different characteristics. Offshore wind energy is considered to have tremendous potential for Germany's future electricity supply. Due to the technology's capital intensity, however, offshore wind energy has so far been considered the domain of large utilities. Municipal utilities on the contrary traditionally have strong ties to their community and conduct low risk business models at the regional and local level. Recently, however, German municipal utilities started to invest in offshore wind energy. Based on a series of interviews with municipal utility executives, the present study identifies two innovative business models and ten key drivers for municipal utilities' engagement in offshore wind energy. It is found that the new business models may have significant further potential and help to stimulate the German market. The present study contributes to the industry debate by identifying business model blueprints for offshore wind and to the academic debate by suggesting three generic types of business model innovation with different characteristics.