• Energy Research

The performance capabilities of an axially laminated anisotropic rotor (ALA) in a high-speed synchronous reluctance motor (SynRM) were studied. A 12 kW ALASynRM was designed as an alternative to a high-speed induction motor (IM) with a solid rotor. The electromagnetic design was implemented taking into account possible issues related to the new manufacturing methods, which require thicker rotor layers than in a typical ALA. The ALASynRM shows a higher efficiency than the corresponding IM with a smooth or slitted solid rotor equipped with copper end rings. To verify the design method, a prototype IM with a smooth solid rotor was built and tested. In the analysis, it was found that, similar to IMs, in an ALASynRM a considerable part of losses takes place in the rotor despite the absence of slip-related losses in the SynRM. The distribution of eddy current losses in the ALA rotor is significantly uneven. The torque ripple in the ALASynRM is considerably larger than the corresponding ripple in IMs.

A commissioning and laboratory tests of an active magnetic bearing supported PM 3kW blower are presented. The motor operation is evaluated in no-load and load tests. An identification of AMB-rotor system, testing of H ∞ centralized control and mass-flow of the blower for recirculation of anode gas in a SOFC are discussed. The key results include comparison between analytical and measured values of an output sensitivity function of different MIMO controllers, measured efficiency and output motor power, and blower measurements.

Fast methods to estimate iron losses of the permanent magnet traction motor during the drive cycle of the electrical vehicle are compared. The methods use the iron loss information calculated by a finite-element analysis as a function of rotational speed both at no load and with a short-circuited stator to take into account the variable frequency and field weakening of the traction motor. The effect of iron losses on the optimal current components, providing the maximum efficiency, is studied. Several methods yield a good accuracy even based on the no-load iron loss only, but the accuracy can be improved especially in deep field weakening by including the short-circuit iron loss information in the analysis.

This article focuses on greenhouse gas (GHG) emissions reduction and on the economics in renewable electricity production at sawmills. Electricity production application in this study is a hermetic turbogenerator (HTG). The HTG is a small-scale steam turbine-generator unit of compact size that achieves high efficiency. The paper studies GHG emissions and the economics of HTG use in sawmills using life cycle assessment methodologies. Small- and large-scale HTG processes are studied in three scenarios. Sawmills produce large volumes of biomass by-products which are mainly used to produce heat needed in lumber dryers. However, due to remote location of sawmills there may be no use for excess biomass. HTGs can be used to produce electricity in addition to heat (CHP), which may help to increase renewable electricity production in sparsely populated areas. It is concluded that from the economic perspective HTGs may be an attractive option but financial viability is dependent on energy prices, required investments, and by-product value. From the climate change perspective, electricity production with HTGs may be a good option if there is excess biomass sources available.

The effect of unbalanced magnetic pull (UMP) caused by air gap eccentricity on the vibration of a permanent magnet synchronous motor (PMSM) is investigated. The force model is established analytically by the Maxwell stress method. For accurate consideration of the eccentricity condition, mixed eccentricity, axial-varying eccentricity, and eccentricity caused by motor frame vibration are modeled and combined. The model of the rotor–bearing system, which includes the UMP model, is developed with two different methods. In the first method, UMP is added as a linear negative spring to the rotor model, whereas in the second method, UMP is included as an external force. The rotor system of a centrifugal pump driven by an integrated PMSM is modeled using beam elements, and the two distinct modeling approaches for UMP are applied. From the results, the UMP effect on vibration and the difference between the two modeling methods are investigated. To verify the results of the analysis, experimental work is done with a pump test rig, and results of frequency spectra are obtained. Based on the analyses and experimental work, the negative stiffness effect and additional vibration excitations caused by UMP are examined.

Expectations on wastewater sludge treatment and recovery of its energy and material contents are increasing because of the tightening legislation and the obligation to reduce environmental impacts of sludge disposal. The objective of this study was to analyze the performance of a heat and power generating sludge combustion plant from technical and economical viewpoints and to compare the studied concept to optional sludge treatment technologies. The plant performance was modeled for sewage sludge produced by approximately 200 000 inhabitants. Two plant sizes below 1 000 kWe range were investigated, the smaller plant using sludge as the only fuel and the larger plant with wood chips as the additional fuel. The plants were compared with heat-only plants of similar size. The payback periods for heat-only plants are typically shorter than with the cogenerating plants because the changes in plant investment affect stronger the economy than do the revenues from selling electricity. The gate fee of sludge treatment has the strongest effect on the payback period. The selection of the plant concept (cogeneration, heat only or pure electricity generation) is, however, affected more by the local demand of heat and electricity than pure economy. The selection of the optimal technology for sludge treatment is a complicated task. The studied concept can be the optimal choice, for example, if there is no cement kiln or co-combustion possibility near the source of sludge, if there is no land enhancement demand for the digested sludge, or if the energy surplus from combustion compared to anaerobic digestion is considered more valuable than nutrient recovery possibility from digestion. If the new technology concept is found competitive, it still has to meet the challenge of acceptability from the business, social and cultural points of view.