Mannes Wolters

Bio: Mannes Wolters is an academic researcher from University of Twente. The author has contributed to research in topics: Hydrogen & Natural gas. The author has an hindex of 5, co-authored 32 publications receiving 136 citations.

A new engineering approach to predict the long-term hydrostatic strength of unplasticized poly(vinyl chloride) pipes

Abstract: Extruded polymer pipes are qualified using pressurized pipe tests. With these tests the long-term hydrostatic strength is determined by subjecting the pipes to an internal pressure, while measuring the time-to-failure. Although these tests can be accelerated (at higher temperatures), they remain time consuming and require a spacious experimental setup. To circumvent this costly method a model based approach is proposed by which the long-term hydrostatic strength is predicted. Using short term measurements, the input parameters for this approach can be determined. In this engineering approach the effects of physical aging are included. The approach is capable to quantitatively predict the (long-term) failure time of pipe sections under internal pressure.

Physical Ageing of uPVC Gas and Water Pipes

Abstract: The kinetics of physical ageing of un-plasticized P VC was investigated using Differential Scanning Calorimetry. A quantitative model was set up that describes the influence of ageing time and temperature on the well-known endothermic ageing peak. The activation energy for physical ageing of 116 kJoule/mole is very close to the literature value (115 kJoule/mole). Physical ageing of uPVC pipes leads to a decrease i n impact resistance and may ‐ for uPVC water pipes ‐ decrease the water hammer resistance. To study this, Rapid Crack Propagation measurements were performed, to assess the Critical Pressure. Crack initiation was always performed where the wall was at its thickest. Thus, RCP data was obtained with about 80% less scatter than usual. Excavated uPVC gas and water pipes have absorbed varying concentrations of water (maximum uptake 0.6 %) and carbon dioxide, which both act as plasticizer. Along with physical ageing these phenomena may affect impact performance.

Methane permeation through advanced high-pressure plastics and composite pipes

Abstract: There is a clear market wish to use plastic and composite pipes for natural gas pipelines at higher pressures than the traditional limit of 10 bars for PE100 pipes. Candidates are Polyamide 12, plasticized PA6.12, Polyamide 11, other long-chain Polyamide pipes and PE-based composite pipes (Multilayer M pipes). However, at higher pressures permeation of natural gas through the wall of plastic or composite pipes increases, depending on materials composition and SDR. An international testing programme was started to measure the permeation rate and permeability coefficient of 14 different 110mm plastic and composite pipes. Sponsors are pipe and resin manufacturers and GERG (European Gas Research Group). Included in the investigation were 5 different brands of Polyamide pipe, a pipe produced from a PE100 resin containing 10% of a special anti-permeation additive and a RTP Light pipe. Two PE100 pipes were measured for reference. Using the permeation curves, the permeability coefficient PC (in ml.mm/m2/bara/day), diffusion coefficient D (in cm2/sec.) and solubility coefficient S (in kbara-1) for methane have been calculated for all measured pipes. The PA pipes show only a few percent of the permeability coefficient of PE100 pipe. The PE100 pipe containing 10 % of a special anti-permeation additive possesses a 5.2 times lower permeability coefficient than regular PE100 pipe. Therefore, this modified PE100 pipe shows a permeation rate in between the values for PE100 and PA pipes.

Securing the public interest in electricity generation markets. The myths of the invisible hand and the copper plate

Abstract: Two aspects of investment in generation capacity in liberalized electricity markets are investigated: the question of whether investment will be sufficient to meet society's goals for the reliability of electricity supply (generation adequacy) and the question of how to coordinate investment in electricity generation capacity in a competitive market while bound by the physical requirements and limitations of the electricity networks. The study focuses on the situation in European electricity markets. A number of factors discourage generating companies from investing in a level of generation capacity that is optimal for society as a whole. Due to the limited possibilities for the storage of electricity and the low price-elasticity of demand, electricity prices are highly volatile. This, in addition to the lack of historical trend data (due to the short history of liberalized electricity markets), insufficient transparency and high capital costs, causes investment risk to be high. Investment risk is increased by several sources of regulatory uncertainty. Given these circumstances, it is rational for investors to be cautious. A number of policy options for improving investment incentives and for stabilizing the volume of generation capacity, called capacity mechanisms, are described and analyzed. A policy framework is introduced for evaluating them and deciding on the best policy options for different circumstances. With respect to the issue of coordinating investment in electricity generation capacity with the networks, the consequences of the choice for fixed transmission tariffs in most European countries were investigated. While fixed transmission tariffs are intended to make the market simple and transparent, paradoxically they create the need for several additional measures to compensate for their external effects. Among these, the implementation of a congestion management method ranks among the most necessary measures. The options for congestion management, given the choice for fixed transmission tariffs, are analyzed and compared.

Progress in Nuclear Magnetic Resonance Spectroscopy

Abstract: ING AND INDEXING