DNV GL (Netherlands)

This report is part of HyDelta work package 2 “Odorisation”. The research question within this part of the HyDelta program was: “what is the odor strength and odor characteristic of candidate odorants in hydrogen and how do these relate to the odor characteristic and odor strength in natural gas?” With the results of this research, the studies that have been done before within this work package and a literature search on foreign experiences, an attempt has been made to provide preliminary advice on a suitable odorant for hydrogen. The research into the smell of three selected odorants THT, GASODOR® S-free and 2-hexyne, shows that the smell of all three odorants in hydrogen is comparable to the smell in natural gas. This applies to the perceptibility of the odors, the perceived odor strength and the perceived odor characteristics. The same dosage of odorant can be used for hydrogen as is required for natural gas. Based on the findings from the HyDelta program Work Package 2, it is not yet possible to make a choice for an odorant for hydrogen for both the short and the long term. The three odorants studied each have specific advantages and disadvantages. Some properties are not yet fully known. An important consideration will be whether the public recognizes and associates the odor with gas and whether the odor perception will lead to an action, such as turn off the gas supply. If the use of fuel cell applications should increase strongly and no cleaning is applied just before the fuel cell, the choice of odorant is not yet clear. THT seriously affects the performance of polymer fuel cells, GASODOR® S-free also adversely affects the performance and the influence of 2-hexyne is not yet known. Several properties of 2-hexyne for an odorant have not yet been tested and it has not yet been investigated whether this odorant can be produced in an economical way. For THT, the odorant that is already known to the public in the Netherlands, the alarming effect has already been proven and when fuel cells are only used very sporadically in the public gas supply and not all knowledge gaps can be filled in the short term, this seems to be the best choice for the first hydrogen projects in the public domain.

This paper presents results from a co-simulation based study to assess the interaction of electric vehicles (EVs) with the residential electricity distribution grid. The impact of this interaction on the grid as well as on the EV charging objectives is studied. The impact of EV charging strategies on the grid is measured in terms of deterioration of the quality of the grid voltage and overloading of the grid assets. The performance of the charging strategies from EV owner’s perspective is studied using metrics such as delay in charging and average cost of charging. The charging behavior of the EVs has been incorporated using models based on empirical data collected from public chargers in the Netherlands. A modern residential grid with high adoption of renewable resources is simulated using the co-simulation platform Mosaik which enables synchronized simulation of all the grid components along with a possibility to integrate external control signals.

This report D2.3 is part of HyDelta work package 2 “Odorization of hydrogen” and describes the long term stability of candidate odorants for hydrogen in a hydrogen gas matrix. Furthermore the current knowledge about the behaviour of odorant and hydrogen in a soil, compared to the behaviour of odorant and natural gas will be summarized. Also the current knowledge about possible de-mixing effects of odorant in hydrogen after a gas leakage will be summarised. Three candidate odorants, all selected in a previous phase, were tested for chemical stability in an atmosphere of 100 bar hydrogen over a three month test period by gas chromatographic analysis. All odorants THT, Gasodor® S-Free and 2-hexyn, were found to exhibit stable behavior, allowing them to exert their effect for a longer period of time. In the case of a gas leak from a mixture of an odorant in hydrogen, it behaves like a singular gas cloud and no separation of the odorant and hydrogen occurs. It is possible that the concentration of the mixture in space is not the same everywhere due to stratification, but this effect also applies to natural gas. With regard to the distribution of gas in a room and the smell of a gas leak, odorization of hydrogen is just as effective as odorization of natural gas. The behavior of an odorant in hydrogen in soil, which is important for examining how a gas leak in the soil behaves, will be reported in the final version of this report in mid-2022.

In this study, a mechanism is developed to support the distribution system operators (DSOs) with a better grid management scheme regarding congestion management by incorporating a data-driven congestion scheme and thus reducing the congestion. The objective of the work is to avoid/reduce the thermal overloading of the transformer with an affordable approach. A data-driven model is developed, which can help DSOs to solve congestion problems in the low-voltage (LV) distribution network. Demand response is applied for the procurement of flexibility, using available flexibility to mitigate the congestion in the distribution network. Once the congestion occurs, the DSO can refer to the data-driven classification model and mitigate the congestion with the minimised cost. A typical Dutch LV distribution network is considered for analysis. It is observed that the DSO has significant savings and reduction of congestion occurrence in the LV distribution network. The performance and accuracy of the developed data-driven model are also found to be well within satisfactory limits.

During the design phase of an offshore wind turbine, it is required to assess the impact of loads on the turbine life time. Due to the varying environmental conditions, the effect of various uncertain parameters has to be studied to provide meaningful conclusions. Incorporating such uncertain parameters in this regard is often done by applying binning, where the probability density function under consideration is binned and in each bin random simulations are run to estimate the loads. A different methodology for quantifying uncertainties proposed in this work is polynomial interpolation, a more efficient technique that allows to more accurately predict the loads on the turbine for specific load cases. This efficiency is demonstrated by applying the technique to a power production test problem and to IEC Design Load Case 1.1, where the ultimate loads are determined using BLADED. The results show that the interpolating polynomial is capable of representing the load model. Our proposed surrogate modeling approach therefore has the potential to significantly speed up the design and analysis of offshore wind turbines by reducing the time required for load case assessment.

Long, flexible wind turbine blades experience significant deflections during operation. Historically, the blade element momentum model in Bladed assumed that the blade is split into a set of radial aerodynamic sections which are aligned perpendicular to the pitch axis, and that any rotation of the sections due to deflection, pre-bend or pre-sweep in the blade can be ignored. For modern-day flexible rotor blades, under extreme loading conditions, this assumption no longer holds. Including this rotation when calculating inflow velocities and angle of attack, and when resolving the resultant forces at the element, causes a significant change in axial force (Fz) along the pitch axis, and therefore the blade out of plane bending moment (My). This in turn drives a change in overturning moments on the hub (which is driven by differences in bending moments between blades). An example 160m rotor shows an increase of 68% in hub overturning moment during an extreme gust event when aerofoil rotation due to deflection is included. This is verified through comparison to the alternative free vortex wake rotor model in Bladed. DNV GL Bladed includes the rotation of aerofoils by default at version 4.8.

Power transformers are valuable assets in the power network, with the primary function to regulate the transmission and distribution voltage. The regulating device is the tap changer which sets the turn ratio. Tap changer failure is one of the leading causes of high-voltage power transformer failure. Most tap changer failures are caused by degrading contacts. Contact degradation may be the result of contact wear or of arcing-induced carbon deposition during on-load-tap (OLT) changes. Contact degradation increases contact resistance, causing increased heating and arcing, eventually leading to possible failure of the power transformer. Proper maintenance, therefore, requires a diagnostic system which can assess the condition of the contacts. The research presented is aiming at automated defect recognition and localisation from measured dynamic resistance measurement patterns, for two types of tap changers, the 'Diverter Switch' type and the 'Selector Switch' type OLT changer.

Abstract Companies on the Norwegian continental shelf (NCS) have in recent years mainly focused on control of the integrity of technical barriers. Against the background of learning from incidents, verification and monitoring activities, both authorities and companies have seen the need to strengthen the work of the management of non-technical barriers. DNV GL and IFE have together with an NCS operator company developed a method to proactively capture factors that have impact on major accident risk in the organisation. The method monitors the use and maintenance of non-technical barriers against major accidents on three levels of management. It is pro-active, and strengthens the management's ability to identify and understand the subtle signals of weakening of non-technical barriers against major accidents. The method may be included in the existing management system; it is based on existing requirements and does not need new systems, resources or expertise. The testing on the three management levels showed that the method is relatively easy to learn, but using the method required understanding. Those who were involved seem relatively quickly to take ownership and see the usefulness of the method. The strength of the method is its ability to support the company's subject matter expertise to interpret ambiguous information, identify weak signals and assemble knowledge into information that can be used to assess the status of non-technical barriers. Based on this, the expertise can prioritize and highlight few and effective measures at all levels of the organization. On the basis of the good experience from the testing, the project recommends to implement the method in the organisation.

The present paper aims to simulate and reproduce the experiments on a imbalanced rotor with one blade off pitched by 20degees carried out within the IEA task 29 Mexnext Phase III. Models of increasing complexity were used (Blade Element Method simulation (BEM) lifting line with free vortex wake (FVW) and URANS CFD) and the results were compared. The rotor has a diameter of 4.5m and three different load cases corresponding to a tip speed ratio of 5.24, 7.6 and11.2 were chosen from the test matrix performed during the experiments. The rotor speed was kept constant at 324.9RPM. BEM and FVW simulations were performed using the Aero Module tool developed by ECN that offers both an advanced BEM formulation and a FVW formulation named AWSM. The commercial solver STARCCM+ was for the CFD simulations and an Unsteady RANS approach with the k-ra SST turbulence model was chosen. Loads recorded with strain gauges during the experiments and pressures on the equipped blades were compared with results from the numerical simulations. The comparison provided good agreement in the low tip speed ratio cases while differences were more noticeable for the highest tip speed ration load case.