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Airborne Wind Energy (AWE) concerns systems capable harvesting energy from the wind, offering an efficient alternative to traditional wind turbines by flying crosswind with a tethered airfoil. Such concepts involve a system more difficult to control than conventional wind turbines. These systems generally cannot be operated efficiently in very low wind conditions, necessitating intervention by launching and landing. In contrast to this approach, this paper proposes to continue flying holding patterns which minimize power consumption. Efficient holding patterns are determined by solving an optimal control problem. The model is specified as a set of differential algebraic equations and an approximation of the tether drag is taken into account. Finally, an evaluation in terms of energy is performed by means of statistical approach.

Airborne Wind Energy (AWE) concerns systems capable harvesting energy from the wind, offering an efficient alternative to traditional wind turbines by flying crosswind with a tethered airfoil. Such concepts involve a system more difficult to control than conventional wind turbines. These systems generally cannot be operated efficiently in very low wind conditions, necessitating intervention by launching and landing. In contrast to this approach, this paper proposes to continue flying holding patterns which minimize power consumption. Efficient holding patterns are determined by solving an optimal control problem. The model is specified as a set of differential algebraic equations and an approximation of the tether drag is taken into account. Finally, an evaluation in terms of energy is performed by means of statistical approach.

Measurements and calculations of the influence of temperature gradients on the partial pressures of the gas species in a cold-wall chemical-vapor-deposition reactor are presented. The experiments were performed at low pressures (300–500 Pa total pressure) and gas mixtures consisting of hydrogen, nitrogen, and tetrafluoromethane. The partial pressures were determined by Raman spectroscopy. The Soret effect (or thermal diffusion) has a large influence on the partial pressures of heavy gases in the vicinity of the heated wafer. In some cases a decrease in partial pressure of 20% compared to the inlet partial pressures was observed. Numerical calculations were performed to predict the behavior of the gas mixture. For mixtures under investigation the gas temperatures as well as the changes in partial pressures due to the Soret effect were predicted correctly.

Measurements and calculations of the influence of temperature gradients on the partial pressures of the gas species in a cold-wall chemical-vapor-deposition reactor are presented. The experiments were performed at low pressures (300–500 Pa total pressure) and gas mixtures consisting of hydrogen, nitrogen, and tetrafluoromethane. The partial pressures were determined by Raman spectroscopy. The Soret effect (or thermal diffusion) has a large influence on the partial pressures of heavy gases in the vicinity of the heated wafer. In some cases a decrease in partial pressure of 20% compared to the inlet partial pressures was observed. Numerical calculations were performed to predict the behavior of the gas mixture. For mixtures under investigation the gas temperatures as well as the changes in partial pressures due to the Soret effect were predicted correctly.

The plug-in hybrid electric vehicle allows vehicle propulsion from multiple internal power sources. Electric energy from the grid can be utilized by means of the plug-in connection. An on-line energy management (EM) strategy is proposed to minimize the costs for taking energy from each power source. Especially in a dynamical energy market, an on-line optimization algorithm is desirable since energy prices change over time. By construction, the proposed EM system can operate with, and without prediction information. If predictions are available, an electronic horizon is applied to anticipate on up-coming events and further optimize the strategy. Illustrative examples are given to explain the added value for both solutions. Also the situation where energy is transferred back to the grid is considered. © 2008 IEEE.

The plug-in hybrid electric vehicle allows vehicle propulsion from multiple internal power sources. Electric energy from the grid can be utilized by means of the plug-in connection. An on-line energy management (EM) strategy is proposed to minimize the costs for taking energy from each power source. Especially in a dynamical energy market, an on-line optimization algorithm is desirable since energy prices change over time. By construction, the proposed EM system can operate with, and without prediction information. If predictions are available, an electronic horizon is applied to anticipate on up-coming events and further optimize the strategy. Illustrative examples are given to explain the added value for both solutions. Also the situation where energy is transferred back to the grid is considered. © 2008 IEEE.

In this paper, we propose using marginal emission factors instead of average emission factors for determining the impact of adding variable renewable electricity to the generation mix. Average emission factors assume constant emissions over time, which does not reflect reality. Therefore, they cannot be used for e.g. accurately determining the mitigated CO2 emissions by renewables, or for scheduling shiftable loads in order to have the lowest CO2 emissions. To solve this, we provide a method to construct the marginal emission profiles via the merit order and demonstrate the method by composing these for the case of the Netherlands. Using this method, we re-evaluate the CO2 impact in 2014 of photovoltaic-generated electricity to be 0.42 Mt - compared to 0.36 Mt using the average emission factor - and for wind-generated electricity to be 3.6 Mt instead of 2.9 Mt CO2 (an increase of 14.3% and 24.2%, respectively). Furthermore, we show the impact of CO2 price on the merit order and show that even high CO2 prices of 50 to 75 €/tCO2 are not sufficient to phase-out new coal-fired power plants.

In this paper, we propose using marginal emission factors instead of average emission factors for determining the impact of adding variable renewable electricity to the generation mix. Average emission factors assume constant emissions over time, which does not reflect reality. Therefore, they cannot be used for e.g. accurately determining the mitigated CO2 emissions by renewables, or for scheduling shiftable loads in order to have the lowest CO2 emissions. To solve this, we provide a method to construct the marginal emission profiles via the merit order and demonstrate the method by composing these for the case of the Netherlands. Using this method, we re-evaluate the CO2 impact in 2014 of photovoltaic-generated electricity to be 0.42 Mt - compared to 0.36 Mt using the average emission factor - and for wind-generated electricity to be 3.6 Mt instead of 2.9 Mt CO2 (an increase of 14.3% and 24.2%, respectively). Furthermore, we show the impact of CO2 price on the merit order and show that even high CO2 prices of 50 to 75 €/tCO2 are not sufficient to phase-out new coal-fired power plants.