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This study investigates the effect of aeration rate and feedstock density on the biodrying process to improve the quality of type 2 wet refuse-derived fuel. The aeration rate and feedstock density were varied to investigate these parameters’ effect on the system’s performance. The experiments used 0.3 m3 lysimeters with continuous negative ventilation and five days of operation. In Experiment A, aeration rates of 0.4, 0.5, and 0.6 m3/kg/day were tested with a feedstock bulk density of 232 kg/m3. In Experiment B, the optimum aeration rates determined in Experiment A (0.5 and 0.6 m3/kg/day) were used, and the feedstock density was varied (232 kg/m3, 250 kg/m3, and 270 kg/m3). The results showed that an aeration rate of 0.5 m3/kg/day was the most efficient for a feedstock density of 232 kg/m3; when the aeration rate was increased to 0.6 m3/kg/day, a feedstock density of 250 kg/m3 was the most effective. However, a feedstock density of 270 kg/m3 was not found to be practical for use in the quality improvement system. When the feedstock density is increased, the water in the feedstock and the water resulting from the biodegradation process cannot evaporate due to the feedstock layer’s low porosity, and the system requires an increased aeration rate. Furthermore, the increase in density scaled with increased initial volatile solid content, initial organic content, and initial moisture content, which significantly impacted the final moisture content based on multivariate regression analysis.

This study investigates the effect of aeration rate and feedstock density on the biodrying process to improve the quality of type 2 wet refuse-derived fuel. The aeration rate and feedstock density were varied to investigate these parameters' effect on the system's performance. The experiments used 0.3 m³ lysimeters with continuous negative ventilation and five days of operation. In Experiment A, aeration rates of 0.4, 0.5, and 0.6 m³/kg/day were tested with a feedstock bulk density of 232 kg/m³. In Experiment B, the optimum aeration rates determined in Experiment A (0.5 and 0.6 m³/kg/day) were used, and the feedstock density was varied (232 kg/m³, 250 kg/m³, and 270 kg/m³). The results showed that an aeration rate of 0.5 m³/kg/day was the most efficient for a feedstock density of 232 kg/m³; when the aeration rate was increased to 0.6 m³/kg/day, a feedstock density of 250 kg/m³ was the most effective. However, a feedstock density of 270 kg/m³ was not found to be practical for use in the quality improvement system. When the feedstock density is increased, the water in the feedstock and the water resulting from the biodegradation process cannot evaporate due to the feedstock layer's low porosity, and the system requires an increased aeration rate. Furthermore, the increase in density scaled with increased initial volatile solid content, initial organic content, and initial moisture content, which significantly impacted the final moisture content based on multivariate regression analysis. [ABSTRACT FROM AUTHOR]

Abstract: We propose a method, Temperature Integration, which allows an efficient calculation of free energy differences between two systems of interest, with the same degrees of freedom, which may have rough energy landscapes. The method is based on calculating, for each single system, the difference between the values of at two temperatures, using a Parallel Tempering procedure. If our two systems of interest have the same phase space volume, they have the same values of at high- , and we can obtain the free energy difference between them, using the two single-system calculations described above. If the phase space volume of a system is known, our method can be used to calculate its absolute (versus relative) free energy as well. We apply our method and demonstrate its efficiency on a “toy model” of hard rods on a 1-dimensional ring. [Copyright &y& Elsevier]

Early production and high energy efficiency are important in greenhouse vegetable production in cold regions. A dynamic temperature integration strategy with low pre-night temperature (PNT) has been developed to reduce energy consumption and to improve early fruit yield and energy use efficiency. However, the application of this temperature control strategy is feasible only if there is no crop yield and quality loss. To determine the low PNT tolerance threshold and explore the mechanism of this temperature control strategy on plant growth and development, the effects of four PNT temperature integration treatments (PNT9, PNT11, PNT13, and PNT15, with an actual PNT of 9.4, 11.3, 13.3, and 15.1 °C, respectively) on greenhouse tomatoes (Solanum lycopersicum) were investigated. The PNT was applied at the beginning of the night for 3 h, whereas temperatures in other periods during a day (24 h) were adjusted accordingly to ensure the same 24-h average temperature (19.4 °C) for all PNT treatments. Four cultivars (Bigdena, Clarance, Quest, and Conchita), representing all three types (beefsteak, cluster, and cherry) of greenhouse tomatoes, were used in the study. The optimum PNT for fruit yield was 13.8 and 14.9 °C for 'Bigdena' and 'Conchita', respectively. Low PNT down to 11 °C did not compromise fruit yield and plant development in 'Clarance', and thus a PNT lower than 13 °C can be used for 'Clarance' if it does not have a negative effect on fruit quality. In 'Bigdena' and 'Conchita', the above-ground biomass increased with increasing PNT at the low range of PNT, peaked at ≈13 °C PNT (13.7 and 13 °C for 'Bigdena' and 'Conchita', respectively), then declined at high PNT. Leaf photosynthesis rates were increased by the highest PNT (PNTI5), whereas respiration rates were reduced by the lowest PNT (PNT9). Therefore, PNT at ≈13 °C might have allowed for the proper balance between the high photosynthesis for photoassimilate generation and the low respiration for photoassimilate conservation and thus accumulated the highest photoassimilate and the highest fruit yield in 'Bigdena'. Flower development rate in 'Conchita' decreased linearly with low PNT, which might hare limited the response of its fruit yield to low PNT and raised the optimum PNT for fruit yield to 14.9 °C. Temperature integration with proper low PNT can be an effective climate control strategy for increasing early fruit yield and energy use efficiency in greenhouse tomato production. [ABSTRACT FROM AUTHOR]

Abstract: Earlier, different dynamic greenhouse climate regimes were designed with various aims as energy saving, biocide reduction or reduction of chemical growth retardants that are used for quality improvement. The aim of this research was to create a decision support tool in order to decide at which week of the year to use which climate control regime for the optimal gain of sustainability and plant quality. A combined greenhouse climate and control model was used to analyse separate and combined effects of six different regimes with increasing degrees of freedom for various climate variables. In this simulation study the model crop cut chrysanthemum was used. Temperature integration, dynamic humidity control, and negative DIF regimes were adapted from earlier papers (DIF=difference between average day and average night temperature, reduces the use of chemical growth regulators). Temperature integration with a regular 24-h averaging period (TI24) and with two nested temperature averaging periods 24h and 6 days (TIn, subscript ‘n’ for nested), and combinations of TI24 and TIn with the DIF concept ( and , respectively) to control stem elongation were simulated. TI24 and TIn were also combined with a dynamic humidity control. All strategies were compared to a standard climate regime (BP, blueprint). The best choice of regimes regarding energy saving, plant quality and reductions of the use of chemicals was targeted for different seasons. In winter absolute energy saving compared to BP was highest when a DIF regime was applied, and the energy saving increased with decreasing DIF set point. In relative sense the largest energy saving can be obtained with TIn (51% in a 4-week period), in spring or autumn (and then with TI24 and the DIF regimes). In these seasons, however, or should be used to reduce chemical growth regulators. The decision whether to use TIn, TI24, or a DIF regime was therefore a decision between energy saving or saving of chemicals. The tool developed in this paper can be used to quantify the costs in energy or chemicals when using the one or other strategy. [Copyright &y& Elsevier]

Modern greenhouses in The Netherlands are designed for efficient use of energy. Climate control traditionally aims at optimal crop performance. However, energy saving is a major issue for the development of new temperature regimes. Temperature integration (TI) results in fluctuating and often high relative humidity (RH) levels in modern, highly insulated greenhouses. At high temperature, water vapour pressure deficit (VPD) is usually high and RH consequently low and vice versa. Relatively low fixed set points (80–85% RH) for air humidity as is common practice, may strongly influence the efficiency of TI, because heating and/or ventilation actions are required to control humidity rather than temperature. This requires much energy. Fluctuating RH may affect crop performance in several ways. Too low VPD may reduce growth due to low transpiration and associated physiological disorders. Water vapour pressure above the dew point leads to condensation on the relative cooler plant tissue and this may give rise to diseases. High VPD, on the other hand, may induce high stomatal resistance and plant water stress (PWS). The aim of the present research was the design of a process-based humidity control concept for a reference cut chrysanthemum crop cultivated with TI. RH control set points were generated as function of underlying processes. Greenhouse performance with this humidity regime and different temperature regimes were simulated with respect to greenhouse climate, energy consumption and photosynthesis. Compared with a fixed 80% RH set point, annual energy consumption of a year-round cut chrysanthemum cultivation could be reduced by 18% for TI with ±2 °C temperature bandwidth as well as for regular temperature control. For separate 12 week cultivations with planting date 1 March, energy saving could increase up to 27 or 23% for TI and regular temperature control, respectively. [Copyright &y& Elsevier]

The ability of crops to tolerate temperature deviations from the average set point could play an important role in energy saving greenhouse climate regimes. This principle is used in the so called temperature integration procedure, which is based on empirical knowledge and uses fixed maximum and minimum temperatures. More dynamic flexible boundaries depending on the underlying crop processes would probably increase the potential for energy saving in greenhouses. Therefore, our aim was to improve the temperature integration concept by introducing dynamic temperature constraints. Processes with a fast temperature response (e.g. photosynthesis or stress) were decoupled from developmental processes with a slow response time. A modified temperature integration procedure was designed combining the usual long-term integration over several days and fixed boundaries for daily average temperature with short-term integration over 24 h with flexible temperature limits. Because the optimum temperature for canopy photosynthesis rises with increasing concentration of atmospheric CO2, this aspect was included in ventilation control. Because plants react not only to extreme temperatures but also to their duration, a dose concept was applied to stress-related temperature constraints. The desired mean temperature for the subsequent 24 h was calculated once in 24 h. Within this 24 h cycle, temperature set points for heating and ventilation were optimised in relation to the fast crop processes. The temperature regime was tested by simulations. Greenhouse climate, energy consumption and dry matter increase were simulated for complete years and different parameter settings for tomato as model crop. With the modified regime compared with regular temperature integration, with the same ±2 °C long-term temperature bandwidth 4.5% (normal secure settings) or up to 9% (extreme settings) more energy could be saved (on a yearly basis). Crop gross photosynthesis could increase by approximately 2.5%. [Copyright &y& Elsevier]