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The core objective of this work was to take advantage of the unexploited wheat straw biomass, currently considered as a broadly available waste stream from the Greek agricultural sector, towards the integrated valorization of sugar streams for the microbial production of polyunsaturated omega-3 fatty acids (PUFAs). The OxiOrganosolv pretreatment process was applied using acetone and ethanol as organic solvents without any additional catalyst. The results proved that both celluloserich solid pulp and hemicellulosic oligosaccharides-rich aqueous liquid fraction after pretreatment can be efficiently hydrolyzed enzymatically, thus resulting in high yields of fermentable monosaccharides. The latter were supplied as carbon sources to the heterotrophic microalga Crypthecodinium cohnii for the production of PUFAs, more specifically docosahexaenoic acid (DHA). The solid fractions consisted mainly of hexose sugars and led to higher DHA productivity than their pentose-rich liquid counterparts, which can be attributed to the different carbon source and C/N ratio in the two streams. The best performance was obtained with the solid pulp pretreated with ethanol at 160 °C for 120 min and an O2 pressure of 16 bar. The total fatty acids content reached 70.3 wt% of dried cell biomass, of which 32.2% was DHA. The total DHA produced was 7.1 mg per g of untreated wheat straw biomass. [ABSTRACT FROM AUTHOR]

The penetration of distributed energy resources (DER), including distributed generators and flexible demand, is increasing worldwide and is expected to increase further encouraged by environmental policies and decreasing costs. Due to their large number and spatial dispersion, DER's effective integration into the operation of electricity markets is a complex and demanding task. Moreover, their relatively small size makes their direct individual participation in the electricity market, although theoretically possible, highly impractical. This paper aims to quantify the benefits of the aggregated participation of DER in the electricity market via a DER Aggregator. The DER Aggregator's interactions with his customers and with the wholesale market are modeled as a bilevel programming problem: the upper level describes the DER Aggregator decision-making; the lower level encompasses the DERs’ decision model and the market clearing process. Several scenarios are examined in order to draw general conclusions regarding the conditions under which DER aggregation is beneficial for DER owners and the aggregator. [ABSTRACT FROM PUBLISHER]

This paper presents a bilevel model for describing the interdependence of decisions between a retailer/aggregator and the distributed resources owners that the former serves and represents. Decision making is performed in a hierarchical fashion. The retailer performs the energy management of various resources indirectly; price signals are used as incentives for inducing the entities owning the distributed resources in a behavior that optimizes the operation and economic profit of the microgrid that they compose. The two-level interaction is formulated mathematically as a mathematical programming problem with complementarity constraints, while nonlinearities are replaced by equivalent linear expressions. The results of a characteristic case study indicate the efficiency and scalability of the proposed model. [ABSTRACT FROM PUBLISHER]

This paper presents the application of bilevel programming for analyzing competitive situations of hierarchical decision making between an Energy Services Provider representing several microgrids (MGs)—each one comprising controllable loads and dispatchable distributed generation units—and a large central production unit. The rules of the interaction between the two entities are determined in a bilateral contract. This operation is compared to the vertically integrated operation of this system, i.e., only one entity manages both the central production unit and the distributed resources of the MG. This comparison highlights the benefits of applying a two level structure in the simulated interaction. [ABSTRACT FROM PUBLISHER]

Salinity is a major limiting factor in crop productivity worldwide. Medicago sativa L. is an important fodder crop, broadly cultivated in different environments, and it is moderately tolerant of salinity. Medicago arborea L. is considered a stress-tolerant species and could be an important genetic resource for the improvement of M. sativa's salt tolerance. The aim of the study was to evaluate the seedling response of M. sativa, M. arborea, and their hybrid (Alborea) to salt shock and salt stress treatments. Salt treatments were applied as follows: salt stress treatment at low dose (50 mM NaCl), gradual acclimatization at 50–100 and 50–100–150 mM NaCl, and two salt shock treatments at 100 and 150 mM NaCl. Growth rates were evaluated in addition to transcriptional profiles of representative genes that control salt uptake and transport (NHX1 and RCI2A), have an osmotic function (P5CS1), and participate in signaling pathways and control cell growth and leaf function (SIMKK, ZFN, and AP2/EREB). Results showed that the studied population of M. sativa and M. arborea performed equally well under salt stress, whereas that of M. sativa performed better under salt shock. The productivity of the studied population of Alborea exceeded that of its parents under normal conditions. Nevertheless, Alborea was extremely sensitive to all initial salt treatments except the low dose (50 mM NaCl). In addition, significantly higher expression levels of all the studied genes were observed in the population of M. arborea under both salt shock and salt stress. On the other hand, in the population of M. sativa, NHX1, P5CS1, and AP2/EREB were highly upregulated under salt shock but to a lesser extent under salt stress. Thus, the populations of M. sativa and M. arborea appear to regulate different components of salt tolerance mechanisms. Knowledge of the different parental mechanisms of salt tolerance could be important when incorporating both mechanisms in Alborea populations. [ABSTRACT FROM AUTHOR]