D.K. Sidiras

Solar systems diffusion in local markets

Abstract This paper reports on a study of the driving forces and barriers of the spectacular diffusion of solar energy use for domestic hot-water production in Greece. Through the various kinds of questionnaires used in this work, the main diffusion actors have been requested to grade the various diffusion factors identified by desk and preliminary field research. Households identify a number of economic (available family income), technical (new technologies), political (new incentives), and socio-cultural (sensitivity in energy matters) factors as dominant. According to the solar industry, advertising, distribution and quality control standards have to be added to the list of critical factors. Technical experts contribute with identifying, besides R&D, public awareness on energy matters. Solar collector diffusion, despite the fact that it has followed a market-driven mechanism, was revealed to be a multi-actor, multi-dimensional and multi-parametric phenomenon. Presently, the phenomenon is constrained by the available family income, with technology-related factors, i.e., research, and standardization quality control, playing increasing roles.

Acid saccharification of ball-milled straw

Abstract The effect of ball milling on the rate and selectivity of dilute acid saccharification of barley straw was investigated. Cellulose crystallinity as well as the formation of intermediate soluble oligosaccharides were shown to play major roles in hydrolysis of pretreated lignocellulose. Experimental results were successfully fitted by a proposed four-step kinetic model to describe the reaction system; the values of the required eight kinetic parameters are independent of the degree of the pretreatment. Due to crystallinity reduction by ball milling, saccharification of more than 50% of straw cellulose with minimal glucose degradation becomes possible at mild hydrolytic conditions.

Utilization of magnetically responsive cereal by-product for organic dye removal.

BACKGROUND Barley straw, an agricultural by-product, can also serve as a low-cost and relatively efficient adsorbent of various harmful compounds. In this case, adsorption of four water-soluble dyes belonging to different dye classes (specifically Bismarck brown Y, representing the azo group; methylene blue, quinone-imine group; safranin O, safranin group; and crystal violet, triphenylmethane group) on native and citric acid-NaOH-modified barley straw, both in magnetic and non-magnetic versions, was studied. RESULTS The adsorption was characterized using three adsorption models, namely Langmuir, Freundlich and Sips. To compare the maximum adsorption capacities (qmax), the Langmuir model was employed. The qmax values reached 86.5-124.3 mg of dye per g of native non-magnetic straw and 410.8-520.3 mg of dye per g of magnetic chemically modified straw. Performed characterization studies suggested that the substantial increase in qmax values after chemical modification could be caused by rougher surface of adsorbent (observed by scanning electron microscopy) and by the presence of higher amounts of carboxyl groups (detected by Fourier transform infrared spectroscopy). The adsorption processes followed the pseudo-second-order kinetic model and thermodynamic studies indicated spontaneous and endothermic adsorption. CONCLUSION The chemical modification of barley straw led to a significant increase in maximum adsorption capacities for all tested dyes, while magnetic modification substantially facilitated the manipulation with adsorbent.

Pillared Sn-MWW Prepared by a Solid-State-Exchange Method and its Use as a Lewis Acid Catalyst

Pillared Sn‐MWW (Sn‐MWW(SP)‐SSE) was prepared through a solid‐state‐exchange (SSE) route. The pillared structure was inherited from pillared B‐MWW, and Sn was inserted in the framework by boron leaching and solid‐state‐exchange with tin tetrachloride pentahydrate. The Sn‐MWW(SP)‐SSE with framework Sn sites exhibits Lewis acidity and good catalytic performance for the Baeyer–Villiger oxidation, and mono‐ and disaccharide isomerizations.

Wheat straw hydrolytic pretreatment using maleic acid to enhance ethanol production from sugars

The acid hydrolysis of wheat straw was studied using a batch reactor. The hydrolysis was catalyzed by 0.01-0.09 M maleic acid for 0-50 min at 140°C-180°C. The hydrolysis kinetics of cellulose and hemicelluloses were simulated by a new model incorporating the acidity of the liquid phase. Moreover, the pH and the temperature profile during the process were included using a new modified severity factor R0*. The model parameters were calculated using nonlinear regression analysis. Process parameters investigated herein include variation in temperature, acid concentration and pH. The optimum reaction conditions resulting to maximum sugars yield were estimated according to the proposed model. For log R0* = 1.971 (0.05 M maleic acid, 180°C, 25 min) up to 18.2% w/w total glucose on cellulose basis, 91.0% w/w total xylose on xylan basis and 44.4% w/w total sugars on polysaccharides basis were obtained. The monosaccharides and oligosaccharides produced can be fermented to bioethanol. [Received: January 14, 2016; Accepted: September 26, 2016]