The Forum: Fall 2005

Fall 2005 journal of the Honors Program at the University of North Dakota. The issue includes stories, poems, essays and art by undergraduate students.https://commons.und.edu/und-books/1058/thumbnail.jp

Variability in large-scale wind power generation

The paper demonstrates the characteristics of wind power variability and net load variability in multiple power systems based on real data from multiple years. Demonstrated characteristics include probability distribution for different ramp durations, seasonal and diurnal variability and low net load events. The comparison shows regions with low variability (Sweden, Spain and Germany), medium variability (Portugal, Ireland, Finland and Denmark) and regions with higher variability (Quebec, Bonneville Power Administration and Electric Reliability Council of Texas in North America; Gansu, Jilin and Liaoning in China; and Norway and offshore wind power in Denmark). For regions with low variability, the maximum 1?h wind ramps are below 10% of nominal capacity, and for regions with high variability, they may be close to 30%. Wind power variability is mainly explained by the extent of geographical spread, but also higher capacity factor causes higher variability. It was also shown how wind power ramps are autocorrelated and dependent on the operating output level. When wind power was concentrated in smaller area, there were outliers with high changes in wind output, which were not present in large areas with well-dispersed wind power

Changes in leaf and thylakoid membrane lipids during low-temperature adaptation of winter barley (Hordeum vulgare L.)

Frost-resistant winter cereals actively adapt the fluidity of their membranes to decreasing temperatures. We have attempted to study the membrane lipid changes that are responsible for this adaptation. In the total leaf lipids of winter barley plants (Hordeum vulgare L.) 3 weeks' growth at low temperature (4 °C) decreased the number of double bonds per lipid molecule in all lipid classes extracted from leaves. However, there were only minor changes in the degree of fatty acid unsaturation in the lipids of barley thylakoid membranes during this treatment. In contrast, a significant increase in the lipid/protein ratio was observed in cold-adapted thylakoids when compared with control plants. This cold-induced increase in the lipid/protein ratio seems to act as an adaptive mechanism to maintain fluid membranes despite lower growth temperatures. Cold-hardening also caused a marked increase of the total polar lipids of leaves relative to chlorophyll; this was particularly pronounced for the phospholipids, indicating that the adaptation to low growth temperatures could also be associated with accumulation of extra-chloroplastic material in the cells. © 1984 Oxford University Press.SCOPUS: ar.jinfo:eu-repo/semantics/publishe