This paper investigates the effects of intermittent solar and wind power generation on electricity price formation in Germany. We use daily data from 2010 to 2015, a period with profound modifications in the German electricity market, the most notable being the rapid integration of photovoltaic and wind power sources, as well as the phasing out of nuclear energy. In the context of a GARCH-in-Mean model, we show that both solar and wind power Granger cause electricity prices, that solar power generation reduces the volatility of electricity prices by scaling down the use of peak-load power plants, and that wind power generation increases the volatility of electricity prices by challenging electricity market flexibility.JEL classification: C22; Q41; Q42.

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A kinetic model for glucose and xylose co-substrate uptake in Saccharomyces cerevisiae is presented. The model couples the enzyme kinetics with the glucose-dependent genetic expression of the individual transport proteins. This novel approach implies several options for optimizing the co-substrate utilization. Interestingly, the simulations predict a maximum xylose uptake rate at a glucose concentration >0 g/L, which suggests that the genetic expressions of the considered transport proteins are of importance when optimizing the xylose uptake. This was also evident in fed-batch simulations, where a distinct optimal glucose addition rate >0 g/L x h was found. Strategies for improving the co-substrate utilization by genetic engineering of the transport systems are furthermore suggested based on simulations.

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