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This paper presents a stochastic factor based approach to mid-term modeling of spot prices in deregulated electricity markets. The fundamentals affecting the spot price are modeled independently and a market equilibrium model combines them to form spot price. Main advantage of the model is the transparency of the generated prices because each underlying factor and the dynamics between factors can be modeled and studied in detail. Paper shows realistic numerical examples on the forerunner Scandinavian electricity market. The model is used to price an exotic electricity derivative.

Abstract Algae have been considered as a promising biodiesel feedstock. One of the major factors affecting large-scale algae technology application is poor wintering cultivation performance. In this study, an integrated approach is investigated combining freshwater microalgae Chlorella zofingiensis wintering cultivation in pilot-scale photobioreactors with artificial wastewater treatment. Mixotrophic culture with the addition of acetic acid (pH-regulation group) and autotrophic culture (control group) were designed, and the characteristics of algal growth, lipid and biodiesel production, and nitrogen and phosphate removal were examined. The results showed that, by using acetic acid three times per day to regulate pH at between 6.8 and 7.2, the total nitrogen (TN) and total phosphate (TP) removal could be increased from 45.2% to 73.5% and from 92.2% to 100%, respectively. Higher biomass productivity of 66.94 mg L−1 day−1 with specific growth rate of 0.260 day−1 was achieved in the pH-regulation group. The lipid content was much higher when using acetic acid to regulate pH, and the relative lipid productivity reached 37.48 mg L−1 day−1. The biodiesel yield in the pH-regulated group was 19.44% of dry weight, with 16–18 carbons as the most abundant composition for fatty acid methyl esters. The findings of the study prove that pH adjustment using acetic acid is efficient in cultivating C. zofingiensis in wastewater in winter for biodiesel production and nutrient reduction.

This paper presents an optimal control strategy for a district heating power plant with thermal energy storage. The main goal of the control strategy is to reduce the operation costs of the power plant, by scheduling the boilers, the operation of the thermal energy storage and the curtailment on the loads. The problem is stated as a constrained optimization in the form of a Mixed Integer Linear Program (MILP), embedded on an Model Predictive Control (MPC) framework. Particular attention is paid to modeling of boilers operating constraints, including the outlet water flow temperature, to the energy exchanged with the thermal energy storage and to the operating modes of the power plant layout, including the constraints related to the supply water temperature needed from the network. The results are performed using the data and the layout of the power plant located in the city of Ylivieska, in Finland. The cost analysis performed shows the advantages of using the predictive control strategy.

Meteorological forcing at the air-water interface is the main determinant of the heat balance of most lakes (Edinger et al., 1968; Sweers, 1976). Year-to-year changes in the weather therefore have a major effect on the thermal characteristics of lakes. However, lakes that differ with respect to their morphometry respond differently to these changes (Gorham, 1964), with deeper lakes integrating the effects of meteorological forcing over longer periods of time. Other important factors that can influence the thermal characteristics of lakes include hydraulic residence time, optical properties and landscape setting (e.g. Salonen et al., 1984; Fee et al., 1996; Livingstone et al., 1999). These factors modify the thermal responses of the lake to meteorological forcing (cf. Magnuson et al., 2004; Blenckner, 2005) and regulate the patterns of spatial coherence (Chapter 17) observed in the different regions (Livingstone, 1993; George et al., 2000; Livingstone and Dokulil, 2001; Jarvinen et al., 2002; Blenckner et al., 2004)

A procedure for the design of an aerobic cometabolic process for the on-site degradation of chlorinated solvents in a packed bed reactor was developed using groundwater from an aquifer contaminated by trichloroethylene (TCE) and 1,1,2,2-tetrachloroethane (TeCA). The work led to the selection of butane among five tested growth substrates, and to the development and characterization from the site's indigenous biomass of a suspended-cell consortium capable to degrade TCE (first order constant: 96 L gprotein(-1) day(-1) at 30 °C and 4.3 L gprotein(-1) day(-1) at 15 °C) with a 90 % mineralization of the organic chlorine. The consortium immobilization had strong effects on the butane and TCE degradation rates. The microbial community structure was slightly changed by a temperature shift from 30 to 15 °C, but remarkably affected by biomass adhesion. Given the higher TCE normalized degradation rate (0.59 day(-1) at 15 °C) and attached biomass concentration (0.13 gprotein Lbioreactor(-1) at 15 °C) attained, the porous ceramic carrier Biomax was selected as the best option for the packed bed reactor process. The low TeCA degradation rate exhibited by the developed consortium suggested the inclusion of a chemical pre-treatment based on the TeCA to TCE conversion via β-elimination, a very fast reaction at alkaline pH. To the best of the authors' knowledge, this represents the first attempt to develop a procedure for the development of a packed bed reactor process for the aerobic cometabolism of chlorinated solvents.

The growing concern on global warming has pushed to set ambitious targets of carbon neutrality or net zero at the water sector. Meanwhile, poor data availability has been reported to restrict the national assessment of climate impacts and mitigation strategies in water sector. In national greenhouse gas (GHG) inventories, water sector is embedded in other sectors' emissions making it difficult to monitor separately. This study presents a national scale evaluation of climate change impacts for water sector in Finland based on life cycle analysis (LCA). In addition, the effectiveness of currently available emission reduction measures is evaluated by scenario analysis until the year 2035. According to the results, the life cycle climate change impacts from the Finnish municipal water sector were 0,67 (0,46-0,88) million tonnes CO2-eq./year (142.8 (98.9-187.1) kg CO2-eq./person/year). Drinking water services accounted for 12.5-13.9 % and wastewater services 86.1-87.4 % of the total emissions. With currently feasible emission reduction measures, the climate change impacts could be reduced approximately 14-30 % in total by 2035. The aim of carbon neutrality in the water sector was found to be unrealistic to achieve with existing and currently feasible measures for Finland and thus significant new emission mitigation measures are needed. The vague definition of carbon neutrality and system boundary of water sector as well as the uncertainties related to the assessment of direct emissions, undermine the credibility of the ambitiously set target. Prioritizing emission offsets to reach the target may inadvertently lead to unintended negative consequences due to the limitations and incompleteness of offset methods.

Reduction of greenhouse gas emissions and mitigation of climate change are the main aims of the global climate policy. Increased use of renewable energy is a central measure in achieving these goals. However, mitigation of climate change through increased use of renewable energy also has negative environmental impacts. Focusing merely on greenhouse gas emissions may lead to overseeing these other negative environmental impacts and thereby in unwanted side-effects. The aim of this review was to assess the overall life cycle impacts related to the production and use of the different renewable energy sources. Impacts were assessed for unit processes and for the Finnish national renewable energy targets as a whole. The review points out that in order to comprehensively understand the overall environmental impacts of the different renewable energy sources, a thorough life cycle assessment with a unified framework would be needed. Presently there is only limited information available or the published results are not comparable with each another. However, assessment using the Finnish National Renewable Energy Targets for 2020 also indicates that under the present targets, the overall environmental impacts of the renewable energy use are likely to be low. Main impacts or risks of impacts relate to the use of forest energy.