Equilibrium supply security in a multinational electricity market with renewable production

An increasing reliance on solar and wind power has raised concern about system ability to consistently satisfy electricity demand. This paper examines countries' unilateral incentives to achieve supply security through capacity reserves and market integration in a multinational electricity market. Capacity reserves protect consumers against blackouts and extreme prices, but distort consumption and investment. Market integration alleviates supply constraints, but requires costly network reinforcement. Capacity reserves can be up- or downward distorted, but network investment is always insufficient in equilibrium. Capacity reserves are smaller when there are financial markets or when dispatched solely to resolve domestic supply constraints

Central- versus Self-Dispatch in Electricity Markets

In centralized markets, producers submit detailed cost data to the dayahead market, and the market operator decides how much should be produced in each plant. This differs from decentralized markets that rely on self-commitment and where producers send less detailed cost information to the operator of the day-ahead market. Ideally centralized electricity markets would be more effective, as they consider more detailed information, such as start-up costs and no-load costs. On the other hand, the bidding format is rather simplified and does not allow producers to express all details in their costs. Moreover, due to uplift payments, producers have incentives to exaggerate their costs. As of today, US has centralized wholesale electricity markets, while most of Europe has decentralized wholesale electricity markets. The main problem with centralized markets in US is that they do not provide intra-day prices which can be used to continuously up-date the dispatch when the forecast for renewable output changes. Intra-day markets are more flexible and better adapted to deal with renewable power in decentralized markets. Iterative intra-day trading in a decentralized market can also be used to sort out coordination problems related to non-convexities in the production. The downside of this is that increased possibilities to coordinate increase the risk of getting collusive outcomes. Decentralized day-ahead markets in Europe can mainly be improved by considering network constraints in more detail

A mitochondrial half-size ABC transporter is involved in cadmium tolerance in Chlamydomonas reinhardtii

Five cadmium-sensitive insertional mutants, all affected at the CDS1 ('cadmium-sensitive 1') locus, have been previously isolated in the unicellular green alga Chlamydomonas reinhardtii. We here describe the cloning of the Cds1 gene (8314 bp with 26 introns) and the corresponding cDNA. The Cds1 gene, strongly induced by cadmium, encodes a putative protein (CrCds1) of 1062 amino acid residues that belongs to the ATM/HMT subfamily of half-size ABC transporters. This subfamily includes both vacuolar HMT-type proteins transporting phytochelatin-cadmium complexes from the cytoplasm to the vacuole and mitochondrial ATM-type proteins involved in the maturation of cytosolic Fe/S proteins. Unlike the Delta sphmt1 cadmium-sensitive mutant of Schizosaccharomyces pombe that lacks a vacuolar HMT-type transporter, the cds1 mutant accumulates a high amount of phytochelatin-cadmium complexes. By epitope tagging, the CrCds1 protein was localized in the mitochondria. Even though mitochondria of cds1 do not accumulate important amounts of 'free' iron, the mutant cells are hypersensitive to high iron concentrations. Our data show for the first time that a mitochondrial ATM-like transporter plays a major role in tolerance to cadmium.Peer reviewe

Optimization of acidic extraction of astaxanthin from Phaffia rhodozyma *

Optimization of a process for extracting astaxanthin from Phaffia rhodozyma by acidic method was investigated, regarding several extraction factors such as acids, organic solvents, temperature and time. Fractional factorial design, central composite design and response surface methodology were used to derive a statistically optimal model, which corresponded to the following optimal condition: concentration of lactic acid at 5.55 mol/L, ratio of ethanol to yeast dry weight at 20.25 ml/g, temperature for cell-disruption at 30 °C, and extraction time for 3 min. Under this condition, astaxanthin and the total carotenoids could be extracted in amounts of 1294.7 μg/g and 1516.0 μg/g, respectively. This acidic method has advantages such as high extraction efficiency, low chemical toxicity and no special requirement of instruments. Therefore, it might be a more feasible and practical method for industrial practice

Grx5 Is a Mitochondrial Glutaredoxin Required for the Activity of Iron/Sulfur Enzymes

Yeast cells contain a family of three monothiol glutaredoxins: Grx3, 4, and 5. Absence of Grx5 leads to constitutive oxidative damage, exacerbating that caused by external oxidants. Phenotypic defects associated with the absence of Grx5 are suppressed by overexpression of SSQ1 and ISA2, two genes involved in the synthesis and assembly of iron/sulfur clusters into proteins. Grx5 localizes at the mitochondrial matrix, like other proteins involved in the synthesis of these clusters, and the mature form lacks the first 29 amino acids of the translation product. Absence of Grx5 causes: 1) iron accumulation in the cell, which in turn could promote oxidative damage, and 2) inactivation of enzymes requiring iron/sulfur clusters for their activity. Reduction of iron levels in grx5 null mutants does not restore the activity of iron/sulfur enzymes, and cell growth defects are not suppressed in anaerobiosis or in the presence of disulfide reductants. Hence, Grx5 forms part of the mitochondrial machinery involved in the synthesis and assembly of iron/sulfur centers