Decentralized energy supply and electricity market structures

Small decentralized power generation units (DG) are politically promoted because of their potential to reduce GHG-emissions and the existing dependency on fossil fuels. A long term goal of this promotion should be the creation of a level playing field for DG and conventional power generation. Due to the impact of DG on the electricity grid infrastructure, future regulation should consider the costs and benefits of the integration of decentralized energy generation units. Without an adequate consideration, the overall costs of the electricity generation system will be unnecessarily high. The present paper analyses, based on detailed modelling of decentralized demand and supply as well as of the overall system, the marginal costs or savings resulting from decentralized production. Thereby particular focus is laid on taking adequately into account the stochasticity both of energy demand and energy supply. An efficient grid pricing system should then remunerate long-term grid cost savings to operators of decentralized energy production or/and charge long-term additional grid costs to these operators. With detailed models of decentralized demand and supply as well as the overall system, the marginal costs or savings resulting from decentralized production are determined and their dependency on characteristics of the grid and of the decentralized supply are discussed.electricity markets, decentralized power production, demand side management

Modelling the impact of different permit allocation rules on optimal power plant portfolios

The electricity generation mix of many European countries is strongly dominated by fossil fuelled power plants. Given that CO2-emissions are responsible for a major part of the anthropogenic greenhouse effect, emission trading has been introduced in the EU in 2005. Under the European emissions trading scheme (ETS), the emission quantities of major industry branches, most notably the electricity industry are capped and a system of tradable CO2 emission permits is established. Although the effects of emission trading on emissions, industry structure and investment had been analysed on beforehand by a number of models, the impact of rules for primary permit allocation has so far hardly been focused on. This was mostly seen as a distributional issue not affecting the efficiency of the market mechanism itself. However a closer look at the permit allocation rules shows that the number of permits allocated to new plants often depends on their fuel and technology (e. g. in Germany). This may consequently have distorting effects on market prices and investment decisions, which so far have been hardly investigated quantitatively. In order to analyse such effects, a mixed complimentary programming (MCP) model is developed, which allows to model investment incentives in the electricity sector. It takes into account major power generation technologies, emission constraints, endogenous investment allocation rules and price elasticity of demand. In particular also the time-varying structure of electricity demand is accounted for and the corresponding distinction of base- and peak-load technologies. The model is applied to the EU-27 focusing on the year 2015, i.e. on the third trading period, where so far no decision has been made on the allocation rules to be applied. From this analysis we derive the average market prices for emission allowances and electricity and the optimal power plant capacities under different allocation schemes. In a pure environmental perspective the auctioning of permits is expected to be a first-best solution, but it could endanger the competitiveness and the security of supply of the European Union. The reason for the latter is that the generation mix becomes biased in favour of gas fuelled plants, which are associated with the least specific CO2-emissions, but have to be imported to a large extent from politically unreliable regions like Russia or the Middle East. The results of our analysis however show that allocating emissions for free, based on expected full-load hours and fuel specifics, will lead to higher CO2-prices whilst the effect of securing supply is only limited. Also electricity prices will only be slightly lower, so that the contribution of free allocation schemes to economic competitiveness is also limited.climate protection, security of supply, emission trading, allocation of emission permits, electricity markets, power plant portfolio

The Summer of Hydrogen

Ground crew veterans at Kennedy Space Center still talk about what they call "the summer of hydrogen"-the long, frustrating months in 1990 when the shuttle fleet was grounded by an elusive hydrogen leak that foiled our efforts to fill the orbiter's external fuel tank. Columbia (STS-35) was on Launch Pad A for a scheduled May 30 launch when we discovered the hydrogen leak during - tanking. The external fuel tank is loaded through the orbiter. Liquid hydrogen flows through a 17-inch umbilical between the orbiter and the tank. During fueling, we purge the aft fuselage with gaseous nitrogen to reduce the risk of fire, and we have a leak-detection system in the mobile launch platform, which samples (via tygon tubing) the atmosphere in and around the vehicle, drawing it down to a mass spectrometer that analyzes its composition. When we progressed to the stage of tanking where liquid hydrogen flows through the vehicle, the concentration of hydrogen approached four percent-the limit above which it would be dangerously flammable. We had a leak. We did everything we could think of to find it, and the contractor who supplied the flight hardware was there every day, working alongside us. We did tanking tests, which involved instrumenting the suspected leak sources, and cryo-loaded the external tank to try to isolate precisely where the leak originated. We switched out umbilicals; we replaced the seals between the umbilical and the orbiter. We inspected the seals microscopically and found no flaws. We replaced the recirculation pumps, and we found and replaced a damaged teflon seal in a main propulsion system detent cover, which holds the prevalve-the main valve supplying hydrogen to Space Shuttle Main Engine 3 -in the open position. The seal passed leak tests at ambient temperature but leaked when cryogenic temperatures were applied. We added new leak sensors-up to twenty at a time and tried to be methodical in our placements to narrow down the possible sources of the problem. We even switched orbiters, sending Columbia back to the Vehicle Assembly Building and bringing out Atlantis, scheduled to fly as STS-38. Two shuttles on their mobile launchers passing in the night was a majestic sight, but not one you want to see if you're trying to get an orbiter launched. None of this told us where the leak was, or if we were dealing with more than one leak source

Kennedy Space Center: Apollo to Multi-User Spaceport

NASA Kennedy Space Center (KSC) was established as the gateway to exploring beyond earth. Since the establishment of KSC in December 1963, the Center has been critical in the execution of the United States of Americas bold mission to send astronauts beyond the grasp of the terra firma. On May 25, 1961, a few weeks after a Soviet cosmonaut became the first person to fly in space, President John F. Kennedy laid out the ambitious goal of landing a man on the moon and returning him safely to the Earth by the end of the decade. The resultant Apollo program was massive endeavor, driven by the Cold War Space Race, and supported with a robust budget. The Apollo program consisted of 18 launches from newly developed infrastructure, including 12 manned missions and six lunar landings, ending with Apollo 17 that launched on December 7, 1972. Continuing to use this infrastructure, the Skylab program launched four missions. During the Skylab program, KSC infrastructure was redesigned to meet the needs of the Space Shuttle program, which launched its first vehicle (STS-1) on April 12, 1981. The Space Shuttle required significant modifications to the Apollo launch pads and assembly facilities, as well as new infrastructure, such as Orbiter and Payload Processing Facilities, as well as the Shuttle Landing Facility. The Space Shuttle was a workhorse that supported many satellite deployments, but was key for the construction and maintenance of the International Space Station, which required additional facilities at KSC to support processing of the flight hardware. After reaching the new Millennium, United States policymakers searched for new ways to reduce the cost of space exploration. The Constellation Program was initiated in 2005 with a goal of providing a crewed lunar landing with a much smaller budget. The very successful Space Shuttle made its last launch on July 8, 2011, after 135 missions. In the subsequent years, KSC continues to evolve, and this paper will address past and future efforts of the transformation of the KSC Apollo and Space Shuttle heritage infrastructure into a more versatile, multi-user spaceport. The paper will also discuss the US Congressional and NASA initiatives for developing and supporting multiple commercial partners, while simultaneously supporting NASAs human exploration initiative, consisting of Space Launch System (SLS), Orion spacecraft and associated ground launch systems. In addition, the paper explains the approach with examples for NASA KSC to leverage new technologies and innovative capabilities developed to reduce the cost to individual users

Strangeness in Neutron Stars

It is generally agreed on that the tremendous densities reached in the centers of neutron stars provide a high-pressure environment in which several intriguing particles processes may compete with each other. These range from the generation of hyperons to quark deconfinement to the formation of kaon condensates and H-matter. There are theoretical suggestions of even more exotic processes inside neutron stars, such as the formation of absolutely stable strange quark matter. In the latter event, neutron stars would be largely composed of strange quark matter possibly enveloped in a thin nuclear crust. This paper gives a brief overview of these striking physical possibilities with an emphasis on the role played by strangeness in neutron star matter, which constitutes compressed baryonic matter at ultra-high baryon number density but low temperature which is no accessible to relativistic heavy ion collision experiments.Comment: 16 pages, 5 figures, 3 tables; Accepted for publication in the Proceedings of the International Workshop on Astronomy and Relativistic Astrophysics (IWARA) 2005, Int. J. Mod. Phys.

A framework for the analysis and comparison of process mining algorithms

Process mining algorithms use event logs to learn and reason about business processes. Although process mining is essentially a machine learning task, little work has been done on systematically analysing algorithms to understand their fundamental properties, such as how much data is needed for confidence in mining. Nor does any rigorous basis exist on which to choose between algorithms and representations, or compare results. We propose a framework for analysing process mining algorithms. Processes are viewed as distributions over traces of activities and mining algorithms as learning these distributions. We use probabilistic automata as a unifying representation to which other representation languages can be converted. To validate the theory we present analyses of the Alpha and Heuristics Miner algorithms under the framework, and two practical applications. We propose a model of noise in process mining and extend the framework to mining from ‘noisy’ event logs. From the probabilities and sub-structures in a model, bounds can be given for the amount of data needed for mining. We also consider mining in non-stationary environments, and a method for recovery of the sequence of changed models over time. We conclude by critically evaluating this framework and suggesting directions for future research