Variable Transmission Voltage for Loss Minimization in Long Offshore Wind Farm AC Export Cables

Connection of offshore wind farms to shore requires the use of submarine cables. In the case of long HVAC connections, the capacitive charging currents limit the transfer capability and lead to high losses. This paper shows that the losses can be substantially reduced by continuously adjusting the cable operating voltage according to the instantaneous wind farm power production.Calculations for a 320 MW windfarm connected to shore via a 200 km cable at 220 kV nominal voltage shows that an annual loss reduction of 9 percent is achievable by simply using a 15 percent tap changer voltage regulation on the two transformers. Allowing a larger voltage regulation range leads to further loss reduction (13 percent for 0.4-1.0 p.u. voltage range). If the windfarm has a low utilization factor, the loss reduction potential is demonstrated to be as high as 21 percent . The methodology can be applied without introducing new technology that needs to be developed or qualified.Comment: To be submitted to IEEE Transactions on Power Deliver

Assessing the Impact of the Iberian Exception on Day-Ahead Prices in Spain : A Difference in Difference and Quantile Regression Approach

The energy crisis of 2021 and 2022 has had severe consequences for Europe. The skyhigh energy prices have reduced economic growth, created inflation, and increased GHG emissions. In an effort to tackle the record high prices, Spain and Portugal have been granted an exception by the EU to implement a cap on the price of gas used for generating electricity. The price cap, best known as the Iberian exception, has sought to limit the impact of volatile gas prices in the electricity market by decoupling the gas price from the electricity price. Within the context of the crisis, it is vital to assess whether the implemented measures have achieved their objectives. This thesis studies the Iberian exception's impact on day-ahead electricity prices in Spain. By estimating a difference in difference model, we find a causal effect of the Iberian exception on day-ahead prices, confirming that the instrument does reduce electricity prices. Furthermore, the results from our quantile regression models show that the gas cap has reduced electricity prices across the price distribution, and reduced price volatility. The results confirm a partial decoupling of the gas price and the electricity price, and the price reducing effect of the instrument is only evident in conjunction with the gas price. While our thesis provides evidence that the Iberian exception has been efficient in reaching its goal, it also highlights multiple adverse effects. The decoupling of gas and electricity prices has led to increased gas generation, alongside increased exports to France, thereby benefitting French consumers. Our analysis show that the Iberian exception can be considered a success in Spain. However, based on our results we do not recommend similar interventions in other European countries, as the adverse effects would exceed the benefits.nhhma

An open-source tool for reliability analysis in radial distribution grids

We present an open-source software implementation of an approximate contingency enumeration approach for calculating reliability in distribution grids based on RELRAD. The tool is coded using the efficient programming language Julia, to ensure fast and scaleable calculations. The network topology is mapped as a graph. This allows us to efficiently determine load points affected by contingencies by using standard graph algorithms. The tool is demonstrated on a simple synthetic test system and an actual Norway distribution grid.acceptedVersio

Song of Triumph: Brass Choir

Full conductor score for brass choir including parts for individual instruments (1st B flat trumpet, 2nd B flat trumpet, 3rd B flat trumpet, 1st French horn, 2nd French horn, 3rd French horn, 1st trombone, 2nd trombone, 3rd trombone, baritone bass clef, baritone treble clef and tuba); 18 pages

Environmental justice in a very green city: Spatial inequality in exposure to urban nature, air pollution and heat in Oslo, Norway

Poorer citizens are often more exposed to environmental hazards due to spatial inequalities in the distribution of urban blue-green space. Few cities have managed to prevent spatial and social inequality despite sustainable development strategies like compact city planning. We explore whether environmental injustice exists in a city where one would least expect to find it: a city with abundant nature, an affluent population governed by a left leaning social democratic city council, and an aggressive densification strategy; Oslo, Norway. Green space was measured with a satellite-derived vegetation index which captures the combined availability of gardens, street trees, parks and forest. Blue space was defined by the proximity of residential areas to the closest lake, river or fjord. We found that poorer city districts, often with greater immigrant populations, have less available blue-green spaces and are disproportionately exposed to hazardous air pollution levels, but not extreme heat compared to wealthier city districts. Citizens living within 100 m of a water body are likely to earn US$20,000 more per year than citizens living 500 m away from water, and a US$ 3000 increase in annual income corresponds to a 10 % increase in green space availability. Hazardous air pollution concentrations in the poorest city districts were above levels recommended by the WHO and Oslo municipality. Historical trends showed that districts undergoing population densification coincide with the lowest availability of blue-green space, suggesting that environmental justice has been overlooked in compact city planning policy. Despite Oslo's affluence and egalitarian ideals, the patterns of inequality we observed mirror the city's historical east-west class divide and point to spatial concentration of wealth as a core factor to consider in studies of green segregation. Urban greening initiatives in Oslo and other cities should not take spatial equality for granted, and instead consider socio-economic geographies in their planning process. Green space Blue space Densification Urban nature Urban sustainability ExposurepublishedVersio

Erstatning for positiv kontraktsinteresse i anskaffelsesretten

I HR-2019-1801-A «Fosen-Linjen» etablerte Høyesterett et nytt ansvarsgrunnlag for erstatning for positiv kontraktsinteresse for brudd på reglene om offentlige anskaffelser. Avhandlingen analyserer innholdet i dette ansvarsgrunnlaget.MasteroppgaveJUS399MAJUR-2MAJU

Mobilising and nurturing collaboration in research – the value of a focused imagination

"Establishing and nurturing contacts are important and time-consuming elements of interactive research. It is usually the researcher who has to establish and nurture collaboration with practitioners – a task that is not normally part of traditional research. A mutual interest in the subject of the research is a prerequisite for collaboration, but there are quite often other factors that explain why collaboration begins and endures. On the basis of the experience gained in a number of interactive research projects, we address the conditions required for an effective and lasting interplay between collaborating partners. Theoretical inspiration has been provided by studies of so-called imaginary organisations." (author's abstract

Attitudes toward Wind Power in Norway–Solution or Problem in Renewable Energy Development?

Wind power has become an increasingly important source of renewable energy in Norway. Current demand and production capacity have exceeded expectations stipulated in energy policies a few years back. Wind power affects landscape characteristics, and the rapid development has created considerable public conflict. However, knowledge to date about public attitudes toward wind power development in Norway is limited. We surveyed a representative sample of the Norwegian public to examine relationships between wind power development and place attachment, localization, and policies. We also examined if attitudes toward wind power are linked to broader environmental attitudes and meaning of place. Public attitudes range from strong support to strong opposition. We found limited support for NIMBY effects. Support versus opposition correlates with attitudes toward place attachment, localization of wind power plants and energy policies. We found evidence of a dichotomy between the more fundamental world views of eco-modernism versus de-growth influencing the more specific wind power attitudes. We argue that policy institutions have underestimated the power of attitude diversity in the wind power debate, and that social acceptability of future wind power development will depend on improved understanding of how social values of landscapes are impacted. Wind power development, Environmental attitudes, Energy policy, Ecomodernism, Degrowth, Landscape valuespublishedVersio