There is a growing demand for increased electricity transfer capacities between the countries surrounding the North Sea. The increased capacities will enable easier integration of intermittent renewable energy sources, decrease the need for balancing power, increase power trade and competition, and increase security of supply across the region. Interregional offshore grid connections are required if large scale deployment of deep sea, far from shore offshore wind energy in the North Sea is to take place. The WINDSPEED research project has resulted in proposals of realistic scenarios for large scale deployment of offshore grid and wind energy in the North Sea. In this study the environmental impacts of an interregional meshed offshore grid as proposed by WINDSPEED have been assessed. Environmental impacts of the offshore wind farms, which may be connected to the grid, have been included in the assessment as well, completing the system boundaries.The methods used to quantify the environmental impacts are process-based life cycle assessment (LCA), input-output assessment (IOA) and tiered hybrid LCA, with main focus on the results of the latter. Four offshore grid scenarios have been assessed, with and without offshore wind farms connected. The offshore grid is primarily composed of 450 kV HVDC technology for long distance transmission, based on the HVDC cables used in the NorNed connection. Wind farms are deployed far from shore (requiring much sea transport and long distance grid connections) and at an average of 43.9 meters depth (requiring large bottom-mounted foundations for the wind turbines). These requirements make the environmental impacts of deep sea, far from shore offshore wind energy substantially higher than for both close to shore offshore wind energy and onshore wind energy.The environmental assessment of the interregional meshed offshore grid found that the largest contribution to environmental impacts is from manufacturing and installation of HVDC cables. Sea transport required for installation of components and operation and maintenance contributes between 5 and 25 percent to most impact categories. The electrical equipment (converters, breakers and switchgear) required by the grid has a quite varying contribution, from almost none to some impact categories to about 35 percent to climate change impact. The environmental assessment of the deep sea, far from shore offshore wind energy, finds that the largest contributors to environmental impacts are the wind turbines. But the other components required – deep sea foundations, offshore grid and sea transport for installation, operation and maintenance – makes the environmental impacts caused by it around twice as high as for onshore wind energy installations. Total climate change impacts were found to be 42.9 g CO2-Eq/kWh; the grid is responsible for 11, foundations 31 and sea transport 9 percent of that. The largest impacts of deep sea, far from shore offshore wind energy as compared to other relevant energy sources are to the impact categories freshwater ecotoxicity, human toxicity and metal depletion. The impacts to these categories are many times larger, up to almost 20 times, compared to other relevant fossil fueled energy sources. The impacts to the other impact categories are substantially lower.The results indicate that the environmental impacts caused by an interregional meshed offshore grid in the North Sea are substantial; it needs to be considered an important part of an environmental assessment of deep sea, far from shore offshore wind energy. On the other hand, the environmental costs are probably not so high that they outweigh the potential benefits of such offshore grid connections. It may in fact lead to net environmental gains because of a decreased demand for fossil balance power. As for large scale deployment of deep sea, far from shore offshore wind energy the environmental benefits as opposed to relevant fossil alternatives are obvious, but, including the significant disadvantages of intermittent energy supply and high monetary costs, overall gain to society is harder to predict.

This work involves the study of heating systems that combine solar collectors, geothermal heat pumps and thermal energy storage in the ground. Solar collectors can reduce the electricity use in these systems by reducing the operation time of the geothermal heat pump and by increasing the ground source temperature. These systems can be designed in many ways, consequently the complexity is high. The purpose of this study has been to develop simulation models to study the behavior of these systems, with emphasis on the thermal energy storage in the ground. A simulation tool with several models has been developed in the simulation software TRNSYS based on the proposed heating system at the GEL under the metrological conditions of Shanghai. The program was used for an intensive simulation study, in which the interaction with the borehole heat exchanger, the geothermal heat pump, the evacuated tube collector and the load requirements could be analyzed. A base case was developed to make it possible to vary and compare the design parameters of interest, such as the ground storage volume, the flow rate of the solar collector and the solar collector area. The base case was based on the design parameters of the GEL. The GEL was used as reference building and was simulated in TRNBuild with the thermal characteristics of the building material. From the simulations the heating demand of the building could be obtained and the building model could later on be used as a heat load for the other simulation models. The results showed that the there were heating demand from November to March. The four operation modes of the proposed heating system at the GEL were presented. All of the operation modes were simulated in TRNSYS. The four operation modes were solar thermal ground storage, solar direct heating, direct heat exchange with the ground storage and geothermal heat pump. The operation modes worked in two different seasons, storage season and heating season. The ground storage mode was studied thoroughly by varying the parameters of interest. To test the significance of the borehole configuration, the storage volume was kept constant and the number of boreholes and the borehole spacing were varied. It was found that a compact pattern with a high number of boreholes and small borehole spacing is favorable for borehole thermal energy storages. The performance of a ground storage is directly linked to the storage size. The solar collector efficiency is highly dependent on the return temperature of the storage. It was decided to continue to work with a compact pattern of the storage, rather than the base case of the GEL. This is because this kind of storage showed the most promising storage efficiency and also reached a high ground temperature during storage season.Simulations of the heating modes showed that the solar direct heating mode, the direct heat exchange with ground storage mode and the geothermal heat pump mode can each cover 37%, 25% and 38% of the heating demand respectively. For the simulations of the geothermal heat pump it was shown that the borehole depth is a very important factor for the system performance. Too short borehole depth will cause unstable and too low temperatures at the inlet of the evaporator. To compare the electricity use of a geothermal heat pump system with and without solar collectors there were also performed simulations for a traditional geothermal heat pump system. Results showed that 26.1% of the electricity consumption could be saved. The savings was mostly due to the reduced operation time of the heat pump, since other heating modes could be used. The studies showed that due to the complexity of such systems it is very important to perform simulations to optimize the performance. There are many factors that play an important role since there are so many components involved. The simulations showed that sizing of the system is critical for the system performance.

In this thesis, a novel open cycle desiccant dehumidification system is experimentally studied. The system is installed and operated at Shanghai Jiao Tong University (SJTU) as part of the Green Energy Laboratory (GEL) initiative. The system uses two-stage desiccant dehumidification as well as regenerative evaporative cooling for chilled water production. The purpose of the thesis is to evaluate the system performance during different ambient and operational conditions. The investigated system has great potential regarding the environmental aspect of HVAC system solutions. The system is more energy efficient compared to conventional air conditioning systems and uses solar thermal power provided by evacuated tube solar air collectors as the main source of energy. Therefore, this type of system can contribute in reducing the use of non-renewable energy sources.A lot of experiments have been performed from June to July 2012 during varying ambient conditions. As a first step, the necessary regeneration temperature level is established. The results show that this temperature should be in the range of 70-75˚C or higher to be able to achieve desired dehumidification effect. Then, experiments regarding the overall system performance during different ambient temperature and humidity conditions are performed and analyzed. The results show that the system excels good performance during periods of high ambient humidity and is capable of achieving average COPth and COPel around 0.8 and 5.7 respectively. The total dehumidification efficiency is approximately 58% and is proven to vary with respect to the regeneration temperature, where increasing regeneration temperature results in higher amount of moisture removed from the processed air. The solar collectors providing heat to the regeneration air has an efficiency of 47-60% depending on the available level of solar radiation intensity. During periods of low intensity it is proven that the heating system needs assistance from an auxiliary device to be able to generate a sufficient temperature level. The evaporative cooler producing chilled water is capable of providing water at a temperature below 21˚C during periods of high ambient temperature, and temperatures below 16˚C if the ambient temperature decreases. The achieved dehumidification and cooling capacity of the desiccant system makes it possible to provide qualified supply air with temperature in the range of 20-26˚C and absolute humidity below 12 g/kg. Also, an experiment with the purpose of investigating the newly installed second desiccant wheel is carried out. The system is operated with only the second wheel running and the results show that the dehumidification performance is very good when the second wheel provides the first stage dehumidification. Lastly, experiments investigating the impact of the pre-cooling heat exchanger is performed and analyzed.

Nitrogen oxides (NOx) are formed by oxidation of nitrogen during the combustion process, and production rate is highly affected by flame temperature. NOx is regarded as a local pollutant causing smog, acid rain and health complaints, and strictest emission regulations are found in urban areas. Reduction of NOx emissions from gas turbines can be achieved by modifying the combustion process or by exhaust gas clean up. Several technologies are already commercial available, but there are still a great many being developed. Increased focus on the environment also forces manufacturers to improve existing technology. In this report, different NOx abatement technologies are looked into, and an optimal solution for the coming gas turbines on Skarv Idun is presented. Different techniques are compared in terms of thermal efficiency, emissions, maintenance requirements, load acceptance and rejection, engine stability and reliability and availability. Application and suitability of available technologies for reducing NOx from the selected gas turbines is discussed, and user experience for these is collected. It is showed that all technologies influence operation of the gas turbines to some extent, either by increasing/decreasing efficiency or by affecting engine stability. They also differ in their ability to reduce NOx emissions over the entire load range. Due to weight and space restrictions on offshore installations, limited technologies are suitable for platforms and boats. Gas turbines installed offshore are usually aero-derivative engines with high efficiency and relative low emissions of CO2. This year, Norwegian government introduced a NOx tax in order to reduce NOx emissions from the petroleum industry. Operators are forced to use best available technology, and dry low emission control (DLE) is the only one considered qualified as far as NOx is concerned. DLE is also chosen as the optimal solution for the planned gas turbines on Skarv Idun, due to small operational impacts and positive experience from existing fields. It is however recommended to allocate space in case a new and better combustor with lower emission levels is developed. Looking at a longer perspective, Cheng technology including steam injection into the gas turbine combustor seems very promising for NOx abatement.

High concentrations of sediments is a serious problem for hydropower stations in the Himalayas and the Andes Mountains. For run-of-river power plants sediment causes heavy erosion even with settling basins. This leads to reduced operating hours and high maintenance cost. In addition, the original design experienced problem with heavy cavitation.The objective of this master thesis is to carry out new hydraulic design of the runner and guide vanes of the existing Francis turbines in La Higuera Power Plant with reduced velocity components. To achieve this the cause of the heavy cavitation, which made the turbine fail, has to be established.Results from numerical simulations indicates a low pressure zone causing heavy leading edge cavitation is the reason for the turbine failure. The off-design operation has made the cavitation even worse.To carry out a new design, the in-house design software Khoj was used. Some new parameters, like blade leaning, were included in the program. Blade leaning is an important tool for pressure balancing the runner blade. Further, a parameter study was carried out to investigate the effect of blade leaning, blade angle distribution and blade length. The numerical simulation indicates proper pressure balancing could have avoided the cavitation problems and a new design should have an X-blade shape. Because the power plant is already built, the number of variables is limited. The rotational speed, inlet and outlet diameter remained constant. This made it impossible to significantly reduce the relative velocities. Therefore, coating of all wet surfaces is proposed to reduce the effect of erosion.The main objective for this thesis has been to identify the cause of the turbine failure and develop a new design to fit in the existing power plant. Complete 3D-drawings of the design, including runner and guide vanes, has not been made due to lack of time.

Det har i denne oppgaven blitt vist at inntektsgrunnlaget for plusskunder iNorge er forholdsvis lavt. Dette til tross for at Norges Vassdrags- og Energidirektorat(NVE) har foretatt flere dispensasjoner, samt kommet med forslag tiltariffering for å gjøre plusskundeordningen mer lønnsom og attraktiv. Blantbarrierene for plusskunder kan det nevnes; få leverandører av aktuell produksjonsteknologi,forholdsvis liten erfaring om plusshus blant norske byggefirmaog den mest dominerende barrieren, den økonomiske. Produksjonsteknologienesom er mest aktuelle for plusskunder, vind- og solkraft, har foreløpig forhøy kostnad per kWh til at ordningen er lønnsom.Det har i oppgaven blitt vist til studier utført av SINTEF og NVE somkonkluderer med en kostnad per kWh for kraftproduksjon fra solceller påmellom 3,33 NOK og 5 NOK. To småskala vindturbiner, i utgangspunktetgodt egnet til bygningsmontering grunnet rotordiameter under 2 meter,viste seg i et pilotprosjekt i Nederland å ha en produksjonskostnad på 22,91NOK/kWh og 14,48 NOK/kWh. Den største turbinen, med en rotordiameterpå 5 meter, kom best ut i testen med en produksjonskostnad på 2,03NOK/kWh. Et liknende prosjekt i Storbritannia konkluderte med at i 16av 26 testtilfeller var den målte ytelsen på bygningsmonterte vindturbiner40% lavere enn det som var oppgitt fra produsent. Dette avviket skyldes ihovedsak at virkningsgraden synker drastisk i urbane områder som følge avustabile vindforhold forårsaket av bygninger.NVEs forelåtte tariffering av plusskunder medfører at inntekter og besparelsertil en plusskunde i BKKs nett er estimert til å utgjøre 3352 NOKårlig. Med en oppgitt investeringskostnad på 200 000 NOK er det blitt vistat innvesteringen, gitt en forventet levetid på anlegget på 25 år, ikke vil blilønnsom med dagens kraftpriser og tariffsystem.I oppgaven har det blitt vist til tariffsystemene ”Erneuerbare-Energien Gesetz”(EEG) og ”Feed in Tariff Scheme” (FITs), henholdsvis i Tyskland ogStorbritannia. Det tyske tariffsystemet har bidratt sterkt til at Tyskland vedslutten av 2011 hadde 25 GW installert effekt fra solceller. I Storbritanniakan en plusskunde med et solcelleanlegg på 2,9 kWp forvente inntekter ogbesparelser opp mot 11 000 NOK årlig. I løpet av anleggets levetid kan detteutgjøre opp mot 280 000 NOK. Denne summen står i sterk kontrast til hva en norsk plusskunde per i dag kan forvente, som i løpet av levetiden til anleggeter estimert til å utgjøre om lag 87 000 NOK.Det har også i oppgaven blitt trukket frem at distribuert fornybar kraftproduksjonkan gi utfordringer knyttet til leveringskvalitet, spenningsstabilitetog personsikkerhet. Blant annet er vekselrettere, som er nødvendig for å omformelikespenning til vekselspenning, en kilde til harmoniske i kraftnettet.Et høyt innslag av vekselrettere i kraftnettet innebærer at anleggene for eksempelmå installerer filtre for å unngå at harmoniske sprer seg ut i nettet.Uønsket øydrift av distribuert kraftproduksjon kan i tillegg være en fare fornettselskapets ansatte ved vedlikehold i kraftnettet. Dette stiller også kravtil anleggets evne til å detektere øydrift og koble ut plusskunden. Det internasjonaleenergibyrået (IEA) har i en rapport konkludert med at risiko forpersonskade som følge av øydrift av solcelleanlegg hos plusskunde er 10^-9 årlig.Det har blitt diskutert at varierende innstråling på solcelleanlegg og ustabilevindforhold byr på utfordringer med spenningsregulering. Det har blitt trukketfrem at transient skydekke kan gi ramper i kraftproduksjonen opp mot15% i sekundet. Grunnet det høye innslaget av kraftproduksjon fra solcellerhar tyske myndigheter innført et nytt regulativ for vekselrettere. Regulativetsetter blant annet krav til en vekselretters effektfaktor, samt at en vekselretterskal ha støtte for frekvensbasert effektreduksjon ved frekvenser over 50,2 Hz.Det har blitt vist at et kundedisplay i kombinasjon med avanserte måle- ogstyringssystem (AMS) kan være en sentral kilde til informasjon for plusskunden.Displayet kan presentere forbruk og produksjonsdata i tillegg tilinformasjon om feilsituasjoner i kraftnettet eller plusskundens produksjonsanlegg.Det har i oppgaven blitt presentert et system for hjemmeautomasjon ikombinasjon med et kundedisplay levert av selskapet Control41. Dette systemetstøtter individuell laststyring i husholdningen og innebærer at plusskundensenergiforbruk i større grad kan tilpasses tidspunkt for kraftproduksjon.Eksempelvis kan en vaskemaskin settes til å starte på tidspunkter der plusskundenproduserer egen kraft. Dette innebærer at det aktuelle apparatetdrives med særdeles kortreist og klimavennlig kraft.

A steady growing global demand for energy and rising greenhouse gas emissions has resulted in several initiatives from the European Union with the purpose of increasing energy efficiency. A part of this strategy is the introduction of energy performance certificates for buildings, containing a numerical primary energy indicator. Another instrument is to encourage an increased use of cogeneration. As a member of the European Economic Area agreement, these events also affect Norway. The main aim of the project was to investigate how various relevant parameters influence the primary energy factor of district heating when a combined heat and power (CHP) plant is the heat producing unit. The study was to be based on Norwegian conditions. To select relevant technologies, a mapping of existing and planned CHP facilities connected to district heating (DH) networks in Norway was carried out. The findings were that at present, there are nine steam cycle CHP plants connected to DH networks that are based on waste incineration, one steam cycle that is based on demolition wood and one reciprocating engine that is running on biogas. The installed electric capacity ranged from 0,3 MW to 22,8 MW and the annual district heating production from 1,5 GWh to 196 GWh. Based on this, it was decided to study steam cycle CHP plants further. Three different sizes were chosen: 2 MWel, 10 MWel and 25 MWel.In addition, the situation in Europe was looked into. Here, steam cycle and combined cycle were found to be the two most dominant CHP technologies. To have a different technology to compare with, a combined cycle with 22,7MWel capacity was also included in the study.By running plant simulations, the effects of part load operation, various district heating supply and return temperatures and different fuel types were quantified. STEAM Pro was utilised to design the steam cycle models, while GT Pro was used to design the combined cycle models. STEAM Pro was also used to perform design simulations for different temperature levels in the DH network and to study the effect of different types of fuels. To be able to investigate the part load performance of the plants based on a given district heating demand, the models from STEAM Pro and GT Pro was imported into Thermoflex and modified.Reducing the DH supply temperature from 120 to 80 °C and the return temperature from 80 to 35 °C in the 10 MW steam cycle plant increased the power efficiency by 25% and the power to heat ratio by 33%, but the total efficiency was only slightly increased. Variation of fuel, on the other hand, influenced the power efficiency and the total efficiency almost equally, and the power to heat ratio was hence left relatively unaltered. The results from the simulations at the defined full load conditions showed that power efficiency was more than twice as high for the combined cycle than for the steam cycle plants, and the power to heat ratio was almost four times higher for the CC plant. The total efficiency was approximately 10 % lower for the combined cycle than for the steam cycles.Performance also varied between the different sizes of steam cycles, and both boiler type and turbine size influenced power efficiencies and power to heat ratios. In contrast, the total efficiencies were close to equal. Part load had a great influence on power efficiency and power to heat ratio for all technology types. Especially at very low load levels, the power efficiency was considerably reduced. The combined cycle experienced a total fall in power efficiency of 40%, while the reduction varied from 60% to only 29% for the steam cycle plants. The part load total efficiency was only slightly reduced for all plants. Based on the part load simulations, annual efficiencies and power to heat ratios were calculated for different annual load distributions. The annual power to heat ratio and power efficiency was clearly influenced by changes in the annual load distribution pattern, while the effect was less notable for the annual total efficiencies. To calculate the primary energy factors, the total efficiency and power to heat ratio results from the CHP plant simulations were implemented in an excel tool developed by [16]. Some other modifications were also performed.The district heating primary energy factors (PEFDH) for the defined base case varied from 0,85 for the Combined Cycle* alternative to 1,4 for the 2 MW steam cycle plant. The base case was defined to have medium energy density(8 MWh/m). This was later found to not represent the actual Norwegian conditions, where the average energy density is closer to 4 MWh/m. When this energy density was used, the PEFDH for the 10 MW steam cycle plant increased 9,4%, from 1,38 to 1,51. This value is still considerably lower than the primary energy factor for the average electricity production in the Nordic countries, which is 2,16.It was found that the combined heat and power plant parameters had a significant influence on the primary energy factors. The power to heat ratio was particularly important when the power bonus method was utilised. One main conclusion is therefore that it is important that the performance indicators that are used for the CHP plant are realistic, and takes into account technology type, part load performance and what load duration curve the plant is subject to. In most of the cases studied, the fuel handling process and the use of additives contributed most to the primary energy losses related to the PEFDH, while the sum of primary energy losses was dominated by the losses occurring in the CHP plant and the fuel handling. Nevertheless, what process and parameters that could potentially improve the PEFDH most depended on technology and choice of allocation method. In all cases studied, pump work related to circulating the DH water and energy consumption related to ash transport, construction and dismantling of the CHP plant and DH pipes were negligible or close to negligible. Heat loss became a considerably more dominant primary energy loss contributor when a low energy density was assumed. In the end, the calculation of primary energy factors involves many choices that influence the results. It is therefore important that the calculation method becomes more standardised. As it is today, some processes are optional, for instance the use of additives. In this study, the use of additives had a non-negligible influence on the results. Furthermore, the CHP simulation results underlined the importance of taking type of CHP technology and operational conditions into account when calculating primary energy factors for this kind of systems.According to NS-EN 15316-4-5, the power bonus method is the allocation method that should be utilised when calculating primary energy factors for district heating. This makes the district heating primary energy factors extremely dependent on power to heat ratio and the choice of PEF for avoided electricity. If the amount of avoided electricity production in fact is smaller than the full amount of CHP production or if the PEF of the avoided electricity is lower than what is assumed, this might lead to a severe underestimation of the PEFDH. The ultimate goal with the use of primary energy is to encourage more efficient energy use. It is therefore important that the issues mentioned in the two paragraphs above are further studied and discussed as a part of exploring how a standard method should be designed to face this challenge.

In this thesis a method was developed to evaluate and compare various offshore grid topology and capacity choices. A small power system was created for the purpose of the study, including prototypes of offshore grids. To perform the offshore grid study, preliminary steps had to be taken and four subtasks were thus defined:1. Develop a scenario of wind park sizes and locations.2. Obtain representative wind speed data for each of the locations defined.3. Calculate resulting wind power production, given the scenario and the wind speed data.4. Study wind power integration and effects of grid topologies.The North Sea was chosen as a starting point and offshore wind power scenarios for the North Sea in 2025 and 2030 were first developed. Choices regarding which wind data to base the study on, i.e. re-analysis data, numerical weather prediction data or synthetic wind speed data, were evaluated. It was chosen for the final analysis to use a relatively high resolution wind speed data set, resulting from metrological data modelling. This wind speed data was then matched with the wind park locations and the wind power production for the North Sea scenario calculated. A multiturbine approach was applied for this conversion from wind speed to wind power. Finally, the resulting wind power could be included in an offshore grid structure and integrated into a power system.A small power system was created including three main generation/ load areas based on the characteristics of the Norwegian, Dutch and the British generation portfolios. These areas where connected with link capacities according to the existing and planned HVDC links between the real countries. Three offshore wind areas where then added, interconnected and connected to their respective countries, creating an offshore grid structure. The benefits of different topologies were then investigated by varying the link capacities off the offshore grid structure. Simulations were performed using a unit commitment and economical dispatch simulation tool. The benefits were mainly evaluated in terms of wind integration, emission reductions and reductions in operational cost.All cases are compared with a base case having only radial connection of the offshore wind clusters. The meshed grid structure results in increased wind integration reduced emission and reduced operational cost for all of the cases. The offshore grid was further found to facilitate both wind integration and trade. Though increasing the rating of the interconnections to shore above the capacity of the connected wind park cluster, as to accommodate for additional trade, was not found to give additional benefits. Regarding the capacities of the interconnections between the wind park clusters, the benefits were seen to saturate at a rating equal to the capacity of the smaller of the two connected wind park clusters. As investment cost was not considered in this thesis, further decisions regarding the optimal rating of the cables were based on the assumption that a high link utilisation is desirable. It is however recommended to apply a cost-benefit analysis for more accurate evaluations. As could be expected the effects on the onshore generation were unevenly distributed among the created areas depending on the generation mix. Finally, it should however be noted that since the case study only included three areas and an un-optimised hydro-scheduling method, results should be treated with caution.

The addressed issue for this report is the making of a model, which represents the power system in Great Britain. This model is connected to an already existing model of Northern Europe in order to study how the present power systems are affected by eventual connections between Great Britain and Norway and the profitability of these. A model for 2020 is also created in order to study how increased wind generation are affecting such cables. Electricity trading in Norway is normally done through the Nord Pool exchange which also covers the other Nordic countries. Most of the electricity is traded in the Elspot market where hourly contracts are traded daily for physical delivery in the next day’s 24–hour period. The price for the volumes traded is based on the intersection between the supply and demand curves. Participants in Norway are normally trading their entire volumes at the exchange. This is distinct from trading in Great Britain where the base load and the ‘shape’ normally are traded separately. Electricity trading in Great Britain is based on bilateral agreements which allow direct contracting between counterparts. Each transaction is made independently between the parties involved, giving the customers an opportunity to negotiate the best price from suppliers and generators without being constrained by any official price. Models for both a 2010 and a 2020 scenario of the Great Britain power system are created in the EMPS-model. The EMPS model is a market simulator which optimizes the utilization of a hydro-thermal power system based on stochastic supply and demand. Great Britain is divided into four areas in both scenarios. Each area has defined transfer capacities to other connected areas while the transfer capacity within each area is unlimited. These areas are therefore defined in such a way that boundaries with insufficient transfer capabilities in the real system are located at the boundary between two areas in the model. Coal, gas, bio and oil fired plants are represented individually in the model while nuclear, wind, small scale CHP, hydro and pumped storage capacities are aggregated for each area. Meaning that there is only one aggregated nuclear plant, one aggregated wind farm etc. in each area. An area also has a given demand which varies throughout the week and year. Price calculations in the model are based on the intersection between the supply curve and the demand curve. Pricing in the model is therefore more representative for the way of pricing in Norway than in Great Britain.For the 2010 scenario, three different cable alternatives are simulated. Two of these cases are equal except for the landing area of the cables in Great Britain. One cable is connected to Southern England while the other is connected to Northern Scotland. For the third case, the assumptions are similar to the other cases except for an equalization of the gas price in Europe. The landing area for the cable in this case is Southern England. All three cable alternatives returns a fair-sized congestion rent, but the congestion rent is not sufficient to cover the investment cost for any of the discussed cables based on the defined assumptions. Additionally, the cables result in large grid constraints across the boundary between the landing area in Norway and the other Norwegian areas connected to this area. Increased constraints are also an issue for the cable connected to Northern Scotland.Towards 2020, installed wind capacity is expected to rise considerably. This also includes offshore wind farms such as Dogger Bank. A cable from Norway could therefore be connected to Dogger Bank and utilize spare capacity on the cable from Dogger Bank to Great Britain. Three different cables are discussed for the 2020 scenario. The first case is a cable from Norway to Southern England and the second and third case are cables from Norway to Dogger Bank. All three cables have the same transfer capacity. The difference between the two cables connected to Dogger Bank is the transfer capacity from Dogger Bank to Great Britain. The second case has a transfer capacity towards Britain which equalizes the installed wind capacity at Dogger Bank. For the third case, the sum of both the cable towards Norway and the one towards Britain equalizes the installed capacity at Dogger Bank. As for the cases in the 2010 scenario, none of these cable alternatives generate a congestion rent which is sufficient to make the cable profitable based on the defined assumptions.

En ny generasjon vedovner tilpasset dagens nye boliger er under utvikling, og i den sammenheng skal vedovner med varmelagring vurderes. Varmelagring bidrar blant annet til en mer stabil varmeavgivelse fra vedovnen ved at varmelageret absorberer effekttoppene. Hensikten med denne oppgaven er å beskrive en første gjennomgang av et konsept for et latent varmelager for vedovner. Latent varmelagring vil si at varmen lagres i et materiale som gjennomgår faseovergang. Fordelen med latent varmelagring, i forhold til tradisjonelle lagringsmetoder med kleberstein og keramikk som lagringsmedium, er at vekt og volum reduseres for samme mengde lagret varme, og at varmen tas opp og avgis ved tilnærmet konstant temperatur. Latent varmelagring for vedovner, er så vidt forfatteren kjenner til, ikke tidligere rapportert om i litteraturen. I dette studiet er ulike faseovergangsmaterialer (Phase Change Material, PCM) for varmelagring undersøkt, og blant dem har salthydratet natriumacetat trihydrat og sukkeralkoholet erythritol vist seg å ha egenskaper som gjør dem egnet for formålet. To utfordringer knyttet til bruk av PCM for vedovner er lav termisk konduktivitet og risiko for overoppheting med påfølgende degradering av materialegenskaper. Metoder for å unngå overoppheting av faseovergangsmaterialene er vurdert i rapporten, og et konsept for et varmelager foreslått. Lageret har konsentrisk geometri med innvendige metallfinner og oppvarmingen skjer hovedsakelig ved stråling. Et luftsjikt mellom lageret og ovnsoverflater gir mulighet for konveksjonskjøling, og luftstrømmen kan stenges og åpnes med spjeld. Det er gjennomført numeriske beregninger av modellen med tre ulike finneløsninger, ved bruk av simuleringsprogrammet COMSOL Multiphysics®, for henholdsvis oppvarmings- og nedkjølingssykluser. Sukkeralkoholet erythitol ble brukt som PCM i simuleringene, og faseovergangen er beregnet ved bruk av ekvivalent varmekapasitetsmetode. Resultatet viser at løsningen med fri luftgjennomstrømning og seks sirkulære finner kan unngå overoppheting i to timer og førtito minutter ved konstant fyring. De numeriske resultatene må imidlertid benyttes med forbehold, på grunn av forenklingene som er forklart i rapporten. Når mer informasjon om samspillet mellom ovnstemperaturer og varmelager etterhvert blir kjent, kan modellen videreutvikles og optimaliseres, og konseptet kan testes eksperimentelt i laboratorium.