Natural gas has become the UK’s foremost primary energy source, providing some 39% of our energy needs. The National Transmission System (NTS) has developed from its humble beginnings when natural gas was first discovered in the North Sea in the 1960s to become a complex interconnected network delivering up to 550 million cubic meters of gas daily. Gas has also become an increasingly important energy source for power generation, currently generating 35% of our electricity. This presents major challenges for the planning and operation of both the electricity and gas networks as their interdependence grows into the future. With the government’s goal of drastically reducing emissions from power generation by 2020, Combined Cycle Gas Turbine units, and therefore the NTS, will have to offer a new degree of flexibility to quickly respond to the intermittency of the growing penetration of wind generation on the electricity transmission system. Coupling this with the decline in the UK natural gas resources resulting in the NTS becoming reliant on imports to meet demand, it is becoming increasingly difficult to decouple the security of the gas supply from the security of the electricity supply in the UK. This study presents the modelling challenge of assessing this growing interaction and provides a robust methodology for completing a security analysis using detailed network models of the UK gas and electricity transmission systems. A thorough investigation of the intraday operation of the two systems in 2020 is presented given the growth of wind generation in the UK. The results are analysed and the implications for combined modelling and assessment are discussed as we enter a new era for UK energy security.

This master’s thesis deals with the design of a heat recovery steam generator. The introductory part of the thesis is dedicated to waste heat boilers, their division and their utilization in combined cycles gas turbine. In the following chapter, an analysis of the existing combined heat and power plant operation is performed. In the next part of the thesis, the conceptual layout of the new source is designed. Subsequently, the thermal calculation of the boiler is carried out as well as the design of individual heat exchanging surfaces. The sixth chapter deals with the strength calculation of the boiler and the outer piping, chambers and drum are designed here. At the end of the thesis there are described off-design states of the new combined cycle gas turbine.

This thesis deals with the design of a Heat Recovery Steam Generator (HRSG). Theintroductory part is devoted to a brief description of the boiler, the specified parametersand the compilation of the temperature profile. The main computational part of thiswork is divided into 6 parts. The first contains preparatory calculations, including thecalculation of boiler eiciency. In the second part, a flue gas duct is designed. This isfollowed by a thermal calculation of the boiler for all heat exchange surfaces. The last 3parts deal with the design of the drum, piping and the loss of boiler draft calculation.

Combined cycle gas turbine power plants (CCGT), as part of the electricity generation fleet, are required to improve their flexibility to help balance the power system under new scenarios with high shares of variable renewable sources. Among the different possibilities to enhance the power plant performance, an inlet air conditioning unit offers the benefit of power augmentation and “minimum environmental load” reduction by controlling the gas turbine intake temperature using cold thermal energy storage and a heat pump. In this thesis, an evaluation of the conditioning unit impact over a power-oriented CCGT under a day-ahead optimized operation strategy is presented. To establish the hourly dispatch of the power plant and the right operation mode of the inlet condition unit bringing the desired benefits, a mixed-integer linear optimization was formulated aiming to maximize the operational profit of the plant within a 24 hours horizon. To assess the impact of the proposed unit operating under this control strategy, annual simulations of a reference power plant were developed with and without the unit, allowing to a comparison of their performance by means of technical and economic indicators. Furthermore, a case study changing equipment sizes was performed in order to identify trends of the power plant performance related to such parameters; and lastly, a sensitivity analysis on market conditions to test the control strategy response was included. The results indicate that the inlet conditioning unit together with the dispatch optimization increase the power plant operational profit trough the gain of power variation over peak and off-peak periods. For the specific case study in northern Italy, it is shown that a power plant integrated with the conditioning unit is more profitable in terms of net present value based on the undertaken investment figures. Related to the technical performance, it also shows that the unit reduces by 1,34% the minimal environmental load when part-load operations are required and that it can increase the net power output by 0.17% annually. All in all, this study presents the benefits of a dispatch optimization strategy when couple to a novel solution to increase CCGT flexibility. / Elproducerande kombikraftverk (CCGT) förväntas förbättra sin flexibilitet för att kunna bidra till stabilisering av elnätet i framtida scenarier med ökande andel variabla, förnybara energikällor. Av de diverse metoder som finns att tillgå för att förbättra ett kraftverks prestanda, erbjuder en inluftsbehandlingsenhet både fördelar med kraftförbättring samt minskning av “minimun environmental load”; genom att med hjälp av kall termisk energilagring och en värmepump kontrollera gasens inluftstemperatur till gasturbinen. I den här uppsatsen undersöks hur en sådan inluftsbehandlingsenhet påverkar prestandan hos en kraftproduktionsfokuserad CCGT när en optimerad driftsstrategi introduceras. För att bestämma kraftverkets elproduktion vid varje timme och det korrekta driftläget för luftbehandlingsenheten (för att uppnå tidigare nämnda eftersökta fördelar) formulerades ett linjärt optimeringsproblem med syfte att maximera kraftverkets driftsförtjänst under ett 24-timmars tidsspann. För att bedöma den föreslagna inluftsbehandlingsenhetens inverkan under den optimerade driftsstrategin genomfördes simuleringar av ett referenskraftverk med och utan nämnda enhet, varpå en jämförelse med avseende på teknisk prestanda och ekonomi genomfördes. Vidare genomfördes en fallstudie där storlek på diverse utrustning varierades för att kunna identifiera trender i kraftverksprestanda baserat på dessa parametrar; slutligen genomfördes en känslighetsanalys rörande hur luftbehandlingsenheten och kontrollstrategin reagerar vid olika marknader.. Resultaten indikerar att en inluftsbehandlingsenhet tillsammans med en optimerad driftsstrategi ökar kraftverkets driftsvinning genom en ökad variation i kraftuttag över peak och off-peak timmar. För fallstudien i norra Italien fanns att ett kraftverk med integrerad luftbehandlingsenhet är mer lönsamt sett till nuvärdesanalys. Gällande teknisk prestanda visade resultaten att enheten minskar den minsta miljöbelastningen med 1,34 % när delbelastningsdrift fordras, och att det kan öka nettokraftuttag med 0,17% årligen. Sammanfattningsvis presenterar denna studie fördelarna med ett driftsoptimerat kraftverk kopplat till en ny lösning för att öka flexibilitet hos CCGT:er.