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The focus of this research is the potential of biomethane in Britain's gas grid. It examines its relative ability to address Britain's sustainability and energy security challenges from an economic perspective. Such research is important because UK is wedded to gas for heat production and power generation and is increasingly dependent on imported gas, in line with shrinking domestic production, and uncertain future trading relationships. Also, dependency on natural gas, threatens Britain achieving its legally-binding carbon budgets. The study included a thorough literature review, primary research to finally uncover the views of key UK market participants plus analytical modelling. The findings reveal that the market is cautiously optimistic, despite reservations regarding feedstock availability and the impending cessation of subsidy approvals. Investors are in greater need of long-term certainty, however, and the challenge of decarbonising heat and heavy-duty transport warrants this. Retail price premiums are polarised but, in line with wholesale costs, relatively high compared to electricity. The key recommendation is for the policymakers to follow precedents in renewable electricity and liquid biofuels, by mandating that energy suppliers, owners of heavy-duty road fleets and occupiers of new buildings purchase biomethane. In tandem, feedstock and grid-entry restrictions must be tackled creatively.

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The concept of combining small micro gas turbines with solar dish concentrator is being developed by the EU funded project OMSoP [1] to benefit from the advantages of higher efficiency, power density and reliability. This paper focuses on small units which are only powered by the solar irradiation and aims to identify suitable means of control that would minimize power output variations and achieve maximum annual generated electricity. Three different strategies have been proposed and studied in this work: power regulation control which is based on variation of the load to achieve maximum permissible power for any particular value of insolation, recuperation control which is a novel idea to partially by-pass the recuperator and use it as an additional degree of freedom in the control scheme and a hybrid control strategy which combines the first two methods. The evaluation criteria of these strategies are based on the annual generated electricity, rated generated power, solar-to-electrical efficiency and practical considerations. The performance of a 5kWe system has been calculated and compared when each of the above control strategies are applied. Quantitative and qualitative comparisons show that the recuperation control and combined methods can provide constant power output for a wide range of solar irradiation, but at the expense of reduced overall performance and additional cost and complexity. The power regulation strategy provides maximum generated electricity, but it is not suitable when the generated power by the system requires to follow the variations of the load from the consumer side.

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The aim of this paper is to present a thermo-economic model of a microturbine for solar dish applications, which demonstrates the applicability and accuracy of the model for off-design performance evaluation and techno-economic optimisation purposes. The model is built using an object-oriented programming approach. Each component is represented using a class made of functions that perform a one-dimensional physical design, off-design performance analysis and the component cost evaluation. Compressor, recuperator, receiver and turbine models are presented and validated against experimental data available in literature, and each demonstrated good accuracy for a wide range of operating conditions. A 7-kWe microturbine and solar irradiation data available for Rome between 2004 and 2005 were considered as a case study, and the thermo-economic analysis of the plant was performed to estimate the levelised cost of electricity based on the annual performance of the plant. The overall energy produced by the plant is 10,682 kWh, the capital cost has been estimated to be EUR 27,051 and, consequently, the specific cost of the plant, defined as the ratio between the cost of components and output power in design condition, has been estimated to be around EUR 3980/kWe. Results from the levelised cost of electricity (LCOE) analysis demonstrate a levelised cost of electricity of EUR 22.81/kWh considering a plant lifetime of 25 years. The results of the present case study have been compared with the results from IPSEpro 7 where the same component characteristic maps and operational strategy were considered. This comparison was aimed to verify the component matching procedure adopted for the present model. A plant sizing optimisation was then performed to determine the plant size which minimises the levelised cost of electricity. The design space of the optimisation variable is limited to the values 0.07–0.16 kg/s. Results of the optimisation demonstrate a minimum LCOE of 21.5 [EUR/kWh] for a design point mass flow rate of about 0.11 kg/s. This corresponds to an overall cost of the plant of around EUR 32,600, with a dish diameter of 9.4 m and an annual electricity production of 13,700 [kWh].

The turbulent combustion flow modeling are performed to study the impacts of CO 2 addition to the fuel and oxidizer streams on the thermochemical characteristics of a swirl stabilized diffusion flame SM1. A flamelet approach along with three well-known turbulence models are utilized to model the turbulent combustion flow field. The k−ω SST shows the best agreement with the experimental fields compared to other methods. Then, the k−ω SST is employed to study the effects of CO 2 dilution on the flame structure and strength, temperature distribution, and CO concentration. To determine the chemical effects of CO 2 dilution, a fictitious species is replaced with the regular CO 2 in both fuel and oxidizer streams.The results indicate that the flame temperature is decreased when CO 2 is added to either fuel or oxidizer streams. The flame length reduction is observed at all levels of CO 2 dilution. The H radical concentration indicating the flame strength decreases following by the thermochemical effects of CO 2 dilution processes. In comparison with fictitious species dilution, chemical effects of CO 2 addition enhance CO mass fraction. The numerical simulations show that by increasing the