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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.

This paper presents an experimentally validated computational study of heat transfer within a compact recuperated Brayton cycle microturbine. Compact microturbine designs are necessary for certain applications, such as solar dish concentrated power systems, to ensure a robust rotodynamic behaviour over the wide operating envelope. This study aims at studying the heat transfer within a 6 kWe micro gas turbine to provide a better understanding of the effect of heat transfer on its components’ performance. This paper also investigates the effect of thermal losses on the gas turbine performance as a part of a solar dish micro gas turbine system and its implications on increasing the size and the cost of such system. Steady-state conjugate heat transfer analyses were performed at different speeds and expansion ratios to include a wide range of operating conditions. The analyses were extended to examine the effects of insulating the microturbine on its thermodynamic cycle efficiency and rated power output. The results show that insulating the microturbine reduces the thermal losses from the turbine side by approximately 11% without affecting the compressor’s performance. Nonetheless, the heat losses still impose a significant impact on the microturbine performance, where these losses lead to an efficiency drop of 7.1% and a net output power drop of 6.6% at the design point conditions.