Assessment of the impact of widespread integration of compressed natural gas filling stations and biomethane injection on the gas network

Abstract

The research in this thesis has explored, investigated and analysed the integration of biomethane production and injection facilities and compressed natural gas (CNG) filling stations in to gas distribution networks, through technical, economic and environmental modelling. First, a simulation of a gas distribution (Dx) network was built to investigate the impacts of technical limits imposed by gas network operation and safety standards on the quantity of biomethane which can be injected. The Dx network simulation also incorporates annual consumer demand profiles based SCADA data, taking into consideration the seasonal variations in the gas demand. Scenarios of maximum, minimum and no demand at a grid-connected compressed natural gas (CNG) filling station were computed, to determine the impact of the addition a CNG filling station to the gas network. The location of the biomethane production and injection facility is also analysed. The results calculated the grid capacity to accept biomethane on an hourly basis over the course of a year. This data was used to determine a range of possible plant sizes for each potential facility location and CNG demand scenario. Next, a spatially explicit geographical information systems model was created to map the distribution of feedstocks suitable for biomethane production in the surrounding area and determine the transport distances. These two submodels fed into a techno-economic assessment that calculated the levelised cost of energy and net present value for each configuration, and techno-econo environmental models that calculated the total cost of carbon abatement for each configuration. Key parameters for both of these models include the capital and operating cost of the anaerobic digester, upgrader, injection facility and CNG station, the feedstock transportation cost, and the potential incentives for biomethane and bioCNG. The techno-econo-environmental model also incorporates a life cycle assessment for the production and use of biomethane as either a fuel for residential heating or a fuel for CNG heavy goods vehicles, to determine the overall environmental costs and benefits. This work contributes to gas grid, biomethane and bioCNG research, by presenting a novel method of modelling the integration of biomethane injection facilities and CNG filling stations into gas Dx networks, to assess the overall technical, economic and environmental impacts.