Same as other energy-intensive industries, the Oil & Gas sector is looking at the development of energy-efficiency solutions aimed to reduce the carbon footprint of its business. The conversion of waste heat into useful power represents a viable and profitable solution to hit these targets. In this framework, Organic Rankine Cycle (ORC) technology represents a feasible option to exploit waste heat and boost the overall efficiency of the gas transportation segment with minimum impact on the existing facilities.
In O&G, one of the main applications of ORC is within Gas Compressor Station (GCS). GCS along the pipelines have in place multiple gas turbines used as prime movers of the compressors which waste a significant amount of thermal energy operating in open cycle. The utilization of such waste heat to produce useful power, leveraging the features that the ORC technology offers, represents a clear opportunity to reduce the CO2 emissions of the whole system, either directly or indirectly. Directly, if the electricity produced by the ORC-based heat recovery system is used on site to drive an electric compressor (EMD); indirectly, if the energy produced is dispatched to the grid and supersedes an equal amount of energy produced on fossil fuels. Novel R&D projects foresee the implementation of electrolyser systems (fed by the electric power generated by the ORC) to produce "green" Hydrogen to be injected in the pipeline in order to increase the percentage of green gas that flows in the network. Where no waste heat is present, another potential form of energy is available: this is the case of gas pressure letdown facilities that are in charge to reduce the pressure along the gas distribution network by means of reduction valves that dissipate the energy contained in the pressurized gas. In this scenario, the Gas-expander technology can be a valuable alternative and a more efficient solution. As ORC, it consists in a turbine through which the natural gas at high pressure, rather than being reduced with valve, expands to produce work, thereafter, converted into electricity by a generator. The paper will present the above-mentioned solution, along with related case histories, and will show how the implementation of the ORC systems represents other than a way to meet sustainability targets also a remarkable and profitable business for O&G companies. Furthermore, the Gas Expander technology represents a solution to improve the energy efficiency of NG transmission and distribution networks.
