Compressed natural gas (cng) power system with co2 emissions capture and storage

CNG power system (1) comprising a storage tank (6) connected fluidically to a fuel conversion system (2) via an energy transfer system (4), the fuel conversion system (2) comprising a power unit using CNG as fuel and generating gas emissions comprising C02, the fuel conversion system comprising a C02 capture unit (16) configured for separating out C02 from the gas emissions. The energy transfer system comprises a CNG expansion turbine (22) mounted in a fuel circuit (8) between the storage tank and fuel conversion system powered by expansion of the CNG flowing from the storage tank to the fuel conversion system, and a C02 compressor (24) connected between the fuel conversion system and the storage tank along a C02 circuit (10) for compressing the C02, power for driving the C02 compressor (24) being supplied in part by power generated by the CNG expansion turbine (22).