Complex sentence: Brown coal has a low energy density due to the high moisture content and would have been uneconomic to transport into Melbourne, but advances in electrical transmission technology meant that electricity could be generated beside the fuel source and transmitted to the consumer.
Split into simpler sentences: Brown coal has a low energy density due to the high moisture content and would have been uneconomic to transport to Melbourne. However, advances in electrical transmission technology allowed electricity to be generated near the fuel source and transmitted to the consumer.