Hydro, wind and solar power collection units are normally situated far away from consumers. In order to utilize these energy sources in an efficient way, the electricity produced has to be transmitted very long distances at a sufficiently low cost. As electricity production has primarily used fossil fuels, which can be transported by boat, there has not been great demand for better methods of electrical transmission. The hydropower resources in the north of Sweden were developed early on and knowledge in electric transmission was developed alongside.
The easiest way to improve transmission capacity is to increase voltage. This was done in Sweden. It was the first country to use 400 kV alternating voltage on a large scale almost sixty years ago.
To transmit electric power very long distances or in cables it was not enough to increase the voltage. But to convert the alternating current to direct current (HVDC) provides considerable advantages. Development has continued rapidly and today up to seven thousand megawatts can be transmitted more than two thousand kilometers on one power line with HVDC
The picture shows how Europe could be supplied by renewable electric energy by utilising HVDC transmission (Origin: ABB and Gunnar Asplund).