* Here [1] is a position-paper proposing an HVDC pan-European "supergrid" of up to 4KM distance, including undersea HVDC, overlaying and working with the existi

* Here [1] is a position-paper proposing an HVDC pan-European "supergrid" of up to 4KM distance, including undersea HVDC, overlaying and working with the existing, less capable AC grids. No magic, no HT superconductors, just recent evolution of existing HVDC technology which will enable a "meshed" HVDC grid (not just isolated HVDC point-to-point links). It elementally observes that while high cable capacitance limits undersea cable AC transmission distance, it doesn't for HVDC; DC doesn't get through capacitance once charged, whilst "reactive" (capacitive and inductive) effects limit how much power can be extracted at the other end of a "long" transmission link (sorry, no reference right now on that). Avoiding reactive transmission losses is one of the reasons AC power distribution is optimal for moderate grid and distribution scale at its low frequencies of 60 Hz or 50 Hz. HV avoids ohmic losses, while low frequency reduces reactive losses up to the limits of some estimable built-out scale. Going to DC allows scaling out to longer distances than AC, even as ohmic losses are minimized by using HV (ohmic losses are elementally the same, whether AC or DC). * Here [2] is a quick summary of recent improvements in HVDC transmission and high power "VSC" inverter techniques, citing [1], summarizing: "...there is now no doubt as to the feasibility of HVDC networks ferrying renewable energy resources from wherever they are in surplus to wherever they are needed." [1] http://mainstream-downloads.opendebate.co.uk/downloads/WG2_Roadmap_to_the_Supergrid_Technologies_2013_Final_v2.pdf http://mainstream-downloads.opendebate.co.uk/downloads/WG2_R... [2] http://spectrum.ieee.org/energywise/energy/the-smarter-grid/hvdc-supergrid-technologies-besting-expectations http://spectrum.ieee.org/energywise/energy/the-smarter-grid/...