Supergrid Terminology

DC grid Terminology

The term “supergrid” is not adequately descriptive. Especially since it has been used to describe several different scales of large grids.  Loosely, supergrids must allow power sharing over a continental size area in order to work.  Supergrids will enable a renewable based energy economy by spreading weather risks between at least three weather systems. The term “continental scale grid” or simply “continental grid” is actually more specific and descriptive. It is easy to imagine a European grid, an Asian grid, an African grid, an Australian grid, a North American grid, and a South American grid. Any such continental grid that is thousands of kilometers across must be a DC grid. This is because with any continental scale AC grid phase instabilities develop especially when an outage occurs in a major generator or a major powerline. There are still technological problems to be solved before such meshed hvdc grids can be built, yet it is well established that continental grids will need to be DC.

If we build such continental scale DC grids, there becomes a large benefit to linking these grids together into a global grid. This will occur one step at a time, for example the European grid will ultimately link up with Asian and African grids to form a meshed hvdc grid that shares generation resources all the way from Japan to India to South Africa to the UK to Northern Europe and on through Siberia and back to Japan, and everything within that loop. One could call this the  Eurasian-African supergrid but I see all such combinations of continental grids as steps that will ultimately be linked Into a global grid. Our great-grandchildren will thank us greatly if we have the foresight to make sure that every continental grid operates at the same voltage so that the ultimate global grid will be much less expensive to form by linking the continental grids.

I propose the term “mesogrid” to describe the scale of DC grids that might link substations around a city. It is less important that such mesogrids operate at a common voltage. Currently substations are linked strictly by AC power lines.I envision the term mesogrid to refer to DC grids operating at voltages around plus minus 100 kilovolts. Mesogrids can greatly stabilize power supply within a city which is fed by multiple long-distance power connections.