This morning I was fortunate to speak about ONR-funded research at the World Green City in Northern Thailand with Captain Paul Marshall, Associate Director for Power and Energy for ONR Global.
World Green City is a prototype of a green city located on the Saluang-Keelek campus of Chiang Mai Rajabhat University. It is comprised of about 20 buildings making use of the latest technology. The DC microgrid funded by the ONR is one of the innovations in place.
Captain Marshall explained that the microgrid can be powered by a number of sources. The power generated is stored in batteries and distributed as needed to the various places requiring power. The grid is self-sustaining and is not intended to connect to a larger power grid as do many solar farms in the US. Instead, this microgrid is designed to be a self-sufficient source of power for remote locations. The area of particular interest with this microgrid technology lies in the fact that it is a source of DC power.
DC – direct current – power is the power that is produced by solar cells, batteries, and fuel cells. AC – alternating current – is the power that is available in our homes in the US and required by our appliances. This AC power has been converted from a DC source. We use AC because it travels well and, because of this, can be generated at a significant distance from the place it will be used. (You can read a simple explanation of DC to AC conversion on How Stuff Works.)
Since travel over long distances is not an issue in a microgrid, the DC current can be used just as it is. This saves a step. It also makes conversion equipment unnecessary – then again, whatever is being powered must be able to use DC current.
It’s my view that the microgrid has exciting potential. For a small island such as Nauru, located in the South Pacific Ocean, a microgrid could replace the current use of fossil fuels with a dependable, clean source of energy. Nauru has other, more pressing issues – such as a lack of arable land – but perhaps solutions to some of the other issues will be found if microgrid technology is deemed appropriate as a first step.