In the long debate between industrial, grid-based electricity and distributed, home-grown electricity…wait, you didn’t know there was a debate? Not surprising, since one side has all the TV commercials, all the cash-and-carry political power, all the hyper-funded “think tanks” and the endowed university departments. The other side has engaging stories to tell around campfires. Nevertheless, there are two sides to the debate, and the turtle in this race is showing some life recently.
The debate has deep roots in our history. (Are we still teaching history in schools? Or are teachers required to spend equal time on fairy tales? Like in science class in Texas.) The men who harnessed electricity, Thomas Edison and Nikola Tesla, fought long and hard over the merits of direct current (which is what generators generate, and is perfect for local, i.e. distributed, use) and alternating current, which is what alternators, um, alternate, and which travels well, making it ideal for the industrial model of everything. AC won the battle, even though Edison went negative with a film depicting the electrocution of an elephant, which he said demonstrated the dangers of AC. (Actual history is often more entertaining than any fairy tale.)
As long as one assumes that electricity has to come from far away, which is the case for most of the world now because that is the way the world has been built out by the heirs of Tesla and his eventual employer George Westinghouse, then it has to be in the form of AC. DC doesn’t travel well unless it is created at extremely high voltages. Look at the thick cables on your (normal, 12 volt, not hybrid) car battery; that’s the size of cable required to get a significant shot of electricity to go three feet or so, to your starter.
The advantage of AC to the industrial model is that it can be easily stepped up in voltage, shot several hundred miles through wires on sticks, then stepped down again (in a transformer) to a relatively safe and usable voltage for home use. Are there line losses? Do the transformers waste electricity by heating up? Sure, but who cares? It’s cheap and plentiful.
Yes, but. The strings-on-sticks grid is rotting down, its reliability cannot be expected in the near future. The industrial alternative — huge solar and wind “farms” (why on earth are they allowed to call them “farms”?) feeding the aforementioned grid — raises at least as many problems as it solves. Those facts, along with our old friend and genie “technological advances” are conspiring to make distributed DC energy look better and better.
Transistors, which run our cell phones, tablets, computers, all our Pods and Pads, require DC current, hence DC batteries, therefore DC battery chargers. So every device we charge has an inverter that converts AC from the wall socket to DC for the device. Every inverter loses energy as heat, and is typically left plugged in 24/7, not just for the hour it takes to do its work. My house is littered with them, and so, probably, is yours.
Now for the technological advance. You may have noticed that over the last few years the connection of devices to chargers has been standardized, from scores of differently shaped plugs to one — the USB cable. Here’s the thing about the USB cable — it can carry both direct current and data, which can go both ways. The data can be used to control what the power is doing and when. This was all laid out in detail in a recent report in the Economist.
At the moment the USB cables carry only 10 watts. Not for nothing is it called a trickle charger. But next year a new USB cable will be available that carries 100 watts, and can run whole networks of electronic devices and LED lighting, and can charge full size laptops. Moreover, they can run directly off of solar panels, small wind turbines and micro-hydro generators that are typically DC.
This advance is not likely to save the world but it can sure save those of us who use it to craft a safe and resilient 12 volt power system for our home, thus becoming better able to brace for impact.