Slashdot Mirror
How Tesla Batteries Will Force Home Wiring To Go Low Voltage
CIStud writes with a story at CEPro suggesting that solar power and home batteries like Tesla's PowerWall "will force the reinvention of home wiring from primarily AC high voltage to DC home-run low voltage to reduce power conversion loss," writing "To avoid the 20% to 40% power loss when converting from DC to AC, home wiring will have to convert to home-run low-voltage, and eventually eliminate the need for high-voltage 110V electrical wiring." As a former full-time Airstream dweller, I can attest to the importance of DC appliances when dealing with batteries.
DC in the home is only viable due to recent advances in power silicon. AC has its problems, but the genius of AC power is that you can controll it with nothing more than carefully arranged windings of wire and big chunks of metal. Transformers, inductors, capacitors, and resisters can all be made with nothing more than properly arranged and chosen wires and metal blocks. There was no practical DC-DC conversion in Edison's day. Even AC/DC conversion was tricky, often requiring an AC motor with a shaft mechanically linked to a DC generator.
Edison did not have the IGBT
http://en.wikipedia.org/wiki/Insulated-gate_bipolar_transistor
Today, that's different.
You can make tiny, tiny, cheap little AC-DC or DC-DC converters that are dozens of times cheaper and many more times efficient than their counterparts made even a decade ago. What used to require large arrays of MOSFETs and many many pounds of expensive copper windings (And the design/volume/heatsinks/fans to deal with all the waste heat!) is now handled by a much smaller transformer, a handful of inductors, and some advanced switching silicon controlled by a fairly smart processor. You also, thanks to increased efficiency, don't need to overbuild with expensive heat tolerant components so much. (Heat shortens component lifetimes, particularly caps)
And they're already deeply commoditized because, guess what, the chinese are big in to solar. (They know they are going to need it. They're quite aware that traditional energy can't economically fully meet their future demand.)
> If you're using somewhere near the inverter's peak output, then you can get as much as 90% efficiency
These days inverters are much better than that. To use a random product that is currently shipping, an SMA Sunny Boy 5000 runs at 95.5-97% efficiency. Bigger inverters are even better with some commercial scale monsters at 98% efficiency.
The original article is pure nonsense. There are already three port inverters on the market. Those ports are: your 120V AC, your solar array, your battery bank. If the energy is going from the solar array to the battery there is simply no intermediate conversion to AC. With a three port inverter, there is only ever a single conversion from DC to AC. And, as I previously mentioned, will only get hit with a 3-4.5% loss. There is simply no way the world is going to change how electricity is delivered to avoid that.
Since the Tesla Power Wall is pretty much for sure going to be a high volume product, there are inverter manufacturers falling all over themselves to design and build three port inverters specifically optimized for the Tesla product.