One of my current projects is a small RV teardrop trailer. I wired it for 12 volt DC and standard 120 volt AC electricity. I also have small energy projects in the home that produce DC current which must go through a grid-tie inverter for use in homes as AC current. Interestingly enough a lot of that AC current is then converted back to DC at individual devices within the home. A little thought and research has convinced me that homes should be wired for AC and low voltage DC electricity.
Reasons for using AC current
The AC grid and power generation system is already in place.
High voltage Long distance AC power transmission is efficient.
AC generators and motors are simpler, less costly, and durable.
Reasons for using DC current
Low voltage (24v) DC is safer.
Can generally use the same wire gauge in the home as standard AC electricity.
Any device that uses transistors requires DC. This means computers, TVs, smart phones, tablets, game systems, cameras (I love my digital cameras).
DC lighting.
Alternative energy systems are DC.
Logistic problems
Distribution within the home for AC or DC using appropriate plugs and connecting devices.
A DC standard–such as 24 volts–would need to be instituted. Devices using other DC voltages would require a DC to DC converter but these are much more efficient than power bricks which convert 120 volts AC to DC. The heat off the power bricks is wasted energy.
Homes would need a rectifier where power enters the home for conversion to DC. Rectifiers can be very efficient–up to 97%. AC and DC power would need separate distribution panels.
A possible scenario
Standard 120/240 volt power to the home. Main AC power through breakers to the home, a shop and a secondary panel through a rectifier for 24 volt power. AC plugs spaced throughout the home for appliances such as microwaves, toasters, fans and vacuum cleaners. Dedicated AC circuits to stoves, ovens, pumps and air conditioning systems. DC plugs spaced throughout the home for computers, TVs and other low voltage DC appliances. Dedicated DC circuits for fluorescent and LED lighting.
This ignores possibilities from alternative energy systems that may be incorporated in the power system.
Studies indicate that within 20 years up to 50% of the power used in a home will be DC. Savings could be substantial. A 2010 study by Electric Power Research Institute (EPRI) found that a Duke Energy datacenter DC power system used 15% less energy than an AC power system. General Electric (GE) claims that a DC datacenter would cut energy costs up to 20% simply by cutting power conversions which lowers cooling costs. Stuff to think about.
