DC Electrical Distribution Systems for Buildings?

[jmbelectrical]

I recently became aware of its existence through a few trade magazines and thought nothing of it, but our marketing person is convinced that it's the future.

From what I understand, the basic idea is for the incoming AC service to be rectified into a 380V DC system, which would serve large appliances and HVAC systems. Lighting loads would be served by a 24V DC system. In addition, 24V, 12V, 5V, and 3V receptacles would be available for cord-and-plug loads. As for its merits, such a system is supposedly more efficient and easier to tie into photovoltaic, wind, and other renewable energy sources.

How could it possibly be more efficient than an AC system? There will be losses in the head-end rectification, and, on top of that, I imagine that the (i^2)R losses in lighting and receptacle branch circuits would be massive, given their low operating voltages.

What are everyone's thoughts on this?

 

[jghrist]

Don't hold your breath waiting for this to happen. Even if a majority of new homes switched, the marketplace for dc lighting and appliances would be miniscule for decades. There will be little incentive for manufacturers to start making the stuff and without the availability of economical dc appliances and lighting, there will be few homes built with dc distribution. You will have a major chicken and egg problem. Ask me again in 100 years.

This is without even getting into the technical problems. And why? Just to accomodate "renewable" energy?

 

[MAGTiger]

jghrist! you've written the magic words, "renewable energy". If it's in the name of renewable energy, they it shall be done and cost will not be an obstacle. Politicians will be falling over themselves to throw money at such a project.

Neil

 

[dpmac]

So I guess Edison was right after all.

 

[PHovnanian]

A couple of issues:

Voltage drop and I^2R losses for low voltage distribution. The lower the voltage, the worse the problem for centralized DC supply architectures.

Converter efficiency. Not good unless the converter is loaded near its design operating point. So central DC supplies that have ratings sufficient to support peak DC loads will be under loaded most of the time.

Circuit protection. You lose the benefit of having a zero voltage crossing to assist in extinguishing an arc.

Standardization. Which voltage(s), current capacities and connectors will we use?

It might be convenient to have some DC outlets distributed around a home or office to eliminate the rats nests of wall warts or line lumps we presently have. A 5V USB power/data hub at outlet positions would be an interesting device. Possibly integrated into a standard AC outlet. But I don't see DC distribution from a central panel as being viable. The AC to DC conversion can be done easily at the point of use.