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Parallel DC electrical wiring in solar homes. |
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Score
82%
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19 votes,
Feasibility
86%
Originality
66%
Humour
49% |
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The Problem:
Wasted energy converting between AC and DC current and back again. Excessive hardware in consumer electronics.
The Social Invention:
Currently in the U.S. we have a residential electrical standard of 120 volt 60 hertz alternating current wiring in our homes. The new standard in the European Union is 230 volt 50 Hz AC. These standards have been developed to allow everyone to receive energy from the local electrical grid, and pay a large electrical utility for access to that energy. These standards also make possible the convenience of compatibility with any local appliances.
As small-scale solar and wind generation continues to appear on people's rooftops, a new standard is possible. Most residential solar systems generate 12 volt direct current: DC because the panels utilize the photoelectric effect; 12 volt, because compatible batteries are ubiquitous in automotive and marine shops. Instead of using a huge bank of batteries to store energy for later usage, many solar installations are using "net metering", where the city's grid is essentially used as the battery, running their electrical meter backward at the times they're using less than they're making.
This is a step in the right direction, but we can go further.
Whether using batteries or net metering, a solar installation requires the use of an inverter, to raise the voltage and alternate the current, so it's ready for either our appliances or our city electrical grid. What if, in addition to our AC wiring system, we also have a DC wiring system to selected areas of our solar home? There are many appliances that already use low-volt DC internally, by using an embedded transformer. Consider home electronics. A desktop computer uses a "power supply" to take AC electricity from the wall and pass it through a transformer to make low-voltage DC current for the computer inside. A laptop computer, cell phone charger, stereo equipment, low-voltage lighting... All these devices have their own individual transformer.
So in our current solar homes, we have 12V DC current from the roof panels, converted to 120V AC to conduct on wire into the kitchen, where it's converted back to 12V DC to power the electronic wall telephone. Each time the energy changes form, a significant amount is lost as heat, and each location where this occurs creates an electromagnetic field, which raises health concerns.
I propose a solar home design with both an AC and a 24V DC side. Each room would be wired for AC as usual, and additionally, at least one DC receptacle per major room with a different style of standardized plug. The DC side would consist of the generating equipment (solar panels), the DC distribution wiring and receptacles, and possibly a small bank of batteries (or fuel cells, when available) to handle a large fraction of the nighttime DC needs. On the other side of the inverter would be the conventional AC wiring, and a net-metering connection to the outside world.
This system would be more energy efficient than universal AC systems, because it minimizes the energy flowing through transformers and inverters. yet it would continue to offer as many AC receptacles as before. The only difference the user sees is a DC plug in each room. DC appliances that require a voltage other than 24V could step the voltage up or down, but it would be a much smaller change than from hundreds of volts of AC. For the electrician, it means running a separate wire into each room, but since it's low voltage, it doesn't carry the same fire or electrocution risks as with conventional wiring. Consequently, it doesn't need to be protected with conduit or enclosures, and can be run with more casual methods, like phone wire.
DC plugs are already standardized. Take a look at the end of a "power block" cord. It should look like a little metallic tube about a centimeter long and a little narrower than a pencil. The size of these connectors varies with the voltage it provides. The DC wall receptacles could be exactly this standard.
At first, there would be few appliances available to use unmodified on the DC side. But as more people use DC at home, the requisite appliances would begin to appear. Existing appliances could be retrofit as well. If you have an appliance that uses a transformer block cord, you could just discard the cube-to-DC cord and use a little double-ended DC-to-DC cord instead. If you have an appliance that plugs into a car's cigarette lighter, you could either use an adapter, or cut off the bulky cigarette lighter plug and replace it with a little pencil plug. Eventually though, appliance manufacturers will offer ready-made DC appliances. All they need to do is remove the AC circuitry making it smaller, lighter, lower cost, and safer.
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I try to keep my quality high, in the face of relentless mediocrity. I live in Berkeley, California, at a place called the Wormhole, and am a maker of things.
http://members.cruzio.com/~loqi/
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