Tuesday, December 20, 2011

A 12V DC home

Since my days in electrical engineering, this question has been bothering me: Most of the devices at our home that need electricity, need low-voltage DC power, not 230Volts AC.

The ones that do, are either run on AC just because DC isn't readily available (ceiling fans, washing machines, vacuum cleaners)..

..Or can now be succeeded by next-gen devices with far better performance and lower power consumption (CRT Vs. LCD displays, fluorescent tubelights Vs oLEDs)...

..And the rest are simple resistive circuits that run on both - including the traditional light bulbs, water heaters, kettles, toasters.

In fact, I'd say the only real uses of high voltage grid AC power supply are industrial ones where 3-phase synchronous motors and the like are needed. Homes and shops and offices : why bother?

The appliances we use at home usually have most of their weight in a hefty step-down transformer sitting inside the casing that converts the supplied power into a much safer 12 Volts, which is then converted into DC by AC-DC converter circuits. Crack open a computer's SMPS or a kitchen mixer or a TV and you'll find one inside. Laptop charger cords and mobile charger cords now have lighter electronic converters (albeit with a much shorter lifespan)
But now, a neighborhood biogas plant, a local wind turbine, a fuel cell, a solar panel can directly supply that low-voltage DC power! But unfortunately the electrical appliance industry today designs all products in a way that we need 230V AC (In India - in some other countries there is 110V also which is quite stupid as plugging into the wrong socket causes several faults, malfunctions and fires).

It's just so ridiculous, seeing that the AC-DC conversion results in inefficiency and power wastage! (and you can feel that in your power adapter heating up). If you wanted to switch to an off-grid electric supply today, you'd have to contend with this mind-boggling multi-step wastage:
1. Take the renewable-generated power and store it in a battery - WASTE POWER but unavoidable unless you're using fuel cells or your biogas turbine runs 24/7
2. Convert the electric power from LV DC to HV AC using an inverter - WASTE POWER
3. At the appliance end, convert the HV AC back to LV DC - WASTE POWER.

No wonder the entire grid power industry keeps gloating that getting off the grid is impractical - the present system we've been using since some decades makes it impractical for no fault of the poor little wind turbine or solar panel! And here we're not even looking at the issues of the actual things that are generating the power - it's purely the conventional systems at the user end that's wasting half the power away!

If the designers and the industry had had the foresight and had included an alternate DC supply socket in every electrical appliance that actually uses DC on the inside, then every home could have readily switched to off-grid renewable energy. Instead, the few expensive examples we see today, probably waste half of the renewable energy put in.

But the industry has locked us in.

So now I'm foreseeing a major demand cropping up for an industry in parallel with the rise of local renewable power replacing the grid : an industry that will re-wire and retrofit all existing electrical appliances to include a DC power socket. In most cases this will be as simple as drilling a hole in the casing and fitting a socket that will skip the transformer/converter sections and hook up directly with the device. Some rudimentary over-voltage and polarity protection will also be in order - but at the low voltages like 12V, it's easily doable. It's very simple, but essential for the concept of off-grid homes to turn to reality.

An offshoot of this: Say goodbye to the eternal safety hazard of the electric socket and switch. A person or child accidentally touching both terminals of a 12V DC outlet will NOT suffer intense burns; a short-circuit at this low level of voltage will be cut out by the protection system long before there can be any fire hazard (unlike 230V AC where the spark can burn someone or set things on fire and only AFTER the spark does the protection fuse kick in). The main fusebox, etc will longer be a very very dangerous place in the house. This "side-effect" of converting a home from AC to DC can be marketed as a major safety enhancement for the family.

Of course, it doesn't have to be this or that - we can have a transition model having both LV-DC and AC sockets available. Several homes in areas of frequent power cuts employ an inverter system anyway which kicks in when the power is out, replicates the 230V AC supply from the battery storage and powers most of the house sockets. In fact, these houses are great potential off-grid converts as you simply have to hook up the renewable power source with the existing battery and extend circuits from there to give DC power outlets to the whole house.

A house with DC sockets and appliances running directly off it - hoping I get to see this idea converted into reality some day!

14 Feb 2013 Edit: This entrepreneur, Gunter Pauli, is DOING IT! Check out his video/audio talk from this article: http://www.abc.net.au/tv/bigideas/stories/2011/08/16/3293620.htm at 51:00 mins!


Jeff Hardy said...

nice post. Now you can use this importers directory india to promote home appliances import & export business.

electrical services perth said...

informative stuff
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Nikhil Sheth said...

This entrepreneur, Gunter Pauli, is DOING IT! Check out his video/audio talk from this article: http://www.abc.net.au/tv/bigideas/stories/2011/08/16/3293620.htm at 51:00 mins!

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