Is this the LED bulb we’ve all been waiting for?

Switch in the fourth quarter will begin to sell LED bulbs to consumers that could help take the sting out of the criticism and complaints surrounding LEDs.

First, it will be cheap. The Switch75, a 15.5-watt bulb that will emit 1100 lumens, or about the same as a 75-watt bulb, will likely sell for around $20 to $25. By contrast, existing high-end LED bulbs sell for $60 or more. (If you are at Lightfair in Philadelphia next week, stop by and see it.)

“It will have a one-year payback,” says Brett Sharenow, chief strategy officer. “It will save you $150 to $200 in energy costs over its lifetime.”

The bulbs put out a nice amount of warm white light that gets dispersed in an even pattern. If you didn’t know better, you’d think it was an incandescent.

To top it off, it comes with a wacky technology backstory that will, ideally, let Switch market them as a fashion statement. The consumer electronics-ization of bulbs is one of the unanticipated, but growing, trends in green.

So what’s the secret? The bulb dome is filled with a nontoxic liquid that draws heat away from the LEDs housed inside. The liquid next to the LED chip gets warm, and then flows outward to the skin of the dome as it warms. At the edge of the dome, it cools, only to be drawn back in.

“We’ve seen eddy currents in the dome,” he said. “There is an environment that is created that cools the LED passively. Our glass is as hot as the heat sink.”

While the bulb in the videos sport a frosted white dome, Switch will also sell one with a clear dome. It will have the same characteristics but it will let consumers see the intricate electronics and catch the currents. Consumers, the company predicts, will buy the clear ones because of the novelty factor.

The liquid is more than an amusing example of convection, like those Christmas lights that bubble. In this case, it is actually a conscious engineering choice. One of the key problems with LED bulbs remains power delivery. Although the light from LEDs is not warm, the LED chips and the drivers in the bulb generate waste heat. Typically, the heat from both the LEDs and drivers gets dissipated by a finned aluminum heat sink.

Heat sinks, however, can only eliminate so much heat. To increase their performance and functionality, manufacturers have to add more metal, which increases bulk and cost. It also limits the input power. Most Edison-shaped LED bulbs are limited to a 12-watt power input, he said.

Philips gets around these limitations in part with its EnduraLED bulb, which extends the aluminum heat sink into the dome itself. That explains the metallic stripes (see video) and the unusual shape of its bulb.

By filling its dome with liquid, Switch effectively takes pressure off of the aluminum heat sink. Most, but not all, of the heat from the LEDs gets dissipated by the liquid. Unlike most LED bulbs, you can’t touch the glass bulb: it is warm.

The design twist also opens up a host of other advantages. Switch, for instance, can drive more power into its bulb. As a result, it can put in fewer LEDs, but run them at full power. Some 60-watt equivalent LED bulbs contain 18 LEDs. The Switch bulb only contains 8, but each one receives 1.4 watts of power instead of 0.6 watts. In the end, this leads to equal or greater light output.

“We get the maximum brightness out of the LEDs,” he said.

Fewer LEDs also means less cost. LEDs account for around 65 percent to 80 percent of the cost of a bulb.

Additionally, the bulbs can be arranged in a radial pattern, sort of like sections of an orange, because they are bathed in cooling fluid. Because of the heat carrying capability of the liquid, Switch has also managed to taper the edge of its heat sink, allowing light to be emitted in a global manner, much like an incandescent.

The company initially started out with the concept of filling the dome with a clear gel containing reflective particles to diffuse the light. Optically, it worked. The gel, however, didn’t flow well and the heat remained concentrated at the light source.

The liquid, Sharenow adds, is non toxic and the bulbs will survive at least a three-foot drop. Is color an option? Sure.  You can also put the bulb in an upside-down socket without heat getting concentrated at the socket.

The company will initially come out with a series of residential bulbs: a 40-watt equivalent (actual power consumption 9 to 10 watts), a 60-watt equivalent that will put out 800 lumens (13 watts actual), and the 75-watt equivalent. The 40-watt bulb will sell for under $20. The company will vary the warranties (3 to 5 years) and lifetimes on bulbs (25,000 hours to 50,000) depending on the price and the internal components.

Later on, it will make candle bulbs and other bulbs in various shapes. Manufacturing will start in the U.S., but a volume manufacturing facility will get built in the first quarter of 2012. The company buys LEDs from a number of sources, including Lumileds. Bridgelux, however, could become a consistent partner. Both Bridgelux and Switch are VantagePoint portfolio companies. VantagePoint partner Alan Salzman has said that when LED bulbs hit $20, utilities can give them away for free as a way to curb peak power. There is no guarantee that Switch can scale or even make a dent with big-box retailers. Nonetheless, there are a lot of compelling drivers here.

Will others make liquid bulbs? If Switch succeeds, there’s a good chance others will tinker with the concept. Progressive Cooling in Berkeley is working on a technique for employing liquid-filled membranes to cool LEDs. The concept hails from Russia. Another advantage of liquid cooling is that it is passive. Both General Electric and Nuventix have created tiny jets for air-cooling LEDs, but with liquid physics that does the work.

Switch (formerly called Superbulbs) has 23 actual and pending patents.

Thus, if you start to play with liquids yourself, you might face a lawsuit.