A DIY Green Machine of a Home


A smart sensor network drives lights, thermostats and motorized shades in this San Francisco do-it-yourself treat.

Nov. 02, 2009 — by .(JavaScript must be enabled to view this email address)

Tahl Milburn has no problem admitting to his geek-hood. By day he manages a strategic IT consulting practice in San Francisco, “but my top hobby has been home automation since I was 12 years old,” he says.

A couple of years ago when he moved into a new 2,600-square-foot home with panoramic views of San Francisco Bay, Milburn repeated the same DIY performance that put him on the cover of the March 2003 issue of Home Automation magazine, formerly an EH sister publication.

This time, though, he decked the pad with all manner of energy-saving mechanisms, including photovoltaic (solar) panels. He wasn’t convinced that solar energy would ever pay for itself, but when San Francisco added a city rebate to the California and federal rebates, he took the plunge. Also influencing him was the fact that his energy use was 300 percent above the baseline for the area. Ah, the price of geekiness.

The photovoltaics, however, are just one element of Milburn’s energy-saving home technology.

Zoning Out
Solar energy is nice, but it isn’t terribly fun. On the other hand, Milburn takes great pride in the 50,000 lines of code he’s written for his home automation system. That system starts with a pair of highly capable Stargate systems from JDS Technologies, one of the original purveyors of home control systems. On top of that, Milburn uses StarCOM software from Pine Tree Systems, which makes software servers specifically for JDS products.

His own implementation of home automation adds a software layer on top of StarCOM, and Milburn calls the resulting solution Liam, short for Lifestyle-Integrated Automation Machine.

Milburn has partitioned his home into zones—office, exercise room, bedrooms, kitchen and so on—and Liam uses occupancy sensing and “neural network algorithms” to determine which zones of the house to set back at any given time.

Devices like thermostats and lights adjust to each zone’s occupancy, but so do electronics like printers, monitors and A/V gear.

Sounds risky? Not for Milburn, who says his algorithms are advanced: “It will go from knowing for sure that a zone is occupied to probably occupied to certainly unoccupied.” The system errs on the side of occupancy, and “I get a page on the ‘probablies,’” he adds.

The do-it-yourselfer uses a variety of standard security sensors (motion, door/window, etc.) to gauge activity in a zone, but he supplements those with some nontraditional triggers. For example, the JDS Stargate system can sense when a phone is off the hook—a sign that a certain area is occupied. In the exercise room, a power sensor connected to Milburn’s massage chair lets Stargate know to keep the room revved.

The Perfect Temperature
A guy like Milburn would never settle for your basic setback thermostats. He even scoffs at some of the better communicating thermostats that integrate with automation systems.

No, Milburn controls heating, ventilation and cooling (HVAC) his own way. It starts with multiple smart thermostats from Residential Control Systems. Each unit has four different set points: The most extreme setback occurs in VACATION mode, followed by UNOCCUPIED, then ASLEEP and finally OCCUPIED.

A few algorithms were required to coordinate the modes with the neural network, but it’s child’s play for Milburn. Enter the motorized shades. “My house faces east and west,” he says. “If it’s too warm, the shades will lower automatically.”

Again, no big whoop for Milburn. “Where it’s pretty smart is with the weather station,” he explains. “Being in San Francisco, it can be foggy, so the system uses a combination of the intensity of the light, plus whether or not it’s foggy. It could be bright but foggy, so it’s OK to leave the shades up.”

There’s one more thing: The Davis Weather Station, together with an hourly feed from the National Weather Service, can help predict the weather. “Depending on the forecast,” he says, “if it’s going to get cold, I will start warming up the house using the motorized shades. They will stay up longer even if it’s a bright day.”
And if Milburn had his dream motorized windows, “they would know when to open up.”

For the time being, Liam will verbally suggest he open one or more windows to modulate the indoor temperature. Milburn can go to his Liam site any time, from his home or on the road, to check up on the house and make adjustments as needed. EH readers can check it out at www.liamsite.net.

Solar System
Milburn had no intention of installing the photovoltaics himself, so he hired a local firm, Luminalt, to do the job. He chose the company because they had excellent service, the best price, a good choice of attractive panels (Sunpower), as well as a gateway that he could hook into for home automation.

Through Luminalt, Milburn can track his solar-related energy savings by day, month or year, but he is waiting for the final piece of the utility-integration puzzle: The Energy Detective (TED) 5000-SG model energy monitoring device.

With that, he says, “I have the final part to monitor both sides, supply and consumption, and hook into Liam.”

For its part, Milburn’s utility provides info on the net energy usage for each of its three time periods: peak, semi-peak, and off-peak. “I’ve gone onto a different charge plan called Time of Use, in which you’re charged more during peak time and less during off-peak times, compared to normal rates,” Milburn says. “Since peak times happen during the day, I essentially have a multiplying effect with my solar system.”

The next step for Milburn? “I want to manage the use of certain optional devices for times when electricity is off-peak.”

Click here to view additional information and photos.

Solar panels with installation: $45,000
City rebate: $6,000
Federal, California rebates: $8,000
System cost after rebates: $31,000

HOME SIZE: 2,600 sq. feet

Monthly electric bills: $12 (In 2010 the utility will owe the owner money)
Panel life: 25 years+
Inverter life: 15 years
ROI: About 10 years

4.7-kilowatt photovoltaic system
RCS Thermostats
JDS hardware, software
and always-on PC server/media server
Hunter Douglas motorized shades
Powerline Control Systems X10 devices
Davis Weather Station
RCS keypads

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