I recently attended the 8th Annual UC, CSU, CCC Sustainability Conference, and I wanted to piggyback off of Julia’s recent posts with a little information on some of the technological ventures that were discussed at the conference.
One topic of interest was the conversion between DC and AC power that takes place during the electricity delivery process. Homes and commercial buildings are all wired with AC power, but increasingly our electricity use is DC. For both lighting and HVAC, DC, digitally-controlled systems allow for a variable system that is more efficient and easier to control. The new trend in energy production is also toward DC. Wind, solar and fuel cells all produce DC power. When it enters a home or office building, it has to be converted to AC, then converted back to DC. I’m no engineer, but this seems silly. The topic was presented at the conference by Brian Patterson of the Emerge Alliance. He argued that wiring a home or office building with DC power so that it could take DC electricity generated from solar panels and use it directly for lighting, HVAC systems, and data centers (computers convert power to DC!) could increase the energy efficiency of the building by 15 %.
Another intriguing tech fix was the use of photocatalytic TiO2. This actually came up in a session on green cleaning. George Beveridge and Larry Eisenberg of the LA Community College District explained that they were coating campus buildings with photocatalytic TiO2, a substance that reacts with dirt, dust, bacteria, and even VOCs in the air, oxidizing them and reducing them to harmless elements (although one site I found named CO2 as one of these harmless elements). This meant they no longer had to wash the outside walls of their buildings, saving money and water. Beveridge also argued that the buildings cleaned the air, removing 80% of NOX emissions. I’m not one hundred percent sure what I think about this coating. I’ve only looked into it a little so far, so any research anyone else has done is greatly appreciated. There was one application that I found especially interesting – solar panels! A lot of community colleges have put up solar panels atop parking lots on campus (mostly funded by PG&E grants). As solar panels get dirty, their efficacy drops as much as 20%. Beveridge encouraged the coating of solar panels with TiO2 to keep them at the maximum efficiency levels.
Whoa! This is something to keep an eye on.
Thanks for the info.
By: walnotes on July 6, 2009
at 7:22 pm
My brother is an engineer. He knows a lot about a lot of things. His response is below:
“you can probably find a more thorough answer somewhere but here is the short story as i remember it.
power is generated as DC because most things that make power do so continuously and so the current is steadily flowing in one direction.
transmitting power over anything more than short distances is inefficient as DC. power is lost to heat, magnetic field creation, etc. Instead the power is converted to AC which travels fairly well.
closer to the place where the power will be used it is sometimes converted back to DC for certain tools and types of motors. DC is used for arc welding and DC motors, which i believe tend to be more powerful.
regular items like vacuum cleaners, tv’s and alarm clocks are build to run off AC power, not because they have to but because thats what is available. The AC power that is on the power grid could be converted back to DC closer to the place of usage everywhere but power is lost each time the current is converted from AC to DC and vice versa.”
By: walnotes on July 7, 2009
at 4:48 am
I was going to make the same statement on the DC power.
the battle between Edison and Tesla lives on!
By: Zach on September 20, 2009
at 7:57 am