Archive for the ‘Off Grid’ Category

lead acid batteries

Sunday, October 18th, 2009

Lead acid storage batteries are a heat generating topic on many renewable energy (RE) and recreational vehicle (RV) forums. People are passionate about their misbeliefs. Mike, at the Solar Electric Power Discussion thread on Sam’s Club batteries referenced the DECA service manual for the D series batteries. That one’s a keeper! The manual is about industrial batteries but the description of battery construction and operation applies to all lead acid batteries.

The cutaway illustration (Fig. A-1) shows the construction of an East Penn battery cell. Each positive plate consists of a lead-alloy grid structure which is filled with a paste of active material, made from lead oxide. The active material is forced into the positive grid structure during manufacturing and is held firmly to the grid by a system of vertical and horizontal glass fiber mats, which reinforce and insulate the positive plate. A retainer and bottom shield encase each positive plate and mat assembly to help prevent short circuits.

The negative plate also consists of a lead alloy grid structure that is filled with active material. But because negative plates undergo much less active material shedding, no reinforcing glass fiber mats are needed. Separators provide insulation between the positive and negative plates. The positive and negative plates are connected to their respective posts by positive and negative straps.

There’s also good stuff about battery safety, operations, and maintenance that apply even to small RV and RE applications.

When you run across someone promulgating the ‘true deep cycle 6v golf cart battery’ as the penultimate solution or carrying on about the ‘deep cycle and thick plates’ baloney, get back to a manual like this to find reality.

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Nov 4 results: FCC opens path

Wednesday, November 5th, 2008

On November 4 the FCC cleared the way for the use of TV channel guard bands for I’net access. As TV moves from analog to digital, the need for an empty space, a guard band, between channels to prevent them from interfering with each other is reduced. Getting more TV in less spectrum is the promise of digital TV and this FCC action is an attempt to utilize that promise. It is a second step after auctioning off the upper UHF channels (51 to 80) freed up in the planned transition.

The idea on this use of the guard bands for I’net access is that, while the equipment must still be FCC approved, transmissions do not need a license. There will have to be provision to make sure the equipment does not interfere with nearby digital TV transmissions. This will likely mostly depend upon a location database more than it will signal sensing.

A key feature of using this part of the spectrum is that it is at a lower frequency than the traditional 2.4 GHz WiFi which means it will suffer less attenuation getting into and out of buildings and other solid objects. It will tend to have a longer range with some trade-off for lower data rates.

Joshua Breitbart has a good description in Open the airwaves and the sky’s the limit and why the ‘free is good’ folks are very happy.

Wireless access is not a full replacement for wired connections, but it is a much cheaper way to bring people the Internet. Mobile phones are far more widespread than in-home computers with broadband connections, especially among the groups currently marginalized from the Internet. …

Once you don’t have to rely on big, corporate license-holders to get a connection, you can start to invent entirely new devices and applications. The FCC used the same kind of open platform for innovation with the 2.4 gigahertz band. That led to an astounding array of inventions — cordless phones, remote controls, microwave ovens, and wi-fi routers — all sharing one tiny piece of the airwaves.

Google has been one the primary backers of this idea. Catherine Holahan described their effort in Business Week’s Google’s Plans for the Space Between Your TV Channels

Companies such as Clearwire are providing I’net service similar to that envisioned by Google. This FCC action will make that type of service easier to implement over more area.

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Energy numbers

Sunday, September 28th, 2008

Both solar and nuclear are hitting the news with advances in efficiency and utility. CEO of Hyperion Power Generation interviewed about the Uranium Hydride reactor provides some numbers that yield scope and scale in thinking about energy sources.

  • specifically designed to fit on the back of a flatbed truck at about 20 tons weight and a meter and a half wide by 2 tall.
  • reactor life is 8 – 10 years with 70 Mw thermal or 30 Mw electrical output at about $100 million each. That appears to be about a nickel per kWh.
  • certified ‘walk a way’ design does not need continuous operator monitoring or attention
  • expected factory output is 400 reators per year or 10-12 Gw output – that’s like building more than 10 typical major sized power plants every year. The estimated market opportunity is for half a million of these units.
  • “The waste that comes out of our reactor after powering 20,000 homes for 8-10 years is about the size of a football.”

That’s a pre-packaged solution for powering a 20,000 home community for near ten years.

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