Monday, July 16, 2018

Part 3 - Logistics Series - Getting electricity in an impacted area

Logistics Series Part 3 :

Getting electricity in an impacted area

A while back I attended a talk given by a Salvation Army volunteer who related her experiences volunteering in Puerto Rico in 2017.  She noted that the salvation army thought ahead and built a network of disaster recovery centers each of which with backup power and resources so that they could continue response activities.  Even with backup power it wasn't consistent.  

As an individual responder you need to plan ahead for the devices you need to do your work.

Individual responder device use time:

  • Hand held 2 way radio's (8 to 14 hours or less)
  • Cellular telephones (11 to 16 hours or less)
  • Laptop computer (4 to 6 hours or less)
*These are estimates for ideal conditions and equipment, it should go with out saying that your mileage will vary.

Factors that affect battery efficiency

  • Temperature - Warm temperatures can affect battery life up to a 25% loss in efficiency.  Sub zero temperatures will also negatively affect battery efficiency.
  • Battery Chemistry - Different battery chemistry will affect the batteries use time.  Most rechargeable batteries are NiMH, Lithium ION or Lithium Polymer.  Lithium batteries having the most efficiency and capacity.
  • Amount of use and energy efficiency - enabling energy efficiency features on cell phones and laptops will make a big difference in battery efficiency.  Radios are typically idle 95% of the time and only actively used 5% of the time.  Heavier the active use, the more power will be used.

Power consumption:

  • Radio - 5Watts @ 12v, ~410 milliamps per hour
  • Cell phone - ~130 milliamps per hour
  • Laptop  - ~3Amp or more per hour

Battery ratings

Batteries are often rated in Amp hours or Milliamp hours.  
A cell phone charger is about 1 or 2 amp hours, a vehicle sized 12v gel cell is rated around 50 Amp hours.

Recharging your devices:

  • Hand-crank generator
  • Solar Cellphone charger
  • Portable Solar charging system with storage battery
  • Fuel Cell - Hydrogen fuel cells allow for power generation when it isn't sunny
  • A large storage battery or lots of little batteries 
    • A large LiPO storage battery capable of charging multiple devices of different voltages
    • A large amount of standard AA batteries
    • Multiple small LiPO battery chargers
    • A deep cycle or gel cell marine battery
  • A thermo-electric generation system (ex. Biolite)
  • Vehicle charger cord
  • Portable wind turbine generator
  • Gasoline electric generator

The fine print

Lithium Ion and Lithium Polymer batteries are very sensitive to temperature and charging conditions.
Only use the charging cable and cords for your device, using any other charging devices may cause the battery to be damaged, catch fire or explode.  

Different types of battery cells have different voltages.  Nickel Metal Hydride (NiMH) AA rechargeable batteries are 1.2 Volts which is slightly less than a standard AA Alkaline Battery.  Most devices can handle slight differences in voltage but abnormal voltages can cause the a device to behave abnormally.  

When using large gel cells or car batteries, be extremely careful not to accidentally connect the two terminals together causing a short circuit.    Short circuits can cause a fire and chemicals in batteries if released are toxic.  Also since large batteries carry larger amounts of power be careful not to electrocute yourself by touching bare leeds or broken wires.

Generators and fuel cells use flammable liquids or gas which can explode when exposed to heat and fire.  Generators often release carbon monoxide which can be poisonous in confined areas.  Always run generators outdoors and away from work spaces.  Always store fuel away from heat and fire sources.  Gasoline and other fuels are bad for you so when handling fuel or any other chemicals use due care and wear appropriate personal protective equipment.

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