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Solar PhotoVoltaics + LiFePO4 batteries Current state of technology
  • Vote Up0Vote Down
    February 2012
    @ All

    It is true that Solar photovoltaic panels have been very expensive in the past, however their prices have dropped three fold from 3 years ago and still dropping, wholesale price for thin film panels of 0.65$/watt ( Coupled with the fact that lithium iron phosphate batteries are also becoming cheaper  ( ) 0.35$/watt-hour of energy storage potential. 

    What does this mean for GVCS? that we need to concentrate on opensourcing these technologies too. For those of you who are not very aware of the advantages of these two technologies, Solar PV panels will virtually last you forever 25 years warranty on power, and new generation of lithium yttrium batteries which can be recharged thousands of times at 80% depth of discharge = more than 10 years of usage before they fall to 80% of their capacity rating. , I am currently working in a solar energy distribution company and the only thing that is preventing mass deployment of both these technologies is the costly balance of systems(BOS)  like charge controllers, inverters, mounting hardware etc which i frankly believe do not cost so much and this is where open source ecology be used to show that these BOS could be easily produced and sold at 1/10 their market price. 

    Any and all comments are appreciated. I would also like to see some action in the near future, we cannot ignore these two technologies.

  • 7 Comments sorted by
  • Maybe it could be wrapped up in the universal power supply? We'd be working on something for managing the charge of batteries anyway.
  • Photovoltaic works great in the American Southwest, and it sucks in the Pacific Northwest (Seattle).  There is no single answer that works everywhere, so we need to think in terms of a toolbox containing (solar, wind, biofuel, small scale hyrdoelectric, and others).  For a given location, you then pick the energy systems that work best for that area.  PV panels are pretty specialized to make, but we can certainly look at supplying the mounts, trackers, etc.  I'm partial to solar concentrators with gravel bed thermal storage.  More of that can be self-built, but the optimal mix might end up being PV for electricity and solar-thermal for water and house heating.  Until we have more finished designs, we can't say what the best combination will be.
  • Vote Up0Vote Down
    February 2012
    @ Daniel very true but then I have used this solar energy calculator called PV watts by NREL to calculate the energy yield in the state of washington( a huge part of it actually)  using a two axis tracker one can have close to 7 hours of peak sun( averaged through out the year (individual months vary) . after you select your desired location just press send to PV watts and it gives you a summary of the monthly outputs and the annual average. 

    Another good idea for OSE would be 2 axis tracker the current market costs are prohibitively high to make them viable but i guess we can do something about it.

    @Matt yes the Universal Power supply is the combination of a AC to DC coverter(battery charger) and DC to AC(inverter) but it does not directly involve the batteries or the solar panels these should be considered more of projects in themselves. like the solar collector project or Ni-Fe battery.

    Where I work we also sell flooded lead acid batteries which are the cheapest (0.15$/w-hr), sealed AGM batteries which are zero maintenance lead acid batteries (0.25$/w-hr) but these have an optimum life of 1500 cycles at 50% depth of discharge for the flooded batteries(they need maintenance are refilling of distilled water every month) and only about 1000 cycles at 50% depth of discharge for the  AGM batteries. compared to these numbers a LiFePO4 battery costs 0.35$/w-hr has 2000 cycles at 80% depth of discharge. so already they are competetive with these technologies in the long run are maintenance free and benign have no heavy metals or spillable acid in them and have a life of  atleast 10 years. The only obstacle to their wide spread deployment is the battery management systems which are used to charge these batteries are an added cost, without the BMS these batteries have very poor life.
  • Vote Up0Vote Down
    February 2012
    I guess the battery management system is a little more that just limiting the voltage to 14.4 volts or what the manufacture is calling for. I have 150watts of solar in my motorhome and use a  AGM right now. After 6 years its just about had it. Something more durable would be nice.
  • Vote Up0Vote Down
    February 2012
    @surfcam you are right, unlike for an AGM battery each cell of a LiFePO4 battery needs to be equalised since each one is around 3.2V nominal a 12 volt battery would consist of 4 of these in series and each such has to be monitored properly . I would like to know your usage pattern for the 6 years that it worked. because they would not last even 2 years if they were discharged daily to 70% of their capacity.
  • Rahul,

    I  was at a small EV  showcase back in Canada before I left to China (now in India).   Most newer EV's   are using the LFP batteries from China. There's a few main makers of these but i can't remember them at the moment.   I think back in Canada people were paying about $1 per AH.  When i was in China (Chengdu) about90% of the scooters and 2 wheelers   were electric. Most were still lead acid.   so cost for newer LFP   has not come popular enough for local use. 

    .  Prices for  avg. LA batteries here  (near Calcutta)  are in the $1,5/AH range.   Currently designing a 10kW  PV grid connected system for the school and battery backup alternative to lead acid is definitely being considered.  More feasible now is experimenting with battery power  for a small off  grid street lamp system  for LED's   and a EV scooter mod.


  • Well to add to this, maybe we should be looking at combinations of stuff like the iJet stuff that the materials student in Australia puzzled out (deposition coating using an inkjet printer, aluminization and curing using a low temp oven), as well as something like this for storage??

    The documentation on the iJet stuff is fairly limited but it resembles the concepts I read about for prototyping large circuit traces.

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