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Energy Storage Student Lutz Steiner of Team Germany, looks over the solar panels on his team’s house during the 2009 U.S. Department of Energy Solar Decathlon on the National Mall in Washington, D.C., Monday, Oct. 05, 2009. – Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon, CC by SA 2.0

Published on June 20th, 2014 | by Roy L Hales

51

The Key To Germany’s Solar Potential Is Energy Storage

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June 20th, 2014 by
 

Originally Published in the ECOreport

Student Lutz Steiner of Team Germany, looks over the solar panels on his team’s house during the 2009 U.S. Department of Energy Solar Decathlon on the National Mall in Washington, D.C., Monday, Oct. 05, 2009. – Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon, CC by SA 2.0

Student Lutz Steiner of Team Germany, looks over the solar panels on his team’s house during the 2009 U.S. Department of Energy Solar Decathlon on the National Mall in Washington, D.C., Monday, Oct. 05, 2009. – Photo by Stefano Paltera/US Dept. of Energy Solar Decathlon, CC by SA 2.0

Between 1 pm and 2 pm on Friday, June 6, Germany’s solar photovoltaic systems generated a record 24.24 GW. The real peak came three days later, when they provided 50.6% of the nation’s electricity, which shows solar technology’s potential. The current reality is that solar contributed only 6% of the nation’s electricity during the first five months of 2014, but this will change. The key to Germany’s solar potential is energy storage.

On A Residential Level

Typical Solar Installation. Solar is everywhere in Germany. This is a newly constructed home with near total solar covering – Courtesy Tim Fuller, thetimechannel, CC by SA 2.0

Instead of relying on the grid, some solar users store energy and only feed the excess to the grid, then only draw upon the grid when their batteries are depleted.

Close to 7,000 of these battery systems were installed in 2013.

Tobias Rothacher, renewable energies expert at Germany Trade & Invest, expects to see more. Battery sales will increase as their price falls, and once battery parity is achieved, possibly “within the next two years,” the majority of PV sales will probably be in conjunction with battery.

He explained, “Since the cost of electricity from PV is significantly lower than buying energy from the grid (~EUR 0.15 PV vs. ~EUR 0.30 utility), customers want to use as high a proportion of electricity from their PV systems as possible. If they were to feed the electricity into the grid, they would only receive a feed-in tariff of around EUR 0.13 – meaning that self-used energy from PV is worth twice as much as energy fed into the grid.

Rooftop solar solars with “PV-only” systems only obtain around 30-35% of their energy from solar, and their excess electricity ends up on the grid.

Emmendingen railway station – Till Westermayer, CC by SA 2.0

Emmendingen railway station – Till Westermayer, CC by SA 2.0

Add a battery system to this equation, and these same systems can obtain twice as much electricity (60-70%) for a household’s annual consumption.

“From now on, every new solar system that is installed in Germany increases the need for electricity storage solutions,” Rothacher said. “The cost of storage systems is forecast to drop in the coming years and this means that storage is not only becoming more necessary – it is becoming more attractive from a financial point of view as well.”

He added that, “several small-scale PV storage system manufacturers are working on bundling their battery systems in order to provide grid services (e.g. balancing power). One example is Econamic Grid (in Germany only).”

On A National Level

As for large-scale energy storage, the government introduced a 200 million euro funding program to support storage projects based on various technologies in 2011. Since then, many such large-scale storage projects have been realized and are being operated in order to gain experience and validate the technologies.

On sunny days, more than 1.4 million German PV systems are currently feeding surplus energy to the grid, but this number will increase.

Though the installation rate has decreased, no systems are expected to go offline until 2025, which is when the nation’s first solar panels reach retirement age. Every solar installation up that point will increase Germany’s overall output.

“The direct self-consumption potential for PV energy is around 74 TWh p.a. which would require an installed PV capacity of around 100 GWp,” Rothacher said.” Only with storage could the PV market grow further (taken together, all PV-suitable rooftops and facades in Germany could potentially provide an installed capacity of around 200 GWp).”

Solar houses in Vauban – meaduva, CC by SA 2.0

Solar houses in Vauban – meaduva, CC by SA 2.0

He stressed that Germany’s solar potential was demonstrated during the first two weeks of June.

“From now on, every new solar system that is installed in Germany increases the need for electricity storage solutions.”

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About the Author

is the editor of the ECOreport (www.theecoreport.com), a website dedicated to exploring how our lifestyle choices and technologies affect the West Coast of North America and writes for both Clean Techncia and PlanetSave. He is a research junkie who has written hundreds of articles since he was first published in 1982. Roy lives on Cortes Island, BC, Canada.



  • Johnny Le

    “The current reality is that solar contributed only 6% of the nation’s electricity during the first five months of 2014, but this will change.”

    I’m confused. How does it contribute only 6% in the first five months but 50.6% on one day in the 6th month? That’s a huge difference.

    • Bob_Wallace

      That’s a peak, the most extreme peak to date.

      Consider, the Sun is up and working a bit less than 25% of the day. That, alone, would cut “50.6%” to an average below 12%. Then calculate in the less sunny months.

      • JimBouton

        Bob, I always wondered, does the 6% number (or for that matter, the one hour peak value) include the electricity that is generated and kept to power your home through your own PV system? Or, does that number only include what is sent back to the grid?

        I would assume that ERCOT (in my state) would not really know how much electricity my system is producing, since their meter probably only records what I get from the grid and what I send back.

        Is that correct?

        • Bob_Wallace

          I don’t know if any states are tracking how much solar is used ‘on site’. The EIA attempts to estimate using utility reports but that’s likely a bit crude.

          The 6% number is from Germany. Germany might have a better handle on how much is consumed because they could work off the FiT numbers. But I don’t know if the 6%/50% number does or does not include consumed.

  • nakedChimp

    nice discussion going on here..
    And btw, my first LFP cell arrived last week: 100Ah 3.2V.
    Now just gotta get the BMS ready for it and then ordering more.. >:)

    • Vensonata

      Interesting. Lets hear more figures once you get it up and running. Price per kwhr life cycles cost of bms etc. thanks.

  • Phoenix

    Hey Everyone,

    Let’s not forget about CSP + Salt. This technology allows for base load 24/7/365. This is where our efforts need to be focused around. Combined with Enhanced Geothermal and we could have a serious powerplant. Imagine a 1 square mile facility running enhanged Geothermal on the bottom and CSP on the second floor above the Geothermal. Massive base load power supply there!

  • Ashtorak

    Have you guys heard of the hydraulic hydro storage idea of Prof. Heindl? Search for “TEDx Talk Hydraulic Hydro Storage” on youtube. It could take hydro storage to the next level, enabling seasonal storage. The idea isn’t listed in the site mentioned in the article above as it still only is an idea really, but one with huge potential. Also, it seems they are planning to realize a 50 m test version.

  • JamesWimberley

    Germany has a moderate capacity of pumped hydro storage (7.6 GW – link). Japan has 25 GW; the UK only 2.8 GW. Germany has a thin strip of true mountains along its southern border with Austria, which attract a lot of tourism, so potential there is limited. There are plenty of low hills though as far north as Hanover. I feel that Germany hasn’t been trying very hard on the technology.

    • Bob_Wallace

      There was some work underway in Germany to turn abandoned mines into pump-up storage. I’m not sure if that’s continuing or stalled.

      Watching how little effort seems to be going into pump-up I wonder if the general feeling is that storage is going to happen mostly with batteries.

      Batteries seem to have reached the point where they are competitive for short term gas peaker replacement. The next step would be multiple hour storage (moving night wind to mornings and midday solar to evenings).

      Pump-up has the advantage over batteries of being able to do “deep” storage – larger reservoirs for multiple day storage don’t greatly increase the overall system price. We might be 15 – 20 years away from needing that type of storage. We’re like to use fossil fuels as deep backup for at least the next decade.

      • Vensonata

        The round trip efficiency on pump up water or mine shaft pressurized air is not very good…maybe 60%. That is certainly better than nothing if you have extra. But battery can be 93% including inverter losses etc. nothing comes close for efficiency..that’s why Elon Musk is always dismissing hydrogen, for example. Seasonal storage though is a whole other ball game, then pump up is about the only possibility.

        • Bob_Wallace

          PuHS = “70% and 80%, with some claiming up to 87%”

          Wiki

          The other long term storage possibility is flow batteries. If the chemicals are cheap enough and large scale storage is cheap then that would be another way to get us past the days of limited sunshine and wind. Seasonal storage is just not something that we need to consider as far as I can tell.

          Some places such as Germany may need additional power in the winter, but that can be purchased from the ‘sunny south’ cheaper than storing power for months.

          • vensonata

            seasonal storage for heat in northern hemisphere is still a holy grail. See “Drakes Landing” community in Alberta. Amazing, housing community stores a winters heat in ground through summer solar hot water for 40 house without using a heat pump. All funded by Canadian government. Been working for 6 years… it should be famous!

          • MorinMoss

            Definitely sounds like something that would be beneficial in Germany.

          • Bob_Wallace

            I heard about that place before it was constructed and then it fell off the radar.

            I would think geothermal heat pumps would be a better solution. Do you know of any cost comparison?

          • vensonata

            It was a little on the expensive side because it was a demo. But now that it is proven it could be done for less. I am a big fan of heat pumps, especially the new cold climate air to air Mitsubishi but they take a fair bit of electricity in winter. The drake landing situation just pumps heat into the earth all summer and recovers it in winter. They have a nice web site that shows live monitoring of there system supplying 100%. I would say about 30 grand per house. About the same as ground source heat pump but much less electric demand.v

          • Jouni Valkonen

            I think that synthetic kerosene is the most relevant long term storage for the surplus production of renewables.

            Latitudes below 50° do not require seasonal storage and there is not living too many people above 50°. Those who live in the northern latitudes can survive with wind / coal / natural gas / biomass during the winter.

          • Bob_Wallace

            Some places above 50° also have good hydro. Northern Europe, for example.

            Toward the poles I would think that geothermal heat pumps for heating would be a good solution. That and super-insulation.

          • Jouni Valkonen

            Northern US and Canada has also good hydroelctric power reserves.

            I am also a fan of geothermal heat pumps. Drilling is getting cheaper quite rapidly. The capital costs are still high so the paypack period is still quite long. On long term it is quite cost competitive already here in Finland.

  • Vensonata

    A new day is dawning for off grid houses. Here is the old formula: pv panels supply 85%, generator supplies 15%, all stored in lead acid battery system, which should be able to provide 3 to 5 days storage, usually not going below 50% discharge. That was based on the prices of pv, gas, generators and batteries. Now because of vast reduction of pv price, here is a new formula. 99-100% supplied by pv. (Usually one needs to triple the solar array to get the last 15%!) eliminate gas, but keep a small cheap generator for worst case scenario. Reduce battery bank to 1-2 days storage at 80% discharge (since it rarely occurs it won’t damage battery life. Use agm instead of wet lead,because they accept the huge fast charge that the much larger pv array puts in. Also downsize the inverter/charger that formerly charged the batteries from the generator since it now needs only a small generator that runs only a few hours per year. Solar charge controllers need to be larger( but they are cheaper and highly efficient these days. You still have to be extremely frugal in December, the worst solar month but at least 8 months of the year you have substantial amounts of excess power, which can be use to charge electric vehicles, domestic hot water, and even a little space heating with heat pump technology.

    • Bob_Wallace

      “Now because of vast reduction of pv price, here is a new formula. 99-100% supplied by pv. (Usually one needs to triple the solar array to get the last 15%!)”

      Can you flesh that out a bit?

      I’ve been considering a major increase in my panel array but approaching the decision without numbers. What numbers would one use to determine the optimal array size? Would it be necessary to collect a winter’s detailed performance data? Or is 3x a seat of the pants estimate?

      My thinking is that having a lot more panels would mean that the hour or so the Sun might peek through could let me skip some generator use. And on the sunny days those extra panels could charge an EV (later when affordable longer range models are available).

      • Vensonata

        The tripling of pv is based on some excruciatingly detailed observations of our 3.6 kilowatt hr pv panel. December is our worst month at latitude 51. It is cloudy as well. We average only 50 hours of bright sun in the entire month. We get about 120 kwh in that month and we use about 300. So tripling gets about 360 kwh, there will be a few stretches of 3 days with very little sun but a 10 kwh array can bring in a days worth of power if the sun comes out for 1 hour. Or over a 6 hour cloudy day you get a respectable amount. We will still scrape bottom once or twice but basically one can be very, very close to 100% solar. All you do is look up your hours of bright sunshine for December multiply by .75 then calculate your total average daily needs in that month. Most places in the U.S will do better than our pitiful 50 hours. Only Germany is worse. If you have a one kwh array its a good bet that adding another 2 kwh array will get you where you want to go. Best of luck.

        • Bob_Wallace

          I don’t have any collected data, but I do have the observation that on “normal” cloudy days I get enough out of my panels to run during daylight hours without tapping into battery storage.

          My present routine is to go out about 5pm and start the gen in order to store up enough to get me through until ~10am the next morning.

          My meter reliably shows that I’m staying about even in terms of +/- Ah from morning until late afternoon. But that doesn’t put anything away for evening/nighttime.

          I’ve been thinking that if I tripled my array size I could probably make it through most nights following (non-stormy) cloudy days.

          Plus I want to get my array off the ground and on my roof in order to free up the space the panels now take. I’m past the point (age and knee-wise) where I’m going to move the panels to my steep pitched roof so as long as I’m paying someone to come out and do my 1.2 kW I might as well bump up the number of panels. Travel and scaffold setup time is going to be the same either way.

          • Vensonata

            Sounds like you can pretty well retire that generator. As long as that roof orientation is within 15 degrees of due south and at least a 6/12 pitch then that roof will work just fine. If it is standing metal seam then you can save money on racking by using s-5 clips.

          • Bob_Wallace

            15/12 pitch – 51.5 degrees. That’s just short of my optimal winter setting of 55 degrees. (Latitude 40 + 15)

            Pointing due solar south.

            I currently do an ~ October 13 to February 27 adjustment to as high as my racks will go (about 50 degrees) and drop down to 40 degrees for the rest of the year. I don’t bother doing a summer drop as I’ve always got far more power than I can use. (Well, there were a couple of days when I was sanding new hardwood floors….)

            And standing seam metal roof. Thanks for the S-5 clip lead. Didn’t know anything like that existed.

          • vensonata

            Yes, the clips don’t require cross bars. Much cheaper and just as good. Your winter setting is all that matters, sounds perfect. It is a nice problem to have to figure out what to do with all the excess juice 8 months a year.

          • Offgridmanpolktn

            Bob,
            Since you are talking about expanding your system have you considered the possibility of a small wind turbine?
            Part of my balancing act includes a 2 Kw Whisper that is designed for slow speed so starts generating at 6 mph and peaks at 12. By the maps this usually wouldn’t be an area where sufficient wind would be considered to be available but fortunately building the house on top of a hill with views to the west and north unobstructed for miles it does work.
            This time of year it doesn’t produce much maybe five percent of our monthly usage, but come the end of September or October when the fronts start coming across the country there are plenty of days when it puts out 100% of our daily average usage. Which is when the days are getting shorter and cloudy. So a perfect match to my mind. Eight years ago it was just a little over three grand including monopole, cabling, charge controller and pouring the foundations and it is light weight enough that I can take it up and down by myself with my mini tractor for maintenance which is only every other year. With the base about 150 feet behind the house and up on top of a hundred foot tower I don’t even hear it running unless we get steady winds over 15-20 mph and I am outside if that is a concern for you.
            Perhaps panels and installation have gotten cheap enough now that your expansion could be the better idea but wanted to throw this out for you.

          • Bob_Wallace

            I’ve run through the turbine numbers a few times and they just haven’t penciled out for me.

            I’m surrounded by 80′ Doug firs so I’d need a fairly high tower. And I’m past the point of installing and doing maintenance myself. (Older age sucks.) That means having to hire someone from town to deal with all that stuff.

            I’ll do the numbers again, but the big attraction for a large array is ‘install and ignore’. Staying with a generator is likely the least expensive, but I’m willing to pay something extra in order to get away from the hassle (and carbon) of fuel.

            If I could install for ~$3k and locate it where I could raise/lower with my PU then a turbine might be a good option. However I do like the idea that a crew would show up here some morning and I’d have a nice big array on my roof by evening.

            Then the issue becomes cleaning. Minor, hosing down should be enough.
            And snow removal. I’m thinking about installing a PVC pipe along the top of the array, drill some small holes in it, and feed up some (hot?) water to get the melt started. My experience so far is if you get a small part of a panel exposed then it quickly heats and the snow/ice melts and slides.

            Now, with ground mounted panels, I often have to shovel snow from below the panels so that there’s a place to slide.

            Except for this last very, very strange winter. I live where snow is common in the winter. About one out of every three years I get snowed in for a month or more. This last year we got a very early snow well before Thanksgiving. Then zero snow until after Valentines Day when we got two small snows.

          • Offgridmanpolktn

            With trees that big the turbine option may not work for you, here in the Southeast it has been no problem getting high enough over the southern/yellow Pines (30-40′) to have enough clearance. And as I said am quite fortunate with my location. When the hardwoods come back in 25-50 years it may not work out as well for my boys but by then efficiencies should be high enough on panels that they can get by on straight solar.
            So I was just checking to make sure that you had considered that as a possibility.
            Another project that has been daydreamed about is to dam off the ravine on our property and fill it during the summer off from our artesian spring and use that for pumped storage during the winter. Right now the slow pump fills our water tank one day a week and for the rest just goes to watering the garden and animals with the overflow making a creek through the ravine. Another option for this is being able to farm our own catfish or trout but as you mentioned age is slowing me down a little too, so will have to wait a couple years until the boys are old enough to contribute on the labor.
            Maybe I am being greedy but the thought of that 8 gallons per minute flowing off of our property, not even counting the rainfall, without getting some use out of it just goes against my Scottish soul.

        • juxx0r

          Are your panels at 65 degrees? You really need to optimise for the worst month, especially if you’re going to over do it by 300%.

          • Vensonata

            Yes we have tilt able racks so we can optimize. We can even manually track by turning a couple times a day. But we have learned over the years that the tilt angle is not that important as long as you are within 20 degrees of your latitude the difference will only be about 5%. There are nice charts for this. Only when you get up around 60degrees latitude do you really néed to optimize because the days are so short in winter.

  • No way

    This will be the most important question going forward. Getting low levels of renewables like they have today is easy. It will be much harder getting most electricity from renewables and even more so to get all.
    I wonder if they have any real plan for this. Or if they count on burning lots of coal forever.

    • Bob_Wallace

      Germany plans on eliminating all fossil fuels by 2050.

      The anti-renewable and pro-nuclear factions are making a lot of to-do about Germany and coal but the facts don’t support their claims.

      “As a reaction to the nuclear phaseout, Germany has thus started building zero coal plants but stepped away from six.”

      http://energytransition.de/2013/04/germany-builds-minus-six-coal-plants-after-nuclear-phaseout/

      • No way

        Maybe not forever. But the plan is still to be dependant on coal for another few decades.
        And for more renewables to work properly they will need a lot of storage. There are lots of big question to answer about it. Not everyone can do as Denmark and use Norway and Sweden for backup.

        • Bob_Wallace

          Germany is using coal because NG is a worse option for them.

          There’s no reasonable way to get fossil fuels off our grids overnight. A 35 year plan looks doable to Germany right now. 35 years is a very long time when it comes to technological advances. I’ll bet they reach their goal sooner.

        • PLehmo

          As soon as there is a world grid then solar will aways be on (somewhere)

    • Bob_Wallace

      “Getting low levels of renewables like they have today is easy. It will be much harder getting most electricity from renewables and even more so to get all.”

      Will it?

      Wind and solar will likely continue to drop in price. It will get easier, financially, to add more wind/solar to the grid.

      Existing thermal plants will ‘wear out’ over the next 36 years. They will need to be replaced with something. Wind/solar with pump-up storage is cheaper than new coal or nuclear. And will meet less resistance than would new coal/nuclear.

      And that’s making no assumption that a cheaper large scale storage technology such as Ambri’s liquid metal batteries doesn’t appear.

      Add to that the development of an All-Europe along with some North Africa and possibly western Asia grid. A continent+ wide grid is going to smooth out a lot of variability and reduce the amount of storage needed.

      • No way

        I hope you are right. Well… right about everything except them having fossil fuel plants for another 36 years. Hopefully all of them will be closed by then.

        • Bob_Wallace

          I’m optimistic. 35 years is a long time. Look back 35 years to ~1980. Cars with carburetors and dial phones.

          Since then we’ve gotten personal computers, cell phones, cheap wind and affordable solar. Most people are aware of the climate change issue. We’re spending very serious money looking for better, cheaper clean energy and efficiency.

          Over the next 10 – 15 years many of the climate change deniers will die. Or at least become so old that they drop out of the discussion. The voters that enter on the bottom end will have grown up in a world in which climate change was an ongoing discussion.

          We’ll have 10 – 15 more years of climate change experience. Unless climate science is wrong we will find it very easy to measure rising sea levels, season shifts and will have seen the Arctic Ocean free of sea ice.

          We’ll, I think, speed things up year-to year and likely accelerate that speed up as climate change becomes more obvious, technology improves, and the deniers fade away.

          I suspect that within the next 10 years the world will essentially stop building coal plants. If for other reason, because they are priced out of the market. That we’ll have affordable, long range EVs and the market will be rapidly shifting away from ICEVs. And that we’ll have figured out a storage system better/as cheap as pump-up hydro.

          A decade of building on top of cheap wind/solar, affordable storage and affordable EV should greatly clean things up 20 years from now. I’m not sure I’ll be around, but if I am I won’t be surprised by Germany’s closing of coal plants by 2040.

          • vensonata

            Yes, i think you’ve got something there…the acceleration of change. Radical technical change has been going on since the 19th century but the rate is increasing with the web, and convergence of technologies. We may all be surprised in a positive way.

          • Ross

            That’s pretty much how the future is likely to play out.

          • Offgridmanpolktn

            You are right in that the change is happening, but I think we already have young people of voting age that have seen the affects of climate change beginning and want to do something about it. Check out the enthusiasm of the graduating class of UC Irvine listening to Obama in the video a couple of blogs up from this one.

          • Bob_Wallace

            Clearly change is happening. But unfortunately young votes are much less likely to show up at the polls than are older voters. Us old farts have less busy schedules and going to vote can be the exciting outing of the week.

            I grew up in a segregated country, where coal was king and nuclear was going to bring us all the cheap electricity we could want, as well as a lot of other stuff that just isn’t today’s realities. Some of those my and age and older have never managed to shake the reality of their youth.

            We vote in higher numbers, but over the next decade nature will see that a lot of us won’t continue to vote.

  • vensonata

    Yes, with a grid price of 26 cents/kwh in Germany then off grid is cheaper. I’d love to know the price of those battery storage systems. However, since we seem to be about 5 years behind Germany I imagine those nice clean lithium units will be here and affordable by the year 2020.

    • Offgridmanpolktn

      You don’t need to wait that long, through a battery distribution company two years ago I got a used set designed for cell tower backup rated at 16 Kwh for 800$.
      Also out of curiosity hearing that used battery packs from the Chevy Volt were becoming available had the manager at the local NAPA do a search. 8-1200$ for battery packs rated within 85-95%of original peak capacity with a five year replacement warranty.
      Have been totally off grid myself for about 8 years and have found that batteries are a lot cheaper if they don’t have the solar qualification in the name. Even my original set of ultra deep cycle marine batteries were 40% of the price of the exact same thing called solar batteries.

      • Bob_Wallace

        Marine deep cells have much thinner plates than ‘golf cart’ deep cycle batteries. And the new Trojan RE series has even thicker plates.

        (I suspect lead acid is not the future. But it’s not yet the past, either. Need to compare new:new when it comes to price.)

        • SirSparks

          My Trojan RE’s won’t compete with those used cell tower prices. I paid 25% less than list or $100 per kilowatt hour however in order to preserve an 8 year life cycle I can only discharge to 1/2 a kilowatt hour per cycle (1 day on solar).

          • Offgridmanpolktn

            With it being used only got a five year warranty myself, but when talking to the original manufacturer since they will never go below fifty percent discharge he said he wouldn’t be surprised if I get twenty or more years out of them. With the efficiency improvements over the years even after being snowed in for 3 days this past winter we didn’t go under 67%. So hopefully these batteries might even outlast me.
            It has saved in gas expenses too, because the generator only had to be run once in December and again in January to achieve peak charge, so about 8$ total. All the other months the panels have done it by shutting down everything but the fridge and freezer when we were out for the day.

        • Offgridmanpolktn

          I was aware of the difference at that time 8 years ago but it was a matter of financing. Paying five dollars per watt for panels back then had to economize on the batteries, and getting a bulk price of 32$ a piece for 12 of them gave me something I could live with. Actually after six years they were still holding up pretty good with 90-95% of original capacity left but I was getting tired of the maintenance every two weeks and wanted to go bigger on my storage capacity. So a jump from 1.6 Kwh to 16 Kwh along with maintenance dropping to once a month of just making sure of a peak charge and no water (electrolyte) to mess with was worth the new investment.
          Lucked out in another way because the price of lead was so high at the scrap yard then that those 32$ batteries returned 12$ each.
          My real point is though that storage on the home scale is and has been possible if you go out and do some shopping around and avoid the solar label.
          Even those golf cart batteries you mentioned are available at a battery supply house for 60% of the price they get for them through a solar marketer because they don’t have the solar label on them.

      • vensonata

        That’s fascinating, these battery packs from the volt though seem to last a good long time…so it will be another few years before the used packs are available to us off-grid communities.

    • Ashtorak

      Can I post links here? On this site you can get info about the sotrage systems available in Germany:

      http://www.solaranlagen-portal.com/photovoltaik/stromspeicher/preise

      It seems that they don’t have an English version, but you could try google translator. In any case, prices for these systems currently still vary a lot. The site mentions a range from 20 to 60 €-cents/kWh (Pb and Li-systems).

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