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The future of solar power

  1. May 18, 2017 #41
    Im hoping this is a fairly significant year for batt storage with the Tesla batt factory nearing completion, Daimler getting into the market, Panasonic getting new competition on their heels.

    Reading about energy storage and ignoring portability it seems to me that electrochemical may not be the best solution. The mechanical simplicity of gravitational potential energy and solar power makes me drool. lol

    Apparently even flywheels are used to "store" energy. kept in vacuums supported with magnetic bearings, made of carbon fiber and rotating at up 60k rpm! Oh that's a cool one too! So cool when star trek complexity and flinstone simplicity converge.
  2. May 18, 2017 #42
    So, using these numbers, I would spend $23,000 on these batteries; they would last 10 years; and in those 10 years I'd use 10 * 365 * 30 = 109,500 kw-hr.

    Then the battery cost is $23000/109500 = $0.21 per kwhr. That's more than I pay for my grid power (even where I live, and the power cost is high here).

    Or, say you took a loan for the battery; 10 years at 4%, the monthly payment is ~$235, and that's just for the battery. That's more than my monthly power bill.

    So, there's plenty of room for improvement in the numbers before I can see widespread adoption of solar.
  3. May 18, 2017 #43
    Yeah, exactly why I don't have a system set up for back-up power at my house.
    That, and lead batteries take up a lot of space, take a lot of babysitting, and put off deadly gas...
  4. May 18, 2017 #44
    I lived in south Florida for awhile. The house I rented in had solar hot water heater on the roof. Now that made sense! On a sunny afternoon the relief valve lifted to vent steam from the storage tank. No electric conversion, just sunshine to hot water. Takes the load off the electric or gas hot water heater. Storage takes care of itself as the tank stays hot overnite.
  5. May 18, 2017 #45
    Re: storing electrical energy, it seems about ten years ago everyone was talking about supercapacitors. I haven't heard anything about them in a long time.
  6. May 18, 2017 #46
    I would not worry. Market forces would "magically" do their thing. Whatever kind of cell would be optimal wrt cost/efficiency, market will eventually mass-produce exactly that one :D

    Well, in fact all other kinds of plants, except maybe wind, have WAY MORE other equipment. Maze of piping for water, air, oil (usually more than one kind: say, "instrument air" and "pneumatic air" are two different systems). Valves everywhere. Gaskets. Pumps, pumps. I remember when I was reading about a 6 MW pump in a nuclear plant and was amused to discover that its sealing system required high-pressure air which... required another small pump just for that purpose! :)

    Solar is winning hands down here. It needs only a handful of kinds of equipment, and it is all electric. No oils, water, gases, high pressures...

    Yes, solar needs transformers. This is not at all different form any other plant.
  7. May 18, 2017 #47
    Tesla's Powerwall is not optimal economically (it's too costly, and I have doubts about longevity). Tesla is just repackaging and selling excess production originally designed for cars. They are, as a business, certainly justified in doing so, but we as consumers need storage tailored for non-mobile, large scale storage.
  8. May 18, 2017 #48
    Aside from cost, or scalability, what disadvantages would a battery designed for mobile use present in a non-mobile application?
  9. May 18, 2017 #49
    Cost is the key factor. A cell which is 4 times heavier, but twice as cheap as car battery, (and all other parameters are same), would win hands down for utility storage.

    Car battery which needs replacement in 5-10 years is okayish for cars. Utilities would want to install them once and run them for as long as possible.

    Car battery needs to be able to provide spiky output. Utility storage does not need that. This means that batteries which have many good params, but require only slow discharge can be suitable for utility but useless for cars.
  10. May 18, 2017 #50


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    ... a gas or coal or nuclear or hydro plant. Intermittent power may throttle these back a bit, but does not replace any of them, and thus only adds to the total equipment installed.
  11. May 18, 2017 #51
    Thank you for the clear reply.
  12. May 18, 2017 #52
    ?? The cells are panasonic, at least the first gen powerwall was. They (tesla) do make and have installed "utility" sized power storage and market it as the powerpak.

    I'm missing the point of "made for mobility" So because the cell has a much better energy density it's made for mobility? imo important factors for a battery is energy density, voltage curve, resistance, c rating and ease of use

    As far as non-mobile installations and cost what beats flow batts? The energy department is supporting/funding both flow batts and Li for energy storage.

    Tesla is making batts already?? news to me. I thought that was why they (Tesla) partnered with Panasonic.
    Last edited: May 18, 2017
  13. May 18, 2017 #53
  14. May 18, 2017 #54
  15. May 18, 2017 #55
    The true value of storage for anyone with PV is a lot higher than the average kWh price. As the cost of the PV drops and users have greater supply in excess of usage that value will become more apparent.

    I realise there are large differences in how electricity is sold dependent on where you live. Here we pay a Service Availability Charge on top of usage, so a close to self sufficient PV and battery fitted home effectively pays much more per kWh than a home totally reliant on the grid. Many are on time of use tariffs, where the evening usage can be double the daytime price - for those it can be financially sensible right now. Note that predictions here are for significant retail electricity price rises, as much as 30% this year, and if that is mostly SAC rises it will shift the balance yet further in favour of battery installations. Most batteries will be still working after 10 years, albeit with reduced capacity that, for a lot of households, will still be adequate. Expect both working life and price to continue to drop as the battery industry develops and expands.

    We are moving beyond renewables being used because of subsidies and other policy support into circumstances where market forces sustain it. Those market forces, combined with shortsighted responses like offering very low prices for PV sold back to the grid or forging ahead with Time of Use metering (both on the face of it, expected to reduce attractiveness of PV - batteries not much figuring into those decisions) continue to strengthen rather than weaken demand for PV and storage.

    The service the grid provides to PV and battery using customers is in provision of backup supply, with ongoing improvements decreasing the frequency and depth of dependence on that backup. Equitable arrangements are needed for accommodating that and make best use of the excess such installations tend to produce; higher prices during weather affected periods where existing fossil fuel plant has to ramp up is reasonable, but again will make improved storage options more attractive. If equitable arrangements are not introduced going off the grid will begin looking increasingly attractive; personally our household is very close to the point where additional batteris and the occaisional use of a generator would be cheaper than paying for an ongoing grid connection. We are borderline for gaining any financial advantage from our PV and batteries installation, but if that price rise does go ahead it will no longer be borderline.
    Last edited: May 18, 2017
  16. May 18, 2017 #56
    Solar panels on residential rooftops is the worst way to utilize solar panels. It ought to be frowned upon by anyone who is pro-solar.

    As you mentioned, a residential install can have shading issues. And few of them will have rooftops in the optimal direction/slope, requiring additional resources for the racks, or just limiting how many panels you can place there.

    Plus, every single installation has to be reviewed, permitted, inspected and have it's own transfer switch. And workers will go to a new site every few days, deal with different roof slopes, gutters, dogs, fences, and on and on. Solar is responsible for more deaths/injuries than nuclear, maybe even coal (on a MW-hr generated basis) - I can dig up the link if needed, from US BLS, IIRC.

    Much better to have an industrial/commercial scale installation. A big-box store, warehouse, and/or large public building (school, library, etc). There's is no shortage of large, flat rooftops in populated areas where the grid is available and energy is needed. A crew goes to one site for an extended period of time, instead of a hundred or thousand individual sites. They work on one flat roof - much safer. Easy to get to for maintenance also. Economy of scale in so many ways.

    I'd consider buying into 'shares' of solar farm like that, long before I would put panels on my roof. I wouldn't need to worry about getting my investment back if I moved. I could buy a share of panels in a locality that had the best combination of available sun, high kWh prices, and the dirtiest grid. That would put those panels to the best use, and provide the best financial and environmental ROI. Everything is so far in favor of solar 'farms', that any talk of residential solar is just silly and counterproductive (exception for the rare off-grid requirement).
  17. May 18, 2017 #57
    I'm not so convinced that putting all of the eggs in one basket is the way to go.

    Every four or five years we have a storm that knocks out the power to tens of thousands of people (Michigan, USA), and lasts for as long as several weeks, before everyone is back up and running. The usual reason for the failure is the infrastructure, namely poles and wires that get knocked out by either wind, snow, or ice, or a combination thereof.

    I definitely am sick of extended blackouts. Aside from the regional occurrences, I have had, on average, a local blackout lasting more than 48 hours, about every 30 months over the past 15 years where I live. Now, a simple battery back-up would have taken care of most of those, but installing a system of batteries to last more than 3 days, is a pretty expensive proposition, and it doesn't take long to start justifying some solar panels, instead of a few more batteries, especially when you consider the potential for the regional blackouts of extended duration.

    If I had the coin, I'd be talking about my solar system, not discussing the merits of having one, wistfully.

    From a purely "economy of scale" stand point, your argument is clearly bullet-proof. On a practical level, there are at least some people who would be better served if the power generation was not super-centralized.

    I live on a "spur", not a grid, when you look at how power gets to me. A few years ago, some automobile driver hit a pole 2 miles from me , at 2 in the morning. Everyone on a line between that pole and the stop sign 5 houses past my house, went without power for almost two days, except folks with the means to generate their own, because the power company has not seen fit to cross-connect our end to the grid a few blocks away from me, where there is another "spur".

    I guess what I am saying is that there is no "one size fits all" solution for Solar infrastructure. In my case, I'd rather be self-dependent, than rely on some bean counters to decide if building the infrastructure properly is "cost effective".

    Also, I would hate to think of what would happen if a big-box store that was providing the real estate on their roof caught fire, and the solar farm was lost. We'd be talking about a lot of people with no lights, for an extended period. If it took an extended period of time to build in the first place, imagine how long it will take to clean up the site, and then remove the damaged portions of the farm, or all of the farm, and rebuild it... the red tape alone would be a nightmare.

    ...and that's an awfully large basket of eggs, I think.
  18. May 18, 2017 #58


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    Coal is worse.
    US coal is ~25 more deadly than rooftop solar, which is 4000 times (sic!) worse than US nuclear power. All per kWh of course.
    If we take the global average and include all accidents, coal kills 250 times more people, while nuclear power has 5 times lower death rates than rooftop solar.
  19. May 18, 2017 #59


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    That's definitely a problem, but unfortunately, residential rooftop solar won't solve it; The vast majority of residential rooftop solar installations are not allowed to operate during a blackout.
  20. May 18, 2017 #60
    There are other ways to get residential backup power, they might (probably?) be more cost effective than solar and batteries every few years (natural gas/propane generator). But that's an individual situation for you to make the call on. I was really talking more about regular day-day power generation, not back up power.

    Thanks! :smile:

    Nah. There are two large installations near us, on large school buildings, LOTS of roof space covered with panels. There are 1,760 panels on the roof, yet it has a peak capacity of ~ 440 KW. That's KW, not MW. A typical coal plant in Illinois has a capacity of ~ 800 MW. So losing one building like that would be like losing 1/2000th the capacity of a coal plant (and only when the sun is shining).

    The eggs would be in thousands of baskets.
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