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BMW Unveils the Solar Charging Carport of the Future 165

Posted by samzenpus
from the park-and-power dept.
cartechboy (2660665) writes "The carport hasn't changed much over the years. Made out of wood, aluminum or steel, they are simple structures meant to cover your vehicle from the elements. BMW has just revealed a concept carport that takes these structures into the future. Made out of bamboo and carbon fiber, this concept carport features solar panels that harvest the sun's energy and use it to charge your BMW i-vehicle. "With the solar carport concept we opted for a holistic approach: not only is the vehicle itself sustainable, but so is its energy supply," explained Tom Allemann of BMW Designworks USA. "This is therefore an entirely new generation of carports that allows energy to be produced in a simple and transparent way. It renders the overarching theme of lightweight design both visible and palpable." The entire thing is quite beautiful, and could be the way to make not only charging your electric car sustainable, but also building your carport."
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BMW Unveils the Solar Charging Carport of the Future

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  • by SpaghettiPattern (609814) on Friday May 09, 2014 @03:27AM (#46956953)
    How long would it take to charge your car with a 15ft x 20ft panel? Hours? Days? Weeks?

    (Is it just me or does BMW make an incredible effort at failing to design pretty cars?)
    • by Calinous (985536)

      Assuming a slanted roof (oriented to south), you'd get at most 3500W from the device. In an 8-hour day, with some 60% total efficiency, you'd get some 17 kWh. That would be enough for the i3 I think.
            This thing would be advantageous if it would keep the car in the shade during summer, and clear of snow in the winter. A garage would be better, though. And maybe setting the solar panels on the house is either too expensive, impossible, ...

      • by stiggle (649614)

        As a carport is usually classed as a temporary structure it can avoid certain planning regulations which a garage, or mounting the panels on the house roof would come under.

        • Carports are usually supported and anchored in concrete, they usually require a building permit just like a garage. Mounting solar panels on an existing structure does not.

          The problem I see here is you will need some type of electrical storage because most people drive their cars to work, etc... during daylight hours when it be charging.

          • by Richy_T (111409)

            Depends completely on jurisdiction. Best not to generalize.

            • True... with the type weather we get a carport that's not anchored {or just cheaply made} would be torn to shreds each spring. I would love to be able to have something like this but we have already had hail twice this year and high winds are the norm for tornado alley. I have thought that a wind turbine would be nice but I don't think the city ordinances would allow for that.

      • Re:How long? (Score:5, Insightful)

        by CrimsonAvenger (580665) on Friday May 09, 2014 @08:12AM (#46957891)

        This thing would be advantageous if it would keep the car in the shade during summer, and clear of snow in the winter. A garage would be better, though.

        This thing would only be advantageous if your electric car spent its daylight hours at your house.

        In other words, largely unused. Most of us drive to work in the daytime, drive home in the evening, and our car stays home (with us) overnight. Not as much sunlight as you might expect at night....

        • You can sell the electricity back to the grid to offset the charging cost. I know it's a crappy deal because the electricity you sell back is somehow worth much less than the electricity you use, but it can help offset some of the electrical costs.

          • by jklovanc (1603149)

            I know it's a crappy deal because the electricity you sell back is somehow worth much less than the electricity you use,

            It is worth less because someone has to pay for the infrastructure to transmit that electricity around and the backup capacity that would kick in on cloudy days. When you buy electricity you are not just purchasing electron but the all the infrastructure to support making sure you always get what you want. Energy produces sell at a wholesale price which is much lower than the retail price. People who sell to the grid at a lower price than they buy from are just being treated like any other electricity prod

            • by AmiMoJo (196126) *

              It's worth more because it peaks around peak consumption times when electricity is most expensive. While you may pay a flat rate all day (or at most a day/night rate) the electricity company's costs vary from minute to minute with load.

              Anyway, the electricity grid is public infrastructure. In my country we built it ourselves (tax money) for our own benefit, but then stupidly sold it off. In Germany they are buying it back to make it work for the end users again, instead of corporate profit.

              • by jklovanc (1603149)

                It's worth more because it peaks around peak consumption times when electricity is most expensive.

                Yes but it never comes up to the retail price for electricity. Also the distribution companies know that so they average out the price during the day. Energy companies buy at a variable rate. Do you think consumers should too?

                Anyway, the electricity grid is public infrastructure.

                So what? No matter who owns it it still needs to be maintained and upgraded as more people use it. If you buy at the same price as you sell there is no money for that.

        • by dj245 (732906)

          This thing would be advantageous if it would keep the car in the shade during summer, and clear of snow in the winter. A garage would be better, though.

          This thing would only be advantageous if your electric car spent its daylight hours at your house.

          In other words, largely unused. Most of us drive to work in the daytime, drive home in the evening, and our car stays home (with us) overnight. Not as much sunlight as you might expect at night....

          Another poster came up with a figure of 30kW-hr per day input to the car (considering efficiency and hours of sun, etc). In my area, that's worth about $3.6 per day. I have 52 weekends off per year, plus 11 company holidays, and 15 days vacation. If my car sits at home for 1/2 of those days, that's 65 days of charging or $234. I would consider a payback period of 5 years to be a reasonable investment for car-related equipment, so for me, the maximum the device could cost is $1170 in order to be a worthw

          • by mythosaz (572040)

            It's less than that. The BMW i3 has a 22 kWh battery, and only under the most deal circumstances are you ever going to charge the whole battery every day, which will at most be about $2/day.

            More realistically, my Leaf, which we drive more than the national average - and which has a battery size and MPGe almost identical to the current BMW i3 - uses about $25/mo in electricity, which you could presumably charge using this system if things went well.

            [Or, you could offset residential electricity to the same $

        • by timeOday (582209)

          This thing would only be advantageous if your electric car spent its daylight hours at your house.

          No, where it would be advantageous is in parking lots (ideally my employer's parking lot!) All the wasted energy falling on parking lots every day is not only wasted, it is harmful, because it makes urban heat islands - the city is hotter than the climate it's in.

          That said, it's foolish to devote the panels on a parking garage to the car that might or might not be there. Feed it into the grid and use i

      • by unrtst (777550)

        ... A garage would be better, though...

        That was my first thought. To me, "carport" is synonymous with "I didn't have enough money for a proper garage". There's nothing wrong with carports but, as soon as you add on the fancy solar panels and all that stuff, this thing is going to be more expensive than a nice garage that includes additional storage, security, protection from the elements, etc etc etc.

        Second thought was, how is this something to "unveil"? it's just a typical solar panel install... *on*a*carport*! I'd be amazed if this hasn't bee

        • by idontgno (624372)

          Second thought was, how is this something to "unveil"? it's just a typical solar panel install... *on*a*carport*!

          Careful, that's going to be the next wave of stupid patents, right after "on a computer" and "on a mobile device."

      • by Dcnjoe60 (682885)

        Assuming a slanted roof (oriented to south), you'd get at most 3500W from the device. In an 8-hour day, with some 60% total efficiency, you'd get some 17 kWh. That would be enough for the i3 I think.

        This thing would be advantageous if it would keep the car in the shade during summer, and clear of snow in the winter. A garage would be better, though. And maybe setting the solar panels on the house is either too expensive, impossible, ...

        Of course if you are going to leave your car in the carport all day, it kind of defeats the purpose of having it. Now if this would charge a battery pack during the day that would then be used to either swap in the car (probably not) or charge the car overnight, that might be cost effective. However, because of inefficiencies, it probably wouldn't provide a full charge but would supplement the regular powergrid.

      • Re: (Score:2, Insightful)

        by Charliemopps (1157495)

        That's assuming it's always sunny and that anyone that owned a BMW would be ok with having a carport. You need to remember, people are still buying electric cars because they're currently fashionable. Carports are not fashionable and I can't see them becoming so anytime soon.

        I do like that they're using Bamboo however. People really need to start utilizing Bamboo in the west. It's an amazing material and more "green" than most of the fads we like to pretend are green over here.

        • That's assuming it's always sunny and that anyone that owned a BMW would be ok with having a carport.

          And that they live somewhere than can have a carport. (I can't because of how my house sits on the lot.) And that they live in a place with ideal solar conditions. (Even if I didn't live in the Pacific Northwet... my driveway is shaded by the house until late morning, and by the trees across the street from mid-afternoon on.)

      • by Vihai (668734)
        However, given the cos alpha rule, 15% realistic efficiency, 3 hours equivalent daily radiation, it takes a week minimum (on a cold shiny day) with such non-small plant.
    • by Firethorn (177587)

      It looks to be using 24 panels in a 6x4 configuration.

      'Standard' 250W panels are 40"x65", giving my 20'x22', so 'close enough', especially if you slant it a bit.

      Assuming ideal, that's 6kw. More realistically 3kw in most areas, about 43kwh per day. About 129 miles of electricity at 3 miles per kwh.

      • Math check (Score:5, Informative)

        by Firethorn (177587) on Friday May 09, 2014 @04:09AM (#46957115) Homepage Journal

        Double checked my math. More like 22 kwh, or 66 miles worth of electricity a day.

        • 22kWh/day really is your best case scenario.

          http://www.nrel.gov/gis/images... [nrel.gov]
          6.8kWh/(m.day) in Arizona on a tilted plane gives you about 2500kWh/(m.y)
          With a performance ratio of 90% for your PV installation, you can get 2250kWh/(kWp.y) of electricity.
          With 3.6kWp (see http://www.solarwatt.de/en/pro... [solarwatt.de]), you get 8100kWh/y, which is about 22kWh/day.

          But this is only in the sunniest place in the US, with a tilted roof and a very good performance ratio.
          You'll get close to 10kWh in Europe and many other places in

          • by Kokuyo (549451)

            According to a technical sheet I just googled, this BMW has a 18.8 kWh battery... so those 10 kWh are more than half a "tank".

            Considering that solar panels aren't high maintenance (I believe?), one could argue that it's a step in a good direction.

            • by mark-t (151149)

              Which means that it would take two sunny days in a row, with very little driving in between to "fill up". In practice it would be even more, since this is the amount of energy that you'd get assuming that the solar panels were 100% efficient, so you can probably double that time or worse.

              Compare this to spending 5 minutes at a gas station to fill up an empty tank with gasoline.

            • by mythosaz (572040)

              I show the i3 with a 22 kWh battery - roughly the same as the Leaf.

          • 22kWh/day really is your best case scenario.

            6.8kWh/(m.day) in Arizona on a tilted plane gives you about 2500kWh/(m.y) With a performance ratio of 90% for your PV installation, you can get 2250kWh/(kWp.y) of electricity.

            Your answer is about in the right ballpark, but the method is in error. The chart which shows up to 6.8kWh/m2/day (for SE US) reflects actual solar energy, not electrical. Solar cell conversion efficiency is about 20%, resulting in about 1.36 kWh electric/m2/day. Considering the 6.8 is really that max possible, and there are electrical losses through the inverter, you could expect about 1 kwh-e/m2 If the panel area is 440f2=40m2, you could get as much as 40 Kwh-e/day. That is a generously high number. I

            • Re:Math check (Score:4, Informative)

              by BlackPignouf (1017012) on Friday May 09, 2014 @09:35AM (#46958589)

              My method is just fine, thank you very much. I happen to work at a german research center on solar energy.

              The performance ratio takes all losses in consideration (cable, MPP, inverter, shadowing,...) and isn't dependent on either the area (which is 27m2 for this carport, BTW) or the efficiency (about 15% for this carport).

              With the performance ratio, you can convert solar irradiance (in kWh/m2.year) directly into specific yield (in kWh/kWp.year).
              This carport has 3.6kWp capacity, and seems to be developed by Solarwatt.

              • With the performance ratio, you can convert solar irradiance (in kWh/m2.year) directly into specific yield (in kWh/kWp.year).

                You state performance ratio of 90%. However, kWh/m2 electrical output = more like 0.15 kWh/m2 Solar irradiance.

                I don't see how you included the 0.20 conversion solar to electrical efficiency in your performance ration. 90% only accounts for losses from electrical output of panel to load, plus shadowing and other physical installation factors as you stated.

                In other words, you do not get 90% of 6.8 kwh/m2/day in electrical output. You get more like 15%.

                • Re:Math check (Score:4, Informative)

                  by BlackPignouf (1017012) on Friday May 09, 2014 @11:10AM (#46959491)

                  Take a look at the units for solar irradiance and specific yield.
                  They are *not* the same.
                  The 20% cell efficiency (or anything between 0.05 and 0.44) is included in the conversion between m2 and kWp : e.g. you need 5m2 of PV modules at 20% for 1kWp.
                  Performance ratio and cell efficiency are different notions. Performance ratio can theoretically be higher than 100%.
                  http://www.photon.info/photon_... [photon.info]

                  • I agree with that, so lets just clarify; You stated;

                    6.8kWh/(m.day) in Arizona on a tilted plane gives you about 2500kWh/(m.y) With a performance ratio of 90% for your PV installation, you can get 2250kWh/(kWp.y) of electricity.

                    I see that as 6.8 x 365 = 2500. 2500*0.9=2250

                    6.8kWh/(m.day) = solar irradiance/(m.day)

                    You seem a assume 20% cell efficiency is already factored into 6.8kWh/(m2.day). It is not. A typical cell produces more like 1 kWh/m/day, not 6 kWh/m/day.

                    • forgive my units.... all m = m2
                    • Re:Math check (Score:4, Informative)

                      by BlackPignouf (1017012) on Friday May 09, 2014 @01:56PM (#46961113)

                      Sorry if I wasn't clear.
                      I don't need to assume *any* cell efficiency, since this information is irrelevant.
                      The only needed information to calculate the energy yield are :
                      *) Solar irradiance
                      *) Nominal power
                      *) Performance ratio

                      Two 3.6kWp pv installations will produce the same energy yield for a given performance ratio, independently of their cell efficiency (i.e. size).

                    • Let's ignore the losses (i.e. performance ratio = 100%) and compare two installations.

                      PV Installation #1, 20% cell efficiency, 1kWp :
                      With 6.8kWh/m**2.day of irradiance and 20% efficiency , you get 1.36kWh/m**2.day of electricity.
                      The installation covers 5m**2, so you get 1.36kWh/m**2.day*5m**2/kWp = 6.8kWh/kWp.day of electricity

                      PV Installation #2, 10% cell efficiency, 1kWp :
                      With 6.8kWh/m**2.day of irradiance and 10% efficiency , you get 0.68kWh/m**2.day of electricity.
                      The installation covers 10m**2, so you g

                    • You must assume cell efficiency if you are calculating based on the 6.8kWh/(m.day) extracted from the map/chart. It is absolutely relevent, hence the error in

                      6.8kWh/(m.day) in Arizona on a tilted plane gives you about 2500kWh/(m.y) With a performance ratio of 90% for your PV installation, you can get 2250kWh/(kWp.y) of electricity.

                      Which is more correctly 0.15 x 2500kWh/(m.y) = 375 kWh/(m.y)

                      You can ignore that method, and begin with a different starting point and instead calculate from a given cell rating, then the 90% performance ratio makes sense and yes, physical size does not matter, only the equivalent full solar hours. Which often ranges between 5 and 7, but is differen

                    • Which is more correctly 0.15 x 2500kWh/(m.y) = 375 kWh/(m.y) electricity
                    • That is utterly ridiculous. You just changed the size to compensate for the change in efficiency. That is totally meaningless, and not related to the original calculation, which was based on an assumed carport size (area). If you assume a size (area), then efficiency matters. If you assume it can be any size, then you can't calculate the output.

                      Simply put, if you use 6.8kWh/m2/day, the only way you can calculate the electrical output is to use the conversion efficiency, which change the units to electric
                    • Why is it ridiulous to consider nominal power and not area?
                      You pay your installation per kWp, not per m**2.
                      You choose your inverter depending on kWp, not m**2.
                      You choose your cable section depending on kWp, not m**2.
                      As long as a pv installation fits on a roof, carport or satellite, nobody cares about its area.

                      You assumed a wrong carport area (40m**2 instead of 27m**2) and a wrong efficiency (20% instead of ~15%) instead of just googling and finding out that the carport nominal power is 3.6kWp.

                      And once again

                    • 6.8kWh/m2.day represents the available power of the sunlight hitting a square meter of surface in a day, on average. To obtain KWH electrical per day using 6.8kWh/m2.day, you must;

                      1) Convert solar to electrical (0.15 efficiency, or whatever you assume the solar panel conversion efficiency is) to get kWh-e/m2.day
                      2) Multiply by the surface area of the panel. to get kWh-e/day terminal output
                      3) Factor any electrical losses from panel output to load. kWh-e/day system output.

                      The 3.6 KW-e/Panel is a panel
                    • The factor you should be using rather than 6.8kWh/m2.day can be found here;

                      http://www.wholesalesolar.com/... [wholesalesolar.com]

                      If we have a panel rating of 3.6 kw,

                      3.6KWp x 6 hrs/day x .95 (loss factor) = 20.5 kwh/day

                      Notice the units work out.
      • Re:How long? (Score:4, Insightful)

        by donaldm (919619) on Friday May 09, 2014 @06:25AM (#46957459)

        It looks to be using 24 panels in a 6x4 configuration.

        'Standard' 250W panels are 40"x65", giving my 20'x22', so 'close enough', especially if you slant it a bit.

        Assuming ideal, that's 6kw. More realistically 3kw in most areas, about 43kwh per day. About 129 miles of electricity at 3 miles per kwh.

        Sounds good on paper, however unless the person who uses this is a night worker the whole array is pretty much next to useless since most day workers would have taken their electric car to work and only return to park under their now non functioning solar car port once the sun has gone down. Of course if we consider the weekend the electric car could be recharged during the day unless the driver has decided to take the car to say a shopping centre. So I think I would be fairly confident to say that with regard to recharging the electric car most of the charging would actually be from the mains.

        Instead of spending money on a car port just to power their car it is more practical to feed the solar power back to the grid and/or powering devices that require power during the day. This is not to say that the car port is a waste of money but like anything that is solar powered some thought is required on the best use of the device.

        • I'm reasonably certain that the carport solar cells don't jack directly into the car. Solar input fluctuates too much, so at a minimum, you'd need charge controllers. Most likely, also fixed batteries, to allow for the fact that people are more likely to be away from home when the sun is out.

          I still like the idea, though. Even if it wasn't a 100% solution, it reduces overall grid requirements. Plus it takes energy that would otherwise either heat up the carport or reflect into the greenhouse and put it to p

        • by AmiMoJo (196126) *

          Even if the owner doesn't use that energy to charge their car they can feed it back into the grid to offset what they take out at night. might even get feed-in tariff. Alternatively it could be a business buying the PV to reduce its energy costs and provide a nice perk to employees.

        • Re: (Score:2, Insightful)

          by drinkypoo (153816)

          Sounds good on paper, however unless the person who uses this is a night worker the whole array is pretty much next to useless since most day workers would have taken their electric car to work and only return to park under their now non functioning solar car port once the sun has gone down.

          Dingdingdingdingding!

          So I think I would be fairly confident to say that with regard to recharging the electric car most of the charging would actually be from the mains.

          Well, let's cover the office and the shopping center and the parking garage with solar panels. At least some of it could come from the sky at the point of use. And if you're going to run a lot of capacity there anyway so that cars which are there can be charged, it's a good place to site the panels even when they're not being used locally.

          • Well, let's cover the office and the shopping center and the parking garage with solar panels. At least some of it could come from the sky at the point of use. And if you're going to run a lot of capacity there anyway so that cars which are there can be charged, it's a good place to site the panels even when they're not being used locally.

            Offices and shopping centres already use a lot of power. I'm not sure why the existence of electric cars really changes anything - they haven't installed PV to cover their usual energy consumption so why would they install PV to charge your car?

            • by drinkypoo (153816)

              they haven't installed PV to cover their usual energy consumption so why would they install PV to charge your car?

              Because there's a finite amount of electrical energy available to them due to real-world considerations, and a time may come when they may not actually be able to buy more. If we substantially increase our use of EVs without increasing our centralized power generation capability, we'll have to increase it in a distributed fashion. Also, solar panels can improve the life of roofs, and these are roofs which are already predominantly flat and thus less hazardous to wander around on.

            • In affluent and sunny enough areas they already install carports to help keep people's expensive cars cool and unfaded.

              So I can see installing solar panel car shades to attract people through a combination of
              1. Offering electric chargers(cheap enough)
              2. Drawing the greens(they have solar panels!)
              3. People who just hate hot cars(shelter!)

              They might also realize significant savings through tax benefits because it's not a shelter(no incentives), it's a solar system mounted high enough to be out of the car's

        • Instead of spending money on a car port just to power their car it is more practical to feed the solar power back to the grid and/or powering devices that require power during the day.

          That's actually just what they're doing, FTA [motorauthority.com]: With the Wallbox Pro’s features, excess solar energy not needed to charge the car can be used by the connected house.

          In short it's a grid tie system that advertises itself as a car charger. Only reason the electricity would go primarily 'to the car' would be proximity.

          The interesting thought I had is that if you write the work description right you could get the 30% federal credit for the whole carport by claiming the support structures are there for the

        • My car sits in the sun for 8 hours per day. While I'm at work.
    • Re:How long? (Score:4, Insightful)

      by AmiMoJo (196126) * <mojo@NOspaM.world3.net> on Friday May 09, 2014 @04:27AM (#46957171) Homepage

      The point is not to rely on solar for charging exclusively, the point is to add some up-front cost in exchange for a lower running cost. You are spending tends of thousands on the car port, perhaps with a dedicated high speed charger, so you might as well throw in a little more and harvest all that free sunshine too.

  • by JaredOfEuropa (526365) on Friday May 09, 2014 @03:34AM (#46956987) Journal
    ..., a qualification which usually applies to "concepts". It's a nice idea to charge your car using solar panels, but if you're commuting, your car will not be sitting in that car port during the most sunny hours of the day. Besides, you can put those solar panels anywhere; choose the most efficient spot, which isn't necessarily the carport roof. Also: simply laying down solar panels on a flat roof is inefficient; you'll want to mount them at a 30 or so degree angle facing south.
    • by Firethorn (177587)

      First up, it's not like solar carports are a new idea [google.com]. Note that in many of the pictures the cars were clearly under solar panels in commercial lots, so that handles the commute

      Still, this is a lot better idea than putting solar panels on the car itself, at least a carport will have a predictable amount of sun, and as you mentioned, it can be angled properly.

      I'd note that this 'solar charging station' is actually only so in name, instead being a standard grid-tie system. The benefit is that covered car po

    • While it does have some kinks to work out, consider:

      1. While those working at the equator will indeed have the car at home when it's mostly dark out, a sizeable population of those well-to-do enough to afford cars live far enough north (or south) of the equator that their car will be home for quite a number of daylight hours.

      2. Quite a number of people work from home these days. In this instance you WOULD be home the hours you're working.

      3. Of those not working from home, a large portion are business ow

  • Glad to read that they at least suggest that this thing gets connected to the main electicity grid (so they also deliver electricity when the car isn't charging, which is most of the time). Also, I guess you should just charge the car from the grid as well. Many people will tend to drive in the day, and charge at night, so, off the grid really seems silly. A rough estimate tells me that the panels could deliver as much as 10 kW (if you're lucky), so size-wise this is not enough to charge the car quickly. An

    • by Firethorn (177587)

      So, using a flat surface of the carport roof for solar panels? Good idea. But it's just not really relevant to involve the car in this story, as you'll be charging it from the grid, like everyone else with an electric car.

      It's more using solar panels AS the roof to save having to put a regular roof on, with it being a grid-tie system. Thus, you can consider the cost of the solar system to be reduced by what the cost of a conventional roof would have been. Since that could be 30% of the cost of the solar cells, it's not insubstantial. Plus, 30% federal rebate(in the USA) on said solar roof, while there's none for a conventional one, and you might even be able to deduct some of the carport construction by saying the support

  • So, you install solar cells, but you only actually get to use them when your car is in the carport - otherwise they're a wasted investment. Given that solar cells already cost more per kwH that most other types of electrical generation, that makes a whole lot of sense - not.

    Anyway, is "functional art" mean to be a euphemism for "ugly as sin"?

    If you want to put solar cells on a roof and attach them to the grid, more power to you. But that's not what they're touting here.

    • If you read the fine print, it's a grid-tie system, it feeds the electricity to the house/grid for net metering if a car isn't sucking down all it can provide and more.

      Anyway, is "functional art" mean to be a euphemism for "ugly as sin"?

      It's also not to my taste, but I can see somebody liking it. It has more 'soul' than conventional painted beams would.

  • Even if the solar panels had the right inclination, they'd produce 2-3kW at most.

    And you'd have to park the car there during the day. Most drivers use their vehicle during the day and leave it parked at night.

  • If you're going to install solar panels then putting them on a car port is often not going to be the smart thing to do. You want to pick the place with the best exposure to the sun, which will often be the house roof. And you don't want to use the power generated just to charge up the car - if you've got the panels you might as well feed the power into the house for general domestic use. There is some additional overhead in sorting that out - buying an inverter and doing the wiring - worth it in the long ru

  • by Hypotensive (2836435) on Friday May 09, 2014 @04:12AM (#46957135)
    I suppose beauty is in the eye of the beholder, but to this beholder it looks like something that would drive property values down, not up.
  • by geogob (569250) on Friday May 09, 2014 @04:26AM (#46957163)

    As I am currently looking into buying an electrical car, I was considering doing (almost) exactly this : Installing solar cells on the roof of the house to charge the car. It wouldn't even take that much solar cells; 20 square meters would charge the car in a reasonable amount of time. Free energy, right?

    While considering the idea, a fundamental problem stuck me: Most of the time when the Sun shines, the car isn't parked at home. It is either parked in front of my office or, when I'm not working, I'm driving somewhere else, enjoying the Sun that could have charged my car. The solution to this issue was to add batteries to the concept, in order to store the Suns energy as I am away and transfer this energy back to the car at night when I am home.

    Considering the car has a capacity exceeding 20 kWh, the battery solutions becomes extremely expensive - as expensive as the car itself actually (if not more). Without the battery, it's a nice expensive systems that will produce a lot of power when I don't need it. It's always possible to sell back the excess power to the utilities, but you get a loss let out of it this way and it makes your life quite complicated.

    Forgetting this fundamental limitation, after doing a lot of calculation, it turned out that it would take over 20 years to amortize; and I doubt the battery system would last 20 years under the kind of stress it would be put too (nearly daily full deep cycles). And this is assuming the normal electricity prices. In fact, the charge stations are highly subsidized and your are basically paying the price large industry would pay for electricity. Suddenly your amortization period goes up over 40 years.

    It's not (yet) worth it, although the technology is actually there and ready.

    Conclusion : Power accumulation solution in the 20 - 40 kWh range are too expensive and power is too cheap.

    • by Lumpy (12016) on Friday May 09, 2014 @06:28AM (#46957467) Homepage

      So hook the solar cells into a syncing inverter and drive your electricity meter backwards. Use the power company as your battery.

      • by geogob (569250)

        It might look that simple, but it isn't. Here at least, this is strongly regulated. The only thing you can do without it being a pain is to use the power and stop the meter.

        • by Lumpy (12016)

          Wow, Around here the Power company MUST allow you to feed backwards and they have to either allow the meter to run backwards or buy the power from you.

          I back feed from 200 watts of panels as a simple plug in system here and it actually made enough of a dent that it paid for the $450 in micro syncing inverters and two panels in a single year.

        • by LandKurt (901298)

          The reality of cheap solar panels is that batteries are now the more expensive part of an off grid system. And for a grid-tie system the permits, inspection, and professional installation is a big burden in the US. All those regulations are annoying, but when you’re playing with thousands of watts it’s reasonable to ensure the safety of linesmen, firemen, and occupants.

          Grid-tie ends up being cheaper than battery systems and maximizes solar production of the panels as power doesn’t go unuse

    • by jcgam69 (994690)
      I leased panels for my house to charge my all-electric car. Since I paid for the 20 year lease in advance, my power costs about 10 cents/kwh over the 20 year period. I don't know where you live but in my area this is about half the current average cost of electricity, and the price per kwh is sure to increase over the next 20 years (for everyone else). Since the system is grid-tied I don't need a battery for the house. As an added bonus I never have to wait in gas lines. I'm actually saving money by no
  • by Solandri (704621) on Friday May 09, 2014 @04:41AM (#46957215)
    A typical sedan gets about 30 mpg. Figure the average car travels 15000 miles in a year, or 41 miles per day on average. That means it burns 1.37 gallons of gas each day.

    A gallon of gas has about 120 MJ. Gasoline engines are about 25% efficient, so the 1.37 gallons of gas consumed represents 123.3 MJ lost as heat, and about 41 MJ of energy used to push the car each day.

    Charging a battery is about 75%-85% efficient; call it 80%. Realistically you'd need another battery to sit at the carport charging (leaving the car parked there all day to charge means you can't drive it). This battery would also help even out the cloudy days with the sunny days. So since you're charging from battery-to-battery, you're hitting this 80% efficiency loss twice. Electric motors are about 90% efficient (that's peak, but then so is the 25% efficiency for an ICE). So for an EV to put 41 MJ into pushing the car, it needs 41/(.8*.8*.9) = 71.2 MJ sent to the carport's battery.

    PV panels generate about 150 W/m^2 peak. Multiply by the average capacity factor for the U.S. of 0.145 to get 22 W/m^2 on average. Multiply by 24 hours and you get 1.9 MJ/m^2 per day.

    So to charge your typical sedan EV entirely with solar power to drive it 41 miles per day, your carport would need 71.2/1.9 = 37.5 square meters of solar panels. Or 404 square feet for those in the U.S. That's a mighty big carport.
    • by Calinous (985536)

      It's a two car port

    • by fche (36607)

      "Multiply by 24 hours and you get 1.9 MJ/m^2 per day."

      You can multiply it with any number you like, but you won't get much sunshine at night.

  • by Lumpy (12016) on Friday May 09, 2014 @06:26AM (#46957463) Homepage

    As if a BMW owner will live in a place with a "car port" and not a garage.

    No the 20 something working at walmart that is driving the beat up 325i does not count.

    • As if a BMW owner will live in a place with a "car port" and not a garage....

      No joke. See how the HOA feels about building this carport on your property...

      • As if a BMW owner will live in a place with a "car port" and not a garage....

        No joke. See how the HOA feels about building this carport on your property...

        "But the article called it 'stunning functional art!"

        "Yea, well, it looks like a big ugly spider to us; request denied, beeotch."

    • by geogob (569250)

      I see a lot a of BMW parked under car ports everywhere here in Germany.
      (And I still have to see a Walmart)

      • by Lumpy (12016)

        Your country it would be Aldi stores, and in Germany BMW is usually driven by the Volk. Here they are only reserved for the $250,000 euro or higher income level as they are special and only allowed for the ruling class.

        • by geogob (569250)

          I do not believe the Aldi - Wallmart comparison is fair. And having lived over 30 years in Canada, I can confirm that there you also find BMW under carports. Not quite as much as here, but a lot...

          For the reference, except a few models, BMW cars are expensive as well in Germany. The German tend to invest more on their cars (incl. maintenance). It's something important - which I can understand when you drive usually 150 - 180 km/h (93 - 112 mph) in normal trafic conditions .

    • by MrMarkie (1079197)

      I hate to burst your bubble but I'm a BMW owner who doesn't own a garage and my car is not of the beat up variety.
      It's not like a BMW is that expensive anyway.

    • by Type44Q (1233630)

      No the 20 something working at walmart that is driving the beat up 325i does not count.

      My beat-up 325i has an electric drivetrain from HobbyKing, you insensitive clod!

  • I even wrote to them, put some solar cells in the sun roof, use it to drive a couple of vent fans for hot days. Usually on the days I need it, there is plenty of sun light. I think some old car, may be Mazda Millennia, replacement for their 929, had it. But none of the car makers provide it. I am sure this idea is patented by someone and asking either too much, or these companies are stingy. Are there after market solar driven vent fans for parked cars?
  • This is a concept. Concepts can be improved!

    As long as your commute doesn't run your battery down completely, and as long as you charge tend to recharge more than you discharge through use, a car port like this will keep you topped up.

    This could also be hooked up to your mains to supply most of your own electricity.

    Maybe, if car makers came together and created standard battery sizes, capacities and forms, you could build in battery swap station to allow your battery to be recharged when you are not at hom

  • by necro81 (917438) on Friday May 09, 2014 @07:58AM (#46957793) Journal
    I spent a few months living in Arizona some years back. I lived in an apartment complex where most of the space between the buildings was the carpark. The most coveted spaces were the ones that had a sort of awning or overhang, so that the car was out of direct sunlight. It made a huge difference in how hot the car got.

    As an engineer, seeing this vast swath of paved-over space (more than an acre all told), some of which was itself covered with structures specifically intended to block the sun, I thought to myself: why in the hell don't they just cover the entire carpark, and cover it with solar panels, to boot? The complex could advertise itself as having all-shaded parking (and commensurate higher rent) and reduce its net electricity consumption. In sunny Arizona, such a project could have paid for itself in less than a decade; today, the economics are even more favorable.

    My question is: why isn't this (grid-tied, solar panel-shaded parking lots) done by every piece of commercial real estate in sunny climes? You make greater use of a resource (land area), the tenants' cars end up cooler (you can charge higher rent for that), it has a more or less guaranteed return in a reasonable time span, and reduces operating expenses (lowered electric bills). See, for instance, the western parking lot at the Googleplex headquarters [google.com]. Why isn't this done everywhere?
  • All that expensive light weight carbon fiber is completely worth it because it will help my carp port accelerate faster when its picked up by a wind storm.
  • But I can still ask if the carport matches the drapes?
  • Carbon Fiber is a poor choice if you're looking at sustainability. It's energy intensive to make it. The primary components are made from petrochemicals. It's not recyclable. You would be better off using cast aluminum for the supports and arches -- while it takes a lot of energy to extract initially, it's fairly robust and can be readily recycled 20 or 30 years in the future when the carport gets replaced.
    • by khallow (566160)
      For me, the problem is simply that the structure in the article doesn't take advantage of carbon fiber's characteristics. You could replace it with aluminum and probably strengthen the structure in the process. Buildings in general just don't have a lot of ways to exploit the special light weight/relatively high strength properties of carbon fiber.

      Ignoring cost, I could see doors and other things that need to move getting some advantage by being made from carbon fiber. I suppose one could make a facade o
  • The idea is to use solar to charge an electric car. OK, might work in some locations for some use cases, but hardly innovative. They had a architect design a support for the solar panels that some people may think is aesthetically pleasing. OK, but again not exciting. They want carbon fiber and bamboo. Again OK, but it could have been recycled plastic, or old aluminum cans, or adobe or pick your favorite "green" material of the day.

    Why is this slashdot worthy? (except as an ad for BMW)

  • Why not put solar panels on the car roof, hood, and trunk?

    Sure, you have less surface area, but unlike the garage, they would always be within reach of the car and charging it. Those 5 and 6 series BMW's are nice and wide too!

    Plus, if you like black cars, it would look cool.

    And no whining about engineering or cost, BMW doesn't compromise on either of those fronts!

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