Anyone know if it’s possible to charge an electric car (say a Tesla model S) off of just solar panels, completely off the grid? Money is no object and I’ve got acres of land. Let’s say I want to match the on-grid charging times of what it normally takes to fully charge an electric car.
The next question is - what are my time options? If I only have to drive 25 miles a day and don’t need to fully charge my car on a regular basis, what kind of set could I get away with?
I have a friend with a largish solar panel farm that powers his house and charges his Chevy Volt. I’ve ridden around in the car, and it seems pretty nice. His range is limited, and he is always concerned with the miles driven ie “point of no return”.
He gets pissed that he has to charge the car at his office sometimes, and that “costs him money”.
Yes, I should have said “it” was using solar off the grid. There is nothing special about charging a car vs running a clothes dryer or an oven. With a 220V, 30A outlet, you can charge the car batteries in about 5 hours. If you have more time, you can use a 110V, 15A outlet.
The Tesla S has a 60 or 85 KWH battery. Depending on where you live, I believe solar panels only produce about 3-8 wh per watt of panel. So you would need anywhere from 8KW up to 30KW of panels to charge the car. What would be the cost of that? Panels themselves are not too expensive now, they are under a dollar a watt. Still that is just part of the cost, installed costs about $3-4 per watt in the US. At the high end the solar panels would cost as much as the car. This assumes you fully drain and recharge the battery each night, which is unlikely. So perhaps a fraction of this, if you are just doing daily commuting.
Grid energy to recharge a tesla S would be something like $0.10/kwh. So about $6-8 to charge the battery. FWIW, that sounds like more than it costs to run all of a household’s appliances.
Well, what’s special about charging a car is the large amount of power needed. The results of my Google search indicate that the output of a “typical” panel used in a house is about 200W. How many panels are needed for how long to recharge a car? Is it practical, even if you’re also not attempting to power the rest of the stuff in the house?
The charger on the Tesla S is on-board and converts 115 VAC to a 375 VDC potential in order to fully charge the lithium ion battery pack. Although it would be more efficient to simply charge the Tesla with a direct current input, it has no provisions to accept DC power (understandably, as 375 VDC would present a significant hazard at even small amperages) so your solar farm has to be connected to a power supply which can convert the current load to a three wire single phase alternating current at 115 VAC. Also, because you are likely using the car during the day and only charging in the evening through early morning, you have to have a storage system for the electricity generated during the day. (You would want this anyway for load balancing so that you get maximal charging without having to worry about the cyclic variation in solar incidence or cloud cover.)
How long it will take to collect sufficient energy how much collector area you need depends on location and climate. The Tesla S has a 53 kW-h battery capacity; Sunny Southern California has an average incidence of around 4 kW-h / m[SUP]2[/SUP]-day. So, to fully charge a battery from one day of solar energy collection, you’ll need 13.25 m[SUP]2[/SUP] of collector area, not accounting for other system losses. How much power you will need to go 25 miles a day depends on a number of factors, such as driving style, ambient temperature, how many accessories you power, et cetera, and as the Li-ion pack ages the capacity and peak voltage output will decline. Tesla estimates a 200 mile range for combined city/highway driving, but that appears to assume a near-optimum nominal conditions. If you live in, say, the Pacific Northwest where solar incidence is in the fractional kW-h range and average daily temperatures are below 60 deg F, you may have to increase capacity by an order of magnitude or more.
Essentially all power that we use, aside from that generated by nuclear fission and geothermal, is solar in nature and simply stored in different forms. This is even true of petroleum; while it is condensed and converted by geological pressure, the capture of carbon and hydrogen into sugars which are then converted into hydrocarbons is done via photosynthesis. Nature has evolved remarkable and elegant mechanisms for capturing and storing solar energy to which our technological solutions are a very crude and inefficient analogue. In terms of storing and using electrical energy for mobile applications electrochemical batteries have some very significant fundamental thermodynamic limitations compared to hydrocarbon fuels such as petroleum distillates, alcohols, and ethers. Of course, the combustion process also releases carbon dioxide into the atmosphere which needs to be offset or sequestered in some fashion to prevent detrimental climate effects, but at a ~US$30k cost for the Li-ion pack on the Tesla S (which despite complaints by customers is probably being sold by Tesla at or near production cost) it is far more cost effective and practical to capture or offset carbon emissions during power generation rather than try to minimize emissions throughout the entire cycle via solar energy and electric motors.
Electric powered vehicles may certainly have their niche in the coming decades, but they are hardly a panacea against net carbon emission notwithstanding all of the infrastructure improvements to the power grid that would be required to support mass conversion to electric vehicles for personal transportation. Internal combustion or fuel cells will still be required for the majority of non-commuter transportation including heavy and bulk goods distribution. Developing methods and a distribution infrastructure to support that need which minimizes net carbon emissions is crucial to avoiding both the limitations of the existing petrocarbon fuel supply and reducing climate impacts. The focus on developing all electric vehicles–and especially one that is essentially a high performance toy for upper middle class drivers who can afford the vehicle–is actually a distraction from the development and implementation of renewable practical transportation fuel technologies and infrastructure.
C’mon guys, this is a THOUGHT EXPERIMENT. Have a little fun. I’m not ACTUALLY going to do this. We’re ignoring if its practical or cost effective.
This is interesting. So if we built an electric car with a removable battery and it came with two of them, I could leave one at home during the day, connected to my field of solar panels charging - while I drove around with the other one.
Perhaps this would be the “best” way to drive “free” off of the sun?