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.
Stranger