Can a house or business charge an electric car?

Electric vehicles are becoming more popular but only a smaller number of owners power those cars with electricity generated from rooftop solar panels.

“If you live in a house that makes all its power from solar, you reduce your carbon footprint for the house down to zero,” said Richard King, “But if you live in a zero emissions house with two fossil fuel powered cars in the driveway, you’ve only reduced your carbon footprint by half.” In the US, an average family of four produces as much carbon with their two cars as the house does on a yearly basis, according to the U.S. Department of Energy.

There are two types of electricity – alternating current, or AC, and direct current, DC. It is more efficient to transport electricity over large distances. But as more homes adopt photovoltaic panels, or rooftop solar, to generate DC electricity locally – in the same place where it is ultimately used – DC power is more efficient. The electricity generated by rooftop solar is DC.

AC to DC inverters are currently being used by operators of electric vehicle fleets to charge their cars at lower electricity rates and to store solar-powered electricity in their batteries. Using the DC inverter is needed to charge an electric car that also runs on DC power. Most homes that add rooftop solar need to convert DC power to the AC grid, and then convert it back to DC when it returns to the house to charge a battery electric vehicle that also runs on DC. And each conversion from AC to DC saps as much as 10 percent of its usable energy. Using the DC directly eliminates some inefficiencies and saves more power to muse in the vehicle

The car is projected to use about a third of the home’s entire daily energy allotment. Rooftop solar could easily use an electric vehicle’s batteries to store excess electricity generated by the rooftop solar. An additional benefit is that an all-electric car fueled with a home’s rooftop solar panels can, potentially, clean up its carbon emissions.

It’s estimated that homes would need an additional 2 to 4 kilowatt hours of photovoltaic panels to generate enough electricity to fuel an electric vehicle that’s driven 50 miles a day. Rooftop solar can inspire us to pursue this technology in the future and to realize that, first of all, it can be beautiful. Secondly, it can be energy efficient, and third it can be sustainable to use for centuries to come. There’s no other energy conversion for how we should live that can claim that,” “We’re going to run out of oil. We’re going to run out of natural gas. We’ll have problems with greenhouse gases from all these other technologies. This one, we could be using it centuries from now.”


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