Here’s a question I’ve chewed on for awhile and which I figured I would put in front of the SolarChargedDriving.Com community to see what others think:
Should solar offset count as a solar-charged mile in an electric vehicle?
Or, differently put, is the only “true” Sun Mile®, or Sun Kilometer, one which has been powered directly, and 100-percent by solar electricity?
I’ve waffled on this issue for awhile, but recently have tended toward being okay with seeing solar offset as essentially the same as a solar EV mile that’s been powered directly and 100-percent by solar electricity.
In fact, the question of whether solar offset should count as a legitimate solar-powered EV mile, or what we call a Sun Mile®, is complicated.
Plugging in at night
Some have claimed it’s “intellectually dishonest” to link solar offset to the EV miles one drives. They point out – correctly – that if you charge your EV at night, the electricity in its batteries has been produced by an electric grid mix without a single drop of solar. According to this view, it’s cheating to claim that any of the miles you’ve driven in your EV after you’ve plugged in at night are solar-charged miles, or Sun Miles® – even if you have offset the electricity used to power these EV miles with electricity produced by your home solar system at a different time.
According to this perspective – what one might call the instantaneous power matching view -- it doesn’t matter if your solar system produces exactly the same number of kWh you drive on a per day, per week, per month, or per year basis. If you don’t plug your EV in when your solar system is producing the electricity that flows into its batteries, those miles cannot be considered solar-charged miles. Period.
Others, who hold what one might call a net-energy view, say, hold on a second: The electric grid is like a bank. A kilowatt hour is like a dollar, they say. When you deposit a dollar bill in the bank – or contribute a kWh to the electric grid with solar, you’ve contributed that dollar bill, or kWh, and you “own” it. Later, when you withdraw money from the bank, you won’t get that same exact dollar bill you put in, and the kWh you draw won’t be exactly the one you produced earlier, but you contributed to the bank or grid exactly the same amount of money or energy you are drawing from the bank or grid.
Additionally, some of the net-energy folks ask: If solar offset matters not one bit when it comes to determining how clean an EV is, does solar offset mean anything at all for anything at all, whether it’s an EV, or a plasma TV, or a refrigerator, or a dryer?
Solar offset bogus?
In fact, the whole question of what is, or is not a “true” Sun Mile®, and whether it is “intellectually dishonest “ to claim solar offset as powering one’s electric vehicle goes right the core of the whole notion of solar offset, regardless of whether one is talking about solar offset for an EV, or for a dryer or refrigerator.
What about the Feds – will they try to determine the pollution output of your solar-charged EV down to the individual puff cloud that passes over your home solar system, or will they do it on a net-energy basis? And what might their decision mean to you, me and anyone else who drives an EV, solar-charged or not?
Indeed, if you take the “it’s intellectually dishonest” to count solar offset toward EV miles to its logical extreme, solar itself would seem almost pointless, at least from an individual solar owner’s point of view.
The vast majority of people with solar – at least those who work someplace other than their home -- tend to use much, if not most, of their electricity when their solar system is not producing.
Are they being “intellectually dishonest”, if, at the end of a year with solar, their solar system has produced 100 percent of the electricity their household has used – it doesn’t matter if it has an EV or not – but 80 percent of that solar produced electricity was not directly used by them, but by their neighbors while they, themselves, covered only 20 percent of their electric use with the pure solar electricity generated by their home solar system with the remaining 80 percent of their electric use being powered by the grid?
On the other hand, an EV charged at night and a dryer, a refrigerator, etc. running at night are clearly not being fueled directly by solar electricity even if at the end of the year, your total solar system’s kWh production equals – or exceeds – the kWh you’ve consumed during that year.
Night-time grid mix
The grid mix fueling your electric appliances at night is whatever your utility is running at night. In fact, it can be even more specific. A utility’s fuel mix can vary down to the hour, even down to the minute.
This is where things get very, very complex – and where the Federal government has a giant challenge on its hands: How does it, for example, measure the pollution output of EVs if the grid mix that’s fueling an EV varies radically according to geographic location – which, in fact it does – and if the grid fueling mix being used to generate the electricity filling that EV’s batteries varies on a time basis as well?
Add residential solar, solar powered EV-charging stations, residential wind, residential geothermal to the whole equation and throw in the question of renewable energy offsets and you have one wildly complicated equation.
And what about the extreme variability of solar, or wind, for that matter?
What if I want to be as “pure” as possible and charge my EV while our home solar system is generating its peak energy, between 10 a.m. and 2 p.m.? What if our charging session is chugging along and I’m watching my TED, which allows us to observe, by the second, our home’s net electricity use and we’re 99.9% to a fully charged EV battery pack when, boom, a big dark cloud drops our solar system’s output to near zero and that last .1% of electricity pumped into our EV’s pack is -- damn it! -- 70 percent coal and 30 percent natural gas generated?
Are we being “intellectually dishonest” if we claim the next 70 miles we drive in our EV are solar-charged? And what about the Feds – will they seek to determine the pollution output of your solar-charged EV down to the individual puff cloud that passes over our home solar system, or will they do it on a net-energy basis? And what might their decision mean to you, me and anyone else who drives an EV, solar-charged or not?
The answers aren’t clear or easy. In fact, they have a lot to do with what perspective one brings to the EV fueling equation, whether that view is an instantaneous power perspective or a net-energy perspective. The disagreement about what perspective to bring to the question of how to treat and understand solar-charged driving is one reason the issue of what constitutes a “true” Sun Mile® and how to measure, and, of course, compare, the pollution output of EV + PV is shaping up to be a potentially controversial one.
- What are Sun Miles®?
- Solar-charged driving 101
- EV/PV activist to sell LEAFs + solar
- Driving on sun -- it's a gas!
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Web blogs by current solar-charged drivers
-- Peder Norby's Electric BMW ActiveE Blog
-- Darell Dickey's EV Nut Web Site
-- Doug Korthof's Live Oil Free Pages
-- The Solar-Charged Electric Car Page
-- Solar Power and Electric Cars
-- Sun Powered EVs
-- Ecogeeco Web Site