I think it depends on why you want it. If you are altruistic and want
to cut your grid usage, then it helps. If you think you'll get more
range out of a charge, then apply David's calculations to the amount of
Wh you'll get while on the course. Probably just a few percent more
range.
Peri
------ Original Message ------
From: "EVDL Administrator via EV" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: 22-Sep-15 6:19:43 AM
Subject: Re: [EVDL] Light-weight 100W PV roof panel for 48V e-carts> ?Is
it worth it?
On 22 Sep 2015 at 3:50, brucedp5 via EV wrote:
? Is this a useful product worthy of the co$t, or is it a profitable
feel-good add-on for bragging-rights ?
Much of the answer is right in the story:
As a yearly average, the system generates 29 percent of the total
energy
required to drive eight miles per day in West Palm Beach, Fla. That
reduces
the energy needed to recharge the battery by 29 percent. Results may
vary
depending on area and usage.
By continually transferring energy to the batteries, the panels limit
how deep
into the battery reserve a vehicle must go during a typical use.
I suspect this is a best-case estimate. Let's run some numbers.
First let me warn you that there's a fair bit of hand-waving here. I'm
not
an expert in these matters. If you're a PV expert and can come up with
better numbers than mine, by all means please do so.
IIRC a typical golf car range is around 40-50 miles. Using standard
T105
type batteries this amounts to an energy usage of between 126 and 158
Wh/mi.
Let's call it 150 Wh/mi for convenience.
Driving 8 miles per day will require 1200 WH per day or (1200 * 365) ==
438000 Wh/year if you drive the car every day (as the PR release seems
to
suggest).
This panel can produce 100 watts, but if that's a typical rating it'll
only
apply when the golf car is parked in the sun with the sun directly
overhead.
At other times the output will be lower, but I'm not a solar expert so
I
don't know by how much. I'll take a wild guess and estimate that the
panel
will average 30 watts over an average day's sunshine (including dawn
and
dusk). Someone please correct me if that's too far off.
So that's 30W * 12h == 360 Wh/day * 234 days (average sunny days per
year in
West Palm Beach) == 84240 Wh/year. This is 19% of the energy required
to
drive 8 miles per day, about a third less than Club Car claim, but
surprisingly close.
But even my 19% estimate assumes the golf car will be in the sun any
time
the sun is shining. If you park it in a garage, or in the shade of a
building or tree, it gains little or nothing. How many people
deliberately
park their cars (golf or otherwise) in the sun on a hot summer day in
Florida?
Other factors will affect solar gain. For example, if you drive it on
a
tree lined street, or a city street with tall buildings around it, it
will
gain less solar energy.
So, is this just a "feel-good add-on"? Well ... as with any other
vehicle
option, how much a given user gains from this one depends on where and
how
she drives. But for most users, I'd say it'll probably yield more
bragging
rights than range.
What it MIGHT do that's potentially at least as useful -- IF you park
mostly
in the sun --- is dribble a little charge back into the battery when
the car
isn't being driven. That'll improve battery cycle life a bit.
Calculating
whether the resulting battery cost savings will offset the cost of the
PV
panel will be left as an exercise for the reader. ;-)
FWIW, in looking for info on this I ran across several dealers offering
aftermarket PV panel options for golf cars. One claimed a (peak)
output of
220 watts. The price was $1450.
Is it worth it? I see 12v 50w generic PV panels on Ebay for around
$100
each. Five of them would give you peak 250W into a charge controller.
Speaking of which, I see 48v, 30-45 amp charge controllers on Ebay at
prices from $160 to $260.
The dealer I mentioned above also provide a roof frame and struts.
What do
you think that's worth, maybe $150? So they're making around $700 on
each
kit. That's a 100% return on the parts cost. Not too shabby.
David Roden - Akron, Ohio, USA
EVDL Administrator
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