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 = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
