Let me take the math another direction. It looks like David calculated a net gain of about 84,000 Wh per year. Let's round that up to 100,000 Wh per year. That is 100 kWh. Assuming electricity costs somewhere between $0.10 and $0.40 per kWh. Sounds like yearly payback is somewhere between $10.00 and $40.00.
Sounds kind of small for an investment of more than $1000. Mike On September 22, 2015 7:19:43 AM MDT, EVDL Administrator via EV <[email protected]> wrote: >On 22 Sep 2015 at 3:50, brucedp5 via EV wrote: > >> ? Is this a useful product worthy of the co$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) _______________________________________________ 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)
