The efficiency of a complete grid tie system is about 75 - 77%. If that is not mentioned then yes, it's baloney-nosed. The price of panels have come down. Used to be $3/W, now you can find
Were it really a cheap form of R&D stimulus. It seems to me that every government-insured loan that Obama handed out for renewable energy (or green anything for that matter) has gone into default... with government guaranteed benefits for his fat-cat buddies who contributed to his campaign. ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
Tom Biasi wrote in news:_aMgw.1509943 $ snipped-for-privacy@fx21.iad:
Do the maths yourself. Its the only way to be sure that noone with their own axe to grind has shaded the figures in their favoured direction.
You cannot count on any government subsidised feed-in tarrif or tax rebate being valid past the next budget.
Solar cell lifespan is often nowhere near as good as claimed (e.g. in marine applications, 10 years is an *excellent* lifespan with most failures being moisture and corrosion related. If you are in an area with high pollution levels, on the coast, or next to a road that is salted in the winter, your roof may be as hostile an environment as a marine instalation)
Dirt on the panels vastly reduces efficiency - either budget for regular cleaning or seriously oversize the panels.
Dont forget aging and depreciation for ancillary equipment e.g. charge controllers, inverters etc. Getting lifespan estimates may be difficult
- use a reasonable fixed multiple of the manufacturer's warrenty period if you have to!
Then there's battery banks. Just about every technology except NiFe cells wear out in cyclic use.
Finally, dont forget the lost R.O.I. cost of all the money you would have tied up in the system.
The last time I even ran a back of an envelope analysis (about 5 years ago) it just didn't make sense except for off-grid applications or where the cost of a grid connection would be excessive (either one-off to get the supply cable to the location or recurring costs where the total annual usage is small enough that the standing charges dominate).
I suspect (but cannot prove) that if you figure in the total energy cost of production from raw materials + transport, most consumer lever alternative energy sources are actually a net energy loss over their actual lifespan. Exceptions: wind or water driven generators built using mostly recycled materials and solar thermal water heating.
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Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
There is one data point to consider. Back in the wake of the oil crisis in the 1970s, a bunch of subsidized solar companies and efforts were started. All vanished when the subsidy ended.
I know nothing of US party politics - other places in the world subsidise solar PV too. It is also a fact that 'fat-cat buddies' will profit wherever they can, whatever the perceived colour.
I also suspect that the panels, batteries, and the associated structures and electronics, will generally not last the 20-25 or whatever years used for the ROI calculations. Nor do they include the roof maintenance complications or cleaning cost.
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John Larkin Highland Technology, Inc
picosecond timing laser drivers and controllers
15m^2 sounds like the cheap amorphous type panels. They don't last as long as the Multi or Poly crystalline panels. The amorphous type have a inherit ability to loose 20% of their output within the first 5 years. Plus they take up more room.
[speaking from the desert southwest where solar is probably more effective than someplace "up north"]
Solar *pool* heating has an almost immediate payback. Some techniques can payback in one season!
Solar *heating* (passive) has a (relatively) short term payback. Good windows, thermal storage elements, etc. But, if you've got an existing edifice and it's not sited optimally...
Solar *water* is close to 5 years -- if you can do your own plumbing.
[labor costs make many of these things impractical; without the labor costs, many more paybacks make sense!]
Solar PV's, IMO, don't have a payback even with subsidies/credits. We see LOTS of LARGE installations, here and shake our heads in disbelief -- even if they're "youngsters" who've got enough (projected) years on the planet for "payoff" to have some chance!
(How often do you have to work on your roof? even concrete tiles experience failures in the underlayment. Is the roofing contractor competent to remove the necessary panels, repair the roof and replace them?)
Starting over (i.e., if I was younger), I'd first invest in an earth-bermed/below grade living quarters. That alone would make the most savings on heating AND cooling (how much of your electric goes into that big AC compressor(s) out back?)
And, I'd opt for low voltage lighting throughout the house (instead of losing power in converters, etc).
2KW wouldn't satisfy much of an AZ electric load. ACbrrr is probably 5KW (granted, it doesn't run continuously and typically runs during the day more than at night -- though it still runs at night!). Electric oven is 3KW. Ditto for electric dryer.
Refrigerator is probably 1KWHr/day (that alone is ~20% of your 2000KWHr/year figure). Electric hot water heater is probably half that (?)
The problem is the big peaks on which you can't really exploit load leveling algorithms. The ACbrrr is going to draw 5KW when it kicks in -- nothing you can do to spread that load out over a longer period (batteries -- which wear, especially with our high ambient temperatures!)
I'm not sure if you can operate under the same tariff if you go solar. So, you may end up with a *higher* rate for energy that you draw off the grid once you sign up. I.e., forcing you to buy extra capacity to avoid incurring those charges.
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