make your ereader run on solar power

[Ken Maltby]

"In conclusion, here is a summary of the solar energy facts
you might want to know if you are looking to buy a home PV system:"

"Peak incident energy at noon on a perpendicular surface: 1 kW/sq.m"

"Average net sunlight energy over a day per square meter: 4 to 7 kWh depending on your location and PV panels angle;"

"Total electricity generated by a PV array over a day:
E[pv]=Efficiency/100×(4...7) kWh/m[squared] , where panel's efficiency is from 6% to 20%."

"For example, for the best cells efficiency of 20%, the daily yield would be 800 to 1400
watt-hours." (per 100 square meters of PV in an array, or 8 to 14 watt hours per
square meter. 30000/14=2142.857 square meters needed.)

"Power generated by the most efficient panels averaged over a day: P[pv]=E[pv]/24, which is 33 to 58 watt/m[squared]."


"In 2009, the average annual electricity consumption for a U.S. residential utility customer was 10,896 kWh, an average of 908 kilowatthours (kWh) per month.
Louisiana had the highest annual consumption at 15,276 kWh and Maine the lowest
at 6,252 kWh"

908/30=30kwh per day

So lets be generous and say the most efficient panels averaged 60 watts per square
meter, for a days output. Then every square meter of the most efficient PV pannels could provide 60 watts of the 30,000 watt hours used per day.

2142 square meters = 0.529 acre. So if you live on a half acre lot and like the shade...

If you live in a house with 2142 square meters of roof space and you have the money
to cover that much space with "the most efficient" PV panels, then have at it.

The American football field has dimensions of 360 ft long x 160 ft wide, which is an area
of 57,600 ft2 or approximately 5351.04 m2.

Luck;
Ken

[carpetmojo]

Quite !

Solar power as it is now, strikes me rather like electric hand-dryers - the triumph of the saleman over practicality.

Wind and wave have far greater possibilities - especially wind for individual properties.
More research into improving/radically redesigning the technology could well arrive at an answer. It is improving all the time as it is.
But there's more £/$ in building the monsters we see popping up all over.

And the lack of progress into wave or tidal power has always baffled me - a constant source of energy for translation into power.

The more materials and technology are improved or invented the more chance there will be - dare I suggest a more immediate pressing need than space travel, right now ?

[frquixote]

Originally Posted by Ken Maltby

"In 2009, the average annual electricity consumption for a U.S. residential utility customer was 10,896 kWh, an average of 908 kilowatthours (kWh) per month. Louisiana had the highest annual consumption at 15,276 kWh and Maine the lowest at 6,252 kWh"

908/30=30kwh per day

So lets be generous and say the most efficient panels averaged 60 watts per square meter, for a days output. Then every square meter of the most efficient PV panels could provide 60 watts of the 30,000 watt hours used per day.

2142 square meters = 0.529 acre. So if you live on a half acre lot and like the shade...

If you live in a house with 2142 square meters of roof space and you have the money to cover that much space with "the most efficient" PV panels, then have at it.

I'm not quite sure where your numbers are off, but I have 28 225W panels from a well-known Japanese manufacturer (cells made in the USA!) that take up 380 square feet (35.28 sq meters) of roof space on my little (1172 sq ft) house and they generate on average 30 kWh/day, which is more than 850W/sq meter/day.

Having spent quite a bit of time studying the available solar panels before buying, I don't know of any that only generate 60W/sq meter/day ... that would be a 30W panel!!! I suspect you forgot to multiply the panel output by the number of hours it is actively generating power. Here in Hawaii we see an average of 5.8 hrs generating per day, but your output will definitely vary. Any solar panel salesman should be able to tell you what sun zone you are in.

And yes, it's easier to justify solar in Hawaii!

[DustyDisks]

Originally Posted by frquixote

I'm not quite sure where your numbers are off, but I have 28 225W panels from a well-known Japanese manufacturer (cells made in the USA!) that take up 380 square feet (35.28 sq meters) of roof space on my little (1172 sq ft) house and they generate on average 30 kWh/day, which is more than 850W/sq meter/day.

Having spent quite a bit of time studying the available solar panels before buying, I don't know of any that only generate 60W/sq meter/day ... that would be a 30W panel!!! I suspect you forgot to multiply the panel output by the number of hours it is actively generating power. Here in Hawaii we see an average of 5.8 hrs generating per day, but your output will definitely vary. Any solar panel salesman should be able to tell you what sun zone you are in.

And yes, it's easier to justify solar in Hawaii!

frquixote
Kapolei, HI

Agree, the numbers and method are off.

[Ken Maltby]

Originally Posted by frquixote

I'm not quite sure where your numbers are off, but I have 28 225W panels from a well-known Japanese manufacturer (cells made in the USA!) that take up 380 square feet (35.28 sq meters) of roof space on my little (1172 sq ft) house and they generate on average 30 kWh/day, which is more than 850W/sq meter/day.

Having spent quite a bit of time studying the available solar panels before buying, I don't know of any that only generate 60W/sq meter/day ... that would be a 30W panel!!! I suspect you forgot to multiply the panel output by the number of hours it is actively generating power. Here in Hawaii we see an average of 5.8 hrs generating per day, but your output will definitely vary. Any solar panel salesman should be able to tell you what sun zone you are in.

And yes, it's easier to justify solar in Hawaii!

I could have some of it wrong as most of the data comes from sites that
promote PV systems.


So if you were able to get the full 7kwh of the net sunlight energy over a
day per square meter for your 35.28 sq meters = 246.96 kwh, but that would
be with 100% conversion efficiency. (And they must be assuming a 7hr day
at 1kW.)

If you could collect at the Peak incident energy at noon on a perpendicular
surface: 1 kW/sq.m, for your 5.8 hrs from 35.28 sq meters (5.8hrs x 35.28
sq.m x 1kW = 204.624 kWh per day, but that is not possible.)

I am assuming that your panels can't collect more solar energy than the sun
puts onto a sq. meter of the surface. Those I see in the 250W range have
a surface area close to a sq. meter. At their max output it takes four panels
to convert 1/4 of the solar hitting their surface into 1kW. 28/4=7kW.
7kW x 5.8hrs = 40.6kWh per day, if you could get the max output of all the
panels for the whole 5.8hrs.

Luck;
Ken

[MikeB1972]

I think you divided by 24 (P[pv]=E[pv]/24) for an average per hour and then used this value for the full day (Probably trying to work an average kWh figure without acounting for the fact that you would get 24 of them in a day).

If you drop that out the figures more or less match up with the actuals from frquixote.

0.8-1.4kW per square meter per day by ken's maths
1kW per square meter per day by frquixote solar panels

[ProDigit]

back to original topic, no I would not do it.
I would paste the solar panels on the back, and wire them directly to the USB port.
That way you don't have to open the device, and can unplug the panels at any given time!
I'd also install one large panel covering the whole back, not just the top.
Chances are you will cover at least one panel with the hand, and from the light they are receiving (usually reflected sunlight from the floor) it will need a more powerful panel!
It is a nice hack though that I am considering on doing, but through the USB port, not through the back plate!

I think this solar panels will be more suited for the job (seeing that they never will receive full sunlight):
1- 6V 200mA
2- 5V 130mA

[Pinecone]

Originally Posted by frquixote

I'm not quite sure where your numbers are off, but I have 28 225W panels from a well-known Japanese manufacturer (cells made in the USA!) that take up 380 square feet (35.28 sq meters) of roof space on my little (1172 sq ft) house and they generate on average 30 kWh/day, which is more than 850W/sq meter/day.

Having spent quite a bit of time studying the available solar panels before buying, I don't know of any that only generate 60W/sq meter/day ... that would be a 30W panel!!! I suspect you forgot to multiply the panel output by the number of hours it is actively generating power. Here in Hawaii we see an average of 5.8 hrs generating per day, but your output will definitely vary. Any solar panel salesman should be able to tell you what sun zone you are in.

And yes, it's easier to justify solar in Hawaii!

And how much did those solar panels cost?

What is their life expectancy?

[DustyDisks]

Originally Posted by Pinecone

And how much did those solar panels cost?

What is their life expectancy?

You can google around to find what a system like his costs, the panels are not the only cost , you also need a controller/inverter and a battery bank. And the more load (ac/dc powered appliances, air conditioners) and such, the bigger the system needed.

The life of a well made and maintained solar panel can exceed 30 + years.

Trying too get back on track, solar powered e-readers and such for direct operation or more likely recharging use. Is a very good option for those that live in sunny areas of the world. And using the right size and type, one could even capture power from inside lighting for recharging/using your devices.

[ProDigit]

There's much research going on in solar panels.
First of all, scientists have found that nano coated carbon tubes will improve the efficiency of a solar panel by much!
There's plenty of carbon available in this world, only the process of applying it to the panel might be not too easy.

Second, there have been discoveries done on using plain white paper, with a carbon layer as background for solar panels. This is also based on nano technology, and still in the early stages, but it would cut back cost of the panels by at least 60%, as well as make it more environment friendly!

Third, there is research being done to improve solar panel efficiency. By increasing the density of the grid (the electric nerve system in the panel) they can increase performance, at only a slightly higher cost.

Fourth, also research being done to make solar panel backs flexible, so that instead of using glass, they can use plastic as the base for the panels.THat would make it possible, to reduce the thickness and weight of the panels, as well as make them flexible for say curved surfaces!
The only con to this research is that the efficiency of the panel drops; but then again, so does the price, and considerably!

[carpetmojo]

I think the solar power-powered eraeder will never happen, it's ridiculous.

It's obvious to that it'll be a wind-powered one that'll crack the market.

Be a bit tricky in a lift or the subway, mind.

But if you wore skates, or cycled - now there's a cross-over bonus.......

[frquixote]

Originally Posted by Pinecone

And how much did those solar panels cost?

What is their life expectancy?

After state and federal tax credits, about $17.5K. Ignoring the time value of money and escalating electricity rates ($0.25/kilowatt last year at this time and $0.35/kilowatt now), the payback period is about 4.5 years. Would be about 12 years without the tax credits.

Life expectancy: About 25-30 years with output warranted for 20 years.

[Ken Maltby]

http://www.cpsenergy.com/

HI has some of the remote location factors and especially good solar conditions, given
the posts here. HI = $0.35/kilowatt TX = $0.09 per kilowatt hour.

Luck;
Ken

[ProDigit]

The only bad thing not calculated within purchasing solar panels is what happens if it gets stolen or breaks!

[ApK]

Originally Posted by ProDigit

The only bad thing not calculated within purchasing solar panels is what happens if it gets stolen or breaks!

Warranty and insurance, like just about everything.