Charging with Solar, Turbine

Can I charge cellular phones, laptops or power tools with solar power or a wind turbine? Absolutely. This is an exciting way to step outside our four walls and use renewable energy. The sun provides peak energy of about 1,000 watts per square meter (93W/sq.ft.). From that source, a solar panel will generate roughly 130W/m2 (12W/sq.ft.). Photovoltaic systems are 10 to 20 percent efficient.

A solar cell produces an open circuit voltage of 0.5–0.65V. Like batteries, solar cells can be connected in series and parallel to achieve higher voltages and load currents (Reference: Series and Parallel Battery Connections article).
 
Solar energy can be expensive. It costs $8 to $10 in materials to generate one watt. Producing 50W from solar panels to operate a laptop continuously, or charge a 50Wh battery in two hours will cost $400 to $500. A system to charge a larger 12V, 150Wh, lead acid battery for a cottage will cost between $1,200 and $1,500. Arguably, you can use smaller solar panels and charge the battery longer. This, however, may not be enough to keep your laptop and other appliances running all day. For example, a 20-watt solar charger costs between $200 and $250 and the output on an overcast day may not be sufficient for continuous operation.

In addition to the solar panels, you also need an inverter and charge controller. It’s best to get a combined unit and most charge 12-volt lead acid batteries. An advanced charge controller takes any energy, even if very low, and converts it by boosting and decreasing the voltage to the desired level. The advanced controller also prevents overloading the source if the output is weak. A device that offers the three functions of boosting and lowering of voltage, as well as adjusting the load to the best power factor is complex and would be out of price-range for casual users. Most commercial charger controllers require a high enough voltage to allow down-regulation. Boosting and adjusting to the power bandwidth of a source is seldom done. If a dark cloud covers the sun, most charge controllers simply shut down.

To charge a laptop or cell phone, you need an inverter that transforms the DC voltage from the solar panel to the correct supply voltage. Do not connect the raw voltage from a solar panel or wind turbine directly to the device. Over-voltage on a high-output day could overload the system. If the device has no DC input for charging, boost the DC source with an inverter to 115AC or 230VAC, and then use a regular charger. Observe the input voltage of the inverter. You may need additional DC regulation if the voltage swing from the source is too large.
 

A solar-powered cottage would be the ultimate, however, a photovoltaic system costs about $20,000. To produce one kW of power, you would need 10 to 12 large panels, which would occupy about 33 square meters (355 square feet). According to Solarbuzz, the cost to generate one kWh on a photovoltaic system is about $0.35. This compares to about $0.10 for grid electricity. Charging with solar panels in the winter is a challenge. The panels provide low power and batteries charge poorly at freezing temperatures. Li-ion should not be charged below 0ºC (32ºF). (Reference: Charging at High and Low Temperatures article)
 
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Comments

On February 8, 2011 at 12:30pm
P_A_P_Y wrote:

You mentionned “Solar energy can be expensive. It costs $8 to $10 in materials to generate one watt. ”
I agree but after the material is yours…. and can produce many more watt…
For instance I bought a 1 W solar recharger for $30.00 Witch is 3 times more than you mentionned (it would of been cheaper to built one ) but i’m still using it after 1 year  

I do not know the lifetime of that small solar pannel but it might last long enough to bring down the ratio $ vs Watt you are mentionning ..

On February 9, 2011 at 3:38am
PV-Solar wrote:

About the cost of (electrical-) energy: It doen not matter what the cost is, it does matter what the cost (financial and non-financial) of an alternative is. e.g. calculate the cost of the energy in the battery of your wrist watch! and still nobody would consider to use a mains charger with extension cable. (but PV solar is a good alternative)
Depending on the cost of the energy, it makes sense to spent some more money on system efficiency. Inverting the low voltage dc from a solar module to 120/230V 50/60 Hz and bringing it down to the 15V dc required for your laptop is waising money. Unfortunately there are no manufacturers yet to solve this in a more energy efficient way. (but I am working on it)
Charging batteries with pv solar requires a totally different approach compared to mains charging. Main reason is that the primary energy, the sun, is not continuously available and when, sometimes not in the required amount (cloudy days) A charging technique that collects all the energy when available, even with some damaging effect to the battery has preference over an empty battery with damage by e.g. sulphation for lead acid.
With the lowering cost and increasing efficiency of PV modules, the number of applications where solar energy is the cheapest solution is growing. The concepts these systems are based on today will not longer be the optimum. Redesign will be necessary.

On February 15, 2011 at 2:50am
discussion forums wrote:

Thanks for the effort you took to expand upon this post. I look forward to future posts.

On May 13, 2011 at 4:23pm
Tyler Sproule wrote:

You wrote: “Producing 50W from solar panels to operate a laptop continuously, or charge a 50Wh battery in two hours will cost $400 to $500.”

How do you go about calculating how long it will take for a battery to charge up given the system?

On May 13, 2011 at 4:31pm
Pierre Legault wrote:

There are little calculators for that ,
The time to charge depends of the battery capacity mAh, and the charge rate current mAh

here is an on line calculator
http://www.csgnetwork.com/batterychgcalc.html

On May 24, 2011 at 5:23pm
Don Rose wrote:

Hi,

The costs per watt of solar panels have dropped a lot. It is quite possible to find quality panels for under $2.00 per watt.

Here is a website that retails to the public:

http://sunelec.com/

Thanks for all the information you have provided.

On September 3, 2011 at 9:39am
Subramanian, D.V wrote:

My LENZ II vertical axis wind turbine is located in a low wind area and works in gusty winds . Its output (D.C) varies from 2 Volts to 20 volts.in lulls rising to gusty winds. most of the time it is around 9 - 10 volts. How do I charge a 12 Volt battery?
Can you give me a schematic for an advanced charge controller which you say boosts low voltage and reduces high voltage of the source ?

On September 3, 2011 at 9:50am
Subramanian, D.V wrote:

My LENZ II vertical axis wind turbine is located in a low wind area and works in gusty winds . Its output (D.C) varies from 2 Volts to 20 volts.in lulls rising to gusty winds. most of the time it is around 9 - 10 volts. How do I charge a 12 Volt battery?
Can you give me a schematic for an advanced charge controller which you say boosts low voltage and reduces high voltage of the source ?

On September 23, 2011 at 1:28pm
abdulazeez wrote:

thanks

On November 22, 2011 at 10:44pm
Scott Brooks wrote:

You estimates may be out of date but if subsidies disappear there’s no telling how that will effect costs. people neglect to think about the costs of mining and manufacturing for all this good solar stuff. That takes real power both oil and either coal or nuclear. Then there’s availability of materials, if solar was massed produced for the masses the material sources could dry up or be peaked out.

http://www.mrsolar.com/page/MSOS/PROD/remote/RPS-1800

http://www.batteriesinaflash.com/deep-cycle-lead-acid/6v/trojan-t-605-6v-210ah-flooded-lead-acid-gc2-deep-cycle-battery

And to be competitive with fossil or nuclear it has to be manufactured in places like China sending all those alleged green jobs overseas.

On December 18, 2011 at 2:01am
amjum wrote:

So far I dont think you can replace all your electric consumption wih solar panels aloine, http://www.southlondon-roofing.co.uk

On February 19, 2012 at 9:09am
Dick Triller wrote:

If you don’t want your children to suffer from asthma, cardiovascular illnesses and or perpetuate unknown illnesses related to polluted air, then the sacrifices made whether in money or effort toward cleaner environment is a must. Whatever it costs to reduce the carbon emissions is worth it. Find a way. Iceland has three times as much energy than they can use, due to geothermal and hydro available resources. They can use their surplus energy to make hydrogen fuel, which can power many green production facilities and operations. We need to start using coal and nuclear more responsibly. That mean perfecting nuclear before we proliferate. Solar is a great idea. Send your kids to school and get them interested in finding solutions for our insatiable appetite for energy. Wind and Solar cost as much as the coke and smoke your kids will be spending their hard earned pay on, if they don’t stay busy. Education, sports, arts and music will inspire creativity and maybe even spawn a Newton or Einstein solution to our energy needs. Creativity and conservation is a great idea. I like solar, I like wind and I love waves. Surf’s up!