Your Questions About Solar Panel Efficiency

Jenny asks…

Where can I get solar panels(not online) for this stupid science project?

I have to do a stupid science project(I HATE SCIENCE PROJECTS!) And I was thinking i could compare the efficiency of a solar oven using plain sun rays and a solar oven using a solar panel. Where can i get some solar panels in Kentucky? I don't want to do online/
I DONT WANT TO BUY THE ONLINE!!

ssadmin answers:

Solar panel to support an oven is big and very expensive (over few hundred dollars). Perhaps you might see some mobil road sign that runs with two big solar panels….and perhaps you could borrow it and return it after finish your project (ask for permission first).

Nancy asks…

How could i estimate the area of a photovoltaic panel for solar powered garden light?

known info:
At night the LED is illuminated, drawing a current of 25 mA
battery supplies 1.2v
runs for 12 hours at night.
take standard air mass to be AM 1.5 1000 W m^2
No information on panel size,
rough estimate: 5 hours good sunlight per day

Would i need to calculate the daily energy requirement of the LED first?

I've calculated the power level to drive the LED is 25 mA x 1.2v = 30 mW
so 30mW x 12hours = 360 mWh = 0.36e-3 Wh

behond this I'm not sure!!!

solar panels power output in a day = efficiency (w/m^2) x area (m^2) x duration of sunlight (s) ws ???

ssadmin answers:

Energy_led = Energy_pvmodule

Energy_led = t_night*I*V

Energy_pvmodule = Pdc_stc * t_peaksun_eqiv

Solve for Pdc_stc (power direct current at standard test conditions):
Pdc_stc = t_night*I*V/t_peaksun_eqiv

Data:
t_night = 12 hours
t_peaksun_eqiv = 5 hrs
I = 0.025 Amps
V = 1.2 Volts

Result:
Pdc_stc = 0.072 Wdc

This is the minimum nameplate size at standard test conditions that your PV module can be.

In reality, it will need to be much more…because you will need to compensate for battery charging and discharging loss…as well as the inefficiency of the MPPT charge controller.

To figure the area associated with it, you need to know the efficiency of the PV module…call it eta.

Typically, this ranges from 10% for laminates to 22% for some of the best crystalline designs.

Let's accept eta = 15%.

We equate DC peak power to incident solar radiation (J) multiplied by efficiency (eta) multiplied by module area (A):
Pdc_stc = J*A*eta

Solve for A:
A = Pdc_stc/(J*eta)

J = 1000 W/m^2
eta = 0.15
Pdc_stc = 0.072 Wdc

Result:
A = 0.00048 m^2
aka
A = 4.8 cm^2

Mandy asks…

Did you read about the 100% efficient Solar Panel?

I read that researchers found a new mixture that reaches 100% efficiency.

http://technutnews.com/2008/11/26/new-solar-cell-material-achieves-almost-100-efficiency-could-solve-world-wide-energy-problems/

How far do you think that this technology is from being used?
Is there a chance of creating more pollution or not being recycleable?

ssadmin answers:

Your article states, “…This combination of materials also utilizes the entire visible spectrum of light energy, translating into a theoretical potential of almost 100% efficiency…”

Current solar cells only use a portion of the visible spectrum, but none utilize 100% of ANY portion of the spectrum. It appears to be a pretty big leap to go from a full-spectrum panel to a 100% efficient full-spectrum panel.

One curious thing to consider, a 100% efficient panel would appear pitch black, but never get warmed in the sun.

Sandy asks…

What is more important to control Global warming Solar Panels or trees?

If everyone put solar panels on their roofs they would have to remove all the trees near their homes that would shade those panels for the panels to work at maximum efficiency.
bruce and how would enforce such a law? China has a one child law enforced by mandatory abortion.
Jack Higher taxes on who? Everybody?

ssadmin answers:

Since global warming is a fantasy, the answer is neither, but plant a bunch of trees anyway because they are nice to look at unlike solar panels and wind turbines, and birds can live in trees as to being butchered alive by wind turbines

Laura asks…

Solar Panel, battery and Motor?

Hi, I am student training inside a company right now.
This is my project.
I need to use DC motor to run an aerator, so the battery will gain the electricity from solar panel.
I have battery have enough electricity to ensure aerator can run 8 hours in daytime, and still left some to operate during night time.
DC motor 0.75kw to 1.5kw , single phase
I choose 5kw solar panel, which mean will provide 5000watts per hour.
battery used 65AH,12V
for motor ,if P=VI
750watt = 240V( assume single phase) x I
then,I= 3.125A , means consume 3.125A /hour
so, 5000watts from solar panel if operated 8 hours i need 5kwx8=40kw.
from solar panel to battery, assume 15% losses(0.85 efficiency), 40kwx0.85=34kw
so from battery we have 34kw electricity.
I am using 65Ah battert, motor consume 3.125A, 65/3.125= 20 hours.
means I can operated 8hours in day time and can backup for night time?
I dono this assumption correct or not. please give me comments. Thanks.

ssadmin answers:

You need to reconcile your numbers.

Your battery delivers current at 12 volts. Your motor consumes current at 240 volts. You would either need 20 batteries wired in series or your single battery would need to deliver well in excess of 62 amps into a suitable DC-DC converter to power your 0.75 kW motor.

A 65A 12V battery will store approximately 750 Wh (0.75 kWh) of energy. I don't know how you are going to get it to hold 34 kWh. Even 20 such batteries would only store about 15 kWh under optimum conditions.

Unless you expect your solar panels to only deliver a small fraction of their rated capacity during daylight hours, 5000 watts is oversized.

Don

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