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Photovoltaic Solar Power System

Renee Said:

What do they mean by "magnify" sunlight?

We Answered:

A better word would be "concentrate". "Magnify" seems to suggest getting something for nothing. I agree that the article doesn't adequately explain the physics of the product. However, it's true that photovoltaic efficiency can be increased by applying more intense light (see ref. 1). If they can get 37%, that's pretty impressive. To me (who's been around the block a few times) it's ironic that we're going back to the first transistor material, germanium, with all its temperature problems.
Incidentally, cost per kilowatt-hour is a very pliable number. It's based on size, efficiency, geographical region (insolation, cloudiness), and cost vs. expected lifetime. See ref. 2. It's much easier to predict 7 cents/kwh than to reach it.
I'd suggest the first answerer consider the alternatives. Wind power is expensive because wind energy isn't well concentrated (consider what a low-power window fan can put out) and winds can be unreliable, just like sunlight. The potential for producing large areas of photovoltaic film at reasonable cost is far greater than for large areas of turbines. Billions have been spent on bio-ethanol (taking food sources out of production and costing excessive amounts of petro-energy); the hydrogen scam (it's free! it's in the water we drink!); and schemes for stashing CO2 in strange forms and places. We are in a desperate situation and can't afford not to work on solar. Also, concentration of sunlight is not "required" to generate electricity, it's just more efficient.

Clinton Said:

whats a good name for a small solar company?

We Answered:

secure solar solutions
sensable solar solutions
asured solar co.
please tell me which one you chooses if any

Audrey Said:

Can you help me my AP enviromental science problems?

We Answered:

You need to do your home work! This is very important stuff to learn about. I will however lend you a hand.

1) harnessing solar energy is called photovoltaics
2) Energy demand is highest in the evening when most people are getting home and turning on lights, but looking at the question it says night so probably durring the day when most people are working and businesses are open. D and E seem to be off topic so choose from B or C
3) The only option here that has NO enviromental negative impact is conservation. Even tidal energy effects the eco system of shelf dwelling sea life. Converting biomass requires biomass so thats to say making energy from garbage, and that has a direct impact. Geothermal energy is not abundant enough in natural occuorances and if it was building a power plant at the site would effect the wild life that called that thermal vent home.
4) . It would take alot of enrgy to ionize water into a flamable gas. I did alot of research on this involving hydrogen genorator fuel cells in cars. BTW its all BULL$!t You cannot power a car with electrolosys or gain efficeincy by suplimenting it into your fuel. E is deffinately a correct answer double check what the law of thermodynamics actually states however.
5)The water around the rods keeps them cool and prevents melt down. It also serves to generate the steam that powers the turbine depending on the model of the generator they are using
6) A chain reaction is a reaction that has a cascading effect. One reaction causing another reaction and so on. Look up the exact definition in a dictionary. Put into context with the nuclear reaciton question prior and mention something about critical mass, the point at wich nuclear isotopes reach a mass that causes them to implode and detonate just like a nuclear bomb.

Nancy Said:

can you help me these AP enviromental science problems?? HELP ME ASAP?

We Answered:

Electricity production from solar power requires photovoltaic cells.

The possible answers to #2 don't make much sense to me. The daily demand for electricity has two peaks. One during the day when businesses are on day shift using lots of power, than another smaller peak when people go home and cook dinner in the evening. In the middle of the night power demand is the least. Hydrogen can be produced from a variety of sources including coal, natural gas, solar, and nuclear. Currently, the easiest, least power intensive way is to strip hydrogen from natural gas (methane), however, this requires energy to do and burning the hydrogen doesn't recover that energy. Also, carbon dioxide is still created. If you just split water using electrolysis, that requires massive amounts of electricity which is still primarily produced by coal in the U.S.

I think the answer they are looking for in #3 is conservation, but that is a myth. When you force people to conserve something, that makes demand go down. When demand goes down, that thing gets cheaper. When it gets cheaper more people buy it. The U.S. has been on a conservation kick since the 1970s, yet we continue to use more and more electricity. Our refrigerators are much more efficient, but now our kitchens have added microwaves, convection ovens, stick blenders, and a host of other electrical gadgets that have resulted in the total power use to go up over time.

Electrolysis requires more energy than it produces, by about 4 to 1.

The water that surrounds the fuel in a reactor slows down neutrons to moderate the chain reaction and removes heat. Of course, it's not "waste heat" because it is going to the turbine to generate electricity.

A chain reaction refers to the nuclear fissions that occur to U-235 atoms within a reactor core. When a U-235 atom fissions, it releases two or three neutrons. Those neutrons fly off at one tenth of the speed of light. If one of those neutrons generates another fission event from a U-235 atom, the reaction is a self sustaining chain reaction. If more than 1 of those neutrons generates additional fission events, the reaction is a super critical out of control reaction. If less than 1 of those neutrons generates another fission event, the reaction is subcritical and the chain reactions stops. An operating nuclear reactor is a delicate balance to maintain that ratio of neutrons generated to fission events as close to 1.00000 as possible.

Constance Said:

Inverse square law!?

We Answered:

A. Each solar cell has an area Ac = 10 cm^2 and there are N=20,000 cells. The total area is:

At = Ac*N = 200,000 cm^2 = 200,000 *(10 cm^2)*(0.0001 m^2/cm^2) = 20 m^2

The sun puts out Es = 1.4 kW/m^2 so the total solar power on teh cells is

P =Es*At = 1.4 kW/m^2*20m^2 = 28 kW

The cells make 5kW of electrical power so efficiency is power oput/power in

Eff = power out/power in = 5kW/28kW = 17.86 %

B. The radiated energy spreads out over a sphere so teh irradiance or flux (Power/unit area) is just the power radiated over the area of the surface of teh sphere:

E = Prad/(4*pi*r^2) Where r = distance from the power source.

So for the probelm at hand Prad = 5kW and r = 3.6 x 10^4 km = 3.6x10^7 m and

E = 5x10^3 W/(4*pi*(3.6x10^7m)^2) = 3.07x10^-13 W/m^2

C. Now you are told that the total power is conecentrated over an area on the Earth's surface. Call that area A and

A = pi*(re)^2 = pi*(1000 km)^2 = pi*(1x10^6)^2 m^2

A = pi*10^12 m^2

Prad is still 5kW but now

E = Prad/A = 5kW/(pi*10^12 m^2) = 1.59x10^-9 W/m^2

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Yoga Meditation Retreat said:

I think the answer they are looking for in #3 is conservation, but that is a myth. When you force people to conserve something, that makes demand go down.

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