Solar Panel Technical

solar

om, amp, joules, volt, watt

What materials do I need?

1. Tempered glass
2. Slygard sealant over the cells.
3. Aluminium angle surround.
4. Plastic backing.
5. Silicone sealant all around.

The UL certification process takes time, and cost a lot of money. Be ready to pay a minimum of $700+ for them to come out and certify your project.
third, be ready to pay them again to come back if you don't have everything ready for them on the first try. It helps to have an 'in', someone who has worked with UL techs and can recommend you as knowing what you're doing. UL will certify 'one off' projects or, for more $$$$ and time, a manufacturing process. Every test required several units and each was destroyed with destructive testing. It cost us several thousand dollars for the certification, not to mention burning up thousands of dollars of product. This means that your DIY panel may be destroyed as part of the certification process. Be ready with receipts and manufacturer specs on every part involved, even glass.

The potential problem with a panel is the high current and heat generated - unlike what a homemade PC or car radio would have. A panel located 150mm (6 inches) off a roof is not far at all in the event of a short circuit. Or possible the wiring, batteries, ect… There are many things that can go wrong. If the Electrical Code is followed, quality listed materials suitable for the purpose, and proper workmanship executed then the risk are very small. Problem for DIY stuff, is the DIY's do not even know what questions to ask.

For DIY solar panels, we have to protect it against moisture, heat, cracks, rain, snow, hails, etc, so it need to be sturdy. Plastic and wood would warp, contract, expand and then let all kinds of moisture in.

How are you going to mount your DIY solar panels on your roof without damaging your roof?

Low iron glass at 4mm thick will allow about 3% more light through than float glass, so the difference can be overcome by adding a few extra cells and saving money.

if you get hail then tempered would be good, if not you can probably get away with non tempered glass, not sure of what you can get locally but thats the best option for glass and frames. Old shower doors and sliding doors are mostly tempered, or for non tempered glass look at regular aluminium framed windows, all these items have much better frames already than you can home make and save more time and money.

Using sylgard as you want to is a good idea, will seal it the best possible for the rainy weather if you completely encapsulate the cells. also backing material may not be required with sylgard , once they are mounted correctly should be little harm coming from the back, being open also allows to visually see all parts easy and allows the cells to cool better.

Yeah, I'm trying hard to stay away from plastic and wood. It would appear that metal and glass are what stands up to the elements.

I caution you that you can't always believe what an eBay seller is telling you. Most companies do not make Grade A cells to be sold individually. Those are usually the ones that didn't pass inspection and are then sold for a much lower value which is why they are very cheap to buy in quantity.

Also you mentioned that the cells were metal. Unless you have found a different source every one of the 6 x 6 cells I found being sold on eBay are either a Mono or Poly crystalline solar cell that is on some type of back-plate (may be metal or something else). The cells are still semiconductor material and will crack, fade and degrade over a period of time depending on how well they are mounted and protected from the elements.

I admire your decision to build your own solar panels but I think you need to understand some of the pitfalls of doing this. The panels (no matter how well you construct them) may still be made from below grade components. Also due to local and national codes (there to protect people from harming themselves or others) will not allow you to sell or install anything that can affect others. The UL listing is just one form of information to tell you that the manufacturer has gone to some length (and cost) to make sure their product is safe and reliable.

Sharp, BP, Sanyo, and Kyocera were mentioned in another thread.

How about:
Evergreen
Sun
Dupont Solar
Canadian Solar
NBsolar
SunAli
EPV Solar?
http://sunelec.com/
Sonali, Suntech & Jetion that are all less than $1 per watt.

Panels being made with alluminium frame, glass top, Sylgard 184 encapsulant, have nothing to burn. This of course leaves the wiring, and i think there is more potential for death or fire from shoddy wiring than from panels. See http://sun.anu.edu.au/files/Ketola08_silicones_for_pv_encapsulation.pdf. What burns is the material adjacent to the panel - a roof perhaps.

You just found the panels for $1/w or less. That is what you will pay to buy them. Shipping and installation along with inverters, cabling, racks, chargers, etc will increase your material costs. You can add your own DIY labor for free.

No one that I know here on this site ever said the Installed Cost was $1/w. Even you won't be able to get the job done for that low price unless someone gives it to you.

Civicsolar - seemingly cheaply priced…until you get to shipping at which point tack on about 30-50% of what the panels cost, blowing the $0.82/W price quoted on their site, next is Sonali…same story there…I'm awaiting two official quotes but they guesstimated the quotes to be similarly priced with shipping as civicsolar. I am researching, by way of actually calling and finding out what the prices are…and I'm still waiting to find these magical $1/W solar panels…

The problem really kicks into high gear, when you are stringing several panels into a 400v or so, array. Then the DIY insulation goes bad near a corner, or a bad solder joint gets flaky. The high voltage creates an arc, and it's all downhill from there.

400V array - that's quite a setup for DIY!!! There wouldn't be too many of those on a domestic roof. Surely this isn't DC before the inverter? Why would anyone want 400V DC

300 - 600V DC is dangerous stuff. I wouldn't expect to see too many DIY at this scale.

DC voltage at this level is deadly - worse than AC. DC current contracts the muscles (eg hand) so they hang on. With AC there's more chance of letting go. However, both are pretty nasty, and anything over 50V either way should be avoided.

Being hit with 600V DC would be devastating.

If you string a few together in series you end up with sometimes 20-50A running through questionable solder joints inside something that's already sometimes 200 degrees F inside due to the sunlight… it's a recipe for disaster.

Like joining aluminum wire to copper - done right it is OK while done wrong it is an invitation to disaster.

The main panel in my home is 380 volt 3 phase - I really don't tend to worry about voltage - I do take considerable care though. Anyone who has worked in industrial plants has probably been exposed to a safety culture where there are things you do and things you don't do.

Running undersized cables with doubtful connections in a hot roof space is high risk for fire.

You need to understand voltage drops and wire sizes, how heat effects things .. basics .. thats first .. then one needs a design that considers the factors involved in a solar panel, heat, exposure to elements, how do i seal it so heat can radiate out and moisture can be blocked, that wont break down and will 'hold' … plexiglass, wood, plastic are all things that dont work for a serious panel home build .. neither is a 200$ piece of glass cost effective .. neither is insulating the back of a panel and basically sealing the heat in conducive to performance .

Has the system suffered severe weather yet - eg hailstones. I used tempered glass to allow for this. It happens rarely, but only takes one instance to wipe out thousands of dollars worth of panels.

protective resin

I use 4mm tempered glass, to ensure they survive that once every 10 year heavy hail storm - make sure your glass can stand up to whatever nature throws at them. You say you have siliconed the cells to the glass. You now have to get slyguard to protect the cells from air attack. You have to make this flow under and over every cell, excluding all air. You may not find this so easy, particularly with silicone in the way. This is important if you want to get acceptable life. Note that if you try to push out air bubbles, you risk cracking a cell, and I've found out the hard way, it's a nightmare to solder in a replacement while the slyguard is setting.

Why did you connect all the cells in series? Your research should have told you that it's normal to connect 36 cells in series for each panel, to give 20V under full sunlight, and over 14V (enough to charge a battery) under reduced sunlight (eg - when the sun's at a low angle). You are better off having two panels, each of 36 cells, connected in parallel. This would give you double the power.

Slyguard

I have encased the ebay b grade cells in glass and silicone to charge just 6 AA batteries 3s2p to power a Cree led. Seems like the cells converted close to 15% of the sunlight, thus they only had slight cosmetic problems. The little 12 cell panel worked for years until it got stepped on…
However, I believe that there are certain kinds of silicone that does not go well chemically with solder, etc. Eventually, corrosion would have rendered it useless anyways.

Unless I had used the "right" kind of silicone to attach the cells (and solder) to the bottom glass pane.

For "real" panels, just buy 'em.
But for odd voltages, you can use tempered glass (bought at store supply, etc and size up 10% or more to make up for the high iron content). Had I done that, it would not have broken, but would have been larger, requiring more batteries and a brighter led. They have 10" and 14" square pieces with smooth edges (but I didn't order yet, thus don't know about shipping).

Sadly, I can't seem to find which is the best silicone for direct contact with solder and solar cells (but I know it's out there). In that case, should last decades! With a LiFePO4, a Cree XMl and just 8 cells (and perhaps, a overcharge protection chip designed for lifepo4, not li-ion), should have a solar yard light rivaling a normal 120v bulb for many years.

aluminum frame (I've talked with some local Aluminum framing companies and this seems reasonable), a plexiglass front, a stiff plastic backing for mounting the cells to and you use the metallic cells…what is going to fail? The plexiglass is more for protection of the cells from outright physical damage and assuming that everything is protected from direct abuse and insulated correctly/properly the system shouldnt fail.

I connected them thinking that the more connected they are the more power I could receive. Which I later found out that it wasn't the case. I found that sure my voltage goes up but my overall power is worse and they would not be able to be hooked up to a grid tie inverter because of the high dc voltage. I am currently going to try the 50 cell configuration to see if that works out the best. They also make a 72 cell panel which is why I thought in my mind the more cells per panel the better. I didn't find in my research that more cells hooked together does not necessarly mean more power. So I learned my lesson about that with only having to destroy 8 cells after taking them off.

I am not too excited about only getting 60W, I am actually disappointed because I should be getting 90w from the 50 cell panel (1.8 watts per cell times 50cells). I think I will be able to get this up by using better cells and having them installed better, we'll see. I'm excited to find out what the two 50 cell panels hooked in parrellel will do. If I find that it is much cheaper to build my own panels then i will proceed into finding out what my local electricity company requires to have for a grid tie system.

Overloaded wires and connections, and faulty connections, is a real fire risk.

You're not going to get electrocuted from panels at 20V, but once you get on the other side of an inverter, it's deadly. 20V will certainly start a fire with a few amps to support it. Try shorting a 12V car battery with some normal electrical cable if you want to see what I mean.

And used anodised alluminum for frame and low iron tempered glass.

Is there such a material that would change state / form and therefore cool down when under pressure or heat?

large grid tie inverters need 300-600VDC. Or to move power over longer distance, higher voltage is used

I'm all for home built, and learning how it works, but the stresses involved between the different thermal expansion rates of wood, plexiglas, PV cells, and the electrolysis that happens when moisture builds, the panels fail, sometimes silently, sometimes in fire.
See this thread:
http://www.solarpaneltalk.com/showthread.php?t=1083

I used solid framing, low iron glass, Dow 184 and tedlar backing.

Get some copper wire, good soldering iron, resin cored solder, and get some practice at it. It's not hard, but there's some technique and recognition of when it's working properly, which takes practice to learn. You don't want to be damaging cells, or getting poor joints.

There are some that have access to the exotic potting compounds, and if you have a vacuum bag system that's even better.

gear :
Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

How do re-chargeable batteries work?
What is an inverter?
What is a capacitor?
How do solar panel work?
How is electricity that is generated by solar panel stored and used?
How do we convert electricity from low current to high current?
What do I need? Do I need to buy battery (for storing the generated electricity)? What tool do I need?

DS1's solar cells are even more efficient than regular solar panels made for satellites because they use solar concentrators.

DS1's solar panels convert 22% of their available energy into electrical power. This may not sound very good, but it is much better than most solar panels. Most solar panels on people's houses, for example, are fairly inefficient. Less than 14% of the energy that reaches them will be converted to electricity. DS1's panels are so efficient, in fact, that unless the ion propulsion drive is running, DS1 is producing far more power than it needs.

Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV || || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

Together they charge two 6 volt 240ah golf cart style batteries for 12 volts. I have an inverter which converts the 12 volts battery DC into 120 volts AC so it can run common things.

The only thing it regularly powers is a back yard post light with two (working) 15w CFL bulbs.

In a nutshell, it takes more than a whole day of full sunshine to replace the power consumed by about 9 hours of CFL use. So my yard remains dark every other night to let my batteries recover with enough power from the panels. If the weather is bad my yard is dark for longer periods.

Peukert Law

One problem with plastic frames is that they may not be rigid enough to properly support the panel and the glass. The other problem, as you mentioned in that post, is that you be sure that they can take the temperature, and more important the UV exposure, without deteriorating.

You can actually get 12v CFLs now. I have 2 wired and set up in my back yard. Just one used car battery out of my brothers non-op car and a spring wound 60 minute timer switch to connect the circuit. they are amazingly bright and no converter to worry about. although there would probably be less loss using an inverted ac voltage than the low dc voltage, but hey it works.

How much power is lost by inverter?

I thought for a while my 12v 240ah deep cycle golf cart batteries might not be delivering their rated amperage.
I can burn a couple 120v 15w CFL's outside on a back yard lamp post overnight (About 9hrs) through my inverter and it takes two sunny days for my panels delivering 6.8ah to replace what the inverter + the CFL's consume.

Using a killa-watt meter, the two lamps on the post consume only 0.42ah @120v.

To test the batteries I connected a single 50W 12v incandescent bulb directly on my batteries. The lamp drew about 4ah tested on my meter.

I started with a full battery @ 12.76V.
I left the single bulb on for 9hrs
The battery tested 12.27v afterward.
(The battery tested unloaded after "resting" unloaded for several hours)

Hmm. This seems to me what I'd expect from my batteries, and is about what I was getting using the two CFL's and inverter.

So why do the CFL's drain about the same as wasteful incandescent?

One reason I figure is inverter loss.

For example I calculate my inverter loss to be 12.6% under the CFL load.
My CFL's draw 0.42ah but the ah draw between my inverter and battery is 3.35ah. Wow, what a difference between inverter input and output. It's close to the incandescent draw!

I am considering buying some 12v CFL's to avoid the loss. Two bulbs would consume around 2.2ah which is about 1ah less than the 120v ones through the inverter.

It may be a good consideration.
When my project is all done I hope to end up with two yard posts containing 3 bulbs each, and maybe two more single bulbs one on the shed and another on the remote car port.
That would be about 18ah consumption using 12v or about 27ah with 120v CFL's per hour.

In other words,
162ah consumption using 12v for 9hrs of night lighting
243ah consumption using 120v for the same duty.

Choosing between 162ah vs 243ah should be a simple choice, but I know that DC and wire impedance may be an issue with a 12v system.

The first yard post is about 150 feet from the batteries, second post on the string about 200 feet from the batteries, the single shed CFL is around 250 feet from the batteries and the final light under the port is around 300 feet.

For anyone familiar with my project, you'll know (and I know) my current solar project won't support that kind of consumption. But I hope to eventually expand to 8 panels delivering about 60ah for maybe 240-300ah of power on a good day. I also plan to expand my battery capacity to a total of 720ah, for a practical usage capacity of 360ah.
I realize the lights may not come on every night.

I hope I didn't make this post too confusing. That is one thing I'm very good at. If this is a dumb plan I know you will tell me.

You are missing something very important which no DIY knows about unless they have an electrical background. You applying DC principle to an AC circuit. It will not work.

You are not even reading your Kill-A-Watt meter correctly. You are looking at watts which is DC. You need to be looking at the Volt-Amps and power factor, the wattage is meaningless without the Power Factor.

So let's take a example your meter said 50.4 watts right? But what is the power factor? For inexpensive CFL my guess is about .6 PF. So with a .6 PF the Volt-Amps = 50.4 / .6 = 84 VA.

Now to calculate the load on the batteries we need to know the inverter efficiency. Lets say at this power level it is 90%. so the load on the batteries will be 50.4 / .6 / .9 = 94 watts. So when you were thinking all I had was 30 watts of CFL, you actually have a 94 watt load. The system uses 3 times more power than you thought. Surprise.

FWIW the wattage listed on the CFL is the tube wattage and does not include the ballast wattage. That is why your meter read 50 watts instead of 30 watts. However even with the ballast power a CFL is far more efficient than incandescent lamps.

Also, with a non-sine inverter, the ballast will burn more, and the inverter has roughly 20% loss too. A modern, efficient inverter like the Morningstar suresine, may give better results than a Kragen Auto $28 inverter.

Straight 12V , you will have a lot of wire loss.

Is there a case against CLF when the meter is not net metering?

I mean if the CLF has a power factor of .5, and for simplicity assume that all other things have power factor of 1, and the meter is the newer kind that won't spin backward. Will the CLF be charged double the power it actually uses by the utility company?

The power company has to supply more power than it can bill for I believe.

In residential settings the problem with power factor is on the utility side as you are billed for kWh only.

But Kwh is still read from the meter. So it's all boil down to how the meter reads the power consumption.

Also, my understanding is that the utility don't really need to generate the extra volt-amperes caused by power factor being less than 1. It just need to have capacitors that turn them back into phase.

You provided a most valuable calculation formula and I did not understand PF.

If I plug my K-W meter into a normal 120v outlet then one single 15w CFL into it my PF reads 0.63. The VA reads 24. If I understand this calculation correctly assuming 90% inverter efficiency:

It's watts divided by PF divided by inverter efficiency equals battery load.
Is that the correct fomula?

The single 15w CFL bulb in this calculatoin would be 15(W)/.63(PF)/.9 (Inverter loss)= 26.5ah battery load.

If that is correct, running that single CFL on the inverter for 9hrs would consume 238.5ah. Wow! My current battery is rated 240ah. No wonder the SOC is only about half after one 9 hour night on my post lamp - and my panels take two good sunny days to recover it.

Can anyone guestimate how long a 12v power line can be before prohibitive losses occur?

I'm glad I'm asking these questions and people are willing to be helpful.

I think how much energy CFL waste in the form of reactive power depends on how the inverter handle it. If the inverter can store the reactive power and feed it back to the CFL, it may not waste that much energy.

Utilities cannot charge customers for VAR,s only watts. It is commercial and industrial customers who have to pay for VAR's + Watts. Residential PF does not add up to a hill of beans.

My clock currently runs off 120v but like most every small appliance uses an internal step down transformer to drop the voltage to low levels. It would take me a very short time to cheaply modify it for low voltage low current DC.

There are a lot of DIY charge controller circuits I'd like to experiment with.

How much power can a solar panel produce?

I have 36 1.8W 3.6Amp- 3"x 6" cells that I plan to run 3 rows of 12. How can I tell how many watts and volts this panel will expend? and what can I do with this amount of power?

Power is simple 36 cells x 1.8 watts = 64.8 watts in theory. You will never see that much power out of it. As for the voltage your only option is to wire them in series to make an 18 Vmp panel at roughly 3.6 amps so again the power = voltage x current = 18 volts x 3.6 amps = 64.8 watts in theory.

What can you run with a 64 watt panel?

Not very much of anything useful. Light Bulb, yes say a 40 watt bulb for about 3 hours per day assuming you had the proper sized battery for it. Computer and TV is out of the question. Maybe a Netbook for a few hours per day. You won't be able to run much with your single panel.

What do I have to worry about when building my own solar panels?

  • I wouldn't worry too much about the Plexiglas turning cloudy on you. Most likely water will penetrate causing the panel to fail long before the Plexiglas turns cloudy and causes it to fail.
  • Things are OK as long as you keep it outside the house like a detached tool shed. The problem comes when you cross the line into your home and integrate into your premises wiring (house wiring). Once you cross that line everything by law has to be UL certified. Anything you make cannot be UL certified. If you ignored the laws and something were to happen like burning down your home or someone getting hurt, you rare fully liable and no insurance will pay any claims. I guarantee you cannot connect for a grid tied system because that takes permits and pass inspections which anything DIY will not fly.

Do the PV frames need to be vented for passive cooling or can they be sealed airtight?

I plan to use treated marine grade plywood for the back, a bordering frame and center member out of more treated wood all painted white. Silicone caulking everywhere, a plexiglass face, more sealer, aluminum tape around the border edge, Sealing it again with UV resistant polyurethane covering everything except the acrylic plexiglass. Maybe put an aluminum L channel around the edge to finish. So you see it would be almost impossible to add a vent once finished.

If you are going to use plywood, understand you will never be able to seal it and use enough paint to make it water vapor tight. May as well plan for some venting along the bottom and top edges to keep the condensation down. Clean the inside glass absolutely spotless, wipe down with rubbing alcohol, and the same with the front side of the PV cells and their edges. Moisture gets in there and causes leakage currents to flow (too small to measure, but enough to start electrolysis happening, and as that removes the front surface metal, the cells stop working.) Paint the inside and let it bake in the sun for a few days, so the paint outgassing does not collect on the inside glass or the PV cells.

What type of battery?

We plan to make 8 panels in all, each should deliver around 65W for a total of around 500W. We hope to power some small appliances (Low voltage clocks, fans etc) lights etc. I've taken the insurance consideration Sunking mentioned seriously and will stay out of the house wiring, although I haven't yet worked out my solar power distribution method. Like everyone I am looking for lowest cost. I know I'm looking for a deep cycle battery. Are these the same as a marine deep cycle battery? I've found some within my project budget online, however their RC value isn't usually posted on the web.

Batteries.. 6V golf cart batteries are a good starter set, get 2, place in series to get a 12V system. They generally are 200ah for the small ones. You will need a charge controller and need to add water (distilled only) to the batteries on a monthly basis.

Does a professionally installed grid-tie system add to a home's resale value?

Any "permitted and inspected" systems you add to the house, add to the value. PV systems, with a design life of +25 years for the panels, will add a significant portion of their cost, to the value. I'd guess 80% of what you install.

What maintenance do I have to do if I have a professionally installed solar panel?

I don't know yet. Need research.

Do solar panels wear out?

Solar panels are very hardy. Compared to alternative power sources, they wear out very slowly. Their effectiveness decreases around 1 to 2 percent a year. This means after a five year mission (boldly going where no probe has gone before), the solar panels will still be making more than 90% of what they made at the beginning of the mission (as long as they haven't gotten farther away from the Sun).

How do solar concentrators work?

A solar concentrator uses lenses, called Fresnel lenses, which take a large area of sunlight and direct it towards a specific spot by bending the rays of light and focusing them. Some people use the same principle when they use a magnifying lens to focus the Sun's rays on a pile of kindling or paper to start fires. Fresnel lenses are shaped like a dart board, with concentric rings of prisms around a lens that's a magnifying glass. All of these features let them focus scattered light from the Sun into a tight beam. Solar concentrators put one of these lenses on top of every solar cell. This makes much more focused light come to each solar cell, making the cells vastly more efficient. Concentrators work best when there is a single source of light and the concentrator can be pointed right at it. The solar concentrators also have the advantage that the solar cells can be spaced farther apart since light can be focused on each cell. This means fewer solar cells need to be made and the panels cost less to construct. Fresnel lenses have been around since Augustin Jean Fresnel invented them in 1822. Theaters use them for spotlights and lighthouses use them to make their lights visible at greater distances.

How do solar panels convert the Sun's energy into electricity?

The solar panels are made of solar cells. A cell is a small disk of a semiconductor like silicon. They are attached by wire to a circuit. As light strikes the semiconductor, light is converted into electricity that flows through the circuit. As soon as the light is removed, the solar cell stops producing power. The energy from the light excite the electrons in these semiconductor materials allowing the electrons to move …

How do batteries work?

Electricity, as you probably already know, is the flow of electrons through a conductive path like a wire. This path is called a circuit. Batteries have three parts, an anode (-), a cathode (+), and the electrolyte. The cathode and anode (the positive and negative sides at either end of a traditional battery) are hooked up to an electrical circuit. The chemical reactions in the battery causes a build up of electrons at the anode. This results in an electrical difference between the anode and the cathode. You can think of this difference as an unstable build-up of the electrons. The electrons wants to rearrange themselves to get rid of this difference. But they do this in a certain way. Electrons repel each other and try to go to a place with fewer electrons.

In a battery, the only place to go is to the cathode. But, the electrolyte keeps the electrons from going straight from the anode to the cathode within the battery. When the circuit is closed (a wire connects the cathode and the anode) the electrons will be able to get to the cathode. In the picture above, the electrons go through the wire, lighting the light bulb along the way. This is one way of describing how electrical potential causes electrons to flow through the circuit.

However, these electrochemical processes change the chemicals in anode and cathode to make them stop supplying electrons. So there is a limited amount of power available in a battery. When you recharge a battery, you change the direction of the flow of electrons using another power source, such as solar panels. The electrochemical processes happen in reverse, and the anode and cathode are restored to their original state and can again provide full power.

How are solar panels on DS1 made?

DS1's Photovoltaics are made out of gallium arsenide (GaAs). GaAs is made into a cylinder that is then sliced into cells. These solar cells are then connected to the rest of the power network. Solar concentrators, made of clear plastic, are placed above them to focus the Sun's rays. More common in commercial, Earth-bound systems are crystaline silicon wafers, which are grown into cylinders and sliced to make cells. These are less efficient than GaAs cells, but are much cheaper.

What is a semiconductor?

A semiconductor is called a semiconductor because it is a type of material that has an electrical resistance which is between the resistance typical of metals and the resistance typical of insulators, so it kind of, or "semi"-conducts electricity. Semiconductors are used in many electrical circuits because we can control the flow of electrons in this material, for example, with a controlling current. Semiconductors are also used for other special properties. In fact, a solar cell is made of semiconductors which are sensitive to light energy. The amount of light energy that hits the semiconductors will determine the amount of electrical current generated by those semiconductors that make up the solar cells.

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