Solar Energy

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Solar PV Basics – How Do Solar Panels Work?

“Solar PV‖ stands for solar “photovoltaic” panels. Very simply, solar PV panels turn sunlight into electricity, and this is how:
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Every day, light hits your roof’s solar panels with photons (particles of sunlight). The panel converts those photons into electrons of direct current (―DC‖) electricity. Naturally, the sunnier it is, the more energy is produced by the panels. Those produced electrons flow out of the panel and into an inverter and other electrical safety devices. The inverter converts that ―DC‖ power into alternating current or ―AC‖ power. AC power is the kind of electric juice that your television, computer, and toasters use when plugged into the wall outlet. A bi-directional meter keeps track of the all the power your solar system produces. Any solar energy that you don’t use immediately will go back into the grid through the meter. Then at night or on cloudy days, that extra solar juice is credited back to your bill. So, net metering is similar to having a virtual battery-back up system (we explain more about grid-tied solar home solar systems later)

Different types of Solar Panels
Let’s talk about the basic types of solar panels and how they’re used.

Monocrystalline silicon (mono-silicon or single silicon)

Right now, these are the most efficient type of solar panels. In other words, when sunlight hits these puppies, more of it turns into electricity than the other types below. As a result of their high silicon content, they’re also more expensive, but you need fewer of them. That’s why they’re ideal for roofs. You can tell if you have a monocrystalline solar panel by its square-ish cells.

Polycrystalline silicon (multicrystalline, multi-silicon, ribbon)

―Poly‖ panels have lower silicon levels than ―mono‖ panels. In general, that makes them less expensive to produce, but they’re also slightly less efficient. The good news is that their overall construction design can often make up for the efficiency loss, so they’re also

good for roofs. You can tell poly-silicon panels by their groovy mélange of silicon woven through thin rectangular conduit wires.

Thin film (amorphous silicon, cadmium telluride, copper indium gallium (di)selenide)
Everyone talks about “thin film” because they’re really inexpensive to make and they don’t mind the heat, which is all cool. Except right now, they’re very inefficient, which means you’ll see them in big solar farm projects with a lot of land, but not on your roof.

Photo Credit / CC BY-SA 2.0

BIPV (building integrated photovoltaics)

BIPV’s can look like real roofing tiles (solar shingles are an example). That’s nice, but good looks do cost a lot more. Second, they’re way less efficient than conventional PV, which means you need a sunny spacious roof to make a dent in your electric bill. Finally, they may not last as long as regular panels. Right now, 1bog doesn’t contract for BIPV systems.

Solar hot water (thermal) panels

Finally, there’s another type of panel that has nothing to do with electricity. Instead of paying the gas company to heat your hot water tank, solar thermal panels produce hot water for your home and/or your pool. Some systems can even provide heat and air conditioning too. 1bog currently doesn’t offer solar thermal deals. More information: Solar Hot Water vs Solar PV.

Solar Panel Efficiency and the Factors that Affect it.

What’s a typical solar panel efficiency rating?

Most solar panels are around 11-15% efficient (check out this handy comparison table of solar panel efficiency to see the differences between brands). The efficiency rating measures what percentage of sunlight hitting a panel gets turned into electricity that you can use. The higher the efficiency, the less surface area you’ll need in your solar panels. Although the average

percentage may sound a little low, you can easily outfit a typical roof with enough power to cover your energy needs.
What are the most efficient solar panels?

In the lab, scientists have developed solar panels that are 40% efficient, or even slightly more than that. But there’s a big difference between the lab and the real world. Manufacturers haven’t yet figured out how to take these experiments and produce economically viable products. Thinking you should wait for new whiz-bang panels is one of the most common solar myths. Out of the solar panels on the market, SunPower makes some of the most efficient–one of their models is 19% efficient. They’ve reached that number by using several techniques, including a reflective coating that can capture more light from an angle. They also offer a line of panels that’s 18% efficient. Sanyo, another solar panel manufacturer, offers efficient models as well.
Should I choose the most efficient solar panels available?

High efficiency doesn’t mean better, it just means your panels use less space on your roof. Efficiency isn’t usually a critical concern unless you have an unusually small space for your solar panels. In that case, you’ll probably choose to spend a little more for higher efficient panels. One Block Off the Grid’s pre-negotiated solar deals typically offer a choice of different recommended panels, including a more efficient panel for smaller spaces. If you have a normal amount of roof space to work with, you can focus more on the price and the annual expected kilowatt production of your panels. We’ll help you choose the best panel for your particular needs and design a customized system around them. To request your free, no obligation system design and price quote, sign up here.
Getting the best power performance

In addition to efficiency and size, there are other factors that affect how much power your solar panels will generate. It’s important to make sure panels are installed in the optimal position, which is why you want to work with a highly experienced provider like One Block Off the Grid. We’ll determine the correct orientation for your panels based on the direction and angle of your roof. We’ll also make sure the panels are installed with the proper amount of airflow so they stay cool– solar panels don’t like it too hot, and they’ll produce more power if they’re the right temperature. (To learn more, check out this article on how solar panels work.) If you just go to the Big Box store and slap on a bunch of panels, you could end up wasting a lot of money. A high performing, long lasting solar array can incorporate dozens of factors in its design.
Factors that affect solar array efficiency include:

Panel Orientation

In the U.S., your roof ideally should face south, but a quality design can often compensate for other directions.

Roof and Panel Pitch The ―pitch‖ or tilt of your roof can affect the number of hours of sunlight you receive in an average day throughout the year. Large commercial systems have solar tracking systems that automatically follow the sun’s tilt through the day. These are expensive, however, and not typically used for residential solar installs.

Temperature Some panels like it hot but most don’t. So, panels typically need to be installed a few inches above the roof with enough air flow to cool them down. Some photovoltaic panels are designed to be more efficient in hotter climates. Check out the solar panels used by San Antonio and Phoenix home owners.

Shade Basically, shade is the enemy of solar power. With poor solar design, even a little shade on one panel can shut down energy production on all of your other panels (like a bad bulb in a string of Christmas lights). Before we design a system for your home, we’ll conduct a detailed shading analysis of your roof to reveal its patterns of shade and sunlight throughout the year. Then, our local installation partner conducts another detailed analysis to verify our findings. This is just one of many reasons to work with a highly experienced solar provider like One Block Off the Grid.

For more on solar cell efficiency, go back to the Different Types of Solar Panels. Want to know more about what goes into a solar PV system? See our next page.

Solar Equipment: Inverters, Solar Panels, and Sunlight. What else do you need?
We’ve already discussed the basics of solar panels. Now, let’s go over all of the other important components of a solar PV system.

The Inverter
The solar inverter is the second most important (and second most expensive) component of a solar PV system. It’s important because it converts the raw Direct Current (―DC‖) solar power that is produced by your solar panels into the ―plug-the-toaster-in‖ Alternating Current (AC) power that comes out of your wall sockets. Inverters also have technology that maximizes the power output of that DC energy. There are two basic types of inverters.

Central Inverters

Central inverters are well-tested and reliable systems that have been around for decades. These are the most common types of inverters. With central inverters, every solar panel is wired in a ―string‖ to the inverter box. The conversion from DC to AC occurs at one central location, such as your garage. Because the solar panels are wired in ―series,‖ each panel’s power output depends on all of the panels working. Think of a string of Christmas tree lights. If one bulb goes out, the whole string of lights go out until the bad bulb is replaced. So, if shade from a tree hits one panel, it can seriously diminish the power produced by the whole solar system until the shade clears. This is why an accurate shade analysis is so important.

Micro Inverters

Micro inverters are relatively new to solar. Instead of converting the DC to AC power at a central location, micro inverters are installed right under each solar panel. The main advantage to micro inverters is the ability for each solar panel to transmit power into your home. In other words, each panel is its own solar powered island and keeps churning out solar watts regardless of what happening to the panel beside it. The down side of micro inverters is that they can be more expensive and take more labor cost to replace each inverter. Also, because they’re so new, micro inverter reliability is unproven outside of lab testing.

Inverter Warranties
Central inverters typically carry a 10 year warranty and often go for 12 to 15 years or longer. The leading micro inverter company has a 15 year warranty, but the inverter(s) could last years longer too. In either case, if you stay in the same house for 20+ years with your same solar panels, (which last 20 to 25 years or longer) expect to pay to replace your inverter(s) at some point. How much? Due to manufacturing advances in 15 years, probably less than the current cost of about $1200-$2000. But who knows? Could be about the same price. Time will tell.

The BOS (Balance of System)

There are many other less well known and less expensive parts to a solar system. Installers typically wrap these up into ―The BOS‖ or ―Balance of System.‖

The balance of system includes components such as wiring, emergency DC disconnects, system monitoring hardware, the frames or “racking” that holds your panels to the roof and at the right angle, nuts, bolts, roof “flashing” to prevent leaks, and more.

The balance of system components required to attach solar panels to your roof is covered in the next section, the Nitty-Gritty on Solar Roofing.

The Nitty-Gritty Solar Roofing
Not all roofs are created equal for solar, so it’s important to understand a few basic things about roofing when evaluating your home. Here’s the real deal on solar roofing concerns.

Different Types of Roofs.
Provided there’s enough space and sun, solar can be installed on any roof. It does, however, cost more to install on tile roofs, shake shingle roofs, and very steep roofs. Tile and shake roofs cost more for solar because there’s no way to walk on them without causing some minor damage, such as breaking a clay tile here and there. Installers will make it right, but it may raise your costs somewhat. Similarly, very steep roofs may take more time to install and require special cranes or equipment. On flat roofs, you may need a few more racks to position

the panels at the correct angle. We can account for the different types of roofs with our solar estimate tool.

The Condition and Age of Your Roof.
Solar panels covering your roof will certainly reduce some of the weatherization wear on the portion being covered by your roof. However, solar panels are not a replacement for a new roof, unless they’re solar powered roofing tiles (photovoltaic shingles), known as ―BIPV‖ or Building Integrated Photo Voltaic tiles. It’s therefore important to know the warranty on your roof and how many years are left on the life of your roof. If you’re close to the end of your warranty and have had a lot of leaks in the past few years, you should probably replace your roof before going solar. Yes, this will cost you more money, but it will cost you even more in labor costs to remove the solar panels in order to replace or make repairs on your roof after the solar is installed. If you think you’re about five or more years away from a roof replacement, it usually makes sense to go solar first.

How are Solar Panels attached to my Roof?
The way panels are attached to your roof depends on the type of roof you have. In general, composite shingle roofs are attached through bolting mounts into your strongest roof rafters and then attaching rails to those mounts. But it’s not just drilling a hole and crossing your fingers. Installers also add sealants into and around the mounts that fill in any gaps. Often the mounts are surrounded by metal ―flashing‖ – coverings that serve as an extra rain proof barrier. Parallel rails are then attached to the mounts and the solar panels are attached to the rails. Live in a townhouse or have some other flat roof? These roofs can be attached with racking and some type of ballast, such as concrete blocks, to keep panels stable and without drilling holes the roof’s structure.

Concerned about Solar Panel Theft?
First of all, this is rare. Yes, you might have heard about it in the news, but that’s why it’s news: It doesn’t happen often. The reason is that it’s not something that can be done while you’re sleeping or without someone noticing. Even if a crew were pretending to be solar un-installers, your neighbors are going to notice since you made such a big deal about getting them in the first place. Even if you live in a high crime area, there are locking systems you can buy, as well as special cements that would require a blow torch and a lot of time to remove. A little sticker next to the

rack that says that these solar panels are protected from theft by X product should deter thieves from trying. Finally, your solar panels should be covered by your home insurance. This should cost you very little extra or nothing extra, though that may differ by state and if data shows thefts increasing. So far it hasn’t which is why insurance companies charge little to nothing extra to cover solar panel theft or accidents. Check with your insurance agent about your policy.

Pole mounts, the non-roof Solar Alternative.
There are cases when a person’s roof and/or garage are facing the wrong way or there’s too much shade. An alternative is a pole mounted solar system. This requires some back yard space and extra cost to dig a trench for running wires from the poles to your home’s electric panel.

The Truth about Solar Batteries and Battery Back-up Systems

Solar and Batteries
When some people think about solar, they might think that they will become free from ―The Man,‖ because a battery will allow them to store any excess power they generate, thus taking

them off the grid. While this is possible with solar, it doesn’t make much financial sense for most people. Allow us to explain:

Grid Tie Solar Most solar systems are ―grid tied‖ these days. That means when the system is generating power during the day, any excess power it makes is fed back into the grid through something called ―net metering.‖ Your meter spins backwards and the utility credits you for that power. At night or on overcast days, you’ll use grid power instead of solar, but your utility doesn’t charge you until you’ve used up all the credit you generated through your panels. More on grid tie solar.

It Means You Probably Don’t Need Batteries You don’t need batteries for your solar system if you’re already connected to the grid. It’s an option, but not one that most people use these days because the batteries are still very big and bulky. They’re also expensive and need to be replaced every five to ten years, depending on the type and how well you take care of them. Battery technology is evolving and solar batteries may become a more viable option someday, but for most people right now, it’s more practical to simply tap the grid in off hours.

Net metering – The Virtual Battery Net metering is like a virtual battery. The utility keeps track of any extra power your solar panels produce, which spins your electric meter backwards. Then at night, you simply use grid power on the credit you earned while supplying the utility company with power during the day. Net metering is maintenance-free and typically costs around $5 per month in administrative fees.

What about ‘One Block Off the Grid’? It’s true, our name has ―off the grid‖ in it. It’s just a metaphor. We want to take at least one block’s worth of grid energy usage out of every city per campaign, but the bottom line is that we’re here to help you buy solar panels for your home.

Solar Battery Back-up Systems
We understand that some people are interested in solar batteries in the interest of disaster preparedness, and because this is America, you’re free to spend your hard earned money any way you want. Here are a few things to consider in your decision though:
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Battery back-up systems are reliable for those “what-if situations.” However, those “what-if” situations are fairly rare. The American electric grid is over 99% reliable, and using a battery would mean you’ed be spending an extra $5,000 to $10,000 every 10 years for the 1% chance that you will need battery back up.

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Also, disasters that upset the grid are typically repaired within days. There are, of course, exceptions like Hurricane Katrina…..but: It would most likely be more cost effective to spend money on flashlights, candles, matches, batteries, extra blankets, and dry good food, water, radio, etc, and be without the modern conveniences for a few days than it would be to purchase an expensive battery. Even in Hurricane Katrina’s case, your entire roof could have been blown away and/or your battery system under water and ruined. Same for an earthquake. Having a battery back up system may not be so important if the rest of your house is unlivable. Bottom line: Battery back-up systems do work, but they’re expensive for the few times they’re needed. It’s more cost effective to prepare to live for a few days without electricity until power is restored.

Solar Maintenance & Monitoring: A Five-Minute Guide

Solar Maintenance
One of the great things about grid-tied solar is that the solar system is very low maintenance. There are no moving parts, so if designed correctly, there are only a few things you need to do to keep churning out free solar energy:

Dusty solar panels will decrease your solar output. If you live in a low-dust climate with occasional rain, you may need to go on your roof and wipe off those panels with some mild soapy water with a squeegee once every quarter. Don’t use any strong detergents. Depending on your roof and solar configuration, you might even be able to do this with an extended mop, extended squeegee, and a garden hose without getting on to the roof. Photo of washing solar panels

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If you live in dusty climates and go solar in Phoenix or San Antonio, for example, you may need to clean your system more often to get the most power. Also be aware of bird droppings, leaves, or other debris that might fall on your roof. It may be time to trim back some trees if it’s been a few years since your original installation and shade analysis. Make a schedule to take a visual look at your solar system to make sure it’s clear.

Solar Monitoring Devices and Services.
Another way to make sure you’re getting the most solar potential out of your PV system is through a monitoring systems and service. For a monthly fee or a flat up front cost, you can monitor how your system is performing.

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Your system is expected to produce a certain amount of power during each month. A solar monitoring system can tell you if your system is off line or if it’s not performing as expected and run diagnostic programs. Solar monitoring systems can also be educational, showing you how much power you’ve saved, how much CO2 you’ve saved, and how much money you’ve saved. Depending on the monitoring systems, you can access your information from the web, from a wall mounted-device, or even from your iPhone or other mobile device. Monitoring systems are usually an extra expense, whether as a monthly service or purchased up front. While not essential, they do make troubleshooting and system performance easier to see.

1BOG’s collective bargaining power makes going solar very affordable, but you can save even more money by making your home more energy efficient before going solar. Nearly 40% of the energy American homes consume is wasted due to poor insulation and other factors. Implement energy efficiency measures before you go solar, and you can reduce your energy needs and the size of your solar system. A smaller size, of course, means a lower solar cost. In addition, there are some innovative solar financing programs, such as San Francisco’s GreenFinanceSF program. This program requires your home to get an energy audit in order to qualify. The energy efficiency and solar are financed by bonds that pay the upfront costs of your solar loan. You pay it back over 20 years through your property taxes at a competitive interest rate. If you move before then, the new home owner takes over the remaining payments.

So, let’s talk about some ways to be more energy efficient and reduce your energy usage and your solar costs.
1. Get a Home Energy Audit

At 1BOG, we’re big promoters of energy efficiency, and one of the biggest things you can do is get a home energy audit. It may be hard to believe (and we already said this), but nearly 40% of the energy American homes consume is wasted through poor insulation, leaky ducts, or inefficient household appliances. An energy audit conducted by a trained professional can tell you exactly where you’re loosing money. Fixing these problems can dramatically cut energy costs for the typical home. We believe energy efficiency is so important that we partnered with San Francisco-based Recurve to offer 15% off energy audits for our SF-based members. 2. Use compact florescent lights (CFL) or light emitting diode (LED) bulbs You’ve already heard this before, but it’s amazing to see how often incandescent bulbs are still used. Honest, the old incandescent bulbs use 6 times as much energy as CFLs. Multiply that times every light in your house and you’ll see you’re wasting a lot of energy—and money. As for looks, the latest CFLs and LEDs are now closer to warmth and color of incandescent bulbs. 3. “Turn off those lights!” No matter what kind of bulb you use, there’s no sense in keeping a room light on if no one is in there. Simple rule: Last one out, turn off the lights. Another solution is a motion detector. These devices turn on the lights when you enter the room and turn them off when motion sensors don’t detect any movement. 4. Identify Phantom Loads/Vampire Loads This expression comes from your television, VCRs, computers, DVD players, cell phone ―bleeding‖ wasted energy. Although these devices are off, they or their charging systems actually on standby, wasting precious watts and cash. The easy fix is to get a power strip and turn off these devices when not in use. Power strips even come in the form of wall light switches now. 5. Buy ENERGY STAR® appliances

Energy Star rated appliances sometimes cost a little more, but save you much more over time, especially for energy hogs like your old refrigerator. And when you retire that old fridge, don’t plug it in the garage as a back-up. Kind of misses the energy saving point of retiring it. 6. Make your Refrigerator more Energy Efficient Vacuum and clean condenser coils on your refrigerator twice a year. Dust insulates (warms) the liquid coolant that your poor fridge is working so hard to cool down. Also, make sure to leave space between the refrigerator and surrounding walls to allow air to circulate. And try not to position the refrigerator next to the dryer or dish washer, which will also heat the fridge up and cause it to work harder. Finally, don’t leave the refrigerator door open for long stretches while you think about what to make for dinner. 7. Turn your fridge Thermostat Up Your fridge needs to be cold, yes, but not freezing. Buy a hardware thermometer, place it in the fridge, and bump the beer chiller up to 38 degrees. Set the freezer to 5 degrees or even higher. Similarly, turn the AC up to 78 degrees, and even higher, if you’re away during the day. 8. Buy a Programmable Home Thermostat and Use it Many people buy a programmable thermostat, but don’t ever program it. Set the thermostat to turn off when you leave for work and turn on right before you get home. (Of course, if a significant other stays at home or your have a pet, program the temperature appropriately.) 9. Consider Skipping the Dryer Use a gas clothes dryer instead of an electric. Better still, use more free solar energy by hanging your clothes out to dry on a clothes line. Also, make sure you clean out the lint from the back of the dryer. 10. Switch to Gas or Solar for Heating Water Switch to gas hot water system or a solar hot water system. Heating water with electric coils is very inefficient and expensive. 11. Buy a Gas Stove instead of an Electric Gas heats more efficiently than electric. Microwave ovens are also efficient. Whatever stove you have, don’t peak to see if it’s done. This wastes heat and energy to maintain the desired temperature. Instead of peaking, set a timer and forget about it. 12. Pay Attention to Heating and Cooling

Your heating and cooling systems are by the most expensive parts of your utility bills. Buy an HVAC system that is efficient. Be sure to insulate the ducts and seal up any leaks. Insulate the attic. This will keep you cooler in the summer and warmer in the winter. Same for the walls. Likewise, you may need to change your windows. There are so many more ways to save energy. We recommend you consult a professional energy audit company. Many cities now have rebates and incentives (like property assessed clean energy financing) to help defer the cost of an energy audit. You can also check with your utility’s website and to learn about these programs. 1. Solar panels are also called:
solar photovoltaics (PV)

Solar panels are called photovoltaics because they harness photo (from the Greek word phos, meaning light) to make voltaic (from the Italian physicist Volta, meaning electric).

2. By themselves, solar panels create this type of electricity:
direct current (like in your car).

Like most generating technologies, solar panels create direct current, which is why you need inverters to change it into alternating current, that your house can use.

3. To clean solar panels on your roof, you need to:
rinse them with warm water and soap.

Solar panels are pretty tough, so the only cleaning they need is a warm wash to get the dust off, and a periodic removing of debris on your roof. Read more to learn about panel maintenance.

4. Fog and clouds affect the annual output of solar panels:
only a little.

Solar panels naturally like sun better than fog. However, fog barely affects a panel’s annual output, and the cool temperatures even help your panels!.

5. Solar panels were first used on residential homes in:
the 1950s.

It actually is not clear when or where the first solar panel appeared on a house, but commercial solar cells first appeared on the US market in 1955, so it can’t be long after that.

6. Solar panels generate more power:
in temperate weather.

Some panels excel in hot weather, but most need to be slightly cool to reach their maximum efficiency. As for listening to Mozart, that depends on your taste.

7. Solar panels are the most cost-effective option to lower your electricity bill:

Solar is perfect if it makes financial sense. When you sign up for free with 1BOG, your personal solar advisor helps you figure out if it does make sense– and for many people, it does. However, the easiest way to reduce your electric bill is by conserving energy.

8. More efficient solar panels reduce your electricity bill even further:
only if you have limited roof space.

The ideal solar system depends on your electric bill, so highly efficient (and highly expensive) 9. The country with the most installed solar power is:

Due to strong support of renewable energy, Germany leads the world in installed solar power. The US is catching up fast, although China is still the largest manufacturer of solar panels and is ramping up their own installations.

10. Solar panels are vulnerable to:
the zombie apocalypse.

Yes, the zombie apocalypse is the right answer. Baseball sized hail would wreck your solar panels (and your car, and your house), but most states require solar panels that are approved by the California Energy Commission to receive the rebates. All of these have been tested for strong hail. And such hail would probably signal the zombie apocalypse anyway. . Micro-inverters are a better option than regular inverters:
only in shady roof conditions.

The only significant difference between micro-inverters and regular inverters is that microinverters let a solar system still transmit power if part of it is in the shade. Normally, solar panels are wired in series to route through one inverter, so if one panel is shaded, the whole system produces much less power. Micro-inverters allow each panel to give their power straight to the grid, so if some panels are shaded the others can still make electricity.

2. A 4 kilowatt solar system would provide this much power in an hour:
4 kilowatt-hours

A kilowatt is the same as 1,000 watts, and a watt is a unit of power. Meaning, the number of watts describes how much energy per second your solar system produces. To get the actual amount of energy, you multiply the number of watts by the length of time, or in our case we multiply 4 kilowatts * one hour = 4 kilowatt hours. Kilowatt-hour is actually the standard measure of energy when it comes to home electricity use, even utilities use it!

3. Solar panels generate electricity by:
using the photoelectric effect of light hitting the surface of the panel to free electrons, which turn into electricity.

If you are clamoring Wait! This is Wrong! Solar panels use the Photo-Voltaic effect! Bravo. But you should know that the Photo-Voltaic effect is a variation of the Photo-Electric effect, and maybe we did say Photo-Electric to make this question slightly harder. Is that so wrong? For the everyone else, the photo electric and voltaic effects both describe a particular phenomenon of light particles hitting an atom. When a photon (light particle) collides with an

atom, there is a chance that it will be absorbed by an electron orbiting that atom. Quick aside on atomic structure: atoms (piles of protons and neutrons) are orbited by electrons, and those orbits depend on how much energy the electron has. End aside. The difference between the photovoltaic and photo-electric effect is what happens after the electron absorbs the photon. If the photon contains enough energy (or the electron was already in a high-energy orbital, for all you physics people reading this) the electron just rockets away from the atom, free at last! This is the photo-electric effect, and it is used in night vision devices, for instance. If the photon didn’t have enough energy to give the electron escape velocity (if you will, I know the actual sub-atomic interactions are more complicated, but it’s a good analogy!), then the electron might be simply pushed into a higher orbit around its atom. This is the photo-voltaic effect. Solar panels are engineered so that when electrons absorb photons, they are pushed from the valence band to the conduction band (what these bands actually are depends on the material that the atom is in). When the electron is in the conduction band, the semiconductor design of solar panels comes in. We could get into how the junction of P-type and N-type semiconductors use the electric field in their depletion region to shunt charge carriers, but that’s a little involved. Read the links if you want to know more! Suffice it to say that solar panels are designed so that there is an electric field pushing all the electrons in one direction (towards the inverter, which requires another explanation. Too bad). When electrons are bumped into the conduction band, the electric field forces them towards the inverter, where they are turned into usable electricity.

4. The majority of residential solar power is provided by:
crystalline solar panels.

There are two types of solar panels that fit on roofs: crystalline and thin film. While much cheaper and lighter, thin film is at the moment much less efficient than crystalline.

5. The first solar panel was made by:
Charles Fritts in 1883.

While Edward Weston received the first US Patent for a solar cell in 1888, and Alexander Becquerel first observed the photovoltaic effect in 1839, it was Charles Fritts who made the first solar panel. You could not recognize that first solar panel as anything remotely like a solar panel today-it was selenium covered with a thin layer of gold that converted less than 1% of the energy it received into electricity. You never know what science experiment will spawn a global industry!

6. Germany (the world’s #1 market for solar power) has the same amount of sunlight as:

Shocking but true! If you look at this insolation table you can see a good part of Alaska and Germany receive the same amount of sunshine each year. So don’t be discouraged if you live in foggy San Francisco or grey Seattle, solar can work almost anywhere!

7. Solar provides ___ % of the world’s power:

Of the roughly 1230 gigawatts of global electricity capacity, 21 gigawatts are solar, or 1.7%. Learn more about the global state of renewable energy by reading the Global Renewables Status Report.

8. Putting solar panels on your roof makes you the most money in:
New Jersey.

Hard to believe, but the Solar Renewable Energy Credits (SRECs) in New Jersey make a solar rooftop extremely profitable. We ran the numbers, and in New Jersey buying solar panels beats the stock market by 325% over 15 years. Granted this statistic is only true for the US, but still. 325%!

9. Realistically, how much of our electric grid could be solar powered?
this is too complicated for a multiple choice question!

It depends what you mean by realistic. Is it physically possible to have an electric grid powered solely by renewable energy? Yes, but it would require extraordinary investment in renewables, new transmission lines, and a vast battery system (for nighttime and calm days) that at the moment would be very expensive. A recent study found that (with reasonable investment) western states could meet the goals of 35% renewable power with the current transmission system. As the study also shows, others are more pessimistic-estimating that the costs of creating transmission lines to utilize renewable energy would be upwards of 100 billion dollars. Ouch.

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