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+ What is Solar Energy and How Do Solar Panels Work?
Solar energy works by capturing the sun’s energy and turning it into electricity for your home or business.
Our sun is a natural nuclear reactor. It releases tiny packets of energy called photons, which travel the 93 million miles from the sun to Earth in about 8.5 minutes. Every hour, enough photons impact our planet to generate enough solar energy to theoretically satisfy global energy needs for an entire year.
Currently photovoltaic power accounts for only five-tenths of one percent of the energy consumed in the United States and 0.5% of the energy consumed in South Africa. But solar technology is improving and the cost of going solar is dropping rapidly, so our ability to harness the sun’s abundance of energy is on the rise.
A 2017 report from the International Energy Agency shows that solar has become the world’s fastest-growing source of power– marking the first time that solar energy’s growth has surpassed that of all other fuels. In the coming years, we will all be enjoying the benefits of solar-generated electricity in one way or another.
How Do Solar Panels Work?
When photons hit a solar cell, they knock electrons loose from their atoms. If conductors are attached to the positive and negative sides of a cell, it forms an electrical circuit. When electrons flow through such a circuit, they generate electricity. Multiple cells make up a solar panel, and multiple panels (modules) can be wired together to form a solar array. The more panels you can deploy, the more energy you can expect to generate.
What are Solar Panels Made of?
Photovoltaic (PV) solar panels are made up of many solar cells. Solar cells are made of silicon, like semiconductors. They are constructed with a positive layer and a negative layer, which together create an electric field, just like in a battery.
How Do Solar Panels Generate Electricity?
PV solar panels generate direct current (DC) electricity. With DC electricity, electrons flow in one direction around a circuit. This example shows a battery powering a light bulb. The electrons move from the negative side of the battery, through the lamp, and return to the positive side of the battery.
With AC (alternating current) electricity, electrons are pushed and pulled, periodically reversing direction, much like the cylinder of a car’s engine. Generators create AC electricity when a coil of wire is spun next to a magnet. Many different energy sources can “turn the handle” of this generator, such as gas or diesel fuel, hydroelectricity, nuclear, coal, wind, or solar.
AC electricity was chosen for the S.A. electrical power grid, primarily because it is less expensive to transmit over long distances. However, solar panels create DC electricity. How do we get DC electricity into the AC grid? We use an inverter.
What Does a Solar Inverter Do?
A solar inverter takes the DC electricity from the solar array and uses that to create AC electricity. Inverters are like the brains of the system. Along with inverting DC to AC power, they also provide ground fault protection and system stats, including voltage and current on AC and DC circuits, energy production and maximum power point tracking.
How Does a Solar Panel System Work?
Here’s an example of how a home solar energy installation works. First, sunlight hits a solar panel on the roof. The panels convert the energy to DC current, which flows to an inverter. The inverter converts the electricity from DC to AC, which you can then use to power your home. It’s beautifully simple and clean, and it’s getting more efficient and affordable all the time.
However, what happens if you’re not home to use the electricity your solar panels are generating every sunny day? And what happens at night when your solar system is not generating power in real time? Don’t worry, you can still benefit through a system called “net metering” or by saving your extra power in a battery bank to be used when there is no solar PV power being generated.
A typical grid-tied PV system, during peak daylight hours, frequently produces more energy than one customer needs, so that excess energy is fed back into the grid for use elsewhere or stored in the battery bank. The customer gets credit for the excess energy produced, and can use that credit to draw from the conventional grid/battery bank at night or on cloudy days. A net meter records the energy sent compared to the energy received from the grid.
For a personalised discussion of a solar solution to meet your own energy needs feel free to give us a call and arrange an appointment.
+ How Many Solar Panels Do You Need: Panel Size and Output Factors
Determining how many solar panels you’ll need for your home means first knowing what your goals are. Do you want to minimize your carbon footprint? Maximize your return on your investment? Save as much money as possible? Most people want to save money while minimizing their environmental impact.
To calculate how many solar panels you need, you need to know the following:
1. How much solar power will you need?
To determine your home’s average energy requirements look at past electricity bills. You can calculate how many solar panels you need by multiplying your household’s hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel’s wattage. Use a low-wattage (150W) and high-wattage (370W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year). Note that how much sunlight your roof gets and factors such as roof size and battery storage will figure in as well.
If you work with Solar Energy Group one of our solar experts will handle all these calculations for you and will do a . But to give you some idea of how many solar panels are needed for the average home (or for your home in particular), here is a sample set of questions that a solar professional might use to figure it out:
2. How many watts do you currently use?
Look at your electricity bill for average usage. Look for “Kilowatt Hours (or kWh) Used” or something similar, and then note the time period represented (usually 30 days). If your bill doesn’t show kilowatt hours used, look for beginning and ending meter readings and subtract the previous reading from the most recent one.
You want daily and hourly usage for our calculations, though, so if your bill doesn’t show a daily average, just divide the monthly or annual average by 30 or 365 days, respectively, and then divide again by 24 to determine your hourly average electricity usage. Your answer will be in kilowatt-hours (kWh). (And just in case you are wondering, a kilowatt-hour is how much power you are using at any given time multiplied by the total time the power is being used.)
A small home in a temperate climate might use something like 200 kwh per month, and a larger home in the south where air conditioners account for the largest portion of home energy usage might use 2,000 kWh or more. The average South African home uses about 900 kWh per month. So that’s 30 kWh per day or 1.25 kWh per hour. 900 kWh / 30 days per month = 30 kWh/day / 24 hours = 1.25 kWh/hour.
Your average daily energy usage is your target daily average for to calculate your solar needs. That’s the number of kilowatt-hours you need your solar system to produce if you want to cover 100 percent of your energy needs.
It’s important to note that solar panels don’t operate at maximum efficiency at all times. (See Solar 101: How Does Solar Energy Work?). Weather conditions, for example, can temporarily reduce your system’s efficiency. Therefore, experts recommend adding a 25 percent “cushion” to your target daily average to ensure you can generate all the clean energy you need.
3. How many hours of sunlight can you expect in your area?
The peak sunlight hours for your particular location will have a direct impact on the energy you can expect your home solar system to produce. For example, if you live in Phoenix you can expect to have a greater number of peak sunlight hours than if you lived in Seattle. That doesn’t mean a Seattle homeowner can’t go solar; it just means the homeowner would need more panels.
The Renewable Resource Data Center provides sunlight information by state and for major cities.
Now multiply your hourly usage (see question No. 1) by 1,000 to convert your hourly power generation need to watts. Divide your average hourly wattage requirement by the number of daily peak sunlight hours for your area. This gives you the amount of energy your panels need to produce every hour. So the average U.S. home (900 kWh/month) in an area that gets five peak sunlight hours per day would need 6,250 watts.
4. What affects solar panel output efficiency?
Here’s where solar panel quality makes a difference. Not all solar panels are alike. Photovoltaic (PV) solar panels (most commonly used in residential installations) come in wattages ranging from about 150 watts to 370 watts per panel, depending on the panel size and efficiency (how well a panel is able to convert sunlight into energy), and on the cell technology.
For example, solar cells with no grid lines on the front (like SunPower ® Maxeon cells) absorb more sunlight than conventional cells and do not suffer from issues such as delamination (peeling). The construction of our cells make them stronger and more resistant to cracking or corrosion.
Because of these wide variations in quality and efficiency, it’s difficult to make generalizations about which solar panels are right for you or how many you’ll need for your home. The main takeaway is that, the more efficient the panels are, the more wattage they can produce, and the fewer you will need on your roof to get the same energy output. Conventional solar panels usually produce about 250 watts per panel, with varying levels of efficiency. In contrast, SunPower panels are known to be the most efficient solar panels on the market.
To figure out how many solar panels you need, divide your home’s hourly wattage requirement (see question No. 3) by the solar panels’ wattage to calculate the total number of panels you need.
So that average South African home in Pretoria, would need about 25 conventional (250W) solar panels or 17 SunPower (370W) panels.
5. What is the effect of solar panel size?
If you have a small or unusually shaped roof, solar panel size and numbers are important considerations. With a large usable roof area, perhaps you can sacrifice some efficiency and buy more larger panels (at a lower cost per panel) to get to your target energy output. But if your usable roof area is limited, or if it’s partially shaded, being able to use fewer smaller high efficiency panels may be the best way to make the most possible power over the long term, ultimately saving you more money.
Typical residential solar panel dimensions today are about 65 inches by 39 inches, or 5.4 feet by 3.25 feet, with some variation among manufacturers. SunPower panels are 61.3 inches by 41.2 inches.
These dimensions have remained more or less unchanged for decades, but the efficiency and output from that same footprint have changed dramatically for the better. In addition, SunPower designs entire systems to have virtually no gaps between panels and uses invisible framing and mounting hardware to keep the rooftop footprint as tight, efficient and attractive as possible.
Knowing the answers to the above questions will give you an idea of the ideal number of panels for your electricity generation needs — or at least a realistic range. Next, a professional installer needs to assess your roof architecture, angle to the sun and other factors to see if and how you’d be able to physically arrange the right number of panels on your roof to achieve your daily energy production goals.
You should also consider SSEG - Small Scale Embedded Generation as you’re considering figuring out your ROI for your solar system. Net metering is how your municipality credits you for producing excess solar energy when the sun is shining and then lets you draw from those credits when you’re using conventional power grid at night, if you don’t have a solar battery storage system.
To get started, give us a call and set up an appointment for us to do a solar assessment with you, which can help you figure out how much you might save going solar, what your actual consumption is, what system size you need, what a solar system would cost you and if this is a feasible option for you in your context.
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