Solar energy 101: Powering your home with sunlight
Have you noticed crews working on your neighbor’s roof lately and wondered how solar panels can work for your home? A quick description almost sounds like a science fiction plot.
A photon of sunlight hits a shimmering silicon sheet sitting on your roof. Almost magically, the panel converts the energy into electricity, powering devices across your home.
Increasingly, people are turning to renewable and clean solar energy to power their homes, cut their electrical bill and aid the environment. If you’ve ever considered installing a solar system but felt overwhelmed, we’re here to help.
In this post, we’ll discuss the basics of electricity and the science behind solar. We’ll also explore trends changing the country’s electrical grid. And if you want to learn more about installing a solar system of your own, the crew at Wolf Track Energy is ready to help you make it happen.
Basics of electricity
Let’s start from the top and learn about a couple of common electrical terms: voltage and current. It’s perhaps easiest to think of electricity moving through a wire as water flowing through a pipe. You can think of voltage as the pressure pushing the water through the pipe, and the amount of water as the current.
Electricity, simply put, is the movement of electrons in a conductor. In direct current electricity, electrons move in one direction, from the negative terminal to the positive terminal. With alternating current, electrons move back and forth.
Solar panels produce DC, but the outlets in your home use AC, so special equipment converts one to the other. Electricians also must consider resistance or impedance (forces constricting water flow in the pipe). That’s a topic for another post.
Your power company bills you based on kilowatt-hours, or kWh. That’s a unit of power (watts) over time. If you used one watt over an hour, that’s one watt-hour, or Wh. Running a microwave that’s rated at 1,000 watts for an hour makes one kWh.
In Duluth, you can expect your home’s electricity bill to come out to about a dime per kWh. You can buy meters that plug into your outlets that measure your appliances’ power use over time. Typically, things like hot water heaters and air conditioners are the biggest users of power in a home.
Powering the grid
Depending on where you live and the decisions of your policymakers and power company, your home’s electricity may be generated by spinning turbines that turn a rotor inside a giant electromagnet. Steam produced by burning coal, natural gas or through nuclear processes spins the turbine. A hydroelectric power plant instead harnesses water flow.
Fossil fuels are still the largest sources of electrical generation in the U.S., according to the Energy Information Administration. Renewables make up 20% of the country’s electricity, with solar representing just 2.3% of the overall pie in 2020, the EIA reported. Still, the use of solar and other renewable sources is growing.
In Minnesota, the state is shifting away from fossil fuel sources. About 3% of the state’s net generation came from solar in 2019, according to the EIA. A 2013 state law set an ambitious goal: 10% of the state’s electricity produced by solar by 2030. If you think that’s lofty, solar and wind could provide 70% of Minnesota’s electricity in 2050, according to Minnesota Solar Pathways, an initiative aimed at helping the state reach its solar power generation goals.
Minnesota produces enough solar to power more than 200,000 homes, according to the Solar Energy Industries Association, and the industry accounts for more than 4,000 jobs.
In neighboring Wisconsin, solar energy accounted for less than one-half of 1% of the state’s net electrical generation in 2019, according the EIA. The state has installed enough solar to power about 70,000 homes, according to the SEIA, a national trade group.
How solar panels work
Solar panels work by converting energy from the sun into electricity. This is known as the photovoltaic effect, which was discovered almost two centuries ago and has evolved into ever-improving solar systems. According to NASA, it was the space industry that “began to make the first serious use of the technology to provide power aboard spacecraft.”
Solar panels are made of individual cells of semiconductor material, most commonly silicon, that are responsible for converting sunlight into electricity.
“When light energy strikes the solar cell, electrons are knocked loose from the atoms in the semiconductor material,” according to this helpful NASA explainer. “If electrical conductors are attached to the positive and negative sides, forming an electrical circuit, the electrons can be captured in the form of an electric current — that is, electricity.”
A “module” or panel consists of individual solar cells. Installers wire those panels together into an “array.” Twenty to 25 panels would meet an average home’s power needs, according to EnergySage, a renewable energy marketplace. But that number depends on your location and power requirements.
Utility-scale projects are much larger. Xcel Energy has proposed a $575 million project to produce 460 megawatts (or 460,000,000) in central Minnesota, the Star Tribune reported. That’s a lot of panels!
Efficiency and the environment
Solar panels are roughly 15% to 20% efficient, according to the University of Michigan. That means they only convert about a fifth of the sun’s energy into electricity.
Other sources are more efficient. But that one data point doesn’t take into account that solar panels are merely harnessing an already abundant energy source. Coal plants, for instance, require excavating and burning fossil fuels to produce electricity.
And burning fossil fuels pumps carbon into the atmosphere, exacerbating climate change. A quarter of the greenhouse gas emissions in the United States come from producing electricity, the Environmental Protection Agency says.
But that gets to a common complaint about renewable energy sources like solar and wind: they’re only useful when the sun is shining or the wind is blowing. And while it’s true that solar panels require at least some sunlight, a battery system can store energy produced during the day for you to use on cloudy days or at night, as EnergySage points out.
To get an idea of how much solar energy will fall on a given area over time, we can measure a location’s solar radiation. Folks in the Duluth area can expect around 4.5 kWh/square meter/day. For context, El Paso, Texas gets about 7.5 kWh/sq. m. per day, and Seattle gets about 3.5.
The National Renewable Energy Laboratory has a cool interactive map that shows solar radiation levels across the country. And the University of Minnesota has an incredibly detailed map that will show you sites that are good for solar.
Installing a solar system
The makeup of a solar power system will vary on size and application, as well as your goals and budget. If you want to supply all of your electrical power from solar panels without relying on the local utility company, you’re going “off-grid.” If you’re still going to use power from your utility in some fashion, that’s a “grid-tied” system.
The power output of your solar system will also depend on its setup, down to the tilt of your panels. Ideally, your panels are facing the sun and are unobstructed by things that cast a shadow. That’s not always possible, so installers aim to place the panels in the right spot to maximize your output. Luckily, the crew at Wolf Track Energy can take all of that information into account and help you design the system that’s best for you.
Given the urgency of addressing climate change, governments and utilities have helped make it more financially palatable to install solar power systems. The federal government offers a 26 percent tax credit, which was just extended for two years. And Minnesota has “net metering,” which basically means any excess power you generate from your panels and send back to the grid entitles you to a credit on your electric bill.
Some utilities, including Minnesota Power, have their own incentives. Wolf Track Energy can also help you navigate these incentives and get the most bang for your buck.
Now let’s discuss the equipment you’ll need to power your home or business with the sun’s rays.
The panels themselves are an obvious starting point. But there’s a long list of other equipment you’ll need to make the whole thing work. People in the industry call this the “balance of system.” Let’s walk through some of the most common components of a solar power system.
Solar panels are typically rated at a few hundred watts each. Determining how large of a solar array you’d need to power your house depends on a few factors. Power consumption and how sunny the skies are above your home are two major considerations.
Your solar system will last for years – or decades to be more precise. The panels lose their efficiency over time, but they are generally considered to last about 25-30 years. So while there may be a large up-front investment, you’ll be harnessing the sunshine for years to come.
Solar setups can involve charging a large battery bank. But you’d also need what’s known as a charge controller to regulate the process and prevent the batteries from overcharging. According to EnergySage, the most common type of battery found in new home installations is lithium ion. Lead acid batteries have also been in use for a long time.
To get AC electricity from your outlets, you’ll need an inverter to take the DC electricity produced by the panels and convert it to AC. As this helpful altE explainer lays out, inverters can come in the off-grid or grid-tied variety.
Depending on the specifics of your home or business, it might make more sense to install the panels on your roof or the ground. The roof is an obvious choice, since it’s an unused space high off the ground that’s less likely to be obstructed by shade. But crews might need to install panels on the ground for some jobs. In either case, you’ll need some kind of rack to hold your array together.
Trends in solar power
You’ve probably seeing a lot of headlines about solar power lately, so it might be hard to keep up with this rapidly changing industry. But here’s a few larger trends we’re seeing.
- Solar installation is growing rapidly. The U.S. installed enough solar panels to power 17.7 million homes in 2020, according to the SEIA, the national trade group. The 19.2 gigawatts installed was a record. Residential installations were affected by the pandemic, but there are plenty of reasons to expect solar to grow in the coming years. As of late 2019, only 6 percent of homeowners had installed panels at their home. But almost half of homeowners gave “serious thought” to that idea, according to the Pew Research Center. Meanwhile, utilities are increasingly adding solar power generation instead of fossil fuel plants.
- Solar is becoming more affordable. The past five years has seen the panels’ price tag drop by more than a fifth, according to EnergySage, which tracks solar installation prices. Researchers at MIT said the dropping costs have to do with government policies, economies of scale and increased efficiency. In other words, today’s panels convert more sunlight into electricity than older ones. Their study found that the costs of solar modules plummeted by 97 percent between 1980 and 2012.
- Carmakers are shifting toward electric vehicles. It’s not just Tesla anymore. General Motors said earlier this year it plans to produce only electric cars by 2035. What does that mean for solar power? Some homeowners and public charging stations use solar panels to charge those cars’ batteries. As this New York Times article points out, more electric vehicles will require more charging stations. Wolf Track Energy has experience with electric vehicle charging stations and can help keep your car powered up.
That was a lot of information to handle, so congrats on making it this far. Hopefully you have a better grasp of solar power and can start making decisions about your own installation project.
Read more from Northland’s solar energy experts:
- Microinverters vs. optimizers: What makes for the best solar system?
- Solar incentives: What you need to know
- How installers mount rooftop solar panels: Flashing, rails and more
- Off-grid solar batteries: A guide to energy self-reliance
- Snow on solar panels? Here’s why you shouldn’t panic