What Is Solar Energy Explained Simply?

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What is Solar Energy?

Solar energy is the radiant light and heat from the sun that is harnessed using a range of technologies such as photovoltaic panels to generate electricity and solar heating systems. It is a renewable energy source, meaning it is naturally replenished and virtually inexhaustible (1). Solar energy technologies convert the sun’s rays into usable heat and electricity using the photoelectric effect and photovoltaic cells (2).

When the sun’s rays reach the Earth, they can be converted directly into electricity using solar photovoltaic (PV) panels. Solar PV panels are made up of many solar cells, which contain photovoltaic materials able to convert the sun’s rays into usable electricity through the photovoltaic effect. This electricity can then be used to power homes, buildings, and even cities (1).

Solar energy is considered a renewable source of energy because it comes from the sun. The amount of solar radiation that reaches Earth in a single hour is more than the world’s total annual energy needs (3). As long as the sun continues to shine, solar energy will be available as a clean and sustainable energy source.

Sources:

(1) https://www.seia.org/initiatives/about-solar-energy

(2) https://www.britannica.com/science/solar-energy

(3) https://en.wikipedia.org/wiki/Solar_energy

History of Solar Panels

The first solar cell was built in 1883 by Charles Fritts, who coated selenium with a thin layer of gold to form the junctions. However, the cells created by Fritts were very inefficient with less than 1% efficiency. The modern solar cell design was first created by Russell Ohl in 1939, who patented his design in 1941. Ohl’s cell used silicon instead of selenium and was more efficient and durable.

The first practical photovoltaic module was built in 1954 at Bell Labs by Daryl Chapin, Calvin Souther Fuller and Gerald Pearson. They used silicon solar cells created by Ohl which were assembled into a panel with a 6% efficiency. This design was then used in 1958 to provide energy for the Vanguard 1 satellite, marking the first use of solar power in space.

Through the 1960s and 70s, photovoltaic technology continued to advance as manufacturing techniques improved. The price of solar panels dropped substantially during this time, making them more feasible for terrestrial applications. In the 1990s and 2000s, advances in materials science and manufacturing further increased the efficiency and decreased the cost of solar panels. Today, solar power is a mainstream energy source around the world.

How Solar Panels Work

Solar panels work through the photovoltaic effect, which is the process of converting sunlight into electricity. When sunlight hits the solar cells in a panel, it knocks electrons loose from the atoms in the semiconductor material, creating an electric current. The electrons flow into metal conductors in the panel and then into wires, producing electricity.

The key components of a solar panel that enable this process are solar cells, a glass cover, metal framing, and electrical connections. Solar cells are made from thin layers or wafers of semiconductor materials like silicon, which are treated to have different conductive properties. When wired together into an array and enclosed in the glass and metal framing, the solar cells can absorb and convert sunlight into a usable amount of electricity.

The photovoltaic effect was first observed by French physicist Edmond Becquerel in 1839 when he found that certain materials would produce small amounts of electric current when exposed to light. Solar panels today operate on the same essential principle, just optimized through modern materials and manufacturing processes to increase efficiency and harness the sun’s energy on a much larger scale.

Source: https://www.energy.gov/eere/solar/how-does-solar-work

Types of Solar Panels

There are three main types of solar panels: monocrystalline, polycrystalline, and thin film.

Monocrystalline solar panels are made from silicon ingots, which are cylindrical blocks of pure silicon. The silicon atoms are aligned in a continuous crystal lattice structure, giving monocrystalline solar panels their characteristic black color and high efficiency. Monocrystalline panels are the most efficient, with average module efficiencies around 15-20%. However, they are more expensive than other types of solar panels.

According to EnergySage, monocrystalline panels are best suited for residential rooftops where space is limited. Some of the most popular monocrystalline panel brands include SunPower, LG, Panasonic, and Solaria.

Polycrystalline solar panels, also called multicrystalline, are made from cut silicon blocks cast into ingots. The silicon atoms have a more disjointed crystal structure, which gives the panels a speckled blue color. Polycrystalline panels are less efficient than monocrystalline, with average efficiencies of 13-16%. However, they are cheaper to produce than monocrystalline panels.

According to This Old House, polycrystalline panels are a good option for most residential solar projects. Some popular polycrystalline panel brands include Canadian Solar, Longi Solar, JinkoSolar, and Trina Solar.

Thin film solar panels use a super thin layer of photovoltaic material on a substrate like glass or plastic instead of silicon crystals. This allows thin film panels to be lightweight and flexible, but also less efficient with averages of 7-13%. The most common thin film materials are cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). Thin film works well when space is limited.

Solar Panel Efficiency

Solar panel efficiency refers to the percentage of sunlight that hits the panel and gets converted into electricity. It represents the ratio of electrical output from the solar panel to the input of solar energy from the sun.¹ The typical efficiency range for solar panels is between 15-22%.

There are several factors that impact the efficiency of solar panels:

Type of solar panel – Monocrystalline panels are the most efficient (15-22%), polycrystalline are less efficient (13-16%), and thin film are the least efficient (7-13%).

Temperature – Solar panels become less efficient as the temperature increases. Cooler climates allow for higher efficiencies.
Shading – Even small amounts of shading from trees, chimneys, etc. can greatly reduce the solar panel efficiency.
Age – Solar panel efficiency degrades slightly over time, typically 0.5-1% per year as materials degrade.

Reflection – Dirt, dust, snow cover, etc. can reflect sunlight rather than absorbing it, lowering efficiency.

Understanding these factors allows homeowners to choose the right solar panels for their needs and climate while maximizing efficiency.

Cost of Solar Panels

The cost of solar panels is measured in dollars per watt. The typical cost ranges from $2.87 to $3.85 per watt, according to Forbes. This cost includes the solar panels themselves as well as inverters, wiring, and installation.

For a complete solar panel system, the total cost is calculated by multiplying the cost per watt by the number of watts your system requires. Most homes need between 3,000 to 8,000 watts, so a typical 5,000 watt system would cost around $15,000 to $20,000 in total.

There are several factors that affect the overall cost of a solar panel system:

Type of solar panel – More efficient panels like monocrystalline tend to cost more per watt

Size of the system – More panels and watts means higher overall cost
Roof type and pitch – Complex roofs require more custom mounts and labor
Location and sun exposure – Areas with more sun can use smaller systems

Permits and installation – Complex municipal permitting and electrical work can add expenses

While solar panels involve a significant upfront investment, the energy savings over their 25+ year lifetime make them financially worthwhile for most homes.

Solar Panel Sizing

The size of a solar panel system for a home depends on several factors, including the home’s energy usage and roof size. Determining the right system size involves analyzing the home’s past electric bills to estimate its average energy usage. According to Pineapple Energy, the average home solar system size is between 6-8 kW (kilowatts) ^[1]. This provides enough power for most households. Southern Energy states a typical residential solar system today is around 8.5 kW with an average price of $17,000-20,000 after incentives ^[2].

For a 2,000 sq ft household, the system may need 20 panels in the 3×5 feet size range. CNET notes the three main solar panel sizes are 60-cell, 72-cell and 96-cell panels ^[3]. Overall, it’s recommended to get a professional solar assessment done rather than guessing system size.

^[1] https://pineappleenergy.com/resources/average-household-solar-system-size/

^[2] https://southern-energy.com/what-size-solar-system-do-you-actually-need/

^[3] https://www.cnet.com/home/energy-and-utilities/this-is-how-many-solar-panels-you-need-to-power-your-house/

Net Metering

Net metering is a billing mechanism that credits solar energy system owners for the electricity they add to the grid. It allows you to offset your electricity usage at retail rates. With net metering, your home’s electrical meter can actually spin backwards when your solar panels produce more electricity than your home is using. This excess electricity goes back into the grid, offsetting the electricity consumed when your solar panels aren’t actively producing electricity (at night, for example).

Here’s how net metering works:

During times when your solar panels produce more electricity than your home is consuming, the excess electricity is fed back to the grid.
This electricity offsets electricity that you pulled from the grid when your solar panels weren’t actively producing power.

At the end of each billing cycle, you are billed only for your net electricity use. This is the amount of electricity consumed minus the excess electricity fed back into the grid.

Net metering policies, rates and caps can vary significantly by state. Many states have implemented net metering policies to encourage solar adoption. However, some utilities have lobbied to implement less favorable policies or add fixed charges on solar customers. When considering solar, it’s important to understand the net metering policies and rates in your specific area.

Federal Solar Incentives

The federal government offers several incentives to encourage homeowners and businesses to go solar. The most significant is the federal solar Investment Tax Credit (ITC).

The solar ITC allows taxpayers to deduct 26% of the cost of installing a solar energy system from their federal taxes. For residential projects, this credit applies to systems put into service by the end of 2032. After that, the ITC will drop to 22% for systems installed in 2033. For commercial projects, the 22% credit will take effect starting in 2033 [1].

Along with the ITC, homeowners and businesses can claim depreciation deductions on their annual tax returns. This helps further reduce the effective cost of the system over time. Depreciation allows taxpayers to deduct a portion of the system’s value from their taxes each year on their tax returns [2].

For agricultural and commercial installations, USDA grants and loans are available through the Rural Energy for America Program (REAP). This can help cover up to 25% of eligible solar costs [3].

Going Solar

Going solar can be a great way to reduce your environmental impact and electricity bills. However, it’s important to weigh the pros and cons before making this major investment.

The process typically involves 5 main steps:

Site evaluation – An installer will visit your home to assess solar potential based on factors like roof space, orientation and shading.

System design – The installer will recommend a system size based on your electricity usage and goals. This is when you’ll get a cost estimate.
Permitting and approvals – Your installer will obtain the necessary permits and submit paperwork to your utility.
Installation – Panels are mounted on your roof and wired to an inverter which converts DC to AC power.

Inspection and interconnection – Local authorities and your utility will inspect the system before final approval.

When exploring residential solar, some key questions to ask installers include:

What are the total costs and incentives available in my area?

How much electricity will the system generate each year?
What warranties and guarantees come with the system?
Who will handle maintenance and repairs?

How long is the payback period for the system?

Going solar can be a big decision, so do your homework to determine if the investment makes sense for you. Reputable installers should provide performance estimates and help you understand the costs and benefits.