What Power Does Solar Produce?
Solar power has emerged as a critical renewable energy source worldwide. As concerns about climate change and dependence on fossil fuels mounts, nations around the globe are looking to the sun to meet growing energy demands in a sustainable manner. With costs falling and efficiencies rising, solar energy capacity is rapidly increasing and represents a technological bright spot providing clean and abundant energy.
This article will provide an in-depth look at how solar power works, the factors affecting its productivity, solar energy storage, costs, and the future outlook. Whether you are interested in powering your own home with solar panels or just want to better understand this increasingly important technology, this overview covers the key aspects of harnessing the sun’s rays for energy.
How Solar Panels Work
Solar panels work through the photovoltaic effect, which is the process of converting sunlight into electricity. Solar cells inside solar panels are made of semiconducting materials like silicon that are specially treated to form an electric field. When sunlight hits these solar cells, the photons from the sunlight energize the electrons in the semiconductor material, causing them to break free of their atoms and flow through the electric field, producing electricity.
The photovoltaic effect was first discovered in 1839 by French physicist Edmond Becquerel. It works because when photons from sunlight hit the solar cell, they transfer their energy to the electrons in the cell, causing voltage and electric current. The electrons can then be captured and used as electricity. The more sunlight that hits a solar panel, the more electricity it can produce.
The solar cells are wired together to form larger units called modules or panels. These are then connected together to form solar panel systems or arrays that can be installed on rooftops or the ground to convert sunlight into useful electricity on a larger scale. Understanding how solar panels leverage the photovoltaic effect to convert sunlight into clean, renewable electricity helps illustrate why they are becoming so widespread as an energy source.
Solar Irradiance
Solar irradiance refers to the amount of solar power per unit area that reaches the Earth’s atmosphere. It is measured in watts per square meter (W/m2). The solar constant, the amount of incoming solar irradiance per unit area on a surface perpendicular to the sunlight outside the atmosphere, is about 1,370 W/m2. This means that at any moment, each square meter of the top of the atmosphere receives 1,370 joules of energy per second from the Sun.
However, because the Earth has an atmosphere, not all of this solar irradiance reaches the Earth’s surface. About 30% is reflected back into space by clouds, while another 20% is absorbed by clouds, gases and aerosols in the atmosphere. This means that at sea level on a clear day, solar irradiance is reduced to about 1,000 W/m2. The actual amount of irradiance varies based on location, time of day, season, and local climate conditions.
In total, Earth receives 174 petawatts (174 million billion watts) of incoming solar radiation at the upper atmosphere. About 30% is reflected back to space while the rest is absorbed by the land masses, oceans and atmosphere. This absorbed solar energy is what powers the climate and weather and sustains life on Earth.
Factors Affecting Solar Output
There are several key factors that affect how much power solar panels can produce at any given time. These include:
Solar Panel Orientation
The orientation of solar panels is critical for maximizing energy production. Solar panels should face true south in the northern hemisphere, with no shade covering them between 9am and 3pm. Tilting solar panels at an angle equal to your latitude will optimize energy capture. Even small adjustments to orientation can make a big difference in energy output over the course of a year.
Cloud Cover
Clouds block incoming sunlight, reducing the solar energy that reaches panels. Solar output can fall by 80% or more on an overcast day. Even on partly cloudy days, power output can fluctuate significantly when clouds pass over. Sites with historically fewer cloudy days will generate more total solar energy.
Time of Day and Year
The sun is highest in the sky at noon, when solar irradiance is strongest. Output falls off before 9am and after 3pm. Seasonally, solar production peaks on the summer solstice and reaches its minimum on the winter solstice. Locations farther from the equator see wider variations in solar output across the seasons.
Solar Panel Efficiency
Solar panel efficiency refers to the percentage of sunlight that hits the panel and is converted into electricity. The efficiency rating represents the ratio of the power output of the panel compared to the amount of sunlight incident upon it.
There are several factors that affect solar panel efficiency including the solar cell material, panel surface area, the angle sunlight hits the panel, temperature, and more. Panel manufacturers aim to maximize efficiency to generate more electricity from the same amount of sunlight.
Different solar panel types have differing efficiency ranges. For example:
- Monocrystalline panels – 15-22% efficiency
- Polycrystalline panels – 13-17% efficiency
- Thin film panels – 7-13% efficiency
Monocrystalline silicon cells are the most efficient panels commercially available today, with lab prototypes reaching over 27% efficiency. However, mono panels are also more expensive than other options. Polycrystalline panels are slightly less efficient but cheaper. Thin film panels have the lowest efficiency rating but can be the most affordable option.
When deciding which solar panel type to install, homeowners must balance efficiency vs. cost to find the optimal system for their needs and budget. More efficient panels will produce more electricity, but less efficient low-cost options can still provide significant power generation.
Measuring Solar Power Production
Solar power production is typically measured in kilowatt-hours (kWh), which represents the amount of energy generated over time. For example, a 5 kW solar system operating at full capacity for 5 hours would produce 25 kWh of energy (5 kW x 5 hours = 25 kWh).
For residential solar systems, production is tracked daily, monthly and annually to determine the total energy output. This allows homeowners to estimate potential cost savings on their utility bills. On average, a typical 5 kW home solar system in the U.S. produces about 6,000-6,500 kWh per year. However, actual production depends on several factors like your location, roof orientation, panel efficiency and local weather patterns.
Monitoring systems provide real-time production data and historical performance. For example, a south-facing 5 kW system in Arizona may produce 30 kWh on a sunny day in July but only 15 kWh on a cloudy day in January. Reviewing these production reports helps homeowners understand how their system is performing over time.
Solar Power Storage
Battery storage plays a key role in harnessing solar power when the sun is not shining. Most solar systems connect to the electric grid, feeding excess generated electricity into the grid during the day and pulling from the grid when solar production is insufficient. However, adding battery storage allows solar system owners to store excess production for use at night. This increases energy independence and resilience.
Common battery types used for home solar storage include:
- Lead-acid batteries – Inexpensive but short-lived option.
- Lithium-ion batteries – More expensive but longer lifetime and no maintenance.
- Saltwater batteries – Emerging technology using saltwater electrolytes.
- Flow batteries – Store energy in external electrolyte tanks for more flexible capacity.
Battery storage capacity ranges from modest overnight power needs to completely off-grid systems. Determining optimal solar battery size depends on energy usage, grid electricity rates, and backup needs during outages. Though batteries add cost, prices are dropping, and storage is key for maximizing solar power utilization.
Feeding into the Grid
When a solar panel system produces more electricity than a home or business can use, the excess solar power is fed back into the electrical grid. This is known as net metering, which allows solar panel owners to get credit for the excess electricity they generate. The utility company keeps track of how much electricity is used vs. how much is fed back into the grid, and the solar customer is billed only for their net energy use.
Net metering provides a major incentive for installing solar panels. Without it, any excess solar electricity would simply be wasted. But with net metering, solar panel owners can reduce their energy bills and even get paid for generating extra renewable energy.
Many states and utility companies offer net metering programs to compensate solar customers at the retail electricity rate. So feeding excess solar power back into the grid offsets the electricity they would otherwise have to purchase from the utility at that rate. This makes going solar much more financially beneficial.
Some areas provide additional incentives on top of net metering, such as renewable energy credits (RECs). RECs provide solar panel owners with payments for the clean energy they produce, providing further financial rewards for generating renewable solar power.
So net metering policies and solar incentives make it possible to generate income from a solar array when it produces more than the building’s energy needs. This excess clean power gets fed into the grid for others to use.
Solar Costs
The cost of a solar system for a home or business has declined significantly over the past decade. In 2010, the average cost of a residential solar system was over $7 per watt. Today, costs have fallen below $3 per watt on average.
There are several factors driving down the costs of solar panels and installation:
- Improved solar panel efficiency – panels can now generate more electricity using less silicon.
- Economies of scale – Increased demand has led to larger manufacturing capabilities and supply chain improvements.
- Stronger competition – Hundreds of solar companies are now competing for business, driving down pricing.
- Lower “soft” costs – Permitting, inspection, financing and installation costs have also declined.
The sharp decline in solar costs means the payback period on a system is now only 4-7 years for most homeowners. And over a 20-year lifespan, a typical system can save tens of thousands in electricity costs compared to utility rates.
Businesses can see even faster payback and more significant long-term cost savings by going solar. With solar already at grid parity in most US states, the economic case will continue improving in the years ahead.
Future of Solar
The future looks bright for solar power. As technology continues to advance, solar panels are becoming even more efficient and affordable. Many experts predict that solar will continue its rapid growth and play a major role in the world’s energy future.
Research shows that solar power capacity could grow by as much as 8-fold by 2050, accounting for up to 30% of global electricity generation. The International Renewable Energy Agency predicts solar capacity growth of over 1750 gigawatts within the next 5 years. This incredible growth will be fueled by both large-scale solar farms as well as distributed home and business installations.
Innovations in solar cell technology, energy storage, and manufacturing processes will also drive down costs and improve efficiency at an astonishing rate. Companies are developing new solar cell designs, novel materials like perovskites, and integrating solar into building materials. Energy storage solutions like batteries continue improving to better store and utilize solar energy. Automation and streamlining of manufacturing is making solar more affordable than ever.
With such immense growth and innovation on the horizon, solar is expected to play a major role in reducing greenhouse gas emissions and enabling a clean energy future. The limitless potential of solar power will continue to be harnessed in new and exciting ways, providing clean electricity across the globe.
