How Does Solar Work?

Solar Radiation Conversion

Solar energy conversion is the efficient conversion of solar radiation, and at its core is a fundamental process that solar energy has been using for decades – converting sunlight into electricity through photovoltaic cells. The average efficiency of solar panels currently sold is 15% to 22%.

New materials such as perovskites can provide laboratory efficiencies of up to 31%. First Solar has commercialized thin-film solar cells with an average efficiency of about 18%, which is stronger than traditional silicon-based panels.

Grid Integration and Energy Storage

Successfully interconnecting solar energy to the grid often requires the use of energy storage systems. The Hornsdale Power Reserve in South Australia uses Tesla's battery pack to provide 129 MWh of storage capacity, and the system has saved about $116 million in grid service costs.

India - Pavagada Solar Park: With a capacity of 2,050 MW (enough to power more than 700,000 homes) covering 13,000 acres, this solar park in Karnataka, India, is one of the largest solar parks in the world.

As solar systems become more common in rural areas, the demand for portable solar solutions is also increasing. Solar-powered drones for environmental monitoring can fly above clouds, soaking up sunlight 24/7, and flying for days or weeks at a time - demonstrating the capabilities of efficient batteries in aviation applications.

The transportation sector is integrating solar energy in an out-of-the-box way, with how the Solar Plane 2 flew around the world, powered entirely by sunlight. Its wings and fuselage are covered with a total of 17,248 solar cells, allowing the aircraft to fly day and night without the need for fuel.

PV System Components

Solar photovoltaic panels consist of multiple solar cells made of silicon, which convert sunlight into electricity. For example, in a typical home installation, you can now use panels rated at 300 watts, combining them to form a system that is close to your daily energy needs of about 5 kilowatts per hour, a configuration that can reduce your home energy bill by more than 50% per year.

In modern applications, it is possible to convert electricity, fine-tune energy output and have grid management functions. Some products in the SMA Sunny Boy inverter series can have efficiencies of up to 97.5%.

Solar panel support frames, which are used to fix solar panels to the roof or ground, and can protect against environmental influences such as wind or snow. Designs vary depending on the type of installation, but may include adjustable tilt brackets, or in some cases tracking brackets, where the solar panels will follow the sun during its daily cycle.

They capture and store any excess solar energy, for example, the Tesla Powerwall is now home, which can store up to 13.5 kWh of electricity - enough to meet your power needs (up to 4 kW continuous).

They can also identify inefficiencies or malfunctions and notify owners and installers when urgent attention is needed. The Enphase Envoy monitoring system is a great example of this, as it allows users to check their power generation via a smartphone app.

CSP Technology

CSP technologies can be broken down into:

• Parabolic troughs: These systems are able to heat sunlight to temperatures of 400o C. The SEGS plant in California's Mojave Desert demonstrates this technology, and they produce a total of about 354MW.
• Solar towers: These can produce temperatures of up to 1,000°C - higher than what troughs can produce. An example is the Ivanpah Solar Power Plant in Nevada, which produces 392MW.
• Dish/engine systems: Each dish mirror can produce up to 25 kW of electricity and operates at about 30% efficiency, making it the best performing of the CSP technologies.
• Fresnel reflectors: More like parabolic troughs, but they use horizontal (flat) or slightly curved mirrors at different angles to focus sunlight onto a longitudinal linear receiver.

CSP systems are the only solar power plants that can store energy as heat. The collected sunlight is converted into heat, which heats these materials (such as molten salts), which can also generate electricity. Solana Generating Station in Arizona has similar molten salt storage capacity and can provide six hours of electricity even after sunset, with a total output of up to 280 MW.

Practical Applications

In industry, some companies (cement and steel) use CSP technology to generate very high temperatures. Desalination: CSP powers our desalination plants. Using CSP to enhance oil recovery: When steam is injected into underground oil fields, the high temperature heats and reduces the viscosity of heavy crude oil, making it less dense (unlike tar), which makes it easier to extract light crude oil from the well. At the Coalinga solar power plant in California, steam generated by CSP is also used for oil recovery, reflecting the synergy of renewable fossil fuels from a different perspective.

Solar Grid Integration

12 Jun 2018 Grid-tie inverters are how you connect your solar array to the grid, converting the direct current (DC) from your solar panels into alternating current (AC) that you can use on the grid. The SMA Sunny Tripower series, for example, can convert solar energy to an AC waveform that aligns with the grid’s - and output that conversion at up to 98.5% efficiency.

For example, California has a state law called “net energy metering” where homeowners can get a credit on their electricity bill for any extra electricity their system generates that is fed back into the grid at the retail price. In Germany, feed-in tariffs (FITs) offer solar producers guaranteed long-term power contracts at a price per kilowatt-hour of electricity generated that is above the market price, which has incentivized widespread adoption of the technology.

These systems can provide real-time balancing of supply and demand, supporting grid reliability, and Tesla Autobidder software, for example, can be used to enable autonomous power trading and real-time balancing, providing greater levels of economic and energy efficiency.

The tool to achieve this across the U.S. could be a slew of projects, such as the 550-megawatt Topaz Solar Farm in California, one of several plants in Agua Caliente capable of serving hundreds and thousands of homes simultaneously.

These programs typically regulate power consumption by grid-connected devices during times of peak solar production to align energy delivery with demand to avoid overloads and maximize efficiency.

Solar Efficiency Advances

Solar cell technology has been well funded in R&D, with multi-junction solar cells being one example, which in 2016 achieved efficiencies of over 40% in concentrated sunlight, compared to the paltry 15-20% for regular silicon cells.

Perovskite solar cells are an emerging technology with efficiencies of up to 25%.

Bifacial solar panels can capture sunlight on both sides of the panel, producing 30% more energy than conventional single-sided solar panels.

Optimizing solar systems with AI and machine learning These can manifest as being able to predict solar power generation based on weather, and dynamically adjust panel orientation for optimal capture. For example, Google’s Sunroof project uses machine learning to analyze the shape of local rooftops and weather to determine if solar energy is available in the area.

Thermophotovoltaic (TPV) cells are used with concentrated solar systems operating at high temperatures, and in principle can achieve efficiencies of over 50%.