How does Solar Panels Store Energy?

How does Solar Panels Store Energy

Solar energy, the energy that the earth receives from the sun throughout the day, is one of the most abundant and green of all renewable energy sources. In fact, it is roughly estimated that an hour of sunlight received on the earth is sufficient to meet the energy needs of the entire world for a year!

Unfortunately, very little of the sunlight falling on the earth is being utilized for that purpose. In the last few decades, when the world woke up to the ill effects of burning fossil fuels and started the search for alternative energy sources, we began tapping into the knowledge of our ancestors in harnessing solar energy.

The initial constraints in using solar energy were overcome by the invention of solar panels and improvements in technology. Let us take a look at how solar panels work.

How do solar panels work?

Sunlight falls on everything on earth similarly. But the way it is used depends on the surface it falls on. Some surfaces absorb more, some less, and some others just deflect. In some materials like silicon, the reaction is totally different. It generates electricity.

When the sun’s rays fall on most objects, including our body, the electrons in the atoms on the surface start vibrating faster, producing heat energy. On the other hand, when sunlight falls on substances such as silicon, the electrons in the atoms on the surface start moving, creating a flow of electrons. In other words, it triggers an electric current.

When sunlight falls on solar panels made of materials like silicon, the electrons absorb solar energy and start moving. This flow of electrons or electric current is captured by tiny wires located within the solar panel and directed to the power inverter. The inverter converts the DC power to usable AC power.

Read about Powering a House with Solar Panels here

What are solar panels made up of?

The older generation of solar panels was made with silicon crystals. The advances in technology have discovered newer materials to improve the usefulness of solar panels. The newer thin-film solar panels use 

  • Cadmium Telluride (CdTe)
  • Gallium Arsenide (GaAs)
  • Copper Indium Gallium Selenide (CIGS)
  • Amorphous Silicon (a-Si)

Compared to silicon crystals, the crystals of these materials are smaller and hence, the panels are thinner. Another important plus point of these new thin-film solar panels is their low cost. However, efficiency-wise, silicon panels are better. While silicon panels are used in domestic and small-scale solar installations, the thin-film panels find their use in commercial projects, spacecraft, and satellites.

Do solar panels store energy?

Not exactly. That was one of the main challenges faced by the solar industry in the initial stages. Solar panels can do the amazing job of producing electricity from one of the most abundant resources on the earth, the sun’s energy. However, at night when the sun is not available to produce electricity or days when the sun’s rays do not reach the earth’s surface, the solar panels are not able to generate electricity. This makes solar panels unreliable and necessitates a backup option. 

Solar developers overcame this hurdle by storing solar energy in batteries or solar energy storage systems. These batteries store solar energy generated for later use. This is an immensely useful addition to the solar installation for domestic users. It helps them to enjoy uninterrupted power supply from solar panels even when the sun is not available or in the events of blackouts and system failure.

Another way of dealing with the problem of intermittent power supply from the solar panels is by hooking up to the grid. Using the arrangement of net metering, users can send the excess energy generated on sunny days to the grid in exchange for credit or cash. And, when the solar panels are unable to meet the energy demand, users can draw electricity from the grid, paying using the credit accrued or in cash.

Being connected to the grid can help in saving on the expense of installing a solar battery. However, energy bills are unavoidable, even though substantially less than before. Solar battery, though an extra installation and expenditure give you freedom from the grid without compromising on the round-the-clock power supply. You may also have both storage methods, solar battery as well as connection to the grid, simultaneously. 

Read about How to Live Off the Grid with No Money here

How long can solar energy be stored?

Solar batteries store the electricity produced by solar panels for later use. The higher the capacity of the battery, the more energy it can store. The efficiency of the solar battery depends on the type of battery installed – lead-acid or lithium-ion. Lead-acid batteries come with a shorter lifespan, lower depth of discharge, and lower efficiency level, while lithium-ion batteries are preferred for better overall performance and lower pollution.

During the storage process, conversion loss is common for both types of batteries. This is the energy lost as heat. This means the electricity stored in the battery will slowly get discharged over time. Conversion loss is less for lithium-ion batteries. Again, how long the batteries will retain the energy stored depends on the type of battery used, the efficiency level, and the age of the battery.

This dilemma can be resolved to a large extent by staying connected to the grid and uploading excess energy to the grid. There is no question of energy loss or the length of time the energy can be stored while doing this. The credit or cash received for the energy uploaded can be used at any point in time later. 

How much do solar panels cost?

An average domestic solar installation in the United States costs in the range of $11,000 and $15,000 after solar tax credits. The average price per watt comes in the range of $2.50 and $3.30. This is calculated for an average system size in the range of 5KW and 7KW.

For a 2 KW system, the cost can be as low as $4,500 and for a 25KW system, the price can soar beyond $50,000.

Read about Why are Solar Panels So Expensive? here

Whether you should opt for a solar battery or stay connected to the grid or have both simultaneously depends on your energy needs, budget, space constraints, and the energy your solar panels can generate. 

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