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Jul 13 2018
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How Solar Panels Absorb and Store Energy

By How Does Solar Power Work on a House? Your Questions Answered No Comments

 

The sun’s energy is expressed in different ways, depending on what materials it interacts with.

Solar panels are built with materials that physically interact with certain wavelengths of solar energy. This enables them to transform solar energy into electricity. Here’s how solar panels absorb and store energy.

What’s in a solar panel?

Traditional solar panels are made with silicon crystals. Silicon is a very special material. It creates an electrical current with sunlight. This is because of the electrons making up a silicon atom.

When sunlight hits your skin, the electrons in the atoms of your body vibrate quickly to generate heat. But electrons do something different in silicon. The electrons start moving around. This means that the sun’s energy is conducted into an electrical current, rather than static heat.

Newer, thin film solar panels function in a similar way. Rather than silicon, they’re made with

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

Crystals made from these are smaller and less expensive to produce. Though, they’re not quite as good at producing electricity as silicon. Thin film solar panels are used more for commercial projects, on satellites and spacecraft.

Thin-Film-Solar-Cells

With either the silicon or thin film solar cells absorbing the sun’s light, the electrons do their thing. They’re bumped up to a higher level of energy and get active. Once that higher energy level is reached, it’s up to us to capture and direct the electricity where we can use it.

A series of tiny wires creates a network of electrical current-conducting “mini highways” within a solar panel. These all tie back to a power inverter. Inverters change the raw electric current from DC power to AC power. Your home is wired to conduct AC power, so inverters essentially make the electricity usable.

Do Solar Panels Store Energy?

In short, no they don’t. This has been one of the biggest challenges for solar developers. While it’s great to generate clean electricity, days with less sun and lower production might mean you have to tap into the power grid anyway. But there are options.

Many states offer net metering, which allows you to sell any excess energy you produce on sunny days to the utility company for credit. Then when those rainy days come along (or at night), you can pull power from the grid with those points you racked up.

Solar Batteries to Store Extra Energy

Battery storage is another option for storing solar energy. Companies such as Tesla, LG, and sonnenBatterie are producing batteries that make solar plus storage for homeowners more available. Batteries give the option of more independence from the grid. You can pull energy from your battery at night, rather than switching to utility power when the sun stops shining.

Battery backup also comes in handy in cases of power blackouts. You could run your appliances and electronics using a solar battery for a day or two. That’s generally enough time for your utility to get things up and running again. Of course, your solar panels will kick back in when it’s sunny as well, giving your battery a break.

Learn more about using a solar battery backup during a power outage here. Explore more about how solar might fit your home by punching in your address here.

Jul 12 2018
Love0

Perovskite and Silicon Solar Cell Efficiency Reaches 25.2%

By Solar Panel Efficiency - Pick the Most Efficient Solar Panels No Comments

While around 90% of solar panels currently on the market are made out of silicon, adding a new material may soon make existing module design even more efficient.

Perovskites are a cheap class of materials that can easily be combined with silicon for more efficient electricity generation. Perovskite cells have come a long way since 2009 when they boasted an efficiency of just 3.8% for a few minutes. The most advanced perovskite cells “now boast an efficiency of 22.7% and routinely work for thousands of hours under harsh test conditions,” according to recently published research.

The most recent breakthrough stems from a new method of combining the silicon-based and perovskite cells. Silicon-based cells have a surface made up of microscopic pyramids, which has historically made placing a homogeneous perovskite sheet on top difficult.

According to Swiss Researcher Florent Sahli, “Until now, the standard approach for making a perovskite/silicon tandem cell was to level off the pyramids of the silicon cell, which decreased its optical properties and therefore its performance, before depositing the perovskite cell on top of it. It also added steps to the manufacturing process.”

Sahli and his team’s new process uses evaporation technology to create an inorganic substance that surrounds the pyramids and allows for easier placement of the perovskite layer. While the technology is not yet commercially available, it is currently undergoing tests to increase efficiency as well as the long-term stability of the perovskite film.

Perovskite and Silicon Tandem Cells: A Perfect Pairing

Like silicon solar cells, modules made solely out of perovskite are possible. However, researchers have begun focusing on “tandem solar cells,” which feature a thin layer of perovskite cells – about one micrometer thick – on top of a layer of silicon-based cells.

While silicon is best at converting red and infrared light into electricity, perovskite is more efficient with green and blue lights. The resulting combination recently reached a record efficiency of 25.2%. However, researchers believe that efficiencies beyond 30% are possible in the near future. 

Perovskite-Silicon Tandem Cell

(Pictured: Tandem Cell Model from source)

This new research comes at a critical moment for technology in the solar industry. Advancements are continuously being made to boost efficiency and reduce prices, but many believe that silicon solar cell technology is starting to flatline after decades of success.

While challenging, the widely recognized theoretical maximum efficiency for silicon-based solar cells is 29.4%. As researchers draw nearer to this limit, tandem solar cells offer the realistic possibility of exceeding this cap. According to the Swiss research team, integrating perovskite cells on top of silicon-based cells “would only add a few extra steps to the current silicon-cell production process, and the cost would be reasonable.”

Better yet, the materials needed to create perovskite cells are relatively abundant. Tandem solar cells and their potential hold certainly offer a lot to get excited about!

Should you wait for tandem cells to go solar?

Although the potential for perovskite-silicon cells are great, consider going solar soon to maximize your savings on your electricity costs. It will likely still be a few years before tandem cells are commercially available at a wide scale.

What’s more, unless you have extremely limited roof space to place solar panels, the efficiency of standard solar panels are already at a high enough level to cost-effectively install an array.

To learn more about your home on solar, use our calculator to get an instant snapshot of what solar would look like for your home.