Why Are Solar Panels Rectangular Or Square?

Why Are Solar Panels Rectangular - featured image

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Think about all the solar panels you have ever seen and it will dawn on you that they all have something in common – they are all rectangular. Why would that be?

As a general rule monocrystalline solar panels are rectangular because of the way that the solar cells are manufactured. They are cut in thin slices from an ingot of silicon with a wide diameter, and then are cut into squares. 

This is the most efficient way for the solar cells to be grouped and the reason why solar cell squares have slightly rounded corners.

It’s obvious that in some locations and nice, flowing biomorphic shape would fit in very well. Currently, the only way to do that is to approximate a round shape by fitting together smaller square sections of groups of solar cells.

Why Are Solar Panels Rectangular?

Polycrystalline solar cells are are cut from silicon crystal and don’t have the corners cut off. However, the rectangular shape is kept because:

  1. a square is easier to cut
  2. a rectangle is the most efficient form for packing cells together into a solar panel
Why are solar cells cut in squares?

           Left – polycrystal cell rectangle              Right – monocrystalline with corners cut off

Why are solar panels so expensive?

Solar panels are expensive because of the complex manufacturing process needed to create them. All solar panels require very thin slices of silicon which have to be precision-cut using CNC (digitally controlled) machines. In addition, the fabrication process involves fixing tiny bus-bars and wires to each individual cell.

The complete solar system includes the solar panels, mounting rails, one or more inverters, cabling and junction boxes, monitoring and net-metering equipment. The cost of the solar panels make up about 34% of the whole cost – see the table below:

Solar Panels

34%

Mounting

5%

Inverter(s)

10%

Labor

15%

Overheads/profit

33%

Permits & Inspections

3%

Labor accounts for another 33% of the overall costs and it’s normal that the contractor/installer makes a profit on the solar panels purchase, often bought in bulk. Its possible to save up to 50% of the cost of a solar installation by installing it yourself.

Why have solar panels dropped in price?

Solar panels have dropped in price due to improvements in the manufacturing process and increasing global production capacity spurred on by an increase in global demand. The cost of having domestic solar installed has reduced by almost 89% since 1980.

Why are solar panels getting cheaper?

Not so many years ago it was unheard of to propose building large-scale solar plants for electricity generation. The main reason was that investors could not earn a big enough reward for their investment. In fact, at one time it was almost twice as expensive to build a solar energy plant than coal or gas.

This situation has completely turned around. It is now very much cheaper to install hundreds of solar panels and enjoy cheap electricity. Whether this will happen remains to be seen, but it’s a great dream. If Elon Musk has his way, the deserts of America will be carpeted with solar panels and fields of batteries connected up to the grid for times of power outage.

Why are solar panels black?

Are solar panels black or blue?

Most solar panels are not black, but a bluish-silvery color due to the nature of the silicon crystal the solar cells are made of. A relatively small percentage of solar panels are made from monocrystalline cells which have a much darker appearance, often appearing black due to the manufacturing process and material used.

Silicon ingots used for solar cells

Why solar panels are black or blue – Courtesy

Polycrystalline solar cells are cut from a large block of silicon which has been melted and poured into a mould. The crystals are not aligned with each other and when hardened give a bluish tint under sunlight.

Monocrystalline solar cells are cut in thin slices from a solid ingot that is grown in a tank. Natural growth aligns silicon crystals so that they reflect sunlight in a different way, appearing darker. The dark appearance of monocrystalline solar cells also helps to make them more efficient, as darker surfaces absorb more light.

 

Why are solar panels so inefficient?

Solar panels are so efficient for two major reasons. Solar cells can only convert a relatively small wavelength band of visible light into electrical energy and silicon also converts some of the light energy into heat. Many conversion devices and machines do not have a high efficiency, but a notable exception is solar thermal, which boasts efficiency rates of up to 80%.

Polycrystalline solar cells are by far the most common for residential solar installations, but are not quite as efficient as monocrystalline. The table below shows the comparable efficiencies of common solar panel types:

Characteristics

Monocrystalline

Polycrystalline

Thin Film (amorphous)

Composition

One crystal

Multiple crystals

Thin silicon layers

Color

Black

Blue

Multiple - varies

Efficiency

17 to 23%

10 to 14%

5 to 6%

Lifetime Duration

25 to 30 years

20 to 25 years

15 to 20 years

Manufacturing Process

Complicated

Easier

Complicated

Cost

Expensive

Cheaper

Expensive

Temperature Tolerance

0 to 5%

-15 to +5%

-3 to +3%

There are several methods employed to try and improve solar panel efficiency, namely:

  • mirrors
  • concentrators
  • cooling (heat reduces efficiency)
  • sun-tracking (optimizes orientation and tilt angle)
  • regular cleaning
  • using MPP (maximum power point) technology for charges and inverters

Why can’t solar panels work at night?

Solar panels cannot work at night because any light available is too weak to convert into a meaningful quantity of electrical power. Artificial light can trigger the conversion, but at a much reduced rate compared to sunlight. Moonlight is 10 million times weaker than bright sunshine.

It would be ideal if solar panels were capable of storing electrical energy but this is not possible. For the foreseeable future, they will depend exclusively on natural sunlight to generate electricity.

Why solar panels can't work at night

Why do solar panels degrade?

Solar panels degrade because of UV exposure, which reduces the energy conversion capabilities of the silicon crystal junctions, and the effects of environmental conditions. Alternating extreme temperature variations stress and degrade solar cell wafers that are becoming ever thinner, and also fracture thin bus-bars and connections between the cells.

Everything that exists degrades – solar panels are no exception. Solar panel manufacturers give certain guarantees for panels, specifying not only the output at a certain value of irradiance (1000kWh/m2), but also what the output will be in 10 or 20 years. This is called the STC standard.

For example, a manufacturer might write that their solar panel will maintain at least 90% of it’s output when new after 10 years, and then 80% after 20 years. In fact, solar panels take a long, long time to stop working completely and will probably still be generating power 50 years after installation.

Why do solar panels degrade?

Can solar panels be recycled?

Solar panels can be recycled but the process is not trouble free. Up to 90% of solar panel construction is glass and the rest is plastic plus silicon, which is doped with impurities such as arsenic. Solar panel glass also contains impurities and is difficult to purify to use as float glass for domestic or commercial purposes.

The whole subject is going to be a very hot topic in 25 years, as that is when the solar installations going in now will be ready to dismantle.

By that time I hope that the recycling technology has improved so much that they can simply be converted right back into electricity-generating solar cells, but I wouldn’t hold your breath.

Why do solar panels face south?

Solar panels face South in the Northern hemisphere because that is the direction in which the sun traverses the sky from East to West. The sun rises in the East and tracks across the sky to set in the West. During this time it also rises in the sky before falling back at the end of the day.

Solar panels should be pointed directly at the sun, that is, perpendicular or 90 degrees to it. An automatic system that ensures this is called a solar-tracker and there are two varieties.

A solar tracking device that follows the sun across the sky in the horizontal plane is known as a single-axis tracker. This style of tracker makes significant gains in overall power output.

A device which also follows the sun up and down the vertical plane is called a dual-axis tracker. The sun’s vertical travel is not so pronounced, and so the gains are less if only this axis were used. A dual-axis tracker can improve solar panels output by up to 40% but it can cost 30% of the total installation’s capital cost.

A single axis solar tracker facing South

Why do solar panels lose efficiency with heat?

Solar panels lose efficiency with heat due to the increased excitation and electron movement within the solar cell’s silicon crystal. Electrical current is a mass movement of electrons and when electrons get hotter, they move around more and more. This means there are less of them to form electric currents and the panel’s efficiency reduces.

It’s quite a paradox. Solar panels need strong, bright sunshine in order to generate electricity but this also generates heat, which diminishes electricity generation. The loss  in efficiency is minimal until the solar cell reaches a temperature of 77 degrees F (25 degrees C).

For every degree after this temperature, the panel’s efficiency reduces by between 0.35 to 0.5. This called the panel’s temperature coefficient and is express as -0.35, for example.

Why do solar panels need batteries?

Solar panels need batteries if they are used to provide electrical power at times when the sun doesn’t shine. If a solar system has batteries but no grid connection it is known as on off-grid solar installation. A home energy storage battery bank can be used with solar panels to protect against power outages.

Tesla batterioes used with solar panels

Residential solar systems come in two flavors – grid-tie or off-grid. Grid-tie systems are connected to the utility grid and can feed power back into the grid if they have a surplus. This is great, because home-owners get paid for it. However, there’s currently some doubt if this practice will continue in its current form.

An off-grid system doesn’t connect to the grid so the home-owners has to make do with what he has. Inevitably, this means providing electricity during those periods when there is no sunlight, either on a cloudy day, at night or during a power outage.

In this case a substantial bank of batteries is required. They are charged during the day when there is  a surplus of production and discharged during the night, or outage, as needed.

It’s important to size the system accordingly so that the amount of insolation (irradiance over time) available in the location and size of the battery bank are sufficient to feed the home overnight, or for extended periods of blackout.

Why have solar panels?

The advantages of having solar panels installed are many:

  • grid-tie system allow sell-back to the utility company
  • an off-grid system can make you independent of said utility company (almost)
  • a solar system immediately adds value to your home’s re-sale price (4% on average)
  • solar is an energy generation system that lasts for 25 years on average
  • almost maintenance free (cleaning required twice a year)
  • non-polluting (until re-cycle time approaches – 30 to 40 years)
  • use to charge your electric car
  • use less of the planet’s resources, such as coal and gas (power stations use these)
  • makes the grid more secure (domestic solar systems feed into, and stabilize, the grid)
  • have extra power for your peak demand times
  • store the extra power in batteries
  • helps creates jobs (it has the biggest job sector growth in the US 2020)
  • saves water (conventional power plants use gallons of water)

Related Questions:

Do solar panels have to be square?

As a general rule solar panels need to be square to make the best use of space for arranging the solar cells, and also fixing the bus-bar connections.

Do solar panels work in the shade?

Solar panels work in the shade but to a much lessor extent. They are most efficient when under direct strong sunlight.

Why are solar panels flat?

As a general rule rigid, fixed solar panels are flat as they are covered in tempered glass for protection and are generally mounted on flat surfaces such as roofs. Flexible solar panels that can be bent exist for different applications and situations.

Why haven’t we covered all the roofs with solar panels?

On average the area covered by a typical home is much too big to be covered in solar panels. The cost would be too great and unnecessary to cover the power needs of most households.


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