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Solar energy limitations: the dark side of solar power

In any discussion circle about solar energy limitations, you will hear people arguing about solar panels as the future of power. Usually the conversation has a tone of: silicon photovoltaic solar cells are efficient but very expensive, while organic solar cells are very cheap but inefficient. This is no longer true.

Limitations of solar energy

In this Hourglass article you can check some solar energy limitations like:

  • Solar cells limitations
  • Is solar panels enough to meet our power needs
  • Solar enegy efficiency
  • The dark side of solar power: is it really good for the enironment?

What is the limitation of solar cells?

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Japanese researchers have shown that organic solar cells have a theoretical photoelectric conversion efficiency limit of 21 percent.

This is more than most silicon solar cell panels available today.

The theoretical limit is important because this is the threshold that researchers are chasing – if they believe the threshold is lower, they believe they have reached the limit when there is still room for improvement.

Organic, or plastic, solar cells are made of carbon-based materials.

They can be much cheaper than inorganic solar cells – made of silicon, for example – because they can be manufactured by printing, and can be printed onto flexible, transparent surfaces.

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Solar cells made of silicon – or, more generally, inorganic semiconductors – have a theoretical efficiency limit of 30 percent.

As this limit is about to be reached, researchers have set their sights on building multi-junction solar cells – similar to the path taken by the semiconductor industry, which moved to multicore processors after it became unfeasible to speed up individual processors because of heat.

One multi-junction solar cell recently reached the 44.7 percent efficiency mark, while an even more exotic design reached 50 percent efficiency in the laboratory.

Since 2014, a hybrid solar cell, using organic and inorganic materials, has reached 15% efficiency.

Pure organic solar cells, however, are being manufactured with efficiencies around 10%, which shows that there is a lot of room for technological improvement.

Kazuhiko Seki, the researcher responsible for this project, and his colleagues at the Institute of Advanced Industrial Technologies (AIST) in Japan found that the limits imposed on organic solar cells had been calculated based on inorganic semiconductors.

The new calculations indicated that the energy required for charge separation in these photoelectric cells is -0.4 eV. With this, at a wavelength of 827 nanometers, the efficiency of organic solar cells has jumped to 21 percent.

The new calculations indicated that the energy required for charge separation in these photoelectric cells is -0.4 eV. With this, at a wavelength of 827 nanometers, the efficiency of organic solar cells has jumped to 21 percent.

The dark side of solar power

All energy sources have an impact on the environment. Some have harmful effects, like coal. Others are clean sources of electricity, such as solar energy – but nothing is perfect.

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The most widely used type of solar panels are photovoltaic panels (the kind we are used to seeing on the roof of houses).

It is true that the impact in CO2 generated per kWh is very low, but the production process of solar energy has a trail of environmental destruction that needs to be discussed.

Solar cells are made of silicon, basically the raw material for photovoltaic panels.

Where does the silicon in solar panels come from? Well, they are the result of mining activities.

Silicon is found in rocks, sands, clays, and soils. Mining this substance involves the removal of vegetation, contamination of the soil, eviction of wild animals, and possible contamination of surrounding waters.

Although solar energy is green and renewable, to produce a solar cell requires a great deal of energy – and energy with a devastating CO2 footprint.

The leading country producing solar panels is China, whose energy matrix has a huge dependence on coal (68% of the country’s electricity source), according to the BP Statistical Review.

Solar panels around the world

Besides the pollution generated in the production of solar panels, we need to talk about the distribution of these panels, which is generally done by plane – the means of transport that generates the most carbon dioxide in the world.

When we talk about the photovoltaic panel, the distribution impact is lower. However, the same is not true for solar photothermal energy.

In this case, the implementation of solar panel farms that supply the power plants requires vast areas with high incidence of sunlight, which can also lead to the loss of native vegetation and the formation of degraded areas, causing erosive processes.

This happens because vegetation in a site tends to prevent rainwater, for example, from fully infiltrating the soil. With the removal for the panels, the land becomes much more susceptible to landslides.

The disposal of solar panels

Solar panels last 25 to 30 years, but they can be replaced long before that, becoming waste.

It is common sense in the energy industry that solar panels can be recycled, but poor waste management can lead to the loss of scarce materials that make up each panel (such as copper, silver, gallium), as well as the loss of more common materials (aluminum and glass).

There is also a discussion about the release of toxic substances the disposal of solar panels, such as lead, which is highly toxic.

Before we finish, it is important to remember that all these problems of production and reverse logistics of solar panels need to be discussed, but this energy source is still the best option for a decarbonized economy.

If we take into account the reality in the United States, where 73% of the tons of CO2 emitted annually are generated in the energy sector, it is clear that the urgency of replacing the energy matrix by a green and renewable source.

Is solar energy enough? Solar energy limitations

Maybe you’re exausted of listening all the solar energy advantages, but there are still skpetcism around it, especially about price and efficency.

But recent advances in photovoltaic technology have increased its efficiency and reduced the size of the area needed to install solar panels.

It is a fact that solar energy is better and that is meets our energy needs. So the current advances have raised a curious question, to say the least: could the world have its electricity generated solely from solar radiation?

What are advantages and limitations of solar energy?

Solar energy has many sustainability and financial advantages. Some of the main positive aspects of this renewable energy source are:

  1. it is renewable
  2. It is sustainable
  3. It is clean (50g of carbon per kWh on average)
  4. It is quiet (unlike wind energy)
  5. It is easy to install
  6. It is efficient
  7. It is economical (95% discount on electricity bills)
  8. It is applicable in almost all countries
  9. It is a path to the end of oil
  10. It is resistant (to rain, wind)
  11. It’s recyclable

Some of solar energy limitations are:

  1. It’s still expensive to have
  2. It’s disposal can be harmful for the environment
  3. It’s production process is not yet clean
  4. It’s not the best sollution for some places like Alaska, that has longer winters without sun.

Solar energy as an way out

The solar energy reaching one square mile (which is equivalent to almost 2.5 square kilometers) is equivalent to the energy generated by four million barrels of fossil fuel. In a period of 40 minutes, the energy that hits the planet would be able to meet the world’s demand for energy for one year.

In one year the earth’s atmosphere absorbs about 3.9 million exajoules, which is 7800 times the energy demand of 2013, for example, which was estimated at 500 exajoules (or 500 sextillion joules).

A 53% increase in global energy demand is predicted by 2040, which would total even less than the total amount absorbed by the earth’s atmosphere for one year.

Can solar panels be the main power source?

There are different types of panels that can be used. Each has different applicability and energy conversion efficiencies.

The Silicon Photovoltaic Panel has a low energy conversion efficiency of 15%. This means that only 15% of the received radioactive energy is transformed into electricity. For this reason, to supply the world’s annual demand for energy, it is necessary to install these panels over a very large area, approximately 662.4 km², larger than the combined area of Spain and Portugal.

The thin membrane photovoltaic cell panel, on the other hand, is cheaper and easier to produce.

It has a higher energy conversion efficiency (19.2%), and thus would occupy a smaller (but still significant) area to supply the demand, which is approximately 507.5 km² (larger than Thailand).

The panels, if installed in five thousand different places with about 25 to 30 panels per country, could achieve an effective solution to the energy demand.

However, many countries do not have enough area for silicon cell panels or concentrated photovoltaic cells, leaving thin membrane panels as the only option.

The ideal location for the use of the other two types of panels are uninhabited deserts because they have ample area and radiation incidence rate. Of the world’s largest projects in the last decade, eight of them are in California, Arizona and Nevada.

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