Tag: sun

How effective are solar panels in northern latitudes?

Solar panels are more effective in colder weather.

…wait, really?

Yes, really. But first, the basics…

How latitude affects efficiency of solar panels

Solar energy is not equally distributed across the Earth.

Although plenty of northern regions get a lot of sun, it would seem that in general, solar panels are less effective the further north you go.

Why is this?

Angle of solar impact

The Southern Hemisphere receives more energy during December (southern summer) than the Northern Hemisphere does in June (northern summer) because Earth’s orbit is tilted. [8]

Optimal Solar Panel Tilt Angle Calculator - SolarSena
source: SolarSena

One factor influencing solar radiation intensity is the angle of impact. For harvesting solar energy from cells, the optimal angular impact is 90 degrees perpendicular.

In northern latitudes, because because the angle of impact is less direct than it is at the equator, it is spread over a greater surface area and therefore you get a less concentrated energy output per unit area.

And unfortunately, this also means that solar panels are less effective during the months that Earth is tilted away from the Sun, during the winter months.

To make up for this, solar panels are often tilted based on the location on Earth as well as time of year.

The angular tilt of solar panels to maximize efficiency is greater the further north you go as well.

In addition to the sun’s rays being spread over a wider surface area, there is a second factor that latitude influences.

Absorption scattering of UV rays

As we see in Figure 1 below, the distance that solar radiation must travel through the atmosphere is further.

A wider band of atmosphere through which the rays pass means there is more absorption scattering of sunlight in the atmosphere.

UV rays comes into contact with the nitrogen, oxygen, carbon dioxide, and other gases in the atmosphere over a wider area, so more is absorbed.

Figure 1: source, hong kong obervatory

Because a large amount of UV rays have been scattered and absorbed, they are less intense once they reach Earth’s surface

The combination of absorption scattering in the atmosphere as well as the angle of impact suggest that in general, we would expect solar panels to be less efficient during the winter time in each respective hemisphere.

Climate conditions affect solar cell performance more than expected
Figure 2: deltaPR on the y-axis represents change in Performance Ratio throughout the months of the year (summer, fall, winter, spring). PR measures how effectively the photovoltaic panels convert sunlight into energy. [3] photo/gift from phys.org [2].

However, as mentioned at the beginning of this post, there is a third factor that influences solar panel efficiency – temperature.

Solar panel efficiency in cold temperatures

Yes, cold weather does increase the efficiency of solar cells, if everything else is constant. [9]

This means that cold weather (with sunshine) are the ideal conditions for solar cells.

The reason is that low temperatures decrease the solar cells’ internal energy leakage.

In cold temperatures, electrons are less active. At higher temperatures, electrons are more active.

With lower electron activity, energy can be stored and moved across wires and batteries more efficiently. [1]

According to phys.org, solar cell efficiency decreases by 0.3% for each temperature degree increased. [1]

This means that a warmer region, while perhaps sunnier, is not necessarily going to be an optimum place for solar energy generation.

This is good news for the northern regions of Earth.

While northern latitudes may be at a disadvantage for reasons based on the first two factors mentioned the earlier section of this post, we can make the case for solar energy in cold, sunny places!

Of course, snow and ice can be a problem for solar panels, and attempting to scrape it off could damage or break the components.

If the ice is translucent, the solar panels may be able to generate a continued output of energy.

Solar in Germany

Germany is the leading country in Europe for solar deployments.

Germany is further North than most people realize. Berlin, Germany occupies the latitudinal region of 52 degrees N (Berlin).

Climate Zones Map Scheme Vector Illustration Equatorial Tropical Polar  Subtropical Stock Vector Image by ©Vector.Plus #419957486
Figure 3: Earth’s climate regions based on latitude.

By comparison, the latitude of Calgary, Canada is around 51 degrees N.

It is inspiring to see a country as far north as Germany have so much success with solar, and Germany should perhaps serve as a model for other nations.

If a northern, Temperate country like Germany can prove the viability of solar, surely countries further south can too, with even greater ease.

Still, we’re not at 100% sustainable energy yet.

In order to meet 100% of its electricity needs with solar, Germany would need to significantly increase its solar photovoltaic capacity to between 303 GW and 446 GW.

Given the three factors covered above that impact solar panel efficiency, equatorial areas are not necessarily going to be the only places (or even the best) where solar will work.

Conclusion

Eventually, the world will need to transition to 100% sustainable energy. We cannot survive off of fossil fuels and coal forever, as these reserves will eventually run out.

This post isn’t meant to provide a more realistic approach and help people understand how solar can help while supplementing other energy sources in order to maximize the amount of sustainable energy for the grid. It should be mentioned that wind, nuclear energy, hydroelectric, and more could also help transition the world to sustainable energy.

For example, as solar is added to the grid, it reduces the net demand for electricity in the middle part of the day (when the sun is most radiant).

Figure 4: Based on data over a 72 hour period, solar energy is able to account for a the largest portion of energy demand during the middle of the day, when the sun is most intense. [6]

And if we assume there is no storage of excess energy during peak hours, solar output during the night is pretty much zero.

Perhaps off-grid regions of the world, such as research bases in Antarctica or remote areas of Alaska, could fulfill their own power demands via solar systems during the summer. [7]

For now, perhaps solar energy could be a viable way to reduce diesel, at least during the daytime.

With improvements in battery technology paired with a greater number of solar panels across the globe, perhaps humans can one day capture and store enough solar energy that we can sustain our energy requirements all hours of the day and night.

And if land is abundant, as it is in the United States, perhaps the most reasonable way to increase the percentage of renewable energy that we consume is to simply build more solar panels.

Sources

  1. https://phys.org/news/2018-03-solar-cells-nordic-climate.html
  2. https://phys.org/news/2017-12-climate-conditions-affect-solar-cell.html
  3. PR aka Performance Ratio for photovoltaic performance https://www.nrel.gov/docs/fy13osti/57991.pdf
  4. hong kong observatory http://www.hko.gov.hk/en/education/edu06nature/ele_srad.htm#
  5. https://renewablesnow.com/news/germany-needs-up-to-446-gw-of-solar-pv-to-achieve-100-renewables-750437/
  6. https://www.nrel.gov/docs/fy13osti/57582.pdf
  7. https://www.energytrend.com/news/20180411-12257.html
  8. http://www.geo.mtu.edu/KeweenawGeoheritage/MiTEP_ESI-2/Solar_energy_and_latitude.html
  9. https://www.researchgate.net/figure/Solar-cell-efficiency-vs-Temperature-plotted-for-the-two-cells-with-trap-densities-of_fig7_237824433

The Sun Becoming a Red Giant

Without the SUN, life on our planet would not exist.

Earth would be a lifeless, ball of ice.

It is the enabler of plants, water, heat, creating the entire ecosystem.

But the sun has a dark side.

Solar flares can interrupt power lines and radio signals causing blackouts.

Solar rays can cause skin cancer, which affects over 3.4 million Americans every year.

Sunscreen is the best defense, but I’d be lying if I said it wasn’t a pain in the ass.

Its surface temperature of the sun is 10,000 deg. F.

90% of the sun is hydrogen, and while it might seem like a star that’s 300,000 times bigger than Earth would exist forever, it consumes 5 million tons of that hydrogen every second.

And one day, our Sun will die.

When stars die, they typically expand into a giant supernova releasing dust and other matter.

Our sun, however, is not big enough to become a supernova.

Instead, our sun will explode into a massive red giant.

The Sun will eventually engulf Mercury and Venus, while bombarding Earth with unlivable amounts of solar radiation

All plants will be burned to a crisp.

Rivers, lakes, and oceans will be baked dry.

Life on Earth will be extinct.

As life becomes uninhabitable on Earth, the goldilocks zone of our solar system will shift towards the outer planets.

This means other places in the solar system – even the moons of Jupiter and Saturn could be suitable for life.

But this will be temporary.

Shortly after the sun has shed its outer layers, it will condense to become a white dwarf, which is the small but immensely dense core of a dead star.

Planets in our solar system will continue to orbit this dead star, but will be too cold to sustain life.

If humans are to survive, we will need to develop space travel and colonization tactics.

The good news is that humanity has about 5 billion years left until the Sun begins to turn into a Red Dwarf.

But we need to continue focusing on developing deep space travel technologies immediately.

May scientists believe the Great Filter is real.

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Understanding UV Rays and Skin Damage

The sun emits radiation along the entire visible as well as ultraviolet spectrum range. In addition, the sun also emits infrared radiation, and even radio waves!

Thankfully, we only need to protect ourselves from ultraviolet radiation. As you probably know, ultraviolet (UV) rays reach your skin causing sunburn and even DNA damage. This results in cellular mutations that can lead to skin cancer. The most deadly form of skin cancer is melanoma.

This post will dive deeper and examine which specific types of UV rays actually harm your skin. After reading this, you will be better educated when selecting sun protection.

First, let’s view the entire electromagnetic spectrum below.

electromagneticspectrum.jpg
Source: Stanford Solar Center

You’ll notice that the UV spectrum is located just to the left of the “visible” spectrum. Humans can see the visible spectrum, whose various wavelengths account for the different colors, but the UV spectrum, composed of wavelengths between 10 and 400 nm, cannot be seen by the naked eye.

Its a wonder that such a small sliver of the entire electromagnetic spectrum causes such massive damage to our cells.

Different types of UV radiation

Spanning from 10nm – 400nm, UV radiation imposes various types of damage to our skin based on the wavelength, frequency, and energy.

In general, shorter wavelength UV rays cause the most damage. This is because shorter wavelengths have higher frequency and a higher amount of energy. Higher energy radiation elicits more harm because it penetrates deeper into skin, tissues, and cells.

Scientists categorize UV radiation into three bands corresponding to the different wavelengths: UV-A, UV-B, and UV-C:

UVC (10-290nm) – completely absorbed by Earth’s atmosphere
UVB (290-320 nm) – 90% absorbed by Earth’s atmosphere
UVA (320-400 nm) – not absorbed by Earth’s atmosphere

Each of the UV bands present different types of risks for humans

As radiation is emitted by the sun towards Earth, the atmosphere (composed of nitrogen, oxygen, carbon dioxide, argon, etc) helps to absorb a large amount of the UV radiation.

Remember how we said the shorter wavelengths of light are more harmful? The good news is that most these shorter wavelengths of radiation (UVB and UVC) are blocked ozone, water vapor, oxygen, and carbon dioxide in the atmosphere.

Specifically, all UVC radiation, and 90% of UVB radiation is absorbed. These rays are largely blocked by our atmosphere because of the unique way that they interact with those chemicals in our atmosphere. Much like sunscreen contains chemicals to absorb certain bands of UV rays, our atmosphere is our best friend for UV protection.

Unfortunately, our atmosphere can only protect so much.

Longer wavelength UVA radiation, for example, is less affected by the atmosphere, so a large amount of the UVA band makes it through. Even though only about 10% of UVB radiation makes it through to pose a risk to humans, a large amount of UVA makes up the dangerous solar radiation that we are exposed to when we go outside on a sunny day.

Once the rays get to our skin, UVA radiation (which lower energy than UVB radiation) tends to penetrate about two layers of skin, causing sunburn and wrinkles long term. The good news, however, is that UVA radiation’s longer wavelength and thus lower energy means it cannot penetrate through our cells, so it does minimal to no DNA damage.

UVB rays, on the other hand, have a slightly shorter wavelength as well as a higher frequency and energy than UVA rays. UVB rays do penetrate our cells and damage DNA causing mutations and skin cancer.

How about UVC rays?

Well – UVC rays have previously been found in tanning beds, and because of the shorter wavelength, higher frequency, and thus greater energy, these rays are extremely damaging, if you are by chance exposed to them. Thankfully, you don’t have to worry about sunlight containing UVC since the atmosphere blocks them completely.

Conclusion:

To protect yourself from wrinkles, block UVA rays.

To protect yourself from DNA damage / cancer, block UVB rays.

UVC rays are largely used in some types of artificial light used for disinfection, such as those made by the company Klaren. Aside from that, there is little risk that UVC rays from the sun will be of any worry.

Sources:

https://www.ncbi.nlm.nih.gov/pubmed/20806994

https://www.who.int/uv/uv_and_health/en/

https://www.skincancer.org/prevention/uva-and-uvb

https://share.upmc.com/2014/07/infographic-abcs-uv-difference-uva-uvb-uvc/

Chemistry of Sunscreen

Stop by a Wallgreens or CVS and you’ll notice a large sunscreen selection, but each product has advantages and flaws. The differences, it turns out, depend on the chemistry of each active ingredient. If you’re in the United States, glancing at the list on the back of each bottle, you’ll see that products tend to have some combination of 8 common active ingredients.

But did you know that of the 8 most common active ingredients, there are actually only two different UV protection mechanisms? Categorized below, you’ll notice that UV filter compounds are much more common, while the mineral blocker type only include two of the main compounds.

Sunscreen lotion contains active ingredients that contribute to the sunscreen’s SPF, protecting you from sunburn by keeping UV rays from reaching your skin and damaging cells. Active ingredients protect you from UV rays in two unique ways:

Filtering:

This method filters or absorbs UV light, turning the radiation into heat energy, rather than allowing it to cause cell damage.

UV filters chemical ingredients: Avobenzone, Homosalate, Octisalate, Octocrylene, Oxybenzone

  • Hazards of UV filters:
    • UV filters can and have been measured in blood of people who use sunscreen frequently. The main concern with these chemicals is endocrine disruption.
    • Oxybenzone is by far the most dangerous chemical found in sunscreen. It penetrates the skin easily and enters the blood stream. It has the ability to penetrate the blood-brain barrier, causing hormone disruption. It is estrogenically active and has potent anti-androgenic effects.

Blocking:

Blocks UV light from penetrating through the mineral ingredients in the sunscreen so that it never comes into contact with your skin. (ex. Zinc Oxide and Titanium Dioxide)

Pick up your tube of sunscreen and look at the back. You’ll see a number of active ingredients. Typically, you’ll see 4 or 5 Filtering type ingredients listed. The compounds that protect by Filtering will tend to absorb only certain wavelengths of light, so sunscreen companies include a combination of different ones to block a broader spectrum of UV rays.

Blocking type ingredients work in a different way, so they are present either by themselves or with a few filter ingredients. For example, you might have sunscreen that lists zinc oxide as the only active ingredient.

To avoid sunburn and more importantly skin damage from UV rays, elect for a broad-spectrum sunscreen with as high an SPF as possible, and ideally use a sunscreen that also contains Zinc Oxide or Titanium Dioxide.

UV blocking minerals: Zinc Oxide, Titanium dioxide

  • Hazards of mineral blockers:
    • Zinc Oxide and Titanium dioxide particles are photoactive, meaning they can create free radicals when exposed to UV radiation that damage surrounding cells. To mitigate this risk, manufacturers apply surface coatings to these particles.
    • Both of these mineral blockers are electrically charged molecules. Over time and due to heat exposure, these mineral blockers can settle or clump, leaving gaps in skin coverage. To be effective, mineral sunscreens contain ingredients that hold zinc oxide or titanium dioxide in a suspension to provide an even coating on the skin.
    • Titanium Dioxide creates more free radicals that do oxidative damage to your body and skin cells, and increases aging processes. Zinc oxide tends to have a broader-spectrum range of coverage than titanium dioxide, although the combination of both Zinc Oxide and Titanium Dioxide provide the broadest range of protection.
    • Zinc and titanium oxide may potentially harm environment.

Some products, such as “SheerZinc Face” by Neutrogena, will contain zinc oxide. Finding a product that contains both zinc oxide AND titanium dioxide is much less common due to the highly charged particles tendency to coagulate and cause clumping.

Conclusion:

As discussed, there are two different types of sunscreen. If you are going for a product that contains Mineral Blockers, Zinc Oxide is preferred over Titanium Dioxide. Check products that contain mineral blockers to ensure lotion consistency is homogenous and not de-coagulated because the clumps will cause gaps in skin coverage, thus causing you to get burnt.

Your ideal sunscreen might have the following active ingredients:

  • Homosalate (8–10%)
  • Ocinoxate (variable percentage)
  • Octocrylene (2–6%)
  • Zinc Oxide (5–15% +)