Tag: solar

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

Tesla Accelerates Sustainable Energy

How will Tesla enable sustainable transportation?

disclaimer: written by a TSLA shareholder. Opinion. Not investment advice. Do your own research. All information here comes from publicly available sources or is speculation / guessing. Please fact check this blog post. (going overboard on the disclaimer after a particularly funny reddit comment).

Tesla has distinguished themselves as a company that builds both software as well as physical products and hardware.

One of the few companies whose mission appears to be sustainability over profit, they continue to innovate and create the best technology, forcing other players in the market to try to keep up.

Tesla’s Big Goals:

Tesla’s number one mission is to accelerate the transition to sustainable energy. Tesla is progressing in a few main areas to achieve this goal:

  1. produce more affordable electric vehicles
  2. build systems for energy storage
  3. be the best at manufacturing

The CEO of Tesla, Elon Musk, has stated how he believes “you have to have a goal”. Following his earlier statement, Elon kept his word – the company’s goals were concisely outlined during the Tesla battery day event this past September.

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Goal 1: Tesla building Affordable Electric Vehicles

Today, less than 1% of the cars on earth (the “global fleet”) are electric. To increase this, Tesla will build a car that anyone can afford. Tesla has announced plans to build a $25,000 electric car.

With what started as a luxury, high-end car, Tesla is working towards reaching economies of scale to move towards high volume production of a car for the mass market.

Once Tesla reaches full-scale manufacturing and production, Tesla wants to produce and sell 20 million cars per year, enough to replace 1% of the gasoline cars with electric vehicles.

To achieve these numbers, Tesla must increase production of their cars by 40X compared to their 2020 manufacturing numbers.

The center controls are completely touch-screen. source: Tesla

Elon has hypothesized that internal combustion engine industry WILL NOT EXIST in the future, aside from perhaps in museums and hobbyists.

Autonomy & self-driving cars:

Creating self-driving cars is not directly related to reducing carbon emissions, yet it does provide a few solutions that will make buying a Tesla an extremely attractive purchase:

  1. Safety. Autopilot, designed to avoid collisions, has the potential to save the lives of at least 40,000 people per year that die in automobile fatalities. With traditional automobiles, accident probability is 2.1 collisions per million miles. With Tesla autopilot, the probability is 0.3 collisions per million miles.
  2. Entertainment will be important in the car once human attention is no longer just being used to drive. This could include video games (the vehicles already have a number of games available), socialization, reading, working, etc.

It is hard to say just how valuable autonomy is to each customer, but the parameters are as follows: Since autonomy is valuable to cars at an individual level, the value of autonomy for Tesla = value of each car * value of autonomy per vehicle.

Full-self-driving technology BETA version feels like it is close to being released to the market after seeing a few of the CEO’s recent tweets on the subject.

source: Twitter

If the FSV features help the company sell more cars, then the company is that much closer to achieving its mission of an automobile economy based on sustainable energy.

Goal 2: Energy Storage – Tesla Batteries, etc.

To be truly sustainable, energy must be accessible and affordable to everyone. Tesla plans to make vehicles and grid batteries that cost less. This includes reducing the cost of energy per kilowatt hour by one half.

Tesla is working to change the trajectory of the curve of cost per kilowatt hour of energy, pushing the cost lower, shown as the red line. source: Tesla Battery day.

At Tesla battery day, the heads of the company mentioned that reducing the cost per kilowatt hour of batteries is not happening fast enough. This was demonstrated by showing the curve of cost per kilowatt hour of batteries and the slow rate of improvement. Its flattening out, as shown in the photo above.

Battery design:

Tesla is al re-engineering the battery cell design, manufacturing, and production processes to create more affordable cells.

Tab-less batteries. source: Tesla Battery Day
  • Tesla batteries are cylindrical, and newer versions are larger (bigger cylinder cells cost less)
  • Tab length in batteries: older batteries had tabs located at anode and cathode ends, which added to the distance an electron has to travel through a battery. Tesla got rid of tabs, so the electron only has to travel a shorter distance, making them more efficient.
  • Battery filler is not only flame retardant, and it is a structural adhesive. Glues cells to the top and bottom of the sheet.
  • Battery cells are load-bearing, made of steel, dual-purpose as the structure of the car itself. (see below)
The image shows how larger battery cells (blue cylinders) in the bottom image are more efficiently packed into the car. Older design at the top has a large amount of wasted space, shown in red. source: Tesla Battery Day
  • Anode: Tesla uses silicon instead of graphite (graphite is carbon based) for the anode. Silicon is the 2nd most abundant element on Earth, present in Earth’s crust as silicon dioxide, commonly known as sand). Stores 9x more lithium than graphite. Problem with silicon is that it expands in the cells. They use raw metallurgical silicon and design batteries to be able account for expansion.
  • Cathode: the cathode holds the lithium and retains its structure. Nickel is the cheapest and has the highest energy density, but Nickel presents challenges with chemical stability. Cobalt is more expensive, yet more stable than Nickel. For the most energy intensive batteries (like the semi-truck or the cyber-truck) they will use full nickel. The goal is maximizing nickel and gradually removing cobalt from battery manufacturing. The company has added coatings and dopants to stabilize nickel in the batteries. Cathode materials are purchased and priced based on the London metal exchange (LME).
  • Lithium: lithium is plentiful in the US, Tesla already has access to enough for every car (once they are building 20M+ per year). The company mines clay containing lithium in areas of the US where the ground has high concentrations. They extract the lithium via an environmentally friendly process involving table salt NaCl. After mixing it with salt and water, the lithium is extracted because lithium bonds extremely strongly to Cl-. The lithium effectively knocks off the sodium atoms, and we are left with LiCl salt, which the company can use for their battery manufacturing.
  • The company will eventually recycle materials in the used batteries to make new batteries.

Goal 3: Manufacturing

In addition to the number one goal of accelerating the adoption of sustainable energy, Tesla wants to be the best at manufacturing. Elon stated Tesla needs to be “better than anyone at manufacturing”. The company has created a vertically-integrated car from the ground up. They build everything in house, outsourcing little of the process.

The remarkable thing being built by Tesla is actually not the car, but how. The way the company built the car, with heavily automated robotic factories is impressive.

Tesla is building 4 types of products for consumers:

  • Energy generation (solar panels / solar roof)
  • Energy storage (Tesla Powercell) – customers want the freedom to charge at home. The Tesla Powercell product allows people to do so.
  • Electric vehicles (cars and trucks)
  • Automated factories. The company has engineered machines to build the car, supporting the creation of each product. While these three products are very much in the foreground, the importance of the robotic factory in the background has given Tesla a wide competitive advantage that will be extremely difficult to copy.

Factories

  • Sustainable factories include car factories built with solar.
  • Factory close to consumers (on each continent) shortens the supply chain, quicker delivery to customers. Factory in Fremont California, Nevada, Austin TX, Berlin, Shanghai China.
    • Tesla is the only American car company with manufacturing facilities in China.
  • Largest casting machine ever to make the front and rear casting in one piece.
source: Tesla Battery Day

Engineering

The ability to do more with less is an important strategy in engineering for elegance.

The company focuses more on metrics within the context of product improvements and manufacturing than purely financial areas. As of Battery day, the company reported:

  • Reducing number of parts in the car: now 370 fewer parts.
  • Reducing floorspace required in the factory by 35%.
    • Ensuring each cubic meter of the factory floor does useful work.
  • Stop using cobalt in batteries, mainly use nickel now.
  • Materials engineering the frame of the car: Developed their own high-strength casting alloy of aluminum that does not require coating or heat treatment. (Heat treatment historically causes alloys to lose shape)
  • Shortening the supply chain for resources: Reducing miles traveled by materials that end up in cathode by 80%.
  • 10% mass reduction in the car.
  • 14% range increase
  • “Electric energy costs are half those of diesel. With fewer systems to maintain, the Tesla Semi provides $200,000+ in fuel savings and a two-year payback period.” – Tesla.com
Tesla Semi-truck rendering source: Tesla

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Sources:

  1. Tesla Battery Day presentation Deck: https://tesla-share.thron.com/content/?id=96ea71cf-8fda-4648-a62c-753af436c3b6&pkey=S1dbei4
  2. http://www.ev-volumes.com/
  3. IHS
  4. OICA
  5. https://www.tesla.com/blog/secret-tesla-motors-master-plan-just-between-you-and-me
  6. https://www.tesla.com/blog/master-plan-part-deux
  7. Tesla website
  8. TSLA 10k / annual report
  9. twitter