Solar Panels deliver different results depending on the weather and the amount of heat and sunlight they receive. It is well known that solar panels generate energy from sunlight, but what effect does heat have on these units?
If you live in a very hot environment, you may also be concerned about the durability of your solar panels. There are some types of solar panels that are more suitable for use in hot climates.
The best solar panels for hot weather are monocrystalline panels. This type of solar panel has a higher efficiency rating than polycrystalline panels. The ability to convert more useable sunlight into power reduces the effect of the temperature coefficient power losses due to the panels getting hot.
When choosing solar panels for your home, selecting a very efficient type that will convert the maximum amount of sunlight into power is important. Heat isn’t good for generating solar power, yet the solar panels need to be in full sun. If you live in a very hot climate, it is important to understand the effect that heat has on the efficiency of solar panels.
Which Type Of Solar Panel Is Best for Hot Weather?
Monocrystalline Solar panels perform better than polycrystalline panels in very hot conditions and also in low light conditions.
The better performance is due to monocrystalline panels having better efficiency, meaning they can use more of the available sunlight to generate power. Monocrystalline efficiency can be as high as 20 percent. Polycrystalline panels seldom surpass 16 percent efficiency.
Although heat causes both mono and poly panels to drop in power output as they heat up, the higher efficiency of the mono panels gives them the edge over the poly panel design.
The Two Most Common Solar Panel Types
The two common types of solar panels available today are monocrystalline and polycrystalline panels, commonly called mono and poly panels.
The main difference between the two types lies in the structure of the crystals found in the silicon from which the photovoltaic cells are made.
Monocrystalline panels have cells cut from a single crystal of silicon compared to polycrystalline panel cells, which are made up of multiple silicon fragments that have been melted together.
Visually, the monocrystalline solar panels are either a very dark blue or black color, whereas the polycrystalline panels are very blue.
Heat Versus Solar Panels Efficiency
Solar panel efficiency is tested in laboratory conditions at 77 degrees Fahrenheit or 25 degrees Celsius at the industry standard temperature.
This recommended operating temperature is expressed as NMOT on the solar panel’s label and stands for “Nominal Module Output Temperature.”
Although the testing happens at 77 degrees Fahrenheit or 25 degrees Celsius the optimum operating temperature for the specific solar panel brand can vary and is given as the NMOT on the label.
Solar panels require sunlight to generate electricity. Along with sunlight comes heat, which negatively affects a solar panel’s maximum output power (Pmax) or efficiency.
As the solar panel increases in temperature, heating above the optimum operating temperature, the efficiency of power generation by the panel is negatively affected.
This loss in power generation by the solar panel is expressed as a temperature coefficient. The reading is displayed as a negative number, for example -0.50%/DegC.
This means that for every one degree Celsius (1.8 Degrees Fahrenheit) that the panel heats up above the optimum operating temperature (as shown on the solar panel’s label), a loss of 0.50% of maximum output power (Pmax) will be experienced.
In this example, this translates to a 1 percent loss for every two degrees centigrade heat increase.
Do Solar Panels Work Better In Hot Weather?
Solar panels work better (generate more power) in hot weather than in cloudy or rainy weather. Hot weather is conducive to good power generation by solar panels up to a point.
The maximum power that a panel can generate reduces as the panel itself heats up. Once the temperature of the solar panels exceeds the recommended operating temperature, power generating efficiency decreases.
The loss or sacrifice in solar power being generated as the solar panel temperature increases is known as the temperature coefficient and is calculated for each solar panel. The percentage loss per degree Celsius is listed on the solar panel’s label.
Maximum power loss for the average solar panel operating in very hot conditions may be as much as 10 to 12 percent. This may not affect the average homesteader running a small off-grid system at all.
The potential losses can be significant when applying this 12 percent loss to a solar farm or factory.
Can Solar Panels Be Damaged By Hot Weather?
Solar panels are tested extensively to withstand high temperatures, extreme cold, and high wind speeds, so damage from being heated by the sun is unlikely. The solar panel’s expected life span is on average 25 to 30 years.
Most solar panel manufacturers offer a 25-year linear performance warranty which guarantees that the solar panel will still generate at least 80 percent of the rated power output.
Panel temperatures can reach 176 degrees Fahrenheit (80 degrees Celsius) on very hot days without being damaged in any way.
Solar panels are shipped and used worldwide in all types of climates, thus are designed with this in mind. Solar panels need light to work and not heat, as is often assumed.
Clear, cool sunny days are the best in terms of getting the best performance out of panels.
At What Temperature Do Solar Panels Stop Working
Solar panels work well in virtually any climate and temperature, with the only requirement being for sunlight to shine onto the panels to generate electricity.
Solar panels will only stop working when the sunlight doesn’t reach the panel due to heavy shade, being covered by snow or ice, or being exceptionally dirty.
Temperature, weather very cold or very hot, reduces the panel’s output but not to the extent that it will stop working.
Most Efficient Solar Panels Currently Available
Solar panel technology is constantly being improved. With all the great options available, it can be hard to choose the right solar panel for your needs.
For 2021 the following solar panels are currently the market leaders in terms of efficiency, which means their ability to extract the most power from the available sunlight.
Solar panel efficiency figures exceeding 20 percent were unheard of not many years ago; now, it has become the standard to beat.
What Factors Influence Solar Panel Efficiency
Several factors influence the effectiveness of the solar panels and affect their performance either negatively or positively:
Irradiance (W/m2) influencing solar panel performance
Irradiance is the amount of light energy emitted from one thing, hitting a square meter of another. Irradiance is measured in Watts per meter squared. Low irradiance levels will result in poor power generation by the solar panels.
Shading On Solar Panels Affects Their Efficiency
Shade falling onto the solar panels is probably the biggest reason for panels performing poorly. The causes of shading could be the poor placement of the solar panels on a roof, not considering the sun’s position at different times of the day. Shading reduces the efficiency of solar panels.
Solar Panel Orientation Affects Their Efficiency
Solar panel orientation or the direction that the panels face is important to ensure the maximum number of useable sunlight hours are taken advantage of by the solar panels.
Online Solar panel orientation calculators are numerous and help determine the orientation of permanently fixed solar panels.
Movable solar arrays that track the sun as the day progresses are, of course, an option if the maximum possible solar needs to be extracted from the panels.
In the Northern hemisphere, solar panels perform best facing south. In the Southern hemisphere, north-facing is best.
Temperature Affects Solar Panel Efficiency
Temperature plays a large part in solar panel efficiency reduction. Cool sunny days deliver the best solar production.
The temperature coefficient comes into play as the heat increases past the solar panel’s optimum operating temperature.
Loss of solar energy production due to heat can be as much as 0.5% of the solar panel’s power output with every 1 degree Celsius (1.8 degrees Fahrenheit) that the solar panel temperature rises.
Location Affects Solar Panel Efficiency
Your geographic location and the physical placement of solar panels in a specific location play a major part in how much power your solar panels will generate.
In terms of geographic location, countries closest to the tropics are more suitable for solar use than countries closer to the north and south poles. Low solar efficiency in some countries is because the earth is round, causing that not all countries receive the same amount as others.
Solar panels are reliant on solar radiation emitted by the sun. So in countries where darkness prevails for months at a time, this option is hardly viable.
As an example, in the United States, the South Western states are very well suited to Solar Power generation.
Physical placement of solar panels has to be done considering shadows cast by nearby tall buildings, mountains, trees, etc.
Obstacles casting shade onto solar panels disrupt the panel’s ability to generate power. As panels are connected in series, one panel’s shading will affect the output of all the panels in that string, reducing power output.
How Do The Seasons Influence Solar Efficiency?
Solar systems generate more solar power in the summer months when long clear sunny days prevail than in the year’s winter months. Solar production is directly linked to the amount of useable sunlight that is available in a day.
If you’re living in the tropics, this will be less of a problem than it would in countries located closer to the poles.
In the northeastern United States, the annual solar generation is split into roughly 65 percent being generated between March and September while about 35 percent is generated in the colder part of the year.
Three main factors cause the low seasonal solar output:
- Fewer daylight hours: Shorter sunny days in winter.
- Climatic conditions: Generally more cloudy and stormy days in winter and possibly snow that covers the panels.
- The sun’s angle: Suns angle is lower relative to the solar panel’s position; hence less sunlight landing on the panels at 90 degrees.
Dust And Dirt On Solar Panels Reduce Efficiency
Solar panels perform best when they are sparkling clean. Dust and grime can accumulate on the solar panels over time, given that they’re exposed to the elements.
A fine dust layer on the solar panels reduces the panels’ efficiency due to the dust causing shading on the panels. The dust also reflects useable sunlight off the surface of the panels, which causes lost energy.
Leaves or debris that has settled on the solar panels will reduce the solar panel’s power output.
Keeping Solar Panels Cool To Improve Their Performance
Purpose-built solar panel mounting structures are readily available in the market for all the different roofing types available today.
Besides securely holding the solar panels in place, the secondary function is to lift them off the roof’s surface to allow air to flow under the solar panels. Ventilation is critical for cooling the solar panels to reduce power loss due to the solar panels getting hot.
Solar panels should never be mounted flush with the roofing surface, restricting airflow underneath the solar panels.
Water Cooling To Reduce Solar Panel Temperature
In some very hot parts of the world, solar plant operators have resorted to keeping the solar panels moist during the heat of the day to keep the panels cool.
As we know, hot solar panels generate less power as they heat up. The phenomenon is known as the temperature coefficient.
Large solar plants can lose up to 12 percent of their potential productivity due to the panels heating too far past their nominal operating temperature.
The cost of installing irrigation systems that run a thin stream of water over the surface of the panels is justified by the reduction in power losses that they would otherwise have had.
The water flow combined with airflow over the solar panels reduces the physical temperature of the solar panels, ensuring they operate as close to their optimum operating temperature as possible.