One peak solar hour corresponds to 1000 W/m2 of sunshine. However, when calculating the total number of peak sun hours received at any site, hours with 1000 W/m2 of solar energy are not considered. Rather, sum the entire quantity of solar irradiation received by the place. The more intense the sunlight, the faster the plant will grow.
In general, plants require about 12 hours of continuous light exposure to fully mature their seeds or fruits. But during a 24-hour period, sunlight is only visible as dark for about 10 minutes at mid-day. Thus, in order to maximize the amount of time that sunlight is available for growing plants, farmers need to collect solar energy over several days or weeks rather than just during midday hours.
Peak sun hours are calculated by multiplying the daily average intensity of sunlight at the site of interest by the number of days it receives direct sunlight. For example, if the daily average intensity is 1200 W/m2 and the sun is directly overhead during most of those days, then the site has experienced one peak sun hour. If the daily average intensity is 900 W/m2 and the sun is directly overhead on 15 out of 20 days, then the site has experienced two peak sun hours.
Solar peaks occur when the sun is highest in the sky during its orbit around Earth (at noon). During a solar peak, sunlight is directly above the location for approximately 12 hours.
Although your panels may receive an average of 7 hours of daylight each day, peak solar hours are usually around 4 or 5. Solar radiation reaches its greatest during solar noon, when the sun is at its highest position in the sky. At this time, you should be able to generate up to 15% more power than indicated by my chart. However, solar radiation decreases rapidly after solar noon, so I would expect your panel performance to decrease accordingly.
During winter months, direct sunlight doesn't come into play. Instead, you will want to account for overcast days and clouds that can block out light. A study conducted by the National Renewable Energy Laboratory found that you can expect to generate about 75% of your annual electricity output on average during clear days with little wind. Heavy cloud cover or strong winds could reduce this number significantly.
In conclusion, your ability to generate power depends on how much sunlight you receive and how efficient your panels are. You might be able to generate more power than indicated by my charts if you have very large panels or if you install solar-tracking devices.
Noon Peak solar hours are often from midday to early afternoon, when the sun is at its highest and most powerful in the sky. The period between 10 a.m. and 2 p.m. is usually the hottest time of the day.
11 a.m.: The average temperature in San Francisco, California, at this time of year is 70 degrees F (21 degrees C). Direct sunlight intensity is at its strongest and clouds aren't affecting the view of the sun. Noon Solar Radiance is at its highest point today, at 996 W/m2.
1 p.m.: The average temperature in San Francisco at this time of year is 77 degrees F (25 degrees C). Direct sunlight intensity has started to decline slightly, but it's still very strong - 950 W/m2. Clouds have moved into the area around San Francisco and are blocking out some of the sun.
3 p.m.: The average temperature in San Francisco at this time of year is 81 degrees F (27 degrees C). Sunlight intensity has dropped significantly - only 400 W/m2 - and that's being blocked by clouds which have moved into the city.
The more peak sunlight hours a solar panel receives, the more power it generates. Solar panels would get direct sunshine 24 hours a day, every day in an ideal case. Unfortunately, the sun does not stay in one place in the sky, clouds do appear from time to time, and there is the entire dawn and sunset thing that we can't escape. However, solar panels do generate electricity even when it's dark out, they just don't produce as much power then compared to when the sun is out.
In conclusion, solar panels work by using the energy of the sun to create electricity. They require direct sunlight to function properly. Although sunlight isn't always available, solar panels can still generate some amount of electricity from other sources of heat such as hot rocks or even the earth itself during the night time.
Every year, there are around 1,800 hours of sunlight. That's enough for about 50 days without any missing hours.
When it comes to solar energy, more is better. So the more sunlight that hits the earth, the more energy we have at our disposal. Solar panels are made from silicon which can only absorb certain wavelengths of light so they need to be transparent to visible light as well as infrared radiation. They're usually made from glass or plastic but some special materials such as germanium could also be used instead.
So if we want to know how much energy we can expect from the sun, we first need to know how much sunlight falls on the earth's surface. This is called the solar constant and it's approximately 1,360 watts per square meter (10,000 watts per square yard).
Now, having said that, you should remember that what we call "sunlight" these days is only a portion of the electromagnetic spectrum. Some of this light is reflected back into space while some reaches the ground as heat.
The amount of energy that gets absorbed by the planet is called the terrestrial irradiance.