Solar panels with identical specifications can have a different electricity output, depending on how much sunlight reaches their photovoltaic cells. Before installing solar panels on any home or business, finding the ideal placement is a very important design decision. There are two important requirements:
- Ideally, solar panels should be installed in areas that never get shading. When this is not possible, they should be located on the rooftop or ground areas that will get the least possible shading throughout the year.
- Solar panels should also be positioned for maximum productivity. Their tilt angle and east-west orientation (azimuth angle) should allow the highest possible solar radiation on their surface, which translates into maximum savings.
Ground-mounted solar systems offer more flexibility during installation since their racking structure can have any tilt or orientation. Roof-mounted solar systems offer less flexibility since their possible orientations are limited by roof geometry and topology.
Solar engineers use advanced design software such as PVsyst, which can simulate the sun’s position in the sky throughout the year. This way, they can find the ideal placement for solar panels in any part of the world. When the optimal placement is not possible due to roof geometry or other site conditions, they can determine the second-best option that is feasible.
Solar design software can also simulate the shadows cast by surrounding obstacles such as trees and buildings. Based on the simulation of the sun’s movement, design software can determine how shadows will behave during the day and throughout the seasons. Using this information, the optimal areas for solar panels can be identified.
Solar Panel Positioning: The Effect of Geographic Location
The sun’s position in the sky at a given time of the year depends on your geographic location. In northern hemisphere countries like the US and Canada, most sunshine comes from the southern portion of the sky. This means that solar panels should be tilted south to maximize the amount of sunlight reaching their surface.
A north-facing solar panel will still generate electricity because it gets indirect sunlight, but it will not reach the highest possible output.
The opposite applies for southern hemisphere countries: solar panels should be tilted north, since most sunlight comes from that direction. For example, you would notice this if you visited Australia, one of the leading solar countries in the southern hemisphere.
As you move farther to the north or south, the sun’s position in the sky is lower at a given time of the year, and the optimal tilt angle for solar panels increases.
For example, California and Alaska are both located in North America, but the sun is much lower in the sky in Alaska. If you compare pictures of solar arrays in both locations, you will notice that the tilt angle is higher close to the north pole.
Finally, in countries close to the equator, the ideal placement for solar panels is facing upward. This maximizes the incident sunlight since the sun tends to be high in the sky throughout the year. This is very convenient in commercial buildings with large and flat roofs, since there is no need for a tilted mounting structure.
Finding the Optimal Solar Panel Tilt with the Global Solar Atlas
You can use the Global Solar Atlas to check the solar resources available in any part of the world, and this includes the ideal tilt angle for photovoltaic panels. The Global Solar Atlas was developed by the World Bank and the International Finance Corporation (IFC), and using it is very simple:
- Find your location by dragging and zooming the map provided by the Atlas and click.
- Alternatively, you can simply input your coordinates on the search bar.
Knowing your location, the Atlas will display a detailed breakdown of the solar resources in your location. This includes the specific photovoltaic power output: the annual kilowatt-hour output (kWh) per kilowatt-peak of installed capacity (kWp).
For example, if your location has a specific PV output of 1,600 kWh per kWp, and you have a 10-kW solar array, you can expect to generate around 16,000 kWh per year.
The Global Solar Atlas will also display the optimum tilt of PV modules for any geographic location. You can see how this value changes depending on your location, and we will use the following US cities as an example:
|City||Optimum tilt angle for solar panels|
|New York City, NY||35°|
|Los Angeles, CA||32°|
|Anchorage, AK||Over 50°|
As you can see in the table above, the ideal tilt angle for solar panels is less than 30° in southern US cities, and higher than 30° in northern cities. You can also click on locations outside of the US to see how the optimum tilt angle changes. For example, you will get a value of only 4° if you click on Quito, Ecuador, and a value of 37° for Dublin, Ireland.
A qualified solar company will conduct a detailed site assessment of your property before installing photovoltaic panels. Using this information, they will design the system based on calculations and simulations that reflect the exact site conditions.
However, the Global Solar Atlas is a great resource that can be easily understood without a technical background in the solar industry.
Solar Panel Azimuth: East-West Orientation
When specifying the position of solar panels, the tilt angle only provides half of the information needed. For a complete picture of how a solar panel is installed, you also need to describe its orientation with respect to east and west. This is called the azimuth angle:
Regardless of your geographic location, the sun rises in the East and sets in the West. Since the sun is half of the time on each side of the sky, the ideal azimuth for solar panels is 0° (North) in the southern hemisphere and 180° (South) in the northern hemisphere. However, there are specific cases where it makes sense to have solar panels facing east or west, depending on several factors:
- The electricity consumption profile of a building.
- The availability of net metering.
- Electricity tariffs with time-of-use rates
The energy consumption profile of a building depends on its intended occupancy. For example, a K-12 school will tend to use more energy in the morning, and a plaza with bars and restaurants will tend to use more energy in the evening. Depending on how a building uses electricity, it may make sense to have solar panels facing east or west.
East-facing solar panels make sense for a school or any other building with a high electricity consumption during the morning since power will be generated exactly when needed. On the other hand, west-facing solar panels make sense when a building is mostly active after sunset.
Many electricity providers give you the option of exporting surplus power to the grid in exchange for a credit, but the kilowatt-hour price they pay is normally lower than the price they charge. You save the full value of each kilowatt-hour when using solar energy, but in most cases, you only get partial credit for exporting to the grid.
If your electricity provider offers net metering with 100% credit for each kilowatt-hour generated by solar panels, it makes sense to install them facing south (or north in the southern hemisphere). Since you get full credit for each kWh, consumed, or exported, it makes sense to generate as much electricity as possible.
Local electricity tariffs aka rates may also influence the decision to have solar panels facing west. Many power companies charge time-of-use rates, which change depending on the hour.
The highest rates are normally charged when the grid experiences peak demand, and this tends to happen in the afternoon and evening. This is especially true on hot summer days: homes and businesses are using their air conditioners at full power in the afternoon, to compensate for the heat gained during the sunniest hours of the day.
If you’re charged a much higher kWh price in the afternoon, west-facing solar panels may actually achieve higher savings. For example, if your total electricity production drops by 5% with respect to a south-facing array, but the afternoon kWh price is 50% higher, you can save more dollars with slightly less kilowatt-hours.
General recommendations can be given with respect to the tilt angle since it depends on your geographic location. However, the decision to install solar panels facing east or west will depend on the specific conditions of each system.
When Does a Solar Tracking System Make Sense?
Solar panels can also be installed on automatic tracking mechanisms, which keep them always pointed towards the sun. There are single-axis trackers that only adjust the tilt or azimuth, and double-axis trackers that can adjust both angles.
A cost-benefit analysis is fundamental before installing a solar tracker. One of the main advantages of solar panels is their simple maintenance: having no moving parts, they are not subject to mechanical wear. However, a tracking mechanism comes with additional upfront costs and maintenance requirements.
In general, a solar tracker makes sense when the economic benefit of generating more electricity exceeds the ownership cost of the tracking mechanism. Solar tracking is not normally an option for residential rooftop installations since most roof structures are not suitable for the required mechanism.
If space is not a limitation, also consider that you can increase productivity by simply installing more solar panels, without having to deal with the maintenance requirements of a tracking mechanism.
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