Maximise Solar for a battery

Sun Chasing: Optimizing Solar Panel Placement and Angle for Battery Charging

Harnessing the sun’s power for your home battery requires strategic placement and angle adjustments for your solar panels. This article dives into the technical aspects of maximising solar energy capture for efficient battery charging, considering both fixed and tracking systems.

Facing the Sun: Direction for Optimal Performance

The cardinal rule: South-facing panels in the Northern Hemisphere captures the most sunlight throughout the year. This maximises energy production for battery charging. Deviations of up to 45 degrees east or west might only result in a 5-10% efficiency loss, but every bit counts. but this is not always the case as the maximum may not be the optimal requirement.

Finding the Sweet Spot: Tilt Angle for Peak Production

The optimal tilt angle for your panels depends on your latitude. A simple rule of thumb is to set the tilt equal to your latitude. For example, at 35° latitude, a 35° tilt is ideal. This ensures the panels face the sun perpendicularly throughout the year, capturing maximum energy during peak sunlight hours. But, you will lose the summer and winter peaks as the panels cannot be optimal for all year round capture.

Shifting Peak Production: While a fixed south-facing tilt maximises the average annual energy, it might not perfectly align with your battery charging needs. Here’s a strategy:

• Steeper Tilt (Winter Focus): In winter, when the sun is lower in the sky, tilting the panels slightly steeper (up to 15° more than your latitude) can increase winter sun capture, ideal for winter battery charging.
• Shallower Tilt (Summer Focus): Conversely, a slightly shallower tilt (up to 15° less than your latitude) can capture more midday summer sun, potentially good for high summer loads.
  

top image Reading bottom Edinburgh showing the tilt angle of panels.

Balancing Power with Battery Charge Limits:

Consider your battery’s limitations. For instance, a 200Ah Lithium Iron Phosphate (LFP) battery typically charges best at a maximum of 40 amps. If your solar array produces significantly more than 40 amps at peak sunlight hours, consider:

• Panel angle: Strategically turning the panels can reduce midday output, bringing it closer to your battery’s ideal charging current.
• Microinverters: Using microinverters allows individual panel optimization, enabling some panels to be slightly tilted for higher morning/evening sun capture while others remain at the optimal angle.
  
  Note: Tilt adjusts seasonal variations, as well as early morning or late evening as the sun rises and falls, Angle adjusts the time of day the panel peaks, east for morning and west for dusk.

Solar Power Curve and the Dual-Axis Tracker Advantage

A solar power curve depicts a typical day’s energy production, with a peak around noon and lower outputs in the morning and evening. Dual-axis solar trackers continuously adjust the panel angle to face the sun directly throughout the day. Here’s the impact:

• Daily Gains: Dual-axis trackers can increase daily energy generation by 25-40% compared to fixed-tilt systems.
• Yearly Gains: Studies show annual energy production increases of 15-35% with dual-axis trackers.

However, trackers come with drawbacks:

• Higher Cost: Trackers are significantly more expensive than fixed-tilt systems.
• Maintenance: They require more maintenance due to moving parts.
• Limited Benefit at Lower Latitudes: The benefit of trackers diminishes as you move closer to the equator, where the sun’s path is less dramatic.

East-West Fixed Array Power Curve

Fixed east-west arrays offer a flatter power curve, generating electricity throughout the day, though with lower overall production compared to south-facing fixed arrays. Here’s a sample power curve with production at three key times:

• Winter: Lower overall production due to shorter daylight hours. Morning and evening sun capture might be beneficial for specific needs.
• Spring & Autumn: More balanced power distribution throughout the day, potentially useful for offsetting daytime home loads.
• Summer: Afternoon production might peak above battery charging limits, requiring additional management strategies like shade structures.

Optimising Your System: Choosing the Right Setup

The best setup depends on your location, battery type, and usage patterns. Here’s a breakdown to help you decide:

• For Maximum Annual Battery Charging: South-facing fixed tilt (adjusted slightly for winter/summer focus if needed) offers the best balance between cost and production.
• For Flatter Power Curve and Daytime Load Offset: East-west fixed arrays can be suitable, but with lower overall production.
• For Maximum Daily/Yearly Production (Budget Permitting): Dual-axis trackers provide the highest output, ideal for off-grid systems or maximising battery charging.

Additional Considerations:

• Shading: Minimise shading on your panels for optimal performance.
• Battery Management System (BMS): A BMS protects your battery by limiting charging current and preventing overcharging.
• System Sizing: Ensure your solar array size matches your battery capacity and expected production and loads.

__________________________________________________________________________________________________________

Chasing the Peak: South vs East-West Solar Panel Placement for Battery Charging

While south-facing panels offer the best year-round average energy capture, they might not perfectly align with battery charging needs, especially in off-grid or battery-centric systems. lets explore the concept of “peak shifting” through panel placement and compares the power curves of south-facing and east-west arrays for optimised battery charging and power delivery.

The Solar Power Curve and the “Duck Curve” Challenge

A typical solar power curve for a fixed south-facing array shows a sharp peak around noon, with lower production in the morning and evening. This creates the “duck curve” phenomenon – a mismatch between peak solar generation and peak electricity demand (often in the evening). This mismatch poses a challenge for off-grid systems or those heavily reliant on battery storage. – Read more on the Duck

Peak Shifting with Panel Tilt and Orientation

The sun’s path across the sky offers an opportunity to “shift” the peak power generation of your solar panels. Here’s how:

• South-facing with Adjusted Tilt: While south-facing offers the highest average annual production, a slight tilt adjustment can be strategic. Tilting the panels slightly steeper in winter captures more low-angle winter sun, potentially shifting the peak towards winter needs. Conversely, a shallower tilt captures more mid-day summer sun.
• East-West Fixed Arrays: These arrays offer a flatter power curve, generating electricity throughout the day. While overall production is lower than south-facing, the peak is spread out, potentially aligning better with battery charging needs during the day.
  
  Note: sun hours vary during the year, from 2 in winter to 10 in summer. The winter “window” is small and narrow in winter when we use more power. therefore south facing panels at a steep angle can be optimal. However this is not practical on a roof installation.

Comparing Power Curves: South vs East-West

Here’s a breakdown of the power curves for each setup:

South-Facing (Fixed Tilt):

• Pros: Highest overall annual production.
• Cons: Sharp peak around noon, potentially exceeding battery charging capacity. Lower winter and evening production.

Power Curve: A steep curve with a pronounced peak around noon, followed by a rapid decline in the morning and evening.

East-West:

• Pros: Flatter power curve with more balanced production throughout the day.
• Cons: Lower overall production compared to south-facing.

Power Curve: A flatter curve with lower peaks in the morning and evening compared to south-facing, offering more consistent power generation.

Choosing the Right Setup for Peak Shift

The optimal setup depends on your location, battery capacity, and usage patterns:

• Maximise Annual Battery Charging: If your primary goal is maximising annual battery charging, a south-facing array with a slight seasonal tilt adjustment might be ideal.
• Prioritise Peak Shift and Daytime Load Offset: For a flatter power curve and better alignment with daytime electricity needs (e.g., offsetting home loads), east-west arrays can be a good choice, even with slightly lower production.

Additional Considerations:

• Shading: Minimise shading on your panels for optimal performance at any orientation.
• Battery Management System (BMS): A BMS protects your battery by limiting charging current and preventing overcharging, even with peak production.
• System Sizing: Ensure your solar array size considers your battery capacity and expected daily energy use, especially with east-west arrays that might have lower overall production.
• Dual arrays: Maximise the solar yield with a summer and winter array, due to the significant difference in performance of up to 50% you could have smaller arrays for the seasons

By understanding the impact of panel placement on the power curve and strategically “shifting the peak,” you can optimise your solar system for efficient battery charging and a more balanced energy flow in your off-grid or battery-centric setup.

The Dual-Axis Tracker Advantage: Power on Demand

Dual-axis trackers continuously adjust the panel angle throughout the day to face the sun directly. This offers several advantages for peak shifting:

• Flatter Power Curve: Trackers follow the sun’s path, generating electricity throughout the day, leading to a flatter power curve compared to south-facing fixed arrays.
• Increased Daily/Yearly Production: Studies show trackers can increase daily energy generation by 25-40% and annual production by 15-35% compared to fixed-tilt systems.

Power Curve: A flatter curve with a slightly lower peak than a south-facing fixed array, but with extended production throughout the day.

Explanation:

The key point to understand is that while the peak production of a single day might be slightly lower for a tracker compared to a perfectly south-facing fixed array on a clear day (due to the tracker not being exactly perpendicular to the sun at peak hours), the tracker’s ability to capture more sunlight throughout the entire day, including early mornings and evenings, leads to a significant increase in overall daily and annual energy generation.

In simpler terms:

• South-facing fixed: Higher peak, but less overall production due to lower production in the mornings and evenings.
• Dual-axis tracker: Slightly lower peak (on some days) but with extended production throughout the day, resulting in a higher overall daily and annual energy generation.

There are two main reasons why a dual-axis tracker might not be exactly perpendicular to the sun at peak hours, even though its objective is to constantly face the sun directly:

1. Mechanical Limitations: Dual-axis trackers are marvels of engineering, but they have physical limitations. The motors and gears that move the panels might have some lag or introduce slight inaccuracies in positioning. This can result in the panels being off by a few degrees, even with advanced tracking algorithms.
2. Sun’s Path and Tracker Range: The sun’s path across the sky is not perfectly straight throughout the year. It varies depending on your latitude and the season. Dual-axis trackers are designed with a specific range of motion. While this range is extensive, it’s possible that on some days, at peak sun hours (especially at the solstices – summer and winter), the sun’s position might be slightly outside the tracker’s range of motion. In these cases, the tracker will be pointed as close to the sun as possible, but it might not achieve perfect perpendicularity.

Here’s a breakdown of the impact:

• Impact on Peak Production: The slight deviation from perfect perpendicularity at peak hours can cause a small decrease in peak power output compared to a perfectly south-facing fixed array on a clear day. However, this is usually a minor difference.
• Overall Benefit: Despite the potential for a slightly lower peak on some days, the tracker’s ability to capture more sunlight throughout the rest of the day, especially during mornings and evenings, significantly outweighs the minor loss at peak hours. This leads to a higher overall daily and annual energy generation compared to fixed-tilt systems.

Additional Points:

• The efficiency loss due to not being perfectly perpendicular is usually minimal (within a few percentage points).
• Newer, more advanced trackers are constantly improving accuracy and range of motion.
• The benefit of trackers is generally greater at higher latitudes where the sun’s path has a more dramatic arc across the sky.

In conclusion, while dual-axis trackers strive for perfect sun alignment, mechanical limitations and the sun’s path variations can occasionally cause slight deviations. However, the overall gain in daily and annual energy production through capturing more sunlight throughout the day makes them a powerful tool for maximizing solar energy capture, especially for off-grid and battery-centric systems.

Dual-axis trackers aim to achieve a flatter power curve with more consistent power generation compared to fixed-tilt systems. While not a perfect “flat line,” the tracker’s ability to capture sunlight throughout the day leads to a higher overall daily and annual power yield.

Addressing the Logical Defect:

Facing the Sun and Peak Production:

Yes, the core advantage of dual-axis trackers is that they constantly adjust to face the sun directly. This ensures they capture the most sunlight possible throughout the day, leading to the increased daily and annual production compared to fixed-tilt systems.

Drawbacks of Trackers:

• Higher Cost: Trackers are significantly more expensive than fixed-tilt systems.
• Maintenance: They require more maintenance due to moving parts.
• Limited Benefit at Lower Latitudes: The benefit of trackers diminishes as you move closer to the equator, where the sun’s path is less dramatic.

Recap: Power Curve Comparison for Peak Shifting

Here’s a table summarizing the key characteristics of each setup’s power curve:

Choosing the Peak Shifter for Your Needs

The optimal setup depends on your location, battery capacity, and budget:

• Maximise Annual Battery Charging (Budget Conscious): South-facing with a seasonal tilt adjustment offers a good balance between cost and production.
• Prioritise Peak Shift and Daytime Load Offset: East-west arrays work well for flatter power curves and daytime energy use, even with lower production.
• Maximise Daily/Yearly Production (Budget Permitting): Dual-axis trackers provide the highest overall production and most flexibility for peak shifting, ideal for off-grid systems or maximizing battery charging.

Additional Considerations:

• Shading: Minimize shading on your panels for optimal performance at any orientation.
• Battery Management System (BMS): A BMS protects your battery by limiting charging current and preventing overcharging.
• System Sizing: Ensure your solar array size considers your battery capacity and expected daily energy use, especially with east-west arrays or trackers that might have lower peak production.

By understanding the power curves and peak shifting capabilities of each setup, you can choose the optimal solar system for your off-grid or battery-centric needs, ensuring efficient battery charging and a balanced energy flow.