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This article highlights the key factors that need to be considered when designing rooftop solar PV systems. Secondly, PV system losses need to be minimized which in turn increase energy yield and hence annual cash flows. Optimizing PV design may slightly increase the cost of the system but the financial gains from increased energy yield over the lifetime of the system would be much more significant. Here you will find 12 ways to make your residential solar design efficient.


Efficient solar design for sloped roofs with multiple Tilts and Orientations

Rooftop solar installations need special considerations for optimum energy yield. They have non-optimal tilts and azimuths, near shading elements, increased module loss due to reduced convection cooling and heat emitted by the roof surface.


1. For residential PV systems with multiple tilts and orientations, allocate the identically oriented strings to a single MPPT input on the inverter. In the presence of near shadings structures, select module-level MPPT (power optimizer or micro-inverters). Combination of string-level and module-level MPPT inputs can also be used. These approaches would minimize mismatch losses and result in optimized energy yield.


Technology-Related Design Inputs that improves performance of the residential solar system

2. Use PV modules that have good performance at low irradiance levels. Choose quality modules with positive power tolerance.
3. Consider temperature coefficient of the PV module for power. It is an important design parameter for selecting PV modules for installation in hot environments.

4. Select PV modules with a low LID and degradation rate. Modules must ensure linear power guarantee.

5. Pay attention to inverter efficiency and capacity de-rating due to high ambient temperature in the rooftop solar PV design.

6. One of the most important PV design inputs is the DC/AC ratio. Optimize this ratio for maximizing inverter power during hours of low irradiance. At the cost of clipping energy loss during peak sunshine hours, the inverter can be operated at higher efficiency for most hours of the day. Make sure the selected inverter supports the high DC/AC ratio.


Ensure an efficient Module Layout Design

7. Design an efficient module layout that minimizes cable runs to the point of electrical connection. It will result in reduced voltage drop and electrical losses.

8. Minimize DC wiring loss by using properly sized cables and shortest possible lengths. Similarly, minimize AC wiring loss by using AC cables of appropriate size and minimum possible lengths. Select cables rating according to the highest temperature they are exposed to. Apply appropriate de-rating factors for temperature and grouped conductors. Over-sizing cables to attain lower losses is a beneficial investment.


9. Maintain appropriate gap between the bottom of PV modules and the roof surface. It will facilitate cooling by wind on underside of the panels which will boost system efficiency. Ensuring compatibility with the type of roof, select roof anchors and clips with dimensions that provide greater ventilation under the panels. It will enhance system performance.


10. Use a renowned PV Design Software for design optimization. Through a series of iterative simulations perform site-specific tuning studies to achieve the best possible values of Performance Ratio and Specific Energy Yield (kWh/kWp).


11. Get the final residential solar design evaluated by an independent technical expert and incorporate review feedback that arguments for efficiency and performance issues.


12. Ensure that the system is properly installed and commissioned by certified technicians.


Together with maximizing system yield, the solar design must focus on effective utilization of available space, code compliance, cost-effectiveness, aesthetics of the building, maintenance access to roof elements and strings length.

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