Introduction A well-designed Solar PV system maximises energy generation, efficiency, and longevity. One of the most critical elements of this design process is creating a Solar Panel Array – connecting a group of panels together to create a string – how your solar panels are electrically connected.
Most Domestic Inverters have a 2 String Input connection to their system. Commercial inverters will provide more, dependant on the size of inverter.
In this post, we explore how expert system design when creating a string, plays a vital role in the overall performance.
Here’s what you need to know.
What Is Solar PV System Design?
System design is the process of engineering a solar setup that suits your roof size, orientation, electrical needs, and future goals. It includes decisions around:
- Number of panels
- Panel layout (landscape/portrait)
- Mounting orientation (South/East/West)
- Pitch Angle of panels (10-45°)
- Use of optimisers when required
- Battery storage sizing
- Inverter type (standard & hybrid)
At Moontree Solar, we tailor each design to match your daily usage profile and property characteristics. Generally for Domestic, we maximise generation. With Commercial we maximise to meet site MIC Limit (KVA) or budget.
Understanding a Solar PV String
Solar panels generate DC power and are wired together to create a “string.” A string is made up of a number of panels connected in series. The String Voltage accumulates but system current remains constant.
i.e. TW Solar 435W Solar Panel with a
- Voc of 35.15V
- Isc of 15.86A
Example:
12 Solar Panels connected in series to form a string
- 12 x 35.15 = 421.80V DC
String Total = 421.80V with 15.86A
A typical system has 2 strings per inverter input. Larger installations or complex roof layouts may require more strings and additional inputs.
Design Rules for Strings
To ensure optimal performance, a string must follow strict electrical and physical design principles:
- Voltage & Current Matching: Panels must be matched to inverter specs
- Shading Considerations: Shadow on one panel affects the whole string
- Use of Optimisers: Essential on partially shaded roofs
- Cable Sizing: 6mm DC cable recommended for lower resistance, less voltage loss and future-proofing
- Safety: Strings enter a Fire-Shunt upon entering the roof and are further fitted into a DC Isolator before entering the Inverter – for emergency shutdown
Multiple Roof Layouts
When panels are installed across separate roofs (e.g. East and West), each string typically corresponds to one aspect. This provides an even balance of energy production throughout the day, when possible. Every roof is different.
- South-Facing: Ideal for maximum yield
- East/West Design: Good for energy balance throughout the day
- Fire-Shunt Isolation is required upon every entry to the roof, within 1.5m of cable entry
Optimisers
Shadowing on a panel lowers its solar generation output. Unfortunately, due to electrical physics, if we have a shadow reducing the power output on one panel of a string, this reduces the power of ALL panels on the string. Thus, it is very important to identify possible shadowing at the early stage of design – choose to use a more suitable roof or location.
When there are no other options, we fit optimisers:
- Optimisers are fitted to the possible shadow affected panels. It is fitted to the rear of the panel and are relatively inexpensive, hence no excuse not to fit!
- We include this as part of our proposal and design.
Quality Control & Safety
Each Moontree system undergoes:
- Voltage/current matching review
- Load balancing
- Fireback safety checks at Fire-Shunt, Inverter and Battery
- Clean, secure cable routing with no loose ends
We never rush string layout. Our aim is maximum performance & reliability.
Conclusion
Creating a Solar PV String is a technical discipline that directly impacts your energy yield, safety, and long-term ROI. It is a simple process but can get quite complex when designing across multiple roofs en route to the inverter and takes careful planning and technical considerations – experience is key.
At Moontree Solar, we design every system with care, detail, and electrical accuracy.
The result: higher performance, longer life, and greater savings for you.
Want a system that works as it should for decades? Book your Moontree consultation today.
