Equipment and components
String inverter
Also known as: central inverter, chain inverter.
Definition
A string inverter connects several panels in series — a string — to a single central inverter. It is the most common and most economical configuration; its drawback is that shade or a fault on one panel can affect the performance of the whole string.
In a string, the current flowing is that of the most limited panel. If one module is shaded, dirty or degraded, it drags the rest of its string down; the panel's bypass diodes contain the damage, but do not eliminate it. That is why a string inverter works very well on clear roofs with a single orientation, and worse on roofs with chimneys, tanks, aerials or neighbours casting shade at specific times.
In exchange, it has solid advantages: it is the cheapest option per installed watt, it concentrates the electronics in a single accessible unit — which simplifies maintenance and replacement — and there is plenty of supply and technical service in the Colombian market. Current models also incorporate several independent MPPTs, which allows two or more groups of panels with different orientations to be handled without penalising each other.
Its weak point is also its concentration: if the inverter fails, the whole system stops producing until it is repaired or replaced, whereas with microinverters only the affected panel's output is lost.
The essentials of String inverter
- Several panels in series form a string connected to a single inverter.
- It is the lowest-cost configuration per watt.
- Shade or a degraded panel penalises its whole string.
- An inverter failure stops the entire system.
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Frequently asked questions about String inverter
When is a string inverter the right choice?
When the roof is clear, has a dominant orientation and there are no obstacles casting shade during hours of good radiation. In that scenario it is the option with the best cost-benefit ratio and there is no technical reason to pay for microinverters.
What happens if the string inverter breaks?
The system stops producing until it is repaired or replaced, because all generation passes through that unit. It is a known, manageable risk: the inverter is accessible, replacement is quick and the warranty usually covers it, but it is worth being clear about the supplier's response time before signing.
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