Optimisers or microinverters - what is the difference between the two?

The heart of any photovoltaic installation is not the panels, as you might think, but the device that converts the direct current generated by the panels into alternating current that can power household appliances.

However, choosing the right technology is not straightforward, as the efficiency of the installation can vary depending on the conditions. When is a standard central inverter sufficient? Is it better to invest in microinverters or to opt for optimisers?

Optimisers or micro-inverters - when to use them?

The power optimiser is a small device located between the central inverter and each panel. Its task is to continuously analyse the performance of the panels and 'decouple' them from each other. Although the inverter still processes the energy from all panels, each panel operates independently of the others. Many optimiser models also offer the ability to selectively disconnect individual panels from the system, which is useful in the event of panel failure or damage.

Microinverters, on the other hand, can be an alternative to a central inverter. They work in a similar way to standard inverters, except that instead of a single device converting the current and supplying it to the home grid, each panel has its own microinverter. This makes it easier to control the performance of individual panels and to quickly detect failures of individual system components. The microinverters do not spoil the aesthetics of the roof or the installation, as they are virtually invisible from the outside. In addition to managing the PV network and recording performance data, many microinverters have built-in maximum power point tracking. MPPT circuits, which can range from one to several depending on the class of device, locate the maximum power point and adjust the inverter's operating parameters, increasing the PV yield.

Which solution is worth choosing?

The choice between optimisers and microinverters depends on the specific conditions and needs of the photovoltaic installation. When to use microinverters:

  1. Shading: If the installation is subject to partial shading (e.g. trees, chimneys, neighbouring buildings), microinverters will be a better choice as each module operates independently, minimising the impact of shading on the entire installation.
  2. Different pitch angles and orientations: For roofs with complex geometries, where the panels face in different directions or are inclined at different angles, microinverters provide optimal performance.
  3. Safety: if safety is a priority, microinverters are beneficial because they eliminate the need for high DC voltage in the system, which increases fire and service safety.
  4. Monitoring: If you want accurate data on the performance of each module, microinverters offer advanced monitoring functions at the level of each panel.

When to use optimisers:

  1. Existing installations: If you already have an installed system with a central inverter and want to improve its efficiency without replacing the inverter, optimisers are the perfect solution. They can be easily integrated into an existing system.
  2. Costs: If your budget is limited and you need a performance-enhancing solution, optimisers are usually cheaper than microinverters.
  3. Large installations: For large photovoltaic installations, where the use of microinverters can be costly and impractical, optimisers with a central inverter can be a more cost-effective solution.
  4. High DC voltage: If the system operates at high DC voltage and this is not a safety concern, optimisers will be suitable.

Comparison

Feature Microinverters Optimisers
Initial cost Higher Lower
Security Higher (low DC) Lower (high DC)
Monitoring At module level At module level
Installation More components on the roof Needs a central inverter
Performance in difficult conditions Very good Good
Scalability Easy Easy (with central inverter)

Conclusions:

The choice between microinverters and optimisers depends on the specific installation conditions and priorities of the developer. Microinverters are a great solution for systems where individual control and safety are key, especially on roofs with complex geometries. Optimisers offer a good compromise between cost and performance, especially in larger installations where central inverters are already present.

The decision should be based on an analysis of costs, site specifics and expectations regarding monitoring and security.

 

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