Commercial barriers to grid connected solar: Curtailment

July 17, 2020

Grid Connection and export approval

The entity that says yes or no to a grid connection for a solar system is called a DNSP (Distributed Network Service Provider). It is the DNSP’s job to keep voltage and frequency “stable” based on regulatory guidelines.

Assumption: the grid is stable and the DNSP has approved a connection for our grid connected solar system with the permission to export with a payment received for each kWh exported.

What is curtailment?

Curtailment is a mechanism to limit or completely cut off the export of electricity into a network.

Why curtailment?

As more solar systems are connected to the grid the more power is exported, and each system causes a slight voltage rise on the grid. The DNSP will observe this in their monitoring systems (from a consumer’s perspective, lights may flicker and appliances fail).

When there are too many systems connected, the grid voltage rise is too high. At this point, a DNSP is required to address this, and the mechanism at their disposal is curtailment.

How is curtailment applied?

Curtailment can occur manually or automatically. If a DNSP sees the voltage rising too much on a distribution network, they will review all grid connections, and can restrict individual sites from exporting energy.

In manual intervention a letter of demand is issued to restrict exports. This little-known risk impacts existing system owners’ returns on investment.

Solar systems are designed to “turn off export” automatically when voltage is outside of a preset range to protect the network. This mechanism, configured in inverters (the device that connects to the grid), is often not monitored.

The issue is only identified by system owners when reviewing their energy statements months later.

Commercial impact

Curtailment represents a risk or limitation to system owners before, during and after a system is installed.

As the penetration of grid connected solar increases, seen in the likes of Australia, Hawaii and Denmark, the hidden risk and impact of curtailment is increasingly realized.

The Solution to Curtailment

The good news is that eleXsys®, with its award winning, behind-the-meter technology can address this risk, before a site is installed, enhancing your business case. And if you suffer from this issue in future, eleXsys® can also be retrofitted to ensure your investment is protected from export curtailment.