If you follow the news about the Australian energy industry, you have probably read that rooftop solar power is growing at an extremely fast pace. For example, Australia was one of the eight countries that installed more than 1,000 megawatts of solar generation capacity in 2017. A common argument against rooftop solar power, commonly spread by the fossil fuel industry, is that excessive use can destabilise the power supply and cause large-scale blackouts. However, the opposite is true: distributed generation leads to increased reliability, especially when complemented with energy storage.
By themselves, solar panels are not smart devices, since they can only provide electricity when sunlight is available. The argument that too much solar power can destabilise the grid is based on this fact, which makes it seem realistic. However, there is a major flaw in the argument: it ignores the fact that solar arrays are connected to the power grid through inverters, which are smart electronic devices.
When many rooftop solar systems are added to a power network, one of the main concerns is destabilising grid voltage and frequency with an excessive supply of electricity. However, this is solved easily with inverters, which are capable of clipping excess power from photovoltaic arrays.
In fact, inverters can tolerate wider frequency fluctuations than conventional power plants fired by fossil fuels. If a power network fault causes a frequency variation, conventional power plants are more likely to trip than the inverters in solar PV systems. This means that rooftop power is actually contributing to power grid stability.
Inverters are highly tolerant to frequency variations, both below and above the rated value. Being solid-state electronic devices, they can adjust their operating parameters much more quickly than conventional power plants.
Wind and solar power are often blamed for blackouts in Australia, given their variable electricity generation. However, statistical data indicates otherwise: most blackouts are caused by power network issues. Old coal-fired power plants are also prone to faults, especially in the hottest days of summer, when their energy output is needed the most. On the other hand, solar power systems reach peak productivity during summer, helping energy consumers offset their air conditioning expenses.
Rooftop solar power will become even more reliable as batteries decrease in cost. Distributed generation and storage reduce the need for expensive power grid upgrades, for the simple reason than electricity is produced closer to the point of use. The conventional approach of using centralised power stations requires high-power transmission lines, and the network becomes more vulnerable to a localised fault. On the other hand, if you have thousands of buildings with solar power systems and battery arrays, individual faults have almost no effect on the power system.
Rooftop solar power is only a threat for the established business models in the electricity industry. It gives homes and business the option of producing their own electricity instead of paying the hefty tariffs found in Australia.