Can the power grid depend entirely on solar energy?

Published: 11 February 2019

Solar energy production can be unstable and is heavily dependent on the weather. Despite this unpredictability though, is it capable of powering the entire power grid on its own? And if so, how can it be achieved?

How does the power grid work?

The power grid is almost like a living organism that constantly changes over time, it has low and peak operation hours and needs a lot of agents to work on its behalf to keep it running within safe values. The power grid is a network through which the electricity flows and goes from one point to another. 

When you plug your computer into the outlet of your house or when you turn on that music stereo in the living room, you have no idea of all the processes and work that is required to take the electricity from the generation source to your house.

There is no way to control where the electricity will flow inside the power grid. Put simply, there are connection points called busbars from which the energy can be injected or drawn. 

In order to have electricity available at every point of the power grid, it is necessary to keep it balanced at all times. Meaning that large blocks of energy demands need to be equal in every single instant with an equivalent amount of energy generation. 

To give you an idea of the importance of this balance, if the generation surpasses the demand by much, then the frequency will increase. This causes an imbalance that could possibly lead to a shutdown if the frequency was not immediately reduced.

Therefore, it is essential to effectively forecast the energy demands of the grid in different periods of time (yearly, monthly, weekly, daily, hourly and even in steps of 15 min) based on previous historic records, the season of the year and current electricity demands.

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What would happen if the power grid worked entirely on solar?

First, we must remember that the nature of solar energy is unstable. 

Clouds, rainy days or low-irradiation days can deeply affect solar energy production. 

When you take a look at the effect of these factors on your home PV array, you will find that there is not much trouble. 

That’s because during the days of low solar energy production the power grid supplies the remaining electricity needed by your home. 

However, what happens when these effects take place on large scale power plants?

As we mentioned, the Independent System Operators (ISO – transmission line operators) need to constantly balance the power grid

If solar power is low in a single hour of the day and electricity demand increases, there will be an imbalance in the grid. 

If that occurs, the system operator will need to rapidly supply the missing amount of energy with another source of energy or power plant.

In a balanced grid, if solar power is low, the system operator can appeal to other resources to cover the extra amount needed. The ISO will need to use another source such as wind, hydro, biomass or in the worst case, natural gas.

However, if we had a power grid functioning entirely on solar energy, then the ISO wouldn’t be able to appeal to other sources. 

In this scenario, the power grid would become unstable, which would lead to constant blackouts. 

Therefore, the short answer to the question in our title is definitely NO!

Power grids with big solar energy capacity

It is definitely true that power grids cannot function entirely on solar. 

But the fact is that they can work with a great power capacity share of solar energy.

However, as solar increases in the power grid, a new phenomenon appears in the scenario. It is called the ‘Duck Curve’:

Since most solar energy generation occurs around midday, this creates a shift in energy demands of power grids over the day, many times with extra solar energy generation. 

As sunset approaches, grids with large PV power plants reduce their power outputs rapidly and by 6 pm solar energy production is almost zero while energy demand rapidly increases due to night activity. 

This presents a problem as the ISO needs to rapidly cover all that extra amount of energy needed that was supplied by solar energy just a few hours ago. 

Not all generation sources are able to catch up with rapid demand curves, therefore a deep analysis must be carried out.

The duck curve: how solar increases in the power grid


As we can see solar energy cannot be the only and single solution to the energy demands of the world due to stability issues and an increasing new problem in states with high solar energy production.

Thus, it is necessary to have a new ally in this renewable energy trend, and it is called: energy storage. 

Installing large energy storage power plants in states with a high share of unstable renewable sources (solar and wind) will be a game-changing innovation that will make it possible for clean energy generation to make its way to complete independence from fossil sources. 

By having large energy storage capacities available, stability issues are forgotten. The duck curve problem can be easily mitigated by storing excess energy during the day for later use at night.

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