The Duck Curve

Understanding the Duck Curve: The New Challenge for Renewable Energy
As renewable energy sources like solar power become more prevalent, the energy grid faces new challenges. One of the most prominent is known as the "duck curve"—a term that describes the unique way energy demand fluctuates when a significant portion of electricity comes from solar energy.
In this blog post, we’ll break down what the duck curve is, why it matters, and what can be done to address it.

What is the Duck Curve?
The duck curve illustrates the daily pattern of electricity demand on a power grid that incorporates a lot of solar power. The term comes from the shape of the graph, which, when charting electricity demand over the course of a day, looks like the silhouette of a duck.
Here’s how it works:

1. Morning Hours (Tail of the Duck): Before the sun rises, electricity demand is moderate because households and businesses are just starting their day. Power plants must supply most of the energy during this time.
2. Midday (Belly of the Duck): As the sun climbs, solar panels generate significant amounts of electricity. This reduces the need for traditional power sources, which causes a drop in the amount of energy that power plants need to generate. This dip in demand for grid power is the "belly" of the duck.

• Late Afternoon/Evening (Neck of the Duck): As the sun sets, solar power production drops sharply. However, electricity demand peaks in the late afternoon and early evening when people come home from work and turn on lights, appliances, and heating or cooling systems. This sharp increase in demand creates the "neck" of the duck, where the grid needs to ramp up traditional energy sources quickly to meet demand.
• Late Evening/Overnight (Beak of the Duck):  As households wind down for the night so does demand on the grid, and power plants scale back production.  However, without battery or other methods of storage power during this time is primarily generated from fossil fuels.  ​

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The price of electricity on the wholesale markets closely follows the Duck Curve as can be seen from the below image.

Why the Duck Curve is a Problem
​At first glance, the duck curve might not seem like a big deal. However, it presents a few key challenges for grid operators:

1. Sharp Demand Ramps: The steep increase in energy demand in the late afternoon is difficult for power plants to handle. Many power plants, especially those powered by fossil fuels, take time to ramp up production. The rapid increase in demand can strain these plants, leading to inefficiencies and potential reliability issues.
2. Overgeneration Risk: During midday, when solar generation is high, there can actually be too much electricity flowing into the grid. Without proper storage or distribution systems, this excess energy can lead to grid instability or waste, as the grid operators must find a way to balance supply and demand in real time.
3. Increased Carbon Emissions: The duck curve can paradoxically increase carbon emissions. While solar power reduces the need for fossil fuels during midday, the quick ramp-up of gas or coal plants in the evening can offset these benefits. Power plants that have to quickly adjust their output are often less efficient and may emit more CO2 than if they were running at a constant, optimised rate.

Cleaner power is cheaper power
​Like price, the carbon intensity of the grid closely follows the Duck Curve.  The cheapest times of the day to procure electricity from the grid also correlate to when the grid has the lowest carbon intensity.

Solutions to the Duck Curve Problem
Addressing the challenges posed by the duck curve is crucial for maximising the potential of renewable energy. Here are a few strategies that can help:

1. Energy Storage: The most promising solution is large-scale energy storage, particularly in the form of batteries. By storing excess solar energy during the day, batteries can release that energy when demand spikes in the evening. This smooths out the curve and reduces the need for power plants to ramp up quickly.
2. Demand Response: Encouraging consumers to shift their electricity usage can help flatten the duck curve. Incentives like time-of-use pricing encourage people to use electricity during off-peak hours (e.g., midday) and reduce usage during peak hours (e.g., evening).
3. Diverse Energy Sources: Expanding beyond solar power to include other renewables like wind, geothermal, or hydroelectric energy can help smooth out the energy supply. Wind, for instance, often generates more power in the evening, complementing solar energy production.
4. Grid Modernisation: Smart grid technologies, which use sensors and automated controls, can help balance supply and demand more effectively. These technologies can direct power where it’s needed most and make the grid more responsive to fluctuations in demand and generation.
   
   

The Path Forward
The duck curve is a natural consequence of our transition to cleaner energy, and it highlights the importance of creating a more flexible and resilient energy grid. By investing in energy storage, modernising infrastructure, and diversifying energy sources, we can overcome the challenges posed by the duck curve and accelerate the shift toward a more sustainable future.
As more regions adopt renewable energy on a larger scale, managing the duck curve will become increasingly vital to ensuring that our energy systems remain reliable, affordable, and green.