In commercial-scale electricity generation, the duck curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and renewable energy production. In many energy markets the peak demand occurs after sunset, when solar power is no longer available. In locations where a substantial amount of solar electric capacity has been installed, the amount of power that must be generated from sources other than solar or wind displays a rapid increase around sunset and peaks in the mid-evening hours, producing a graph that resembles the silhouette of a duck. In Hawaii, significant adoption of solar generation has led to the more pronounced curve known as the Nessie curve.
Without any form of energy storage, after times of high solar generation generating companies must rapidly increase power output around the time of sunset to compensate for the loss of solar generation, a major concern for grid operators where there is rapid growth of photovoltaics. Storage can fix these issues if it can be implemented. Flywheels have shown to provide excellent frequency regulation. Short term use batteries, at a large enough scale of use, can help to flatten the duck curve and prevent generator use fluctuation and can help to maintain voltage profile. However, cost is a major limiting factor for energy storage as each technique is expensive to produce at scale and comparatively not energy dense compared to liquid fossil fuels.
The term was coined in 2008 by the National Renewable Energy Laboratory.
Video Duck curve
Mitigation strategies
Methods for coping with the rapid increase in demand at sunset reflected in the duck curve, which becomes more serious as the penetration of solar generation grows, include:
- Installing more dispatchable generation
- Orienting some solar collectors toward the west to maximize generation near sunset.
- Energy storage including:
- Pumped-storage hydroelectricity
- Battery storage power stations
- Solar thermal energy with thermal energy storage
- Ice storage air conditioning
- Use of batteries in electric vehicles for temporary storage (vehicle-to-grid)
- Energy demand management, including:
- Transitioning to more efficient lighting systems, such as compact fluorescent and LED lighting
- time-of-use pricing (TOU) and real-time pricing
- Smart grid technology
A major challenge is deploying mitigating capacity at a rate that keeps up with the growth of solar energy production. The effects of the duck curve have happened faster than anticipated.
The Economics Behind the California Duck Curve:
The California Independent System Operator (CAISO) has been monitoring and analyzing the Duck Curve and its future expectations for about a half a century now and their biggest finding is the growing gap between morning and evening hours prices relative to midday hours prices. According to their last study, the U.S. Energy Information Administration, found that the wholesale energy market prices over the past six months during the 5 p.m. to 8 p.m. period (the "neck" of the duck) have increased to $60 per megawatt-hour, compared to about $35 per megawatt-hour in the same time frame in 2016. However, on the other side they have measured a drastic decrease in the midday prices, nearing $15 per megawatt-hour. These high peaks and deep valleys are only showing continues trends of going further apart making this Duck Curve even more prevalent as our renewable energy production continues to grow.
To understand these deep valleys and the high peaks we need to look at many different variables that go into the renewable energy grid. The green resources such as solar, wind, geothermal, and hydroelectric are increasingly satisfying California's total electricity needs. Green energy is abundant, which has become an economic issue on the time of use front. However, as of now, the technology that has been implemented puts a lot of control into consumers which leads to issues amongst different operating conditions. In order for it to run smoothly this would require flexible resource potentials to guarantee reliability from the renewable energy grid. The idea of reliability is one of the biggest issues facing the green energy market. Intermittency, "occurring at irregular intervals; not continuous or steady" leads to skepticism by consumers. If they are going to be transferring into the renewable grid then they must be guaranteed a constant stream of energy at a price/rate that can be maintained, but the Duck Curve issues is proving just the opposite.
A critical part of this curve comes from the "Net load," net load is the difference between expected load and anticipated electricity production from the range of renewable energy sources. In certain times of the year (namely Spring and Summer), the curves create a "belly" appearance in the midday that then drastically increases portraying an "arch" similar to the neck of a duck, consequently the name "The Duck Chart." During the midday mass amounts of solar energy is created but because of this, people require much less energy during the day. This is when the issue with lack of battery storage comes into play. We have enough solar technology to power the world, but we have very little infrastructure that would enable us to store it to be used later. So, we have an oversupply of energy at a time when demand is low and an inverse issue of lack of supply when demand is high due to lack of storage availability. This is why prices are so high at those peak times.
Maps Duck curve
References
External links
- Energy Storage and the California "Duck Curve"
Source of the article : Wikipedia
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