There are many myths floating around the grid. Most stem from a lack of understanding of how the grid works. How many of these myths have you heard? I'll provide a quick answer here, and link to more detailed explanations,
Myth: Storage is something new that has to be added to the grid for renewable power.
Reality: There has always been energy storage in the grid. Short-term storage in the form of inertia was part of the first generators that powered the first power systems. Pumped hydroelectric storage was introduced in Europe in the 1890s and in the United States in 1929.
Today, worldwide, and not counting very short-term storage, there is about 175.8 GW of storage power. Total energy is difficult to characterize, as pumped hydro reservoirs can be quite large, while some battery systems may support as little as 15 minutes at rated maximum power.
In the United States today, there is about 25.2 GW of installed storage, and about 2.5% of power is stored before delivery. In Europe, the figure is 10%, and Japan, 15%. The United States lags behind in storage.
See Grid for Beginners: Storage
Myth: Wind and solar cannot ramp up to meet unexpected demand.
Reality: Neither can any other power source—if already being operated at 100% capacity. With thermal or hydro, operating at less of 100% capacity is called "reserve". People often give fossil fuels, hydro, and nuclear a pass on this, and assume incorrectly that renewables must always operate at 100% capacity. No grid can operate with any reliability in that mode, no matter the energy source.
In the US, standards were set by FERC back in 2012 for how this should operate, culminating with a full-scale test in August 2016 by CAISO, the National Energy Reliability Laboratory, and First Solar at one of their 300 MW solar arrays. Because of the use of electronic inverters, solar and wind (and battery storage) can provide advanced grid stability services that are difficult or impossible to provide with other sources.
It is not usually done today, because wind and solar are usually displacing more expensive sources, and the use of batteries usually makes more economic sense, allowing a higher capacity factor throughout the grid.
Myth: The reason the grid needs storage is that wind and solar are intermittent.
Reality: When a generator goes offline for any reason, or is brought online, a corresponding amount of power must be added or removed elsewhere in the system to stay in balance. This can be by adding or removing generation, or from stored power.
A 3 GW fossil fuel plant that goes offline, must be replaced with 3 GW of power. When one 100 MW wind farm shuts down due to low wind, you only need to make up 100 MW, and it doesn't happen all at once. It is only when many wind and solar facilities are located in a small enough area to experience the same weather, that their impact on grid stability begins to equal that of a large fossil fuel plant.
The fact that wind, solar, and batteries can respond quickly to fluctuations allows them to help stabilize grid voltage and frequency.
See: Grid for Beginners: Reserves, Failures, and Recoveries.
Myth: There are only a few storage options available today.
Reality: There are many storage options covering a wide range of time scales and purposes. While usually, people think of storage in terms of storage for hours to days, shorter-term storage is more critical to grid stability. The longer-term storage allows generators, including wind and solar but also fossil fuel, to operate at a higher capacity factor, greatly improving the economics.
Most installed battery storage to date is largely fulfilling either a reserve power role, or ancillary services such as voltage and frequency support, up/down regulation, phase compensation, and similar. Batteries perform these jobs much better and more economically than the alternatives. An example is reserve power. Being able to replace a failed coal plant at a moment's notice while allowing an orderly switchover, has a high value, because it keeps the grid operating, without consuming fuel having a plant on hot standby. The battery saves both the cost of the plant and the fuel.
The benefits in these usages can far outweigh the benefits from power arbitrage, shifting power from when it's plentiful to when it's less available.
Here are some of the deployed options (dates are approximate):
| Type | Introduced | Time scale | Role | Notes |
| Generator Inertia | First generator | seconds | Voltage and frequency stability | Inherent, but can be augmented with a flywheel |
| Synchronous Condenser | Early | seconds | Voltage and frequency stability, phase correction | Essentially an undriven generator |
| Capacitor | ≤1932 | milliseconds | Phase correction | |
| Inductor | milliseconds | Phase correction | Less common because transformers, generators, and motors are inductive. | |
| SVC | 1970s | milliseconds | Phase correction, transients | Energy stored in inductors and capacitors. |
| STATCOM | 1970s | milliseconds and up | Voltage and frequency stability, Phase correction, transients | Energy stored in a larger capacitor and/or battery |
| Flywheel | milliseconds to minutes | Voltage and frequency support | ||
| Wind Turbine Blades | 2017 | milliseconds to minutes | Voltage and frequency support | The capability has always been there, but requires that inverters support this kind of dispatch, and the grid operators be able to request it. |
| Ultracapacitor | 2013 | seconds | Voltage support for variable loads | Transportation w/ acceleration and deceleration |
| Advanced Lead-acid | 2013 | minutes to hours | Voltage support, reserve power | Probably obsolete even with advanced lead-acid |
| Lithium-ion | 2013 | minutes to hours | All storage roles except long-term | Currently dominant type. Many manufacturers |
| Sodium-sulfur | 2013 | minutes to hours | All storage roles | Sodium is cheap. Flow battery |
| Zinc-chlorine | 2013 | minutes to hours | All storage roles | Flow Battery |
| Vanadium redox | 2013 | minutes to hours | All storage roles | Flow Battery. Current largest battery in Dalian, China |
| Compressed air | 1978, 1991 | days | Only two built to date, using salt caverns. Development is being done on more flexible locations | |
| Thermal power | 1981 | ~ 1 day | baseload | Usually associated with concentrated solar, but can be used independently |
| Thermal heat/chill | 2011 | ~ 1 day | Heating and cooling | Used to shift the load rather than the power |
| Vehicle charging | 2012 | hours | Transportation | Load shifting |
| Hydrogen | 2013 | days-years | Long-term reserves | To date, only the production side is in operation; the hydrogen adds to the natural gas supply |
Myth: Grid batteries are small.
Myth: Germany's adoption of renewables has been a disaster/has raised prices.
Reality: While Germany has set itself a major challenge, simultaneously closing coal and nuclear plants, renewables are not a disaster for Germany.
Leaving aside the question of whether they will meet their stated targets, they are in fact closing nuclear plants and re
reducing CO2 emissions, though clearly much more slowly than if they did not close the nuclear plants.
Here's Germany's power mix over time:
As you can see, Germany's power production has increased, but fossil fuel use has declined, and renewables are expanding more rapidly than ever.
In 2010, before the push to close plants and build renewables, the average day-ahead wholesale price was €45.55. In 2018 it was €43.26. Germany's power exports have grown during this period.
Remember, too, that power generation is just a fraction of the retail prices of electricity. In most cases, the costs of transmission, distribution, and taxes predominate in retail prices.
This is not what failure looks like. As Germany cuts more deeply into their nuclear fleet, they will face additional challenges. That it can be done is not in question. What remains to be seen is at what pace, and at what final cost.
Myth: Renewables have made South Australia's power grid fragile and caused power outages.
Reality: This is pretty far from the truth. It is part misunderstanding, and part political ploy in favor of continued coal production.
The view is grounded in a major blackout in South Australia in 2016, after two tornadoes tore apart the transmission system 40 seconds and 170 km apart. Wind farms tried repeatedly to reset as the grid failed, but some were configured to give up after 9 tries. The underlying cause was that the grid did not have enough intertia to carry it through the necessary steps to handle the disruption, and the wind farms were not configured to provide it, nor to survive the grid failures.
They did not cause the grid failures, but if they had been configured differently, the blackout might not have happened. (There was additional damage after, so survival is not certain).
I cover this in more detail in Grid for Beginners: Elon Musk's Bet
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