NEW GRID-SCALE BATTERY SYSTEMS IN UK FOR SHORT-TERM COUNTING OF WIND / SUN ONE DAY
https://www.windtaskforce.org/profiles/blogs/grid-scale-battery-systems-in-new-england
Wind system paired with grid-scale battery system
Wind output is different from other generators, because it is unpredictable and highly variable; its discontinuity is not the main problem.
Wind provides dry energy, MWh, but not reliable power, MW.
Reliable power is absolutely essential, for any modern grid system, for supply and demand to always match with high accuracy.
Grid-scale battery systems are increasingly being combined with wind systems to reduce adverse effects on grid stability, due to variations in wind output, MW. Under strong wind conditions, the output power of the wind system has a large fluctuation, which can adversely affect the frequency and voltage stability of the power grid.
For example, a utility or grid operator may require a 30 MW wind system with an output variation not exceeding 2 MW/min, up or down, to maintain voltage variations and grid frequency within the specified range. View URLs.
The battery system must be able to charge and discharge to meet the acceleration rates required by the utility, while not overheating the battery.
Overheating will reduce the useful life of the battery and can cause a fire, burning at high temperatures and taking a long time to extinguish.
The battery system is rated to provide an energy level, say 10 MW for 4 hours = 40 MWh, which is AC at the battery voltage, from 100% full to 0% full. The battery will probably be about 60 to 70% full when the wind slope occurs.
The utility allows a maximum downwind ramp of 2 MW/min; if exceeded, it will be necessary to cut down on wind output by feathering the blades. The battery discharge will be 2 MW x 3 minutes/60 = 0.6 MWh, if the downlink lasts 3 minutes.
Round-trip battery system losses, A to Z, are about 18% for new li-ion systems, 20% or more for older systems
MW and MWh of the battery system will be based on the capacity of the wind system, MW
On average, batteries should be charged and discharged to always maintain a certain level of charge to be ready for any uphill and downhill ramps.
In Hawaii, some battery systems caught fire because they charged and discharged too quickly, i.e. they were undersized and/or did not have a proper cooling system.
NOTE: Electric vehicle batteries, in the case of 1) fast charging at the charging station, 2) rapid discharge during acceleration and uphill, 3) frequent “distance driving”, such as making long journeys per day (charge to 95%, discharge to 5%, instead of the recommended 80%/20%), all of which will reduce battery life due to overheating and cell damage; Hot summer days and cold winter days both put a strain on the battery.
NOTE: The report of the National Renewable Energy Laboratory, NREL, addresses the above issues. NREL is a government, pro-wind entity, which tends to see the wind through rose-tinted glass rather than private enterprise.
https://www.nrel.gov/docs/fy14osti/59003.pdf
Solar system paired with grid-scale battery system
Variable clouds are the main reason solar output varies so rapidly, in addition to the usual daily cycle. See pictures
Solar output can be reduced by 60% within a few seconddue to a cloud passing through the solar system.
The time it takes for a cloud to pass depends on the height of the cloud, the height of the sun, and the speed of the wind.
These factors need to be considered regarding solar power output forecasting and variable output integration into the grid.
Graph showing solar output records for ZIP codes in California. The further north, the less solar power.
For example, ZIP code 920 shows a spike from about 115 MW to 65 MW, or 50 MW in 10 seconds, or 300 MW/min, at 1 p.m., which will significantly affect stability frequency and voltage on the grid.
For at least a decade, California has mandated that utility companies install grid-scale battery systems on their distribution systems.
The cost of such battery systems is not charged to solar system owners to perpetuate the “fossil-competitive solar” illusion.
https://www.windtaskforce.org/profiles/blogs/large-scale-solar-plants-require-large-scale-battery-systems
