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​Reliable energy: Balancing supply and demand
Just as a tightrope walker must maintain balance to guarantee a successful and safe high-wire crossing, so too must power grid operators maintain a delicate balance, accurately matching supply with demand and carefully preparing for their next move. Hydropower’s many positive attributes, coupled with careful planning and precise management, make this power resource one of most reliable. Here are a few reasons why.

It’s always on

Renewable resources aren’t often associated with reliability because their generation depends on Mother Nature. But unlike many other renewables, Northwest hydropower is dependable and predictable. The water cycle constantly replenishes the fuel source of the Columbia River Basin, which receives significant runoff from mountain snowmelt. With such a plentiful fuel source, hydropower serves most of the region’s power needs year round, 24/7. Hydropower is the only renewable resource that excels at producing such a high and continuous electrical output.

It follows demand

Hydro is a “load following” resource. That is, it can throttle up or down to
match the daily peaks and valleys of our energy use – increasing in the morning when people start the day, and decreasing in the evening as people wind down. Operators control the electrical output by choosing how much water to allow through the water intakes in the dam. Opening and closing the intakes directly controls the amount of water flowing to the turbines, which determines the amount of electricity the dam is generating.

You can save it for later

One of the greatest challenges of electrical systems is that energy has to be consumed as soon as it’s produced – it can’t be stored and saved for later. But hydropower offers the next best thing. Storage reservoirs behind dams in the Columbia River Basin can store up to 30 percent of an average year’s runoff. These reservoirs act like batteries by storing energy (or in this case, water) when it’s not needed, and releasing it later when there’s more power demand.
Hydropower operators can also plan ahead for seasonal changes.  Generally, operators in the Columbia Basin will fill reservoirs during the wetter months in preparation for drier conditions.

It can quickly change output

Hydropower plants are nimble enough to ramp up and down within minutes, or even seconds. This means they are ideal resources for meeting one of the requirements of electrical systems: The amount of power entering the transmission grid must equal the amount being consumed at all times. An imbalance can cause generating units to react by increasing or decreasing their rotational speed, or frequency, which should always be at 60 hertz. If not corrected, the generator could fall offline or even trigger a cascading outage. Hydropower can respond to imbalances from moment to moment, always keeping the system in balance.

It’s a self-starter

In the event of a system-wide blackout, utilities need access to black start capability – the ability to start a generator in the absence of an outside power source. Just as a car needs a jump start when it has a dead battery, most types of generators need an external power supply to return to operation. Hydropower plants are the only large-scale generators that can dispatch power to the grid immediately when all other sources are inaccessible.