Taking Control of Renewables

By  Azeez Mohammed, president & CEO, GE’s Power Conversion business

November 16, 2017

 

The renewables revolution is in full swing, and a closer look reveals growth figures that speak volumes. At a global level, the International Energy Agency (IEA) forecasts that renewable electricity capacity will expand by nearly 1,400 gigawatts through 2025 (source: IEA WEO 2017). This is set to boost the share of renewables in power generation to 31 percent by 2025. Looking at solar power specifically, the sector is entering a new era, as it will represent the largest annual capacity additions for renewables through 2025. All of this is against a backdrop of a worldwide increase in overall power generation predicted by the U.S. Energy Information Administration that will see nearly a doubling in output from 13.8 terawatt hours (TWh) in 2016 to 26.5 TWh by 2040 in non-OECD countries alone.

 Today, solar has already reached the tipping point in some parts of the world. For example, Dubai’s iconic Mohammed bin Rashid Al Maktoum Solar Park has reached 2.99 cents per kilowatt-hour in terms of cost of electricity, making solar power generation more competitive than coal in the region. Multiple distributed solar systems and other renewables are also on the rise. These are often working in hybrid combinations and even, sometimes, incorporate “traditional” rotating generators. It’s a radical switch that demands new technology and fresh thinking to smoothly deliver dispatchable power as it’s needed—to, across and outward from grids.

How intermittent sources rewrite the rules

While fossil fuel-based power generation has been around for decades, the increase in renewables penetration is relatively recent. Such rapid change means that operators of infrastructure primarily designed for fossil-fuel generation—especially at grid level—have been caught off guard.

Connecting power to where it’s needed, grids are the blood vessels of today’s power ecosystem. However, the intermittent renewables source has raised clear challenges to grid integration and its stability.

The advantage of coal, oil or gas power generation is that while it cannot be turned on or off easily as demand dictates, the rotating turbines and generators have a lot of built-in inertia. This means a long lead time to ramp up and down, even under fault conditions. The result is a “stiff grid” that makes managing any “trip out” easier.

However, the intermittence of natural power—such as unpredictable wind and sun that inherently can’t shine round the clock—changes the rules of the dispatchable power game. Interruptions or fluctuations in power/voltage occur within seconds, and a full trip out can even create a challenging “cascade effect” when demand overwhelms power source capacity plant by plant, like falling dominoes.

As the power generation landscape is being reinvented around renewables, so are national grid codes that define performance—especially in countries with weaker grid infrastructure, which are changing in response to this new power generation mix. These grid codes specify the power quality of electricity that plant and grid technologies must deliver—both in normal operation and under fault conditions—and are now giving rise to a range of creative solutions such as GE’s “rotating stabilizer.”

Leveraging GE’s vast experience in variable speed drive and rotating machine technology, the solution helps to replicate the stability provided by traditional thermal power generation to smooth the peaks and troughs that are intrinsic to renewables output as well as provide a high inertia generation source even under fault conditions. The solution can also be easily and quickly connected or disconnected with the grid via converters, which can help reduce the overall cost of maintaining compliance with the latest grid codes.

Honing in on digital solutions

The need for instant additional power on a grid is not new, with the renewables factor now encouraging some in the industry to reassess one effective old solution: pump storage. This proven method of dispatchable power management has involved pumping water off peak from lower to higher levels in traditional hydro-electric settings for some 100 years—ready for release to generate power when needed. Pump storage 2.0 is now seeing generators starting to explore its potential near smaller renewable sites. However, the higher capex and more complex environmental considerations involved mean pump storage is no panacea.

Cutting-edge battery storage on the other hand offers the advantage of being easily scalable and manageable. Leveraging the latest lithium-ion technology, this enables batteries to be used to deliver stabilizing power instantly across grids or to generate it afresh—in effect behaving like a large, traditional rotating generator.

While batteries offer exciting opportunities to store and deliver power, sophisticated new digital techniques now extend their control potential to help maximize grid stability as well as optimize energy production and usage in terms of both supply and demand. Artificial intelligence that leverages digital control and monitoring plus big data analytics is already well on the way to reshaping a smart grid future.

As renewables further evolve and expand and hybrid systems play a bigger role, GE’s digital technology will continue to develop new ways of maximizing its contribution across global grids. Look out for my forthcoming article on how digitization is supporting dispatchable power in this new distributed era.

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