Wednesday, June 20, 2018

Micro and Macro: What is the Energy Future?

Solar panel on a house roof near Boston
Wikipedia, Gray Watson 
Everybody knows?

Milt Caplan wrote an excellent blog post on the future of energy.   He describes attending an event where

a number of speakers prefaced their comments with statements like “everybody knows the future will be based on distributed generation – primarily with small scale renewables and storage to provide reliability”.  
(Bold in the original)

Is this indeed what everybody knows?  Is there no dissent?

Maybe Microgrids?

As Caplan wrote:
 We have this romantic fantasy that we can live off-grid with a combination of solar power and battery backup.  Of course, with a bit of thought .....we accept that we cannot go it completely alone.  The conclusion being that maybe we need to collaborate with our neighbours and build a small system (or microgrid) to achieve the reliability that we need to power our lives.
As it turns out, I have also been thinking about microgrids. A few days ago,  I heard an excellent talk on smart microgrids by Andy Haun, Chief Technology Officer, Schneider Electric Microgrids Business. These advanced microgrids can be controlled "in parallel" with the grid.  When used in this manner, the smart microgrid systems can avoid costs by shaving peak demand and by using cheaper, off-peak power. The microgrids can be also controlled in an "intentional islanded mode," which is especially useful for storm readiness.

It seemed to me that while these microgrids could be used stand-alone in remote locations, they were mostly going to be used in conjunction with the larger grid.  Or why develop all these "peak shaving" features, and so forth?

It doesn't look to me as if advanced microgrids are going to make the bigger grid obsolete, or at least, not anytime soon.

Maybe Macrogrids? 

Maybe instead of microgrids, we should be looking at really big macro grids?

Many of the renewables advocates who hope for a proliferation of microgrids also hope for long-distance DC lines, to bring bulk power from sunny or windy places to places where more people are living.  Maybe, the answer is long-DC lines to bring energy across the continent, moving energy from sunny and windy areas to big cities.  In other words, really big grids.

Earlier this year, Power Engineering featured an article, Enabling Large Scale Renewables in the Western U.S. This article proposed new, lengthy High Voltage DC lines. These lines had names such as Power from the Prairie, and Centennial West.  The lines seemed primarily designed to move wind energy from the west to the east.  Similarly, in early June, an Wall Street Journal ran an opinion piece titled  Upgrade America's 19th Century Electric Grid.   This article called for a $500 billion dollar infrastructure project to build DC power lines to "transfer energy between power-abundant and power-hungry regions. "

Could this work? Probably not.

Donn Dears wrote a blog post DC Transmission for Cutting CO2 Emissions.  As Dears explains,  HVDC transmission lines are best for moving great quantities of power for long distances; current examples carry hydro power from dams to cities. There are HVDC transmission lines carrying hydro power in the American West (Pacific DC Intertie), and similar lines in China and Brazil.  These lines are fully utilized almost all the time,  because they come from huge hydro systems with more than one power plant.

Such utilization would not be the case for the new DC lines proposed for the US.  They would carry wind and perhaps solar energy, which are not steadily available.  Low utilization rates would lead to higher costs, and DC lines are only cost-effective in limited circumstances to start with. An HVDC build-out would not work.  It would not be cost-effective.

Pursuit of the the Unsuitable

Somehow, in pursuit of renewable energy, microgrids (connected to the main grid) or a huge buildout of continent-spanning DC power lines (connected to the main grid) are considered to be options.  The main grid doesn't go away, but these new features get added.

Now, there are uses for both microgrids and DC lines. Even their proponents, however, are not proposing microgrids and DC lines as a complete substitute for the current grid. At best, they would solve some problems on the grid.  At worst, they would be high-cost, duplicative add-ons to the grid that exists now.

In short, if we want to decarbonize our grid without romantic fantasy and without too much costly duplication,  we need the following:
  • Keep our current fleet of nuclear plants running
  • Build more nuclear plants
  • Build more grid infrastructure, as appropriate.  
  • Don't duplicate infrastructure because "microgrid" or "HVDC" sounds cool.  Add them as needed. 
In other words, for a reasonable future, we must pursue suitable technologies. Technologies such as nuclear energy.

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