Solar Power and Grid Stability: Scenarios and solutions

hawaii.gridx299Renewable energy is often intermittent, and that variability presents a variety of challenges to power grids. The nature and magnitude of the challenges depends on the time frame — from fractions of a second to seasonal or even multiyear variations — as well as the nature of the grid itself. The latter is evident in two of my articles from last week looking at how seconds-to-minutes fluctuations in solar power complicate grid controllers’ efforts to maintain alternating current at the 60 hertz frequency and the roughly 110 volt power levels required by North American devices.

Fluctuating AC frequency stars in my Technology Review dispatch from the paradise of Kauai, where the island utility is riding an electrical roller coaster as it pushes solar towards 80 percent of peak power flows. Clouds form around the Hawaiian islands’ mile-high peaks and wreak havoc as they float over solar farms, eliminating three-quarters of their generation in less than a minute. On Kauai’s tiny island grid the resulting power supply dips are deep enough to slow down Kauai’s handful of diesel-fuelled generators, causing the AC frequency to crash below 60 hertz.

My story tracks the Kauai Island Electric Cooperative’s hitherto troubled experience with using batteries to smooth out the solar power flows. Discharging a first set of batteries to fill the solar power gaps burned out the battery cells.

Larger continental grids experience solar power quite differently, as I described last week in IEEE Spectrum. Fluctuating output from even the biggest solar farms has little impact on a big grid’s AC frequency, which is maintained by the collective momentum of literally hundreds of conventional power plants spinning in sync. However, fluctuating output from lots of small rooftop solar systems can cause gyrating voltage on a big grid’s local distribution lines.

My piece for Spectrum shows how California is empowering solar systems to solve the voltage problem. The inverters that turn each system’s DC output into AC power for the grid are being deputized to serve as miniature grid regulators that monitor and dynamically adjust the voltage levels on the local lines.

California’s ‘smart inverters’ mark an about-face in how grid operators think about distributed power generation, and are definitely a good-news story. As reader @etlipman commented: “You know exciting changes are afoot when regulators and utilities that have in the past perceived something as a nuisance are starting to see it as asset!”

Germany’s Grid: Renewables-Rich and Rock-Solid

Grid graph German Energy TransitionLast Friday Germany’s grid regulator released the 2013 data for grid reliability, and the figures have renewable energy advocates crowing. The latest numbers (released in German) reveal no sign of growing instability despite record levels of renewable energy on the grid — 28.5 percent of the power supplied in the first half of 2014. In fact, Germany’s grid is one of the world’s most reliable. Continue reading

Amid Blackouts, India’s New Leader Vows 24-7 Power for All

Blackouts this week in New Delhi and surrounding states are providing a dramatic backdrop for a bold promise by India’s new prime minister, Narendra Modi, whose Hindu nationalist party swept to power in a landslide election last month. As a scorching heatwave drove power consumption beyond the grid’s capacity, Modi’s government vowed to deliver “round-the-clock power for all by 2022,” reports the Wall Street Journal.

That will be an awesome task. Nearly one-quarter of India’s 1.26 billion citizens lack grid access. And India’s utilities have struggled to keep up with demand from those who are connected. Power cuts are frequent. Continue reading

Seattle’s Bullitt Center Shines

Online at Architectural Record:

The designers of Seattle’s Bullitt Center have overachieved. The designers set out to demonstrate that a six-story office building could generate all of the energy it needs, but after one year of operation, it is sending a sizable energy surplus to the local power grid, according to data released by its developer, the Bullitt Foundation.

Consumption is simply far lower than what its architects and engineers projected for the 52,000-square-foot building. Instead of using 16kBtu per square foot—half the energy-use intensity (EUI) of Seattle’s best-performing office building—consumption during its first year was just 10kBtu/sf …

read on

Minnesota Finds Net Metering Undervalues Rooftop Solar

Utilities should be paying more for their customers’ surplus solar power generation according to a solar pricing scheme approved by Minnesota’s Public Utility Commission last month and expected to be finalized in early April. Minnesota’s move marks the first state-level application of the ‘value of solar’ approach, which sets a price by accounting for rooftop solar power’s net benefits, pioneered by the municipal utility in Austin, TX.

Minnesota is one of 43 U.S. states that requires utilities to pay retail rates for surplus solar power that their customers put on the grid. Utilities across the U.S. are fighting such net metering rules, arguing that they fail to compensate the utility for services that their grid provides to the distributed generator. So last year pro-solar activists and politicians in Minnesota called the utilities’ bluff, passing legislation tasking the state’s Department of Commerce with calculating the true value of rooftop solar power. Continue reading

AC/DC 101

Much of your editor’s reporting in 2012 focused on the re-emergence of direct current or DC power — through pieces in IEEE Spectrum, Technology Review, and Power & Energy Magazine — and there is more in the works. Some of you, however, may still be wondering what DC power is and how it differs from the alternating current or AC power flowing from most electrical sockets. So here are some answers.

The questions were posed by Andrew Huang, a 9th grader at High Technology High School in Lincroft, NJ, who recently interviewed me for a history project on Nikola Tesla and Thomas Edison’s late-19th Century War of Currents. (Check out The Oatmeal’s Why Nikola Tesla was the greatest geek who ever lived for a rather tilted yet entertaining take on a key combattant in this epic tech tussle.)

What are some differences between the physics of AC and DC? Continue reading

The Debate: Fracking and the Future of Energy

France 24 Energy in 2013 DebateThe Arctic is melting faster than predicted. Is now the time to shut down the low-carbon nuclear power plants in France — the 20th Century’s staunchest proponent of nuclear energy? Is natural gas produced via hydraulic fracturing or ‘fracking’ a gift that is buying time for a transition to renewable energy or a curse that reinforces fossil fuel dependence? Will carbon belching heavyweights such as the U.S. and China ever get serious about cleaning up their energy systems?

Such questions are top order in France, whose President kicked off a Grand Débat on energy this month Continue reading