Rumble Royale: Can the U.S. Grid Work With 100% Renewables?

Four Days in 2055: Dynamic heat and power supply in the mid-century wind, water and sunlight-fuelled Continental U.S. simulated by Stanford’s Mark Jacobson. Credit: ASU/PNAS

A battle royale between competing visions for the future of energy blew open today on the pages of a venerable science journal. The conflict pits 21 climate and power system experts against Stanford University civil and environmental engineer Mark Jacobson and his vision of a world fuelled 100 percent by renewable solar, wind, and hydroelectric energy. The criticism of his “wind, water and sun” solution and an unapologetic rebuttal from Jacobson and three Stanford colleagues appear today in the Proceedings of the National Academy of Sciences (PNAS).

The critics enumerate what they view as invalid modeling tools, modeling errors, and “implausible and inadequately supported assumptions” in a projection of the mid-century U.S. energy supply that Jacobson and his coauthors published in PNAS in 2015. “The scenarios of [that paper] can, at best, be described as a poorly executed exploration of an interesting hypothesis,” write the experts, led by Christopher Clack, CEO of power grid modeling firm Vibrant Clean Energy.

Clack says their primary goal is accurate science, the better to equip policymakers for critical decisions: “We’re trying to be scientific about the process and honest about how difficult it could be to move forward.”

The text and statements by Clack’s coauthors question Jacobson’s evaluation of competing energy technologies, and specifically his rejection of two non-renewable energy options: fossil fuel power plants equipped to capture their own carbon dioxide pollution and nuclear reactors.

Jacobson calls Clack’s attack, “the most egregious case of scientific fraud I have encountered in the literature to date.”

In fact, while both sides claim to be objectively weighing the energy options, the arguments and backgrounds of the protagonists belie well-informed affinities for various energy sources (and informed biases against others). As sociologists of science would say, their choice of data and their reading of it reflects hunches, values, and priorities.

Consider Clack’s coauthor Ken Caldeira, a climate scientist at the Carnegie Institution for Science. Caldeira’s press release broadcasting their critique argues that removing carbon dioxide from the U.S. power supply is a massive job demanding the biggest tool box possible: “When you call a plumber to fix a leak, you want her to arrive with a full toolbox and not leave most of her tools at home,” says Caldeira.

The same document then abandons this technology-agnostic tone to call out nuclear energy and carbon capture as technologies that “solving the climate problem will depend on.” And Caldeira has appealed for deploying a new generation of nuclear reactors which he and other nuclear boosters such as former NASA scientist Jim Hansen say are needed because renewables “cannot scale up fast enough.” Continue reading


German Parliament OKs Bold HVDC Grid Upgrade

Germany’s bold transmission plan is a go. The Bundesrat, Germany’s senate, has accepted the plan’s enabling legislation forwarded to it by the Bundestag (Germany’s parliament), according to the authoritative German Energy Blog. There is every reason to expect that the plan’s core element — four high-voltage direct current or HVDC transmission lines profiled by Spectrum last month — will get built.

That is good news for Germany’s grid and those of its neighbors. All are straining to manage powerful and variable flows from the wind turbines and solar panels that provided 12 percent of Germany’s power generation last year.

Elements of both the HVDC system design and the legislation should ease construction of the HVDC systems. On the design side, Germany’s transmission system operators have specified advanced converters whose ability to arrest and clear DC line faults will reduce the risk of running overhead lines. This means the HVDC lines can use existing rights-of-way used by AC lines. In fact, they can be hung from the same towers. Read the May 2013 story for extensive discussion of the advanced modular multilevel converters.

The enabling legislation, meanwhile, will simplify line permitting by making a federal court in Leipzig the only forum for legal disputes concerning the projects. Separate legislation passed by the Bundesrat and Bundestag makes  Germany’s federal networks regulator, the Bundesnetzagentur or BNetzA, the sole permitting authority for power lines that cross Germany’s state or national borders. These measures — for better or worse — cut out state-level officials that face greater pressure from local project opponents and may be more sympathetic to their concerns.

Add it all up and Germany is en route to become the first country with HVDC lines playing a critical role at the core of their power grid. It is arguably the first real challenge to AC’s century-plus reign as the top dog in power transmission since DC-advocate Thomas Edison lost the War of Currents. Tesla and Westinghouse may just be rolling over.

This post was created for Energywise, IEEE Spectrum’s blog on green power, cars and climate

Germany Jumpstarts the Supergrid


Power Core: Spectrum’s infographic take on Germany’s HVDC transmission plans

New developments in high-voltage DC electronics could herald an epic shift in energy delivery

By Peter Fairley

Stuttgart is one of the last places you’d expect to find in a power pinch. This south German city’s massive automotive plants run 24-7 without a hiccup, efficiency measures have held industrial power consumption flat, and solar panels flash from atop its major buildings. But now all that is at risk. The country’s accelerated shift from nuclear power and fossil fuels to renewable resources, such as wind and solar, has exposed a huge gap in its transmission capacity. If they are to survive, Stuttgart’s factories—and power consumers across southern Germany—will need to import a lot more power from the north, and Germany’s grid is already at capacity.

To fill the gap, Germany is considering an aggressive plan that would push high-voltage direct current, or HVDC, from its conventional position on the periphery of AC grids to a central role. The primary reason is simple: For the first time, HVDC seems cheaper than patching up the AC grid. But Germany’s transmission planners also have another motivation: They want to provide as much performance and reliability as they can to an AC grid that’s already strained by excess wind power. For that, they’re considering implementing power electronics that are capable of doing something that’s never before been done on a commercial line: stop DC current in milliseconds flat.

Germany’s plan could mark the beginning of something much bigger: a “supergrid” of inter connected DC lines capable of transporting electricity on a continental scale, ferrying energy from North Sea turbines, dams in Scandinavia, or Mediterranean solar farms to wherever demand is greatest at that moment…

Published in the May issue of IEEE Spectrum. Read the story at

Supergrid Technology Beats Expectations

HVDC breaker Source AlstomAn industrial research consortium that is a who’s-who of the European power industry says development of technologies to produce high-voltage DC (HVDC) supergrids accelerated in 2012 — “surpassing expectations.” The assessment comes in the supergrids technology roadmap updated earlier this month by Friends of the Supergrid, whose members include power equipment suppliers such as Siemens, ABB and Alstom, as well as transmission system operators and renewable energy developers.

Summarizing the conclusions of an expert group within the International Council on Large Electric Systems — better known as CIGRE, its French acroynm — the Friends of the Supergrid says there is now no doubt as to the feasibility of HVDC networks ferrying renewable energy resources from wherever they are in surplus to wherever they are needed: “CIGRE Working Group B4–52 considered this question, specifically whether it was technically and economically feasible to build a DC Grid, and the answer was yes.” Continue reading