In an electrical age which has been dominated by fossil fuels and nuclear power, one thing that is seldom mentioned is rotational inertia.
Inertia from rotating machines provides the residual stabilizing few seconds for grid operators to correct frequency problems. In those seconds, inertia provides frequency stability and enables the power system to maintain its operational frequency level — 60 Hz per second in the United States, and 50 Hz per second in Europe and much of Asia.
Without inertia — either due to production variations or load shedding — sudden changes in frequency will become faster and larger, meaning the residual time will be much reduced and the normal range of variation will be increased largely.
Grid operators can’t fix a frequency problem in an existing system without employing ancillary services. If frequent variation isn’t corrected, things will fall apart. In this situation the electrical system fails, possibly with a cascading effect.
In the fossil fuel and nuclear world, there is no shortage of inertia, which derives from rotating machinery (i.e. turbines and generators). In the renewables world, inverter-controlled solar panels have no moving machinery, so no inertia. Wind turbines have many rotating masses (rotor, gearbox and generator) to produce inertia but an inverter, located between rotor and grid, prevents the kinetic energy of the rotating mass from providing inertia during a period of frequency change.
Unlike conventional hydropower, inverter-controlled, free-flow river turbines in development will produce power without inertia, and make grid frequency unstable and unreliable.
As more inertia-lacking power is loaded on a grid system, frequency becomes unstable, and it must be corrected with ancillary services, elaborate power electronics — if you will, a synthetic solution to save the system. Germany is facing an inertia crisis and so are many other countries where wind and solar generation are approaching a higher percentage of generation.
Frequency is the sine qua non of all electrical systems, from microgrids to the national grid. If there is no inertia, frequency fails and the power system goes down. Blackout.
Enter a small but tech-savvy company, DDMotion, which has developed a solution to the non-inertia-producing power generators, plus other innovative refinements.
The company, headquartered in Owings Mills, a suburb of Baltimore, offers technology which could radically improve harnessing systems for renewables and bring down the cost. It could facilitate the operation of microgrids and open the way to the large-scale use of rivers to generate grid-compatible baseload electricity, according to the company.
The secret to the DDMotion solution is “producing constant speed,” its president and chief scientist, Key Han, told me. He has been working for decades on infinitely variable transmissions (IVTs) that will convert variable input to a constant-speed output.
During the first decade of research, Han worked on a purely mechanical system. But his research has evolved into an electrical power generation system directed at producing a constant speed from a variable input, where with, say wind turbines, much of the equipment in the nacelle can be eliminated, and the balance will be situated on the ground for easy installation, repair or maintenance.
The company explains, “The DDMotion system eliminates the elements in the traditional designs that most frequently fail and that are expensive to fix. Specifically, the DDMotion architecture eliminates the power converter which grooms the frequency of the electricity harnessed by wind turbines [rotors, gearbox, and generators].”
That feature, Han told me, is what makes its system financially attractive to manufacturers, along with the advantage of not needing ancillary services for the grid operators. What is more: The power converters and the gearboxes are the components with the highest failure rates and downtimes, he said.
DDMotion speed-controlled systems are scalable and can be applied for harnessing the untapped energy of non-powered dams, small streams and big rivers. The final goal is harnessing practically unlimited ocean current energy, according to Han.
DDMotion has been largely supported by Alfred Berkeley, chairman of Princeton Capital Management and a legend in the financial community. He served as president of Nasdaq and later as its vice chairman.
Han, who holds many patents relating to his work on infinitely variable motion controls, began his career at General Electric before founding DDMotion in 1990.
A native of South Korea, Han attended college in Montana so that he could fulfill his dream of becoming a professional cowboy. His resume includes roping and branding calves one summer.
Han, a student of Confucius and Aristotle, told me, “You can learn how to be happy from Aristotle.”
