Grid Parity, Nanotechnology and Electrical Energy Storage

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By Dr. Mark Daugherty, CTO of Enable IPC
We have all grown comfortable with the astounding rate of progress occurring in the semiconductor industry. We know Moore's Law, which predicts a doubling of performance every two years, is still going strong. Sometimes we forget photovoltaic panels are also semiconductor devices. While there are obvious differences between integrated circuits and photovoltaic panels, there is at least one similarity: an enormous amount of potential in the photovoltaic industry to reduce costs by applying technology to get more performance from less material.

Grid parity is a term used to define the point at which photovoltaic electricity is the same price as grid electricity. It is also the point at which demand for photovoltaic electricity goes ballistic. If you had to guess when do you think this would happen? 2030? 2050? It might surprise you to learn that President George W. Bush has set 2015 as a goal for grid parity in the United States.

General Electric's Chief Engineer Jim Lyons is also on board. He recently told a room of conference attendees in London that he expects price parity in sunny parts of the United States to occur by around 2015. Several photovoltaic manufacturing companies are targeting grid parity even sooner. Last November, Google announced it plans to spend hundreds of millions of dollars on a project called "Renewable Energy Cheaper Than Coal."

Photovoltaic electricity costs are dropping by around five percent a year, and non-subsidized grid parity is already a reality in parts of California. It has also been reached in Hawaii and other islands that otherwise use diesel fuel to produce electricity. Photovoltaic panel production has been doubling every two years, increasing by an average of 48 percent each year since 2002. According to preliminary figures, by the end of 2007, cumulative global production was 12,400 MW. Roughly 90 percent of this generating capacity goes into grid-tied electrical systems.

How will the grid need to evolve to accommodate all of this solar electricity? Given the intermittent nature of solar power it is clear that energy storage will become a critical enabling technology at some point in the not-too-distant future. While hydropower provides exceptional energy storage capabilities, there isn't much else out there.

One possible alternative is ultracapacitors. While ultracapacitors are related to batteries, they use a different energy storage mechanism. Batteries move charged chemical species (ions) from one electrode to another through an electrolyte. The ions interact chemically with the electrodes to store energy. Batteries store chemical energy and the reactions occurring at the electrodes are never completely reversible. Ultracapacitors store electrical charge physically, without using chemical reactions. Because the charge is stored physically, the process is highly reversible and millions of discharge-charge cycles are possible.

Current ultracapacitor technology has lower energy storage per unit volume than batteries. On the positive side, ultracapacitor power densities are significantly higher than batteries, and ultracapacitor lifetimes are measured in millions of charge/discharge cycles rather than the thousands of cycles rechargeable batteries are capable of. Ultracapacitors also require virtually no maintenance and work well over broad temperature ranges.

Because of their long lifetimes and high power levels, ultracapacitors are expected to first enter the large-scale power markets to provide grid stability. While ultracapacitors are currently far too expensive to consider for bulk grid scale electrical energy storage, that may not always be the case.

Ultracapacitors share an important property with semiconductors and photovoltaic panels. They are amenable to the application of technology, nanotech in this case, to dramatically improve performance without significantly increasing material costs. To put it another way, nanotechnology might enable ultracapacitors to jump on the Moore's Law bandwagon and follow integrated circuits and photovoltaic panels down rapidly decreasing cost curves until they become commercially viable, even at grid scale. If that happens, a completely renewable electrical grid may not be too hard to imagine.

Dr. Mark Daugherty is the CTO of Enable IPC. Though not limited to nanotechnology or the energy industries, Enable IPC's growing portfolio currently includes the exclusive rights to two break-through energy technologies. More information on Enable IPC can be found at www.enableipc.com.

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