Friday, February 6, 2009

Renewable Energy Storage

Finding efficient, cost effective ways to store energy is crucial to the future of renewables. Energy storage would stabilize supplies of electricity and enable us to manage the fluctuations inherent in the power production profiles of many renewables.

In an article entitled 'The Element That Could Change the World' , Jim Kelly senior vice president of transmission and distribution at Edison was quoted as saying.“For most of us right now, the real key to effective storage is batteries. And Nick d'Arbeloff, executive director of the New England Clean Energy Council took it one step further saying, "Storage is a critical component. As a technology area ripe for innovation and investment, it's huge - it's a holy grail,"

Specifically, what is needed is a battery that can store enough energy to manage sporadic supply. These storage devices must be able to be charge and discharge large amounts of energy. “We want to make renewables truly dispatchable* so we can deliver given amounts of electricity at a given time,” says Imre Gyuk, manager of energy systems research at the U.S. Department of Energy. "Without storage, renewables will find it hard to make it big,” Gyuk says

The common battery relies on toxic chemicals and is expensive, bulky, and has a limited life span. But there are alternatives and utilities have been using other storage techniques for decades. An Ars Technica article reviewed five promising energy storage technologies.

Hydrogen Chemical Storage: One alternative to the toxic chemicals in regular batteries is hydrogen, which can be produced from water by electrolysis and then fed into a fuel cell later to produce power. The Department of Energy was already looking into this in 2004 (PDF) as part of the much-hyped hydrogen economy. However its reliance on fresh water may constitute a problem.

Charge Storage: At present there are two experimental mechanisms for storing a charge directly, supercapacitors are replacements for current battery technology and high-temperature superconductors are for transmitting electricity.

Compressed Air: Air can be pumped into airtight geologic formations using excess generating capacity. At times of high demand, the air can be used to turn turbines. A single plant is in operation in Alabama and the Iowa Stored Energy Park is slated to open in Iowa in 2011. However finding suitable geology may present a problem.

Mechanical Energy: Mechanical energy storage is already on the market in the form of flywheels. The primary downside of these flywheels is the precision manufacturing needed to fit the tolerances demanded of something that has to spin fast enough to store significant amounts of energy. It's possible that economies of scale can drive these costs down.

Solar Thermal: Insulation is already mass produced, and doesn't have any moving parts to wear out. The National Solar Thermal Test Facility uses mirrors to heat molten salt, which then transfers the heat to a conventional steam generator. With proper insulation, the molten salt can easily retain the heat for generation well after the sun has set.

As reported in Discover Magazine, "Another promising solution on the horizon is an obscure piece of technology known as the vanadium redox flow battery. This unusual battery was invented more than 20 years ago by Maria Skyllas-Kazacos. The vanadium battery can absorb and release huge amounts of electricity quickly and have a virtually infinite life span. Several promising battery technologies are already in early-stage commercialization, but the vanadium battery may have the edge in terms of scalability and economy."

Sumitomo Electric Industries, sells the vanadium redox flow battery in Japan since 2000. Outside of Japan, Vancouver's VRB Power Systems owns the intellectual property rights to the technology. However, price remains a problem ($500 per kilowatt-hour). According to the Discovery article, it would cost $2.4 billion to run a city of 250,000 for 24 hours off a vanadium battery.

Advances have been made in cutting costs and making the venadium redox flow battery smaller. The prototype 5-kilowatt battery stack is the size of a filing cabinet and fits in a household closet. Configured as part of a home-based generation system, it could absorb power from rooftop solar panels and discharge electricity during peak periods. Skyllas-Kazacos estimates that such a consumer-use vanadium battery might eventually sell for around $5,000. (A price that could pay for itself in a few years).

The greatest challenge to the vanadium battery may come from other batteries like sodium-sulfur technology but it doesn’t work well at sizes below 1 megawatt. For smaller applications, such as regulating the flow of electricity from a house’s solar panels, vanadium-based systems look more cost-effective. They can be fit to more modest demands by using smaller tanks.

At MIT fuel cells with catalyst researchers Nocera and Kanan say they have discovered a simple, inexpensive, highly efficient process for storing solar energy. According to an MIT article, Nocera and Kanan were inspired by a photosynthesis like process that will "allow the sun's energy to be used to split water into hydrogen and oxygen gases. Later, the oxygen and hydrogen may be recombined inside a fuel cell, creating carbon-free electricity to power a house or electric car, day or night. James Barber, a leader in the study of photosynthesis who was not involved in this research, called the discovery by Nocera and Kanan a 'giant leap' toward generating clean, carbon-free energy on a massive scale." "This is a major discovery with enormous implications for the future prosperity of humankind," said Barber, the Ernst Chain Professor of Biochemistry at Imperial College London. "The importance of their discovery cannot be overstated since it opens up the door for developing new technologies for energy production thus reducing our dependence for fossil fuels and addressing the global climate change problem."

In the US, Obama's emphasis on renewable energy should translate into growth for battery and fuel cell technology companies. At present Obama's commitment to hybrids and specifically to plug-ins electric vehicles favors companies working with lithium-ion batteries. Johnson Controls (JCI Quote) may turn out to be the exclusive provider of high-powered Li-ion batteries for domestic cars. Valence Technologies (VLNC Quote), is an up and coming company that may see significant growth. Energy storage companies that are able to reduce costs and increase efficiency can expect to see the most growth.

Jim Kelly of Southern California Edison says, “Five years from now that will seem so trivial. It’s like comparing the first personal computer you had with the ones we have today. You look back and laugh. I think we’ll see that same thing happen with the battery industry. We are taking baby steps, in part because the industry is not mature, the technology winners have not been determined, and the costs are still high. But these are all the things you expect as a revolution happens.”

Energy storage is crucial to the future of energy management and can be expected to grow alongside renewables. Solar, wind and tidal power all confront a similar challenge when it comes to energy storage. Stabilizing a future national grid that draws its power from renewable sources depends on improving our energy storage capabilities. In the absence of an extraordinary technological breakthrough, it is entirely possible that we will employ a mixture of technologies. However, turning renewable energy into mainstream sources of power will require cheap and efficient ways to store large amounts of energy.

*dispatchable means that means it can be controlled from second to second to keep the grid balanced, so the amount of energy being put into the wires exactly matches demand. If the grid goes out of balance, power surges can damage transmission lines and equipment. Generators are therefore designed to protect themselves by going off-line if the grid becomes unstable. Sometimes this can amplify a small fluctuation into a cascading disaster, which is what happened in the northeastern United States and eastern Canada in August 2003, plunging 50 million people into a blackout. Unless the reliability of renewable energy sources can be improved, as these sources contribute more and more electricity to the grid, engineers will have an increasingly difficult time keeping the system balanced.


BeyondGreen said...

We need to do everything in our power to reduce our dependence on foreign oil.We have so much available to use such as wind and solar as well as technologies to reduce our dependence on fossil fuels. There could be no better investment in than to invest in energy independence. Create clean cheap energy,create millions of BADLY needed new green jobs, and reduce our dependence on foreign oil.The high cost of fuel this past year did serious damage to our society and economy. Record numbers of jobs and homes have been lost due to the direct impact on our economy.Oil is finite.We are using it globally at the rate of 2 X faster than new oil is being discovered. Added to the strain on our supplies foreign countries are bursting in populations and becoming modern.China and India alone are expected to add another 3 million vehicles to their highways in the next 2 decades. I just read a fantastic book called The Manhattan Project of 2009 Energy Independence Now by Jeff Wilson.Great Book!

SBC said...

Excellent points and a great book recommendation. Thanks for your comments.