Feature

Options for energy storage


Joyce Laird

Part 1: There are more storage technologies than one may imagine. Batteries are the primary format, but other technologies are being developed, reports Joyce Laird.

Headquartered in France, SAFT Batteries is a 100 year old company that services a worldwide market. As the company name indicates, its specialisation is batteries: “Our core business is in electrical chemistry, high end/high technology applications,” Michael Lippert, Marketing & Business Development Manager for Energy Storage Systems, says. “One of our strategic developments is energy storage that supports all types of renewable energy sources to the grid.”

Lippert notes that until the intermittency challenge of renewable energy is truly met, all solar and wind will by necessity, be relegated to being ‘supplemental’ energy sources. “Even for residential, they can't carry the full load, and definitely not the full utility load.

Too many things affect their creation of power that is beyond the control of the actual technology. Regardless of how efficient a specific brand of solar panel may be, it still does not produce power at night or whenever the sun is blocked.

Plus, it is not kind to the grid when it does go down or ramp back up. The goal is to make these the main power sources and this can't be done without effective storage and metering of that stored power to the grid.

“Energy storage is not just putting all energy into one big storage tank and then taking it out when needed. We look at it more in the full context. If you are a PV generation plant or wind plant and want to store all the energy that is produced, you would need huge energy storage. That is the future. We will need that in 2020 or beyond, but the more current problem is to eliminate the immediate variability of renewable technology,” Lippert says.

“Currently, we only store 10-20% of the total that the renewable system is generating so it can be drawn on to smooth out the variability of this type of energy generation to the grid. In doing this, we reduce the ramp rate both up and down to increase the even compatibility of the power source with the grid.

“The grid needs what we call ancillary services such as frequency regulation. In a national grid, the more renewables you have feeding into it, the more you need ancillary services,” Lippert explains. “Ours is a different kind of battery because it requires very high power, in the range of tens of Megawatts. SAFT promotes all types of battery storage, but the technology of choice for renewable energy is lithium-ion.” Compared with other types of batteries, lithium-ion is a relatively young technology, but SAFT nonetheless has already invested in these types of batteries for 15 years.

“In Europe we are participating in a project that is called Nice Grid. It is a flat grid project that will be implemented in the South of France. We will be installing storage at three different levels: The transformer level with megawatt storage capability, on the distribution feeder with a couple of hundred kilowatt hours, and in homes,” Lippert says. “The idea here is to have these three different levels along with smart grid technology. We have smart meters between each infrastructure to optimise the energy system flow between the transmission and distribution, between the generation devices, and the storage devices.

“While we were thinking of renewables initially, we are seeing a much bigger picture now. Increasingly, energy management functions that can address all forms of energy generation are needed. This project can handle multiple energy generation sources, but with the difference that it can also be regulated at the local levels.”

Power management

Xtreme Power is one of the pioneers in very focused energy storage and distribution. Headquartered in Kyle, TX, USA, the company has been providing very large-scale, intelligent power management solutions since 2006 – which makes them an ‘old timer’ in this area. Xtreme Power services three large customer groups: Large utility plants such as their project in development with Duke Energy in Texas, independent power producers such as First Wind in Hawaii, and the US military.

“We integrate power electronics, energy storage and our control system, and we manage the balance of plant,” Alan Gotcher, CEO, says. “All our solutions are configurable, modular and can be scaled. We currently have 6 different megawatt scale power management solutions installed or ready for installation. These run from 1 MW up to 36 MW.”

The technology is fairly straightforward. Xtreme Power uses battery technology to store power and control electronics to deliver power. The batteries are sized on a megawatt scale. Power electronics manage the entire system and completely manage the power per unit. A standard module is 11 ft. tall, 11 ft. wide and 20-40 ft. long. One unit would be between 1 MW and 2 MW, holding between one and two hours of storage per unit. Gotcher says that these modules can be placed anywhere as long as they are connected along a transmission/distribution line: Inside a facility, beside the facility or even several miles away.

“We provide what is known as a full four quadrant that can push or pull power; making it real or reactive. It can manage the full pitch and frequency to keep everything within the narrow specs that are needed to deliver power to the end user,” Gotcher says. “We call it a Dynamic Power Resource. It can respond in only 0.03 seconds and it can store energy or energy can be pulled from it. We can handle up to 100 modules simultaneously. The biggest module we support currently is 6 MW. Therefore, currently we can deliver a modular system that can handle 600 MW.”

The benefit for renewables is ramp-rate control – how fast to let the power increase and decrease. A smart storage system addresses the continual variability of both wind and solar power. Excess energy generated during prime time is stored to fill the gap in down time. More importantly, it removes the jolts to the grid, allowing it to ramp up and down in a smooth manner.

“A good example of this is Kahuku Wind on Oahu [Hawaii]. That installation has 12 wind turbines and was generating 30 MW of power when suddenly four of the turbines went off. It was like throwing a light switch. It had an instant 8-MW drop. Now that would harm the grid. But, our system immediately put 8 MW back into the grid from storage and the grid never knew anything had happened while issue was fixed,” Gotcher says.

Currently, Xtreme Power can provide up to four hours of backup power, but Gotcher says that they are working on a technology that will expand this into days within the next year. “In this particular case these are hybrids. We can use two different kinds of batteries; a fuel cell and a battery, or we can use a generator and a battery. It's a matter of what the customer – utility, independent power producer or military – need.”

Part 2 will look at the world of energy storage beyond batteries.

About: Joyce Laird has an extensive background writing about the electronics industry; semiconductor development, R&D, wafer/foundry/IP and device integration into high density circuit designs.

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Comments

ANUMAKONDA JAGADEESH said

07 October 2012
Excellent article on power storage options.
Dr.A.Jagadeesh Nellore(AP),India
E-mail: anumakonda.jagadeesh@gmail.com

ROGER CLARKEJOHNSON said

04 October 2012
Indeed, very informative article Joyce. Like Anonymous, hydroelectric can easily (technically) be developed at tens of thousands of EXISTING irrigation or flood-control dams. It is literally as you said: store THOUSANDS of MW-HOURS in the reservoirs! The biggest obstacle is public opinion and myths surrounding hydro development. Remember: these are EXISTING dams...going unused in terms of energy storage capability. Pumped Storage is the Cadillac of electricity generation and storage schemes, and already widely used, but are more expensive to develop because of civil costs and environmental-activists' resistance. Would they prefer more natural gas, coal, diesel, or nuclear units to provide the back-up power needed to balance intermittent renewable generation?? Also, one thing noticeably absence from the article is the cost/MW-HR of battery/fuel cell storage. Hydro may suddenly become even more attractive when equipment and maintenance costs are compared.

JASMINE WILLIAMS said

03 October 2012
Great article Joyce. I agree that there are more storage technologies than one may imagine! But is there more battery storage than pumped hydro storage? I hope the next article in the series includes ice storage which is widely used and already developed. Can't wait to see your part 2!

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