Where Can We Put It?
A Solution To Storing Excess Renewable Energy Using Batteries
Abstract
Since the 1800s, the battery has been known to be the ultimate means of storing electrical
energy. Over the years, batteries have changed and are still useful in most technological areas.
Due to their versatile design, batteries can be used in everything from a small electronic device
like a cell phone, to a source of power for an electric vehicle. The next possibility is using
batteries to help renewable energy take over as the world’s primary means of electrical
generation.
Key Words
Renewable
Energy
Batteries
Prepared by Andrew J. Logan
Author Biography
Andrew is currently a Junior studying Electrical Engineering at USC’s Viterbi School of
Engineering. He plans to finish his degree in 2013 and go on to either research alternative energy
or continue on to graduate school.
Contact Information
AndrewJL@USC.edu
(303) 594-1016
Prepared for: Marc Aubertin, Writing 340 Professor Section 66804
USC Viterbi School of Engineering
And Illumin
“May the wind always be at your back. May the Sun shine warm upon your face.”
-
From an old Irish Blessing
Sometimes, however, the wind is not blowing and sometimes the Sun is not shining.
When looking at shifting from fossil fuels to renewable such as wind or solar, these facts become
very important in the design and integration of alternative energy technology. For the current and
past systems, utilizing fossil fuels, this was never a problem because the fuels were available
when needed. However, due to unchangeable conditions like the rotation of the Earth and the
climate in various regions, we cannot control the energy produced using renewable technology.
Therefore, to combat this challenge, much research has gone into power storage [1]. The most
common way to store power for the last couple
hundred years started with Alessandro Volta and the
construction of the Voltaic Pile [2], which would
eventually lead into battery cells starting in 1836 and
all the way to today’s batteries.
Batteries are used in everything from small
electronics (phones, computers, etc.) to electric
vehicles. Their importance can spread far into other
realms of technology, like the area of renewable
energy generation. Whereas batteries themselves are
not new technology, consideration needs to go into
what they can be used for in the future. One
possibility, the one presented in this article, is the use
How A Battery Works
Figure 1. The electrons, shown in pink,
flow from the negatively charged anode
on the bottom to the positively charged
cathode on the top. They are created
from the chemical reaction in the battery
and can only flow when a circuit is
completed from the anode to the
cathode. [3]
of batteries for power storage from alternative energy sources, like solar and wind. With
continuing research on increasing storage capacity, creating more powerful cells, and
considering new designs, batteries have much potential for helping create a cleaner, more
efficient world in the area of energy and power generation.
How They Do What They Do
Batteries are in almost every handheld device on the market for consumers. They come in
many shapes, sizes, uses, and ranges of output. However, all of them work in the same basic
manner. As shown in Figure 1, electrons created in the battery flow through the wire to whatever
the battery is powering (in this case, a light bulb.) This is a simplistic model of a battery, but a
concept all batteries use for producing energy. For rechargeable batteries, this same process
works in reverse when the battery is being charged. Beyond the basic charging and discharging,
different batteries use different metals and compounds for different features including: energy
density (how much energy can be stored), how lightweight the materials are, and the rate at
which the materials promote different rates of charging and discharging. For example, batteries
used in cell phones and laptop computers are made of lightweight materials with high energy
densities to make those devices portable and small. As a trade-off, these devices do not last as
long. However, if they were made to last longer, laptops could have ended up staying the same
size as the first portable computers (weighing about 20 pounds), even with advances in all of the
other technology in a computer. The designs of earlier batteries were simple and followed a
design similar to the voltaic pile, in terms of stacking the cathode, electrolyte, and anode. Also,
over the years, researchers have found the best chemicals to use for electrolytes. A typical
household battery like a AA uses manganese dioxide whereas the original voltaic pile used brine,
which is water that is saturated with salt. They have also found the best metals to use which are
inexpensive, but still able to build up and carry the most charge. The types of metals vary with
the different types of batteries, which are discussed further in a later section.
How Powerful They Are
To the drag team, shown in
Figure 2, batteries are what make their
races successful. Currently, this
specific motorcycle holds the world
record as the quickest electric vehicle
of any kind. The motorcycle, called the
KillaCycle®, is completely powered by
batteries, can be standing still and
accelerate to 60 miles-per-hour in less
than a second [4]. The batteries used to
The KillaCycle®
Figure 2. The powerful batteries in the motorcycle allow it to reach
speeds of over 150 miles-per-hour in less than 10 seconds and at a
distance of only one-fourth of a mile [4]! Fully electric, it can still
show power comparable to its fossil fuel counterparts.
power the bike are the same kinds that power some cordless power tools. To compare this power
with fossil fuels, only drag-racing vehicles can achieve this same acceleration. However, this
motorcycle only uses about $0.07 worth of fuel (in this case electricity), whereas the average
dragster can use over $200 of nitro-methane fuel [4]. Now take a step back and think if the
energy in those batteries was also generated by renewable sources. That would make each run a
really clean ride in terms of the environment. One minor drawback to an electric motor, however,
is the horsepower compared to a fossil-fuel dragster which can exceed 5000 horsepower. The
electric drag motorcycle in Figure 2 still boasts over 500 horsepower. This may not be enough to
replace some ships engines which can put out about 3700 horsepower [8], but it is plenty to
replace engines in many passenger vehicles and even some trucks.
Batteries can provide enough clean power to race a motorcycle and power some vehicles,
but also plenty to power a phone for more than a day. Due to this versatility, batteries have
already shown their dynamic utility, and, therefore are not a farfetched solution to storing large
amounts of power from wind or solar sources. There are also many different types of batteries
which can be used to store different amounts of power in different places. As previously stated,
batteries come in many shapes, sizes and capabilities, which include batteries that would suit the
storage of excess renewable energy. The batteries used in smaller electronics give up cycle life
for size. In the case of these larger-scale batteries, size would not be as much of an issue.
Therefore, batteries with better cycle lives could be used without considering size or weight.
Types of Batteries
Where it might be possible to have a very large array of AA batteries stacked in a large
warehouse somewhere, it would probably be more efficient and useful to choose a battery that
suits the situation. Many batteries are made from very rare metals or toxic chemicals because
those materials work well together to create a voltage and discharge at a given rate. For example,
alkaline batteries have potassium hydroxide as part of the chemical process. The battery casing is
made out of metal, but it is not entirely indestructible. Over time, the casing can become brittle
or break under pressure or heat. If the potassium hydroxide did manage to leak, it is a very
corrosive acid that can cause severe chemical burns [9]. Due to the toxicity and rarity of the
materials for some batteries, research has gone into finding alternatives for those batteries. One
of those successes is the battery commonly found in cell phones. It no longer uses any toxic
chemicals as an electrolyte. Instead, these batteries, Lithium-Ion batteries, rely on the highly
reactive lithium metal which can store energy in its atomic bonds [10]. These batteries are very
safe chemically, but they still have problems with the highly reactive elements used in the
battery. The elements can cause a combustive reaction, but they are very rare [10]. With research
also came other batteries like Lead Acid and Capacitive batteries. These are two batteries which
are very useful with applications in storing large
amounts of power for low cost.
Lead Acid batteries are the oldest type of
rechargeable batteries (see Figure 3) [6]. The reason
that they were replaced in most devices was the fact
that toxic chemicals and metals are used in the
batteries. However, these are still the most widely
used batteries in most automobiles because of their
low cost and long life. Eventually, these may be
replaced with a more environmentally friendly
battery, like a Lithium-ion battery, but are much
cheaper for the time being. The problem, beyond the
environmental issue, is that these batteries are very
Different Batteries
Figure 3. The larger battery picture above is a
Lead Acid battery most commonly used in
automobiles. The ultracapacitor battery is
pictured below that and may be the future of
batteries. [5]
hard to recharge if they become completely
discharged. However, they still provide a viable
option considering their reliability when charged and
the amount of energy that they can store.
Capacitive batteries, on the
other hand, may not be able to hold as
much energy in the space provided,
but they are environmentally friendly.
They are not composed of any type of
toxic chemical or rare metal and they
may have an even longer life than the
Lead Acid battery. This type of
Nanoscale Capacitor
Figure 4. Many of the visible features in this picture (i.e. the
spaces between the capacitive plates) are only a few microns,
which is one one-millionth of a meter. This being done allows for
capacitors to be made using dimensions that were previously
thought to be improbably achieved.
battery is still under a lot of research
and has not yet replaced all other types
of batteries, but they are expected to
perform as well as most batteries on the market [5]. They also provide another low-cost solution.
They are lightweight enough and low profile to replace batteries in small electronics, they are
made of environmentally friendly materials, and they can hold enough energy to contain excess
from renewable energy generation. These may be the future of batteries in most electronics, large
and small. They can also be made into nanoscale capacitive batteries to make batteries even
smaller. This is achieved using the growing field of nanofabrication. With it, capacitors can be
created like the ones pictured in Figure 4. Capacitors are better with more surface area for each
plate and with a small distance in between each plate. Due to the advances in fabrication
processes, these two features can be achieved with much more ease than using larger plates for
capacitors. Hopefully, these will be able to provide an alternative to the more unfriendly batteries
like the lead acid batteries. Also, there will continue to be more research on new battery
technology that may surpass even the theoretical usefulness of the capacitive batteries.
Conclusion
Whether or not renewable energy generation will need to utilize battery storage in the future,
batteries already posses the capability of doing so. Since so much research has gone into creating better
batteries, the technology already existed as the need arose. Batteries are so versatile and powerful that
they have the ability to replace the energy source for almost any electronic device that currently receives
power from a more conventional, but less environmental, source. Their simple design makes them easy to
use, their composition allows for them to store and release large amounts of energy, and their composition
also allows for clean and safe use. Batteries can help make the idea of clean energy more realistic and
help it move along faster.
References
[1] J. Luoma. “The Challenge for Green Energy: How to store Excess Electricity.” Yale Environment 360. [On-Line]
Available: E360.yale.edu/content/feature.msp?id=2170.
[2] M. Bellis. “Battery: History Timeline of the Battery.” About.com Inventors. [On-Line] Available:
Inventors.about.com/od/bstartinventions/a/History-Of-The-Battery.htm.
[3] Northwestern University Qualitative Reasoning Group. “How do batteries work?” [On-Line] Available:
www.qrg.northwestern.edu/projects/vss/docs/power/2-how-do-batteries-work.html.
[4] “KillaCycle Specs. And the KillaCycle Team.” Killacycle.com. [On-Line] Available: www.killacycle.com/about/.
[5] J. Mulroy. “Nano-scale Ultra Capacitors Challenge the Lithium-Ion Battery.” PC World. [On-Line]. Available:
www.pcworld.com/article/192300/nanoscale_ultra_capacitors_challenge_the_lithium_ion_battery.html.
[6] Cadex Electronics Inc. “What’s the Best Battery?” Battery University. [On-Line]. Available:
http://batteryuniversity.com/learn/article/whats_the_best_battery.
[7] A123 Systems Inc. “Core Technology.” [On-Line]. www.a123systems.com/technology-core.htm.
[8] K. Bonsor. “How Floating cities will work.” [On-line]. Available:
http://science.howstuffworks.com/engineering/structural/floating-city1.htm.
[9] “Remote Power Transfer – the end of batteries.” Childlikes.com. [On-line]. Available:
http://www.childlikes.com/battery.htm.
[10] M. Brain. “How Lithium-ion Batteries Work.” [On-line]. Available:
http://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery.htm.