Most electricity is generated by
converting kinetic energy from steam, moving water or moving air to electricity
using a generator. Mechanical energy storage involves adding potential energy
to water, air or a mechanical storage medium and when desired, releasing it as
kinetic energy to turn a generator to generate electricity. These systems have
a startup time that is generally slower than EES systems however they are
commonly characterized by having a very large capacity (Abele,
Elkind, Intrator, & Washom, 2011) .
The round trip efficiencies are
heavily dependent on the ability to add the potential energy from the storage
medium and then use the energy to create electricity. As most of mechanical
energy storage devices turn a generator they often produce alternating current
(AC) electricity which is compatible with most electric grids. The direct production
of AC electricity also avoids efficiency loses resulting from inverting direct
current electricity to AC.
On a personal note, I tend to be
more interested in mechanical energy storage. One reason is that I am a
mechanical engineer by training and have an admitted bias towards mechanical
systems as they are easier for me to understand and more familiar to me than
electrochemical systems. This personal bias aside, electrochemical energy storage
systems tend to use rather novel, often toxic, significantly impactful
chemicals in their storage medium. The extraction, refinement, processing and
disposal of these chemicals can be energy intensive and present significant
issues related to toxicity, waste management and land use from mining. In a
recent study at Stanford university, researchers found that compared to a
pumped hydro system (a mechanical energy storage device), lead-acid,
lithium-ion, sodium-sulfur, vanadium-redox and zinc-bromine electrochemical
energy storage devices had a significantly larger negative impact on the
environment to produce the same amount of power and energy (Shwartz, 2013) . Though all storage technologies will
be necessary to move towards the idealized goal of supporting large scale
renewable energy deployment, I believe that mechanical energy storage will be
the dominant method for large scale energy storage.
As I add posts reviewing different
energy storage devices in the category of Mechanical Energy Storage devices I
will add a link to that post below:
Works Cited
Abele, A., Elkind, E., Intrator, J., & Washom, B.
(2011). 2020 Strategic Analysis of Energy Storage in California. Los
Angeles: California Energy Commission. Publication Number: CEC-500-2011-047.
Shwartz, M. (2013, March 5). Stanford scientists
calculate the carbon footprint of grid-scale battery technologies.
Retrieved October 1, 2013, from Stanford News:
http://news.stanford.edu/news/2013/march/store-electric-grid-030513.html
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