You
can’t run a 24/7 power system on intermittent renewables like wind and solar.
They
won’t keep the lights on.
But
the Islands are building intermittent renewables like mad, and leaving legacy
fossil fuel plants to back them up. Ultimately, that’s neither sustainable nor
in line with state policy.
The
next few RaisingIslands posts will review how the paradigm is changing. The key
to the change is the fast-moving new world of energy storage.
With
appropriate storage, intermittent power becomes firm power. Oil and coal plants
can go away.
Our
primary sources for this series are a four-day conference on utility-scale
energy storage research and a new industry/government report, the DOE/EPRI/NRECAElectricity Storage Handbook for 2013, which was released earlier this summer.
If
you’re interested, you should read the report, as we’re only going to summarize
pieces of it here.
As
little as 10 years ago, there was very little choice available in terms of
energy storage—most folks were getting by with lead-acid batteries, although
there was a lot of “potential” out there for different storage technologies.
That
has changed.
“Storage
for frequency regulation has become fully commercial and facilities are being
built to explore renewable integration, PV smoothing, peak shifting, load
following and the use of storage for emergency preparedness,” wrote Imre Gyuk, of
the U.S. Department of Energy’s Energy Storage Program, in the foreword to the
report.
The
Hawai`i Clean Energy Initiative plays a role in the story, and is cited in the
report.
What
quickly becomes clear when you pay attention to energy storage is that this
field is dense, complex and difficult to summarize, other than to say there’s a
lot going on.
Most
folks think about storage and think batteries, and indeed, batteries are a key
piece—perhaps the biggest piece. But they’re certainly not all of it. There is
also, flywheel energy storage, compressed air energy storage (CAES), pumped
hydropower, thermal storage, and hydrogen.
Each
of these technologies has strengths and most also have significant weaknesses.
Some are appropriate for certain applications but not for others. Balancing
those features is both difficult and necessary to move forward.
There
are many issues in deciding whether a new system is ready for prime time. Here
are some of them, which I drew from my participation in a June conference in
Newport Beach, “Massive Energy Storage for the Broader Use of Renewable Energy
Sources.”
This
list is largely designed to rank battery storage systems, but much of it can be
applied to any storage technology.
The
dream energy storage system of the future needs to be:
Made
of cheap materials;
Efficient,
in that you get nearly as much energy out as you put in—preferably 80 percent round-trip
efficiency or better;
Safe,
in that it won’t explode, leak, or otherwise endanger those in the immediate vicinity;
Have
charge-discharge capacities of approaching 10,000 times;
Energy
dense, so it is compact (although this is more important for mobile systems like
electric car batteries than stationary utility-scale storage, it can't take up too much acreage);
Made
of non-toxic compounds;
Recyclable
at the end of its useful life;
Able
to operate at ambient temperatures.
Oh,
and it needs to be far cheaper than anything available today. The U.S.
Department of Energy’s ARPA-E program is looking for batteries in the $100 per
kilowatt-hour range. Most of the cheapest technologies available today are in
the range of 5 to 10 times that...or more.
Can
we get there? In this series we’ll take a look.
(ARPA-E stands for Advanced Research Projects Agency-Energy. It is a Department of Energy program modeled on the Department of Defense's DARPA, the Defense Advanced Research Projects Agency.)
©
Jan TenBruggencate 2013
1 comment:
Energy storage is a complex subject and there are many ways to calculate its value.
There is the capacity per cycle times its lifetime # of cycles. Or there is the actual cost per kWh stored regardless of the capacity of the storage medium.
In distributed solar energy systems, the important cost is the cost of lifetime kWh capacity, because it is very difficult to actually calculate how much electricity is actually stored, because it is going in and out of the battery under many complex sets of conditions. The solar PV feeds the battery but it also feeds the inverter for ongoing electrical use during the day.
The most important thing about storage is how little do you actually need in order to maximize self-consumption and autonomy while also maximizing the life of the battery.
FYI, I just purchased four L16 flooded lead acid batteries for ~300 each. Together they amount to a nominal 10.08 kWh of storage (12 VDC x 840 AH at the 20 hour rate - more at a slower rate).
With these batteries you have to de-rate them by 50% in order to maximize their life so it is more realistically ~5 kWh of storage.
My last set lasted for 7 years at about 250 50% cycles annually. That comes out to about 8750 kWh stored or $0.13/kWh stored.
However, I cannot supply exact figure as to how much was stored and how much was used during the day. That is an automatic balancing act based on very complex and varying conditions.
That is why I have instead learned to size the battery according to optimal operating conditions. Experience demonstrates that it is a ratio of generated energy to stored energy that gives the best and most cost-effective solution.
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