1. •Why is Storage Important
•How Much Storage is Needed
•Why is Storage so Hard
•Possible Futures
2. National Renewable Energy Laboratories
Website is http://www.nrel.gov
Ludington Power Storage information is
directly from Consumers Energy website -
http://www.consumersenergy.com/content.aspx?id=1830
Energy for Future Presidents –
Richard Muller
Simple web searchs for the rest
3. Study about impact of different renewable levels
Looked at 20% to 90% renewable levels in the
electrical grid
Study got lots of media attention
Reporting was mostly superficial
Study is very impressive and well done
May be a bit optimistic on two points
It does not model the effect of day to day changes
Loss of base load efficiency may reduce CO2 reduction
4. Variable generation – covers offshore/onshore
wind, solar photovoltic (PV), and solar thermal
Overnight capital cost – cost of building a plant if
you could do it in a single day
Capital Recovery Factor – multiplier against
overnight capital cost to get yearly cost
Dispatchable – generator runs when requested
Curtailment – when a generator produces energy
that the grid must refuse
5. Several reasons
Geography – grid cannot move the energy to
where it could be used
Temporal – grid cannot store the energy to use at
a better time
Quality – voltage or wave pattern are wrong
Curtailment is a very bad thing
Economic value not who gets paid
6.
7. • Electrical usage is about 40% of total US
energy consumption
• Only 34% of CO2 emissions
• US uses 2300 trillion watt hours in a year
8. Ludington is about 1.8
GWatts
27 Billion gallons
More than 8 hours of storage
1000 acres
9% of US storage
Opened in 1973
Largest storage site in the
world when new
Now the second largest in US,
fifth in the world
Bath County VA is largest at 3
GWatts
9. Many countries adding wind and solar PV
Many states have renewable energy mandates
Emphasis is on wind, solar, and biomass
Local production is also given special treatment
Wind and solar are variable driven by Mother
Nature
If you don't need the power when it comes, too
bad
Storage lets you use the power when needed
10. GE recently announced a battery option for
their 1.6 Megawatt Wind Turbine
Standard version stores 50 KWHours
How much is that in hours?
11. GE recently announced a battery option for
their 1.6 Megawatt Wind Turbine
Standard version stores 50 KWHours
How much is that in hours?
About 2 minutes
12. Minute by Minute
Solar PV most sensitive
Hour by Hour
Solar PV and Wind both
Day by Day
All Solar and Wind
Seasonal
Mostly Solar but Wind to a limited extent
13. The grid distributes power at light speed
Speed of light in copper not in a vacuum
Sudden changes in load or in demand cause
variations in voltage
Tight limits on what is allowed
Minor variations cause local issues
Major variations can cause blackouts
Today's grid has little need for large scale
storage
Built to match yesterday's technology
14. Baseload Power – Plants run 24/7/365
Nukes, most hydro and coal plants
Load Following – Many plants run some part
of most days
Small coal, some hydro, gas combined cycle,
biomass
Peakers – Plants run during the biggest loads
Open cycle gas turbines
Even some oil-fired plants for the hottest days
15. Load on the grid changes with day and time
Biggest change is day to night
Night load is 50 to 60 percent of weekday load
Next is workday to weekend day
Weekend day is about 75 percent of workday
Last is normal day to hot day
Depends strongly on region – Not sure how much
16.
17.
18. Another problem is sudden changes
From NREL, ERCOT load with simulated wind
19. Four ways to handle variable generation
Over-engineer and accept curtailment at times
Load management to reduce peaks and valleys
Move electricity between regions
Store energy at valleys and release at peaks
20.
21. 5.5% curtailment at 80% renewable load
100 terawatt hours lost per year
At 5 cents per kilowatt hour, $5 Billion dollars
22. 5.5% curtailment at 80% renewable load
100 terawatt hours lost per year
At 5 cents per kilowatt hour, $5 Billion dollars
100% increase in load management
23. 5.5% curtailment at 80% renewable load
100 terawatt hours lost per year
At 5 cents per kilowatt hour, $5 Billion dollars
100% increase in load management
100% increase in high tension lines
24. 5.5% curtailment at 80% renewable load
100 terawatt hours lost per year
At 5 cents per kilowatt hour, $5 Billion dollars
100% increase in load management
100% increase in high tension lines
400% to 650% increase in storage
From 20 GWatts to 100-150 Gwatts
Store/release 200 to 300 terawatt hours per year
25.
26. As a result of the modeling assumptions, most of the new storage is CAES;
however, the tradeoff between CAES and PSH is largely due to the data
limitations in the ReEDS model, where the vast majority of potential PSH in
much of the United States was not evaluated. In addition, the relative risk
associated with CAES versus PSH was not considered. PSH is a proven tech-
nology, while CAES has yet to be deployed in either bedded salt or in porous
rock formations, which represents a large fraction of assumed deployments.
The limited deployment of batteries estimated by ReEDS is due to their high
cost and assumed minimal projected cost reduction over time as well as to a
lack of full valuation of their benefits to bulk power and distribution systems.
Overall, ReEDS results demonstrate an obvious discrepancy with relative histor-
ical and proposed deployment of these technologies, where PSH dominates.
The analysis of energy storage technologies for RE Futures demonstrates the
need for more comprehensive estimates of the cost and resource availability for
both CAES and PSH, as well as a more complete assessment of the various
benefits of energy storage as renewable energy penetrations increase.
27. Storage needs lots of usage to be practical
Outside edges of the curve are rare
But the right side of the curve has more power
than it might appear
28. Assuming a fixed life and KWh dominates
(OCC*CRF + FOM)/(8.760*UR) + CEI/EFF
OCC – Overnight Capital Cost per KWh
CRF – Capital Recovery Factor
FOM – Fixed Operations and Maintenance
8.760 – Hours in a year/100
CEI – Cost of energy coming in
EFF – Efficiency of the storage
UR – Utilization Rate in Percent
29. (OCC*CRF + FOM)/(8.760*UR) + CEI/EFF
Ludington is about $100 per KWh
CRF is based on useful years and interest rate -
.054 for 50 years, .36 for 3 years
FOM is usually between 1 and 10 percent of
OCC – pumped hydro is the lowest
(100 * .054 + 1)/(8.76 * .25) = 2.9 ¢/KWh
(4.0 / .85) = 4.7 ¢/KWh
Call it 7.6 cents per Kwh
30. Pumped hydro runs around $100 per KWh but
$2000 per KW
For every 6 KWHours, we need $2000 of KW
capacity
2000/6 is 333
(333 * .054 + 1)/(8.76 * .25) = 8.7 ¢/KWh
(4.0 / .85) = 4.7 ¢/KWh
Call it 13.5 cents per Kwh
31. Ludington is already cost effective
Even before Wind and Solar were common
Ludington was built
Getting an $800 Million upgrade to be more
valuable in the age of Variable Generation
32. Ludington is marginal, nearly not worth it
Pumped hydro has scaling issues
No such thing as a small pumped hydro station
Years to build
Limited locations
Many locations have environmental issues
They don't store as much as it sounds
Ludington stores 3 percent of what Michigan uses
All types of storage have issues
33. (OCC*CRF + FOM)/(8.760*UR) + CEI/EFF
(333 * .054 + 1)/(8.76 * .25) = 8.7 ¢/KWh
(17.94 + 1 )/(8.76 * .25)
(4.0 / .85) = 4.7 ¢/KWh
First component most important
Need to keep OCC and CRF down
Nice to keep FOM down as well
Need to keep UR up
Second component less critical
Curtailment implies a very low value for CEI
34. Time of day shifting – output runs 6 hours a day
6/24 is .25
Day to day shifting – output runs 10 hours but only
every third day
10/24 * .333 is about .14
Seasonal shifting – output runs 10 hours a day but
only 25 percent of the year
10/24 * .25 is about .10 but not full power
Closer to .05 or .06
35. Hardest area to estimate
NREL report suggests 100 to 150 GWHours
I think they are optimistic
Their daily wind and solar numbers too steady
I think we will need twice as much
100 to 150 GWHours for time shifting
100 to 150 GWHours for day to day smoothing
Fossil fuel usage will be a bit higher without this
Today we only have about 20 GWHours
36. Energy density
Power density
Environmental impact
Scale issues
Use of rare/sensitive
materials
Efficiency
Responsiveness
Energy loss over time
Capital cost
Operating and
maintenance cost
Useful lifetime
Energy Stored Over
Investment - ESOI
37. Capital Cost
Very important – running $333 for grid storage
Operating and Maintenance Cost
Also important – pumped hydro is very low
Useful Lifetime
Long life time is critical – pumped hydro is 30+ years
Environmental Impact
Needs to be low as possible – Pumped hydro is bad
38. Energy Density
Not very important – Pumped hydro is really bad
Power Density
Somewhat important – Pumped hydro is fair here
Scale Issues
Important to get off the ground
Efficiency
Important but less than you might think
39. Use of rare/sensitive materials
May be critical as grid storage is huge
Responsiveness
Pumped hydro is 2 or 3 minutes so not a big issue
Energy loss over time
Low levels are ok but high levels are not
Energy Stored Over Investment (ESOI)
Need to beat lead-acid batteries at 3- but don't
need to beat pumped hydro at 100+
40. Potential energy has low energy density
1 foot-pound is 0.000376616097 watt hours
1 gallon 300 feet up is .9 watt hours
Chemical bonds are higher energy density
Battery powered cars go up hills lifting
The batteries
The car
Passengers
Fuels like gasoline are even higher
6 gallons will push many cars further than a Tesla S
41.
42. Stores electrical energy directly with minimal
conversion cost
Very fast charging and energy release
Does not store much power
Does not scale well
Leaks power over time
Good choice for second by second grid
stability
43. Graphene based supercapacitor announced
Very early days
Improved energy density – 60 KWhrs per liter
Very good for a supercapacitor
Very low for a battery
Low leakage
No idea about price yet
44. Store energy in a large rotating high density
wheel
Very fast response
Does not scale very well
Leaks energy but slowly
Good for both S/S and M/M grid stability
storage
In use as grid storage in some locations
45. Store energy as heat – liquid salt
Good energy density
Leak rate depends on quality of
insulation
Day to Day is possible
Week long is hard but doable
Longer is probably out of reach
Integrates especially well with Concentrating
Solar Power (CSP)
46. Recovery of Power takes time
Use molten salt to boil water and spin turbines
Needs some amount of water
Does not scale down well
Square-Cube impact on doubling size
Looks good for day level and week level
storage
Cost structure is unclear
47. Store energy by lifting something up
Comes in several forms
Costs are low but so is energy density
48. Ludington is a perfect example
Big plant requiring lots of area and volume
Needs lots of elevation near large body of water
Takes about one minute to spin up
Subhydro is pumped hydro upside down
Large storage tanks at the bottom of the ocean
Really big tanks mostly made out of concrete
All moving parts underwater
Maintenance costs could be a killer
49. Slate (www.slate.com) had a posting about
using rail tracks
Sounds good where pumped hydro is out
But find a train that weighs as much as Ludington
Find a location where rock comes to the
surface
Cut away a big cube and build motors underneath
Lift it up to store energy and lower to retrieve
50. Abbreviates to CAES
Many designs out there
Because temperature, pressure, volume are
related CAES is an engineering challenge
Some grid storage already
Large scale usually means pressurizing a cavern
Finding good locations is hard
Only been done a few times, cost is unclear
51. Store into high pressure cylinders
Split the heat away and store separately
One example is Lightsail
Energy density is 13 gallons per KWh
Better than pumped hydro, worse than most batteries
Store into tanks underwater
Hydrostor is trying this out near Toronto
Not clear what the advantage would be
52. There is more than one battery chemistry
Batteries have been researched for years
No silver bullets but some possibilities
Good points
Good energy density
Mostly good power density and responsiveness
Good efficiency
Pretty scalable
53. Bad points
Some types use rare or dangerous metals
Most don't last many cycles
Some need high temperatures
54. Well researched
Lead can be dangerous
Poor and uncertain cycle lifetime
Bad ESOI – 2 to 3
55. High quality lithium ores are rare
Cost is pretty high
Fire risk not entirely understood
Energy density is pretty good
Power density is worse than lead acid but
pretty good
56. High operating temperature
Good energy density and power density
Common materials
No long term risk to ecology
Expensive but might improve with scale
Current models have fire hazard
57. EOS Energy Storage is a new player
Impressive but unproven claims
Cost - $1000/KW and $160/KWh
30 year lifetime with one full cycle per day
High energy density
Fast response
At least fair power density
Main materials are cheap
and non-toxic
58. Storing Excess Variable Generation as Fuel
Not biomass!
Direct conversion of wind, solar PV or solar
thermal into fuel
Done in the laboratory
Nothing scales today
59. Electrolysis is well understood
Currently requires rare materials
Hydrogen gets lots of press
Poor energy density when a gas even pressurized
Liquified hydrogen is dangerous and inefficient
Many metals turn brittle with long exposure
Hydrogen can be mixed with methane
Works well with our current infrastructure
May be limited to 10-20%
60. Starts with Methane – CH4
Works well with current infrastructure
Not the best energy density
Ethane – C2H6
More changes needed in infrastructure
Energy density improves
Propane – C3H8
Changes needed same as ethane
Energy density still improving
61. Methanol – CH3OH
Good energy density
Moderately toxic but by-products are not an issue
Ethanol - CH5OH
Better energy density
Not toxic in low concentrations
Propanol CH7OH
Don't know much about this
62. Ammonia – NH4
Seriously toxic in moderate to high concentrations
Good energy density
Important precursor in agricultural usage
63. Old Model
Storage lets utilities have a higher percentage of
base load
Storage needed to be efficient since the input had
marginal value
Few surprises so cheap KWHours was more
important than cheap KW
64. New Model
Storage lets utilities avoid curtailment
Less important to be efficient because input
would be wasted without storage
Sudden increases and decreases in Variable
Generation are common
Cheap KW more important than cheap KWHours
65. We don't see any big advances in grid level
storage
Pumped hydro and underground CAES are the
only workable solutions
Both are expensive and take years to build
Hard to see how NREL 80% can happen in their
timeframe
Getting 400% to 650% increase in storage is necessary
but not sufficient in their vision
Need to build multiple plants at the same time
66. At least one technology improves grid storage
economics substantially
Supercapacitor, zinc air, CAES, or something else
NREL 80% target much easier to make
Still need to redo the electrical grid
Reduces US CO2 emissions about 29%