Transcript NREL Power point slide template - cover and main

Tradeoffs and Synergies between CSP and PV at
High Grid Penetration
*
*
NREL
July 5, 2011
National Renewable Energy Laboratory
Innovation for Our Energy Future
Bottom Line
•
•
As penetration of variable generation (solar, wind)
increase, it is increasingly important to consider the
interaction between these resources and the entire grid
system
Dispatchable energy (e.g. CSP w/storage) has a higher
value than non-dispatchable energy.
–
–
•
At low penetration of solar and wind this difference is small
At higher penetration (15% on an energy basis) this difference
may increase by as much as 4 cents/kWh
Overall penetration of solar energy can be increased by
the use of CSP with storage which provides grid
flexibility
–
Allows for higher levels of PV penetration by providing the
ramping rate and range needed to accommodate the variable
output of PV systems
National Renewable Energy Laboratory
2
Innovation for Our Energy Future
Increase in Energy Value Due to Dispatchability of
Systems with Thermal Energy Storage
Dispatchable solar energy sources:
1. Maintain high energy value
–
Always displaces the highest cost energy sources
2. Maintain high capacity value even at high solar penetration.
3. Lower curtailment than solar systems w/o storage
4. Lower integration/reserve costs
The actual difference in value is largely a function of
penetration and overall grid system flexibility
National Renewable Energy Laboratory
3
Innovation for Our Energy Future
Analytic Methods
•
Detailed grid simulations of the Western Interconnect
–
–
–
–
–
–
•
Two scenarios
–
–
•
Simulates the hourly dispatch of the power plant fleet
Ensures reliability by ensuring availability of operating reserves
Validates basic transmission operability using DC power flow
Enforces power plant constraints including ramp limits, operating
limits
Calculates fuel burn and associated cost and emission
Assumed frictionless markets (best case scenario for PV)
15% PV and 15% wind
10% PV, 5% CSP and 15% wind
Did not capture full range of integration costs due to uncertainty
about reserve requirements of PV, short term variability and
forecast errors – assumed perfect knowledge of solar resource
National Renewable Energy Laboratory
4
Innovation for Our Energy Future
1) Difference in Energy Value
90000
PV
PV10
15%CSP5
PVWind15
No CSP
Example WECC-wide dispatch
during a 4-day period in spring
CSP
80000
Wind
Hydro
70000
PHS/CAES
Other
Biomass
Coal
50000
Nuclear
Dispatch of CSP results in
less high cost gas and
more low cost fuels
Geothermal
40000
Gas
30000
20000
10000
90000
0
1
5
9 13 17 21 1
5
9 13 17 21 1
5
9 13 17 21 1
5
PV
CSP5
Wind15
10%
PV
5% PV10
CSP
9 13 17 21
Wind
80000
Storage enables a relative
fuel savings benefit over PV
of about 0.5 cents/kWh at
$4.50/mmBTU gas
National Renewable Energy Laboratory
Hydro
PHS/CAES
Difference in
gas burn
70000
Other
Biomass
60000
Generation (MW)
Generation (MW)
60000
Coal
Nuclear
50000
Geothermal
CSP
40000
Gas
30000
20000
10000
0
1
5
5
9 13 17 21 1
5
9 13 17 21 1 5
Hour
9 13 17 21 1
5
9 13 17 21
Innovation for Our Energy Future
2) Difference in Capacity Value of PV
Normal peak at ~4-5 pm
At 10% PV, peak is shifted to
8-9 pm. PV provides no
further peak capacity benefits
92000
90000
88000
Net Load
86000
At this point PV cannot
reduce the need for
generation capacity
84000
82000
Normal Load
80000
2%
78000
5%
10%
76000
15%
74000
12
14
16
18
20
Hour (Ending)
22
CSP capacity value remains
close to ~100% by shifting
energy production to evening
(and morning during
spring/winter months)
•Capacity value adder depends on market conditions - typical
values of $40-$70/kW/year
•Depending on CSP system design and market conditions,
adds a CSP value of 0.7-2.0 cents/kWh
National Renewable Energy Laboratory
6
Innovation for Our Energy Future
3) PV Curtailment Due to Ramping Requirements
60000
Normal Load
1% PV
50000
5%
10%
Net Load
40000
15%
20%
30000
20000
Ramp rate of
conventional generator
requirements increases
10000
0
0
Ramp
12 range of24
conventional generator
requirements increases
36
48
60
72
Hour
Curtailment results from two main constraints – ramping requirements and
minimum generation constraints. Curtailment results when existing plants to not
have the flexibility to ramp
National Renewable Energy Laboratory
7
Innovation for Our Energy Future
Curtailment Due to Minimum Generation Constraints
90000
• Marginal curtailment rate of PV moving from
10% to 15% of generation was 5%
PV
CSP5
Wind15
15% PV
No
CSPPV10
CSP
80000
Wind
Hydro
70000
PHS/CAES
Gas
60000
• At SunShot goals (~6 cents/kWh) this
increases effective PV cost by about 0.3
cents/kWh due to underused capacity
Generation (MW)
Other
Biomass
50000
Coal
Nuclear
40000
Geothermal
30000
20000
10000
10%CSP5
PVWind15
5 % CSP
PV10
90000
PV
0
CSP
80000
1
5
9 13 17 21 1
5
9 13 17 21 1
5
9 13 17 21 1
5
9 13 17 21
Wind
Hydro
70000
PHS/CAES
Gas
Generation (MW)
60000
Extensive coal and nuclear cycling unlikely
to occur in current system
Other
Biomass
50000
Coal
Nuclear
40000
Geothermal
30000
20000
• PV curtailment would be reduced if grid
flexibility were increased
• CSP/TES provides an option to replace
“baseload” capacity with more flexible
generation
10000
0
1
5
9 13 17 21 1
5
9 13 17 21 1
National Renewable Energy Laboratory
5
9 13 17 21 1
5
9 13 17 21
8
Innovation for Our Energy Future
PV Curtailment at Higher Penetration
Marginal PV Curtailment
60%
Estimates marginal
curtailment as a function of
PV penetration (without
additional grid flexibility)
50%
40%
30%
20%
10%
0%
0%
5%
10%
15%
20%
25%
30%
35%
Fraction of System Energy from PV
Without storage or load
shifting, marginal LCOE of
PV increases rapidly
“Multiplier” to
base LCOE
Relative Marginal LCOE
2.4
14
2.2
13
2.0
12
1.8
11
10
1.6
9
1.4
8
1.2
7
1.0
6
35%
0%
5%
10%
15%
20%
25%
30%
Sunshot Marginal LCOE
(cents/kWh)
15
Fraction of System Energy from PV
National Renewable Energy Laboratory
9
Innovation for Our Energy Future
4) Integration and Reserve Requirements
• Variability and uncertainty of solar resource requires
changes in operation, typically some re-dispatch of
system resources to maintain reliability
Very large ramping of
conventional generators is
required. This potentially means
more use of fast responding but
lower efficiency generators
12000
Normal Load
10% PV
8000
15%
Ramp Rate (MW/Hour)
20%
4000
0
0
12
24
-4000
-8000
-12000
Hour
National Renewable Energy Laboratory
10
Innovation for Our Energy Future
Reserve Requirements
•
We have not yet analyzed the increased need for frequency
regulation or forecast uncertainty for either PV or CSP
– One previous PV study estimated costs of re-dispatch at 0.4-0.7
cents/kWh, but used limited data sets and is not reproducible
– Estimates from wind integration studies are in the range of 0.2-0.4
cents/kWh
•
Storage enables operation at part load and ability to hold back
energy during periods of high uncertainty or large reserve
requirements
National Renewable Energy Laboratory
11
Innovation for Our Energy Future
Summary: Impacts of Storage at 10-15% Solar
With gas prices in the range of $4.50-$9.00 mmBTU, the
estimated value of CSP with storage is an additional 1.6-4.0
cents/kWh relative to PV due to:
• Energy shifting value: ~0.5-1.0 cents/kWh
• Capacity Value ~0.7-2.0 cents/kWh
• Reduced curtailment: Depends on PV cost. At 6
cents/kWh, corresponds to ~0.3 cents/kWh
• Reserve/integration costs 0.1-0.7 cents/kWh
National Renewable Energy Laboratory
12
Innovation for Our Energy Future
CSP as a PV Enabling Technology
• The ability of a the grid to accommodate PV is inherently limited
by the increased variability and uncertainty of net load
• As PV penetration increases other generators will need:
•
•
•
•
Short start-up times
Large ramp rates
Large turn-down ratios
Good part load efficiency
CSP with storage can
provide these requirements
Historical performance of U.S. small gas
steam plants which are a good proxy for
CSP – typical operating range of 78% with
only a 7% heat rate penalty at 50% load.
National Renewable Energy Laboratory
13
Innovation for Our Energy Future
CSP as a PV (and Wind) Enabling Technology
45
Additional PV will
largely be curtailed
due to minimum
generation
constraints
Dispatch in a “conventional” system
40
Curtailed PV
35
Dispatched CSP
30
Load (GW)
Relying on thermal
generators and
ignoring flexibility
benefits of CSP limits
amount of demand
that can be met with
variable generation
Usable PV
Wind
25
Conventionals
20
Load
Non-Dispatched CSP
15
Dispatched CSP
10
5
0
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
Hour
CSP energy is shifted to morning and
evening, increasing the contribution of
solar technologies, but not providing a
direct benefit to PV or wind.
Total RE contribution is 35% on an energy basis (solar
provides 23%). About 5% is curtailed.
National Renewable Energy Laboratory
14
Innovation for Our Energy Future
CSP as a PV (and Wind) Enabling Technology
Dispatch in a “CSP-flexible” system
45
40
Curtailed PV
35
Dispatched CSP
30
Load (GW)
Adding the flexibility
of CSP enables a
greater fraction of the
load to be served by
variable generation
Usable PV
Wind
25
Conventionals
20
Load
Non-Dispatched CSP
15
Dispatched CSP
10
Minimum generation
constraint reduced
5
0
1 6 11 16 21 26 31 36 41 46 51 56 61 66 71 76 81 86 91 96
Hour
CSP energy is still shifted, but also used
to provide quick-start reserve capacity
during periods of high PV output.
CSP provides additional ramping
capacity in the evening and morning.
Total RE contribution is increased to 46% (solar contribution
at 29%) with no increase in curtailment.
National Renewable Energy Laboratory
15
Innovation for Our Energy Future
Summary
•
•
As penetration of variable generation (solar, wind)
increase, it is increasingly important to consider the
interaction between these resources and the entire grid
system
Dispatchable energy (e.g. CSP w/storage) has a higher
value than non-dispatchable energy.
–
–
•
At low penetration of solar and wind this difference is small
At higher penetration (15% on an energy basis) this difference
may increase by as much as 4 cents/kWh
Overall penetration of solar energy can be increased by
the use of CSP with storage which provides grid
flexibility
–
Allows for higher levels of PV penetration by providing the
ramping rate and range needed to accommodate the variable
output of PV systems
National Renewable Energy Laboratory
16
Innovation for Our Energy Future
Questions?
References (Note that several of the results in this presentation have not yet been published).
Madaeni, S., R. Sioshansi, and P. Denholm, "How Thermal Energy Storage Enhances the Economic Viability
of Concentrating Solar Power" accepted in Proceedings of the IEEE.
Madaeni, S. H., Sioshansi, R., Denholm, P. (2011) “Capacity Value of Concentrating Solar Power Plants”
NREL Report No. TP-6A20-51253.
Brinkman, G.L., P. Denholm, E. Drury, R. Margolis, and M. Mowers. (2011) “Toward a Solar-Powered Grid Operational Impacts of Solar Electricity Generation” IEEE Power and Energy 9, 24-32.
Denholm, P., and M. Hand. (2011) “Grid Flexibility and Storage Required to Achieve Very High Penetration of
Variable Renewable Electricity” Energy Policy 39 1817-1830.
Sioshansi, R. and P. Denholm. (2010) “The Value of Concentrating Solar Power and Thermal Energy
Storage.” IEEE Transactions on Sustainable Energy. 1 (3) 173-183.
Denholm, P., E. Ela, B. Kirby, and M. Milligan. (2010) “The Role of Energy Storage with Renewable Electricity
Generation” NREL/TP-6A2-47187.
Denholm, P., R. M. Margolis and J. Milford. (2009) “Quantifying Avoided Fuel Use and Emissions from
Photovoltaic Generation in the Western United States” Environmental Science and Technology. 43, 226-232.
Denholm, P., and R. M. Margolis. (2007) “Evaluating the Limits of Solar Photovoltaics (PV) in Electric Power
Systems Utilizing Energy Storage and Other Enabling Technologies” Energy Policy. 35, 4424-4433.
Denholm, P., and R. M. Margolis. (2007) “Evaluating the Limits of Solar Photovoltaics (PV) in Traditional
Electric Power Systems” Energy Policy. 35, 2852-2861.
National Renewable Energy Laboratory
17
Innovation for Our Energy Future