RE(x,y)=?
Power system adequacy with intermittent
renewable energy
Energy Transformed Flagship
Geoff James
AIE National Conference
Sydney, 19 November 2012
Important influences in the Asian region
• Universal access to clean energy
• There are 800 million Asians relying on basic fuels (Asian Development
Bank)
• The best overall solution is likely to be a mixture of interconnected grids and
separate regional grids – or interconnected and local energy supplies in an
Australian context
• Interconnection and trading
• Increased quality and diversity of renewable resources that may be
accessed and traded – each region can use its best resources
• Long-distance interconnection by HVDC transmission creates a new
dispatchable resource for grid management
• The emergence of energy storage
• Storage will modify demand, smooth supply, and create a new dispatchable
resource for operators of clean grids
Geoff James, Power system adequcy with RE, 19/11/2012
Question about system adequacy
• Presuming that power grids will trend towards majority renewable
energy supply and that much of this will be intermittent
• Allowing that the purpose of power grids of any size is to balance
supply and demand continuously
• Given (historical) knowledge of the renewable energy resource over an
interconnected region
• How much installed generation capacity will be needed (and
where) to ensure system adequacy?
• Minimising the overall installed capacity
• Maximising the proportion of renewable energy supply
• With or without consideration of transmission capacity
Geoff James, Power system adequcy with RE, 19/11/2012
Reliability = security + adequacy
• Security of the power system
• Physical, information technology, and communication threats
• Thermal, transient, voltage, oscillatory instabilities
• Adequacy of generation, transmission, substation, and distribution
infrastructure to meet the electrical load at all times
• Without violating system voltage and frequency limits
• In the presence of planned and unplanned outages (e.g. N-1 contingencies)
• Separate measures for installed adequacy and operating adequacy
• Typical requirement for interconnected power systems
• Loss-of-load expectation (LOLE) is less than 0.1 days per year
• Expected energy not served (EENS) is less than 0.002% of total
consumption
Geoff James, Power system adequcy with RE, 19/11/2012
Renewable & fossil-fuel generation capacities
Type
Capacity
Variation
Intermittent RE
R(x,y)
r(t) ≤ R(x,y)
Fossil fuel
G
g(t) ≤ G
Load
L
l(t) ≤ L
r (t )   R( x, y) ( x, y, t ) dx dy
A
Generating “efficiency” of the installed
RE capacity according to the weather
Geoff James, Power system adequcy with RE, 19/11/2012
Begin with generation-only risk assessment
Ignore transmission
R(x,y)
G
L
With transmission
R(x,y)
G(x,y)
L(x,y)
• A fast optimisation method can compute R(x,y) and G
• Tested with wind and solar and extensible to represent a diverse mix
of sources
• Hydro generation h(t) ≤ H
• Biomass generation b(t) ≤ B and potentially separate treatment of biogas
generation
• Geothermal generation u(t) ≤ U
Geoff James, Power system adequcy with RE, 19/11/2012
Wind deployment with unconstrained G
Outcome:
maximum
capacity
factor!
• Optimise using 30-min intervals over 1 year (17,600 constraints)
• Resolution 1 degree in latitude and longitude (1,500 unknowns)
Geoff James, Power system adequcy with RE, 19/11/2012
Solar deployment with unconstrained G
Outcome:
maximum
correlation
with load!
• Now introducing ramp-rate limits for fossil-fuel generation plants
• Also constraining the emissions (= maximising RE penetration)
Geoff James, Power system adequcy with RE, 19/11/2012
Traditional way to model generation availability
Wenyuan Li. (2005). Risk Assessment of Power Systems. IEEE on-line.
• Artificial time series for generation availability using MTTF and
MTTR
Geoff James, Power system adequcy with RE, 19/11/2012
Combine with artificial load to calculate LOLE
Wenyuan Li (2005). Risk Assessment of Power Systems. IEEE on-line.
• But for an accurate result the simulated period can be many years!
Geoff James, Power system adequcy with RE, 19/11/2012
New way to model generation and load
Keane et al. (2011). IEEE Trans. Power Systems 26 (2), 564-572.
• Recommends a Preferred Methodology for calculating system
adequacy with wind generation
• Each generator capacity and FOR is convolved via an iterative method to
produce the capacity outage probability table (COPT) of the power system
• The COPT of the power system is used in conjunction with the hourly load
time series to compute the hourly LOLPs without the presence of the wind
plant
• The annual LOLE is then calculated
• This approach uses coincident time-series data for load and
renewable generation output – and these are significantly
correlated
• The fast optimisation method can include LOLE and EENS calculated
this way as optimisation targets
Geoff James, Power system adequcy with RE, 19/11/2012
Energy storage to balance supply and demand
• Energy storage options and costs have been compared in the context
of high-penetration RE future for the National Electricity Market
• James and Hayward (2012). AEMO 100% Renewable Energy Study:
Energy Storage. CSIRO, Australia. Available on the DCCEE website.
• Several technologies available at grid scale were studied
•
•
•
•
Solar thermal storage using molten salts
Storage of biomass solids – and production and storage of biogas
Compressed air energy storage (CAES)
Three different battery technologies
• Pumped hydro storage was analysed in detail by another consultant
• ROAM Consulting (2012). Pumped Storage modelling for AEMO 100%
Renewables project. ROAM, Australia. Also available on the DCCEE
website.
Geoff James, Power system adequcy with RE, 19/11/2012
Storage costs as $/MWh of delivered energy
which depend on a number of assumptions about operating regimes
Woody biomass solids
Crop biomass solids
$1,000
Repurposed lithium-ion
Advanced lead-acid
Above-ground CAES
Underground CAES
$100
Zinc-bromine
Pumped hydro
Biogas from MSW
CST with molten salt
1 hour
Geoff James, Power system adequcy with RE, 19/11/2012
Biogas from woody/crop sources
1 day
30 days
Deciding what to do with biomass
Available
biomass
solids
fb
Use for “baseload” generation
fs
Direct to solid biomass storage
fg
Direct to biogas storage
1  fb  f s  f g
Geoff James, Power system adequcy with RE, 19/11/2012
Not used
Flow rates in biomass electricity generation
Rgenerate
Rharvest
Rtransport
Geoff James, Power system adequcy with RE, 19/11/2012
Availability of woody biomass in 2030
Exclusions
used to help
identify the
resource that
can be
responsibly
and
sustainably
harvested
Geoff James, Power system adequcy with RE, 19/11/2012
Availability of crop & stubble biomass in 2030
Complements
quite well the
availability of
woody
biomass
Geoff James, Power system adequcy with RE, 19/11/2012
The East Australian biogas storage network
Storage capacity on the gas pipeline network
Gas
Electricity
measure measure
150 PJ
14.6 TWh
Processing and transmission capacity of the network
4 PJ/day
Parameter
Geoff James, Power system adequcy with RE, 19/11/2012
16.2 GW
CSIRO Energy Technology
Geoff James
Principal Research Scientist
Phone: +61 401 681 282
Email: geoff.james@csiro.au
Web: www.det.csiro.au
Thank you
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