IEEE Power & Energy Magazine - November/December 2021 - 60

Interstate
Transmission
Included
System Cost of
Electricity (US$/MWh)
04080 120
None
+ Existing Regional
+ New Regional
+ Existing Interregional
+ New Interregional
Within Interconnects
+ New Interregional
Across Interconnects
Transmission
PVs
Hydropower
(a)
2,500
2,000
1,500
1,000
500
BAU
HVdc
Macro Grid
Generation Fixed Generation Variable
Transmission
Emissions
(b)
500
400
300
200
100
2020
2035
2050
Generation Fixed Generation Variable
Transmission
Hydrogen
Distribution
(c)
figure 3. (a) The MIT study's system electricity costs broken
down by transmission, storage, PV, wind, and hydropower
resources for each of the scenarios; (b) the Interconnections
Seam Study's 35-year net present value of system
costs for 50% renewables case; and (c) ZeroByFifty's annualized
system cost components for 100% clean energy in
2018 U.S. dollars for the years 2020, 2035, and 2050. The
fixed costs include capital investments and variable costs
comprise fuel and operations and maintenance costs. BAU:
business as usual.
60
ieee power & energy magazine
A Macrogrid Saves Money
A macrogrid is a large-scale, interregional network of transmission
that can include HVac and dc components. HVdc has
many benefits, including lower cost for long-distance, highcapacity
transfer capability and more efficient use of right of
way. It also can benefit stability in weak grids using voltage
source converters (as discussed below). In addition, HVdc connects
asynchronous ac systems such as the EI, WI, and ERCOT.
Multiterminal HVdc can be used to provide off-ramps along
long distances, albeit at a higher cost. Dc terminals can connect
into HVac collector systems at source and sink regions.
november/december 2021
Optimizing Capacity and Transmission
Expansion Over Larger Regions
Saves Money
The MIT study found that conducting electric system coordination
and expansion over increasingly larger geographic
areas reduces system cost, generation capacity, and storage
capacity needed for an equivalent level of reliability. It found
that the system cost of electricity (including annualized capital,
operating cost of generation, transmission, and storage,
but excluding distribution and administration costs) in the
nationally optimized zero-carbon system to be US$62/MWh
(46%) lower than the average system cost in the every-statefor-itself
alternative [shown previously in Figure 3(a)].
Storage
Wind
plant individually. The proactive planned approach can significantly
reduce the amount of onshore HVac upgrades at the
landing sites, including in the Cape Cod region, saving money
and reducing project risk. This approach would also foster
competition among offshore developers, reduce wind energy
curtailment, and save US$1 billion in onshore transmission
upgrades. For New York, Brattle similarly found savings of at
least US$500 million for a planned offshore grid approach.
The Electric Reliability Council of Texas (ERCOT) offers a
good example of proactive transmission planning. Competitive
renewable energy zones (CREZ) were designated in areas with
high-quality wind resources, and new transmission was planned
and built to deliver that new generation to loads. This process
did not merely identify resource zones, but legislatively deemed
these transmission lines " used and useful " to assure cost recovery
of the CREZ transmission projects. Transmission could then
be properly sized to the zones rather than developed and justified
incrementally as the generation projects were approved,
saving money through the " right-sizing " of projects.
It also allowed better coordination between the longer timeline
of transmission construction and the fast construction
times of wind and solar plants. The statute imposed short-time
requirements upon planners and regulators to design and process
the CREZ plans, select competitive transmission providers,
and approve line routes. Texas' practice of assigning transmission
expansion costs directly to customers, rather than requiring
new generators to pay for transmission upgrades (as the latter
yields incremental rather than large-scale transmission expansion),
also contributed to the success of CREZ.
Annualized
35-Year Net
Costs (US$ Billions)
Present Value (US$ Billions)
IEEE Power & Energy Magazine - November/December 2021

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