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How Much Solar Can We Use, How Fast, and at What
Cost?
Ken ZweibelThe George Washington University
Institute for Analysis of Solar EnergyNational Academies of Science, Engineering, and Medicine
July 29, 2008
Some Background• There’s more solar energy than we’re ever likely to need for
all our energy demands combined• Making intermittent solar during the day is easy and
relatively cheap – In the best solar locations, about 15 ¢/kWh for CdTe PV
(First Solar) and claimed for CSP• We also must take into account solar’s daily and
seasonal variations• Other important details include
– PV output varies proportionally with local sunlight, which within the US varies by about a factor of almost two
– CSP is uneconomical in cloudier regions due to its dependence on direct sun
– HV DC transmission has losses and costs
General Comments
• The following is a toolbox of approaches that harnesses solar in the US at the multi-TW level and aims at minimizing total cost in terms of solar variation by– Blending solar to reduce as many natural variations as
possible– Using existing fossil fuels and nuclear as a back-up (while
reducing fuel use by a large fraction), but never building a new conventional plant
– Using solar mostly in the daytime and electric storage (compressed air) only when we must
• Timeliness:– Uses today’s best solar prices, and prices achievable with
a high degree of confidence during the next 10 years– Aims at harnessing today’s solar ASAP, not waiting
The Opportunity
1 day1 day of unconverted US solar energy: 48,000 TWh
1 year of US electricity: 4000 TWh
Imported oil is ¾of this, if electric
Approach
• Conversion of vehicles to plug-in hybrids• Solar and wind mostly converted in their best resource locations
(Southwest & Midwest), but spread out within those regions to de-couple weather
• Low-loss transmission lines (HV DC) from location of large fields todemand
• Wind and solar combined along transmission lines to make smoothly varying, 24/7 output
• Short-term solar thermal heat storage used to its economic limit• Compresses air energy storage (CAES) use only for evening peaks (no
overnight or seasonal storage)• To minimize impact of transmission losses, build large solar farms
wherever there is decent sunlight closer to demand– Large arrays in sunny Idaho, Florida, Eastern Colorado, Texas,
Utah, rest of CA, Northern Mexico, Eastern Oregon, etc.– Consider a “beltway” HV DC linking these to reduce weather,
climate, and seasonal impacts
Wind
Midwest
Solar Southwest
National Electricity Transmission System to Export Solar Electricity from Southwest and Wind Electricity from the Midwest.
15 ¢/kWh solar electric from the Southwest canbe sent nationwide with about 11% losses. We can get solar electricity in Maine for about20 ¢/kWh
How to get the solar and wind electricity (the first order approach)
Courtesy SunEdison
Courtesy UniSolar
PV Geographic Smoothing:This is what we want as output nationwide
“Capacity Valuation Methods,” SEPA 02-08, Hoff, Perez, Ross, Taylor, 2008
Blending Wind & Solar
Transmission corridors will pick up complementary wind along the way to demand
• Wind blows at night and winter (opposite of solar)– Of 6000 MW
ERCOT (Texas) wind, only 10% available at daytime peak
• 24/7 waves of wind/solar power
Wind and Sun Are Complimentary
High Plains Express Feasibility Study, June 2008, p. 35
Increased Capacity Use with Wind and Solar Lowers Transmission Cost
“We found that by blending wind and solar for geographically diverse sites, we can achieve a more consistent product for delivery, thereby offering the potential for reducing integration costs and improving the economics and acceptability of renewables.” Jerry Vainineti (co-author)
From High Plains Express Feasibility Study, HV AC, for wind and solar combination
JUWI Group is installing 40 MW of First Solar modules in Waldpolenz, Germany. At the time of the announcement, it was both the largest and lowest-priced PV system in the world at €3.25/W, which was then equal to $4.2/W. A program for 250-MW of rooftop systems by Southern CA Edison has been signed for $3.5/W.
First Solar has a contract to install a thin film CdTe PVSystem in Blythe, CA and sell its electricity at 12 ¢/kWh (after incentives)
http://www.juwi.de/international/information/press/PR_Solar_Power_Plant_Brandis_2007_02_eng.pdf
LUZ I 15 years agoNevada 1 Today
Solar Thermal: BrightSource/LUZ II has a contract to install a 400 Megawatts (expandable to nearly 1 GW) for Southern California Edison
Claimed to be in the same 15 ¢/kWh range as the best PV (prior to incentives)
Daytime Solar Costs (¢/kWh)
0.5 (falls proportionally to cost of solar)
1
Estimated Cost to
Make Fully Usable
(daytime only)
11 - 123.8 (solar) or 2.6 (solar + wind)
82015
19 - 214.5 (solar) or 3.2 (solar + wind)
152008
Total at
2000 miles
(East
Coast)
Transmission
Cost (¢/kWh
per 2000
miles)
Intermittent
Cost in Best
Locations
Timeframe
2.5792037453.810048total added costs
1.7958222223.026667Capital cost
3 stations per 1000 miles
0.7833815220.783382losses cost
9%9%% losses total
88feedstock elec
1.0284444441.733333Capital cost of DC-AC eqpt
3 stations per 1000 miles
1%1%loss at DC-AC
0.7673777781.293333
capital cost of transmission wire alone
6%6%losses per 1500 miles
20002000distance
45.0%26.7%capacity factor
High CFLow CF
How Fast Can Solar Be Scaled Up?
• Recent solar PV growth rate has been around 50% per year, to about 5 GW
– There have been some undesirable bottlenecks and price increases
– Having an agreed-upon timeline for expansion could avoid future bottlenecks
• Solar thermal appears to be built with basic materials and components, suggesting rapid growth would be possible
Possible Growth of PV from 5 GW (world, 2008)
Assumes 50%/yr Growth, 1/3 in US
0
500
1000
1500
2000
2500
3000
3500
4000
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
US
PV
In
sta
lle
d
GW World Annual PV
GW US Annual Installed PV
GW Cumulative US InstalledPVTWh/yr in US SW
US electricity today
What about CSP and Wind?
• CSP – assume similar level – 3700 TWh by 2023
• Add in 1000 TWh of wind (DOE & various estimates)
• Deploy up to 8400 TWh/yr non-CO2 renewables by about 2023
– Not quite as fast as Gore’s Plan
• Perspective: US electricity 4000 TWh; imported oil if displaced by electricity, 3000 TWh
Using Daytime Solar Well
• Now – can add solar and move daytime fossil fuels to meet solar/wind evening shortfalls and nighttime plug-in charging*
• Wind meets a large part of nighttime charging
• Later – solar overwhelms traditional midday electricity demand post-2020; must be used for midday plug-in charging, with some solar and nuclear moved to nighttime by CAES
*Better than Pickens Plan of using natural gas for cars, since this displaces the natural gas with solar
Economic Perspective
• Cost of smoothly varying daytime solar, nationwide (lower in proximity to US SW)* :
– Up to ~20 ¢/kWh now (less in CA, Midwest, etc.)
– Up to ~12 ¢/kWh 2015 (less in CA, Midwest, etc.)
• First Solar has $2/W (8 ¢/kWh) installed systems as their stated goal in the next few years; and wafer silicon says that once silicon prices subside, something similar is possible
• Cheaper transportation, more costly electricity at first, permanent solution that is much less expensive than business as usual
– Saves society money with switch to electric plug-in hybrids
– Removes the terrifying threat of continually escalating fossil fuel prices and obligations
– Grows jobs and dollars domestically
• First decade versus coal needs ITC as CO2 offset
*Does not include additional charge by local utility for AC distribution
Footnote to Economics
• Nothing in economics takes into account the long life of PV
• Once paid off in 20-30 years, PV has another 30 plus years of life
• No one will plow under a PV system that is at 85% of full output in 30 years and costs practically nothing to maintain– Meanwhile, who knows where fossil fuel prices will be?
• This is not captured anywhere in above, because the above is “levelized cost of energy” over life of the loan– This will be a great gift to future generations, as the Hoover dam
and TVA was to ours
Impact
• Eliminate almost the equivalent of all of our current energy use (100 Quads) in 15 years– Up to 8400 TWh/yr (2000 of PV, 2000 of CSP,
1000 of wind)• ~10,000 TWh used electrically can displace
about 100 Quads primary energy • Reduce CO2 by almost 5 gigatons (almost all
today’s energy emissions) versus 2023 “business as usual” level
– Actually reverse carbon dioxide buildup• Achieve energy self-sufficiency and strong economy
Action Items
• Build solar and wind as fast as humanly possible, mostly in large fields in high resource locations
• Build HV DC to send to demand, include source and geographic diversity on each HV DC line to smooth output
• Shift vehicle fleet to plug-ins, use mostly wind and shifted natural gas and coal at night to charge
• Replace natural gas and coal during day with solar• Use existing conventional capacity to fill in daytime gaps and
meet any missed evening peaks• Require large proportion of midday charging as solar output
outstrips daytime demand post 2020• Add CAES to meet evening peaks, starting with storing
daytime nuclear electricity
Imagined Scene
• NY Mayor: “Should we build our electricity aqueduct to Kansas and use their wind and solar, or extend it all the way to Nevada?”
• Official: “Well, the sunlight in Nevada is 25% better, and the time zone difference means we can meet our evening peak without storage. But Florida is offering us a deal.”
• Mayor: “What does New Jersey want, or do we go through Pennsylvania?”
• Etc.
Thanks to James Mason (ASAP.org), Vasilis Fthenakis
(BNL & Columbia), Tom Hansen (Tucson Electric), Bill Bailey, and
many others
202-994-8433Institute for Analysis of Solar EnergyThe George Washington University
