This document discusses the potential for building a solar society by using solar power to provide electricity for electric vehicles. It argues that transitioning to electric transportation powered by solar and wind energy could solve major problems like carbon dioxide emissions, oil supply issues, and economic vulnerabilities related to energy imports. The document estimates that converting 70% of vehicle fuel needs to electricity would require around 1000 terawatt-hours per year of new solar capacity, which could be achieved through 625 gigawatts of solar panels using just 0.2% of US land area. It acknowledges challenges like costs, intermittency, and transmission but argues these issues can be addressed to make large-scale solar electricity feasible and cost-competitive within a 12 year timeframe.

1. Building a Solar Society
Ken Zweibel
Director
GWU Institute for Analysis of Solar
Energy

2. What are our problems?
Carbon dioxide
•
Oil supply
•
Energy prices
•
World conflicts over energy
•
Trade imbalance
•
Economic vitality
•
Can we use solar to solve these problems?
•

3. Electric Transportation
• Plug‐in hybrids
Daytrips – electricity
–
Range – fuel
–
Charging
–
Efficient electric motors (90%, instead of 30% internal
–
combustion engines)
– 10 c/kWh electricity is close to $1.5/gallon gasoline
equivalence
– This is not “business as usual”
– THIS IS A HUGE OPPORTUNITY FOR CHANGING OUR
ENERGY WORLD!

4. Transforming Our Energy
• If we move to electric transportation we can
– Get off foreign oil
– End dependence on others
– Remove the irritation causing global tensions
– Stabilize energy prices
– Stimulate our economy instead of bled dry by
imports
– And lower our transportation costs at the same
time!

5. How can we do this?
• Make MUCH more electricity with
– Coal
– Nuclear
– Wind
– Natural gas
– Solar
• Or maybe not…

6. Electricity Options
Coal makes too much carbon dioxide
•
Natural gas is too supply limited
•
Nuclear…is nuclear
•
So that leaves wind and solar
•
– Wind is fine, but too small
• Potential for 20%‐30% of current
electricity
– So, solar…

7. There’s Plenty of Solar
1 day of unconverted US solar
energy: 48,000 TWh
1 year of US
electricity: 4000 TWh

8. Let’s Remind Ourselves that Solar
Already Exists

12. How does solar solve our problems?
• We use solar and some wind to produce almost
every new kWh we need to meet transportation
demand
– Energy self‐sufficiency AND
– Elimination of the carbon dioxide in gasoline
• Won’t people charge at night?
– Yes, initially, and for that we use wind and fossil fuels
– But we displace those same fossil fuels during the day with
solar
– And when we produce enough solar, we shift to daytime
charging

13. To Repeat…
• We can use solar and a wind to charge our
plug‐in hybrids
• We may not need any more fossil fuels to do it
• We may not need any more nuclear to do it
• We can do it without carbon dioxide
emissions, eliminating almost all carbon
dioxide from the transport sector
• And we can save money doing it

14. Aren’t there some devilish details?
Cost of solar
•
Land for solar
•
Intermittency
•
Demand & supply mismatch
•
Transmission
•
Speed of adoption
•

15. Problems and Solutions
• Let’s look at each of these
• First, how much energy are we talking about?

17. How Much Electricity?
• 5.3 Quads used to move vehicles
• Losses
• 15% electric to battery
• 10% motor
• 10% electric transmission from source
• 5.3 Quads needs 7.7 Quads before losses
• Let’s replace 70% (somewhat arbitrary), so we
need 5.4 Quads of electricity
• 1600 TWh (1 Q is about 300 TWh)

18. How Much Solar?
• Let’s add ~10% for demand growth during
replacement
• We need 1800 TWh/yr of new non‐carbon
production
• If 800 TWh of this is wind (equivalent to 20%
of today’s electricity, a common goal)…
• Then we need 1000 TWh of solar
• At 1.6 kWh/W installed, this is 625 GW of new
solar capacity

19. How Much Land Is 625 GW Solar?
• Ignore rooftops to first order
• About 16,000 km2 (126 km on a side)
– Assuming 40 W/m2 of land use
• Less than 0.2% of US land area (9 million km2)
• Is this a lot?

21. Hydro and Solar Land Use
Hydro Solar
• 1% US land • 0.2% US land
• 7% electricity • 1000 TWh (25% US
electricity)
• 280 TWh
• 16 times more land
efficient than hydro!!!!

22. Can We Do This Quickly?
• Current world PV production is about 5 GW/yr
• At a growth rate of 50% per year, and
assuming 1/3 goes to the US, we accumulate
625 GW of installed PV in the US in 2020 (12
years)
– We use PV as a proxy for all solar in this
calculation (adding solar thermal electric would
make this easier)
– Pinch points require further examination

23. But how much would it cost?
• Many ways to calculate cost
• Key is, in comparison to what?
• The most direct answer:
– In comparison to buying gasoline over $2.5/gallon,
it is cheaper
– In comparison to buying gasoline that is
continuously escalating, it is transformationally
cheaper
– In comparison with today’s coal, it is more
expensive, but avoids carbon dioxide

24. This Assumes
• Solar electricity is
– 15‐20 c/kWh in the US Southwest and CA
– 20‐25 c/kWh elsewhere due to less sunny conditions
or long‐distance transmission costs
• Used in plug‐in hybrids, 20 c/kWh solar is equivalent to
about $2.5/gallon gasoline
• Technical roadmaps exist for solar at 10 c/kWh or less in
the Southwest
– But commodity inflation may overtake those cost reductions

25. Comparison of Plug‐In Hybrid Options*
CO2 Emissions of Plug‐in
Hybrids (g/mi)
600
500
400
300
200
100
0
Gasoline Solar US
Electric Electric
Hybrid Mix
Hybrid
*Not including battery costs and battery CO2 footprint.

26. Solar versus Coal
• Today’s coal‐based electricity is about half the price
of solar (for new installations)
• The following assumptions make using coal or solar
the same within 1% for a 12‐year program:
– Today’s solar is twice the cost of coal
– Coal increases by 3% per year and solar decreases by 3%
per year (cost weighted by increasing annual installations)
• Over the course of a 12‐year program, solar and coal
could be the same cost

27. What Issues Are Left?
• Intermittency
• Supply & Demand Mismatch
• Transmission

28. Transmission
• Transmission is valuable because solar intensity in some
regions is 50% higher than most places
– Implies 33% lower price
• For long distances
– High‐voltage lines lose less per mile (I2R loss)
– DC loses less than AC (wavelength‐driven loss)
• A High‐Voltage (HV) DC line
Loses 3% per 1000 km
–
Line costs 0.25 c/1000 km at solar capacity factor
–
1% loss and 1.7 c/kWh capital cost at downlink
–
10% loss at 3000 km implies another 1.2 c/kWh (at 12 c/kWh)
–
Total implied cost is about 4 c/kWh at 3000 km
–
• So total cost is 15 c/kWh + 4 c/kWh = ~20 c/kWh for transmitted solar
– Requires right‐of‐way access

29. Siemens has built several GW of high‐voltage DC transmission lines worldwide. This is a 235‐
MVA‐HVDC power transformer for the Australia‐Tasmania undersea cable. An even larger line is
being built in China (2400 km with a power transmission capacity of 6.4 GW)

30. Transmission Opportunities

31. The Sun Is Always Shining: Siemens HV
DC Vision
12,000 mile transmission, about equivalent to storage losses (0.9720>0.5)
Can balance night/day (east-west) and seasons (north-south)
Siemens 2007, EPRI, DC_Solutions_EPRI_Conference_09-07_V_1b, slide 47

32. Supra‐Regional
• International transmission
– Could be cheaper than storage (capital plus losses)
– Removes sudden peaks and valleys due to geographic
distribution (avoids correlated cloud events)
– East – West
• Extends daylight hours
• Eventually could be “24 hour”
– North – South
• Ameliorates seasonal solar variations (always about the
same output)

33. Example of Geographic Smoothing
“Capacity Valuation Methods,” SEPA 02-08, Hoff, Perez, Ross, Taylor, 2008

34. Transmission corridors will pick up
wind along the way to East Coast
Add distributed
solar along the
way as well

35. Wind and Sun Are Complimentary
High Plains Express Feasibility Study, June 2008, p. 35

36. 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

37. What Does Transmission Do?
• Access to better (cheaper) resource
• Can combine with wind
• Geographic diversity smoothes output,
reducing size of abrupt changes (a key
variability issue)
• Reduces day‐night and seasonal variations if
very long distances
• Partial replacement for storage

38. What’s Left?
• Further solutions for solar variability
– We may not have long‐distance transmission in a
timely manner due to access issues
– Machines and consumers do not run on varying
electricity
• Mismatch between solar and demand

39. Solar Variability
Night
•
Seasons
•
Storms
•
Cloudiness
•
Transient clouds
•
– Gap and peak ramp rates

40. Variability Solutions
Fast, short‐term gaps
•
• Transmission
• Geographic diversity of sources
• Draw down from plug‐in hybrid batteries
• More flexible fossil fuel generators
• Moderately fast gaps
• Normal fossil fuel backup
• Growth in evening peaks
• Storage (e.g., compressed air, CAES)
• East‐west transmission
• New fossil fuel generators
• Nighttime demand for charging plug‐ins
• Wind
• Fossil fuel moved from daytime (and replaced with solar)

41. Demand Mismatch
• Solar shape (midday maximum; seasonally
varied)
• Demand variability (regional, season)
• Spring and Fall midday solar oversupply
• Charge plug‐in hybrids
• Charge compressed air
• Winter demand
– Fossil fuel back‐up
– CAES and North‐South transmission

42. How Can We Do This?
• More flexible fossil fuel generation, even if it requires
replacing existing generators with specialized ones
– Because solar requires flexible “load following” to
compensate for its variations
• Almost no new conventional energy generation
– Everything from wind and solar, some new storage
– Possibly some natural gas growth for evening peak growth
• Smarter grid that allows more responsive movement
of supplies to demand, and movement of oversupply
to storage or elsewhere

44. Principles
• Avoid storage except plug in hybrids as much as possible
– Doubles cost of electricity
• Do not store fossil fuels – increase carbon dioxide emissions
by turnaround losses
• Store lowest cost non‐carbon dioxide electricity
– Wind, existing nuclear, then solar
• Store excess solar in plug‐in hybrids Fall and Spring midday
• Explore long‐distance transmission to offset storage

45. Denoument
• Instead of thinking of shutting down existing
coal plants with solar, we should be thinking
of eliminating foreign oil and using our
existing fossil fuel plants to backup solar
energy
• This will avoid the issue of abandoned assets
(which still have to paid for), while addressing
our key problems – oil prices and carbon
dioxide emissions

46. Total Value
• Energy self‐sufficiency
• Avoided CO2
• Price stability (and no fear of others’ price and
political manipulation)
• Reduced global tension
• Local jobs and well‐being

47. The morning after (a sober re‐examination)
• Depends on success of plug‐in hybrids
– Will batteries work?
– What will they cost (money and CO2)?
• Growth rates mean oversight of
– Pinch points and shortages
– Prices
– Local content
– Financial manipulation
• Needs “the right” government involvement