Let's take a systems approach to describing the problem and the impacts of the potential solution alternatives. The main problem is oil consumption, but cascading problems from PO can include heightened use of other fossil fuels, so these are included as well.
DEMAND
1. Transportation: 40% of oil in US is used for this purpose, including;
a. Personal Transport (cars)
b. Aggregate Transport (buses, planes)
c. Goods Transport: Long, medium, short haul (trucks, container ships, planes)
Primary Needs: Gasoline, Diesel
2. Heating
a. Home
b. Commercial
c. Industrial processes
Primary Needs: Heating oil
3. Petroleum-Based Products
a. Plastics
Primary Needs: Petroleum
4. Agriculture
a. Plowing, tilling, harrowing, harvesting, etc.
b. Greenhouse heating
c. Fertilizer (NG)
Primary Needs: Gasoline, NG
5. Electricity Production
Primary input: Coal
POTENTIAL DEMAND MODIFICATIONS
A. Reshaping Human Settlement Patterns
Focusing new growth and mass transit in urban areas
http://www.carfree.com
Major Demand Improvements: 1a, 1b, 2a, 2b (more shared walls)
Minor Demand Improvements: 1c
B. Increased energy efficiency
CAFE increase, higher standards for appliances, HVAC, industrial processes, etc
Major Demand Improvements: 1a (amplified when concurrent with A.), 1b, 1c, 2a, 2b, 2c, 4a,
Minor Demand Improvements: 4b
C. Alternate modes of transportation
Bikes, Buses, Mass Transit, Walking
Major Demand Improvements: 1a.
Minor Demand Improvements: 1c
SUSTAINABLE ENERGY SOURCES
(Note: if a source can generate electricity, that electricity can be used to charge batteries, run subways, drive HVAC systems, etc. it can also be be used to produce H2, hence the many potential improvements noted below)
D. Wind
Major Demand Improvements: 5 (if H2 gen, 1a, 1b, 1c, 2a, 2b, 2c, 4a)
Minor Demand Improvements: 4b
E. Solar PV
Major Demand Improvements: 5
(limited market penetration until costs are reduced)
F. Solar Thermal (including H2/electricity gen)
Major Demand Improvements: 1a, 1b, 1c, 2a, 2b, 2c, 4a, 4b, 5
G. Hydro Generation/Storage
Major Demand Improvements: 1a, 1b, 1c, 2a, 2b, 2c, 4a, 4b, 5
H. Tidal Power
Major Demand Improvements: 1a, 1b, 1c, 2a, 2b, 2c, 4a, 4b, 5
I. Wave Power
Major Demand Improvements: 1a, 1b, 1c, 2a, 2b, 2c, 4a, 4b, 5
J. Geothermal Power
Major Demand Improvements: 1a, 1b, 1c, 2a, 2b, 2c, 4a, 4b, 5
LIMITATIONS
The above raw assignments must be brought into context of existing infrastructure and inherent shortfalls. For example, all gasoline cars on the road today will not vanish overnight; infrastructure shifts will take time. And passenger planes will not fly on batteries. I will not endeavor to cover all limitations, but focus on some of the more meaningful.
I Transportation Safety.
Simply shifting a small percentage of commuters to bicycles will see a proportional drop in oil consumption. However, unless weather considerations are addressed via full fairings, the number will remain small during pre-peak. Conflicts between human powered vehicles and 4000 lb autos/trucks will limit the number of 'converts'.
http://www.velomobiles.net/
II Grid Stability
As one poster remarked. we cannot simply power our grid with simple renewable energy sources without consideration of baseload requirements and demand peaks, both seasonal and diurnal. To keep a grid stable, the dispatcher must have enough power to maintain daily minimum power supply (baseload) and be able to control dispatchable power, such as hydro or natural gas turbines. Many renewable sources are intermittent (solar, wind), available only as the weather allows. If the sun isn't shining and the wind isn't blowing, we can't simply shut down a whole country or continental region. Hydro storage may help, but a baseload provider is needed, which could be hydro generation and possibly nuclear for the interim, until fusion is developed.
Denmark is currently powering their over 20% of their grid capacity with wind power, so extensive use of a plentiful intermittent source is feasible.
Demand Side Management (DSM) can also be used to mitigate intermittent shortfalls; constrained spot pricing can be used as well.
Personal initiative could also be viewed as a limitation; how many people make major purchases with energy use as the primary consideration? Not many Americans, with some exceptions; our house is highly insulated, passive solar heated (also have woodstove), with photovoltaic panels powering energy efficient appliances/HVAC. I take a bus to work and drive a Honda Insight when I have errands that I can't bike to. The family car is a Prius. I would have preferred to live close to a subway location, but all the homeowner convenants restricted solar panels, and most existing homes would have required very extensive renovation. Simply noting the difficulties setting up a clothesline in California during their energy crisis calls out the impediments to personal initiative in these areas.
CONCLUSIONS
Our electric and fuel bills are about an order of magnitude less than those of our SUV driving neighbors. Such reductions are within relatively easy reach if energy efficiency ratings for automobiles/homes were signficantly improved, and options for renewable energy generation (PV primarily) were part of the sales options on homes.
So the primary changes that can bring about a transition to the establishment of sustainable energy sources as a our primary sources are by first lowering our high energy consumption levels through;
A. Reshaping Human Settlement Patterns
(includes localization of goods and food production, i.e., bringing back horse-powered family farms)
B. Increased energy efficiency
C. Shift to alternate modes of transportation
The above measure will allow us to then shift to sustainable energy sources. Please comment on areas missed, so that this can be updated to reflect your input.