100% Renewable Energy Indeed Possible, say Stanford U. Researchers
May 01, 2011 - sustainablebusiness.com
The world can be powered by renewable energy in 20-40 years - using technology available right now, says Stanford researcher Mark Jacobson.
According to their plan, wind and solar can provide 90% of energy demand through electricity. Geothermal and hydroelectric sources would each contribute about 4% (70% of hydro is in place now), and wave/tidal would supply the remaining 2%.
Vehicles, ships and trains would be powered by electricity and hydrogen fuel cells. Aircraft would run on liquid hydrogen. Homes would be cooled and warmed with electric heaters and water would be preheated by the sun. Commercial processes would be powered by electricity and hydrogen.
Because all combustion processes would be converted to electricity, including hydrogen production, the plan would result in a 30% reduction in world energy demand. Electricity is much more efficient than combustion.
How do they do this cost effectively? By reducing energy demand and by factoring in the savings that would accrue through lower health care costs associated with air pollution from fossil fuels.
"When you actually account for all the costs to society - including medical costs - of the current fuel structure, the costs of our plan are relatively similar to what we have today," Jacobson says.
A major obstacle with widespread use of wind and solar energy is its variability - they don't provide "base load" power, the minimum amount of energy that must be available to customers at any given hour of the day.
Jacobson says that can be overcome by packing them into a bundle. "If you combine them as one commodity and use hydroelectric to fill in gaps, it is a lot easier to match demand," he says.
Since wind often peaks at night and sunlight peaks during the day, they are complementary. Using hydro to fill in the gaps - as it does now - allows demand to be precisely met by supply in most cases. Other renewable sources such as geothermal and tidal power can also be used as supplements.
"One of the most promising methods of insuring that supply matches demand is using long-distance transmission to connect widely dispersed sites," says co-author Delucchi. Even if conditions are poor for wind or solar energy generation in one area on a given day, a few hundred miles away the winds could be blowing steadily and the sun shining.
"With a system that is 100 percent wind, water and solar, you can't use normal methods for matching supply and demand. You have to have what people call a supergrid, with long-distance transmission and really good management," he said.
Another method of meeting demand could entail building a bigger renewable energy infrastructure to match peak hourly demand and use non-peak excess electricity to produce hydrogen for the industrial and transportation sectors.
Using pricing to control peak demands, a tool that is used today, would also help.
They also examined whether the earth has enough resources to build out a renewable energy infrastructure. They concluded that even supplies of rare earths and platinum are sufficient. Recycling could effectively extend the supply.
"For solar cells there are different materials, but there are so many choices that if one becomes short, you can switch," Jacobson said. "Major materials for wind energy are concrete and steel and there is no shortage of those."
Jacobson and Delucchi calculated the number of wind turbines needed to implement their plan, as well as the number of solar plants, rooftop photovoltaic cells, geothermal, hydroelectric, tidal and wave-energy installations.
They found that to power 100% of the world for all purposes from wind, water and solar, about 0.4% of the world's land would be needed for solar, about 0.6% for wind. Turbines need to be spaced out to prevent interference between them.
"Most of the land between wind turbines is available for other uses, such as pasture or farming," Jacobson said. "The actual footprint required by wind turbines to power half the world's energy is less than the area of Manhattan." If half the wind farms were located offshore, a single Manhattan would suffice.
Only about 1% of the wind turbines required are in place now, and less than that for solar.
"This really involves a large scale transformation," he said. "It would require an effort comparable to the Apollo moon project or constructing the interstate highway system."
"But it is possible, without even having to go to new technologies," Jacobson said. "We really need to just decide collectively that this is the direction we want to head as a society."