Hex, Bugs and More Physics | Emre S. Tasci

Powering the Planet / Nathan S. Lewis
MRS Bulletin 32 808 2007

(Recommended by Prof. Thijsse)

This article is an edited transcript based on the plenary presentation given by Nathan S. Lewis (California Institute of Technology) on April 11, 2007, at the Materials Research Society Spring Meeting in San Fransisco.

• Richard Smalley’s collaborator.
• The problem is not the extinction of fossil based fuels, they will be available for the future (roughly 50-150 years for oil / 200-600 years of natural gas / 2000 years of coal). "This does not even include the methane clathrates, off the continental shelves, which are estimated to exist in comparable quantities to all of the oil, coal and gas on our planet combined."
• The article focuses on the planet in the year 2050:

  I chose 2050 for two reasons. First, achieving results in the energy industry is a much longer-term endeavor than, say, achieving results in the information technology business. In IT, for example, you can build a Web site and only a few years later become a Google. If you build a coalfired power plant, however, it will take about 40 years to pay itself off and deliver a reasonable return on investment. The energy infrastructure that we build in the next 10 years, therefore, is going to determine, by and large, what our planet’s energy mix is going to look like in 2050. The second reason for choosing 2050 is that today’s population wants to know what our planet’s energy picture is going to look like within a timeframe meaningful to them—the next 30 to 40 years.

• The real problem is the CO₂ emission. If we stop emitting carbondioxide as of this moment, it will be about 350 ppm by 2050. Even 550 ppm rate looks pretty hard to obtain. "We do not know, except through climate models, what the implications of driving the atmospheric CO₂ concentrations to any of these levels will be. There are about six major climate models, all differing from each other in detail."
• What can be done? 
  1 – Nuclear Power – Insufficient. 
  2 – Carbon sequestration – Very insufficient. "The U.S. department of Energy is doing work on carbon sequestration, with the goal of creating 1 gigaton of storage by 2025 and 4 gigatons total by 2050. Since the United State’s annual carbon emissions are 1.5 gigaton per year, the total DOE goal for 50 years from now is commensurate with a few years’ worth of current emissions.
  3 – Renewable Carbon-Neutral Energy Sources – Highly insufficient. Not the time, nor the areas are available for this to work. But we should head to the sun. "To put that another way, more energy from the sun hits the earth in one hour than all of the energy consumed on our planet in an entire year." Also there is some debate about using geothermal energy but the the low temperature difference that will practically let us extract much less than a few terrawats sustainably over the 11.6 TW of sustainable global heat energy.
• Solar cells / sun energy collectors must be cheaper about 1-10$/m². Also the energy can not be stored efficiently. We can store it by pumping water uphill for example, but by comparison, we will need to pump 50000 gallons of water uphill for 100 m to replace 1 gallon of gasoline.
• Energy solutions for the future: 
  1 – Photovoltaics – Efficient but highly expensive. 
  2 – Semiconductor/Liquid Junctions – Promising.
  3 – Photosynthesis – Must be researched for better efficiency.
• Energy saving : "Any realistic energy program would start with energy efficiency, because saving energy costs much less than making energy. Because of all the inefficiencies in the energy supply chain, for every 1 J of energy that is saved at the end, 4-5 J is avoided from being produced."
• The problem is severe and critical and there isn’t much time to act:

  Advocates of developing carbon-free energy alternatives believe that this is a project at which we cannot afford to fail because there is only one chance to get it right. For them, the question is whether or not, if the project went ahead, it could be completed in the time we have remaining. Because CO₂ is extremely long-lived, there are not actually 50 years left to deal with the problem. To put this in perspective, consider the following comparisons. If we do not build the next "nano-widget," the world is going to stay the same overt he next 50 years – it will not be better, perhaps, but it will not be worse, either. Even if we do not develop a cure for cancer in 50 years, the world is going to stay basically the same, in spite of the tragedy caused by that disease. If we do not fix our energy problem within the next 20 years, however, we can, as scientists, say with absolute certainty that the world will simply not be the same, and that it will change in a way that, to our best knowledge, will affect life on our planet for the next 3000 years. What this cange will be, we do not precisely know. That is a risk management question. We simply know that no human will ever have experienced what we will within those 50 years, and the unmitigated results will last for a time scale comparable to modern human history.

  If, on the other hand, we decided to do something about our energy problem, I am fairly optimistic we could succeed. As I have outlined, there are no new principles at play here. This challenge is not like trying to figure out how to build an atomic bomb, when we did not know the physics of bomb-building in the first place—which was the situation at the start of the Manhattan Project. We know how to build solar cells; they have a 30-year warranty. We have an existence proof with photosynthesis. We know the components of how to capture and store sunlight. We simply do not yet know how to make these processes cost-effective, over this scale. 

  Here, our funding priorities also come into the picture. In the United States, we spend $28 billion on health, but only about $28 million on basic solar research. Currently, we spend more money buying gas at the pump in one hour than we spend funding basic solar research in our country over an entire year. Yet, in that same hour, more energy from the sun is hitting the Earth than all of the energy consumed on our planet in that year. The same cannot be said of any other energy source. On the other hand, we need to explore all credible energy options that we believe could work at scale because we do not know which ones will work yet. In the end, we will need a mix of energy sources to meet the 10–20 TW demand, and we should be doing all we can to see that it works and works at scale, now and in the future. We have established that, as time goes on, we are going to require energy and we are going to require it in increasing amounts. I can say with confidence therefore, as Dr. Smalley did, that energy is the biggest scientific and technological problem facing our planet in the next 50 years.