Sunday, October 21, 2007

Solar Energy - Heat or Hype ?

There is so much written about solar energy these days, that it almost reminds one of the Internet days of 2000. Stocks like SunPower are at 400+ PEs and new startups are getting funded in the 10s of millions of dollars. It almost begs the question - how hot is it and will the trend continue for ever? I had been wondering about this question when I got an invite to a talk on "Current Status and Future of Solar Energy" from the speaker himself, Dr. Amit Kumar. Talk about coincidences. :-) The talk was on October 17th at the PARC auditorium in Palo Alto and was hosted by the MEMS Journal club.

Dr. Amit Kumar did his Ph.D research in Photovoltaics at Stanford and Caltech in the late 80s and early 90s, and is now CEO of a publicly traded biomedical company and is on the boards of several solar energy companies. The talk was well laid out and had a wealth of data drawn from a variety of sources including Dr. Kumar's own estimates.

Current worldwide energy use is 14-15 Terawatts (TW), with the US consuming about 4 to 5 TW. Of the total worldwide energy consumption, about 12TW is from fossil fuels, 1.5TW from hydroelectric and biofuels, 1TW from nuclear and 0.2 TW from all other including solar. In 30-50 years this 15 TW is expected to grow to 30TW from population growth, emerging nations consumption and economic growth. One of the estimates which surprised me was the fact that about 3.5TW of the 4TW US consumption came from transportation related energy consumption (planes, trains, ships and automobiles). The vast infrastructure put in place to deliver oil and gas worldwide from raw material to consumable gasoline enables it to be sold at prices cheaper than most other liquids except tap water. :-)

If fossil fuels continue to be the primary source we will continue to pump carbon into the atmosphere (currently estimated at 8 billion tons/yr) aggravating any existing problems. Dr. Kumar estimates resources for oil, gas and coal to be 120, 300 and 1500 years, respectively. He then considered each of the alternative energy sources in terms of their opportunities, challenges and potential to supply the global energy requirements.

Cleaning up fossil/bio fuel use with carbon sequestration methods allows continued use of fossil fuels with less of their problems. However, challenges here are entropy, cost, capacity and leakage. Without technical breakthroughs it does not look easy. Geothermal and ocean tides have the potential to supply 70 TW, but economically feasible capacity is on the order of 2TW and installed capacity is minimal.

Hydroelectric has a gross potential of 4.6TW and installed capacity of 0.6TW in 1997 and a possible 0.3TW more production increase. Problems include capital cost and issues like the relocation of a billion people (?) for the Three Gorges dam in China. In India, I am aware of some projects shelved due to environmental impact.

Wind energy has a theoretical land potential of 10 TW and practical potential of 2TW. Offshore potential can be up to 5TW. But, wind power is intermittent, needs storage and has distributed generation restricted to some areas only. It is viable, supplying at close to grid power rates where it is deployed.


Biofuels like Ethanol need large land areas for cultivation and have energy densities close to half of gasoline and cost more in energy to make than we can get out of them. They are also water resource limited for cultivation. If all available land is cultivated 8-10 TW is possible, but practical potential is 1-2TW. Their primary attraction is being able to use the existing fossil fuel distribution infrastructure and subsidies.

Nuclear fission is a viable alternative, and much capacity is deployed worldwide and even in the US. Estimate that 20% of US power is nuclear. Waste disposal, uranium availability and weapons and terrorism concerns are major issues. To get 10TW we need 10000 plants, which seems like quite a lot to build. So, delivered capacity from nuclear is limited to the number of 1GW plants that will be built.

Solar has a theoretical potential of 120,000 TW if irradiation of the whole earth's surface is considered. Practical possibility is about 1200 TW. To deliver 3-4 TW at 10% solar cell efficiency needs land area of about 250miles x 250 miles or 62500 sq miles. Currently we have about enough solar modules to cover 50-100 sq. miles. Even this is a $30B market. So, we have a long way to go :-) Maybe, the high PE of the solar panel makers are justified :-) But, there's more to this story. One of the limitations of solar energy is that its not very concentrated. Rooftops and other viable sources can only provide about 10% of the surface area required. The rest has to come from generating installations which can be capital intensive. One can see why many startups are targeting this space. Capacity is increasing, but nowhere near what is required. Silicon may be a limitation even at current levels.

One main issue with solar energy has been the cost. While coal, gas, oil, wind and nuclear have generating costs between 5-8 c/kWh, (with coal the cheapest at 5c/kWh), solar energy costs about 25c/kWh. This does not even include the costs for storage and distribution. Dr. Kumar quoted his thesis advisor, who compared funding solar energy generation to funding the Apollo mission if Southwest were to provide $29 shuttle missions to the moon. Clearly, in spite of these economics, many VCs are pumping billions of dollars into solar energy. Other challenges for solar include inverters for DC-AC conversion and storage.

Cost may be reduced with scale, manufacturing improvements and new types of cells. Efficiencies range from about 25% for crystalline silicon to about 15% or lower for CIS/CIGS, CdTe, amorphous silicon and nano TiO2. The market is dominated by single crystal silicon (92+ %). followed by CdTe, CIGS and particle based cells. Exotic structures like tandem cells and paints are in their infancy. Most of the non-Si technologies have still not achieved the scale of manufacturing capability that is required. Till they do, its too early to make a call on their viability and scaling possibility.

New opportunities in solar include new types of cells and structures, storage and inverters, thin film material and cells, silicon supply and other materials, installation and repair, electric vehicles and catalysts for hydrogen evolution. Cost reduction is a major challenge. The environmental impact of some of the technologies used is another.

Dr. Kumar concluded that in the midst of a global energy crisis we are forced to look at alternatives to fossil fuels and solar is clearly one of the better alternatives. But, we also need massive changes to our way of life, conservation and more efficient products for lighting and transportation and an effort in alternative energy bigger than the Manhattan and Apollo projects. Dr. Kumar can be contacted at amitoptigon (at) hotmail (dot) com.

I am glad that I attended this talk, because it gave a broad overview of many different alternative energy methods and their relative impact and potential. However, the answer to the question of how much of the solar buzz is hype and how many bumps there will be in the road between now and when solar energy is a viable energy alternative to fossil fuels, is still elusive. With oil close to $90/barrel, its easy to fund alternative energy work. But, what happens if oil were to go back to $20/barrel ? Maybe with the impact of global warming being felt worldwide, there would still be an impetus to drive alternative energy. But, with more oil accessible from the less ice-locked Arctic and Greenland, does it drive a vicious cycle of more oil based economies ? :-)

If I were to guess, the VCs will fund more solar energy companies. Silicon Valley will continue to be at the center of much of this action. There will be a few phenomenal successes, as there were in the Internet boom days, and there will be a few fadeouts. However, there will be much energy generated(pun intended :-)), lots of action and excitement and a few millions to be made for the entrepreneurs and investors. The valley will have contributed to global development in yet another realm, maybe with more impact than the previous semiconductor and internet cycles. The more things change, the more they remain the same :-).


3 comments:

jaq said...

Some of the #s that were posted here are startling. Many figures are contrary to numbers calculated by various energy agencies. Furthermore, the figures are all biased against the renewables.

Why does the author need to provide new estimates for statistics that have been routinely monitored and calculated by industry professionals?

Why would you chose language that misrepresents actual numbers? I am no fan of ethanol, but you have to be honest about things. For instance, 70% is reported as "close to half" if you insist on goofy language rather than straight numbers, this would actually approach three quarters. Similarly, the post claims that energy density is a problem with "biofuels." In fact, this is not true in general - only ethanol. I find many misleading statements like this one within the post.

Another example is the opening statistic, the comparison of energy consumption of the US vs. the world. Your reported numbers are sloppy. A 15% uncertainty in the US fraction of energy? Incidentally, that 15% window is between about 0% and 15% larger than the figures reported by the US DOE.

Why would someone chose to misrepresent facts like this?

ak said...

jaq makes some good points in his comments, but misunderstands the key point of the presentation, as he probably did not have the benefit of hearing the speech. First of all, the estimates and calculations in all of the areas are composites of estimates from multiple sources in some cases. In others, they are from single sources. The key point, however, is that all of these numbers and those from other sources, including those to which jaq is referring, are all the result of an elaborate number of assumptions and estimates. Therefore, these numbers as well as other could easily be off by 10s of percentage points and even by factors of 2.

That being said, the main points of my presentation were that of the many alternative energy options, the combination of solar, nuclear and biofuels are viable enough to address energy issues at a global scale. However, each has its challenges- for example ethanol from corn kernels is not viable long term. Ethanol from switch grass or a weed that grows in areas that are not needed to grow food is possible, but we cannot technically convert switch grass to ethanol. Maybe we will in a few years and that will make it viable. But if you are going to compete with land and water resources needed for food production, it will not work on a global scale. Problems with solar include cost, capacity, etc. Problmes with nuclear exist as well. Wind and hydro are great, but there is just not enough capacity to impact energy issues at a global scale What about geo, tide, etc. These are all good things to work on, but on a global scale they will probably not be meaningful with out technical advancements. Sure there will be plants that produce megawats and maybe gigawatts but on a global scale we are talking tens of terrawatts. I never implied that economically these alternatives would not be successful. In many cases, they will be successful and will provide returns to investors and power to customers. Wind and hydro already are doing this, and other alternatives are coming on line. My point was that when thinking about supplying 30 Terrawatts to the world, you needed a lot more.

Amit Kumar

skipper386 said...

nice article! i am now starting to like solar energy as another way of source of power! Solar Power in Queensland

 

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