global strategy begins with control," says BÃ©la LiptÃ¡k in his Lessons Learned column from the September issue of CONTROL magazine. Not so fast, BÃ©la. It begins by accurately defining the problem to be solved, which, in this case, is multifaceted and cannot be adequately described by such a simple statement. Nor will the solution to our nations energy issues have a single dimension. It will be multidimensional and as diverse as our current energy industry.
Control has a role
As industry and society grapple with the many facets of the problem, it will remain true that the role of control is to make sure the many parts of the solution operate safely and efficiently. And for the control engineers behind this effort, it is certainly a noble calling. As an educated part of the public, control engineers will also participate in the public debate and likely be notable agents of change speeding the evolution of the energy industry to whatever form it may take.
Perceiving the problem
"We all know that oil will run out by the end of this century." The problem is not really one of supply, or in other words, a scarcity of recourses. The problem is how to supply and distribute energy we have.
There are multiple sources of energy and energy, like money, is fungible. Substitution between sources can, does and will occur based on price and production costs. According to the Energy Information Administration (EIA) oil represents only 39% of U.S. energy consumption (Annual Energy Outlook 2004, 2002 actual consumption). If oil becomes disproportionately more expensive than other sources its contribution to the overall energy mix will decline.
Initial steps in this economic process would include direct substitution, where oil does not have a technical advantage. Presumably, this would include fixed power generation where coal, gas, nuclear, or fixed-position renewables (hydroelectric, wind, tidal, solar cells, etc.) could substitute without generating costs higher than the oil such alternatives would replace. But a factor that may sustain oils key role in the energy mix is its inherent transportability because it is a liquid. Transportation is a major cost issue and liquid fuels have a distinct cost advantage because of their ease of handling and high energy density. Energy source substitutions will occur here also, but for a price. The most viable substitutes to oil will most likely continue to be liquid fuels.
Nonetheless, there is a report by the EIA that postulates rapid declines in conventional oil reserves starting anywhere from ~20252075 and eventual production decline to below 1 billion bbls/year by 20752125. The problem with the projection is the fact that the report ignores non-conventional reserves (tar sands, oil shales, etc.) which exist in large quantities around the globe. It also makes no reference to outer continental shelf production potential. Heres what the World Energy Council has to say about that: Today, the potential represented by deep offshore resources has not yet been clearly determined. Sedimentary areas lying in over 200 m of water represent nearly 55 million kmÂ² of sedimentary basins, or four times the conventional offshore surface area.
An unfinished oil portrait
One needs to consider all energy sources and how energy is, and will be used when postulating the character our energy future. To focus on one source (oil, coal, etc.), especially without considering where, how, and how much energy will be used, or how existing infrastructure might be reused or adapted, will only paint a very incomplete picture. Any conclusions drawn from that will be erroneous.
The oil picture is still very incomplete. It would seem that we have a good picture of probable conventional oil reserves based on current technology, but have a very incomplete image when one considers non-conventional sources, the ultimate recovery from conventional sources via technical advances, and our ability to take advantage of potential reserves in deep water out on the continental shelf.
The probable final outcome will be determined by relative cost between the sources. Depending on how much one wants to spend most of the oil out there is probably recoverable. Whether we eventually recover 30% or 70% depends on relative costs. If renewable energy costs drop oil may eventually cease to be important not because it is scarce but because it isn't cost effective.
When will we run out of non-renewable energy sources like oil? Still unknown. We will run out of fossil resources (by definition), but when is still largely conjectural and is probably much farther out than the end of this century.
Big idea, questionable economics
LiptÃ¡k proposes renewables on a grand scale might provide for our future energy needs: Start by building gigantic, floating islands covered with solar collectors and positioning them around the equator, he offers. But before we judge the merits of such a proposal, consider the following:
Worldwide energy demand: Assuming a world population of 15 billion in 2100 with per-capita consumption at the current U.S. level (97.72 Quad/yr (EIA) for 300 million (U.S. Census Bureau) world energy demand would be about 4,900 Quads/year.
Surface area required to support solar cells: Assuming 100% energy supply from solar cells (a very poor assumption, but necessary to put a scope on the problem) we can calculate the required area that must be dedicated to energy collection. Solar energy density (per Lessons Learned, sidebar) is 500,000 BTU's/ft2/year at the equator, less as we move away from the equator (13% reduction at 30Â° latitude, 50% at 60Â° latitude). Solar cells are around 15% efficient. Taking additional discounts for bad weather, maintenance, stranded sources, etc. we could arrive at 2% (or less). Assuming 2% efficiency we need to cover about 17,500 square miles of the earth's surface with solar cells to meet 100% of our energy needs. This is a miniscule percentage of the Earth's 197 million square- mile surface area, so the proposition is not unreasonable.
Cost of floating platforms: I do not have a good estimate of offshore platform infrastructure costs, but believe $2,500/ft2, or about $56 billion/square mile is not unreasonable (anyone have a better number?). To support 17,500 square miles of offshore platforms might cost $975 trillion exclusive of costs associated with solar cells and hydrogen generation, compression, and transportation facilities.
There has got to be a cheaper way. Why not mount on existing roofs? It would seem there is a lot of roof already out there. To arrive at a ball-park estimate let's assume 500 ft2 of roof per person by 15 billion people, or about 270,000 square miles of available surface. That's plenty. This has the advantage of keeping energy generation close to the population centers (literally on the roof). Alternately we might mount them in the deserts, there are plenty of these, too, but unfortunately are not as close to the users.
What about hydrogen
Many, including CONTROLs columnist look towards turning that solar energy into hydrogen. Why convert it? Before we assume anything about conversion and transportation modes for hydrogen we need to determine how the energy gets used. Assuming we use solar energy we also need to determine how to store energy through the night.
Per the EIA, about 27% of U.S. domestic energy usage is for transportation. The remaining 73% represents (for the most part) fixed consumers who's energy needs could presumably be met by electricity. Residential needs could presumably be generated "on the roof" for most homes within 45Â° of the equator (20% of current usage).
Industrial and commercial consumers (53%) would likely have higher energy demands than could be accommodated onsite, therefore an electrical distribution system would be required (and it already exists!) The probable model would involve sales from production in excess of demand from residential and low power consumption industrial/commercial users (warehouses, malls) and production for purpose (solar farms) to the electrical grid for use by large consumers. The advantage is this uses existing infrastructure; however some technical changes would be required to support decentralized power generation. The advantage here is no conversion (to hydrogen or anything else with its attendant inefficiencies) is required to meet most energy requirements.
Overnight storage does not present much in the way of a technological hurdle and could be accomplished by any combination of electrical, mechanical, thermal, or chemical means (batteries, flywheels, water ponds, etc.).
As mentioned, liquid fuels dominate because they offer ease of distribution and handling combined with a high energy density. Areas with low population densities and/or a low level of technical achievement are not likely candidates for any other type of fuel. Hydrogen (or any gaseous fuel) does not offer the same distribution efficiencies, and when you factor in the weight of the containment vessel, it doesn't offer as high an energy density. Similarly, batteries offer their own set of problems.
Picture this â¦
A likely scenario would be that liquid fuels would still dominate, but that the sourcing would change from oil to solid fuel (coal, bitumen) liquifaction possibly using hydrogen from water dissociation, agricultural (fermentation to alcohols and/or hydrogenation of cellulosics), and synthesis from CO2 and hydrogen (assumes green house gas emission recovery occurs and CO2 becomes available in high volumes at low cost). High density transportation may very well move away from liquid fuels (electricity for railroads, nuclear for ships, compressed gas or possibly hydrogenfor buses). Maintaining the existing liquid fuels distribution infrastructure and existing technical know how would seem to be much more economic than replacing it with a new infrastructure. (Need we digress into the safety issues of hydrogen - high flammability limits with almost assured ignition from any high pressure leak for example.)
One could see hydrogen taking a part in the future economy as a gradual substitute for natural gas through the existing natural gas transmission system. Hydrogen could be generated at the gulf coast and mixed with natural gas for transport. Percent hydrogen would be raised by say 5%/decade, a rate slow enough to allow the replacement of natural gas appliances at the normal expected retirement rate, each generation redesigned for use with the current gas composition as required due to the very different air/fuel ratios and fuel flow rates per BTU for natural gas versus hydrogen. Ultra-high pressures, slurries, or other exotic solutions would not be required.
Regardless, let's stay away from statist solutions. No cadre of experts, no matter how well educated can reasonably be expected to optimize our energy future and that includes the Global Academy of Science. That experiment has been run and didn't work well. The market works because the guys making the decisions are putting their own money on the line and therefore, have a strong incentive to get it right. There will also be many more people working on (parts of) the problem than any academy could support, and by covering more ground are more likely to find the right solution. Sure, a lot of people will get it wrong (and lose a lot of money), but some will get it right. Yes, there is a place for government support of research, but no place for coercion.
This is not to say that some aspects of a hydrogen economy will not emerge. However, it will at best be a small part of the overall energy supply and distribution solution. The optimum solution is the one that solves the problem the most economically, not the one with the best toys or sexiest publicity. Economics will (or should) dictate our energy future.