It's somewhat ironic that the long-awaited approval of the Cape Wind offshore wind project by the Department of Interior (DOI) should come in the same week that the nation's attention is focused on the problems of another, more traditional offshore energy project. Although the renewable electricity from the former scarcely substitutes for petroleum from the latter, Cape Wind is nevertheless emblematic of an intentional shift from energy sourced far away, in places like the deepwater Gulf of Mexico, to energy derived from sources all around us. If Secretary Salazar had turned it down, it would have cast serious doubts on the administration's entire clean energy agenda. However, concurrence with this one project doesn't answer all questions concerning the larger shift, of which it represents just a small component. Similar issues are bound to come up with increasing frequency as the transition to new energy continues.
Cape Wind and the Macondo prospect that the Deepwater Horizon rig was drilling into represent opposite poles of the energy spectrum, and not just because the latter is now leaking oil into the marine environment at a rate that the latest estimate puts at 5,000 barrels per day, much higher than initially thought. Cape Wind would tap into the clean and renewable, but extremely diffuse energy sources that surround us. After taking into account the restrictions imposed by DOI, its 130 turbines would on average generate as much electricity as a gas turbine power plant consuming a quantity of natural gas equivalent to 6,000 bbls/day of oil. In other words, it takes a very large array of offshore wind turbines to match the energy in the oil currently leaking from a single well. Platforms similar to what BP might have been planning to install after successfully completing the exploration of Macondo routinely produce up to 20 times that much oil.
The implications of this huge difference in energy density are clear. Without the energy concentration that nature has embedded in fossil fuels over many millennia, the hardware required to tap natural energy flows in real time becomes vast in extent. Generating 20% of US electricity needs from wind, which some see as just the beginning, will ultimately require more than 8 times as much wind capacity as the 35,000 MW installed as of the end of last year, even if US electricity demand remains static in the interim. Solar power, which last year generated just 0.02% of our electricity, would have to increase by a much larger factor. This is one of many reasons that increased reliance on nuclear power is such an important element of the transition to more sustainable energy sources, because nuclear--and to a lesser extent geothermal power--represents a critical source of highly-concentrated, low-emission energy. The more nuclear in the mix, replacing baseload coal, the less we must rely on distributed energy gathered in our immediate vicinity.
In any case, in order to obtain a much larger portion of our energy diet from sources like onshore and offshore wind and solar power, projects like Cape Wind must go from being rarities to ubiquitous features of our seascapes and landscapes. The opposition to Cape Wind that has delayed this project for years is focused on a central dilemma of that shift: Many of the same underlying trends that lead us to want to harness clean energy from wind, sunlight and geothermal heat have also increased our focus on the broadly-defined environmental impacts of doing so.
Our grandparents wouldn't have blinked at putting up tens of thousands of wind turbines, let alone the few hundred slated for Nantucket Sound. They'd have thought of them as signs of progress, just as they viewed oil derricks and power lines. It's incumbent on us to balance our more modern sensibilities related to the "viewscape" with fundamental environmental challenges of climate change and sustainability, as well as the need to sustain the energy supplies our civilization requires. Approving Cape Wind--whether it eventually gets built or not--is entirely consistent with those imperatives.
Showing posts with label sustainable energy. Show all posts
Showing posts with label sustainable energy. Show all posts
Thursday, April 29, 2010
Tuesday, June 23, 2009
Sustainable Energy
I just ran a quick search on Google Trends to check my hunch that the phrase "sustainable energy" has become a lot more common, lately. That seems to be the case, at least based on the volume of news references tracked by Google. While I would regard a greater focus on sustainability as a positive development, I'm much less comfortable with its indiscriminate use as a synonym for "renewable". It's dangerously simplistic to think that the only parameters of sustainability that matter for a given energy technology are the extent of the energy supply it taps and the greenhouse gas emissions associated with its use. However understandable that might be in light of concerns about climate change and energy security, the complexities it obscures could ultimately prove just as limiting, in their own way, as the depletion of finite reserves of fossil fuels or the response of the global climate to increasing concentrations of carbon dioxide in the atmosphere.
Sustainable energy means different things to different people, as even a Wikipedia definition that points mainly to standard renewables admits. All too often, though, these definitions focus on the consumption of fossil energy sources and their accompanying emissions, while ignoring the use of other scarce resources, particularly water. In a recent posting I highlighted the high water consumption associated with the production of corn ethanol, a fuel widely regarded as more or less infinitely renewable, and thus much more sustainable than the oil it is intended to displace. Ironically, petroleum production and refining on average consume far less water per gallon or BTU of marketed fuel than most biofuels. The production of biofuels from non-food sources requiring little or no irrigation would alter that comparison, but still might not close this gap.
Biofuels aren't the only components of our energy mix that use lots of water. Electricity generation also consumes huge quantities, though much of it is returned downstream without degradation. Most thermal power plants use water for cooling and steam generation. That includes both fossil and nuclear power plants. Some renewable energy sources are also subject to this constraint, including solar thermal power, as noted in a recent Washington Post article. Enhanced geothermal power, which has great potential as a low-emission energy source, requires the injection of large volumes of water underground to create artificial hydrothermal reservoirs, and to transfer heat to the surface for power generation. In fact, at least 80% of the electricity generated in the US last year involved the use of water to some degree, a dependency that attracted critical attention during the Southeast drought in 2007.
Water is hardly the only input that should be considered in a broader view of sustainable energy. The consumption of rare earths and scarce metals in the production of thin-film solar panels, advanced batteries, wind turbine generators, and other aspects of the developing green-energy economy is starting to worry some experts. While I haven't delved into it in much detail, I'd be surprised if these factors proved limiting in the near term. After all, the technologies in question have only been around for a few years, so there hasn't been much time for the sources of these exotic ingredients to ramp up to support their growing demand. This scaling issue cuts both ways, however. For example, if solar energy is to expand from its present contribution of less than 1% of renewable power generated here last year to, say, 10% of our total power supply, the use of an ingredient in proportions as small as a hundred grams per kilowatt of capacity would translate into a cumulative requirement for tens of thousands of tons. If the substance in question was the Tellurium used in Cadmium-telluride solar cells, its global output would have to expand by at least 10X within a decade or two. That might not be possible, or at least economically feasible.
The point here is not to suggest that we're stuck in some depressing dynamic in which we encounter bottlenecks and unintended consequences in every direction we turn, as we seek alternatives to conventional energy. Instead, we need to remember that oil, gas and coal aren't the only finite substances in the earth's crust. We must consider all our energy options in terms of trade-offs, and not just with regard to the aesthetics of wind farms and solar panels in our back yards vs. oil derricks and central power plants in someone else's. The choices we are making demand a thorough look at their lifecycle impacts, including all the inputs and outputs along the way. That won't be easy, and it clearly will not be convenient for those sectors that have benefited from an overly narrow view of this issue, such as the interests that are supporting legislation to block the EPA from factoring in the effect of global land-use changes in the agency's lifecycle assessment of corn ethanol.
This broader view of sustainable energy is another reason to moderate our faddish focus on all things renewable, as I noted recently when I argued that we need a low-emission electricity standard, instead of a renewable electricity standard. Tackling climate change effectively will require clear goals that address outcomes, rather than preconceived notions about pathways. And when it comes to energy security, we need a framework that recognizes that oil in tankers is not the only energy-sector import that bears watching.
Sustainable energy means different things to different people, as even a Wikipedia definition that points mainly to standard renewables admits. All too often, though, these definitions focus on the consumption of fossil energy sources and their accompanying emissions, while ignoring the use of other scarce resources, particularly water. In a recent posting I highlighted the high water consumption associated with the production of corn ethanol, a fuel widely regarded as more or less infinitely renewable, and thus much more sustainable than the oil it is intended to displace. Ironically, petroleum production and refining on average consume far less water per gallon or BTU of marketed fuel than most biofuels. The production of biofuels from non-food sources requiring little or no irrigation would alter that comparison, but still might not close this gap.
Biofuels aren't the only components of our energy mix that use lots of water. Electricity generation also consumes huge quantities, though much of it is returned downstream without degradation. Most thermal power plants use water for cooling and steam generation. That includes both fossil and nuclear power plants. Some renewable energy sources are also subject to this constraint, including solar thermal power, as noted in a recent Washington Post article. Enhanced geothermal power, which has great potential as a low-emission energy source, requires the injection of large volumes of water underground to create artificial hydrothermal reservoirs, and to transfer heat to the surface for power generation. In fact, at least 80% of the electricity generated in the US last year involved the use of water to some degree, a dependency that attracted critical attention during the Southeast drought in 2007.
Water is hardly the only input that should be considered in a broader view of sustainable energy. The consumption of rare earths and scarce metals in the production of thin-film solar panels, advanced batteries, wind turbine generators, and other aspects of the developing green-energy economy is starting to worry some experts. While I haven't delved into it in much detail, I'd be surprised if these factors proved limiting in the near term. After all, the technologies in question have only been around for a few years, so there hasn't been much time for the sources of these exotic ingredients to ramp up to support their growing demand. This scaling issue cuts both ways, however. For example, if solar energy is to expand from its present contribution of less than 1% of renewable power generated here last year to, say, 10% of our total power supply, the use of an ingredient in proportions as small as a hundred grams per kilowatt of capacity would translate into a cumulative requirement for tens of thousands of tons. If the substance in question was the Tellurium used in Cadmium-telluride solar cells, its global output would have to expand by at least 10X within a decade or two. That might not be possible, or at least economically feasible.
The point here is not to suggest that we're stuck in some depressing dynamic in which we encounter bottlenecks and unintended consequences in every direction we turn, as we seek alternatives to conventional energy. Instead, we need to remember that oil, gas and coal aren't the only finite substances in the earth's crust. We must consider all our energy options in terms of trade-offs, and not just with regard to the aesthetics of wind farms and solar panels in our back yards vs. oil derricks and central power plants in someone else's. The choices we are making demand a thorough look at their lifecycle impacts, including all the inputs and outputs along the way. That won't be easy, and it clearly will not be convenient for those sectors that have benefited from an overly narrow view of this issue, such as the interests that are supporting legislation to block the EPA from factoring in the effect of global land-use changes in the agency's lifecycle assessment of corn ethanol.
This broader view of sustainable energy is another reason to moderate our faddish focus on all things renewable, as I noted recently when I argued that we need a low-emission electricity standard, instead of a renewable electricity standard. Tackling climate change effectively will require clear goals that address outcomes, rather than preconceived notions about pathways. And when it comes to energy security, we need a framework that recognizes that oil in tankers is not the only energy-sector import that bears watching.
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