What can “Green” energy do for us?

2009/03/12

Originally, this was intended to be a post about whether or not ‘Green’ energy technologies could be used for economic stimulation in our current recessiony situation, but ultimately, I found that in order to do that post, I needed to do what this post has now become, first. As with all things ‘Green’, I assume that this refers to energy technologies that are environmentally friendly; for the moment, I will forego questioning whether or not it is a good idea to guide our economic recovery according to the tenets of an ideology that is still subject to intense debate (yeah, that’s right…I don’t blindly accept doom-and-gloom prophecies emanating from the Oracle of Gore – try not to judge me too harshly). WRT the energy technologies themselves, these are typically referred to as renewable, since the fuel used for producing the energy itself is either ‘free’ (as in the case of solar, wind, geothermal, etc.), or can be derived from a resource that can be replenished (as in the case of the various biofuels). Many of these technologies have been around for years (decades, in some cases), so the question that arises is, why aren’t they already being used on a large scale?

In the case of most of the traditional technologies (solar, wind, geothermal, hydroelectric, etc.), the primary limiting factor is location (location, location). In particular, geothermal and hydroelectric have very specific location requirements, and cannot be used just anywhere, e.g. hydroelectric power plants require moving water of some kind (ideally of a high volume), and there are only a few rivers in the country that are suitable for these purposes (and indeed, many of these rivers are already utilized for hydroelectric power – see the Hoover Dam or the Niagara River, for examples). Wind, as anyone who’s been outdoors can attest, is much more widespread. The limiting factor here is one of scale; since air has a much lower density than water, wind-generated electricity requires far greater numbers of turbines to produce useful amounts – hence, the growth of the giant wind farms that have sprouted up around the country. As these wind farms require large areas of clear land, and adequete wind veloceties to warrant building the farms in the first place, they cannot be built anywhere; additionally, they cannot be built in or near the centers of highest energy demand (cities), again, due to the scale of the farms themselves. Photovoltaics (solar) have become much more promising within the past couple of years, and there are some interesting statistics available [1],  but it is unclear if these cells can be utilized on a large enough scale to be effective at energy production on the scale required to address the nation’s energy demands. Solar collectors (facilities that use mirrors to collect and focus sunlight to heat a fluid that flows into a turbine to generate electricity) suffer from similar location-specific limitations as geothermal and hydroelectric; ideally, they need to be built in areas that are relatively cloud-free (like in the desert), so that they can collect as much sunlight as possible. Theoretically, such collectors could be built anywhere, as the sun shines everywhere, but I suspect that they would be far less efficient in New England than they would be in Arizona.

Location limitations aside, however, the biggest problem we face with implementing any ‘Green’ energy sources is the scale on which we would need to utilize said technologies. Based on current statistics (2007) according to the U.S. Department of Energy, we derive over 70% of our electricity from fossil fuels, the bulk of which comes from coal. [2] Based on the same statistics, we currently derive only about 10% of domestic electricity production from renewable sources. Assuming no net increase in nuclear power, which accounts for the remaining 20% (and environmental activists hate nuclear power almost as much as fossil fuels), we would need to increase renewable energy production by 7 times to meet the demand that is currently satisfied by fossil fuel energy. I suspect that the 50 billion USD provided for energy investment in the American Recovery and Reinvestment Act of 2009 (i.e. the Stimulus Bill!) [3] isn’t enough to make even a small dent in that figure.

Note also that I have not even touched on the issue of biofuels or hydrogen; I will do so in a post immediately following this one, the reason being that most of these cannot easily be used for electricity production. Biofuels and hydrogen are generally being considered as potential replacements for our nation’s petroleum fuel needs, but the vast majority of these fuels are not used to produce electricity, but to fuel cars, trains, and aircraft. [4] All of these fuels also require energy input to create them, so this energy needs to come from somewhere else, i.e. the national power grid.

An interesting tangential thought to these considerations is how much energy gets lost in transition across the national power grid. The vast majority of our electricity distribution takes place across conductive wires, but anyone familiar with high school physics will recall that even conductive materials have some resistance to energy transfer, i.e. some of the energy gets lost while travelling through the conductor. Even if this figure is a small percentage of the total amount (i.e. the efficiency of the system is high), given the enormous scale of the national power grid, the amount lost may be a non-trivial amount. I can’t find statistics on this, however, so its only speculative for now. I also have no idea what else we might be able to use as an alternative, though microwave tranmission through vacuum-enclosed tubes comes to mind (huge infrastructure costs, though…)

Notes:

[1]: Information from the U.S. Department of Energy: http://www1.eere.energy.gov/solar/myths.html

[2]: Statistics from the Energy Information Administration (EIA): http://www.eia.doe.gov/cneaf/electricity/epa/epates.html

[3]: ENORMOUS PDF WARNING! (also note that the PDF does not contain bookmarks – and its 407 pages long…no wonder nobody read the damn thing before signing it!): http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=111_cong_bills&docid=f:h1enr.pdf

[4]: Statistics from the Energy Information Administration (EIA): http://tonto.eia.doe.gov/dnav/pet/pet_cons_psup_dc_nus_mbbl_m.htm

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One Response to “What can “Green” energy do for us?”

  1. MI Says:

    1. Power line resistance amounted to 7.2% in 1995; see:

    climatetechnology.gov/library/2003/tech-options/tech-options-1-3-2.pdf

    2. Geothermal: while the western US is better for geothermal power plants, heat pumps are usable anywhere. See:

    theoildrum.com/node/3661.

    Depletion of wells is also a problem with hot dry rock, IIRC.

    3. Re. the usability of wind, see:

    ergosphere.blogspot.com/2005/03/forty-two.html (supplemental power)

    environment.independent.co.uk/climate_change/article3194088.ece (baseline power)

    4. Even assuming, arguendo, that solar is indeed limited to the western US by insolation, methinks we have sufficient unused land out there to generate sufficient power. With US energy consumption = ~100 EJ, insolation of 237 W/m2 for 8 hrs/day, & PV efficiency of 10%, we’d need ~155k mi2, or a little over two thirds the area of Arizona & New Mexico.

    5. You didn’t mention OTEC; however, AFAIK, US utilization thereof would largely be limited to Hawaii.

    6. WRT wind & solar (IMHO the most promising renewables), another drawback is intermittency (resulting in variable power output – not good for baseline power). This can be gotten around with sufficient quantities of batteries, or other electricity storage means (e.g., compressed air, pumped hydro). Cost is another issue, but I suspect it will continue to decrease over time for both wind & solar (between continued R&D & improved manufacturing processes).

    7. Re. subsidies, my preference remains tariffs on imported energy sources, and letting the domestic free market figure out the appropriate balance between substitution of new energy sources, & conservation of existing ones.


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