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The following is a simple analysis of the potential options for reducing US greenhouse gases over the next 25 years.
Total energy needs projected growth for US:
The eia (energy information administration) projects a 32% increase in energy needs by 2030.
32% growth [1]
Conservation:
In 1975 the average projection of the total energy needs in 2000 were about a 100% over 1975 usage [2]. The actual increase was about 50% [2]. If we assume that the conservation effort following the oil embargo was the principal driver, this suggests that conservation could essentially reduce the growth in energy demand by about 50%. Thus, half of a 32% growth = 16%. If an all-out intense program of conservation measures is used, a highly optimistic assumption is that conservation will negate growth (i.e., 32% effect).
• Likely: –16% (Using average 1975 projections as a model)
• Max: –32% (Optimistic estimate)
Electrical energy projection for US:
The installed electrical capacity 2005 was about 1000 GWe [3]. In 25 years, installed capacity is expected to be about 1380 GWe [3]. Using conservation 50% reduction in electrical energy growth gives 500/2 =190 . Thus, 1000 + 190 = 1190 GWe in 25 years. For extreme conservation efforts it is assumed that electrical energy needs will be held at 1000 GWe.
• Likely: +39% 1190 GWe [3]
• Max: 0% 1000 GWe (Optimistic estimate)
Wind power:
In 2006, wind power contributed about 0.4% of US electricity, and the eia projects an increase to only 0.9% by 2030 [4]. Very optimistic projections of an ultimate wind power contribution give 20% of electrical power (190 GWe). For wind farms, 1 GWe requires 200 km2 x (.621)2 = 77 miles2 [5]. Thus, for 20% contribution, 190 x 77 = 14,630 miles2 required; i.e., about 2 times the size of NJ. This is a very massive development and an unrealistic goal for 25 years. A highly optimistic projection for 25 years is 5% (wind farms about half the size of NJ). Power stations produce about 20% of the GHGs; thus, the max estimate for wind power to reduce GHGs is about 5% x 0.2 = 1% of US GHGs. More likely, wind power will contribute less than 2%, or a GHG reduction of about 0.04%.
• Likely: –0.4% (twice eia)
• Max: –1% (Optimistic estimate)
Nuclear power:
Currently, nuclear power produces about 19% of US electrical energy [4]. The eia [1] projects a 112.6 GWe growth in nuclear electrical power by 2030, which would require about 100 new plants. This growth implies general acceptance of nuclear power and rapidly expanded capable work force. Using 112.6/1000 = 11.3, or an 11.3% added electrical power from new nuclear plants. 20% of GHGs from power stations gives 11.3% x 0.2 = 2.26%; i.e., about a 2% reduction in GHGs. This does not sound realistic and probably is just a reflection of the current administration plans. A more likely scenario is a 1% reduction in GHGs.
• Likely: –1% (more likely, given constraints)
• Max: –2% (eia projection)
Coal:
Coal currently provides half of all US electrical power. Current plans for the next 5 years is to add almost 38 GWe to US grid [6]. Over 25 years this rate would provide about 190 GWe. Here we will assume that about half of the new electrical power for the most likely case (half of 190 GWe = 95 GWe) will be provided by coal. The issue, however, is how many of the coal-fired plants, if any, will be able to sequester CO2. Thus, the reduction in GHGs can range from no sequestering (adding) GHGs to 100% sequestering. New coal fired plants would contribute 10% of electrical power in 25 years, with a range from about +4% (increase) to about –4% (decrease) in GHGs. The most likely situation might be some plants built without sequestering, some plants not built, and some built with sequestering, resulting in a net effect of about 0. The maximum GHG reduction would be about –4%, although this would require back-fitting sequestering to plants now started (feasible?).
• Likely: ~0% (mix of plants)
• Max: –4% (sequester successful)
Biomass:
In 2005, biomass produced about 1% of US electricity [4]. Eia projects about 100 GWe from biomass, yielding about a 1.8% GHG reduction [4]. For transportation, the eia projects as much 8% of the energy for the transportation sector will be provided by ethanol by 2030 [1]. If corn ethanol is used the net energy savings is only 1/3 of this amount. Assume that most is from cellulous biomass and that the energy required for production of cellulous ethanol is small (all 8% is achieved). About 14% of GHGs come from the transportation sector. Thus, the reduction is about 8% x 0.14 = 1.1%, making the total (electricity plus transportation) of 2.8% or about 3%. These numbers sound somewhat optimistic; nonetheless, I will use them as the likely case. With a major effort, perhaps these numbers could be increased to 5%.
• Likely: –3% (using eia data)
• Max: –5% (Optimistic estimate)
Solar:
Solar photovoltaic (PV) is very expensive and currently supplies only about 0.04% of the US electrical energy [8]. It is unlikely to be economical even with carbon taxes. Optimistically, perhaps specialty needs (remote locations), demonstrator installations, and ecology-minded individuals could increase the PV contribution in 25 years to 0.4%, an increase of 10 times. The GHG reduction is 20% of this, or 0.08%. Concentrated solar has been developed and tested; however, it has not been demonstrated to be economical. Solar passive heating would almost entirely apply to new construction. If we assume about 5% of all homes in 25 years will be new construction, and 25% are located in regions where solar heating is practical, and 50% of these homes and buildings use passive solar heating, the number of homes and buildings with passive heating is about 5% x 0.25 x 0.5 = 0.0625%. This also assumes that no backup heat system is used. Residential and commercial buildings contribute about 10% of GHGs. Thus, the passive solar heating reduction in GHGs would be ~0.005%, and the net solar GHG effect is about 0.08%. Although this sounds optimistic, solar has a wide appeal in some sectors and is showing rapid growth, despite the costs. I will assume a GHG reduction of 0.05% for the likely case, and for the optimistic case I will use a GHG reduction of about 0.1%.
• Likely: –0.05% (assuming rapid growth, tempered by cost)
• Max: –0.10% (Optimistic estimate)
Geothermal:
Currently, geothermal produces about 0.4% of US electricity. An MIT study predicts that within 50 years about 100 GWe can be obtained affordably from geothermal [7]. The eia [4] points out that there are limited sites for expnding geothermal and does not project much growth. Here, we assume a contribution between the eia and the MIT assessments. Optimistically, we assume that within 25 years, we could produce 25 GWe using geothermal (~2.5%). Thus, using the usual process, geothermal GHG reduction is about 0.5%. Perhaps half that amount is more realistic (0.25% GHG reduction); because the ability to field practical geothermal may take some time.
• Likely: –0.25% (eia and MIT data considered)
• Max –0.5% (using eia and MIT data, optimistic)
Hydropower:
Hydropower accounts for almost all of the 8.8% renewable contribution to the US electrical power supply. In the US, no more attractive hydropower sites are available and hydropower is recognized as a major environmental threat. Additional GHG reduction from hydropower in 25 years = 0.
• Max 0%
Wave/tidal:
None producing power in US, and the predicted benefit in 25 years will to be very small.
Agricultural shift:
Move away from energy intensive agricultural practices and methane-producing crops and cattle. Difficult cultural and infrastructure shift. Even if a 10% effect in 25 years, agriculture only contributes about 12% to GHGs. Thus, estimate about a 1% effect, at most a 2% effect.
• Likely: –1% (optimistic guess)
• Max: –2% (optimistic guess)
References:
1. Energy Information Administration Reference Case Projections, International Energy Outlook 2007 PDF .
2. Chen, A, What can history teach us about forecasts of energy use?, Lawrence Berkley Laboratory, Dec. 17, 2002.
3. Energy Information Administration Forcasts and Analysis.
4. Energy Information Administration Annual Energy Outlook 2007 with Projections to 2030.
5. National Renewable Energy Laboratory, Power Technologies Energy Data Book, accessed June 1, 2007.
6. Clayton, M, New coal plants bury 'Kyoto' Christian Science Monitor, Dec.23, 2004.
7. MIT The future of geothermal energy, 2006.
8. Energy Information Administration U.S. Electric Net Summer Capacity
9. Energy Information Administration Electricity Demand and Supply.
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http://zfacts.com/p/834.html | 01/18/12 07:23 GMT
Modified: Sun, 01 Feb 2009 22:26:51 GMT
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