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CIESINReproduced with permission, from: Edmonds, J.A., M.A. Wise, and C.N. MacCracken. 1994. Advanced Energy Technologies and Climate Change: An Analysis Using the Global Change Assess ment Model (GCAM). Pacific Northwest Laboratory, Richland, Washington.


Defining Five Advanced Energy Technology Cases

To examine the potential of advanced energy technologies to reduce greenhouse related emissions, we have constructed five alternative scenarios each of which adopts the same assumptions as those used in the reference scenario (closely following IS92a), with the exception of the assumed wide availability of additional energy supply and transformation technologies. While these technologies are assumed to be widely available, they must compete in the marketplace against other fuel prod uction technologies, including both conventional and other advanced technologies.

Case 1. Reference Case (IS92a (ERB)): Developed to be consistent with IS92a.

Case 2. Advanced Fossil Fuel Technologies (Adv FF): The efficiency of fossil fuel powered electric-generation technologies are assumed to reach 66 percent by the year 2095. Other assumptions are the same as for Case 1.

Case 3. Advanced Liquefied Hydrogen Fuel Cells (Adv FF, LH2): Hydrogen fuel cells are used to power transportation. Hydrogen is available from natural gas, biomass and electrolysis at the following costs:

	Natural Gas Steam Reforming: 		$1.71 + Pgas/0.901
	Biomass BCL Gasifier: 			$4.83 + Pbiomass/0.784
	Electrolysis: $2.36 + Pelec/0.900

Costs from Williams 1994a.

Hydrogen is assumed to be liquefied and used in fuel cells on board vehicles. Associated costs are as follows:

	Liquefaction: 				$3.90/ GJ;
	Fuel Storage: 				$1.16/ GJ;
	Fuel Cell lifecycle capital cost:	$138/GJ.

The cost of liquefying, transporting, and operating fuel cells from Rogner.(b)

The cost of Solar/wind power reaches a busbar cost of $0.04/kWh by 2020 and the cost decreases at 0.5 percent/year thereafter, Williams 1994b.

Other assumptions are the same as for Case 2.

Case 4. Advanced Hydrogen Fuel Cells (Adv FF, H2): Assumptions are the same as in Case 3, except that there are no costs of liquefying hydrogen, and no additional costs for vehicles or infrastructure.

Case 5. Low Cost Biomass (Low Bio Cost): Same as Case 4 except that biomass costs are reduced. By the year 2020, 20 percent of the biomass resource is available at $1.40/EJ, and 80 percent is available at $2.40/EJ, Williams (1994a).

Case 6. Accelerated Rate of Exogenous End-use Energy Intensity Improvement (3E21): Same as Case 5 except that it assumes that the exogenous end-use energy intensity improvement rate reaches 2.0 percent/year by 2050.

Click for Table 2.

The Effects of Advanced Energy Technologies on Energy Use and Emissions

Figure 5 and Figure 6 show emissions and total primary energy trajectories associated with each of the six cases outlined above. Both energy and emissions are reduced by the introduction of a dvanced fossil fuel combustion technologies, Case 2. Interestingly, the effect of these technologies on total primary energy use is greater than the effect on fossil fuel carton emissions. The differential effect, of between two and five percent, is due a t least in part to the "take back" effect of lower electricity prices associated with the advanced energy technologies. Note that this effect is of second order, modifying emissions reductions. but never reversing the direction of the change in emissions reductions.

The introduction of advanced transportation technologies, Cases 3 and 4, significantly reduced fossil fuel C02 emissions. Reductions become increasingly important after the year 2005. While the lower cost, non-cryogenic hydrogen fuel cell technology has lower emissions in addition to lower cost, the incremental impact on emissions is not as great as that obtained from the introduction of hydrogen fuel cell vehicles; that is the difference between Case 2 and Case 3. The effect of advanced transportation technologies on energy is less pronounced than on fossil fuel carbon emissions. For example, cryogenic hydrogen technology reduces fossil fuel carbon emissions by more than 25 percent on the year 2095, yet total primary energy use increases by only 1 perc ent. The non-cryogenic technology case, Case 4, lowers energy use, but never by more than 10 percent relative to the advanced fossil fuel case, Case 2. This contrasts sharply with the 20 to 30 percent reductions in fossil fuel carbon emissions between Cas es 2 and 4.

The most important feature of Case 5 is the introduction of significantly lower biomass energy costs. The appearance of this technology has a moderate impact on global primary energy use, reducing it 10 percent in the year 2095 relative to Case 4, though there is no noticeable effect prior to 2060. The effect on global fossil fuel emissions is dramatic, however. The low cost biomass fuel quickly drives coal from the market shortly after the turn of the next century. Contrast Figures 3 and 7 which show Ca ses 1 and 5 respectively.

Case 6 differs from Case 5 only in the fact that the rate of exogenous energy intensity improvement has been raised to 2 percent/year. From the perspective of fossil fuel CO2 emissions, there is some additional reduction in fossil fuel emissions over Case 5, but that difference is trivial by the year 2095. The effect on energy use is dramatically different. The impact of the increased rate of exogenous end-use energy intensity improvement is to lower energy use by 44 percent by the year 2095 relative to C ase 5. As a consequence, biomass energy production declines from 420 EJ in the year 2095 in Case 5 to 250 EJ in Case 6.

Click for Figure 7.

Comparison to Results of the LEESS Scenario

The low CO2 Emitting Energy Supply Systems (LEESS) scenario developed for the IPCC WGII (Johansson et. al., 1993) uses the same set of assumptions about the costs of advanced energy technologies, as those adopted in Case 6. The LEESS is a "bottom-up" sce nario based on engineering estimates of the future costs of advanced low-carbon energy supply, while the results developed here employ a classical "top-down" model. Nevertheless, both scenarios give similar results.

Figures 8 and 9 compare the LEESS scenario to Cases 1-6 with respect to global fossil fuel carbon emissions and energy production. From Figure 8, the LEESS emissions are not substantially different from Cases 5 and 6. In Figure 9, global energy supply in the LEESS scenario is less than Case 5: however, Case 6 actually has a slightly lower energy supply total than LEESS by the end of the next century. These figures demonstrate that the "top-do wn" and "bottom-up" approaches do not produce inconsistent results when given common assumptions. This suggests that differences in results between the two approaches are not primarily due to methodological differences but instead caused by differences i n assumptions about the economic costs and availability of technologies.

The Value of Advanced Energy Technologies in Stabilizing Future Fossil Fuel CO2 Emissions

One way to consider the climate-related value of advanced energy technologies is to examine their effect on the cost of achieving some climate-related goal. We have arbitrarily chosen as a reference goal the stabilization of fossil fuel CO2 emissions as a target. The tax rate (assumed to be applied globally), or marginal cost of stabilizing fossil fuel carbon emissions for Case 1, is shown in Figure 10. These rates are equivalent to the market values of tradable permits.

Costs of stabilizing fossil fuel CO2 emissions are computed using the consumer plus producer surplus method described in Edmonds and Barns (1992). Note that costs reflect only those associated with fossil fuel carbon emissions reductions, and make no atte mpt to include value for other greenhouse related gaseous emissions. The cost of global emissions reductions grow from approximately $35 billion per year in 2005 to $1387 billion per year in 2095. At the same, time global GNP grows from an estimate $20 t rillion in 1990 to $230 trillion in 2095. To compute a present value, we have discounted costs at 5 percent per year. Summing discounted costs and comparing these to the sum of present discounted GNP yields a present discounted burden of 0.22 percent for Case 1.

The incremental value of adding each bundle of technologies to Case 1 is given in Table 3. The total value of the technologies increases steadily, indicating that each reduces emissions. The second column is computed by looking at the difference between individual cases and can be interpreted as the incremental value in terms of stabilizing emissions of the next component to the bundle. It is important not to make too much of this number, because component values are not independent of the order of computation. That is, the incremental value of advanced fossil fuel technologies might be very different if it were the last item added to the bundle rather than the first. And one would expect that diminishing returns to addi ng emissions reducing technologies would apply in this case.

Quite clearly, great value is gained by adding low cost biomass to the bundle. Even with advanced fossil fuels, low cost solar electric power, and low cost fuel cell vehicles, the present discounted value of adding this technology is still almost half a trillion dollars. The present discounted value of the advanced energy technologies embodied in Cases 1-5 is $1.8 trillion.

(a) Solar electricity is a general category which includes technologies all non-carbon emitting electricity technologies other than nuclear, hydro, and biomass. Thus fusion, wind, geothermal, and OTEC are included in addition to photovoltaic an d power tower technologies.

(b)Personal communication. 1994.


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This work, including access to the data and technical assistance, is provided by CIESIN, with funding from the National Aeronautics and Space Administration under Contract NAS5-32632 for the Development and Operation of the Socioeconomic Data and Applications Center (SEDAC).

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