In section 6.2.2, a demand scenario was developed for the year 2050, and in sections 6.2.4 to 6.2.7 estimates were made of potential energy utilisation from the most important renewable energy sources, for the same period of time. Resources were divided into those suited for decentralised and centralised supply, both on a geographical basis. Estimates of additional renewable inputs, such as hydro power and geothermal energy, exist and can be added (S0rensen and Meibom, 1998; 2000).
The next task is to match supply and demand, adding new system components as necessary, e.g. when the energy form supplied is not that demanded, and pointing out requirements for energy imports and exports between regions when the location of supply and of demand is not the same. In practice the form of transport will depend on the type of energy (electricity transmission, gas piping, heat in district lines, or fuels to be moved, e.g. by vehicle or ship). Also temporal mismatch can be identified, and energy storage requirements determined. In most of the cases considered, some storage cycle losses were already incorporated into the supply estimates, notably for those renewable energy sources where the source variability already indicated a storage need. The supply-demand matching is now made, first by using only those amounts of renewable energy that are estimated to be available locally, in a decentralised form, and subsequently, the possible advantages of also including centralised production are investigated.
In going from Table 6.2 to Table 6.5, the demand categories were already simplified under the assumption of an abundant fraction of the supply being in the form of electric energy. What remains now is to determine the sources of supply for each demand type.
For the vegetable food-fraction, the results of comparing local supply and demand are shown in Fig. 6.78, where Fig. 6.78a shows the amount of surplus for those geographical grid cells where supply exceeds demand, and Fig. 6.78b shows the amount of deficit for those local cells where demand exceeds supply. Regional sums are given in Table 6.9. It follows that on average, worldwide supply exceeds demand by 35%. This must be considered reasonable, as there has to be room for variations in crop harvests and thus food production from year to year, and further the transportation required for evening out supply and demand will entail some additional losses.
Like today, there is surplus vegetable food production in the Americas and Western Europe (regions 1, 2 and 4, cf. Table 6.5), and by year 2050 also in region 3 (including Russia), owing to substantial improvements in agricultural practices assumed for this region. Region 5 (including China and India) will be just self-sufficient by year 2050, whereas Africa (region 6) will have a deficit that must be covered by imports. In the scenario, Africa is the only region that by 2050 is in a development situation where it may offer labour at lower expense that the other regions, and thus there will be the possibility of paying for food imports by industrial revenues, provided that an education policy is pursued, that will give the working force the necessary skills. In addition to inter-regional exchange, Upon closer inspection, Fig. 6.78 indicates scenario requirements for transport of vegetable food within regions, especially from farming areas into cities.
The scenario assumptions for inter-regional trade in food are indicated in Fig. 6.83, where the regional exports have been selected from the surpluses available. The substantial needs for both vegetable and animal foods in Africa are uniformly imported from regions 1-4.
For animal-based food from either rangeland or fodder-fed animals, the surpluses and deficits are shown in Fig. 6.79. The picture is similar to that of vegetable foods, with surpluses in the region 1-4, but here with deficits in region 5 and 6. This is due to the increase in the meat and milk fractions of diets assumed for Asia Table 6.5), but the amounts are easily covered by imports from other regions, as indicated in Fig. 6.82. Overall, the animal food supply exceeds demand by 27%, which again is considered adequate in view of additional losses. Variations between years are smaller than for primary crops (because of the storage functions performed by livestock), but fairly frequent epidemics of animal disease are known to require a reserve.
Figure 6.80 shows the surplus and deficit of potential liquid biofuels derived from agriculture and silviculture, relative to the energy demand for transportation. The assumed fraction of biofuels used in this way is 48.5% (chosen such that the global average demand is covered), the remaining is considered going into industrial uses such as medium-temperature process heat, where it is assumed used with 90% efficiency.
When constructing the demand scenario, we left it open to what extent electric vehicles would be used, but the availability of liquid biofuels is such
Figure 6.78. Local surplus (a: above, scale left, annual average supply minus demand in Wm 2 is shown if positive) and deficit (b: below, scale right, annual average demand minus supply is shown if positive) of vegetable-based food supply relative to demand, on an area basis, valid for both decentralised and centralised 2050 scenario (this and following Figures from S0rensen and Meibom, 1998).
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