63 If the goals set up in the US can be reached a large market ERDA is backing fuel cells and the immediate goal is to connect The uncertainties in the example presented here are naturally In our example we have chosen a level of supply of 568 TWh. In the government bill energy conservation etc 1975 it is stated that we must seriously examine the possibility of keeping energy consumption at an unchanged level as of 1990. The National Industrial Board in their latest prognosis (SIND 1977:9) indicate an estimated total supply of approximately 500 TWh in their conservation alternative. Other uncertainties naturally occur in the assumed production of goods and services both with regards to volume and kind. Even rather small changes of this have noticeable effects on the total level. If we for example assume a total supply of 70 TWh below that used 64-65 Such a reduction in the area needed would naturally considerably reduce the conflict over land use. The need for land is also influenced by the yield. If we assume this to be 120 MWh ha instead of 90 MWh ha we find that at the reduced energy supply level of approximately 500 TWh the need for space is reduced to 1.6 Mha. If at the same level of energy supply we assume that the productivity is reduced from 90 70 MWh per ha the necessary area increases to 2.7 Mha instead. Another factor which can considerably influence the need for space for energy plantations is the development of marine culture of biomass. In our example we assumed a supply of 20 TWh from marine culture. Available water areas in Sweden are considerable. This means that fresh water and aquatic culture is of considerable interest. There are possibilities of more efficient utilization of the biomass from agriculture and forestry. We have included 30 TWh but at least the double is possible to collect presuming that it is done with suitable technology. The fear that windpower stations will constitute visual pollution seems to be smali in Denmark (84). If this turns out to be true in Sweden also there is a potential to increase energy production from windpower several-fold compared to the 30 TWh we have included. Another uncertainty lies in the conversion efficiency from biomass to metahnol or electricity and the possibilities for utilizing residual heat. The figures we here use exceed what is reached today. We do however believe that there is reason to look optimistically at the development of renewable energy sources. In many cases such technology only constitutes modification of existing. It should be observed that it was not until the oil crisis 1973 - 74 that interest in these alternative technologies increased. Previously there was only limited interest in e.g. methanol production from biomass or utilizing the residual heat from industrial processes etc. 66 5. ENVIRONMENTAL EFFECTS AND SAFETY IN A RENEWABLE ENERGY SYSTEM One of the major arguments for a Solar Sweden is its probably very favourable characteristics from the point of view of environment protection and safety. Another is the self-sufficiency - no energy is imported. Energy production in Solar Sweden rests on deflecting natural energy flows and can thus be expected to have limited environmental impacts. However, the technologies and systems described in chapter 4 are in many details still under development and it is difficult to make precise projections of their environmental impacts. It is quite clear that it is possible, by short-sighted or careless design of individual components of the system, to create severe risks for the environment e.g. by choice of toxic metals such as cadmium for solar cells with concomitant risks for further contamination with this metal during extraction, handling and waste disposal. The energy conversion methods that we have used are relatively advantageous. Emissions from cars will be considerably reduced. This is of the utmost importance since emission from cars is our greatest air pollution problem in urban areas at present. The low levels depend on the use of fuel cells, which are very clean. By choosing fuel cells powered by methanol a smooth transition from present engines can be achieved as discussed earlier in the context of methanol used in conventional engines (section 4.6). Using methanol as an additive to petrol means that the lead is no longer needed and other emissions can be reduced. This is of great importance and can be quickly carried out. Fuel cells are also used in industry for production of electricity and heat. They give rise to low levels of emissions, lower than at direct combustion of biomass, which has also been included in 54-948 0 - 80 - 53 67 the system. In spite of small emissions of sulphur direct combustion of biomass may need flue gas cleaning. Nitrous oxides and probably polycyclic hydrocarbons are formed in such quantities that this is probably necessary (85). Biomass contains only small amounts of sulphur. Emissions of sulphur will therefore go down. A large proportion of the acid rain in Sweden is caused by emissions in Europe and we can therefore not expect a drastic improvment of the acid problem in Swedish waters by domestic reductions of sulphur emissions. Large amounts of carbon dioxide are formed during combustion of biomass. This, however, is no environmental problem since carbon dioxide is fixed from the atmosphere via photosynthesis when the biomass grows. There is thus a balance between the release and uptake of carbon dioxide in the system. From the environmental point of view the production of biomass is of particular interest since it has a dominating place in our energy supply. Energy plantations on land is the major proportion of the biomass component. Several problems exist in connection with growing biomass over large areas (85, 86). The plantations such as they are now conceived must be heavily fertilized, particularly with nitrogen. The plantations can be damaged by game animals, rodents, fungi and insects. The extent of damage is difficult to assess since there is a lack of wider experience. Ecologically acceptable counter measures exist, but their efficiency is difficult to estimate. It is therefore possible that a lower productivity can result due to these problems. To a certain degree this can probably be contained already within the conservative estimates that we have used in our 68 calculations. If not, it would lead to a need for larger areas to reach the production volume used here. The damage caused by game animals can probably be controlled by intensified hunting. Energy plantations would then be a positive factor. The rodent problem is more difficult to assess both from the point of view of yield and methods of combatting it. Fungal infections can perhaps be met by breeding for increased resistance as has been done in agriculture. Damage from insects can perhaps be met with ecological management of the plantations, primarily by having mixed stands with respect to both species composition and age structure. If at the same time species that can fix atmospheric nitrogen such as alder (Alnus) could be used. This would reduce the risks for nitrogen contamination of ground water. The nitrogen problem is important because of the strong indication that exist for a connection between various types of cancer and exposure to certain nitrogen compounds. The losses of nitrogen to the stratosphere (in the form of N20) are also important. These losses are proportional to the concentration in the soil. It should be possible to reduce the losses by giving the nitrogen fertilizer in small amounts several times during the growing season. It should, however, be stressed that considerable work on research and development is done to avoid such problems. There is reason to hope for favourable result of this work. One can assume that large scale development of any system is precluded if environmental effects are not under control. It should be noted that certain problems, e.g. large scale insect problems, probably will not occur until a large system has been created (86). The systems must thus be planned so that a situation does not arise where chemical pest control is considered the only alternative for coping with a problem. A far-sighted planning is thus necessary and should give good results. |