2

The energy system, like many other sectors of society, has a high inertia and we must reckon with decades for major changes to be made. The rather small hope of maintaining the world oil production means that one such major change is just around the corner. The alternatives that seem to exist for the next few decades must be analysed in an impartial manner. Only in this way can the interaction between these future alternatives and different interests in society be brought to light in time and give results in the long range measures that can be taken now. Such measures can be pure matters of energy policy, as e.g. the direction of research, development and demonstration or measures to influence energy use. They can also be measures that e.g. influence the long term development of production and consumption.

This report is structured in the following way. The rest of the introduction gives a short background to our present energy situation. In chapter 2 the energy flows deriving from the sun are dealt with in a summary fashion. The present state of the art for a number of renewable energy sources is also dealt with. The following chapter sketches a possible development of society, which is the background against which the energy system should be seen. Chapter 4 discusses the components of a renewable energy system for the early part of the 21st century. Environmental problems and safety aspects are dealt with in chapter 5. The introduction of such an energy system is discussed with respect to economy in chapter 6 and with respect to conflicting interests during a transition period in chapter 7. Chapter 8 is a summary of the discussion.

Sweden ́s energy supply is based on oil and gas as is that of the rest of the industrialized world. World oil resources are such that we can expect stagnation and later decline in production. The situation with respect to natural gas is similar. For resource reasons it is probable that the production of conventional oil and gas will stagnate during the next decades. Political and/or economic factors can move this point in time closer (2).

Petroleum will largely have to be substituted within a relatively short period of time. This means that the world is facing a major change. The quantities of energy used at present are very large and the energy conversion systems that have been built up are designed for oil and gas.

The main alternatives to substitute petroleum at first gradually and later completely as a base for the world energy supply are coal, uranium/tnorium in breeder reactors or renewable energy sources. These alternatives have different characteristics in a number of respects. In all there are great but different uncertainties inherent. These have been discussed more fully in a previous report (1).

1.2.2

Uncertainties concerning future alternatives

The uncertainties inherent in basing the world energy supply on
coal are primarily concerned with the effects on the environment
of coal use. Major climatic changes within the next decades are
among the possible effects of emissions of carbon dioxide (3).
Large scale coal use also results in releases of large amounts of
poisonous heavy metals. Mercury and cadmium seem to be the two
most problematic and very large cleaning and disposal problems
can be foreseen if these effects of large scale coal use are to

be mastered. Furthermore, there are great problems with emissions of sulphur and a number of other substances (85).

With large scale use of nuclear power other major uncertainties follow. On a purely technical level it is uncertain whether the breeder technology complete with reprocessing, which is necessary if nuclear power is to have a future, can be developed into a functioning, large scale system without jeopardizing several aspects of safety. Breeder reactors use uranium and thorium very much more efficiently than present light water reactors and thus remove the limits to the development of the nuclear energy supply system now set by uranium reserves (4). It is also unclear if such a system could be developed and built quickly enough to replace oil in the global perspective. Furthermore, there are uncertainties concerning the risk for nuclear proliferation and terrorism.

The underlying problems are so complex that we cannot count on knowing significantly more in, say,some decades. We must count on having to make decisions in spite of remaining uncertainties in fundamentally important questions. This fundamental uncertainty can have implications both for shaping energy policy and for the decision-making process as such (5).

This makes it interesting to investigate if there are possible and feasible methods for the world to solve its energy supply problems without using either very much coal or very much nuclear power in the long run. The renewable energy sources could provide such an alternative. We will here try to analyse the possibilities for and the conditions under which the energy supply planning could be geared to substituting oil with renewable energy sources .

5

1.3

What do we mean by solar energy in Solar Sweden?

With solar energy we mean all energy forms that reasonably directly can be derived from the sun. We include direct solar radiation, wind and wave power, both of which are caused by solar radiation, hydro power, which uses part of the hydrological cycle powered by the sun etc. Tidal power, which is of no significance in Sweden, would logically not be included since it derives from the interaction between the gravity of the earth and the moon. Neither would geothermal energy, since it derives from radioactive decay within the earth Geothermal power has probably only limited and local importance in Sweden within the foreseeable future. We do not include oil, natural gas or coal, although they have been formed by organic substances built up by photosynthesis. These sources are excluded since they must be considered non-renewable due to their extremely slow time of formation. The same is true for peat, of which we have rather large quantities in Sweden. Peat is thus not included in our energy system. It could, however, very well be important in the transition between energy systems based on oil and solar energy. One reason for this is that the areas where peat has been extracted seem to be suitable for energy plantations. Development of a system for handling and processing peat seems to be a suitable precursor for later development of systems handling biomass.

In this section we give the background which shows why a Swedish energy system could be based completely on renewable energy sources.

The Earth receives a constant flow of energy from the Sun. This flow keeps the temperature of the Earth above that of the cold space, drives currents in the atmosphere and the oceans, drives the hydrological cycle and powers the photosynthesis of the green plants. Figure 2.1 illustrates these energy flows on Earth. It also shows the energy turn-over of human society. The global energy flows have been expressed as multiples of the amount of energy used by human society. For example, the photosynthesis of the green plant fixes a quantity of energy, which is eight times that used by human society. The amount of energy reaching the Earth from the Sun is 30,000 times that used by human society etc. The energy used by human society is derived primarily from fossil fuel, firewood and food. Fossil fuels, which are formed at a negligible rate by anaerobic decomposition processes, dominate human energy supplies on a global level. Together they make up for approximately 85 %.

Thus we utilize both natural energy flows and those made by man in the industrilized system. The natural system is much larger but some of its characteristics are such that it does not fit in very well into the present pattern of energy use. The man-made energy flows are much smaller, but have developed together with the systems of utilization. They thus fit well together today. If we can use the natural energy flows in some ingenious way for what we consider necessary energy use, the quantities of energy available do not constitute a problem. The figure shows that the flows are sufficiently large. Against this general background we would like to point out three, as we think important, dichotomies: