12

The costs of producing biomass have been estimated in several studies. Ordinary wood for use in pulp industry costs approximately 300 - 320 Sw. Crs/ton dry matter delivered to a point accessible by truck (13). This is equivalent to 0.06 Sw. Crs./kWht if the wood is burnt*. For energy plantations different sources give the following values:

a) 100 Sw. Crs/ton DM: 0.02 Sw. Crs/kWht (14)

b)

150 Sw. Crs/ton DM: 0.03 Sw. Crs/kWht (15)

c) 0.02 -0.033 Sw. Crs/kWh at a production of 67-175 MWh/ha (16). d) 0.01 0.02 Sw. Crs/kWht (17)

These figures should be used with great caution since the methods for calculating the costs are not completely known. For comparison ... the price of fuel oil is 0.05 - 0.06 Sw. Crs/kWh in Sweden.

Biomass can be used as a raw material in chemical industry in the same way as oil. One difference however is that the technology for utilizing biomass is today not as well developed as for oil. After gasification various chemical components can be produced e.g. methanol, ammonia.

Biomass can be converted with the aid of bacteria so called anaerobic fermentation, i.e. bacterial decomposition in the absence of oxygen. The technology is not yet fully developed (19).

When biomass (firewood) is burnt carbon dioxide is formed. The amounts formed are equivalent to what was taken up from the atmosphere during photosynthesis when the biomass grew. Combustion of biomass thus does not entail any long term build-up of atmospheric carbon dioxide as is the case with combustion of fossil fuels.

*kWht is kilowatthours of thermal energy

13

The basic principles for power generation from the wind are well known since decades (26) and several million windmills have been used previously. When oil became a cheap source of power the windmills became uneconomical. Except for the last few years no development with modern technology has taken place. Sweden is situated in the so called belt of westerly winds and has good wind conditions. The energy yield from a windmill is approximately equivalent to 2,000 hours (1,700 - 2,500 hours depending on locality etc.) production at maximum power (rated power) for the generator. At present the major development effort is directed towards electricityproducing windmills with a horizontal propeller axis.

A number of prototypes are under construction or testing. Thus all figures for cost of mass-produced windmills today are estimates. Prototypes today cost in the order of 10,000 Sw. Crs per kW rated power (Crs/kW). It is estimated that mass-production will reduce costs considerably. Two planned prototypes in Sweden in the MW-size are costed at respectively 3,400 Sw. Crs/kW (25) and 3,600 4,500 Sw. Crs/kW (SAAB-SCANIA) (25). The Swedish Council for Energy Production Research estimates that the cost for electricity will be 0.14 0.23 Sw. Crs/kWh (25).

Attempts have been made to estimate the decrease in cost through build-up of experience after 100 plants have been constructed. One study points at costs in the interval of 2,000 - 4,500 Sw. Crs/kW (27). Large windmills (megawatt-size) have the advantage of being able to utilize the higher wind speeds at greater height by being placed on high towers. The cost per kWh has been claimed to be lower for large mills than for small. This view has been questioned recently since smaller mills (8 - 40 kW) have a size suitable for industrial massproduction. This would make cost reductions possible. ERDA has set the equivalent of 2,500 Sw. Crs/kW for 40 kW plants at a production of 1,000 units as its goal (27).

14

A further reason why cost reductions are possible is that only
10 - 20% of the costs today are for materials. On top of the costs
for the mill itself, are other costs for plannning and execution.
These are construction works (roads etc), electric installations
(power lines etc) to the grid plus costs to the builder (planning,
designing the layout of the plant etc). These costs are estimated at
approximately 460 Sw. Crs/kW (25).

The energy used for building a windmill is repaid in less than

one year (25). Annual costs for running and maintenance are estimated to be less than 0.5 % of the investment cost (25).

Since wind power yields energy only when the wind blows the energy must be stored to be available at need. Long periods of total calm are unusual, especially in the winter when the energy demand is greatest. Thus short-period storage (day-week) is sufficient. Hydro power can be used to even out the load in a system with large scale use of windpower. When the wind blows production of electricity from hydro power is simply reduced. In this manner some 1,000 large wind generators can work together with hydro power. Further needs for equalizing the load can be met by pump storage i.e. demand-regulated electricity production. The need for supplementary generation capacity for a large scale wind power system has not been sufficiently studied.

Instead of producing electricity, windmills can be used directly for supplying mechanical energy (e.g. pumping water) or heat (e.g. for heating recreational houses).

Solar cells (photovoltaic) transform sunlight directly into electricity. The principle of operation is that a direct current is generated when photons of suitable energy are absorbed in a material with semi-conductor properties (8, 24, 28).

15

Concentrating solar systems are somewhat less interesting in
Sweden than in many other countries. This is because the pro-
portion of diffuse light due to cloud cover is relatively large in
Sweden (cf fig. 2.3). The diffuse radiation cannot be concentrated
by mirrors or lenses.

Figure 2.3:

Average insolation on a horizontal surface. Total value, the proportion that comes as diffuse radiation (28) and the demand for electricity. The latter has been drawn so that it has the same mean value as the one for total insolation.

The energy production from solar cells, which we have included in this study, comes from cells mounted near to or on buildings in urban areas, i.e. walls and roofs of houses, covered parking lots etc. Electricity-producing solar cells can also be built into thermal solar collectors (which give heat). No special areas need therefore be set aside for solar power.

16

The basic principle for solar cells are known and a number of different absorbing materials are now being tested. Silicon cells at present are considered to be those for which costs can most rapidly be reduced by mass-production. Efficiencies above 12% in conversion of solar energy to electricity have today been reached using silicon cells. The theoretical maximum efficiency is approximately 20% and the practical large scale efficiency is estimated to be 15 % (24).

For solar cells to play a role in energy supply systems their capital costs must be drastically reduced (1975 in the order of 50 Sw. Crs/peak watt). Persons with experience in conventional mechanics or from nuclear power systems or utilities consider the basic possibilities for this small. Manufacturers of semi-conductors and persons acquainted with the development of semi-conductor technology (e.g. the costs for electronic calculators) are more optimistic. At least four of the large oil companies have concentrated their investments in solar technology on solar cells (30).

The US energy research organization ERDA has set as a goal for 1986 a cost of 2.5 Sw. Crs per peak watt for encapsulated silica cells (2.5 Sw. Crs peak watt is equivalent to 250 Sw. Crs/m2) (31). See cost estimate in fig. 2.4. A cost of 17 Sw. Crs per peak watt is reported to have been reached in Israel (32), (point B in fig. 2.4). According to another recent report it is likely that a cost of 10 Sw. Crs per peak watt can be reached within 2 years (33), (point C in fig. 2.4). The remarkable advances made in development of solar cells has lead ERDA to consider modifying their solar cell program from stimulating development of technology to trying to develop a demand. At a price of 5 - 10 Sw. Crs/peak watt, prospects for a rapid market development are estimated to have been reached. If this occurs the goal of 0.5 Sw. Crs/W is considered realistically obtainable by 1995 (fig. 2.4).