Towards renewable energy in Northern Finland

An excess of solar energy exists throughout the world. The developing countries have the greatest potential, but the industrialized world itself is not lacking in opportunities either. Even the most populated countries with a high standard of living, such as the Netherlands or the U.K., consume energy which is equivalent to no more than 1-2 percent of that received from the sun. Activities aimed at utilizing solar radiation could scarcely be restricted by a shortage of this energy, it would seem. This is also the case in northern latitudes like Finland, even at latitudes beyond the Arctic Circle.


Flows of solar energy

Water power, wind and biomass, our most abundant energy sources, all have their origin in the sun. Also, they are all based on flow process, a flow of water, of air, or of photons in the case of photosynthesis and biomass.

The water cycle concentrates solar energy in the rivers. Of all the possible renewable energy flows, a large, high waterfall contains the greatest energy flux density. Niagara Falls, for example, is estimated to produce a potential energy flux of 4400 megawatts, and its energy flux density per square metre can reach as much as one megawatt (Table 1).

A certain concentration of energy also takes place in wind processes. The average velocity of the near-surface wind on the globe is 5,85 metres per second (Lauscher 1951). This exerts an energy of 130 watts on a vertical area of one square metre. Under favourable conditions on coastal sites, a steady wind blows at a velocity of 25 metres per second, with a corresponding effect of 1000 watts per square metre.

But if all the wind energy were extracted, the winds would cease blowing. This strange fantasy restricts the potential of the average wind effect. The energy extracted in one square metre will not appear in another square metre to be extracted again (Gustavson 1979). In common with the water cycle, wind collects and concentrates solar energy, although its energy flux density is far below that of a river.

The effect of solar radiation on a horizontal soil surface has an annual world average of about 200 watts per square metre, the corresponding figure for Finland being about 100 watts. Even in the sunniest region of the world, the Red Sea area, the annual average of the solar flux density is not higher than 280 watts per square metre. Unlike water power and wind, natural solar radiation has no mechanism of concentration.

Table 1. Comparison of certain renewable energy sources

It is interesting that the average effect of the wind (130 watts) almost equals the energy flux density of solar radiation itself, even though the solar flux as a whole is 50 times greater than that of the wind (Gustavson 1979). The same wind blows from one district to another, whereas solar rays are scattered evenly upon districts.

A crucial but largely ignored constraint in solar radiation is its diffuseness. Even in the Red Sea area, almost 1600 hectares of land would be needed to match the energy effect of Niagara (4400 MW). In order to obtain that energy efficiency in terms of electricity, the present low-efficiency artificial quanta collectors (solar cells) should, in fact, cover an area at least three times greater.

The high flux density greatly explains why renewable energy today is preferentially extracted from flowing water rather than from more abundant sources such as the wind and especially the sun. A dense energy flux renders energy production economically feasible, and unless we can break this relationship, solar-driven energy will continue to remain expensive.


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Pohjonen, V. 1985. Towards renewable energy in Northern Finland. In: Siuruainen, E. (Ed.). Ten Years of Work at Research Institute of Northern Finland. University of Oulu. A3:31-41.