Before the current situation is described, it is
interesting to consider what the potential of renewable energy supply in the
world could be. The table below shows the total potential power output from
each renewable source and the number of times that would cover current usage.
NB: The figures are shown in TW, which is a power
unit. Normally the consumption is given in TWh, which is an energy unit. One TW
corresponds to 8,760 TWh per year.
As can be seen the world consumes on average 15 TW, which
is 15 000 GW or around 2 kW per person in the world. As a comparison each
human consumes around 60 W in his own body.
This means that only a fraction of the energy we
consume comes from our food production. This is an enormous increase as historically
previous generations mainly consumed food and some wood for heating.
The table shows the major potential sustainable energy
source is solar energy. If we could make effective use of this, there would not
be any energy problems in the world. The two main problems with solar power,
however, are that it requires a large surface area to produce sufficient electricity
and that earlier other sources of fuel have been cheaper to obtain.
Wind energy is a form of solar power where nature has
helped to concentrate the energy. Wind is the second biggest potential energy
source. The problem is that wind is less concentrated than hydro and that the
best wind locations are located at sea or in mountains far away from the consumers.
Hydropower is the source that has been mostly widely used
to date. Here nature has done a great job by concentrating the energy in a way
so it has been cheap to exploit. Unfortunately, the potential is not big enough
to produce all our energy need.