A book on the energy in the world has taught me some important things.
As laready well announced, the energy resources including water are going to be run out very soon. The latest prospects say as follows as for the question how long we could use natural gas and petrolium including the unconventinal types like the shale gas/oil. IEA "World Energy Outlook 2009" estimates it 100 years for natural gas while World Energy Council "Survey on Energy Resources 2010" gives 50 years for perolium. Uranium is not an exception which is going to be deficient sooner or later. If the developing countries like Inida or China go on using increasing amount of these rsources, the deficits will come much sooner.
The energy is comprised of not only the electricity, which is coming from the 1st resources of energy, but also of the heat energy. The former is only 46 % of total energy in the energy flow in Japan. We should consider how to lessen the total energy consumption. The utilized energy is approximately 30% of the supplied total energy. The rest is wasted as heat.
We should reduce the total energy requirement as well as the loss occurring in the process of utilization.
We should reform our life style of massive production and massive consumption. The exponential increase of energy consumption is not sustainable. The housing, choice of the transportation vehicles, usage of solar heat or pursuing more efficient energy consuming items etc would decrease the total energy consumption. The energy loss should be decreased with such as cogeneration system or exchage from electricity to the other modes of energy. The latter could be carried out in a small society where the heat associated with electricity generation could be harnessed.
Anyway, I believe we should be aware of the energy crisis going on and should turn to the society sustainable from the standpoint of energy consumption. Or the next generation would suffer from this crisis or so would we.