Energy can be stored in many ways, and it is often convenient to think of it as potential energy when attempting to understand what is happening.
Alternative energy is widely seen as important to our future but some known alternative energy sources are carbon-neutral, or close to it, while others are not.
Many alternative energy sources carry with them a severe carbon cost in making steel, concrete or other materials, or in transport and feed stock for sprays.
In 1609, an attempt was made to harness tidal power in the Bay of Fundy, the first time that tidal power had been brought into use, but it was unsuccessful.
Energy has been the cause of social change. The developed world lives at 7.5 kilowatts, the undeveloped world at 1 kilowatt. This needs to change.
The energy we need to live at 7.5 kilowatts involves burning enough fossil fuel to produce 5.5 tonnes of carbon dioxide for each person each year.
Incandescent lamps are inefficient light producers, because much of the electricity they use is converted to heat first and released as waste heat.
Energy conservation will prolong the life of the earth as we know it, and of the life forms on the planet, and so prolong the survival of humanity.
Fossil fuels like coal, gas, oil and peat contain stored solar energy from the past. They can be used far more rapidly than replacements can be formed.
Most renewable energy requires a certain energy input, but some renewable energy sources consume more energy (mostly fossil fuels) than they deliver.
In reality, most alternative energy systems carry a major carbon cost in the manufacture of the components or in lost opportunities like lost photosynthesis.
Some forms of energy are renewable, as we see it in our time frame. In that sense, solar energy is renewable, although in a longer time frame, it is not.
In 1865 W. S. Jevons warned that coal supplies would eventually run out, though he exaggerated estimates of use, and did not allow for oil being used as a fuel.
The best solar conversion systems now convert 9% of sunlight to hydrogen, which is getting close to the generally assumed break-even point of 10%.
Geothermal energy draws heat from hot water and rock, deep underground, and is effectively renewable in our time frame, although not in a longer time frame.
Alcohol which is made from sugar or corn, vegetable oils, draught animals, biologically generated hydrogen and biogas are all renewable energy sources.
Wind power is a form of alternative or renewable energy that relies on the sun for the energy input side. Wind generators require backup, as they stop at times.
Photovoltaic cells convert sunlight to electrical energy but there are problems in getting satisfactorily efficient conversion in mass-produced modules.
There seems to be a practical limit of 25% on the efficiency of photovoltaic cells. There is no good theoretical reason for this limit that anybody can see.
Hydrogen makes a clean and effective fuel, but it needs to come from somewhere in the first place, and it presents special storage and transport problems.
Fuel cells convert the chemical energy of fuel and an oxidant to electrical energy cleanly, but while they show promise, they are not yet fully developed.
At the moment, more people die around the world as a result of mining coal each year than were killed in nuclear accidents in the whole of the past ten years
This file is http://members.ozemail.com.au/~macinnis/scifun/splatswiseenergy.htm, first created on February 16, 2008. Last recorded revision (well I get lazy and forget sometimes!) was on February 16, 2008.