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Users Guide to Off-Grid Energy Solutions
Renewable Energy Resources (RE) Fact Sheet
Renewable energy resources (RE) are generally referred to those energy resources that can be replaced or regenerated continuously, and completely, over a short period of time. There are plentiful and varied renewable energy resources. Renewable energy has been used by humanity as the primary source of energy since the beginning of history, whether for drying meat, fruits and skins, or for cooking food. Renewable energy has been harnessed for more industrialised and complicated processes such as transport (wind for sailing) and grain grinding (first hydropower, later wind milling) for over a thousand years.
Biomass (in the form of charcoal) and hydropower fuelled the Industrial Revolution in Europe and North America before the use of fossil fuels in the latter part of the 18th Century. Renewable energy still comprises a major form of the energy consumed in the developing world. Even in countries as industrially developed as Austria, Sweden and Finland, renewable energy currently accounts for over 20% of all primary energy production and consumption. In the remotest areas of the world, where grid electricity has yet to reach, renewable energy will often play some, if not a major role in meeting off-grid electricity and energy needs. It is for that reason that so much attention is paid in this guidebook to renewables.
The sun's energy is ultimately the source of virtually all renewable energy available on the earth. The sun provides light for heating and generating electricity. It also is the key energy force for photosynthesis for plant (biomass production). Its energy sets the world's weather, thereby affecting rainfall and, by consequence, hydropower, and wind. Tides are a product of the earth's gravitation balance with the moon and the sun. Waves are caused by a combination of the earth's spin and weather, and tides. The following are considered by all as renewable energy resources:
Geothermal energy is renewable, and its energy can only remotely be attributed to the sun in so far as the earth remains within the sun's gravitational sphere. There are definitional issues with whether the following are renewable or not:
- geothermal (waters should be returned to their geothermal reservoirs and springs); and,
- wood (for every tree cut for energy, one should be planted to make it truly renewable).
More contentious yet is whether the following should be considered renewable:
- animal wastes
- agricultural wastes
- municipal and industrial wastes (solid, sewage, other liquids)
Energy from waste is regarded by some as renewable, while others cite that were wastes not produced in the first place (e.g., municipal and industrial wastes), there would be no renewable energy from these sources. Moreover, there is a belief among members of this school of thought that using these wastes to generate energy only encourages people to waste more. This debate seems destined to continue for some time.
Animal and agricultural wastes are also contentious issues among purists in the renewable energy community. There are those who believe all animal and agricultural wastes should be returned directly to the soil in the form of nutrients rather than converted to energy. However, no one debates that if animal wastes (and human wastes) are converted to biogas, that this is renewable and sustainable, as the non-energy by-products (e.g., the slurry) can be, and is, used as a valuable soil nutrient enhancer.
Agricultural wastes produced through processing (e.g., rice husks, sugar bagasse, etc.) are difficult to return to the soil, so even the purists agree that it is better they be used for energy rather than left concentrated in situ to pollute the area, and the ground water. Likewise, wood wastes (e.g., sawdust, shavings, etc.) produced from the harvest of trees and from the processing of the wood, are major renewable energy resources, and most people have no problem with promoting their use as sources of energy.
So long as trees are planted to replace those harvested, renewable energy proponents have no problem with wood as a renewable resource. More contentious is whether it is actually replaced. In many parts of the developed world, such as Western and Eastern Europe, there is now more standing forest than there was 100 years ago. One the other hand, the Tropics are losing their forestry cover at a rate of anywhere between 3-5% per annum. It should be noted, however, that well over 75% of this reduction in forestry cover is attributable to land clearing for settlement, and agricultural and livestock production, and considerably less than 20% of the wood harvested in the Tropics is harvested or used for energy.