Renewable
Updated 12th April 2008
What is a 'renewable' resource?
A renewable resource is one which is regenerative or which cannot be depleted. Renewable energy therefore is energy which is derived from a source which cannot run out, or which is “obtained from the continuous or repetitive currents of energy reoccurring in the natural environment” (Twidell and Weir 1986).
Fossil Fuels
Fossil fuels exist in finite quantities and were formed over tens of millions of years and in very specific climatic circumstances. They are certainly not a renewable resource: when they are depleted to the point at which we can no longer extract them from under the surface of the earth, that's it.
Turf
Although turf (peat) forms from the build up of partially decayed organic matter, it cannot be considered renewable in the timescale of a human being. The turf deposits in Ireland took thousands of years to form. Year on year turf formation may be as little as a millimetre per year.
Nuclear Energy
There is some disagreement about whether nuclear energy can be considered renewable. While the advocates of nuclear energy frequently argue it is not a finite source of energy, this is not strictly accurate.
Nuclear Fission
The process by which contemporary nuclear reactors work, nuclear fission, is one which requires uranium for fuel, and uranium is indeed a finite resource and one which would be depleted very quickly were the world to switch over from fossil fuels to nuclear energy ( leaving aside the enormous technical and infrastructural difficulties involved).
Although one type of nuclear fission reactor, the fast breeder, creates its own fuel (Plutonium-239), this form of reactor has been singularly unsuccessful to date and the risks associated with Plutonium-239, which is extremely toxic and has a half-life of 24,000 years, do not make it an attractive proposition.
Nuclear Fusion
In theory, it is possible to harness the energy of a different type of nuclear reaction, namely fusion. Uncontrolled nuclear fusion reactions occur in a thermonuclear explosion, which is what takes place when a hydrogen bomb is detonated. While the effects of such detonations are horrendous, the raw materials (deuterium and tritium) are simply isotopes of hydrogen, hence the name hydrogen bomb.
While creating a hydrogen bomb is relatively straightforward, harnessing nuclear fusion for peaceful purposes has defied the best efforts of nuclear physicists for half a century. There is a standing joke in the nuclear energy community that nuclear fusion is 50 years away from being developed as a useful source of energy. In another thirty years, it will still probably be 50 years away, and by then the world will have moved on to other things.
Renewable Energy Sources
Biofuels
Wood and other biofuels are regarded as renewable sources of energy, but this is only true if the land resource is managed in a sustainable manner. Chopping down the rain forests of Brazil and Malaysia to grow sugar cane (for ethanol production) and palm trees ( for palm oil) to replace the soon-to-be diminishing supplies of petroleum based fuels hardly fits any definition of what constitutes sustainable practice.
Both the EU and the USA are encouraging the use of biofuels without first ensuring that checks are in place to prevent the wanton destruction of the remaining rainforests and other ecosystems by unscrupulous transnational corporations. This is not only irresponsible; this is criminal act which should rank on a par with genocide.
Solar Energy
This is energy derived directly from solar radiation and can be harnessed to deliver heat or to generate electricity using solar photovoltaics ( solar PV).
Solar PV panels are able to convert about 10-12% of solar radiation into electricity while a typical solar water heater is about 20-50% efficient, depending on how the resource is managed and what the heat is being used for.
Wind Energy
Windmills have been used to harness the kinetic energy of the wind to drive mills and pump water for thousands of years, and in many countries of the world this technology can still be found. In the more industrialised nations, wind energy is used to generate electricity, sometimes on a massive scale.
Wind turbines vary in size from ones which will only provide sufficient power to run a lightbulb to ones which are capable of running a small town. While the resource is enormous, the intermittant and unpredictable nature of wind makes it a difficult resource to utilise, and the best wind resources are often to be found in places ( naturally enough) where few people live.
Hydro
Hydro-energy is the energy which can be captured from moving bodies of water such as rivers, mill races or penstocks ( the channel which connects a dam with a turbine). Although hydro energy is utilised to drive mechanical devices such as mills or simple machinery in the less industrialised parts of the world, it is more commonly associated with the generation of electricity, sometimes on a massive scale.
Large hydro electric projects involve the building of immense dams, with equally large attendant environmental (and often social) costs, notably in Turkey and China but in many other parts of the world too.
Also, the reservoirs behind the dams gradually silt up over time too, so the projects have a very limited lifespan before remedial dredging is required or the dam ceases to be useful. Although hydro energy is a very large and very reliable source of energy, it is quite a limited resource as there are only a finite number of locations suitable for building dams.
Ocean Energy
Although, like hydro, ocean energy is also derived from water, it is usually viewed as being a distinct form of energy in its own right. Its sole application is to generate electricity.
The sector can be further subdivided, usually into tidal stream energy and wave energy. Tidal streams are places where the tidal currents are compressed into relatively narrow channels between islands or different land masses. It is argued that this energy can be harnessed using undersea turbines. In some parts of the world, notably Scotland but to a lesser extent Ireland, the potnetial tidal stream energy resource is huge.
The energy of the waves is characterised by the ever moving sea. Many different prototypes and some working models have been built to capture some of this energy and convert it into electricity.
Both types of ocean energy technologies are still in their infancies and it has yet to be proven they will be viable on a large scale. Many technical problems remain, not least of which is how to prevent the devices from being destroyed by the very energy they are trying to capture.
Low Density Environmental Energy
This is a catch all expression for low density background environmental heat which can be utilised using devices called heat pumps. Heat pumps are able to concentrate the low density heat of the ground, of bodies of water or even the air, into high density heat (typically 30 degrees Celsius or higher) which can then be used for space or water heating.
Heat Pump Technology
For every one unit of energy used by the heat pump, some 2.4-3.2 units of useful heat energy are delivered. This phenomena has led to manufacturers and suppliers alike descibing heat pumps as being "300% efficient", though strictly speaking this is not true. A more accurate unit of measurement is the coefficient of performance ( COP), which measures the useful energy output against the energy input. A well designed heat pump based heating system, therefore, might have a COP of 3.0 or higher.
The downside is that to run a heat pump requires electricity. Heat pumps are not renewable energy devices but they do permit a renewable energy source to be tapped. While this might still sound very impressive, the advantages of the COP of 3.0 (or less as is often the case) is pretty much offset by the very low efficiency of fossil fuel fired power stations (only about 38% in Ireland) and the high level of emissions which arise from generating electricity in this manner.
While heat pump based heating systems may be economical to run, the benefits to the environment are negligable unless the electricity is also derived from renewable sources. When manufacturers and suppliers describe this technology as being 'emission free', they are talking rubbish.
Some Facts on Renewable Energy
Ireland generates approximately 7% of its electricity from renewable sources. In spite of grandiose claims that this proportion will rise to 20% or even 30% by 2020, there is no strategy in place for achieving these objectives.
In 2001, the EU adopted the Electricity Production from Renewable Energy Directive, which set a target of 22% of electricity from renewable energy by 2010. Possibly in recognition of the ineptitude of our politicians, Ireland was given a rather more modest target of 13.2%. Even though we have some of the best wind resources in Europe, it is highly unlikely that even this lesser target will be met on time.
Of Irelands total energy requirements (transport, heating and electricity combined) less than 3% comes from renewables. Only 0.02% of our transport fuel comes from renewable sources... over 99.9% comes from imported fossil fuels.
The EU has set a target of 5.75% of transport fuels to be provided by biofuels by 2010. Apart from chopping down the entire Amazon rain forest and planting sugar cane there instead, there is no possibility the EU will make this target in the time available. Indeed, the only way the EU could ever meet this target using biofuels produced in Europe would be by drastically reducing fuel consumption. But politicians don't want to admit that. Nor are they inclined to discuss where the remaining 94.75% of fuel might come from in the future.
In Ireland's case, the 5.75% target might eventually be realisable, owing to our low population density, but only if there was a huge countrywide effort to develope our land resource. Even then, it will take many years.
This percentage would be close to the maximum possible at current transport fuel requirements, and would require as much land to be set aside for biofuels as is currently used for all our field crops combined. If we want to produce a higher percentage of fuel, the only way is to reduce demand. The best we can hope for by 2010 is about 0.5%.
There is a solution however... use less energy. Ireland could reduce its total energy requirement by at least 75% over 30 years and probably would be far better off for it. Among the many positive benefits would be: less pollution, less waste, better quality food, less time wasted grid locked in traffic, and a healthier population.
