Sustainability of renewable energy sources
Renewable energy sources are generally sustainable in the sense that they cannot ‘run out’ – although, as noted above, both biomass and geothermal energy need wise management if they are to be used sustainably. For all of the other renewables, almost any realistic rate of exploitation by humans would be unlikely to approach their rate of replenishment by nature, though of course the use of all renewables is subject to various practical constraints.
Renewable energies are also relatively ‘sustainable’ in the additional sense that their environmental and social impacts are generally more benign than those of fossil or nuclear fuels. However, the deployment of renewables in some cases entails significant environmental and social impacts. Renewable energy sources are generally much less concentrated than fossil or nuclear fuels, so large areas of land (or building surfaces) are often required if substantial quantities of energy are to be collected. This can lead to a significant visual impact, as in the case of wind turbines.
Also, the monetary costs of many renewable sources are at present considerably higher than those of conventional fuels. Until this imbalance is reduced, either by reducing the costs of renewables or through increases in the costs of conventional sources, renewables may be unable to succeed in capturing a substantial fraction of the world market.
Renewables may seem attractive in many ways, but how large a contribution might they make to world energy needs in the future?
After text activity
I. Reading exercises:
Exercise 1.Read and memorize using a dictionary:
| geothermal energy, earth’s internal heat, decay, long-lived radioactive elements, aquifers, tectonic activity, sustainability, replenishment, environmental impact, world energy needs |
Exercise 2.Answer the questions:
1) What is the source of geothermal energy?
2) For what purposes is the resulting hot water/steam used?
3) Are the environmental and social impacts of renewable energies more or less benign than those of fossil or nuclear fuels?
4) Are the monetary costs of many renewable sources high compared with those of conventional fuels?
Exercise 3.Match the left part with the right:
| 1. Geothermal energy originates | a) considerably higher than those of conventional fuels |
| 2. Renewable energy sources are | b) from the earth’s internal heat |
| 3. The earth’s internal heat originates | c) less concentrated than fossil fuels |
| 4. The costs of renewables are | d) from the decay of long-lived radioactive elements |
THE SPEAKING MODULE
II. Speaking exercises:
Exercise 1.Describe decay, geothermal energy, long-lived radioactive elements, aquifer, sustainability, environmental impactusing the suggested words and expressionsas in example:
| decay spontaneous, transformation, nuclide, different, nuclides, accompanied, emission, particles, nucleus, nuclear, capture, ejection, orbital, electrons, fission Example: A spontaneous transformation of a nuclide into one or more different nuclides, accompanied by either the emission of particles from the nucleus, nuclear capture or ejection of orbital electrons, or fission. |
| geothermal energy thermal, energy, contain, earth; use, directly, supply, heat, convert, mechanical, electrical, energy. |
| long-lived radioactive elements element, isotopes, spontaneously, transform, different, nuclides, give off, various, types, radiation; long, period, disintegration |
| aquifer porous, deposit, rock, contain, water, use, supply, wells |
| sustainability stable, development, environment, preservation, natural, reserves |
| environmental impact extent, pollution, environmental, degradation |
Exercise 2.Ask questions to the given answers:
1) Question: ____________________________________________________?
Answer: The most useful geothermal resources occur where underground bodies of water called aquifers can collect this heat.
2) Question: ____________________________________________________?
Answer: Geothermal energy is already making a minor but locally useful contribution to world energy supplies.
3) Question: ____________________________________________________?
Answer: If geothermal heat is extracted in a particular location at a rate that does not exceed the rate at which it is being replenished from deep within the earth, it is a renewable energy source.
THE WRITING MODULE
III. Writing exercises:
Exercise 1.Complete the sentences with the suggested words:
Out, if, in, both, as, to
Renewable energy sources are generally sustainable ___ the sense that they cannot ‘run___’ – although, ____noted above, ____biomass and geothermal energy need wise management ____they are ____be used sustainably.
Exercise 2. Fill in the table with words and expressions from the text:
| countries | physical phenomena | impacts | |
| Example: The source of geothermal energy is | - | the earth’s internal heat. | |
| The deployment of renewables in some cases entails | |||
| Steam and hot water from aquifers are used for electricity generation | |||
| The source of the earth’s internal heat is |
Exercise 3. Compose a story on one of the topics (up to 100 words):
“Geothermal Heat: Renewable or not Renewable?”
“Sustainability of Renewables”
LESSON 6
THE READING MODULE
Read the text: BIOMASS AND COPPICING FOR CHEAP, RENEWABLE ENERGY
Biomass is a biofuel derived from plantswhich are harvested and suitably processed for burning. The heat produced is the form of energy which can be harnessed. Other names commonly associated with the technique are Coppicing and Energy Fuel. Biomass is, strictly, a form of biofuel but when we talk about biofuels normally we have in mind biodiesel or ethanol and methanol which are mainly applicable to motor vehicles.
The concept becomes attractive only when the plants are replaced at a rate equal to the rate at which they are harvested. It is argued that the carbon sinking effect of the growing plants neutralises the carbon emitted when the fuel is burnt. Young trees are better sinks than mature trees. Since the extraction of energy is accompanied by the release of carbon, it is not such an ideal solution as the generation of solar or wind power. Nevertheless, it provides a renewable source which can be called on no matter what the prevailing weather conditions are and is much more eco-friendly than burning fossil fuels such as coal and oil. Additionally, it can be a cheap option.
Biomass methods are basically low tech and they are particularly useful where there is surplus low-grade arable land. Therefore the system is appropriate, not only for some undeveloped countries, but also for the UK and other parts of Europe where efficient agricultural techniques frequently lead to overproduction of food crops. The potential is attractive because it is relatively cheap (eg compared to the radical solar, wind, etc schemes). Although the processing requires the input of energy (cutting, chipping, pelleting, transporting etc) it can be quite efficient. Where the location is suitable, for example in rural areas, end-users may have access to logs at negligible expense and others may be able to extract clean (ie untreated) timber from constructors' waste which otherwise may go into landfill.
If this process was developed fully in the UK, it could become a major agricultural industry and would be capable of meeting a significant proportion of the current electrical demands. One of the most practical ways of generating biofuels is to plant fast-growing trees, such as willow, and cut them back every few years, allowing further growth to occur. This is usually referred to as coppicing and the fuel is solid wood, often chipped or pelleted. Another method is to grow suitable green plants from which liquid vegetable oil can be extracted.
Biomass implementation is not without its opponents. Apart from the underlying disadvantages that carbon is emitted and there may be toxic products of combustion, some feel that the countryside would be spoiled by the sight of disfigured forests, and there are other legitimate objections such as the hogging of arable land and a reduction in biodiversity.
On the other hand the prospect of a new, significant, cleanish, renewable energy source which is cost effective and which will provide employment is likely to appeal to government and farmers alike. Pelleted wood burners are likely to increase in use in the UK because the fuel should be reliably available and in areas where oil and electricity are the norm the capital outlay can be offset in a few years. In summary biomass has the potential to contribute to carbon reduction, convenience and possibly economic development.
After text activity
I. Reading exercises:
Exercise 1.Read and memorize using a dictionary:
| biomass, biofuel, coppicing, biodisel, motor vehicle, carbon sinking effect, low tech, eco-friendly, arable land, food crops, processing, cutting, chipping, pelleting, timber, landfill, end-user, combustion, hogging, biodiversity, pelleted wood burners |
Exercise 2.Answer the questions:
1) What is “biomass”?
2) Where are the biomass methods particularly useful?
3) Which is the most practical way of generating biofuels?
4) What are the underlying disadvantages of biomass implementation?
Exercise 3.Match the left part with the right:
| 1. Biomass is | a) planting fast-growing trees and cutting them back every few years, allowing further growth to occur. |
| 2. Coppicing is | b) in use in the UK. |
| 3. Pelleted wood burners are likely to increase | c) a biofuel derived from plantswhich are harvested and suitably processed for burning. |
| 4. The prospect of a new, cleanish, renewable energy source is likely to appeal | d) to government and farmers alike. |
THE SPEAKING MODULE
II. Speaking exercises:
Exercise 1.Describe biomass, carbon sinking effect, processing, chipping, timber, landfillusing the suggested words and expressionsas in example:
| biomass dry, weight, living, matter, include, stored food, present, species, population, express, terms, given, area, volume, habitat. Example: The dry weight of living matter, including stored food, present in a species population and expressed in terms of a given area or volume of the habitat. |
| carbon sinking effect effect, some, extensive, quantity, carbon, absorb |
| chipping process, reducing, large, pieces, wood, chips. |
| timber wood, use, building, carpentry, joinery. |
| landfill special, place, territory, various, waste, garbage, take, keep |
Exercise 2.Ask questions to the given answers:
1) Question: _________________________________________?
Answer: Other names commonly associated with the biomass technique are Coppicing and Energy Fuel.
2) Question: __________________________________________________ ?
Answer: Biomass methods are basically low tech.
3) Question: ___________________________________________________?
Answer: Another method is to grow suitable green plants from which liquid vegetable oil can be extracted.
THE WRITING MODULE
III. Writing exercises:
Exercise 1.Complete the sentences with the suggested words: