The potential for sustainable energy supply and consumption & Renewable resources Flashcards
The potential for sustainable energy supply and consumption
Current patterns of energy supply and consumption are unsustainable in the long term. Fossil-fuel reserves are finite and their consumption is polluting.
The UK is currently respsonsible for the release of about 3% of the world’s global greenhouse gases, despite having only 1% of the world’s total population. The UK’s energy industries are its largest singley contributors to greenhouse gas emissions. The increased use of renewable energy resources is thought to be vital if sustainable energy supply and consumption are to be a feature if the future.
Renewable Energy - Wind Energy
Wind Energy is Harnessed by Wind Turbines
Wind power is the fastest-growing renewable energy source.
Wind energy is responsible for 1% of the world’s electricity production. Carbon dioxide is released during the production and installation of wind turbines but once that’s finished no greenhouse gases are released and no fuel is needed.
Wind turbines are built in open exposed areas where there’s a high chance of strong and regular winds.
The energy of the wind turns the blades of the turbine, converting wind energy to mechanical energy, which is then convereted to electrical energy by a generator.
Large-scale wind power involves wind farms that may have thousands of turbines. The electricty generated is fed into the National Grid thats transports electricity to consumers.
Advantages:
- Wind energy is poulltion-free and does not contribute to global warming.
- In Europe and North America, winds tend to blow strongly in winter when demand for electricity is at is highest.
- Wind farms do not take up a lot of space (only 1% of the land on which they are sited), which allows farmland or natural habitats to exist around them.
Disadvantages:
- Wind energy is unpredictable. The amount of electricity generated varies with wind strength.
- Opponents of wind farms claim that many of the windiest sites are also areas of natural beauty. They argue that wind turbines are an unwelcome intrusion into the landscape and an eyesore.
- Some people are worried about the noise the turbines create, particularly as wind farms are often sited in quiet locations; the damage that they could inflict on wildlife (especially birds); and the potential effect on property prices.
- Critics also point out that windfarms require large areas to produce only small amounts of energy. It can take over 7,000 wind turbines to produce the same amount of eenrgy as 1 nuclear power station.
If wind energy is to be viable, a lot of wind turbines will have to be built
Example:
Denmark has been investing in wind power since the 1970s, establishing wind farms onshore and offshore. Famililes are offered tax exemptions for generating their own electricity, either by investing in community turbines or by buying thier own. By 2004 over 150,000 households had joined the scheme. Denmark now produces 19.7% of its electricity from wind power, the highest proportion in the world.
Renewable Energy - Biomass
Biomass is material that’s burnt for power or used to produce Biofuel
Living plants and decaying vegetable matter comprise the greatest bulk of the Earth’s biomass. Biofuel is that part of the biomass that can be converted into energy. At its simplest this involves burning fuel wood, dung and crop residues for cooking in less developed countries. Modern techniques include gasifying the biomass and burning the gas released. In more developed countries biofuels also include the methane that is harvested from landfill sites and municipal waste.
Advantages:
- Using biomass as an energy source can involed a lot of technology (if biofuels are being made), or very little (if biomass is being burnt directly). This means that biomass is a suitable energy source for a wide range of countries.
- Biomass energy is released by burning, which produces carbon dioxide. Biomass doesn’t contribute to global warming though, as the amount of carbon released equals the amount of carbon taken in when the material was growing. This means there’s no overall increase in the amount of carbon dioxide in the atmosphere from the burning of biomass - it is said to be carbon neutral.
Disadvantages
- Large areas of land are needed to produce sufficient amounts of biofuels. This reduces the area of land available to grow food crops, which could lead to food shortages.
- Biomass is only a renewable energy resource is it’s carefully managed - consumption rate needs to not exceed net renewal.
- Fossil fuels are often used to process and transport biomass - contributing to global warming.
Example:
Brazil has been running an ethanol fuel programme since the 1970s. The ethanol is made by fermenting sugar cane, and any leftover cane is burnt for heating and power. Ethanol supplies 18% of transport fuel and cars either run on ethanol or a petrol and ethanol mix. This has decreased Brazil’s dependance on imported oil - by utilising domestic resources to aid energy security and to try to efficiently meet its energy demands.
Renewable Energy - Solar Power
Solar Power Depends on Energy From the Sun
The Earth recieves massive amounts of energy from the sun as incoming radiation. Solar power comes from this radiation and can be used in lots of different ways.
Solar water heaters use solar energy to heat water, which is then pumped to a storage tank ready for use.
Solar cookers work by concentrating sunlight, converting it to heat energy and then trapping it for use in cooking.
Photovoltaic (PV) cells convert light energy into electrical energy, which is used in the home or exported to the National Grid.
Materials that absorb the sun’s heat during the day and release it at night can be used to keep houses warm.
Disadvantages:
- At present the intital investment required for solar energy is high (PV cells are expensive) and conversion efficiency is relatively low.
- Large areas of solar panels and sunny climates are needed to produce large amounts of electricity - in the UK sunshine is less reliable than households living in sunny Mediterranean climates, and the potential for large-scale development of this power source is limited under current levels of technology.
- Carbon dioxide is released in equipment production.
Overall, although the potential for harnessing the sun’s energy is enormous, the locations where the greatest amounts of solar energy could be harvested are often great distances from major centres of population.
Example:
In the Chinese city Rizhao, 99% of buildings have solar water heaters (it’s now compulsory for new builds), over 6000 households use solar cookers and most traffic and street lights are powered by PV cells.
Renewable energy - Tidal Energy
Tidal Energy is a Reliable Source of Energy
Tidal energy comes from the movement of tides. It’s less variable that wind or solar energy as tides are regular, unchangeable events. Tidal energy can be harnessed using tidal barrages or tidal stream systems.
Tidal barrages (dams) are built across estuaries. As the tide flows in and out water passes through gates in the barrage, turning turbines that generate electricity. Some turbines are only turned by outgoing tides, some by incoming as well.
Tidal streams are fast-flowing currents caused by the tide. They turn turbines placed in their pathway to generate electricity.
Arguments for:
- It is renewable & sustainable - consumption rate will never exceed net renewal as it’s impossible to over-exploit the movement of tides
- It is reliable and predictable - tides are naturally occuring, regular, unchangeable events
- Its large size is massively efficient - the projected Severn barrage would provide the same energy as 5 nuclear power stations
- It is non-polluting - does not contribute to global warming
- It benefits the estuary as erosion rates are reduced behind the barrage
Arugments against:
- Flooding of wetlands bordering estuaries, often the home of many species of migrating birds, is damaging - decreases biodiversity by removing habitats of wildlife
- It could have an adverse effect on spawing fish such as salmon, and the turbines can kill aquatic animals - decreases biodiversity
- Construction costs are extremely high and making this equipment releases carbon dioxide.
Example:
The Rance estuary tidal barrage in Northern France began operating in 1967. It’s the largest tidal power station in the world, producing enough electricity for over 19,000 homes.
Renewable Energy - Wave Energy
Wave Energy is Created by Wind Blowing over Water
Wave energy is harnessed by using a wave generator - a chamber with a hole at the top that contains a turbine.
When a wave flows into the bottom of the chamber, the increased mass of water forces air in the chamber upwards and through the hole, which turns the turbine.
The turbine is connected to a generator that produces electricity.
Advantages:
- It is renewable & sustainable - consumption rate will never exceed net renewal as it’s impossible to over-exploit the movement of waves
- It is non-polluting - does not contribute to global warming
- Offshore devices have tremendous potential in terms of the amount of electricity that could be generated
Disadvantages:
- Wave power is one of the least developed renewable energy sources and is thought to be 10 years behind wind power in development terms. Although offshore devices have tremendous potential in terms of the amount of electricity that could be generated, at present they are too expensive to implement on a large scale. In addition, the development of such schemes could create negative environmental changes in tidal basins.
- Wave energy is unreliable, as there aren’t always waves
- Making the generators releases carbon dioxide into the atmosphere.
Examples:
- In 2004 LIMPET in Scotland became the world’s first device that used wave energy on a commercial scale. It generates electricity for the national grid.
- In September 2007 ScottishPower was granted planning permission to build the world’s largest generating capacity commercial wave farm off the Orkney Islands. This was the first wave farm in the UK and became operational in 2008. It cost around £10 million, and consists of four floating 160-m long Pelamis devices, otherwise known as ‘sea snakes’. These provide 3 MW (Megawatts) of renewable electricity, enough to power around 3,000 homes.
