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The pros and cons of alternative The pros and cons of alternative energyenergy

The good and the bad?Its mostly

good isn’t it?

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Last lessonLast lesson

We looked at just how dependent we are on fossil fuels both for electricity and powering our transport.But because it is not renewable – at least in the short term – and oil is running out, we need to find other ways of making electricity and running our cars.But the big drawback is burning fossil fuels adds carbon dioxide to the atmosphere, which has the effect of warming the atmosphere, which will cause all manner of problems if we carry on.

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Last lessonLast lesson

We also looked at nuclear power, which while not being renewable is sustainable in the medium to long term. It does not add to the Greenhouse effect as it does not produce carbon dioxide.However the small amount of waste it does produce is highly toxic and hangs around for thousands of years, so it needs careful handling

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Solar – how it worksSolar – how it worksSolar Cells (really called "photovoltaic" or "photoelectric" cells) that convert light directly into electricity. In a sunny climate, you can get enough power to run a 100W light bulb from just one square metre of solar panel.

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SolarSolarThe good pointsThe good pointsSolar energy is free - it Solar energy is free - it needs no fuel and needs no fuel and produces no waste or produces no waste or pollution.pollution.In sunny countries, solar In sunny countries, solar power can be used where power can be used where there is no easy way to there is no easy way to get electricity to a get electricity to a remote place. remote place. Handy for low-power Handy for low-power uses such as solar uses such as solar powered garden lights powered garden lights and battery chargersand battery chargers

The bad pointsThe bad pointsDoesn't work at night. Doesn't work at night. Very expensive to build solar Very expensive to build solar power stations.power stations.Solar cells cost a great deal Solar cells cost a great deal compared to the amount of compared to the amount of electricity they'll produce in electricity they'll produce in their lifetime.their lifetime.Can be unreliable unless Can be unreliable unless you're in a very sunny climate. you're in a very sunny climate. In the United Kingdom, solar In the United Kingdom, solar power isn't much use except power isn't much use except for low-power applications, as for low-power applications, as you need a very large area of you need a very large area of solar panels to get a decent solar panels to get a decent amount of power. However, amount of power. However, for these applications it's for these applications it's definitely worthwhile. definitely worthwhile.

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Solar – the Solar – the futurefuture

1. The solar tower is 115m (377ft) tall and surrounded by 600 steel reflectors (heliostats). They track the sun and direct its rays to a heat exchanger (receiver) at the top of the tower2. The receiver converts concentrated solar energy from the heliostats into steam3. Steam is stored in tanks and used to drive turbines that will produce enough electricity for up to 6,000 homes

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Wind Wind Wind turbines need wind to work. (From my research) they are found mostly on land, but there are many also at sea. They are very very big and tall so that they can catch the stronger air that is further up. The wind makes the propeller turn and the turbine transforms the energy of the movement into electric energy.

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WindWindProsProsWe can get electricity quite easily, We don't have to pay to use windProduces no waste or greenhouse gases. The land beneath can usually still be used for farming.

ConsConsthey don't look very nice and that they are too expensive to build. Some people say that they are noisy and that they interfere with television reception. They don't work without wind, and many birds and bats die by crashing into them.

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Wind – the futureWind – the futureI think there is a future for it because they make a lot of energy so that we can use it in our homes and offices.This 5 megawatt off the German coast is the way the UK intends to go.Off shore wind farms have more reliable wind but are more expensive to build initially.They get around the problems of people who object to building them on land

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Wave powerWave powerThe tide moves a huge amount of water twice each day, and harnessing it could provide a great deal of energy - around 20% of Britain's needs. Although the energy supply is reliable and plentiful, converting it into useful electrical power is not easy. There are eight main sites around Britain where tidal power stations could usefully be built, including the Severn, Dee, Solway and Humber estuaries. Only around 20 sites in the world have been identified as possible tidal power stations.

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How it How it worksworks

A huge dam (called a "barrage") is built across a river estuary. When the tide goes in and out, the water flows through tunnels in the dam. The ebb and flow of the tides can be used to turn a turbine, or it can be used to push air through a pipe, which then turns a turbine. Large lock gates, like the ones used on canals, allow ships to pass.The only operational on in Europe is on the Rance Estuary in Northern France

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Wave powerWave powerProsProsOnce you've built it, tidal power is free. It produces no greenhouse gases or other waste. It needs no fuel. It produces electricity reliably. Not expensive to maintain. Tides are totally predictable. Offshore turbines and vertical-axis turbines are not ruinously expensive to build and do not have a large environmental impact.

ConsCons

A barrage across an estuary is very expensive to build, and affects a very wide area The environment is changed for many miles upstream and downstream, especially the birdsThere are few suitable sites for tidal barrages.Only provides power for around 10 hours each day, when the tide is actually moving in or out.

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Waves – the futureWaves – the futureLots of universities are trying design systems that have less impact than barrages, which do have a heavy environmental impacts

Proposed for Strangford Loch

N Ireland

A study by Swansea University

Research in Canada

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Hydro power from riversHydro power from riversThere are many hydro-electric power stations, providing around 20% of the world's electricity. A dam is built to trap water, usually in a valley where there is an existing lake. Water is allowed to flow through tunnels in the dam, to turn turbines and thus drive generators. Notice that the dam is much thicker at the bottom than at the top, because the pressure of the water increases with depth.

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Hydro from riversHydro from riversProsProsOnce the dam is built, the energy is virtually free. No waste or pollution produced.Very reliable Water can be stored and used when neededHydro-electric power stations can increase to full power very quickly, unlike other power stations. Electricity can be generated constantly.

ConsConsVery expensive to build.– However, many dams are

also used for flood control or irrigation, so building costs can be shared.

Building a large dam will flood a very large area upstream, causing problems for animals that used to live there. Finding a suitable site can be difficult Water quality and quantity downstream can be affected, which can have an impact on plant life

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Hydro – the futureHydro – the futureCurrently, it produces 6% of worldwide energy supply and 20% of its electricity.In the developed world many of the best sites have already been developed.Most of those which are still possible are in LEDCs. As they are very expensive, LEDCs are not building them themselves. But World bank investments in schemes in the past have led to environmental and social consequences that many local people and organisations like WWF for instance are fighting any new ones.So while hydro is an important renewable, it is unlikely to grow much more.

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Geothermal PowerGeothermal PowerHot rocks underground heat water to produce steam. We drill holes down to the hot region, steam comes up, is purified and used to drive turbines, which drive electric generators. There may be natural "groundwater" in the hot rocks anyway, or we may need to drill more holes and pump water down to them.

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GeothermalGeothermalProsProsGeothermal energy does not produce any pollutionThe power stations do not take up much room, so there is not much impact on the environment.No fuel is needed.Once you've built a geothermal power station, the energy is almost free

ConsConsThe big problem is that there are not many places where you can build a geothermal power station. – You need hot rocks of a suitable

type, at a depth where we can drill down to them.

– The type of rock above is also important, it must be of a type that we can easily drill through.

Sometimes a geothermal site may "run out of steam", perhaps for decades. Hazardous gases and minerals may come up from underground, and can be difficult to safely dispose of.

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The futureThe future

Using geothermal energy as a means of heating buildings will become more common. For this you take heat from below ground but not that deep down, and use a heat exchanger to warm air that can then heat your home, even in winter.There are also sites in volcanic regions in the developing world which will be able to generate electricity for the hot rocks

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Biomass for electricityBiomass for electricity

As you see, this is the same flow chart as we saw before for using fossil fuels for generating electricityThere are several fuels, e.g.– Sugar cane waste pulp or "bagasse“– Forestry waste – thinnings, sawmill waster– Bio digestion produces methane as a fuel– Specific crops for fuels– Municipal solid waste– Land fill gas

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BiomassBiomassProsProsIt makes sense to use waste materials where we can. The fuel tends to be cheap.Less demand on the Earth's resources

ConsConsCollecting the waste in sufficient quantities can be difficult. We burn the fuel, so it makes greenhouse gases. Some waste materials are not available all year round.

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Biomass - the futureBiomass - the future

Biomass is the ultimate renewable resource.Many LEDCs are planting crops especially for biofuels, but current ideas see this as possible increasing green house gases if it means clearing forests to plant the cropsHowever, MEDCs produce lots of waste that could be burnt, thus reducing the release of methane. Towns and cities are already running out of suitable landfill sites, and are under EU orders to reduce the amount of waste they bury.

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Fuel cells for carsFuel cells for cars

Fuel cells generate electrical power quietly and efficiently, without pollution. Unlike power sources that use fossil fuels, the by-products from an operating fuel cell are heat and water. The basic idea is to reverse hydrolysis. If you pass an electricity through water, it breaks down into oxygen and hydrogen gas giving 2H2O + energy O2 + 2H2

So if you can reverse it: O2 + 2H2 2H2O + energy

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Fuel CellsFuel CellsProsProsNo polluting gases to cause acid rain and increases in the green house effectUnlimited supply of hydrogenThe cars are quiet smooth and easy to drive

ConsConsHydrogen is not a polluting or a greenhouse gas, but the production methods of collecting hydrogen as yet still do cause emissoins - altho this could changeThe technology used in fuel cell cars is very expensiveGas storage takes up a lot of space, which means you can not go long distances without refilling.

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Fuel Cells – the futureFuel Cells – the future

Developments taking place right now will soon lead to hydrogen being released in vehicle from diesel – but along side this, are second generation biodiesals being produced from city waste, by a process called gasification, which does not have the downside problems of current biodiesals.As the diesel is not burnt, CO2 is not released and so does not add to greenhouses gases.This means that the future looks bright for fuel cells!

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Electric carsElectric cars

Electric vehicles have been around for a very long time. In the early 1900s, there were more electric vehicles than there were petrol cars.Electric vehicles use electricity stored on the car in batteries. Sometimes, 12 or 24 batteries, or more, are needed to power the car. To charge an EV's batteries, the car is usually plugged in at night.

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Electric carsElectric carsProsProsThe cars and busses are quiet smooth and easy to drivePollution freeThey have a number of safety features that means electric shocks etc are unlikelyNo road taxNo congestion charge

ConsConsMost EVs today, however, can only go about 100 miles before you need to plug them in and recharge their batteries.Recharge time can be hours, Batteries only survive so many recharges before they require replacement and they aren't cheapBatteries currently contain unfriendly chemicals that must be handled properly.They tend to be much more expensive to buy and maintain.

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Electric cars – the futureElectric cars – the future

They are improving them all the time and no doubt they will become more and more popularGovernments are encouraging people to use them, especially in towns, to improve air quality – congestion charging in London is not paid

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BiofuelsBiofuelsBiodiesel – a fuel normally derived from plant oils for diesel engines, usually sold blended with traditional dieselBioethanol – a fuel normally derived from starch or sugars for petrol (gasoline) engines, usually sold blended with traditional petrol Biogas – a gas fuel derived from the digestion of organic material, for natural gas engines (limited sale in the UK) All fuels from 2010 will contain 5% biofuel

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BiofuelsBiofuelsProsProsBurning biofuels is carbon neutralCars using biofuels have lower road taxAs petrol gets more expensive, cars using biofuels will be cheaper to run

ConsConsProducing biofuels does use up energyBiofuel growth may mean loss of habitat and forest clearance.If fuel production replaces food production, food prices may riseBiofuels need fertilizer

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Biofuels – the futureBiofuels – the futureWhile there are problems with the current biofuels, ‘second generation’ biofuels do offer hope. For instance, butanol, a fuel that can be produced by fermentation from a diversity of organic material, including waste products from industrial processes, thus ensuring that the raw materials and harvesting involve no extra emissions. The molasses left behind by sugar production and whey from cheese production are possible bases. Butanol has several advantages over ethanol: it has a higher energy output, is easily blended with diesel and, because it is less subject to evaporation, is easier to transport.

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Biofuels – one way forwardBiofuels – one way forwardIn 2002 Indian Railways started using biodiesel in one of its high-speed passenger trains. They found oil-bearing shrubs to produced good quality biodiesel. These plants, once thought to be of very little use, thrive on land which cannot be used for food-crops.Indian Railways intends to use uncultivated land beside its tracks to provide sufficient biodiesel to allow all its trains to use a 10% blend. Jatropha is ideal for the purpose, since its bush-like growth does not impair visibility along the line.

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What are the objections to What are the objections to crops for fuel?crops for fuel?

In Mexico there were riots as demand for corn to fuel American cars pushed the price out of reach of those who needed it for food. Agricultural corporations cleared thousands of acres of rainforest to grow oil palms or sugar cane for biofuel, producing huge carbon emissions as they burned off the vegetation. A UN report said the rush for biofuel could damage the economy and biodiversity in many developing countries. The Royal Society questioned the carbon savings of biofuels and called for targets to be firmly linked to cuts in greenhouse gas emissions. Some research into how much energy goes into growing corn for example, shows that it can take more non-renewable energy to produce that is available in each litre of fuel.

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Why are wind turbines Why are wind turbines unpopular?unpopular?

Some people say that They are uglyThey destroy habitatsThey are not efficient – 75% of the wind is <18 mph and turbines work best at 30mphFeeding wind power into the national grid is expensiveWhole mountainsides are destroyed with huge access roads, giant pits filled with concrete to hold the steel towers, miles of new pylons to join to the national gridWind turbine hum and causes sleep disturbance Shadow flicker, caused when the sun is behind the turbine is similar to strobe lights and may have ill effects on people with epilepsy.