Greener Energy Sources

Geothermal Energy Consumption

Thu, 14 Aug 2008 20:32:58 GMT

Utilization of wind energy has increased spectacularly in recent years, with a 27% increase in installed capacity during 2007 capping similar rises in previous years. The 20 GWe increment represented an investment of EUR 25 billion (US$ 37 billion). This brought total world wind capacity to 94 GWe, with tens of thousands of turbines now operating.

Wind turbines of up to 5 MWe are now functioning in many countries, though most new ones are 1-2 MWe. The power output is a function of the cube of the wind speed, so doubling the wind speed gives eight times the energy potential. In operation such turbines require a wind in the range 4 to 25 metres per second (14 - 90 km/hr), with maximum output being at 12-25 m/s (the excess energy being spilled above 25 m/s). While relatively few areas have significant prevailing winds in this range, many have enough to be harnessed effectively and to give better than a 25% capacity utilisation. Alternative power sources allow the system to cope with calmer periods.

Where there is an economic back-up which can be called upon at very short notice (eg hydro), a significant proportion of electricity can be provided from wind. The most economical and practical size of commercial wind turbines is now up to 2 MWe, grouped into wind farms up to 200 MWe. Depending on site, most turbines operate at about 25% load factor over the course of a year (European average), but some reach 33%. Wind is projected to supply 3% of world electricity in 2030, and perhaps 10% in OECD Europe.
Germany leads the field with over 22 GWe installed, Spain has over 15 GWe and the USA has over 16 GWe. The average size of new turbines in USA in 2007 was 1.6 GWe.

With increased scale and numbers of units, generation costs have been diminishing. They are still greater than those for coal or nuclear, and allowing for backup capacity and grid connection complexities adds to them. However, government policies in many countries ensure that power from them is able to be sold (see Appendix). The US capacity is claimed to produce 31 billion kWh per year at 30.5% capacity factor, and relies on only a small production tax credit.

Wind turbines have a high steel tower to mount the generator nacelle, and have rotors with three blades up to 50m long. Foundations require a substantial mass of reinforced concrete. Hence the energy inputs to manufacture are not insignificant. Also siting is important in getting a net gain from them. In the UK the Carbon Trust found that small wind turbines on houses in urban areas often caused more carbon emissions in their construction and fitting than they saved in electrical output (CT 7/8/08).

SOLAR ENERGY

Solar energy is readily harnessed for low temperature heat, and in many places domestic hot water units (with storage) routinely utilise it. It is also used simply by sensible design of buildings and in many ways that are taken for granted. Industrially, probably the main use is in solar salt production - some 1000 PJ per year in Australia alone (equivalent to two thirds of the nation's oil use)
Three methods of converting the sun's radiant energy to electricity are the focus of attention. The best-known method utilises sunlight acting on photovoltaic cells to produce electricity.

Flat plate versions of these can readily be mounted on buildings without any aesthetic intrusion or requiring special support structures. Solar photovoltaic (PV) has application for certain signalling and communication equipment, such as remote area telecommunications equipment in Australia or simply where mains connection is inconvenient. Sales of solar PV modules are increasing strongly as their efficiency increases and price falls. Even working on 1 kilowatt per square metre in the main part of a sunny day, intensity of incoming radiation and converting this to high-grade electricity is still relatively inefficient, though it has been the subject of much research over several decades. But the cost per unit of electricity - at least ten times that of conventional sources, limits its potential to supplementary applications on buildings where its maximum supply coincides with peak demand.

More efficiency can be gained using concentrator PV (CPV), where some king of parabolic mirror tracks the sun and increases the intensity of the solar radiation op to 1000-fold. Modules are typically 35-50 kW and some 18 MWe of CPV capacity was installed in 2006.

For a stand-alone system some means must be employed to store the collected energy during hours of darkness or cloud - either as electricity in batteries, or in some other form such as hydrogen (produced by electrolysis of water). In either case, an extra stage of energy conversion is involved with consequent energy losses.

Several experimental PV power plants mostly of 300 - 500 kW capacity are connected to electricity grids in Europe and USA. Japan has 150 MWe installed. A large solar PV plant was planned for Crete. Several Spanish PV plants are over 20 MWe. In Australia a 154 MWe solar PV power station is planned for northern Victoria, costing $420 million and expected to come into operation over 2010-13. Research continues into ways to make the actual solar collecting cells less expensive and more efficient. In some systems there is provision for feeding surplus PV power from domestic systems into the grid as contra to normal supply from it, which enhances the economics.

A solar thermal power plant has a system of mirrors to concentrate the sunlight on to an absorber, the energy then being used to drive turbines. The concentrator is usually a parabolic mirror trough oriented north-south, which tracks the sun's path through the day. The absorber is located at the focal point and converts the solar radiation to heat (about 400°C) which is transferred into a fluid such as synthetic oil. The fluid drives a conventional turbine and generator. Several such installations in modules of 80 MW are now operating. Each module requires about 50 hectares of land and needs very precise engineering and control. These plants are supplemented by a gas-fired boiler which generates about a quarter of the overall power output and keeps them warm overnight. Over 350 MWe capacity worldwide has supplied about 80% of the total solar electricity so far. With solar input being both diffuse* and interrupted by night and by cloud cover, solar electric generation has a low capacity factor, typically less than 15%. Power costs are two to three times that of conventional sources, which puts it within reach of being economically viable where carbon emissions from fossil fuels are priced.

* In low to middle latitudes on a sunny day up to 1 kW/m² falls on a surface maintained at right angles to the sun's rays. In Europe much less than this is received through much of the year, for instance in winter most of Europe averages less than 1 kWh/m² per day (on a horizontal surface).

In mid 2007 Nevada Solar One, a 64 MWe capacity solar thermal energy plant, started up. The $250 million plant is projected to produce 124 million kWh per year and covers about 160 ha with mirrored troughs that concentrate the heat from the desert sun on to pipes that contain a heat transfer fluid.

Another kind of solar thermal plant is the solar tower, using a huge chimney surrounded at its base by a solar collector zone like an open greenhouse. The air under these is heated and rises up the chimney, turning turbines as it does so. A 200 MWe installation planned for Australia would use 32 turbines each of 6.25 MWe with a 7km diameter collector zone under a 1000 metre high tower. Thermal mass - possibly brine ponds - under the collector zone means that some operation will continue into the night. A 50 kWe prototype plant of this design operated in Spain 1982-89, and a 50 MWe prototype is proposed in Australia before the full-scale version.

The main role of solar energy in the future will be that of direct heating. Much of our energy need is for heat below 60^oC - eg. in hot water systems. A lot more, particularly in industry, is for heat in the range 60 - 110^oC. Together these may account for a significant proportion of primary energy use in industrialised nations. The first need can readily be supplied by solar power much of the time in some places, and the second application commercially is probably not far off. Such uses will diminish to some extent both the demand for electricity and the consumption of fossil fuels, particularly if coupled with energy conservation measures such as insulation.

With adequate insulation, heat pumps utilising the conventional refrigeration cycle can be used to warm and cool buildings, with very little energy input other than from the sun. Eventually, up to ten percent of total primary energy in industrialised countries may be supplied by direct solar thermal techniques, and to some extent this will substitute for base-load electrical energy.

GEOTHERMAL ENERGY

Where hot underground steam can be tapped and brought to the surface it may be used to generate electricity. Such geothermal sources have potential in certain parts of the world such as New Zealand, USA, Philippines and Italy. Some 8000 MWe of capacity is operating, including 3000 MWe in the USA and 2000 MWe in Philippines, and in 2002 geothermal produced more electricity than did wind worldwide. In Japan 500 MWe of capacity produces 0.3% of the country's electricity. In New Zealand 420 MWe produces over 7% of the electricity, and Iceland gets most of its electricity from 200 MWe of geothermal plant. Lihir Gold mine in Papua New Guinea has 56 MWe installed, the last 20 MWe costing US$ 40 million - about the same as annual savings from the expanded plant. Geothermal electric output is expected to triple by 2030.

There are also prospects in certain other areas for hot fractured rock geothermal - pumping water underground to regions of the Earth's crust which are very hot or using hot brine from these regions. The heat - around 250°C - is due to high levels of radioactivity in the granites and because they are insulated at 4-5 km depth. They typically have 15-40 ppm uranium and/or thorium, but may be ten times this. The heat from radiogenic decay* is used to make steam for electricity generation. South Australia has some very prospective areas. The main problem with this technology is producing and maintaining the artificially-fractured rock as the heat source. A 50 MWe plant is envisaged as having 9 deep wells - 4 down and 5 up.

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Government Support for Renewables Deployment

Thu, 14 Aug 2008 20:27:58 GMT

In an open market, government policies to support particular generation options such as renewables normally give rise to explicit direct subsidies along with other instruments such as feed-in tariffs, quota obligations and energy tax exemptions. In the EU, feed-in tariffs are widespread.

Corresponding to these in the other direction are taxes on particular energy sources, justified by climate change or related policies. For instance Sweden taxes nuclear power at about EUR 0.6 cents/kWh.

European Environment Agency figures in 2004 gave indicative estimates of total energy subsidies in the EU-15 for 2001: solid fuel (coal) EUR 13.0, oil & gas EUR 8.7, nuclear EUR 2.2, renewables EUR 5.3 billion.

Germany applies a mixture of incentives for renewables, such as a feed-in tariff arrangement which guarantees renewable energy producers up to 90% of the retail domestic electricity price (so they get about EUR 8.86 c/kWh total). In November 2001 the German parliament decided to increase its subsidies for solar and some other renewable technologies by one third. The combined subsidy from consumers and government totals some EUR 5 billion per year - for 6% of its electricity.

Denmark has a wide range of incentives for renewables and particularly wind energy, accounting for nearly one third of total wholesale electricity prices. In 2000 it produced 4 TWh (out of 36 TWh gross total, about 11%) thus, and is aiming at 15%. Its utility buy-back rates for privately-generated wind electricity in 1999 averaged DKr 0.60/kWh, including a DKr 0.27/kWh subsidy funded by carbon tax (now US$ 6.8 cents & 3.2 cents respectively). This is now being replaced by a complex 'Green Certificate' scheme which will transfer the subsidy cost to consumers. However, there is a further economic cost borne by power utilities and customers.

When there is a drop in wind, back-up power is bought from the Nordic power pool at the going rate. Similarly, any surplus (subsidised) wind power is sold to the pool. The net effect of this is growing losses as wind capacity expands. Official estimates put the expected losses at DKr 1.5 billion per year, others reckon more than double this.

Sweden subsidises renewables (principally large-scale hydro) by a tax on nuclear capacity, which (late in 2001) works out at EUR 0.32 cents/kWh.

In Norway the government subsidises wind energy with a 25% investment grant and then production support per kWh, the total coming to NOK 0.12/kWh, against a spot price of around NOK 0.18/kWh (US$ 1.3 cents & 2 cents respectively).

In the USA the wind energy production tax credit (PTC) of 1.5 c/kWh indexed to inflation (now about 1.8 c/kWh) has provided incentive, though this expires every two years before being renewed by Congress.

In Australia energy retailers are required to source specified quantities of power from new (non hydro) renewables. The obligation is tradeable and there is a fallback tax of AUD 4 c/kWh for retailers failing to comply.

Spain has a fixed tariff of EUR 6.28 c/kWh for wind energy or a market-related tariff plus an environmental premium of 2.9 c/kWh (in 2002). The tariffs for renewables are adjusted annually to be 80-90% of the predicted retail electricity price.

Greece has a feed-in tariff of 6.1-7.5 c/kWh, whereas the Netherlands relies on exemption from energy taxes to encourage renewables.

The UK does not use any feed-in tariff arrangement, but a specific indication of the cost increment over power generation from other sources is given by the 4.5 - 5.0 p/kWh market value for the Renewables Obligation in early 2004, by which utilities can cover the shortfall in producing a certain proportion of their electricity from renewables by paying this amount and passing the cost on to the consumer. In addition there is a Climate Change Levy of 0.43 p/kWh on non-renewable sources (at present including nuclear energy, despite its lack of greenhouse gas emissions), which corresponds to a subsidy.

Small-scale PV input is encouraged by high feed-in tariffs, eg 48 c/kWh in Germany and 50 c/kWh in Portugal.

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Renewable Energy & Electricity

Thu, 14 Aug 2008 20:20:25 GMT

There is a fundamental attractiveness about harnessing such forces in an age which is very conscious of the environmental effects of burning fossil fuels and sustainability is an ethical norm. So today the focus is on both adequacy of energy supply long-term and also the environmental implications of particular sources.
In that regard the near certainty of costs being imposed on carbon dioxide emissions in developed countries at least has profoundly changed the economic outlook of clean energy sources.A market-determined carbon price will create incentives for energy sources that are cleaner than current fossil fuel sources without distinguishing among different technologies. This puts the onus on the generating utility to employ technologies which efficiently supply power to the consumer at a competitive price.

Sun, wind, waves, rivers, tides and the heat from radioactive decay in the earth's mantle as well as biomass are all abundant and ongoing, hence the term "renewables". Only one, the power of falling water in rivers, has been significantly tapped for electricity for many years, though utilization of wind is increasing rapidly and it is now acknowledged as a mainstream energy source. Solar energy's main human application has been in agriculture and forestry, via photosynthesis, and increasingly it is harnessed for heat. Electricity remains a niche application for solar. Biomass (eg sugar cane residue) is burned where it can be utilised. The others are little used as yet.

Turning to the use of abundant renewable energy sources other than large-scale hydro for electricity, there are challenges in actually harnessing them. Apart from solar photovoltaic (PV) systems which produce electricity directly, the question is how to make them turn dynamos to generate the electricity. If it is heat which is harnessed, this is via a steam generating system.

If the fundamental opportunity of these renewables is their abundance and relatively widespread occurrence, the fundamental challenge, especially for electricity supply, is applying them to meet demand given their variable and diffuse nature*. This means either that there must be reliable duplicate sources of electricity beyond the normal system reserve, or some means of electricity storage. Policies which favour renewables over other sources may also be required. Such policies, now in place in about 50 countries, include priority dispatch for electricity from renewable sources and special feed-in tariffs, quota obligations and energy tax exemptions.

* The main exception is geothermal, which is not widely accessible.

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Gordon Brown Unveils Renewable Energy Plan

Thu, 14 Aug 2008 20:15:33 GMT

Thousands of new wind turbines could be built across the UK as part of a £100bn investment in renewable energy that could create hundreds of thousands of new "green collar" jobs, Gordon Brown announced today.

The prime minister unveiled what he described as a "green revolution" and "the most dramatic change in energy policy since the advent of nuclear power".

He wants to build up Britain's clean power supply in order to reach the EU-imposed target of producing 15% of the country's energy from renewable sources by 2020. This will require £100bn of investment from the private sector, which the government will encourage with financial incentives due to be announced later by the business secretary, John Hutton.

In a speech to an energy summit at the Tate Modern art gallery in central London, Brown said that the North Sea, which has passed its peak in terms of oil and gas supplies, will be turned into "the equivalent for wind power of what the Gulf of Arabia is for oil". Wind turbines will also be built inland, but with sensitivity towards local communities.

Householders will be encouraged to reduce their bills through energy-saving incentives due to be announced later this summer, said Brown. Within a decade he said he wanted every householder able to do so to fit loft or cavity wall insulation, install low-energy light bulbs, and use low-energy consumer goods.

The government will also shortly begin a new advertising campaign showing people what steps they can take to reduce their energy and fuel bills – steps such as turning appliances off rather than leaving them on standby, and fitting new shower heads.
In the autumn, said Brown, the government will consult on a new plan aimed at changing the way in which energy companies operate – encouraging them not to supply ever more units of electricity and gas, but to make profits from reducing, not increasing, demand.

"This is a green revolution in the making," Brown said. "It will be a tenfold increase on our current deployment of renewables, and a 300% increase on our existing plans: the most dramatic change in our energy policy since the advent of nuclear power."
He said it would mean that by 2020 renewables would account for over 30% of electricity supply, 14% cent of heat supply and up to 10% cent of transport fuels.

Brown estimated that the renewables programme would generate around 160,000 jobs, and plans for new nuclear power stations around 100,000, with many more created from energy-saving measures.

The prime minister also said that he was prepared to take on public opinion over green taxes, insisting that a low-carbon society would not emerge from a "business as usual" approach.

"It will require real leadership from government - being prepared to make hard decisions on planning or on tax for example," he said.

"It will mean new kinds of consumer behaviour and lifestyles. And it will demand creativity, innovation and entrepreneurialism throughout our economy and our society."

The shadow business secretary, Alan Duncan, said that after a series of "painful and reluctant U-turns", the government had come round to the Conservatives' vision of a greener Britain.

He criticised Brown for launching a consultation on energy after a "decade of dithering".

"Gordon Brown must now translate these words into action. If we don't grasp this opportunity now, we'll still be playing catch-up in 20 years," said Duncan.

The Liberal Democrats' environment spokesman, Steve Webb, said that, with Britain near the bottom of the European renewables league table, he found it hard to believe Brown's talk of a "green revolution".

He said: "The fundamental problem is that Brown doesn't do 'green'. He would rather urge oil producers to extract more oil than invest in technologies that will actually save CO2 emissions now.

"When the government has failed so lamentably to take a political lead in the last 11 years, why should we believe the coming years will be any different?"

Greenpeace described the new strategy as "visionary", but the environment group warned that ministers had promised much before and had so far failed to deliver.

John Sauven, the group's executive director, said: "If the government actually means it this time, then Britain will become a better, safer and more prosperous country. We could create jobs, reduce our dependence on foreign oil and use less gas, and in the long run our power bills will come down. But it won't happen without real government action."

Philip Wolfe, the executive director of the Renewable Energy Association, said: "Government have produced an energy strategy, not just an electricity strategy. This shows a new maturity in approach, getting away from the soundbite policy-making of the past and looking carefully at the role of renewables in buildings, heat, and transport.

"The key missing factor is a greater sense of urgency. We have only 12 years left and government still wants to use two of those talking about it."

Martin Temple, the chairman of the Engineering Employers' Federation, said: "Moving to a low-carbon economy will create significant business opportunities for the UK, but we will need to move quickly and decisively. Businesses around the world are alive to the massive opportunities and a number of governments are making their exploitation a national priority."

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