Hello sunshine
The answer to the world’s energy problems has always seemed to be blindingly obvious. Shining up above us is the ultimate sustainable energy source – enough sunlight falls on the Earth every day to meet the world’s current energy needs for four to five years, if we can just figure out how to harness it.
For decades, research efforts have focused on the use of photovoltaic (PV) cells, which convert solar energy directly into electricity. Costly to produce and relatively inefficient, it’s only recently that they’ve approached financial viability as an alternative power source. Even now, they are used primarily for domestic power generation – the world’s largest PV plant is in Erlasee/Arnstein, Germany, and only has the capacity to produce 12 megawatts (MW) of power.
Difficulties surrounding the storage of power for use during the night and when cloudy days reduce output have also reduced the viability and popularity of PV power plants.
Now, a growing number of engineers and environmentalists think that the limitations of PV plants have overshadowed a simpler, cheaper method known as concentrating solar power (CSP). As its name suggests, CSP plants use mirrors tilted towards the sun to concentrate its rays onto a small area. The mirrors, which can number in the hundreds or even thousands, are connected to a computer that’s programmed to slowly move them so that they follow the sun’s path across the sky.
The focused sunlight produces extremely high temperatures (from 400°C to more than 1,000°C), enabling the production of steam, which is then used to drive turbines, in much the same way as traditional coal-fired or nuclear power stations. One variation employs a central tower and pipes that are connected to a boiler; another that is currently being tested uses a gas turbine followed by a steam turbine. The energy produced can be stored in tanks of melted salts, building up a bank of dispatchable power.
According to Neil Crumpton, Friends of the Earth’s energy campaigner, forecasts suggest that CSP will be ‘significantly cheaper and more cost-effective than PV solar power, unless there is a significant reduction in PV costs’, and that ‘the raw materials needed to build CSP plants are abundant, essentially non-toxic and cheap. A CSP plant can be built by a largely low-skilled workforce and can be up and running relatively quickly.’
Shining examples
The technology is already proven – several thousand Californians have been relying on CSP plants in the Mojave Desert for electricity since 1985 – but it hasn’t been widely commercially viable until now.
The turning point came in March last year, with the introduction of the EU’s first commercial CSP plant. The 11-megawatt (MW) facility, known as PS10 and located near Seville in southern Spain, comprises 624 mirrors and, according to operator Abengoa, will prevent the emission of 18,000 tonnes of CO2 per year.
Abengoa says that PS10 will be part of a larger 300MW project, known as the Sanlucar la Mayor Solar Platform. The company hopes that the combined facility will be operational by 2013, at which time it will be capable of supplying all of Seville’s power needs.
According to Felipe and Javier Benjumea, co-chairmen of Abengoa, ‘[The solar platform] is a clear reflection of Abengoa’s trust in the energy of the future, its respect for the environment, natural resources and the fight against climate change: this project will prevent the emission of more than 600,000 tonnes of CO2 into the atmosphere per year.’
PS10 is the first of several CSP plants that are being planned and built in countries located within the world’s so-called ‘sun belts’. Ten new plants are planned for land near the Spanish town of Merida, and Italy and Israel are also preparing their first operations. Australia, considered one of the world’s best locations for solar power, is planning a joint CSP and PV plant in outback Victoria. The 154MW project will provide power for 45,000 homes – just a fraction of what Australia could potentially produce.
Even the oil-rich Arab emirate of Abu Dhabi, mindful of the fact that its reserves of black gold are finite, is currently evaluating the potential of a number of large-scale CSP projects. And back in the CSP heartland of California, companies and engineers from Australia, Germany, Israel and Spain are scouting desert sites for future facilities.
A bright future
The big push for CSP has come largely from an international group of scientists and engineers called the Trans-Mediterranean Renewable Energy Cooperation (TREC) and two recent reports commissioned for the German government. One of these, the TRANS-CSP report, demonstrates that Europe could use CSP to meet all of its electricity needs and cut CO2 emissions from electricity generation by 70 per cent by the year 2050, allowing for the complete phasing out of nuclear power.
‘Every year, each square kilometre of desert receives solar energy equivalent to 1.5 million barrels of oil,’ explains Dr Franz Trieb, a senior researcher at the DLR-Institute of Technical Thermodynamics in Stuttgart and the report’s project manager. ‘Multiply that by the area of deserts worldwide, and it means several hundred times the world’s entire current energy consumption.
‘It has been estimated that an area of hot desert of 110 kilometres by 110 kilometres covered with CSP plants would meet all of Europe’s electricity needs,’ Trieb continues. ‘Less than one per cent of the world’s hot deserts could, in principle, provide the world’s entire electricity needs.’
The TRANS-CSP report calculates that the cost of collecting solar thermal energy equivalent to one barrel of oil is about US$50 (a barrel of oil, meanwhile, costs US$90). That figure should eventually come down to around US$20. ‘We have calculated that solar electricity imported to Europe would be among the cheapest sources of electricity, and that includes the cost of transmitting it,’ says Trieb. ‘Also, CSP imports would be much less vulnerable to interruption than current imports of gas, oil and uranium.’
Engineer Dr Gerry Wolff, coordinator of the group’s UK wing, describes CSP as the ‘sleeping giant of future energy supplies for Europe, the Middle East and North Africa’.
‘The science behind CSP is proven,’ he says, ‘and it has been operating successfully in California for several years. It’s clean, green and a lot of it is on our doorstep. We all know how sunny it gets for months on end in southern Europe, the Middle East and North Africa, even in the winter. CSP can harness that free fuel and can make a useful contribution to cutting world emissions of CO2.’
The European supergrid
In order to be truly commercially viable, CSP plants need to be in hot, sunny desert regions, many of which are remote and lacking in infrastructure. Consequently, there is the question of how to get the power from, say, the Sahara to the huge customer bases in Europe. This could be done, say Trans-Mediterranean Renewable Energy Cooperation (TREC) scientists, via a network or ‘supergrid’ of high-voltage direct current (HVDC) transmission lines.
These power lines look much like the familiar alternating current lines that currently criss-cross the countryside, but have much lower transmission losses. TREC’s TRANS-CSP report calculated that using HVDC, ‘transmission losses are only about three per cent per 1,000 kilometres. In round figures, this means that electricity may be transmitted from North Africa to London with less than ten per cent loss of power.’ In comparison, the energy losses associated with transmission of electricity from coal-fired power stations can run as high as 50–70 per cent.
‘Ninety per cent of the world’s population lives within 2,700 kilometres of a hot desert and can receive solar electricity from there via HVDC transmission lines,’ says TREC engineer Dr Gerry Wolff. Work on the transmission network has already started, with the total cost estimated at around €45billion (£33billion).
Fringe benefits
The waste heat created from CSP power generation can be used to desalinate large quantities of seawater – up to 40 litres per kilowatt-hour. Because many of the best sites for CSP plants are in arid regions that suffer from chronic water shortages, this could help to alleviate drought.
These same regions are virtually useless for agriculture, but the hectares of mirrors will produce hectares of shade. ‘Couple these two advantages, and there is the potential for areas of, for example, Libya, Algeria or even southern Spain that have been agriculturally barren for centuries to become workable,’ says Dr Gerry Wolff. ‘There is huge potential for a large new horticultural industry using the shade and desalinated seawater. It could help poorer countries become more self-sufficient.’
March 2008
For decades, research efforts have focused on the use of photovoltaic (PV) cells, which convert solar energy directly into electricity. Costly to produce and relatively inefficient, it’s only recently that they’ve approached financial viability as an alternative power source. Even now, they are used primarily for domestic power generation – the world’s largest PV plant is in Erlasee/Arnstein, Germany, and only has the capacity to produce 12 megawatts (MW) of power.
Difficulties surrounding the storage of power for use during the night and when cloudy days reduce output have also reduced the viability and popularity of PV power plants.
Now, a growing number of engineers and environmentalists think that the limitations of PV plants have overshadowed a simpler, cheaper method known as concentrating solar power (CSP). As its name suggests, CSP plants use mirrors tilted towards the sun to concentrate its rays onto a small area. The mirrors, which can number in the hundreds or even thousands, are connected to a computer that’s programmed to slowly move them so that they follow the sun’s path across the sky.
The focused sunlight produces extremely high temperatures (from 400°C to more than 1,000°C), enabling the production of steam, which is then used to drive turbines, in much the same way as traditional coal-fired or nuclear power stations. One variation employs a central tower and pipes that are connected to a boiler; another that is currently being tested uses a gas turbine followed by a steam turbine. The energy produced can be stored in tanks of melted salts, building up a bank of dispatchable power.
According to Neil Crumpton, Friends of the Earth’s energy campaigner, forecasts suggest that CSP will be ‘significantly cheaper and more cost-effective than PV solar power, unless there is a significant reduction in PV costs’, and that ‘the raw materials needed to build CSP plants are abundant, essentially non-toxic and cheap. A CSP plant can be built by a largely low-skilled workforce and can be up and running relatively quickly.’
Shining examples
The technology is already proven – several thousand Californians have been relying on CSP plants in the Mojave Desert for electricity since 1985 – but it hasn’t been widely commercially viable until now.
The turning point came in March last year, with the introduction of the EU’s first commercial CSP plant. The 11-megawatt (MW) facility, known as PS10 and located near Seville in southern Spain, comprises 624 mirrors and, according to operator Abengoa, will prevent the emission of 18,000 tonnes of CO2 per year.
Abengoa says that PS10 will be part of a larger 300MW project, known as the Sanlucar la Mayor Solar Platform. The company hopes that the combined facility will be operational by 2013, at which time it will be capable of supplying all of Seville’s power needs.
According to Felipe and Javier Benjumea, co-chairmen of Abengoa, ‘[The solar platform] is a clear reflection of Abengoa’s trust in the energy of the future, its respect for the environment, natural resources and the fight against climate change: this project will prevent the emission of more than 600,000 tonnes of CO2 into the atmosphere per year.’
PS10 is the first of several CSP plants that are being planned and built in countries located within the world’s so-called ‘sun belts’. Ten new plants are planned for land near the Spanish town of Merida, and Italy and Israel are also preparing their first operations. Australia, considered one of the world’s best locations for solar power, is planning a joint CSP and PV plant in outback Victoria. The 154MW project will provide power for 45,000 homes – just a fraction of what Australia could potentially produce.
Even the oil-rich Arab emirate of Abu Dhabi, mindful of the fact that its reserves of black gold are finite, is currently evaluating the potential of a number of large-scale CSP projects. And back in the CSP heartland of California, companies and engineers from Australia, Germany, Israel and Spain are scouting desert sites for future facilities.
Start the slideshow (5 pictures)
A bright future
The big push for CSP has come largely from an international group of scientists and engineers called the Trans-Mediterranean Renewable Energy Cooperation (TREC) and two recent reports commissioned for the German government. One of these, the TRANS-CSP report, demonstrates that Europe could use CSP to meet all of its electricity needs and cut CO2 emissions from electricity generation by 70 per cent by the year 2050, allowing for the complete phasing out of nuclear power.
‘Every year, each square kilometre of desert receives solar energy equivalent to 1.5 million barrels of oil,’ explains Dr Franz Trieb, a senior researcher at the DLR-Institute of Technical Thermodynamics in Stuttgart and the report’s project manager. ‘Multiply that by the area of deserts worldwide, and it means several hundred times the world’s entire current energy consumption.
‘It has been estimated that an area of hot desert of 110 kilometres by 110 kilometres covered with CSP plants would meet all of Europe’s electricity needs,’ Trieb continues. ‘Less than one per cent of the world’s hot deserts could, in principle, provide the world’s entire electricity needs.’
The TRANS-CSP report calculates that the cost of collecting solar thermal energy equivalent to one barrel of oil is about US$50 (a barrel of oil, meanwhile, costs US$90). That figure should eventually come down to around US$20. ‘We have calculated that solar electricity imported to Europe would be among the cheapest sources of electricity, and that includes the cost of transmitting it,’ says Trieb. ‘Also, CSP imports would be much less vulnerable to interruption than current imports of gas, oil and uranium.’
Engineer Dr Gerry Wolff, coordinator of the group’s UK wing, describes CSP as the ‘sleeping giant of future energy supplies for Europe, the Middle East and North Africa’.
‘The science behind CSP is proven,’ he says, ‘and it has been operating successfully in California for several years. It’s clean, green and a lot of it is on our doorstep. We all know how sunny it gets for months on end in southern Europe, the Middle East and North Africa, even in the winter. CSP can harness that free fuel and can make a useful contribution to cutting world emissions of CO2.’
The European supergrid
In order to be truly commercially viable, CSP plants need to be in hot, sunny desert regions, many of which are remote and lacking in infrastructure. Consequently, there is the question of how to get the power from, say, the Sahara to the huge customer bases in Europe. This could be done, say Trans-Mediterranean Renewable Energy Cooperation (TREC) scientists, via a network or ‘supergrid’ of high-voltage direct current (HVDC) transmission lines.
These power lines look much like the familiar alternating current lines that currently criss-cross the countryside, but have much lower transmission losses. TREC’s TRANS-CSP report calculated that using HVDC, ‘transmission losses are only about three per cent per 1,000 kilometres. In round figures, this means that electricity may be transmitted from North Africa to London with less than ten per cent loss of power.’ In comparison, the energy losses associated with transmission of electricity from coal-fired power stations can run as high as 50–70 per cent.
‘Ninety per cent of the world’s population lives within 2,700 kilometres of a hot desert and can receive solar electricity from there via HVDC transmission lines,’ says TREC engineer Dr Gerry Wolff. Work on the transmission network has already started, with the total cost estimated at around €45billion (£33billion).
Fringe benefits
The waste heat created from CSP power generation can be used to desalinate large quantities of seawater – up to 40 litres per kilowatt-hour. Because many of the best sites for CSP plants are in arid regions that suffer from chronic water shortages, this could help to alleviate drought.
These same regions are virtually useless for agriculture, but the hectares of mirrors will produce hectares of shade. ‘Couple these two advantages, and there is the potential for areas of, for example, Libya, Algeria or even southern Spain that have been agriculturally barren for centuries to become workable,’ says Dr Gerry Wolff. ‘There is huge potential for a large new horticultural industry using the shade and desalinated seawater. It could help poorer countries become more self-sufficient.’
March 2008
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