CO2 capture-and -storage project

The Sleipner field is in the North Sea, about 250 km (155 mi) west of Stavanger, Norway. It is operated by Statoil, Norway’s largest oil company. The Sleipner field produces natural gas and condensate (light oil) from the Heimdal sandstones, which are about 2,500 m (8,200 ft) below sea level. Natural gas is a mixture of gases. It is typically at least 90% methane, plus other hydrocarbons such as ethane and propane. Natural gas often also contains gases such as nitrogen, oxygen, and carbon dioxide; sulfur compounds; and water. Gas containing small volumes of these impurities can still be used as fuel, but gas with high volumes of them cannot be burned efficiently and safely.

The natural gas produced at Sleipner contains unusually high levels (about 9%) of carbon dioxide (CO2), but the customers buying the gas from Statoil need less than 2.5%.

A special platform, Sleipner-T, has been built to support a 20-m-high (65-ft), 8,000-ton treatment plant that separates CO2 from the natural gas. The Sleipner-T plant produces about 1 million tons of CO2 per year.

To encourage companies to reduce their carbon emissions, the Norwegian government imposes a carbon tax equivalent to about $50 per ton of CO2 released into the atmosphere. To avoid paying this tax, and as a test of alternative technology, all of the CO2 extracted since 1996, when gas production started at Sleipner, has been pumped back deep underground.

 It is not put back where it came from, because that would further contaminate the natural gas. Instead, it is put into a 200-m-thick (650-ft) sandstone layer called the Utsira formation, about 800 m (2,600 ft) beneath the bottom of the North Sea. The Utsira formation contains no commercial oil or gas; like most rocks deep underground, it is filled with salt water. The Utsira formation has high porosity and permeability, so the CO2 moves rapidly sideways and upward through the rock layer, replacing the water between the sand grains.

It is estimated that it would take about 600 billion tons of CO2 to fill all the pore space of the Utsira sandstone. That is equivalent to all the human-made CO2 production for over 20 years, at current rates. It is likely that CO2 sequestration will continue at Sleipner long after the abandonment of the field as a hydrocarbon producer. The Utsira formation is just one of many similar deep saline aquifers around the world that could be used to help slow down or reverse the rate at which CO2 and other greenhouse gases are released into the atmosphere.

The Sleipner project is the first commercial example of CO2 storage in a deep saline aquifer, so there is a lot of interest from around the world in its success. In particular, scientists want to know how the CO2 moves inside the aquifer and if there is a risk that it could escape back to the surface.

Carbon dioxide capture, transport and storage technologies

Carbon dioxide capture and storage (CCS) in geological formations is a potentially important climate change mitigation measure in the coming decades, as geological formations can store large amounts of CO2 (as well as other gases or liquids) for thousands of years. However, CCS has not been widely used to date. The largest CO2 storage project to date (at the Sleipner field in the North Sea) has been injecting approximately 1 million tonnes of CO2 per year since 1996 into a saline formation.

         

CO2 emissions are produced from a wide variety of combustion-related and industrial processes sources.CO2 emissions from large point sources, such as power plants, refineries or cement plants, could be captured, transported and stored in several different ways.The technologies used within each step of the carbon dioxide capture and storage chain are at different stages of development. Some are mature/widely applied; some are economically feasible in some conditions, while other technologies are at the demonstration phase. Geological CCS projects (developed as CDM projects, or not) could involve   different combinations of capture, transportation and storage technologies. In turn, this could lead to a wide range of potential CDM project types.

 

CO2 capture already occurs in some energy and industrial activities. For example, CO2 separation routinely occurs in industries where CO2 is required as an input to a manufacturing process (e.g. production of urea). CO2 must be stripped from natural gas during exploitation of fields with significant CO2 content. CO2 is also extracted in refineries, ammonia plants and hydrogen plants.

 

“Pre-combustion” separation of CO2 can occur during the partial combustion of fossil fuels, used for example in the production of hydrogen or hydrogen-rich fuels. Electricity generation from Integrated Gasification Combined Cycle (IGCC) plants also requires pre-combustion separation of CO2.

 

“Postcombustion” CO2 capture from flue gases is also possible, e.g. via absorption or flue gas treatment (IPCC 2005). This can be used to capture CO2 from electricity generation plants (and indeed is the only option for CO2 capture from existing power plants), although it is energy-intensive and so entails an energy penalty. Oxyfuel combustion refers to a technology under development whereby fuel is combusted in oxygen and re-circulated flue gas, rather than air (which is mainly made up of nitrogen). The exhaust gases from oxyfuel combustion contains thus mainly CO2 and H2O (water vapour), rather than nitrogen. As the vapour can be easily condensed, the waste gas is largely CO2.

 

Transport of CO2 can be done by pipeline or ship. Commercial-scale transport of CO2 via pipeline and ship/tankers already occurs (IPCC 2005). Pipeline transport is normally of compressed (gaseous) CO2, whereas transport on ships is often of liquefied CO2, as this takes less volume. Liquefaction of gases is routinely used, e.g. for the transport of liquefied petroleum gas (LPG) or liquefied natural gas (LNG).

 

There are also different ways in which CO2 can be stored. These include various underground geological formations such as oil and gas fields (in use or abandoned), saline formations or coal seams (mineable or unmineable). Experience with storing CO2 in these types of formations varies. For example, the largest CO2 storage project to date (at the Sleipner field in the North Sea) has been injecting approximately 1 million tons of CO2 per year since 1996 into a saline formation. Other demonstrations, pilot or commercial projects, exist to inject CO2 into depleted gas fields and coal mines.

 

CO2 is being re-injected into various oil fields to increase the rate and amount of oil produced. Such enhanced oil recovery (EOR) can also use other fluids for the same purpose, notably water and steam.

 

Globally, CO2-based EOR projects inject around 40 million tonnes of CO2 per year – of which 30 million come from natural underground sources of CO2 and about 10 million tonnes is captured from industrial  plants. The use of CO2 for EOR can provide a valuable near-term opportunity for gaining storage  experience, but this needs to be done at the right time in the life of a particular field. Enhanced gas recovery and enhanced coal bed methane recovery are in development phase.

Water use for electricity generation

IEEE Spectrum: How Much Water Does It Take to Make Electricity?

TAPPING SOLAR ENERGY

India is a sunny country with a solar energy potential of 20 mw every square km. At present, only a tiny fraction of it is being tapped. Solar energy can be used directly in two forms – producing heat or light. Production of light and electric current from the sun’s rays uses ‘photovoltaic technology’, which involves direct conversion of sunlight into electricity.The thermal form, which is used for cooking, water heating or purification, drying and fruit ripening, distillation or producing steam for power generation, is more economical. Solar cookers are already well-known and popular. Solar cooking has been recommended even in the Rig Veda which says: ‘All edibles ripened or cooked in the sun’s rays change into super medicine, the amrita”.  Solar energy has every thing to recommend it. Unlimited and non-polluting. It will neither drain our mineral resources nor submerge large tracts under dam waters. If only it could be tapped cheaply. That is what technicians are trying to do the world over.

New Schemes

            The Ministry of New and Renewable Energy supports Research, Design and Development (RD&D) activities in New and Renewable Energy including solar energy in the country. Comprehensive guidelines for supporting and accelerating pace of Research, Design and Development leading to eventual manufacture and deployment of various Renewable Energy Systems including solar energy have been put in place.

An amount of Rs. 600 crore has been tentatively allocated for Research, Design and Development in  the Energy Sector for the 11th Five Year Plan. During the last Five Year Plan period, Rs. 72.65 crore were spent for the same activities.  The Ministry has financially sported about 600 RD&D Projects particularly in  Solar Energy Sector.

 New  schemes have been launched  by  the Ministry  in addition to implementation of ongoing schemes to encourage large-scale use of solar energy in the country during the 11th Five Year Plan Period. The new schemes include ‘Development of Solar Cities’ and ‘Demonstration Programme on MW size Grid Solar Power Generation’. In addition, Research and Development thrust areas for solar and other New and Renewable Energy Technologies for the 11th Five Year Plan period have also been identified and publicised through newspaper and website advertisements for further intensifying research and technology development in this area. Promotional measures taken by the Government and other associated agencies include publicity and awareness campaigns, amendment of building bye-laws for making the use of solar water heaters mandatory in certain categories of buildings, rebate in property tax/electricity tariff to the users of solar water heaters, etc.

Solar Energy Plants

            The Ministry of New & Renewable Energy promoted deployment of nine Solar Energy Plants during 2007-08 in six States of the Country. Out of this, Maharashtra tops the list with three Plants where as Jammu & Kashmir got two such Plants. Chhattisgarh, Haryana, Orissa and West Bengal each got one power plant during this period. The total capacity sanctioned for these plants is less than 2000 kwp. The capacity under implementation is more than 800 kwp.

            Out of different Plant Projects, all the six States have received one Solar Photovoltaic Power Plant Project. The State of West Bengal has been sanctioned highest capacity of 945.0 kwp followed by Chhattisgarh with  646.8 kWp. Besides these Jammu & Kashmir and Maharashtra, each have been sanctioned Building Integrated Power Plants (BIPV) with total sanctioned capacity of 18 kWp and one each SPV Power Pack of total sanctioned capacity of 8 kWp.

            The Ministry is promoting deployment of solar photovoltaic power packs/plants in different parts of the country under various programmes including remote village electrification programme by providing partial financial support. These projects are implemented through the state implementing agencies in their respective states.  The total funds released to the state agencies are to the tune of Rs. 40 crore which includes funds for four ongoing projects also. These projects are likely to be completed during 2008-09.

The projects for installation of solar photovoltaic power packs/plants are considered by the Ministry on the basis of proposals submitted by the States, as per provisions of the scheme and availability of funds.

            Non-polluting, requiring little maintenance, free from wear and tear caused by moving parts, solar power is the most promising form of energy for the future.

Total 33 grid interactive solar photovoltaic power plants installed Electricity production to reach 2.55 million units in a year

A total of 33 grid interactive solar photovoltaic power plants have been installed in the country with financial support from the Government. These plants, with aggregate capacity of 2.12 Megawatt, are estimated to generate about 2.55 million units of electricity in a year. In addition, around 14.5 lakh decentralized off-grid solar photovoltaic systems aggregating to about 125 Megawatt capacity have been installed in the country, which is capable of generating about 150 million units in a year. Further, a collector area of about 2.15 million square meter has been installed for solar water heating applications. The amount of energy generation depends on the use pattern of the system and climate of the place. Typically, a solar water heating system with 2 square meter of collector area can generate energy equivalent to up to 1500 units of electricity when the system is used for about 300 days in a year.

The Government has taken several measures to reduce the cost of solar energy systems, which include: (i) research and development to improve their performance and reduce the consumption of materials, (ii) subsidy on selected solar energy systems; (iii) interest subsidy to provide soft loan to users and the manufacturers; (iv) concessional or nil import duty on some of the raw materials, components and products; (v) excise duty exemption; and (vi) 80% accelerated depreciation in the first year etc

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Many incentive have been given to private agencies for research and generation of solar energy. All academic, research institutions and industries, including the private institutions are engaged in research in solar energy. They are eligible to receive grant for undertaking R&D. In addition, expenditure on R&D by the private industries is eligible for deduction from profits under Income Tax Act

.

Under grid interactive solar power generation, private companies are eligible to get production based incentive for power fed to the grid from megawatt capacity solar power plants set up on build own and operate basis in the country.

 

Proposal from any project developer with a maximum aggregate capacity of 5 MW, either through a single project or multiple projects of a minimum capacity of 1 MW each, are being considered under the programme. Preference is given to the projects from the States where the State Electricity Regulatory Commissions (SERCs) have announced or are in the process of announcing tariff for solar power.

For projects approved and commissioned by 31st December, 2009, the Ministry will provide generation based incentive up to Rs.12 per kWh for solar photovoltaic power and Rs.10 per kWh for solar thermal power after taking in to account the tariff provided by the SERC or the utility.

 

The Sun powers (almost) everything

When we talk about Solar Power, we are really talking about direct solar power. Using the sun’s heat to heat our homes or light to produce electricity. When you think about it, the Sun actually powers almost everything we do either directly or indirectly.

With the exception of Nuclear energy, all of our energy comes from the Sun. All of the oil, gas, and coal we burn is carbon based energy that was converted by photosynthesis and stored in short hydrocarbon chains, ready to be broken down by combustion and combined with Oxygen to form water vapor, CO₂ and heat.

The bond between Carbon and Oxygen is so strong that a lot of energy is given off during the chemical reaction (combustion) when the atoms combine to form CO₂. Conversely, to break the CO₂ molecule back into Carbon and Oxygen requires a lot of energy. That is where the sun comes in.

Our Sun

Our Sun is about 93,000,000 million miles away. It takes light leaving the sun 8.31 seconds to reach Earth. The Sun’s diameter is about 870,000 miles, compared to Earth which is about 7,900 miles. The rate of the Sun’s energy striking Earth is called insolation. The average rate of insolation on the surface of the Earth is 250 watts per square meter. This takes into consideration the North and South poles, inclement weather and night time periods. When the sun is shining, the average insolation for any given location is about 1,000 watts per square meter.

Here is a little perspective. Currently, we (the human race) consume 15 TW (terawatts, one terawatt equals 1,000,000,000,000 watts) of power at any given moment. The energy from the Sun striking the Earth is 89,000 TW.

There are, of course, a few details. We cannot cover the entire surface of the Earth with solar collectors.

1. Water covers 70 percent of our planet. Which means that 30 percent of the energy from the sun strikes land areas. 89,000 TW x 0.30 = 26,700 TW available.
2. Mountainous terrain (too difficult to build on) covers about 10 percent of the land area, that leaves 90 percent available for use, or 26,700 TW x 0.90 = 24,030 TW
3. Roughly 9 percent of the land area is Antarctica, which is uninhabited. 24,030 TW x 0.91 = 21,867.3 TW available for use.
4. Lets assume that roughly 5 percent of the remaining land area would be able to be developed into solar power installations (includes roof top installations). 21,867.3 TW x 0.05= 1,093.4 TW

Then there is the matter of conversion efficiency.

1. Currently Photovoltaic efficiencies (technologies actually in production) are at most 16 percent. 1,093.4 TW x 0.16 = 175 TW

There are 175 TW of practical solar power available for our use. This gives us more than enough room to grow. Additionally, some of the solar power that strikes the oceans and other water areas. This energy creates wind, evaporates water and generates waves. It is currently being used for wind turbines, hydro power and so on. There is also a big push to develop wave and tidal power. These applications would further enhance the amount energy we directly use from the Sun.

The long and the short of it; there is plenty of energy for everyone provided we use our technology to develop that potential and stop trying to blow each other up.

 

Whatever Happened to Solar Power?

Solar energy is the light alternative to a carbon-rich energy diet, and it may be the only renewable energy that can significantly reduce greenhouse gas emissions, engineers say.

“Wind can play some role, as can biofuels and geothermal, but they are all too small,” said Erin Baker of the University of Massachusetts Amherst. “The three really big players are solar energy, nuclear power and carbon capture and storage .”

Over the course of a day, the amount of energy in sunlight striking the continental United States is more than 2,500 times the amount of the nation’s daily electricity consumption. Despite this potential, solar power is far behind other renewables, making up just 0.07 percent of the U.S. energy portfolio, according to the Department of Energy.

“Solar energy would have to provide 20 percent of the energy supply to have a climate change impact,” Baker told LiveScience. “We’d like it to be more than that.”

In a report released earlier this year, Baker and her colleagues looked at the technologies that might bring solar out into the full light.

Sand in demand

Solar panels contain photovoltaic cells that turn light into electricity without releasing any greenhouse gases. One of the attractive features of solar panels is that they can be relatively easily added to a home, as opposed to the bigger construction projects typically associated with wind turbines or other energy-gathering setups.

Almost all cells in current use are made of silicon. Although silicon is abundant in sand, it must be processed to make it usable in solar cells and computer chips. In fact, the current high demand from the electronics industry for silicon wafers has caused a shortage of high-grade silicon, which means the solar industry could have even more trouble trying to become competitive.

For a typical home’s electricity needs, the cost of solar panels is several tens of thousands of dollars. Over the lifetime of the panels, this works out to about 30 cents per kilowatt hour, three times what most utilities charge.

To reduce this price, much of the current engineering effort is focused on making solar cells from thin films that either use less silicon or replace it with other photovoltaic materials. Baker said that many experts think this should be the first goal of research and development.

“We could fund a lot of people to look for other materials,” she said.

Solar on the horizon

There are other ideas as well, such as organic solar cells based on cheap, flexible plastic. However, organic cells are currently inefficient at converting sunlight into electricity, and what’s worse, said Baker, “they tend to fade and breakdown in the sun.”

Some researchers are working on future “third generation” solar cells, which could employ a number of new technologies, such as lenses, chemical dyes, multi-layer cells or tiny quantum dots that trap more of the incoming sunlight.

But even if highly efficient solar panels could be made cheaply, they can’t make electricity at night or on a cloudy day.

“The biggest problem for solar is the intermittency of supply,” Baker said.

For solar to be a major energy provider, there will need to be better electricity storage. Giant flywheels or improved batteries could help smooth out the power flow.

Diversify

None of the technological options are sure to work, so Baker thinks policy makers and the solar industry should fund research into several possibilities, much like a diversified stock portfolio.

“You don’t invest all your money in Google; instead you buy 10 or 100 different stocks,” she said.

Interestingly, Google just announced plans to invest tens of millions of dollars next year in the development of a gigawatt of power from renewables, enough to supply roughly a million households. One of the companies selected by Google is eSolar Inc., which specializes in solar thermal power.

Solar thermal technology “provides a very plausible path to providing renewable energy cheaper than coal,” said Larry Page, Google co-founder and president of products, in a company statement.

Solar thermal is different from photovoltaic technology, in that the sun’s energy is focused to boil water or another fluid. The resulting steam can then be used to turn a generator as is done in traditional coal or nuclear power plants.

Although seemingly less direct than solar panels, solar thermal converts roughly 30 percent of the sun’s energy into electricity, which is twice the efficiency of most silicon-based solar cells. Moreover, some of the heat can be stored and used at night to keep the electricity supply more constant.

Several concentrated solar power plants have been built using this technology in places such as Spain and the Mojave Desert. The required sun-tracking mirrors are far too unwieldy to ever conceivably go on a person’s roof, but similar systems could be used to provide warm water for a home.

Solar Power to Rule in 20 Years, Futurists Say

By Robin Lloyd, LiveScience Senior Editor

He predicted the fall of the Soviet Union. He predicted the explosive spread of the Internet and wireless access.

Now futurist and inventor Ray Kurzweil is part of distinguished panel of engineers that says solar power will scale up to produce all the energy needs of Earth’s people in 20 years.

There is 10,000 times more sunlight than we need to meet 100 percent of our energy needs, he says, and the technology needed for collecting and storing it is about to emerge as the field of solar energy is going to advance exponentially in accordance with Kurzweil’s Law of Accelerating Returns. That law yields a doubling of price performance in information technologies every year.

Kurzweil, author of “The Singularity Is Near” and “The Age of Intelligent Machines,” worked on the solar energy solution with Google Co-Founder Larry Page as part of a panel of experts convened by the National Association of Engineers to address the 14 “grand challenges of the 21st century,” including making solar energy more economical. The panel’s findings were announced here last week at the annual meeting of the American Association for the Advancement of Science.

Solar to compete in five years

Solar and wind power currently supply about 1 percent of the world’s energy needs, Kurzweil said, but advances in technology are about to expand with the introduction of nano-engineered materials for solar panels, making them far more efficient, lighter and easier to install. Google has invested substantially in companies pioneering these approaches.

Regardless of any one technology, members of the panel are “confident that we are not that far away from a tipping point where energy from solar will be [economically] competitive with fossil fuels,” Kurzweil said, adding that it could happen within five years.

The reason why solar energy technologies will advance exponentially, Kurzweil said, is because it is an “information technology” (one for which we can measure the information content), and thereby subject to the Law of Accelerating Returns.

“We also see an exponential progression in the use of solar energy,” he said. “It is doubling now every two years. Doubling every two years means multiplying by 1,000 in 20 years. At that rate we’ll meet 100 percent of our energy needs in 20 years.”

Other technologies that will help are solar concentrators made of parabolic mirrors that focus very large areas of sunlight onto a small collector or a small efficient steam turbine. The energy can be stored using nano-engineered fuel cells, Kurzweil said.

“You could, for example, create hydrogen or hydrogen-based fuels from the energy produced by solar panels and then use that to create fuel for fuel cells, he said. There are already nano-engineered fuel cells, microscopic in size, that can be scaled up to store huge quantities of energy, he said.

Other grand challenges

The NAE panel thinks that meeting the energy challenge and the other grand challenges of the 21st century is “simply imperative to our survival on the planet,” said panel member Charles Vest, former president of MIT and current NAE president. Other challenges that the panel addressed include providing access to clean water , engineering better medicines, reverse engineering the brain, securing cyberspace and enhancing virtual reality.

The inspiration for the report was a previous NAE that reflected on the engineering achievements of the 20th century, such as the automobile, aircraft, jet aircraft, rockets, missiles, satellites, radio, radar, television, nuclear power, nuclear weapons, the computer, internet, genetic engineering and antibiotics.

These inventions gave us the green revolution that improved food production as global population grew, the distribution of safe water and electricity, improved health and generated an improved standard of living for many in the world.

However, now the world faces some dark consequences of these advances, said Stanford University’s William Perry, a member of the Grand Challenges panel and a former Secretary of Defense in President Clinton’s administration, including the depletion of prevailing energy resources, a looming global environmental disaster in global warming, the emergence of drug-resistant bugs and the threat of a security disaster if nuclear and biological weapons fall into the wrong hands.

With this in mind, the NAE brought together the panel (other members included Segway inventor Dean Kamen, biomedical engineer Robert Langer, former National Institutes of Health Director Bernadine Healy and genomics pioneer Craig Venter) to report on the needs of society and how technology can meet them.

More solutions to 21st century challenges

Other tech solutions suggested by the NAE panel to the new century’s big challenges include:

·                           Better detection and monitoring of nuclear weapons components to prevent them from getting in the hands of terrorists.

·                           Improving rapid responses to possible bioweapons attacks.

·                           Advances in genetic engineering to address the problem of drug-resistant viruses and bacteria, and to create personalized medicine.

·                           Desalinization and water filtering to address the shortage of potable drinking water.

·                           Tutoring computers to help meet education needs.

·                           Artificial intelligence that better simulates the brain to help create faster computers and also to aid in the treatment of neurological disorders

Perry was optimistic about the ability of society to arrive at these solutions, saying the achievements of the 21st century “will I believe be just as spectacular as achievements of 20th century.”

Panel member Calestous Juma of Harvard University, an authority on using science and technology to promote sustainable development, said the policy implications of the 21st century challenges plan reveal a “more enlightened understanding of role of science and technology in general.”

“This idea [of solving large-scale problems using technological innovation] is being developed in the context of a globalized world,” he said. “Even though the proposals have been developed in the United States, the challenges themselves that humanity faces are global in character.”

 

 

Energy from Space-Based, Solar-Lasers

There are two new studies ongoing with the aim to investigate the feasibility of generating solar energy from solar panels borne by satellites. I can see the reasoning here: at the top of the atmosphere, the amount of the Sun’s radiation falling onto the Earth amounts to about 1,400 W/m^2 (Watts per square meter); however, the air-molecules absorb various wavelengths of light and so at any point at ground level, the intensity of radiation is attenuated. In northern Europe a reasonable estimate is around 150 W/m^2, somewhere quite sunny it is about 350 W/m^2 and in the Sahara Desert the energy is not far short of 1,000 W/m^2. Hence, out in space the full complement of the Sun’s power might be harvested.

In this particular concept being explored, a network of orbiting satellites would serve as energy transducers, capturing the abundance of energy from the Sun and sending it down to Earth in the form of a laser or microwave beam. (Mmmm… I wonder what the Health and Safety people would have to say about that?) . The original notion originated in the mind of Peter Glaser, a scientist working at Arthur D. Little in Cambridge, Massachusetts in the late 1960’s. No one is in any doubt that there are difficulties and drawbacks attending this particular type of technology, which smacks of “Star-wars”, and it is debatable just what the real economic benefit would be in practice.

The challenges of Space Solar Power (SSP) are various, but while concluding that the launching costs were too high, NASA (in 1995) decided to take a fresh look at the technology, possibly to attract financial and public support for its future activities. Since then interest in SP has accumulated, and a special study group at the National Research Council (NRC) has singled out several technological advances, which might be worth following-up on: (a) improvements in the efficiency of solar panels and the fabrication of light-weight panels, (b) progress in wireless transmission on Earth, notably in Japan and Canada, (c) robotics, deemed essential to run such an SSP assembly, has demonstrated significant improvements in terms of manipulators, machine vision systems, hand-eye coordination, task-planning and reasoning.

The panel concluded that significant breakthroughs are necessary before SSP technologies could produce energy in a cost-competitive way compared with Earth-based power generation. The final success of generating power on Earth from satellites depends “critically on ‘dramatic reductions’ in the cost of transportation from Earth to geosynchronous orbit (i.e. the altitude at which the orbiting period of the satellite is the same as that of a point on the Earth’s surface, meaning that from an Earth-bound perspective, the satellite stays in the same place at all times… you wouldn’t want it drifting off would you?!”). It further concluded the need for ground-based demonstrations of point-to-point wireless power transmission, and also the ‘desirability’ of ground-to-space and space-to-ground demonstrations… i.e. potential “Star-Wars” weapons.

We shall see, and I would rule nothing out as the world clutches ever more desperately at means to avoid drowning in the “Oil Dearth” era.

Related Reading.
“Bright Future for Solar Power Satellites,” by Leonard David. http://www.space.co./businesstechnology/technology/solar_power

German “Combined Power”.

A group of German scientists based at the University of Kassel has carried out a pilot-study which suggests that nuclear and fossil-fuel based energy can be phased-out and substituted by renewables, without interrupting the output from the national grid. As they point-out, renewable energy has certain limitations: e.g. cloudy or windless days are no good for solar or wind-energy. However, their innovative “combined power plant” draws its energy from 36 different kinds of plant, including solar, wind, biogas and hydroelectric designs, in an effort to prove that such a mix of renewable energy can yield a consistent and reliable output of power, under a range of prevailing weather conditions and according to non-constant demand for electricity as is the reality.

This has indeed been achieved on a relatively small scale so far, enough to power 12,000 homes, or enough for a small town/village. The village of Caversham, where I live, has a population of around 9,000 inhabitants (maybe 4,000 homes), if you include the effectively accommodative developments, i.e. with no shops or other amenities, and hence are pretty much dependent on car ownership. One significant aspect of the German design is that excess energy is used to pump water uphill into a large reservoir, which can be used during times of peak demand to drive hydroelectric turbines as an additional source of energy. The ability to thus store energy is a vital component of the overall scheme to provide a constant supply.

If this approach can be scaled-up, it is calculated that a total of 448 TWh/year might be produced in Germany, which breaks down to: 37.5% from 10,000 onshore wind turbines, 26.8% from 5,000 offshore wind turbines, 13.4% from photovoltaics (covering 20% of roof surfaces)and 22.3% from biogas, involving 17% of agricultural land. It is suggested that 40% of Germany’s electricity needs could be thus met by renewables by 2020 and 100% by 2050. I append a link to the full technical report below.

A very interesting approach. Of course there is around another 40% of total energy to be found for space-heating etc. and another 40% for transportation in the form of oil, assuming that the German break-down of energy use is similar to that in the UK. However, a relocalisation of German society, as will be the case across the entire world as oil supplies begin to fail our demand for them, substantially eliminates the latter component and Germany has substantial reserves of coal, which can underpin heating etc., even if its use can be avoided in electricity generation. The scheme will doubtless require a massive investment of money, energy and other resources to expand it to the future levels of electricity provision that are proposed, but such an integrated mix of supply sources may well be the best way forward, even at a local level.

Ultimately, in order to survive, all societies will have to be sustainable in terms of energy, food and all else they consume.

Coal is Dirtier than Gas.

There is much discussion currently concerning the relative merits of coal or natural gas as a fuel. It is debatable just how much extractable coal is in the earth, and there are estimates ranging from10 trillion tonnes down to around 0.5 trillion tonnes. To put this into perspective it is thought there is around 1 trillion barrels of readily extractable crude oil, or around 0.15 trillion tonnes, and a comparable amount of natural gas that will be recovered. Coal, then still looks like a good bet in terms of its quantity.

The heat of combustion of methane (which is what natural gas is mostly) is 891 kJ/mol, which amounts to 1 x 10^6 (g/tonne)/16 (g/mol) x 891 x 10^3 = 55.69 GJ/tonne. This can be compared with around 28 GJ/tonne for coal (the figure varies according to the nature of the coal, but this is a fair estimate).

When methane burns the process can be expressed as: CH4 + 2O2 –> CO2 + 2H2O
and for coal (being largely carbon) as: C + O2 –> CO2

Thus each tonne of methane yields 44/16 = 2.75 tonnes of CO2, while each tonne of coal yields 44/12 = 3.67 tonnes of CO2.

 

But since less heat is obtained per tonne of coal than per tonne of methane, we need to burn more coal to get the same amount of heat from it, and so a relative CO2 yield per unit of heat can be derived:

3.67/2.75 x 55.69 GJ/tonne/28 GJ/tonne = 2.65, or over two and a half times as much.

Either way, using natural gas or coal, produces a lot of CO2. For example, a typical 1 GW power plant burns 3 million tonnes of coal per year or half that amount of natural gas, and produces around 11 million or 4 million tonnes of CO2, respectively. For oil-fired stations (which exist mostly in Asia but are being phased-out and converted to coal), approximate thermal values of 42 GJ/tonne are often quoted, and there are some at 45 GJ/tonne, depending on the exact nature of the oil. For comparison, a value may be obtained for n-octane (a reasonable model for oil-based refined fuel) of 47.87 GJ/tonne.

We burn around 7 billion tonnes of “carbon” annually, which ends-up as 26 billion tonnes of CO2 – of which only about half is removed by natural processes, including photosynthesis. Thus the atmospheric concentration of the gas can only increase, unless we were to reduce fossil fuel use by around 50%.

People talk much about renewables, since they are ideally sustainable and non-polluting. i.e. They don’t consume irreplaceable reserves like coal and gas and oil, or contribute to greenhouse-gas emissions, but matching the amount of them that we get through to sustain our current quality of life, by renewables is a long way off, if it can be done at all. Localised energy production, e.g. through CHP and micro-hydro generation might come some way to providing for relatively small communities, if the dearth of oil and hence transportation fuel forces civilization to take this course, but generating enough electricity to run power utilities on the scale of conventional power stations and the national grid will prove extremely challenging.