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A review of the technology for providing energy. Updated August 2010 |
Please note: the statements made on this page are an honest impression from various information on the web, but no guarantee is made for their accuracy. On this page:
Other
Technologies for Stationary Energy (i.e. electricity generation)
In this section: In comparing ways of generating electricity, there are several considerations:
I.e., can it guarantee to meet a predicted demand? At one extreme, wind is very unpredictable; at the other, hydro can be used to store energy from other sources (by pumping water back up). In between, an energy source may be reliable but inflexible, i.e. it's most efficient if you run it at constant output, or reliable and flexible ("dispatchable") but with no ability to absorb and store energy from other sources. This issue would be solved by large, cheap, efficient batteries, but there is no prospect of that any time soon.
I.e., how quickly can capacity be expanded? Given the urgency of climate change, we cannot wait 30 years for the ideal solution.
References: http://www.theglobaleducationproject.org/earth/energy-supply.php http://en.wikipedia.org/wiki/Peak_uranium Studies demonstrating the feasibility of 100% renewables: Europe: http://www.pwc.co.uk/eng/publications/100_percent_renewable_electricity.html Australia: http://media.beyondzeroemissions.org/preview-exec-sum14.pdf
In this section Wind
Electricity from wind has been around for 120 years, with commercial generation since 1941. Current costs go as low as 6 to 7 cents/kWh for the most suitable sites, making it about the same as new coal-fired, and can be expected to fall a little as the technology evolves. Its main disadvantage is unpredictability, but mixed with other technologies could provide 20% of Australia's needs. A looming technology is high-altitude windpower, which it's claimed would provide electricity at 2 to 5 cents/kWh. At the low end, domestic wind turbines don't get enough wind, but other technologies might harness low wind speeds more effectively: http://www.newscientist.com/article/dn19274-innovation-reinventing-urban-wind-power.html References: http://en.wikipedia.org/wiki/Wind_energy http://en.wikipedia.org/wiki/History_of_wind_power http://www.res-australia.com/resources/about-wind-power.aspx http://beyondzeroemissions.org/category/keywords/renewable-energy/wind-energy/large-scale-wind-power http://www.evwind.es/noticias.php?id_not=3172 http://theenergycollective.com/TheEnergyCollective/60297 June 2010: Turbine noise no health threat http://www.nhmrc.gov.au/publications/synopses/new0048.htm This concentrates the sun's rays to heat molten salts to 500oC. As needed, this is then used to generate steam to drive a turbine. Adequate salt storage and diverse sites in the grid make it suitable not just as baseload but as a flexible source to be mixed with unpredictable sources such as wind. There are two main versions: parabolic trough and power tower. Parabolic troughs have been expensive to construct. A new aluminium design helps, but still probably more expensive than power tower. Current generation cost is around 15 cents/kWh, but is expected to fall to the same or less than coal. June 2010: EU Sees Solar Power Imported From Sahara In 5 Years: http://planetark.org/enviro-news/item/58491 References: http://en.wikipedia.org/wiki/Concentrated_Solar_Power http://www.beyondzeroemissions.org/media/newswire/molten-salt-magic-ingredient-091110 http://www1.eere.energy.gov/solar/pdfs/csp_prospectus_112807.pdf
This turns light directly into electricity, avoiding the inefficiencies of a heat stage and the need for water as a coolant. That also makes it viable for domestic scale generation. However, current PV materials are still rather inefficient and can overheat, and the most efficient are very expensive. Current cost is around 20 cents/kWh, but technological advances could make this much more attractive one day. Such advances are reported almost weekly now: Feb 2010: Silicon Wire Arrays; Caltech: http://www.sciencedaily.com/releases/2010/02/100216140259.htm
March 2010: Plant protein; Tel Aviv: http://www.aftau.org/site/News2?page=NewsArticle&id=11819 Algal electrons; Stanford: http://www.newscientist.com/article/dn18666-algaes-solar-electrons-hijacked-to-steal-power.html April 2010: CoS cathode, organic redox electrolyte; Quebec: http://www.sciencedaily.com/releases/2010/04/100406125545.htm
Graphene; Indiana: http://www.eurekalert.org/pub_releases/2010-04/iu-cio040910.php Nanowires; summary: http://www.newscientist.com/article/mg20627550.300-skip-the-hard-cell-flexible-solar-power-is-on-its-way.html PbS; PennState: http://www.newscientist.com/article/dn18778-carbon-flakes-brush-up-for-cheap-solar-cells.html Continuous flow thin film; Oregon: http://www.eurekalert.org/pub_releases/2010-04/osu-ami041610.php May 2010: Purple Bacteria; Miami: http://www.upi.com/Science_News/2010/05/05/Bacteria-may-aid-solar-energy-technology/UPI-21211273076723/ Printable plastic strip cells; CSIRO: http://www.itwire.com/science-news/energy/23361-new-technology-enables-solar-cells-to-be-printed-like-money Plastic fibre cells; Wake Forest: http://www.solarserver.de/solarmagazin/news-e.html#news2113
Multilayer fabrication of thin film GaAs; University of Illinois: http://www.sciencedaily.com/releases/2010/05/100520093036.htm June 2010: Grätzel cells take Millennium Prize; Lausanne: http://en.wikipedia.org/wiki/Michael_Grätzel Quantum dots could double PV efficiency; University of Texas: http://www.eurekalert.org/pub_releases/2010-06/uota-hes061410.php Longer life unsealed plastic solar cell; University of Alberta and the National Institute for Nanotechnology: http://www.eurekalert.org/pub_releases/2010-06/uoa-lop062110.php Ultrathin cells save on silicon; Transform Solar: http://www.transformsolar.com/tech_sliver.php
August 2010: Photon enhanced thermionic emission (PETE) uses both heat and light; Stanford: http://news.stanford.edu/news/2010/august/new-solar-method-080210.html Embedding Selenium in Zinc Oxide increases capture; Lawrence Berkeley Lab, Ca.: http://www.eurekalert.org/pub_releases/2010-08/aiop-smm080310.php Nickel can replace gold in colloidal quantum dot solar cell contacts; University of Toronto: http://www.eurekalert.org/pub_releases/2010-08/aiop-nis080310.php
Self-assembled monolayer helps charge dissociation in conjugated polymers; University of Cambridge: http://www.sciencedaily.com/releases/2010/08/100817090756.htm
Chlorophyll in stromatolites captures infrared; University of Sydney: http://www.newscientist.com/article/dn19338-infrared-chlorophyll-could-boost-solar-cells.html Other References: http://www.solarserver.de/solarmagazin/news-e.html http://en.wikipedia.org/wiki/Photovoltaics http://www.renewableenergyworld.com/rea/news/article/2007/08/what-solar-power-needs-now-49617
This involves injecting water into hot rocks deep underground. The water is recycled, but other water may be used as coolant. The key cost with this is the initial drilling; the hot rocks are deeper than most mines. Cost from most suitable sites is around 7 cents/kWh. There is a worry that the injection of water may trigger earthquakes. In principle, this may only be bringing on earthquakes that would have happened one day in any event, but it remains at least a legal issue. This may rule out some sites. There may be some amount of GHGs and other undesirable gases released from underground in the process. A recent idea is to avoid drilling so deeply by choosing a place where there is a good insulating layer near the surface. It turns out that brown coal deposits are favorite! References: http://en.wikipedia.org/wiki/Geothermal_energy http://www.rnp.org/RenewTech/tech_geo.html
Biomass may be existing crop waste or purpose grown. If crop waste, the energy density is low, and the main cost is gathering it from a broad area. Traditionally, this has led to small scale combustion, which in turn results in incomplete burning and smogs (which have a powerful greenhouse effect). A better option is pelletisation, reducing the cost of transporting to a centralised furnace and allowing it to be stockpiled. If purpose grown, collection is still something of an issue, plus it may displace food crops. Either way, it is unlikely to provide more than about 10% of world demand ever. It can provide a useful backup heat source for solar thermal. References: http://en.wikipedia.org/wiki/Biomass http://www.bmu.de/english/press_releases/archive/16th_legislative_period/pm/pdf/42805.pdf See also Biofuel
The designs for collecting wave power are more varied than for any other energy source. Several years of experiments are needed to select the best. Current installations are achieving 15-20 cents/kWh, but this is expected to fall to 5-7 cents. Some estimates claim as low as 2-3 cents! In Australia, there may be limited sites producing reliable energy and close to urban centres. Even so, it has been claimed that it could supply 35% of Australia's current demand. August 2010: Wave energy hotspots around Australia References: http://en.wikipedia.org/wiki/Wave_energy http://www.rnp.org/RenewTech/tech_wave.html http://www.abc.net.au/rn/scienceshow/stories/2008/2378304.htm
Current installations are achieving 10-12 cents/kWh, but this is expected to fall to 4-6 cents. Given the high capital cost, it may surprise that the unit cost is expected to drop so. This may be because the land used is not considered of commercial value. The necessary landscaping impacts wildlife and may cause GHG emissions as with hydro. In Australia, there are few suitable sites. References: http://en.wikipedia.org/wiki/Tidal_power http://www.rnp.org/RenewTech/tech_wave.html http://www.sustainabilitycentre.com.au/TidalPowerWA.pdf
There may be significant GHG emissions from the reservoir. According to the World Commission on Dams report, where the reservoir is large compared to the generating capacity (less than 100 W/m2 of surface area) and no clearing of the forests in the area was undertaken, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant. The best sites produce very cheap electricity (about half the price of coal), but Australia already exploits most viable sites. References: http://en.wikipedia.org/wiki/Hydroelectricity
CCGT stands for Combined Cycle Gas Turbine. This is the most efficient gas-based power generation to date. While natural gas combustion has only 60% of the CO2 emissions per unit of energy as coal, it is a more expensive fuel. There are also significant question marks over the total GHG footprint, since methane leaks are inevitable. Until recently, the known reserves would only power humanity for 50 years at current demand. Vast new fields have been discovered. It is hard to judge whether this is good news or bad. On the one hand, it creates a relatively easy way to reduce emissions significantly over the next five to ten years. On the other, building the new gas-fired power stations diverts efforts from renewables, locking us into continuing emissions for an extra ten to twenty years.
References: http://en.wikipedia.org/wiki/CCGT
Carbon Capture and Storage (CCS, or "Clean coal")
In addition to the CO2 produced in combustion, some CO2 and other undesirable gases are released during mining. Capture reduces the carbon footprint 80-90%. Despite the billions invested in trials, it shows no sign of being competitive with the best renewables, whether applied to new coal plant or retrofitted to existing plant. Even if the storage is safe for a thousand years, we would be leaving posterity a legacy they'd prefer to be without. April 2010: Report says it cannot work.May 2010: Tim Flannery withdraws support
June 2010: Iceland could capture the CO2 chemically in rock July 2010: Trap the CO2 in bacteria
References: http://en.wikipedia.org/wiki/Carbon_capture_and_storage#Australia
One fossil fuel power station option is to capture carbon organically, using algae say, which can then be used as biofuel or cattle cake. There are effectively two carbon cycles on earth: on a decades scale it cycles between air, ocean, soil, and biota. Over millennia, it can be bound into minerals as rocks weather and as organic matter becomes buried instead of decaying, and released later by tectonics. Our key problem is that burning coal and oil, and manufacturing cement, rapidly move carbon back to the short cycle. Capturing it in algae does not take it back out of the short cycle unless you then bury it. And if you do that, you may as well run the power station on the algae and leave the coal in the ground. So algal capture is hardly a solution. If used as cattle cake it may reemerge as methane, and that could be worse than not having captured it at all. Of course, if the algae were to capture CO2 directly from the air and not depend on a power station then that would be excellent, but there's no suggestion that would be viable.
It is essential that we stop using this ASAP. Coal has been storing excess carbon safely for millions of years. Once we release it into circulation it will be hard to take it back out. References: http://en.wikipedia.org/wiki/Coal
While no GHGs are emitted during operation of the generator, there is a large footprint from the vast quantities of concrete needed for construction of the plant, plus the ongoing impact of mining and transporting the ore. Current nuclear power station production technology generates large quantities of radioactive waste that must be stored for centuries, some for millennia. At the same time, anticipated reserves would only meet the world's energy demand for 200 years. Fast breeder reactors, still only experimental, could reuse existing waste, produce much less waste in future, employ sources other than uranium, and so extend the resource to thousands of years. A key obstacle is that material could be diverted for weapons. For military-political reasons, thorium, in the form of a molten salt, has been neglected. India has vast reserves. The dream has for decades been fusion, the power source of the sun. This 'burns' water and promises almost limitless power for very little radioactive waste. It is also far safer than a fission reaction, a catastrophe like Chernobyl being impossible. Over fifty years of international effort, it was always '30 years away' from becoming reality. The two leading designs are the Tokamak, which contains a sun-like plasma in a magnetic 'bottle', and laser inertial confinement fusion (Laser ICF). Recent breakthroughs in the laser systems are promising, but technical challenges remain. A third option is hybrid fission-fusion. As well as enjoying the power output from the fusion component, this confers many of the advantages of the fast breeder process on the fission component. References: http://en.wikipedia.org/wiki/Nuclear_power_plant http://en.wikipedia.org/wiki/Environmental_effects_of_nuclear_power#Carbon_dioxide http://en.wikipedia.org/wiki/Breeder_reactor http://en.wikipedia.org/wiki/Nuclear_fusion http://en.wikipedia.org/wiki/Thorium http://en.wikipedia.org/wiki/Hybrid_nuclear_fusion
As well as technologies for generating electricity, it is important to look at how we could distribute it across the grid more efficiently. The present system uses alternating current (AC), even though direct current (DC) is more efficient. For long-distance transmission, very high voltage levels are needed for efficiency. These must be stepped down to much lower voltages for domestic use. To transform voltage so, the current needs to be AC. When the grid was built, converting from DC to AC was inefficient. Nowadays there better ways to convert DC to AC, so a DC distribution network would save energy. And given a more efficient distribution network, there are more options for siting the power generation. Another option is to distribute energy in the form of gas, mostly hydrogen. References: http://en.wikipedia.org/wiki/Fuel-cells
A cheap and efficient way to store lots of energy would help greatly in both ensuring baseload and meeting peak demands. Conventional electrical batteries do not come close.
http://www.esru.strath.ac.uk/EandE/Web_sites/03-04/marine/tech_storage.htm http://energyeconomyonline.com/Utility_Scale_Storage.html
The special consideration for transport is portability. Glossing over walking and cycling, clearly to be encouraged for their health benefits as well as being carbon-neutral and cheap, we have:
Electric Vehicles Even if the electricity is produced from fossil fuels, electric vehicles have a lower carbon footprint than petrol and diesel vehicles. This is because power stations convert fuel to electricity with an efficiency of up to 40%, whereas a car engine only achieves about 20%. Some is lost in the transmission of the electricity, but it still comes out ahead. A key problem has been the batteries, both their weight and their life expectancies. Lithium ion batteries and their derivatives have been a great advance, but still expensive. June 2010: carbon nanotubes in lithium batteries; MIT: http://www.eurekalert.org/pub_releases/2010-06/miot-ucn061710.php June 2010: EU agrees standard for plugs and sockets for car recharging: http://www.reuters.com/article/idUSTRE65N43120100624
Hybrid Vehicles
Hybrid vehicle can mean any of a variety of technologies: TBA
Plants store energy as oils, sugars and celluloses.
There's not enough oil in plants to make it worth extracting as biofuel specifically, but a great deal of waste vegetable oil (and animal fat) is produced by existing food processing.
Aviation needs a particularly high energy to mass ratio, which means hydrocarbons. Algae may be useful here. This lowers the carbon footprint but does not yet eliminate it.
See also Biomass The hydrogen can be produced from electricity, particularly when there's surplus in the grid. It could also be produced directly from sunlight, as in photosynthesis. To replace a given quantity of petrol you only need a third of the hydrogen by weight, but that is vastly more by volume at atmospheric pressure. So storage is a problem. It can be pressurised, as with LPG, or stored in a tank containing materials which absorb the hydrogen. In the vehicle, the hydrogen can be burnt to drive a combustion engine much like that used with petrol, or it can be converted back to electricity in a fuel cell. The latter is much more efficient but there are major technical challenges still to be overcome.
Recent advances have been made both in generating the hydrogen (hydrolysis) and in using it in a fuel cell to form electricity. http://www.nature.com/news/2010/100428/full/4641262a.html http://www.physorg.com/news156004532.html May 2010: FePt/Pd nanoparticle fuel-cell catalyst; Brown Uni: http://news.brown.edu/pressreleases/2010/05/core-shell June 2010: Riversimple's open-source hydrogen car: http://green.autoblog.com/2009/06/16/riversimple-open-source-fuel-cell-car-could-cost-just-315-month/ June 2010: New process for storing and generating hydrogen; Purdue University: http://www.purdue.edu/newsroom/research/2010/100616VarmaHydrogen.html
August 2010: New platinum/titanium-oxide/tungsten-oxide catalyst more stable and cheaper; Cornell University: http://www.eurekalert.org/pub_releases/2010-08/cu-nco080210.php August 2010: New nickel-borate catalyst 200 times more efficient at hydrolysis; MIT: http://www.eurekalert.org/pub_releases/2010-08/acs-2bi080910.php August 2010: Lung-like fuel cell needs less platinum; Norwegian Academy of Sciences: http://www.newscientist.com/article/mg20727744.900-lungstyle-fuel-cell-needs-less-bling-for-more-oomph.html LPG Already widely used, but emits 80% as much CO2 as petrol and global reserves are limited.
Mass Transit
TBA http://en.wikipedia.org/wiki/Green_transport August 2010: University of York (2010, August 18). How to reduce UK transport carbon emissions by 76 per cent by 2050. Since there is already more CO2 in the atmosphere than is safe (380+ ppm compared with 350), there is a need to draw CO2 back out. This can be done by natural means such as increased forest, natural with intervention (biochar), or by engineering (artificial trees).
Biochar is another name for charcoal; a fuel that will burn at the higher temperatures needed for some processes than would the biomass from which it was made. But calling it biochar puts the accent on an alternative use, namely, to sequester carbon. Some energy is still derived from the charring process, but much less than by burning the biomass completely. The resulting char is used to remediate soils, greatly improving their retention of water and nutrients, while also removing the carbon from circulation for hundreds of years. It has been calculated that carried out on a world scale, largely by peasant farmers, this could draw down enough carbon. Organising it would be a major challenge.
Artificial trees and scrubbing towers These are methods for extracting CO2 from the atmosphere, but still as CO2. It then has to be sequestered in the same way as with CCS. This may be cheaper than retrofitting CCS to existing plant because the scrubbers would be sited close to the repository.
Ocean fertilisation Phytoplankton are the main photosynthesising organisms in the oceans. Their abundance is often limited by lack of iron, so the idea is to fertilise the oceans with iron and generate phytoplankton blooms to absorb CO2. Numerous experiments have been conducted, with varying results; in some cases the sequestration is only temporary. If it works, it is relatively cheap. The main concern is the inherent uncertainty in monkeying with ecology. Experiments continue. References: http://en.wikipedia.org/wiki/Biochar http://physicsworld.com/cws/article/news/40254 http://en.wikipedia.org/wiki/Carbon_dioxide_air_capture http://en.wikipedia.org/wiki/Iron_fertilization The term geo-engineering has been used to cover rather a wide range of proposals.
Low-tech:
Most proposals relate to rooves. In some places, this can pay for itself in reduced air-conditioning costs. However, the same savings might be made more cheaply with insulation, so an incentive is needed to encourage the whitening of rooves.
High-tech:
This may be already happening accidentally (Science, DOI:10.1126/science.1182274). References: http://en.wikipedia.org/wiki/Cool_roof http://2020science.org/2009/05/27/steve-chus-white-revolution/ http://en.wikipedia.org/wiki/Geoengineering http://www.climateandfuel.com/pages/exotic.htm http://www.mindfully.org/Air/2002/Decreased-Pan-Evaporation1nov02.htm Other Agricultural methane TBA Renewable Energy Policy Network for 21st Century Lots of downloadable presentations here: http://www.beyondzeroemissions.org/events/discussion-group |
