Posts Tagged ‘emissions’
Modelling civilization as “heat engine” could improve climate predictions
Posted by: Karl Ramjohn
An interesting article from Environmental Research Web (November 27, 2008) on a possible conceptual approach to modelling human activities (and the built environment) and how they interact with climate systems (and the natural environment).
—> Modelling civilization as ‘heat engine’ could improve climate predictions – environmentalresearchweb
The extremely complex process of projecting future emissions of carbon dioxide could be simplified dramatically by modelling civilization as a heat engine. That is the conclusion of an atmospheric physicist in the US, who has shown that changes in global population and standard of living correlate to variations in energy efficiency. This discovery halves the number of variables needed to make emissions forecasts and therefore should considerably improve climate predictions, he claims.
Computer models used to predict how the Earth’s climate will change over the next century take as their input projections of future manmade emissions of carbon dioxide. These projections rely on the evolution of four variables: population; standard of living; energy productivity (or efficiency); and the “carbonization” of energy sources. When multiplied together, these tell us how much carbon dioxide will be produced at a given point in the future for a certain global population. However, the ranges of values for each of the four variables combined leads to an extremely broad spectrum of carbon dioxide-emission scenarios, which is a major source of uncertainty in climate models.
Timothy Garrett of the University of Utah in the US believes that much of this uncertainty can be eliminated by considering humanity as if it were a heat engine (arXiv:0811.1855). Garrett’s model heat engine consists of an entity and its environment, with the two separated by a step in potential energy that enables energy to be transferred between the two. Some fraction of this transferred energy is converted into work, with the rest released beyond the environment in the form of waste heat, as required by the second law of thermodynamics.
However, the work is not done on some external task, such as moving a piston, but instead goes back to boosting the potential across the boundary separating the entity from the environment. In this way, says Garrett, the boundary “bootstraps” itself so that it can get progressively bigger and bigger, resulting in higher and higher levels of energy consumption by the entity.
Algae – The Solution to Energy Crisis & Climate Change?
From: World Business Council for Sustainable Development (WBCSD): AFP – July 10, 2008
As the world mulls over the conundrum of how to satisfy a seemingly endless appetite for energy and still slash greenhouse gas emissions, researchers have stumbled upon an unexpected hero: algae. So-called microalgae hold enormous potential when it comes to reining in both climate change, since they naturally absorb large amounts of carbon dioxide, as well as energy production, since they can easily be converted to a range of different fuel types.
“This is certainly one of the most promising and revolutionary leads in the fight against climate change and the quest to satisfy energy needs,” Frederic Hauge, who heads up the Norwegian environmental group Bellona, told AFP. The idea is to divert exhaust spewed from carbon burning plants and other factories into so-called “photobioreactors”, or large transparent tubes filled with algae. When the gas is mixed with water and injected into the tubes, the algae soak up much of the carbon dioxide, or CO2, in accordance with the principle of photosynthesis. The pioneering technique, called solar biofuels, is one of a panoply of novel methods aiming to crack the problem of providing energy but without the carbon pollution of costly fossil fuels — with oil pushing 140 dollars a barrel and supplies dwindling — or the waste and danger of nuclear power.
Studies are underway worldwide, from academia in Australia, Germany and the US, to the US Department of Energy, oil giant Royal Dutch Shell and US aircraft maker Boeing. This week alone, Japanese auto parts maker Denso Corp., a key supplier to the Toyota group, said it too would start investigating, to see if algae could absorb CO2 from its factories. The prestigious Massachusetts Institute of Technology (MIT), for one, has successfully tested the system, finding that once filtered through the algae broth, fumes from a cogeneration plant came out 50-85 percent lighter on CO2 and contained 85 percent less of another potent greenhouse gas, nitrogen oxide. Once the microalgae are removed from the tubes they can easily be buried or injected into the seabed, and thus hold captive the climate changing gases they ingest indefinitely. And when algae grown out in the open are used in biomass plants, the method can actually produce “carbon negative” energy, meaning the energy production actually drains CO2 from the atmosphere. This is possible since the microalgae first absorbs CO2 as it grows and, although the gas is released again when the biomass burns, the capturing system keeps it from re-entering the air. “Whether you are watching TV, vacuuming the house, or driving your electric car to visit friends and family, you would be removing CO2 from the atmosphere,” Hauge said.
Instead of being stored away, the algae can also be crushed and used as feedstock for biodiesel fuel — something that could help the airline industry among others to improve its environmental credentials. In fact, even the algae residue remaining after the plants are pressed into biodiesel could be put to good use as mineral-rich fertiliser, Hauge said “You kill three birds with one stone. The algae serves at once to filter out CO2 at industrial sites, to produce energy and for agriculture,” he pointed out. Compared with the increasingly controversial first-generation biofuels made from food crops like sunflowers, rapeseed, wheat and corn, microalgae have the huge advantage of not encroaching on agricultural land or affecting farm prices, and can be grown whenever there’s sunlight. They also can yield far more oil than other oleaginous plants grown on land. “To cover US fuel needs with biodiesel extracted from the most efficient terrestrial plant, palm oil, it would be necessary to use 48 percent of the country’s farmland,” according to a recent study by the Oslo-based Centre for International Climate and Environmental Research. “The United States could potentially replace all of its petrol-based automobile fuel by farming microalgae on a surface corresponding to five percent of the country’s farmland,” the study added.
As attractive as it may seem however, the algae solution remains squarely in the conception phase, with researchers scrambling to figure out how to scale up the system to an industrial level. Shell, for one, acknowledged on its website some “significant hurdles must be overcome before algae-based biofuel can be produced cost-effectively,” especially the large amounts of water needed for the process. In addition, further work is needed to identify which species of algae is the most effective.
Further discussions related to the topic of this post:
http://www.oilgae.com/forum/viewforum.php?f=1
http://www.worldofrenewables.com/showthread.php?t=16547
http://www.its2hot.in/viewtopic.php?f=28&t=158
http://www.sustainabilityforum.com/forum/climate-change/2762-algae-solution-climate-change.html
“Spatial Footprint” Challenges of Solar Energy Use
Submitted by: Karl Ramjohn
Solar energy can be utilized in either passive or active systems. Passive systems do not contain any internal energy sources, and can be used for direct heating (e.g. solar dryers, water heaters, etc.) or day-time lighting (e.g. “green” office buildings). Photovoltaic devices are an example of active systems based on semiconductor technology, often using silicon (an indirect semiconductor).
The advantages of using solar radiation are well established and often cited – such as their ability (with proper design) to lower energy costs, reduce emissions and other environmental pollution, thereby initiating the process of competitively replacing hydrocarbon use, and thus contributing to sustainable development.
Solar energy approaches are also frequently suggested as a sustainable solution in less-developed countries in the tropical environment, on the assumption of having less seasonal variation in day-length and more hours of direct sunlight each day (i.e., usually a higher intensity and longer duration of incident solar radiation each day). The fuel medium (solar radiation) is also an “open-access” resource (no direct user cost). The overall decline in the operational costs seen over the past 35+ years is also typically acknowledged.
However, one major challenge remains with regard to conversion to solar energy use – their spatial footprint (land use requirement) in the event that larger scale utilization is proven feasible. In particular, for the use of flat-plate collectors or PV systems in tropical environments, this becomes an issue.
The primary reason is that to optimize the use of solar radiation, the panels (or plates) need to be sloped so as to correspond to the latitude of the specific area of the Earth, hence taking up more horizontal space in the tropics. If we take the example of an island in the middle-tropics such Trinidad & Tobago, implementation will require the slope of the panels to be 10 degrees (corresponding to latitude) for the same technology that may be placed at an angle of 40 degrees in countries within temperate regions. The implication is that the area set aside for power generation (or other solar energy use) will no longer be available for other land uses (such as agriculture) and this may be a significant limiting factor, especially in the case of small-island developing states. After all, any large-scale conversion will require much more than a rooftop, and island geography often restricts the feasibility of wind energy.
Some recent discussions aimed at solving or mitigating these potential challenges to sustainable energy:
http://cr4.globalspec.com/thread/20329
GEO ENERGY NETWORK 