Energy Knowledge
From Common Energy UVic
This page is part of the Knowledge Base and provides a necessary context for understanding the climate crisis.
The sharp increase in anthropogenic carbon dioxide (CO2) emissions since the beginning of the industrial age is due to fossil fuel combustion. The cars we drive, the energy that powers and heats our homes, and the industries that build our plastics and metals all depend on fossil fuels and produce signficant emissions. This section provides a broad overview of the energy systems that have existed, currently exist, and potentially will exist as we move towards an emission-free future.
Also see UVic Energy Research
Also see Common Energy Climate Trust
Contents |
[edit] Framing the Problem
[edit] Energy System Architecture
Energy technology does not spring up on its own; rather, innovation is driven by our demand for services. The link between source and service is what is defined as the energy system and is shown below, courtesy of the Integrated Energy Systems Institute at the University of Victoria (IESVic). A particular service demands an associated technology, which uses a particular energy 'currency'. This currency in turn was created from natural energy sources using the appropriate transformer technology. Transportation, for example, is a service provided by the automobile, which requires gasoline. This gasoline is produced by converting natural oil, say from Venezuela, in an appropriate oil refinery.
Often, multiple configurations of an energy system can be used to provide the same service. Take the image below for example. Communication with Grandmother can be by mail or through some electronic method. Each service however requires a distinct energy currency, in this case diesel/jet fuel or electricity. The transformer technology is specific to the chosen currency, as is the natural energy source to the transformer technology. Only oil can provide delivery by mail, while a host of natural sources are capable of powering electronic communication. Much of energy policy today focuses on choosing the most cost-effective path towards providing a particular service, in this case a much appreciated message to Grandma.
Although numerous pathways may exist from source to service, many become outdated and are ultimately discarded as new technologies replace old ones. The following image shows the evolution of transportation from the 18th century onwards. Originally, sunlight was the only source needed to produce hay, the currency used to provide transportation via horses. As transportation evolved to steam locomotives and then to internal combustion engines, the energy system designed to provide the same service evolved accordingly. The final part of the diagram looks towards the potential future of hydrogen fuel cell powered cars, and the variety of natural sources that may be harnessed.
[edit] The Rise in Energy Use
As our current energy system has evolved, it has required more and more energy to sustain it. To travel 1 km in an automobile requires a myriad of products and processes by which the oil is extracted, transported, refined, delivered, and ultimately used. Consider too the amount of work required to build the automobile. A horse, on the other hand, requires a little bit of hay, sunlight, some time, and a shovel to scoop up its exhaust.
Consider the figure opposite. Energy use per person has increased consistently, corresponding to better technology and a more comfortable, productive, and arguably more meaningful lifestyle. Hunters and gatherers used the high energy content and relative abundance of wood to provide their energy needs. However, as industry evolved and people became accustomed to an ever increasing standard of living, continually more energy was needed from natural resources.
Figure 5 shows the increase in energy use over time, and the new resources that were discovered and tapped to meet demand.
[edit] References
- Rowe, Andrew 2006, Mech 542 Energy Systems Lecture Notes edn, Integrated Energy Systems Institute, University of Victoria.
- D.S Scott, "The Energy System", Int. J. Hydrogen Energy, vol.19, pp. 485-490, 1994
[edit] Some Sobering Thoughts
In Vaclav Smil's brief article, 21st Century Energy, Some Sobering Thoughts he raises a series of major challenges to the transition of our energy regime from fossil fuels to renewable sources.
His primary conclusion is, well, sobering: "Today there is no readily available non-fossil fuel energy source that is large enough to be exploited on the requisite scale."
[edit] Scale
In 1850, 85% of the humans' total primary energy supply (TPES) was derived from biomass. By 1890 50% of TPES came from fossil fuels, and achieving this had required the development of a fossil fuel energy infrastructure capable of delivering 0.7 Terawatts. To achieve the same feat with renewable energy sources today would require the development of 6 Terawatts of renewable energy.
[edit] Energy Density
In the transition from biomass to coal, and then from coal to hydrocarbons, the energy density of the fuel increased substantially. In other words, the same amount of energy could be derived from less weight of fuel. Using biomass based fuels, such as ethanol, requires a larger and more powerful infrastructure to move these low energy density fuels.
[edit] Power Density
Power density is the "rate of energy production per unit of the earth's area and is usually expressed in watts per square meter (W/m2). Fossil fuels have power densities several orders of magnitude larger than all renewable sources. This means that a very small area of land produces an enormous flow of energy. We have structured our society to use these high power densities by concentrating the density of our power demand. This presents a challenge because renewable sources are several orders of magnitude less power dense.
There is a considerable amount of variation between renewable energy sources. Biomass tends to be around 1W/m2 while wind reaches 10W/m2 and solar PV gets to 20W/m2. This compares with 100 to 1,000W/m2 for coal and hydrocarbons. So,
"In a future solar-based society inheriting today’s urban and industrial systems, we would harness various renewable energies with at best the same power densities with which they would be used in our dwellings and factories. Consequently, in order to supply a house with electricity, photovoltaic cells would have to cover the entire roof. A supermarket would require a photovoltaic field roughly ten times larger than its own roof, or 1,000 times larger in the case of a high-rise building. In other words, a transition to renewable energy would greatly increase the fixed land requirements of energy production and would also necessitate more extensive rights-of-way for transmission."
Smil goes on to point out that with a power density of just 0.22W/m2, corn based ethanol would require twice the cultivated land in the US to replace its demand for liquid transportation fuels, currently served almost entirely by fossil fuels.
[edit] Intermittency
Our society demands an ever increasing constant (base load) of energy. Fossil fuels are easily stored and fossil fuel powered generators are available on demand. In contrast, renewable sources such as wind are not easily stored and suffer from the vagaries of the elements. This means that if our entire energy regime were to become renewable overnight (without solving the storage problem) their supply of energy will not always, and perhaps not often, match up with demand.
[edit] Geographical Distribution
Human settlements were not located or designed with renewable energy in mind. There are many large population centers in the world that have little proximate renewable energy, or have only one or two kinds. Dealing with this problem will require enormous energy transportation infrastructures.
[edit] References
Vaclav Smil. "21st Century Energy: Some Sobering Toughts" OECD Observer no. 258/259 (2006): 22-3, http://home.cc.umanitoba.ca/~vsmil/pdf_pubs/oecd_observer.pdf, (accessed May 1st, 2007)
[edit] World Flow Chart on the Sources of C02e Emissions
The World GHG Emissions Flow Chart from the Climate Analysis Indicators Tool shows the sources of the various C02e emissions and their size relative to one another.
In short,
- Approximately 61% of C02e emissions come from energy use for transportation, electricity, heat, and industry with other sources of fuel combustion and fugitive emissions contributing 12.9% of that total.
- Land use change (primarily deforestation), agriculture, waste, and industrial processes make up the remaining 39%. While deforestation, at 18.3% of the total, primarily contributes C02 the rest primarily contribute methane or nitrous oxide.
[edit] Possible Solutions
Links:
- The Energy [R]evolution report by Greenpeace and European Renewable Energy Council
- Solar Hot Water (slide show by Solarcrest, Victoria )
- Interested in biofuels? Check out Grist's in depth look at 'em: Fill'er Up
