Six renewable energy sources judged to be best prospect for future, says report
Nov18, 2009 - RenewableEnergyFocus.com
The best prospects for large-scale renewable energy production and net-energy performance remain wind and certain forms of solar, according to a study released by two California-based think tanks.
“It is reasonable to conclude ... that a full replacement of energy currently derived from fossil fuels with energy from alternative sources is probably impossible over the short term; it may be unrealistic to expect it even over longer time frames,” explains Searching for a Miracle: Net Energy Limits & the Fate of Industrial Society. The report was published by the International Forum on Globalization with content provided by the Post Carbon Institute.
It is the first major analysis to use the new research tools of full lifecycle assessment and net energy ratios to compare future scenarios for how industrial society can face its long term future.
The report analyses 18 power alternatives, from traditional fossil fuels and nuclear, through renewable energies such as wind, solar, wave, geothermal and biomass, to identify their net energy ratios (amount of energy that must be invested in them versus the amount of energy they will be able to produce, as well as their environmental, social and geopolitical impacts).
Certain energy production systems suffer from low or negative net energy gain, including most biofuels and biomass, as well as hydrogen systems, oil shale and tar sands, some of which also present unacceptable environmental problems, the report explains.
The best prospects for large-scale production and net-energy performance remain wind energy and certain forms of solar, although these renewable energies face important limitations due to intermittency, remoteness of good resources, materials needed for large-scale deployment, and scale potential.
The cost to install one kilowatt of new capacity ranges from US$500 to US$1500 for natural gas, US$1900-5800 for coal, and US$4500-7500 for nuclear, to the renewable energies wtih US$1300-2500 for wind, US$2600-3500 for geothermal, US$3000-5000 for solar thermal and US$3900-9000 for solar photovoltaic (PV).
The current cost to generate existing power is US$0.01/kWh for hydropower, US$0.02-0.04 for coal, US$0.029 for nuclear, US$0.04-0.07 for natural gas. For renewable energies, it is US$0.04-0.09 for biomass power, US$0.045-0.10 for wind, US$0.06-0.15 for solar thermal, US$0.10 for geothermal, US$0.10 for tidal, US$0.12 for wave and US$0.21 to US$.83 for solar PV.
“Can any combination of known energy sources successfully supply society’s energy needs at least up to the year 2100?,” the report asks. “In the end, we are left with the disturbing conclusion that all known energy sources are subject to strict limits of one kind or another.”
Conventional energy sources such as oil, gas, coal and nuclear, “are either at or nearing the limits of their ability to grow in annual supply, and will dwindle as the decades proceed but, in any case, they are unacceptably hazardous to the environment,” it explains.
“Contrary to the hopes of many, there is no clear practical scenario by which we can replace the energy from today’s conventional sources with sufficient energy from alternative sources to sustain industrial society at its present scale of operations. To achieve such a transition would require a vast financial investment beyond society’s practical abilities, a very long time - too long in practical terms - for build-out, and significant sacrifices in terms of energy quality and reliability.”
“To say that our current energy regime is unsustainable means that it cannot continue and must therefore be replaced with something else,” it states. “If the transition from current energy sources to alternatives is wrongly managed, the consequences could be severe.”
“While it is possible to point to innumerable successful alternative energy production installations within modern societies (ranging from small homescale photovoltaic systems to large farms of 3 MW wind turbines), it is not possible to point to more than a very few examples of an entire modern industrial nation obtaining the bulk of its energy from sources other than oil, coal, and natural gas,” the report adds. “Thus, for most of the world, a meaningful energy transition is still more theory than reality.”
“The longer the transition to alternative energy sources is delayed, the more difficult that transition will be unless some practical mix of alternative energy systems can be identified that will have superior economic and environmental characteristics,” it concludes. It excludes biofuels (ethanol and biodiesel) from future energy supply and downplays the potential for nuclear, hydro, passive solar and biomass.
That leaves 6 renewable energy possibilities: wind, solar PV, concentrating solar thermal, geothermal, wave and tidal, all of which have challenges such as intermittency or limited growth potential.
“There is no single silver-bullet energy source capable of replacing conventional fossil fuels directly (at least until the problem of intermittency can be overcome) though several of the sources discussed already serve, or are capable of serving, as secondary energy sources.”
“This means that as fossil fuels deplete, and as society reduces reliance on them in order to avert catastrophic climate impacts, we will have to use every available alternative energy source strategically,” it concludes. “Instead of a silver bullet, we have in our arsenal only BBs, each with a unique profile of strengths and weaknesses that must be taken into account.