by kublikhan » Sat 26 Mar 2016, 19:14:30
$this->bbcode_second_pass_quote('BrianR', 'D')oes this absolutely demonstrate that there is net positive energy from windmills? And is this a question we should be asking, or will the demonstrable benefits, beyond the economics, such as environmental, be sufficient to outweigh (possibly) net negative energy?
That was never in question. Wind turbines have long been known to be net energy positive:
$this->bbcode_second_pass_quote('KaiserJeep', 'T')he wind turbine pays off the fabrication energy debt in a year. That would be the energy used to manufacture it, and to source all the raw materials from nature. That includes burning coal and coke to make steel - and consuming oil for fiberglass and insulation for copper wires, and copper, concrete, and excavation, grid attachment, etc. Not to mention, transporting raw materials from widely dispersed sources, and transporting finished goods to the wind farm site.
US researchers have carried out an environmental lifecycle assessment of 2-megawatt wind turbines mooted for a large wind farm in the US Pacific Northwest. Writing in the International Journal of Sustainable Manufacturing, they conclude that in terms of cumulative energy payback, or the time to produce the amount of energy required of production and installation, a wind turbine with a working life of 20 years will offer a net benefit within five to eight months of being brought online.
The pair has carried out a life cycle assessment (LCA) of 2MW wind turbines in order to identify the net environmental impact of the production and use of such devices for electricity production. An LCA takes into account sourcing of key raw materials (steel, copper, fiberglass, plastics, concrete, and other materials), transport, manufacturing, installation of the turbine, ongoing maintenance through its anticipated two decades of useful life and, finally, the impacts of recycling and disposal at end-of-life.
It is likely that even in a worst case scenario, lifetime energy requirements for each turbine will be subsumed by the first year of active use. Thus, for the 19 subsequent years, each turbine will, in effect, power over 500 households without consuming electricity generated using conventional energy sources.