Renewable Energy; What are the Limits?

rowante

I thought that this would interest all...
Renewable Energy; What are the Limits? by Ted Trainer.

Clouseau2

When I read something like:

"The area over which windmills must be placed to equate to a 1000MW power station is quite large. If 750 kW mills of 80m diameter are placed at 10 x 5 diameters, lose 13% of energy due to array interference and function at 25% capacity, then 4907 mills spaced over 1570 square km would be needed to deliver electricity equivalent to that of a 1000MW power station operating at .8 capacity."

Why would you use 750 kW mills if you could use 1.5, 2.5., 3.6, etc. MW turbines?

Otherwise the article is quite interesting, if a bit pessimistic.

scordry · Tar Sands Joined: May 19, 2005 Posts: 31

Climatologists are only now starting to look at the effects of large wind turbines on climate. They are finding that wind farms affect both thermal and moisture transport, having "contential scale" climatalogical impacts. At some point there will be a trade-off between the no-greenhouse-gas benefits of wind-farms and the climate-altering effects of wind farms.

Sad

backstop

Rowante -

Interesting piece of work.

The author clearly recognizes its limitations, but I wish he'd a/. given it more scope, (there is for instance a chapter on Hydrogen but none on Offshore Wave Energy) and b/. had been more discerning in the assumptions he's working from.

In addition, much of the detail is wide open to question - as below:

"This would represent a [forestry] plantation yield of c 12 t/ha on a small amount of the best land, tapering to zero yield on the last of the c 1500 million ha this line in effect assumes for biomass plantation. This is equivalent to an average yield of 10 t/ha from 600 million ha, i.e., a total yield of 6000 million tonnes, which is 120EJ of primary energy. . FAO (undated) gives a similar estimate for present forest harvest, about 6.6 billion tonnes. The current world primary energy consumption they state, is 410 EJ.

Note that it would not be economic to harvest the low yield areas represented by the right hand tail of the graph, which might cut off one third of the total area under it. However this 6 billion tonnes of biomass converted to methanol would yield a net approximately 6,000 million tonnes x 39 gallons of petrol equivalent per tonne (this assumption is discussed below), i.e., 260 billion gallons, or 6.2 billion barrels, which is 22% of present annual world crude oil consumption.

Note also that much of the present 6000 b t harvest is by Third World people to whom it is "economic" to collect from areas producing at yields well below those that would meet the costs of industrialised biomass production systems. The present yield is already in use, forest and agricultural land is being worked to hard, and as population goes from 6 to 9 billion demand for food producing land will significantly reduce the area available for biomass production."
__________________________________

I've bolded four such questionable areas from the "Liquid Fuels" chapter.

Forestry yields: FOA figures do not account the potential of Coppice Silviculture, whereby the stems are harvested and topped of twig & stick to avoid removing the ecosystem's nutrients, with new stems being grown form the root, which they do up to 20% faster than conventional replanting. It is relatively labour intensive, particularly appropriate for hill and marginal land, and offers multiple side-benefits.

In addition, FAO makes no assessment of the potentially massive areas, paticularly of hill lands, now under marginal grazing, that should for a convergence of reasons be returned to forestry.

"Would not be economic to harvest" is just assertion, based on present western wealth and energy-rich culture. In Nepal for instance, in the absence of good national strategy, people have been going over deforested slopes to dig up the roots as they have no other fuel to cook on.

6.2 Bn BBls of Petrol-equivalent-Methanol offsets subtantially more than 22% of annual crude supply, since a barrel of crude does not yield a barrel of petrol.

Population going from 6 to 9Bn looks to me a fantasy that has no bearing on the energy supply question.

There are scores of other such questions to be asked about the one chapter that I've any expertise on, so I have my doubts about the remainder.

Regards,

Backstop

skyemoor

I decided to take a look at this website, so I started at the top, with Photovoltaics. It starts off;

"The potential for solar electricity supply must be examined primarily in relation to the task of meeting winter demand."

This is always the starting point of those who ignore energy efficiency and conservation. I live in an energy efficient home powered by PV panels. My home's 'demand' is roughly 1/3 that of a similar house, and the PV system provides roughly all of the power in a netmetering configuration.

So wasteful demand is not the correct starting point for assessing the ability of a power source to provide for reasonable demand.

Then with wind, the author assumes wind power can only occur on land as the US purportedly has only 1/7 the wind potential offshore (how this relates to AUS is unclear), and might be as low as only providing 50% of power requirements. While indeed wind is variable, it is easily combined with other power sources, stored as hydrogen or in pumped hydrostorage facilities. However, the author attempts to ignore pumped storage by mentioning it in only a few lines and obfuscating by throwing numbers around without actually using them in a conclusion.

The main flaw of this propaganda piece: the author tries to show how each of these could not 100% replace coal power by themselves alone, when the true power in renewables is the diversity of power sources, especially when combined with pumped storage and hydrogen production.

He also conveniently ignores tidal, wave, and OTEC power sources.

But note the objectives of power generation the author blithely promotes;

"It is of the utmost importance to recognise that whether or not renewable energy can sustain consumer-capitalist society is not a matter of whether it can meet present demand. The supreme goal in this society is rapid, limitless economic growth. It is to increase the volume of goods and services being sold all the time. "

In other words, we are never satisfied with what we have, we must have more and more. Does this sound to anyone like a heroin addict's habit? What eventually happens to the addict?

whereagles

Just a note to clarify those who might be confused as to where wind power comes from. There are three forms of energy that, in a way, feed on Earth's rotation. They are:

1. Hydro plants
2. Wind plants
3. Tidal plants

Basically, the Earth-Sun-planets system is dissipative. The Earth is not 100% elastic, so, as it rotates, tidal forces to the Sun, Moon and other plantets make it lose energy through friction. Large obstacles to the free flow of water and air, like 1 2 and 3, make it lose energy quicker.

The end-stage of the dissipation is the halting of Earth's rotation in relation to the Sun and Moon, resulting in an everlasting day/night. This is precisely what happened to the Moon: because it's a small body, dissipation already stopped its rotation in relation to the Earth, and this is why we always see the same side of the Moon. Wind/tidal/hydro power makes the dissipation Earth-Sun-planets to process quicker.

Ok, so that seems bad. But the good news is that even millions of wind turbines won't do much of a difference as to what would happen naturally. It will take zillions of years for the Earth to stop spinning. Turbines or no turbines.

Optimist · Heavy Crude Joined: Sep 28, 2004 Posts: 220

pstarr

MonteQuest

EnergySpin · Fission Joined: Jun 25, 2005 Posts: 2381

Optimist · Heavy Crude Joined: Sep 28, 2004 Posts: 220

Etalon · Heavy Crude Joined: Sep 04, 2005 Posts: 117

Renewable energy can be sufficient for all our demands so long as the country which uses it has a countrywide (or maybe bigger?) grid to even out varitations in generating capactity due to larger or smaller inputs from solar, wind, wave generation. (and any else you can think of). Having a large system means storage isnt nessesary.

Sure there is a chance that all your sources generate a lot less than anticipated due to freak weather events, but the larger the system is, the less likely this is. If the whole of europe had one grid for example, im sure the chances of this are very small indeed.

MonteQuest

I find it rather telling that, almost without exception, the Big Picture that Trainer paints is lost on those here that have reviewed it.

The way we live is unsustainable.

There is no techno-fix.

We must change the way we view the world and our notions about profit and endless growth.

Any use of renewables without advocating a "powerdown" or "Simpler Way" is a fool's errand.

Good post, Rowante. Smile

_________________
A Saudi saying, "My father rode a camel. I drive a car. My son flies a jet-plane. His son will ride a camel."
Live in Arizona? Check out: http://sustainablearizona.org and read my blog.

EnergySpin · Fission Joined: Jun 25, 2005 Posts: 2381

Optimist · Heavy Crude Joined: Sep 28, 2004 Posts: 220