Comments on: Windmills vs. Photovoltaics

By: Ben

Ben — Mon, 03 Mar 2008 18:26:12 +0000

Well, if you think about the energy input into getting oil and coal, ask why people haven’t thought of this before.
If anyone could tell me why coal is a good idea, show me. First they destroy the land, and then burn it and destroy the atmosphere.
And don’t say because coal is readily available. because I can’t remember the last time I went looking for a sun burn!!!
And how many times I voluntarily chased my hat after the wind blew it off!!!! I live in Ohio, and Ohio isn’t the windiest nor the sunniest place in the U.S.

By: Jon Bohmer

Jon Bohmer — Sun, 02 Mar 2008 01:09:17 +0000

Don’t forget solar thermal. The world also needs heat energy, and the output from solar water heaters are currently 30 times higher than PV. Plus, this industry grows at 40% per year.

The PV numbers do not include solar thermal plants either.

As to the growth of PV, an example is a new plant being constructed by Norwegian PV company REC in Singapore. Its output will be about 1.5 GW per year. If these PV cells are used in 10x solar concentrators the output is suddenly 15GW per year. The use of lenses and mirrors will lower the cost and increase the output of solar to become meaningful. In 10 years time, it is likely that we won’t see traditional un-concentrated flat plate PV anymore.

By: Andreas

Andreas — Tue, 15 Jan 2008 20:20:46 +0000

I like this discussion a lot but as a fellow Dane, I agree with Simon. The question is not one or the other, but both. We need to harness erenewable nergy from the globe in everyway we can - and each alternative has it’s own niche. Since there is not so much sun, but a lot of wind in Denmark, Denmark has become the leading country for wind turbines. In the alps, billions of watts are being pulled from damns and river turbines and in sunnier countries, PV’s could be preferred.

By the way. Simons site is also in english:
http://www.globalwindpower.com/content/view/116/84/lang,en/

By: Fred Irani

Fred Irani — Thu, 20 Sep 2007 21:37:30 +0000

How about the energy required to create the high tensile steels required for manufacture of the generators used by “wind mills” (or whatever)? Do we get as much energy out of a windmill as we put into its manufacture, installation and maintenence, -social costs aside?

By: Gary Moss

Gary Moss — Tue, 03 Jul 2007 00:21:31 +0000

We should be focusing on this more, not arcane babbling about reducing carbon dioxide output simply for the sake of reducing carbon dioxide output as so many blogs do, where people with a limited grasp of reality arcane points as a matter of status quo in a computer society of all things! Good story btw.

By: Simon

Simon — Wed, 14 Mar 2007 17:54:08 +0000

Just so you know…

Wind Power is very much a reality…

It covers app. 20 % of the Danish power consumption anually. Weather or not wind power or PV is the appropriate choice on a certain location depends on the sun intensity and hours and wind velocities.

So the the choice isn´t one or the other, but one in one location and the other in another location.

This website is in Danish: http://www.globalwindpower.com/content/view/116/84/lang,dk/

It says that we cover 20 % of our consumption with wind power and in 2015 we should reach 35 %.

This is simply a result of 10-15 years of policy to promote and further developing wind power production.

Simon

By: Jeremy

Jeremy — Wed, 31 Jan 2007 20:35:29 +0000

One of the challenges in SOLAR VERSUS WIND is the comparison based on nameplates is just wrong. Glad you spotted that counting nameplate power numbers need to take into consideration whether it’s sunny or windy. But additionally, nameplate values don’t translate to power produced by simply dividing by 1/3rd.

It’s the net power production UNDER THE CURVE over time that matters. Some cells will be much more efficient across the spectrum, angle of incidence etc. than others. Some turbines have better startup scenarios, better capture in light winds, etc. And I can state from authority that two nameplate wind turbines of 3kwh might produce 3200 or 6400 kwhrs per year (a 100% variance).

So, someday, we’ll move from the useless “nameplate” value of noon-day clear skies Arizona solar and 35 MPH wind at 30 meter hub height, and get to YEARLY POWER PRODUCED, which is what we are buying these things for.

It all reminds me of “page views” in the Internet web days. The irony being, Google - the most successful Internet game of them all, monetized the virtual opposite construct - click-throughs.

One other comment: $/watt won’t be the only math, in urban environs - where an increasing majority of the world lives, watts/sq meter will also matter. Case in point, Google is building one of the largest deployments, campus wide, and it will generate a measly 1.6 mw (nameplate) - in a good windy campus, a wind system might be able to do 10-100x that power production on the campus size of google. (or more concretely, there are approximately 36 watts / sq meter on a rooftop in solar power, and 320 watts / sq meter on a rooftop in wind power (even higher for wind if you are not height constrained).

Of course, I work for an urban scale wind power startup, so I don’t come unbiased into this game.

By: Ed Ring

Ed Ring — Fri, 22 Dec 2006 20:25:25 +0000

That is a good question, and one we haven’t addressed in a while. Here’s a study “What is the Energy Payback for PV?” that attempts to answer this.

In this study, which is consistent with others we’ve looked at, a PV system will return about 20x the energy that went into it during its lifetime output. This multiple, which is far better than anything reported to-date for biofuel, continues to improve as thin film technology becomes commercialized.

Moreover, since the primary energy required to make PVs is electricity, and PVs produce electricity, it is possible from an energy standpoint to have photovoltaics themselves generate the power required for the expansion of their own manufacturing output.

By: Rosa

Rosa — Fri, 22 Dec 2006 20:08:16 +0000

Money cost aside, do we know how much energy it takes to manufacture a certain area of PV cells (by any of the current methods), and how much energy they produce in their lifetime (which is limited, mind you)? Using a GWh of mostly coal power to produce PV cells that yield a GWh worth of energy trickled over the course of 30 years doesn’t sound particularly green to me.

By: Ed Ring

Ed Ring — Fri, 22 Dec 2006 17:42:42 +0000

We could call them aerogenerators, I suppose. What is your preferred term?

The $1.00 per watt threshold for photovoltaics was referring to manufacturing cost. Installation costs are another story. A lot of energy and innovation has gone into reducing manufacturing costs for photovoltaics but installation costs remain at $5.00+ per watt for most photovoltaics. Getting installation costs down is being addressed, especially as volumes increase, and as you say, that is a separate and equally relevant issue.