Sweet home Alabama Street

Small wind in urban settings

Posted by Adam Browning (Guest Contributor) at 12:41 PM on 31 Mar 2008

Read more about: wind power | energy | California | solar voltaic power | energy at home

I never really thought much about small wind's potential as a significant source of a city's electricity supply. Windmills in a urban setting? I just don't see it.

Didn't see it, that is, until I saw it. The other day I biked by 1303 Alabama St., in the Mission District of San Francisco. Softly -- very softly -- whirring overhead is a 1.9 kW Southwest Windpower Skystream windmill. The Choose Renewables resource estimator says that it's a class 3 wind site, but I wouldn't be surprised if it's actually higher. As any San Franciscan knows, the Mission can be very sunny and pleasant during a summer day, but on summer evenings, as the marine layer moves in, the wind just nukes over Twin Peaks and the South Mission/Noë area can be a wind tunnel.

The result, I expect, makes for propitious economics. The house also has a 5 kW SunPower solar system. California's system peak is shifting later and later, which is being reflected in PG&E's tariffs. The old E-7 Residential Time of Use (which is being phased out) had a summer peak of 12 to 6 p.m. The new E-6 has a summer peak of 1 to 7 p.m., and a partial peak of 7 to 9 p.m. In practice, that means that as the solar system's production winds down in the early evening, the windmill steps in and produces electricity that would have cost up to 53 cents/kWh if bought from the utility.

That's just a wonky way of saying that wind and solar are like peanut butter and chocolate: great on their own, but even better together.

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13 Comments | Post a Comment

Less concrete

An added advantage of some small wind turbines is that they don't necessarily require a concrete pedestal. Large wind turbines, by contrast, require something like 0.3 cubic metres of concrete per kilowatt of rated capacity. That's a lot of concrete when you start adding it up.

And what happens to that concrete when a large wind turbine is decommissioned? Usually it stays in the ground.

These are only my personal opinions.

by Ron Steenblik at 1:28 PM on 31 Mar 2008

Why decomm?

Fair point if true, Ron, but why are wind turbines decommissioned? Given that high class wind sites don't move, aren't most turbines repowered when the first-generation turbine wears out?

How many wind-turbine sites are actually fully decommissioned rather than repowered? (I'm genuinely asking, I have no idea -- I've actually not heard of an aging industrial size wind installation not being reused with a next-generation turbine.)

Obviously if the initial install was in a stupid location (Altamonte Pass, etc.) I could see not reusing that site -- and leaving the concrete base in the ground is probably the cleanest thing to do with it, yes? Would take a buttload of energy to get them out of there for sure.

The 5% Project

by JMG at 2:05 PM on 31 Mar 2008

volatility

One thing about urban wind is that it's so volatile - gusty and unpredictable where buildings are tight, so that most urban wind developers are looking at vertical axis wind turbines rather than horizontal axis units like this one is. Vertical axis machines require a smaller base, too, I believe. More here:

http://www.windpower.org/en/tour/design/horver.htm

Erik

The Orion Grassroots Network: 1,200+ grassroots groups working for conservation & more

by Erik Hoffner at 2:22 PM on 31 Mar 2008

In answer to JMG

Perhaps some pedestals are re-used, but certainly the industry advises communities to plan for decommissioning. As the British Wind Energy Association (BWEA) writes in answer to the question, "What happens when a wind farm is taken down/decommissioned?":

The concrete bases could be removed, but it may be better to leave them under the ground, as this causes less disturbance. If so, they would be covered with peat, stone or other indigenous material, and the site returned as closely as practicable to its original state. The turbine itself will often have a scrap value which will cover the costs of such ground restoration.

Covering up a concrete base -- "with a bit of peat, stone or other indigenous material" -- does not make the scar go away. And sometimes the bases protude above ground level, as in this one.

These are only my personal opinions.

by Ron Steenblik at 2:54 PM on 31 Mar 2008

small turbines and economy of scale.

Most small installations can be pretty inefficient due to (dis)economy of scale effects. I suspect few small scale WT ever recover the energy/resource cost to produce them. There is a reason wind farm turbines have been getting ever larger. Solar PV has to a much smaller degree similar effects, i.e. the price of wiring, inverter, and grid interconnect can be similar to the cost of the panels. Utility scale projects are likely to get better usage of scarce materail and financial resources. Perhaps in this case the local wind resource is good enough that it makes sense?

by bigTom at 3:11 PM on 31 Mar 2008

reply to bigTom

do you actually know that, or are you just making it up? I know there was a University of Wisconsin study that put energy payback in the 17X to 39X range. even if that was for a large windfarm, i'm not sure why it would be any different for a small system--the materials-to-production ratio should scale commensurately.

Get Some Sun: www.votesolar.org

by Adam Browning at 5:44 PM on 31 Mar 2008

Once did a project in Ft. Worth...

...artist lofts, that would've been almost entirely powered by a combo of on-site wind and solar power. The site was right near downtown too. It would've been LEED certified and also recycled most of the existing concrete and brick on site (since it was a parking lot at the time), and had green roofs and rainwater collection.

Shame it never got built.

by Tasermons Partner at 10:19 PM on 31 Mar 2008

Nitpick much do we?

I'm wondering why people are opposed to wind power in urban settings? Once you get past the noise and the blade throw problem I can't see the point in objection. San Francisco is covered in a sea of concrete and asphalt from the Bay to Breakers with small exceptions like Twin Peaks and the Presidio and the godawfully ugly Sutro Tower looming above it all.

Compared to that monstrosity a few windmills are barely noticable. As for the concrete bases the hills facing the sea are marked with concrete pillboxes and other structures from the Russian River to Big Sur and I defy anybody who doesn't know where they are already to find them without cheating and using Google:Earth. I grew up there and those things are hard to find.

Functionally they are just another set of rocks on a very rocky coast. The works of man aren't as tough and long lasting as we like to think. Lining the coast with windmills wouldn't be any worse than placing our houses or roads there.

Just my $.02

Put the Carbon Back

by Pangolin at 11:43 PM on 31 Mar 2008

Not nitpicking

I think that wind turbines in urban locations, especially where there is already lots of concrete, makes some sense. And small wind power has lots going for it.

But I do not think that we should ignore the concrete "footprint" of wind power, especially large, on-shore wind power. For 700 MWe of rated capacity (i.e., not even reliable capacity) -- the size of two combined-cycle gas turbine power plants, or a few geothermal power plants -- the amount of concrete in the bases would cover an area equal to 20 football pitches to a depth of more than 6 feet. Just because there is already lots of concrete covering the earth does not mean we should not be concerned about more being poured, especially if not all of them are used again (see my previous comment). It may be difficult to find some of them from Google, but on top of former ridges and out in cow pastures, they -- and their service roads -- are plainly there.

These are only my personal opinions.

by Ron Steenblik at 12:12 AM on 01 Apr 2008

Urban wind and concrete...

...Ron, most urban wind structures are actually installed on the tops of existing roofs, especially micro-wind power.

And on large wind farms out in the countryside, the service roads built are usually gravel, not concrete or asphalt. there is alot of concrete in the base support, but it doesn't extend far from the windmill, usually just a few feet.

Plus, typical windmills will offset the GHGs associated with its construction (includin' the conrete) within 6 months or less.

The new powerlines needed actually probably have a greater impact than anythin' else.

by Tasermons Partner at 8:19 AM on 01 Apr 2008

yes

Yes, TP, and like I said above, the vertical axis units don't need much for a base, just something solid to sit on...like a rooftop.

Erik

The Orion Grassroots Network: 1,200+ grassroots groups working for conservation & more

by Erik Hoffner at 9:23 AM on 01 Apr 2008
[ Parent ]

On urban wind and concrete

Tasermons: I wasn't talking about urban or micro-wind power. Indeed, in my original message (see below or above) I was saying that an advantage of urban wind power, especially micro-scale, is that it needs less concrete, or no extra concrete. Also, it incurs less transmission losses.

I know that service roads are not concrete or asphalt. But ever see the erosion that accompanied the building of dirt roads, especially those up mountainsides? It's not always a pretty sight.

I'm not condemning wind-turbines, just underlining the differences between those in cities and those on top of formerly pristine mountain ridges.

These are only my personal opinions.

by Ron Steenblik at 11:25 AM on 01 Apr 2008
[ Parent ]

Sure Geo's better....

but nobody will fund it. Wind gets funding because it's modular; each little bit comes online while the rest is in manufacturing. It's an easier sell.

Put the Carbon Back

by Pangolin at 2:01 PM on 01 Apr 2008

ADVERTISING POLICY

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