/* ]]> */
Jan 032013
 
This graph, typical of many wind turbines, shows power output (vertical axis) against wind speed for a typical wind turbine.  There is only a very narrow band of wind speeds suitable for measurable power generation.

This graph, typical of many wind turbines, shows power output (vertical axis) against wind speed (m/sec) for a typical wind turbine. There is only a narrow band of wind speeds suitable for measurable power generation.

One of the essential requirements of any retreat has to be some type of renewable energy source.

As we’ve stated elsewhere on the site, the ultimate and paramount issue in any post-WTSHTF scenario is availability of energy.  Almost everything else in your life is or will be energy dependent – certainly shelter, definitely food, and maybe even water too.  Whether the energy comes from yourself (worst case scenario), from hoarded supplies of energy sources such as propane and diesel (which are only good until they run out) or from other sources, sourcing energy is your most important issue.

There are two or three obvious renewable (or ‘free’) energy sources – hydro, solar, and wind.

Wind has some appeal to it, particular in its abstract form, and particularly from reading the glossy brochures, and in terms of cost, the capital cost per kW of generating capacity is very competitive with other renewable energy sources.  But there is a lot more to wind power than meets the eye, and most of the added issues are negative rather than positive.

To help you better understand wind power, we look in this article at some of the less talked about downsides of wind turbines.

Hydro is easily understood, and solar is not much more complicated.  If you’ve got an accessible flow of water dropping from a higher level to a lower level, you’ve a chance at hydro, and the more the sun shines, and the bigger your solar array, the more solar power you can hope for.

Wind Power Only Works in Some Winds, Some of the Time

But wind is a different matter entirely.  With wind power, you need wind speeds that are greater than the minimum which your turbine requires, but less than the maximum.  At greater than maximum speed, the turbine blades will ‘feather’ – they will turn into the wind and the turbine will cease to spin, and no longer generate electricity.  This is different to solar and hydro – there’s no such thing as ‘too much’ sun or ‘too much’ water.

There’s also less of an issue with ‘too little’ water/sun either – sure, no water means no hydro power generated, and so too does nighttime mean no solar power generated.  But the minimum amount of water or sun needed to start the electrons flowing is truly very low, whereas most wind turbines sit lifeless until wind speeds exceed somewhere in the 5 – 15 mph range.

So that’s the first disadvantage of wind.  Wind works best in a location with steady (rather than gusty) winds that flow regularly in the 25 – 40 mph range.  Not many of us have such locations.  Most of us have insufficient ‘suitable’ wind to make a wind turbine a sensible concept under any conditions.

Even if you do have a reasonably good location, you need to have a back up plan for when you have a ‘wind drought’.  We all know that just because a place averages so much rain in a month, that doesn’t mean it is guaranteed to rain an even equal amount every day, and the same is true of wind, too.  What happens if you have no wind, or too strong wind, for an entire week and are unable to generate any wind-sourced power during that time?  At least with solar, even the cloudiest day will still give you some power, but with wind, you could conceivably end up with a ‘wind drought’ that lasts a week or longer.

That’s a very big problem to confront.  Most solar systems are backed up by standby batteries, with the idea being that during the day, the solar cells generate enough power for your needs plus a surplus to be stored in the batteries, then when the sun goes down, you switch to the batteries for the night, until sunrise the next day.  Plus, with a bit of planning, you can shift your electricity consumption so that most of it happens during daytime and less of it happens at night, reducing the amount of power you need to store.  That only requires a 12 – 15 hour or so supply of stored power.

But what if you’re planning to be able to withstand a seven-day period with no wind at all?  You need at least ten to fifteen times more batteries (which – trust us – is a lot of batteries), plus the excess wind generating capacity to quickly recharge them.

Now, for the further bad news.  Even if you do have reasonably suitable winds in your area, there are two other problems with wind power.  Reliability/maintenance, and longevity.

Reliability Issues

Next time you drive past a ‘wind farm’ have a look at how many of the turbines aren’t spinning.  If the ones around them are turning, then the ones that aren’t turning have failed for some reason or another (that’s not to say that all the ones which are spinning are actually working properly either, of course – some electrical failures don’t result in the turbine blades stalling).  Depending on the location, the design of turbine, and the speed with which failed turbines are repaired, you’ll probably observe anything from one in 20 to one in 10 are not turning when they should be.

Think about that – if we say it takes on average 4 days for a failed turbine to be repaired, and if you see one in 15 turbines are not turning, that suggests that on average that every turbine is failing once every 60 days, and with four days down out of 60, that is a 93% uptime rate.

Okay, wind enthusiasts, let’s take an optimistic view if you prefer.  Let’s say only one in twenty turbines is failed, and let’s allow an entire week for the turbine to be repaired – that suggests the failure rate is once every 140 days, which is still nearly three failures per turbine per year.  That is a 95% uptime rate.

And, just to be fair, wind naysayers, let’s say one in ten are failed, and they can be repaired in two days.  That means an average time between failures of twenty days – not quite three weeks.  Ouch!

You should also remember that these turbines aren’t working 24/7.  Their duty cycle might be more like 8 – 12 hours a day – in other words, they are only working a third to a half of the time, and even at that low rate of application, they are still failing repeatedly.

In a ‘grid down’ situation and with the progressive loss of high-tech componentry and high quality machining, do you really want to rely on such maintenance intensive things as wind turbines for one of the most essential parts of your ongoing survival?  What will you do when you run out of spare parts?

Longevity Issues

The other dismaying thing is the total service life that you might get out of a wind turbine.  It has generally been considered that you can expect 20 – 30 years out of a turbine before it needs complete replacement.  But what if that’s not so?  What if you can only get ten years of life from it.  What happens when the turbine totally fails?

Here’s an article which reports that the actual life span of wind turbines in Britain is proving to be significantly less than was optimistically projected.  There’s such a huge lobbying effort behind wind power generation (in both the UK and US) that this type of data is unlikely to be widely reported or commented on, but go read the article and form your own conclusions.

It is probably okay to plan for a 25 year life for your Level 2/3 retreat’s power source.  But only ten years?  That’s not as long as you might think – the human mind tends to find it hard to appreciate the time to a future date, so as a way of appreciating it, think back ten years instead.  That’s probably not such an impossibly distant point in time.  And so neither is ten years into the future, either.

As a comparison, solar cells are also often rated vaguely for a 25 year or longer life, but unlike a wind turbine, that doesn’t mean that at the end of their rated life, they stop generating power entirely.  Assuming they don’t suffer ‘catastrophic failure’ (ie someone dropping a brick on them!) the output they provide slowly diminishes over time – generally about 0.5% every year.  So after 25 years, a solar cell array has lost only about 12.5% of its maximum power generating capacity.  This article points out that some solar cell installations are still providing 80% of their initially rated power after 40 years, and show no signs of failing.

Solar cells can easily outlast their owners.  Not so, wind turbines.

Integrating Wind Power into Your Total Energy Sourcing Strategy

You’re probably getting the feeling that we don’t like wind power.  That’s moderately correct – we love the abstract promise of wind power, but we’re not very happy with the present day reality.

We could be persuaded, however, to add a wind turbine or three to provide another semi-redundant source of power to our retreat, but as a supplemental ‘bonus’ power source rather than as a critical must-be-working source.  This not only give more total power, but also adds another fail-safe level of redundancy.

Maybe a ‘once in a thousand years’ hailstorm destroys a large part of your solar cell inventory.  Maybe your hydro dam breaks.  Maybe any one of many other catastrophic events occur, in which case you’d be very appreciative to have spread your risk and to have deployed some wind power too.

If you do choose to adopt wind power, we’d recommend deploying multiple wind turbines.  That way, when one fails, you don’t suddenly lose all your wind power.  You ‘only’ lose half (if you have two), or a quarter (if you have four) and so on.

Needless to say, you’ll need to have a truly impressive inventory of spare parts, and beyond that, a high-end machine shop to allow you to repair and rebuild damaged components as well as simply replace them.

You’ll also want to also add to your battery storage capacity, or deploy some other form of energy storage so that you can take the spare wind power, when it is available to you, and put it to some good use.

Summary

Wind power is a very specialized type of power that has many constraints and concerns associated with it.  The wind speeds with which the turbine will actually generate power are concentrated in a very narrow band.  The turbines themselves are very maintenance intensive and prone to failure on a regular basis.  And their total service life may be much shorter than originally anticipated and promised.

Wind power may be acceptable as a ‘top up’ source of power, particularly in our present world where the electricity grid has multiple redundant power sources and can manage even if all wind power was to fail simultaneously.  But we do not recommend wind power as a prime source of power in a retreat/off-grid situation.

If you choose to include wind power as an energy source, you’d need to reduce the impact of turbine failures by investing in multiple turbines – at least three, so that having one turbine go offline would only reduce your power by 33% or less, hopefully giving you still sufficient for your essential needs.  You’d also need an extensive inventory of spare parts, and a much greater reserve bank of batteries to tide you over sometimes lengthy periods when your turbine can’t generate due to the wind being either too weak or too strong.

[suffusion-the-author]

David Spero[suffusion-the-author display='description']

  4 Responses to “Wind Power – Maybe Not as Good as Hoped?”

Comments (4)
  1. I would tend to avoid anything that relies exclusively on high-tech components and/or frequent repairs by skilled repair personnel, as a viable replacement for the long-term loss of the power grid.
    On the other hand, plenty of farmers around here have low-tech windmills that function to pump water out of the ground to water their livestock. Sure, it isn’t as steady and reliable as an electric well pump (while the power grid exists, that is); but they are sturdy and long-lasting, use simple mechanical parts, and even if the pumping is only intermittent, would be a heck of lot better than having NO way to pump water out of one’s well; and the wind is definitely free and more or less unlimited.

  2. I agree with Julie. Intermittent wind can operate a pump to raise water into a holding tank, one of its traditional uses.

  3. Lack of wind isn’t a problem on the Northern Plains, in fact, a calm day is appreciated now and then. 🙂 The old fashioned farm windmills have been incredibly durable. Around the region where I grew up most of the mills pumped water, usually into a large tank AKA “cattle tank”. A few “rich” farmers actually had electricity generating windmills.

    You don’t see very many still on farms these days not because they became inoperable but due to lack of use. Farmers became more comfortable and dependent on electric pumps so the “old” ways fell by the wayside. As time went on the structures became viewed as being in the way so most were scrapped.

    My brother now has the family farm and is in the process of setting up for wind and solar generation. Both systems are going to be used, not for lack of wind, but it just makes sense to have multiple sources. Depending on the weather trend sunlight can be scarce for days on end in this area.

    The points brought up in the article cover the issues of wind but don’t overly concern my bro and I. Whether its antique or modern windmills there’s relatively few moving parts but they need to be kept lubed. Compared to maintaining an engine windmills are not high maintenance. About 30 miles east there’s a large number of those huge commercial windmills. Its correct that not all are running at the same time. Some are down for maintenance but often the reason is the power company doesn’t need all the mills to power the grid. I don’t think you can really compare these huge machines to a small “farm size” mill. The commercial machines are HUGE which means weight which means stress on the parts. Plus they have pitch controls (and brakes, I think). The more parts the more protential issues.

    I’ve been a number places around the US where lack of wind is a real issue and frankly it makes better sense to use solar as your primary electric source. But if have wind I wouldn’t shy away from it. The biggest problem my brother has been the power company. They are being uncooperative with his efforts to incorporate his power into the grid, only because they’d lose income if this power independence got too popular!!

    • Hi, Bill

      Thanks for your detailed and sensible insights into wind power.

      Only one comment I’d offer in reply. I don’t think there is ever a time when any power utility company would turn off wind turbines because it doesn’t need the power. At least in theory, the variable cost of wind power is cheaper than oil/gas fueled power stations, and so if the turbines are capable of turning, they should be allowed to do so. Furthermore, with the mandated growing percentages of power that utilities need to generate from renewable sources, power co’s want to be able to get as much wind power as they can.

      One more thought – if a utility has a surplus of renewable power at any happy moment, it can sell it on to one of the other utility co’s through the national grid.

      So I’m unwilling to say that a non-turning turbine might be stopped simply because its power isn’t required. I think they only stop when they can’t turn! But call me cynical….. 🙂

Leave a Reply

/* ]]> */