At what point are home windmills sustainable?

Question

Do home windmills have a 'prove in' curve for sustainability like they do for economics? I presume they are sustainable sooner than the point where they are economical, but couldn't find anything on what their production does to enviroment (eg like the rare materials in cell phones or production of hybrid car batteries). Assume home windmill is in a rural area with sufficient wind to have an economic prove-in around 5-7 years (ie their initial investment will have been paid back in energy savings and credits). Assume 'home' sized windmill, not a windmill to provide commercial power. Assume electricity in the area is provided by burning natural gas.

Do windmills use any rare components or are they particularly egregious in how they are produced? I assume the carbon footprint reduction (of the energy produced by wind instead of electric company burning fossil fuels) offsets any production sustainability issues - but I'm asking for hard data.

Answer 1

In what sense of sustainable? I assume you mean profitable, since you use "economical" as a synonym in the text.

A short, brutal answer is that a small unit in an urban area is unlikely to generate enough electricity to even cover maintenance costs, so it's not ever going to be profitable. The problem is that smaller turbines are more expensive ($/watt), wind in urban areas is more erratic and people tend not to live in exposed areas (a city will be built in a valley rather than on a hilltop). Urban planning rules make it difficult to build a decent tower so generally an urban turbine will have to be low which makes all those problems worse.

The ATA did a desktop study in 2007 (pdf here) The study concluded that:

• the urban environment is too complex to model with any accuracy; therefore
• the use of anemometers would be advised to check the wind resource at any potential site
• urban turbines have performed poorly overseas and payback periods are likely to be long
• bird strike and electromagnetic interference are unlikely to be significant
• turbines are still expensive, with installation and grid connection costs adding around $10,000 to the cost of the turbine

Note this key point:

In order to gather case study information for this report, a number of small wind turbine owners were contacted to take part in an online survey. The survey was designed to learn about several aspects relating to installation of small turbines, including costs, output, planning, noise and siting issues. Nine respondents described their experience with 10 turbines.

Most of the respondents to this survey live in windy rural areas and have purchased turbines that are readily available in Australia. Typically the turbines have been sited on hills or raised areas and away from houses.

So the study did include actual experience from people who have small wind turbines on their properties.

Anecdotally, there's this slightly cynical thread on Whirlpool where a number of people observe that the turbines on an office building rarely rotate. I've done a "sustainability tour" of that building and another where in both buildings the power output of the turbines was under 1% of capacity. For comparison in a wind farm the capacity factor is typically over 30%.

The answer seems to be that you would need to do this for the exact site you're considering:

1. establish how big and how high your turbine can be
2. install a tower that high with anemometers at intervals up the tower
3. log the wind speed, direction and variability over at least a year
4. work out from that what power output you can expect from the turbine(s) you are considering, at the heights you're allowed to put them.
5. negotiate with the power company to establish a connection regime
6. install the wind turbine
7. negotiate with the neighbours if any problems arise (in Australia "wind turbine syndrome" is a real problem for turbine owners, even if the medical issues are contested)

At step 6 you should have some idea of profitability, but you will have spent quite a lot of money to get there. Assuming it looks profitable, you can then install the turbine and test your assumptions.

Once you've got the turbine up and running you can calculate the payback period for your installation based on actual output, real running costs, and how much (if any) payment you get from the power company for what you feed in to the grid.

Answer 2

In most situations, they are a toy.

One thing comes up over and over on various other sites: Height is critical. The minimum height you should consider is 30 meters. 50 meters is better. This is likely to get you noticed by your neighbors. Ideally you want to be 30 meters above the surrounding wind deflecting obstacles such as other houses and trees. Google "Wind Atlas" Both the US government and the Canadian government publish wind maps of your region. At one point the Canadian one had de-ratings for various heights under 50 meters.

For use in urban areas add the height of the local houses & trees to the height above ground values.

Often, for small units, the price of the mast and base is as much as that of the windmill.

I have a windmill. It pumps air into a pond. It can't saturate the generator so it doesn't need a furl mechanism. The air pump is a simple diaphram pump. The return on investment was about 5 years (compared to an electrically operated air pump)

I know of one other wind generator that was worth it. Was in a fly-in fish camp. (Careen Lake, Saskatchuwan -- nice folks) They used a windmill to charge the batteries used to operate the radios during the day, and on a breezy day it would also power the lights for the evening. But every gallon of gas for the generators had to be flown in, or towed in by skidoo in winter. This made the effective cost of gasoline $15/gallon.

At present small scale wind is not economic unless you have both open space (several hundred feet) a good site, and a good reason to not be connected to the grid.