Niall McMahon

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Can Medium Wind Compete With Solar PV?

2015-06-24

A question that I was asked recently was this: when is a wind turbine a better investment than solar photovoltaic panels?

So, with a few assumptions, including:

I wound up with the following graph:

solar_wind

Above the horizontal line, solar wins; below, wind wins.

The usual cautions apply, and there are caveats, below, but the graph captures the relationship between the important physical quantities. As the price per kilowatt increases, a higher average wind speed is required at the site to maintain parity with solar, in terms of simple pay-back.

So back to the original question.

Mid-wind machines are usually on taller towers, accessing higher wind speeds, and are cheaper per kW installed. This approximate approach demonstrates that the answer is yes: at typical mid-wind sizes and costs, at average sites, wind energy is competitive with solar energy.

The surprise is perhaps that solar is becoming so good.

The caveats! The graph is produced using average numbers and with plenty of approximation. In Ireland, the winter nights are long and wind becomes a clear short-term winner.

If we are primarily interested in providing secure yet renewable energy at a site, wind must be a component. At some sites, wind will be the only option or the wind resource will be very good.

The graph, however, illustrates the technical challenges for wind: to reduce manufacturing and installation costs while maintaining safety, and maximise power output (usually by improving efficiency, increasing swept area and/or accessing higher winds).

One of the external economic challenges for wind energy is the falling price of solar - this corresponds to a downwards shift of the horizontal line in the graph. It's still moving ...

The second economic challenge is the rise of affordable and reliable battery storage.

About which more soon.

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