Where the Wind Blows – Onshore vs. Offshore Wind Energy

A group Alstom's ECO 100 wind turbines.
Source: Alstom 2010 (NREL)

As long as the wind blows, it is sure to be part of the energy conversation.

The wind industry has proven itself as a key player in providing energy to the public.

If the industry is going to continue growing, new infrastructure will be needed to deliver electricity from turbines to consumers.

The question is, which technology makes more economic sense to develop–onshore or offshore?

Is Onshore on Target?

Traditionally onshore turbines have dominated the wind market, with the first turbine constructed in the late 1800’s.

Pros

  • People are familiar with onshore wind. We can point to many examples around the world of how successful onshore wind can be. Denmark is receiving over 40 percent of their electricity from wind and 75 percent of that comes from onshore turbines.
  • The infrastructure necessary to transmit electricity from onshore turbines is considerably less expensive than that of offshore. Onshore wind is also competitive in the greater renewable market, as it is the cheapest form currently available.
  • Onshore turbine production could act as a boost to local economies. If turbines are installed closer to their manufacturing sites, their value is likely to stay closer.
  • There would be less emissions from transporting wind structures if they are installed closer to the manufacturing site.
GE 1.5 MW wind turbines at the Grand Ridge Wind Energy Center in Lasalle County, Illinois.
Source: Invenergy LLC 2008 (NREL)

Cons

  • Onshore wind speeds are more unpredictable than offshore. Because turbines are optimized at a specific speed, they could lose efficiency if wind is too slow or too fast.
  • Similarly, onshore wind direction changes much more often. Turbines must be facing the direction of the wind to operate efficiently. Advances in technology have led to new turbines that have some ability to pivot towards the wind.
  • There are people – climate deniers, big oil executives, etc. – who are against the growth of onshore wind. Some think it’s an eyesore or noise pollution, others think it endangers birds. There is little evidence supporting these claims, but public buy-in is key to the success of the onshore wind industry.

Misinformation can even make its way into reputable sources from the government, as Dr. John Bane explains, professor and head of the Carolina Ocean Observations Laboratory at UNC-Chapel Hill said.

“I can show you something on one of the federal organization          websites that is just flat wrong, in a couple of ways,” Bane said. “And this leads to  people reading that and thinking, ‘Oh, well this is on a federal website, it must be the truth.’”

He said opinions and inaccuracies can affect how people vote, both in the public and the legislature.

Is Offshore the Reliable Option?

Offshore wind technology is much less developed than its predecessor. It was first implemented almost a century later than onshore. The first offshore wind project went into effect in the early 1990’s near Denmark.

Pros

  • Offshore wind turbines are tend to be more efficient than onshore because wind speed and direction are more consistent. Conceivably, less turbines are needed to provide the same amount of electricity as onshore turbines.
  • Offshore wind is just that – offshore. The “not in my back yard” argument can’t be used if you can’t even see the turbines.
  • Similarly, some see onshore wind farms as threatening farm or other private land. Offshore wind does not interfere with land use.
  • Offshore wind could benefit a marine ecosystem in which it is constructed. Some studies suggest that offshore wind farms protect sea life by restricting access to certain waters and increasing artificial habitats.
December 8, 2009 - Horns Rev 2 Offshore Wind Farm, Installation of Siemens 2.3 MW Offshore Wind Turbines, North Sea, Denmark. (Photo from Siemens AG)
A wind project in the North Sea near Denmark. Source: Siemens AG 2009 (NREL)

Cons

  • The technology necessary to transmit energy from turbines in a body of water is expensive. This could change as the industry matures, but this makes it hard to justify offshore over onshore.

Dr. Harvey Seim, a professor and chairman of the department of marine sciences at UNC-Chapel Hill, said the investment in offshore is worth it–decisions should factor in long time scales.

“In the long term, I think offshore wind is a lot more robust an         investment. I think the wind field is likely to be more reliable and predictable. It certainly has a greater energy density, a significantly higher energy density,” said Dr. Seim. “But there is a big capital investment that has to be factored in to all that. However, if it’s managed properly, it should be recouped by the facility over the long term.”

  • Offshore turbines endure more wear and tear from wind and waves than onshore. This brings up operation and maintenance costs, further distancing the price from onshore.
  • Because offshore turbines are harder to get to, it could take longer to fix problems and restore them to function properly.
  • Renewable energy cooperatives allow small town citizens to be stakeholders in new development. This leads to local economic benefits, especially to rural areas. It is currently not feasible for a small town to finance an offshore farm.

So, who wins?

It’s hard to say what’s on the horizon for wind energy given fast paced nature of the industry. Because the offshore wind industry is relatively immature, the capital cost and operation and maintenance are very expensive for a new project.