The question is no longer "Who has seen the wind?" but "Who owns the wind?"

In the developing world of renewable energy, can neighbouring wind farms steal from each other? What if you put solar panels on your roof and your neighbour plants a tree that blocks them from the sun? Do you have a right to solar access?

These aren't just philosophical questions, but real-life challenges that are already lining lawyers' pockets in Canada and Europe.

"Who owns the wind over land, and at what height does that ownership start?" said John Marrone, director general of the CANMET Energy Technology Centre at Natural Resources Canada.

"Those are the kinds of issues that emerge. We never had to worry about these things, and now we do."

In the Drake Landing Solar Community in the Alberta town of Okotoks, just south of Calgary, Sterling Homes inserted legal encumbrances into its purchase agreements, stipulating that the 52 new homeowners could not plant vegetation that shaded solar panels.

And there are lots of solar panels in the leading-edge community. Each home has two 1.2-by-2.5-metre panels on its roof to supply hot water to the family living down below.

Added to that, the 52 detached garages hold 800 panels that contribute solar power to run a district heating system that all neighbours share.

"It's not just that you're covering your own solar panels, you're covering the whole neighbourhood's solar panels," said Marrone, whose department helped develop the community.

Keith Paget, manager of special projects for Sterling Homes, said the encumbrances, which also allow utilities access to the panels, will bind all future property owners in the community.

"Future purchasers have to agree to the same thing," Paget said.

Sterling didn't have any models to use, and lawyers spent three months and about $190,000 to devise the legal wording for the purchase agreements and register it on the land titles.

Homeowner Denise Francis said she had no problem approving the encumbrances when she and her husband bought their Drake Landing home in June 2006 and doesn't foresee any conflicts with neighbours.

"We all have solar panels so we're all in the same boat," she said, adding that it will be a while until their small trees are tall enough to worry about anyhow.

Although these agreements have solved the solar access issue in Drake Landing, the situation would be different for an individual homeowner.

"If your neighbour planted a tree next door that would shade your house half the day, there's not much you can do about it," Paget said. "You might have a little difficulty."

"We have some concern about this," said Elizabeth McDonald, executive director of the Canadian Solar Industries Association. "We will be facing these issues and I think there's a lot of need for discussion in the communities where this will impact."

The issue even arose in a TV episode of The Simpsons, when Mr. Burns constructed a giant, movable disk to block out the sun, so Springfield residents would have to constantly use electricity, thus boosting profits for his nuclear power plant.

Solar energy is not the only area where problems can arise. A "wind theft" court case has arisen in Germany, where an existing wind farm claims that a planned neighbouring windfarm's giant turbines will create a slipstream, decreasing the speed of airflow, cutting into profits.

"This fact can neither be found in the Bible nor in the German Criminal Code," says the German magazine Der Spiegel. "In a wider sense, we are talking about larceny although the loot is invisible."

"It's absolutely true - of course that could happen," said Marrone. "If you have a lot of machines, you're changing the pattern of the wind."

That situation has not yet arisen in Canada, where we have fewer wind farms and more space to spread them out, but it could eventually happen at the best wind sites, Marrone believes.

Conflicts between wind farm owners have occurred in many countries where the best sites are close together - Germany, Britain, Denmark and New Zealand, said James Glennie, director of business development for the Wind Energy Institute of Canada - a non-profit research and testing facility in Prince Edward Island.

However, Robert Hornung, president of the Canadian Wind Energy Association, said wind theft might not become an issue in Canada if we learn from the problems that arise elsewhere.

Other emerging technologies that could bring new legal wrangles include wave energy, tidal energy, biofuels and micro-hydro on small rivers and streams.

Marrone said the situation is similar to what the oil and gas industries went through when they first emerged.

"I'm sure the first time somebody drilled a hole, some of these issues came up - if somebody drills a hole right next to you and he's taking... your oil," Marrone said.

"Somehow, we've gotten through all that and now there's all this jurisprudence and everyone knows what to expect of each other's rights and privileges."

© CanWest News Service 2007