Q: Has anyone thought of combining offshore wind farms with ocean renewable energy technology? For example, could we use the offshore base of the wind turbine to produce energy from waves, tides, or currents?

A: Combined offshore wind, wave and tidal projects, also known as “hybrids,” hold great commercial potential down the line when wave and tidal technologies have become more established. At that point, wave and tidal production might compensate for the intermittency of offshore wind, while economies of scale developed from offshore wind could accelerate cost reduction for wave and tidal components.

More on this from Renewable Energy Access.

Langdon Wind, LLC, a joint venture between Florida Power and Light and Ottertail Power Company, have commited to install 150MW worth of wind power in the Cavalier County region of North Dakota. Minnkota Power Cooperative has inked a 25 year deal to buy the output of the farm and Ottertail will use their portion of the farm (~40MW) for their own customers.

The project will consist of some 106 turbines with a nameplate rating of 1.5MW. Using the standard 30% capacity factor rating, we can expect this project to produce something on the order of 400,000 megawatt hours per year, or enough power to serve around 42,000 homes.

Traditional wind systems have had either a horizontal axis with a single blade (95+% of what is in use today) or vertical axis with a single blade (think large egg beater anchored to the ground.) A company called Mass Megawatts Wind Power Inc. is advancing the application of multi-axis vertical turbines, that is many blades mounted vertically in a box-like array around 20 meters off the ground.

The thinking behind this technology is that with more smaller blades, lower wind speeds will be able to output power than in traditional horizontal turbine systems. The design has two generator modes, one 7.5 kilowatt that cuts in at under 4.5 meter/second (~10mph) and another 22.5 kilowatt that cuts in at 6.25 meters/second (~14 mph.) Each unit has 32 generators attached to 32 shafts with blades. That means in a 6 m/s wind, 100% output would be around 864 kilowatts/hour and in a 8 m/s wind, 100% output would be 2,592 kilowatts hour. The image above is a smaller prototype system.

Wind systems rarely operate at 100% capacity, in fact, the average capacity factor is 30% across the installed wind farms. If we take this into account, the MAT system would produce somewhere between 2,267 and 6,811 megawatt hours per year depending upon which generator has the dominant share of time in action. At the prevaling wind rate of $45/MWh, that gives a revenue spread per unit per year of $101,015 on the low end to $306,495 on the high end. The acquisition and construction cost of each unit is estimated (by Mass Megawatts) to be $210,000 per unit. If the MAT unit performs as above and maintenance costs don’t kill it, it might be economically viable.

The science of harvesting kinetic energy from the wind is pretty straight forward, the density of the air moving through the swept area of the turbine at some speed dictates how much energy can be harvested. The formula is: Power = 0.5 x Swept Area x Air Density x Velocity³. Without accurate measurements of the blades on the MAT we can’t make the calculation, but at first blush, the swept area doesn’t look sufficient to produce the stated power levels. This is physics, the equation has to solve so if the area is smaller, then the velocity has to increase and/or air density has to increase.

The other claim made by the MAT folks is that the maintenance costs are lower. I’m high skeptical of this as basic physics dictates the more moving parts an object has, the more opportunities for things to break. In a traditional horizontal turbine there is one blade assembly, one gearbox, one turbine etc you get the picture. On the MAT, there are 32 turbines, 32 shafts, who knows how many blades; it’s at least 32x more likely to experience failure in a given time frame. Now, with the horizontal turbine, a failure tends to be complete. In a MAT, that’s not necessarily so, if 1 shaft/generator/blade combo goes, theorhetically, the other 31 are still in business.

I’m all for experimentation and open minded that breakthroughs can and do happen, but I don’t think we’re seeing one here. A part of me hopes that there is something to this, but the evidence seems to suggest that this design introduces more problems than it solves. We’ll see as Mass Megawatts installs their wind farm, the business plan calls for 100 units to be installed this calendar year. Proof will be in production and we’ll be able to see that as a result of their quarterly reports. We’ll be watching with interest.


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Technorati Tags: Energy | Wind | Multi-axis Turbine

In 2004 the Center for Biological Diversity filed suit against the wind producers operating in the Altamont Pass in California. During the ensuing time period, a study was completed showing that 45 of the 7,000 turbines were responsible for the vast majority of the deaths and a compromised was reached with the producers that during the migration time 50% of the turbines would sit inactive. Last October, a judge tossed the lawsuit saying the Center for Biological Diversity had no legal standing in the case.

This is a classic case of cross purposes. I don’t think anyone wants to see raptors (Golden Eagles, Hawks, etc.) killed unnecessarily, that’s just silly. The producers took many steps to study and attempt to remedy the problem. But the problem was also blown out of proportion as mobile phone towers and buildings kill more raptors each year by far than these turbines, yet we see no action against mobile phone providers. Regardless, the hypothesis is that the lattice towers were good perches for the birds and that’s what contributed to the higher mortality rate than experienced at other wind farms.

The solution seems pretty straight forward to me, shut down and demolish the 45 problematic turbines and allow the producers to “repower” using larger turbines with tubular towers which would serve to reduce the number of turbines, likely increase the output of the farm, and lower the avian mortality rate. What’s lost in a suit like this is that for each MWh of coal generation displaced by technologies like wind, around 1,000kg of carbon and around 13kg of NOX and SO2 is kept from entering the atmosphere. After all, climate change is likely to kill far more species than all the wind farms on the globe combined.

Given the outcome of the court case, I’d expect the producers to be back in business and hopefully taking steps to further reduce the avian mortality rate at the site.


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Technorati Tags: Wind Power | Avian Death | Case Dismissed

This week, Southern California Edison signed an agreement with Alta Windpower Development, LLC. (subsidiary of Australia’s Allco Finance Group) to purchase the output of an aggregation of projects to produce some 1,500MW of electricity from turbines located in Tehacapi. That’s renewable at utility scale and it’s very exciting to see. I strongly suspect that a large portion of that 1,500MW is power that will be displaced when sites in Tehacapi are “repowered” – taking older, smaller turbines down and replacing them with larger, more efficient models. Regardless, it’s encouraging to see renewable projects on this scale.

To put 1,500MW into perspective, the average wind turbine has a capacity factor of 30% meaning the net average generation capacity at any point in time would be around 450MW flowing onto the grid. As a reminder, a MW of capacity is capable of generating a MW per time period, say an hour, to get megawatt hours (MWh.) A MW at 100% capacity and availability would be able to generate 8,760 MWh (non-leap year) or 8,760,000 kilowatt hours. This project will generate approximately 3.9 gigawatt hours per year (3,900,000,000 KWh.) Check your electric bill, it’s metered and billed in KWh, most households in the US consuming around 1,000 KWh per month. The net is, that’s alot of power coming from a renewable resource. Very encouraging.


Technorati Tags: Energy | Investment | Power Purchase