It is widely rumored that the Carlyle Group and AES have bid to buy Calpine and its $26B in assets. A key asset Calpine holds is the Geysers geothermal power plant complex in Northern California of which Calpine owns 20 of the 22 plants producing around 700MW, or 5.5 gigawatt hours of electricity, enough to power San Francisco each year.

We’ll see if this comes true, Calpine has been in bankruptcy reorganization for some time and has steadily been divesting assets oved the past 18 months.

In March of 2005, Goldman Sachs acquired Zilkha Renewable Energy for an undisclosed purchase price, though it was widely speculated to be in the $500M range. Zilkha then morphed into Horizon Wind Energy, LLC. and was operated as a Goldman company until yesterday.

Energias de Portugal, S.A. (EDP) announced it’s intention to acquire 100% of Horizon in return for $2.15B. The combined EDP/Horizon portfolio will have over 3,800MW of generation by the end of this year and a pipeline of some 9,000MW.

This marks the latest in a series of European acquisitions in the US renewable power market. Earlier this month, AMP Resources was acquired by the Italian electric utility ENEL. It’s clear the large European companies are taking advantage of a window where US utilities are asleep at the switch…

One of the limitations in using renewable resources for power generation at scale is the fact that nearly all renewable generation sources have some achilles heel in harvesting the natural resource. For instance:

• Solar (PV, thermal, etc) only generates when the Sun is shining. Average capacity factor, 24%.
• Wind only generates when wind velocity is above x threshold of m/sec. Average capacity factor, 30%
• Hydro (gravity, wave, tidal) only generates when there is sufficient resource, drought, calm seas, and shifting currents impact production. Average capacity factor, 70%.
• Waste gas generates at small scale and only when there is sufficient gas as dictated by the decomposition or production process. Average capacity factor, less than 50%.
• Geothermal generates only as long as there is heat and some material to carry the heat’s energy. As heat and resource are mined and released (old plants) the overall production of the resource decreases. Average capacity factor, 90%.

Each of these renewable electric generation means has their charm and some have more favorable characteristics than others, but they all could benefit from some sort of energy storage mechanism at utility scale to compensate for times when the renewable resource is not producing. This has long been a challenge for wind producers as wind production frequently is mismatched to consumption patterns for the power.

Peak consumption time tends to be during the day where renewables like solar produce at their peak. Wind is unpredictable by definition so the need to store the energy for future use becomes a vital part of the equation to make the projects viable and reliable. After all, I think everyone expects the light to power up when the switch is flipped.

There seem to be 3 major approaches to the storage challenge:

• Compressed gases (as reported yesterday in Renewable Energy Access)
• Pumped water – using surplus electricity to pump water uphill back into a reservoir for instance
• Battery storage schemes where electricity is kept until needed

It seems to me a fourth approach (which may be happening, but I haven’t seen anything about it) would be to use the surplus electricity to process other fuels with better storage characteristics. An example would be to use the renewable electricity surplus to process hydrogen gas that can then be used in the future for other purposes (including potentially transportation as well as electric generation.

This is clearly a barrier to economic viability as well as large scale renewable adoption. Until this challenge is met, there will be a natural governor on the velocity of progress on renewable electricity generation.

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.