Deench

Everything for Everyone

Category Archives: renewableenergy

Unused US hydropower could supply 1.5 million megawatt-hours annually

In the US, the loss of landscape and wildlife to hydropower has made the installation of major new dams very unlikely; in fact, the government is seriously considering removing a number of existing ones, and has recently dismantled some smaller ones. But two reports by the Department of the Interior suggest that this doesn't mean the end of new hydropower in the states. The DOI has gone through its catalog and identified existing dams and canals that could be fitted with generators, and found the potential for up to 1.5 million megawatt-hours annually.

The Obama administration has decided to take what has been termed a portfolio approach to reducing the country's reliance on fossil fuels (the DOI calls it "all-of-the-above"), expanding nuclear and hydropower while fostering the wider use of wind, solar, and geothermal power. Hydropower would seem to be the most difficult to expand, given the problems seen with dams on the West Coast (loss of local fisheries) and the rapidly dropping water levels at the dams based in the western interior.

But a 2011 report identified large numbers of dams that are already in place, but not generating their full potential, or aren't producing electricity at all. Now, the Bureau of Reclamation has gone through its full catalog of canals, drainage sites, and water tunnels. Anything that had a drop of five feet, could generate 50kW or more, and had water for at least four months of the year was considered. These total up to about 350,000 megawatt-hours annually. Add that to the figure from the dams, and you get the 1.5 million megawatt-hours figure. All of that without disrupting the environment any more than it already has been.

Overall, the figure isn't overwhelming—Glen Canyon dam alone produces more than this, and it's actually one of the smaller dams in the region. But that's the advantage of a portfolio approach: every little bit helps.

Read the comments on this post


How California can hit its mid-century emissions reduction goals

If California wants to reach its goals for greenhouse gas emissions—80 percent below 1990 levels by 2050—it must replace most direct fossil fuel use with electricity, according to a new analysis published in Science. In addition, energy efficiency needs to rise steadily and most electricity generation needs to be decarbonized. Since the state is the world’s sixth-largest economy and 12th largest greenhouse gas emitter (its per capita numbers are similar to those of Japan and Europe), strategies developed specifically for California are likely applicable to many large, developed nations.

Read the rest of this article...

Read the comments on this post


Google drops the axe on its internal renewable energy work

Google has shown a significant commitment to efficiency and renewable energy, using its RE < C initiative to invest in a variety of wind power projects and map the US's geothermal resources. But, not content to leave all the fun to other companies, part of RE < C involved work done by the company itself. Now, as part of its general cutbacks, the company has announced that all internal renewable energy work will stop, although outside investments will continue.

Google's efforts were probably well thought out at the time they launched, but they ended up being done in by a combination of a lack of relevant experience and betting on the wrong technology in what's a dynamic and fast moving market. The bet that made sense was that concentrated solar power would end up being a dominant renewable technology, but any reliance on water for power generation could limit its adoption, given that the best sites for solar facilities resided in the desert.

So the company took a two-pronged approach: work on the heliostats that allow mirrors to track the sun, and develop a solar-driven hot air turbine called a Brayton engine. The latter only got as far as computer-based analysis of potential designs, but the former involved Googlers building sun-tracking mirrors and testing them out. This is where the lack of experience came into play, as the report on the experience notes, "We learned that handling glass is tricky, and also experienced a stationary mirror module structural failure." (Perhaps the other initiatives that are facing the axe were suffering the ensuing seven years of bad luck.)

A number of different concentrated solar technologies could benefit from a better heliostat, but it turns out that the renewable energy companies were already doing a reasonable job of extracting savings—"Our cost analysis projected that our heliostat field would be modestly less expensive than previous approaches," Google concluded.

Meanwhile, the entire field seems to have moved beyond the need for a Brayton engine. Photovoltaic systems have dropped in price much faster than expected, making their economics far more competitive with concentrated solar. As such, Google has sensed the focus in concentrated solar shifting toward technologies that can continue generating electricity after the sun has set, such as designs that incorporate heat storage in molten salt.

So although RE < C wasn't misguided, its cancellation isn't going to have a discernible impact on the renewable energy field, since companies that specialize in this field were outperforming it. And, unlike many of the companies that are also suffering in this fast-moving and competitive market, Google at least has a profitable side-business to turn to.

Read the comments on this post