CFD could do even better

21 June 1998

CONTRACTOR REPORTS ON CONCEPTUAL DESIGN FOR ADVANCED TURBINE, says a headline in Hydrowire (the US hydroelectricity industry's biweekly newsletter). The story introduces itself as being about documentation of 'work to develop conceptual engineering designs for the first phase of the advanced hydropower turbine program sponsored by the Department of Energy'. Cosponsored by the industry's own Hydropower Research Foundation, this first-phase work was done to 'develop a turbine that is more efficient and more "environmentally friendly"'.

As you read on from the introductory paragraph you find that computational fluid dynamics has been employed to produce a concept for a new turbine runner. 'Low pressure change rates, minimum absolute pressures, and minimum shear were among key criteria ... The design also reflects other criteria in the minimum number of blades (only two), minimum total length of leading edges, and large flow passages'.

It turns out, however, that the contractor's report in question is a 172-page publication titled Development of a More Fish-Tolerant Turbine Runner and that its 'environmental' concern is in fact concern for the safe conduct of fish. An overall power efficiency of about 90 percent is claimed at the same time as piscine protection. Maybe later phases of the DoE programme will extend friendliness to the environment more generally.

But is the minimum number of runner blades truly two? Wind turbines have been tried, not altogether unsuccessfully, with single-bladed rotors. On my computation of the fluid dynamics, one full-bladed swipe per revolution (instead of two) would nearly double a fish's chances of slipping through unscathed.

Watch out for lighting effects

So much is said about China's neglect of the environment, as shown for example by use of unclean coal technology (remedial planning has begun, however) and by unrepentant persistence with the Three Gorges hydroelectric scheme, that one may fail to notice such more virtuous efforts as the Green Lights Programme. Yes, the 'green' does here mean conservational and has no intentionally funny implications.

According to an article in E-notes, a quarterly publication of the International Institute for Energy Conservation, the Green Lights programmers envision a 24 TWh reduction in annual lighting demand by the year 2000. That would be about the output of five large thermal generating plants.

The writers, Ming Yang and Peter du Pont of the IIEC, point out that, with 1.2 billion people and the world's third biggest economy (the USA comes first and Japan second), China presents a great and growing market for illuminating equipment. Rural electrification continues while regional industrialization surges. Lighting product sales grew 15 percent a year in 1990-95 and illumination absorbed 13 percent of China's electrical output at the end of that period: as later statistics come out they are expected to reveal demand rising at comparable rates.

Unfortunately China's own lighting industry has been turning out inefficient goods. Moreover, the most efficient lamps are exported and the least efficient are sold at home. So the scope for the Green Lights Programme is immense. Contemporary Chinese incandescent lamps give 10 lumens per watt, fluorescents reach something over 40, 'thin tube' and compact fluorescents extend to more than 50 and high-intensity discharge lamps improve on ordinary fluorescents. Typical western products, on the other hand, may do half as well again as the Chinese in the case of incandescents, twice as well in the case of fluorescent tubes, maybe 20 percent better in the case of compact fluorescent lamps and over twice as well in the case of high-intensity discharge lamps.

Particularly striking in the E-notes data is the message that, broadly speaking, the best western products outdo the typical western ones to the same extent as those typical ones outperform current Chinese lamps. Just levelling up western practice to its best could do as much for conservation as China is striving for by reaching western averages.

Western liberal economies will presumably develop as hitherto, while in the meantime the weird Chinese mixture of command and free market principles is stirred. The brighter future is to my mind undoubtedly promised by liberal economics. Could the weird mixture really yield greener lights?

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