Environmental News

The 'fresh' water at the mouth is unlikely to be potable. Take a shower on the coast and some soaps will form 'curds'.

Bob Wilson

 

There are other efficiencies to consider in a RO system. Household systems powered by the domestic water pressure are very efficient on electricity, and produce that dilute waste stream. They are just very inefficient in the use of water. A good system will only dump 4 gallons down the drain for every gallon of pure water produced. A bad one could use up to 20 gallons.

A desalination plant chooses to use electricity to drive pressure pumps that result in more concentrated waste water over high speed pumps to move move more total water through the system to obtain the same drinking water output with a much more diluted waste stream. More than electric and water efficiency go into it a full plant design; membrane efficiency, available space, dispensing of the waste, etc., but a balanced system is going to end up with an actual brine in the waste stream. For example, the Tampa Bay desalination plant has outgoing brine that is over two times saltier than the seawater that entered the system.

The brine needs to be properly handled in order to minimize the ecological impact. That includes diluting it, and this electrical generation system could be placed where that dilution occurs.

It is also unlikely to to be fresh too. Depending on the geography and tides, the salt water can extend miles inland from the river mouth. To have such energy generation efficient, the plant will likely need to have a pipeline up the river to the point at which it is guaranteed fresh.

 

I fear that as air pollution history fades out of living memory, increasing portions of the population will believe that it never happened. Such denial has already been expressed in Congress, even before the most recent election.

 

@183 - The Science Daily review of the Karl paper published in Nature doesn't fully characterize the conclusions of the paper. If you read the full paper, NOx emissions in Europe are significantly underestimated from traffic, and more rigorous enforcement of on-road emission regulations is needed.

However, lower ambient NO2 levels are offset by higher ambient levels of ozone ("weekend effect"), as demonstrated in the paper ("What is the impact on atmospheric chemistry?" section). A 7-8 ppb rise in ozone is expected if NOx emissions are lowered to what is currently encountered on weekends (from increased enforcement) based on their evaluation of current weekday-weekend trends in ambient ozone and NOx.

There also appear to be major inconsistencies in reports/studies of air quality in Europe. The Science Daily review along with many newspaper reports suggest that ambient air quality standards (AAQS), especially NO2, are routinely violated in many metropolitan areas in Europe. However, the most recent report from the European Environmental Agency ("Air quality in Europe — 2016 report," EEA Report No 28/2016) shows that air quality in Europe is actually quite good. According to that report, 16% of the urban population lives in an area that exceeds PM10, 8% that exceeds PM2.5, 8% that exceeds ozone, and 7% exceeds NO2. So according to that report, NO2 is less problematic than any of the other criteria pollutants, contrary to what other reports suggest.

Trends in ambient NO2 seem to be decreasing as depicted by NASA satellite images linked in a post here on PC - http://svs.gsfc.nasa.gov/12094 .

The eddy covariance methodology is certainly interesting, but this study enforces the notion that urban air quality is an extremely complicated nut to crack, so to speak.

 

In the mid-1960s, our family took a vacation drive from Oklahoma to Maine and passed through Pittsburgh. About 50 miles on either side, the trees were distressed and sulphur dioxide was strong in the air. The sun was orange/red when it rose enough to be seen. Dreadful place back then.

Bob Wilson

 

ROTFLMAO!

Bob Wilson

 

I must point out a paragraph with an oft-repeated but misleading theme:

"The process of making solar panels shares traits with making microprocessors. In 1965, Intel’s Gordon Moore predicted that the number of transistors that could be crammed into the same-sized chip would double every 18 months. Essentially, it meant that manufacturers could relentlessly cram more capability into smaller spaces, so now the total amount of computing power that NASA relied on to get Neil Armstrong to the moon can fit in your Apple Watch. A similar dynamic makes solar panels better and cheaper: Technologists can constantly reduce the thickness of solar cells and use less silicon per watt, driving down manufacturing costs while increasing each cell’s efficiency."

The Moore's Law of transistors and computing power simply doesn't apply to solar cells. The former have shrunk their physical area by a factor of ten, then a hundred, then a thousand, then many more times. A similar size shrink of the later simply can't work, because sunlight has a fixed flux density. The large collection area is a requirement, not a dispensable annoyance. Sure, there are improvements in collection efficiency, in wafer thinness, and in cost, but these are in no way comparable to Moore's pattern of shrinking transistors by many orders of magnitude.

 

I suspect we'll continue to see advances that might not be as fast as IC transistor density, a different physics, but significant none the less. A lot of solar spectrum is not being converted to electrons and there are challenges getting the electrons from the junction(s) to the bus. The art of making solar cells and systems is still evolving.

Bob Wilson

 

Yes, solar cells are continuing to improve, and costs are falling. But PV performance hasn't shifted anywhere near the orders of magnitudes we have seen with computer processing power. And there is no theoretical room for it either.

Here is the history of PV efficiency:

(Full size chart: https://www.nrel.gov/pv/assets/images/efficiency-chart.png)

A comparable Moore's Law chart would have a logarithmic vertical scale, not linear.

Commercial silicon single junction units are currently in the 16-21% range, with a theoretical cap of about 32%. Lab units have beat 27%. Other materials could hit a cap of about 34%, gallium arsenide has been pushed to about 29% so far. Multijunction types, currently pushing 46%, still have theoretical room to approximately double.

This doesn't put a floor on prices, which have fallen much faster than efficiencies have improved. But that rate is still not comparable to Moore's Law.