Originally published at: https://boingboing.net/2018/12/30/pipes-under-portland-produce-p.html
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So, “Put a turbine in it” is the new “Put a bird on it”?
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Portland residents complaining that they can’t get a good shower in 3… 2… 1…
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It’s a nifty idea but a hard sell, especially in the U.S. where they’d rather wait for a section of century-old water main pipe to fail completely before paying the minimum necessary to replace it. I hope the company that produces this pipe system can demonstrate its long-term value proposition to more cities.
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It’s nice when it works, but I think most cities probably can’t do this. This is essentially converting gravitational potential energy in the water into electricity, which is only viable if the water is flowing downhill to its destination. So you can only do this and get anything useful out of it if the city’s water supply is far uphill of the city itself.
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Furthermore, it inevitably must result in less water pressure delivered to the tap, so not only does your system need to be gravity-fed, but gravity-fed and with pressure to spare.
Still a neat addition to the bag of tricks where it does make sense.
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See also:
- Hydroelectric dams.
- Economies of scale.
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The article says these are installed “where water is naturally flowing downward with gravity”. A system as big and complex as this surely has sections that are pumped and sections where gravity takes over. Is this not just a way of recovering some of the energy expended by the pumps? Why would it impact the pressure at the tap? I’m curious what factor I’m not aware of here.
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A bit disappointed at the alliteration not continuing in the headline. For instance, “Portland pipes produce power while providing populace plenty of potables.”
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Perhaps I can explain. All water utilities are major electrical consumers. Most modern households use at least a tonne of water per day, and mostly, it has to be pumped at least dozens of metres uphill, because nearly all natural water is found in low places: the nearby lake or river valley is the lowest point in town.
The only way to get electricity OUT of the local water resources is if the river drops by so much on its passage through town that you can scavenge some of the potential energy from that drop. And it’s rarely convenient to put a hydroelectric dam in town. Normally, you have it upstream or downstream and get your power there.
If water is high up inside town, it’s either a very small town getting water from groundwater wells, some of which are way up hills (super rare), or it was pumped up there from the river or lake level in the first place.
Perfect efficiency would mean reservoirs near everybody at (preferably) 70m above your house, so that we can pump water 70m above you to your reservoir and you’d naturally have 100 psi for a great shower. (1.4 psi per metre, my favourite metric/imperial mixed constant. We’re metric in Canada, but all pressure gauges are from the USA, in PSI.)
In practice, we have reservoirs that serve a band of elevations from 25m below the reservoir, giving the customer about 40 psi that is tolerable (your shower will be a sprinkle) to the aforementioned 100psi that’s the max rating on your hot water tank. (We aren’t perfect and some people get 105 psi and short-lived hot water tanks. They rarely complain. Others get 38 psi and complain bitterly. Sorry.)
Anyway, that’s most of the design, but because some places are very hilly and uneven and development is uneven, sometimes the only way to serve somebody is from the next reservoir higher, which would blow their hot water tank to bits. So we put in “Pressure Reducing Valves” that run all water through a tiny hole, restricting flow and throwing away energy we put in with the pumps. Forever. But still cheaper than an whole extra reservoir for (say) 200 houses.
These guys are using a generator as their “pressure reducing valve” and getting some of the formerly-lost energy back. That’s all. It’s nice. It’s an improvement in efficiency. It might even pay for itself after about 30 years. Or it might only have been done because vague articles like this one give the impression its some sort of gold mine and complete eco-victory. It’s just not. Sorry. It’s mostly just a PR victory. It’s getting back maybe 1% of the power the water utility buys, because 98% is NOT wasted in PRVs to start with, just in places where an extra reservoir is not workable.
TOPIC #2:
If you want to be some big eco-hero, USE LESS WATER. No, don’t go thirsty or even skip your shower. Just xeriscape and quit pretending the whole North American continent is a great place to grow Kentucky bluegrass. Put in plants that grow naturally in your environment without watering.
IRONICALLY-SUGGESTED ALTERNATIVE
Or, leave in your old plants, but get a backpack that holds 50 lb of water and go down to the river and trudge uphill with 50lb on your back. More or less every day, all through the hot part of the summer, for each 10 square metres of irrigation-needing garden. Because if you use the hose, you are paying US to pump 50lb of water uphill for every 10 sq. m. every day for 100+ days a year. It’s generally over a tonne per household per day (on top of the usual tonne for all washing & cooking) for the gardens and lawns. Because Everybody with a standard golf-course-type lawn (mostly Kentucky bluegrass) is that kind of gardener. With a few HUNDRED square metres. Your standard “inch of watering per week” is 5 tonnes per week for 200 sq. m. (2100 sf). Try THAT with a backpack.
–
Roy Brander, P.Eng.
Sr. Infrastructure Engineer (retired)
Water Resources, City of Calgary
(where we have a 1000 foot elevation difference between bottom of river valley and highest hill, and use about 10% of Calgary’s power.)
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Fight Climate Change, Flush Twice!
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Score: 5 (insightful)
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And see also:
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Probably poorly penned.
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Great (and clear) explanation. Thank you.
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A big thank you for your post! I loved it.
I too was wondering about ROI, which is the heart of the matter, IMO, as far as municipal implementation. If we’re talking about people with lots of money to spend perfecting their off-grid residential palace, maybe ROI isn’t such a big deal.
Yeah.
There’s a 2015 article here…
… that mentions this project, and I will follow the progress of this project with interest.
And as far as this part goes:
Yes, a thousand times this.
There’s a lot of fact-based, reality-tested, practical advice from Brad Lancaster for those who want to learn how. I have (and use) Volumes I and II of Rainwater Harvesting for Drylands and though I live in rather arid central Texas, I believe many of the practices can be widely applicable in less arid places. NB: these books are not solely about rainwater harvesting–there’s plenty on how to make the most of the water you do use, and how to use less.
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Portland gets away with it, since they use a gravity-fed source at over 1000’ elevation while most of the city is under 250’ elevation.
This could work for cities adjacent to mountains, like Denver or San Jose, but probably isn’t in the cards for places like Minneapolis or Chicago.
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No system involving production or use of power can be a closed system. There’s no way any water system can produce as much power as it consumes, so it’s always a net loss on power. HOWEVER, there’s absolutely no good reason for not having a system that can significantly reduce power consumption, as this has the potential to do. So it’s not a perfect solution - so freaking what. It’s better and worth the investment. The less we use, the longer our resources last and that means the better off we’ll be. Build these power-recovering systems anywhere there’s hills.
Years back, when I was a teen, someone asked my dad how we kept our lawn so lush and green. Sprinklers? Special fertilizer?
Our (not really) secret: Just don’t cut the grass very short. Also don’t bag or rake your clippings.
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