4 ms·

Remote Mexican village uses solar power to purify water

59 points by Oatseller 11y ago

timonoko 11y ago
Wind blows 24 hours, 3 times more water and more cheaply too: https://youtu.be/9xYXWISWv5I?t=6m28s https://youtu.be/9xYXWISWv5I?t=6m28s
- jws 11y ago
  At this scale, two solar panels, so something like 1200 watt hours of energy per day I don't think you'll find a wind generator and tower to beat the price. 24 hour operation may not be requirement. Clean water stores just fine. I was going to list a counter example of a place where wind would be a better idea, but all the cloudy places I can think of have rain, so they probably get water from that. It's a big world though, I'm sure lots of places have bad enough sun that the number of panels would make the cost tip in favor of wind.
  - timonoko 11y ago
    I was also contemplating windshield wiper motor and solar panel. My tests showed I needed at least 30 watt panel, which was too cumbersome in a kayak. So my collapsible windmill equals 24*30 = 720 Watt hours of solar energy. I had 10 liter can and I needed 3 liters/day, so I started the windmill only twice per week.
  - froo 11y ago
    > At this scale, two solar panels, so something like 1200 watt hours of energy per day I don't think you'll find a wind generator and tower to beat the price. There are many small scale wind generators that produce more than enough energy to run watermakers on yachts, much more cheaply solar panels for the energy output. This has been a solved problem for quite a few years.
- cpeterso 11y ago
  Wind may blow 24 hours. And some places are less windy than others.
- Oatseller 11y ago
  Wind blows 24 hours ... Not everyone in Mexico lives on the Baja coast. ... 3 times more water ... What part of "uses solar power to purify water" lead you to believe it has anything to do with quantity?
- mapt 11y ago
  What wind power does not do well is scale down. There are abundant small-scale wind turbines available, but there are rarely opportunities for them to perform nearly as well per installation effort & cost, as large 1MW+ turbines mounted on massive towers. A town of 100 households who each set up wind turbines in their backyards are paying >10x what a town of 100 households who buy a share in a wind farm coop for the same amount of electricity are paying. Wind has gotten very cheap very quickly over the years since Altamont Pass was put in with 100kW turbines, and a lot of it is down to bigger turbines and towers. http://www.sunnypanels.com/wp-content/uploads/2014/11/wind-energy-costs-per-kwh.jpg http://www.sunnypanels.com/wp-content/uploads/2014/11/wind-e... http://www.power-technology.com/projects/solaronesolar/images/6-wind-power-costs.jpg http://www.power-technology.com/projects/solaronesolar/image... Solar photovoltaic power, on the other hand, scales down fairly well. It doesn't deal with altitude-dependent winds. The economies of scale, while still considerable, are smaller because no matter the scale, all solar photovoltaic facilities involve parts that fit on a shipping pallet.
Figs 11y ago
Does using a solar panel to run a reverse osmosis machine work better than an evaporation-based solar still? If so, why is it more efficient?
- timonoko 11y ago
  Well. In my vast experience 1 square meter of evaporator produces about 1 liter per day. On the other hand 1 square meter of solar panel makes 200 watts and you need 20 watts/liter/hour on the osmosis machine. So the panel is 10*200/20 = 100 times more "efficient", if the use of land area is the issue here (and if the sun shines 10 hours)
- adevine 11y ago
  Yes, it is much more efficient. It takes a lot more energy to transition water from gas to liquid state (energy which is mostly wasted when the water vapor is converted back to liquid) than is needed just to work against osmotic pressure.
  - Scoundreller 11y ago
    > energy which is mostly wasted when the water vapor is converted back to liquid Please tell me the condensing coils are used to pre-heat the incoming water...
    - laughinghan 11y ago
      Unless the condensing coils transferred heat efficiently enough to boil the incoming water, that would barely make a dent in efficiency. > [water's] enthalpy of vaporization, 40.65 kJ/mol, is more than five times the energy required to heat the same quantity of water from 0 °C to 100 °C (cp = 75.3 J/(K mol)) https://en.wikipedia.org/wiki/Enthalpy_of_vaporization#Thermodynamic_background https://en.wikipedia.org/wiki/Enthalpy_of_vaporization#Therm...
      - pflanze 11y ago
        Efficient heat transfer just means using a big exchange surface versus a small material thickness and/or good heat conductivity of the material. But the problem you probably have in mind is that the vapor can't drive the boiling as for the vapor to transfer its energy it has to be condensed, at which point the question becomes why would the vapor condense and boil the water on the other side versus simply boil itself. The answer here should be a pump, so as to make the pressure on the condensation side higher than the pressure on the boiling side. The pump will need energy to maintain the cycle, but it will be (much) less than the energy needed to boil off water in the absence of the pump and condenser. The question becomes open again, I think, why would this be less efficient than reverse osmosis?
tomcam 11y ago
Is this possible because PV panels are more efficient now? Pump motors? In other words, why wasn't this done 40 years ago?
- timonoko 11y ago
  Nothing of value has happened in last 30 years, since the introduction of low-powered osmosis with feedback loop. I recall hand-cranked devices came about 1985 and I also remember I bought 6 watts solar panel for 80 Australian dollars. So this is not an important piece of news at all. Sorry.
- toomuchtodo 11y ago
  http://cleantechnica.com/2014/09/04/solar-panel-cost-trends-10-charts/ http://cleantechnica.com/2014/09/04/solar-panel-cost-trends-...
jacobolus 11y ago
This is really fantastic. I hope they can scale out to more villages in Mexico and around the world. In such remote places, there are regular outbreaks of serious waterborne diseases like cholera and dysentary, hepatitis A is widespread, and amoebas, giardia, schistosoma, various parasitic worms, etc. are endemic. The hard part is setting up the social/institutional structures to maintain the equipment. The technological problems per se are relatively straightforward at this point. Rural peasants typically don’t have the technical knowledge, connections, or capital to set up their own water treatment facilities, and often communities are too remote and sparsely populated to be worth piping fresh water in from a long distance. I particularly appreciated how the MIT engineers trained local residents to operate and maintain the system, and they set up enough payment structure for the plant to pay for its ongoing costs. If that can be sustained indefinitely without too much need for additional external help, then the project should hopefully keep people healthy for decades, on only a small up-front investment.
- IndianAstronaut 11y ago
  This might have a huge impact. A lack of clean water is terrible for health and leads to a lot of deaths. It can also he a cause of cognitve decline. http://www.economist.com/node/16479286 http://www.economist.com/node/16479286
doguozkan 11y ago
I would like some more details on the deployment and maintenance costs of this system. Maintenance costs play a huge role in long-term sustainability and if the initial costs are too high, many people in need of clean water might not get the system in the first place.
- Gys 11y ago
  Read the article: 'She adds that the residents in La Mancalona have taken ownership of the technology, having been trained to operate it on a day-to-day basis, from changing out ultraviolet lights and filters to testing the water quality and replacing batteries. They also have a list of local suppliers for replacement parts.'
emailgregn 11y ago
I'm genuinely interested to know if the altruistic/community driven ethos of these efforts ever last? Once the NGO leaves town and the local federalè or whoever notices a nice little income stream?
- Gys 11y ago
  Read the article: 'At this price, the community reaps a profit of about 49,000 pesos, or $3,600, per year. The community has appointed a committee to manage the incoming funds, setting aside some money for maintenance and repair of the system, and investing the rest back into the community.'
  - HiLo 11y ago
    How would this work in areas where local cartels already have control over these types of assets?

59 points by Oatseller 11y ago

Wind blows 24 hours, 3 times more water and more cheaply too: https://youtu.be/9xYXWISWv5I?t=6m28s https://youtu.be/9xYXWISWv5I?t=6m28s

jws 11y ago
At this scale, two solar panels, so something like 1200 watt hours of energy per day I don't think you'll find a wind generator and tower to beat the price. 24 hour operation may not be requirement. Clean water stores just fine. I was going to list a counter example of a place where wind would be a better idea, but all the cloudy places I can think of have rain, so they probably get water from that. It's a big world though, I'm sure lots of places have bad enough sun that the number of panels would make the cost tip in favor of wind.
- timonoko 11y ago
  I was also contemplating windshield wiper motor and solar panel. My tests showed I needed at least 30 watt panel, which was too cumbersome in a kayak. So my collapsible windmill equals 24*30 = 720 Watt hours of solar energy. I had 10 liter can and I needed 3 liters/day, so I started the windmill only twice per week.
- froo 11y ago
  > At this scale, two solar panels, so something like 1200 watt hours of energy per day I don't think you'll find a wind generator and tower to beat the price. There are many small scale wind generators that produce more than enough energy to run watermakers on yachts, much more cheaply solar panels for the energy output. This has been a solved problem for quite a few years.
cpeterso 11y ago
Wind may blow 24 hours. And some places are less windy than others.
Oatseller 11y ago
Wind blows 24 hours ... Not everyone in Mexico lives on the Baja coast. ... 3 times more water ... What part of "uses solar power to purify water" lead you to believe it has anything to do with quantity?
mapt 11y ago
What wind power does not do well is scale down. There are abundant small-scale wind turbines available, but there are rarely opportunities for them to perform nearly as well per installation effort & cost, as large 1MW+ turbines mounted on massive towers. A town of 100 households who each set up wind turbines in their backyards are paying >10x what a town of 100 households who buy a share in a wind farm coop for the same amount of electricity are paying. Wind has gotten very cheap very quickly over the years since Altamont Pass was put in with 100kW turbines, and a lot of it is down to bigger turbines and towers. http://www.sunnypanels.com/wp-content/uploads/2014/11/wind-energy-costs-per-kwh.jpg http://www.sunnypanels.com/wp-content/uploads/2014/11/wind-e... http://www.power-technology.com/projects/solaronesolar/images/6-wind-power-costs.jpg http://www.power-technology.com/projects/solaronesolar/image... Solar photovoltaic power, on the other hand, scales down fairly well. It doesn't deal with altitude-dependent winds. The economies of scale, while still considerable, are smaller because no matter the scale, all solar photovoltaic facilities involve parts that fit on a shipping pallet.

Figs 11y ago

Does using a solar panel to run a reverse osmosis machine work better than an evaporation-based solar still? If so, why is it more efficient?

timonoko 11y ago
Well. In my vast experience 1 square meter of evaporator produces about 1 liter per day. On the other hand 1 square meter of solar panel makes 200 watts and you need 20 watts/liter/hour on the osmosis machine. So the panel is 10*200/20 = 100 times more "efficient", if the use of land area is the issue here (and if the sun shines 10 hours)
adevine 11y ago
Yes, it is much more efficient. It takes a lot more energy to transition water from gas to liquid state (energy which is mostly wasted when the water vapor is converted back to liquid) than is needed just to work against osmotic pressure.
- Scoundreller 11y ago
  > energy which is mostly wasted when the water vapor is converted back to liquid Please tell me the condensing coils are used to pre-heat the incoming water...
  - laughinghan 11y ago
    Unless the condensing coils transferred heat efficiently enough to boil the incoming water, that would barely make a dent in efficiency. > [water's] enthalpy of vaporization, 40.65 kJ/mol, is more than five times the energy required to heat the same quantity of water from 0 °C to 100 °C (cp = 75.3 J/(K mol)) https://en.wikipedia.org/wiki/Enthalpy_of_vaporization#Thermodynamic_background https://en.wikipedia.org/wiki/Enthalpy_of_vaporization#Therm...
    - pflanze 11y ago
      Efficient heat transfer just means using a big exchange surface versus a small material thickness and/or good heat conductivity of the material. But the problem you probably have in mind is that the vapor can't drive the boiling as for the vapor to transfer its energy it has to be condensed, at which point the question becomes why would the vapor condense and boil the water on the other side versus simply boil itself. The answer here should be a pump, so as to make the pressure on the condensation side higher than the pressure on the boiling side. The pump will need energy to maintain the cycle, but it will be (much) less than the energy needed to boil off water in the absence of the pump and condenser. The question becomes open again, I think, why would this be less efficient than reverse osmosis?

tomcam 11y ago

Is this possible because PV panels are more efficient now? Pump motors? In other words, why wasn't this done 40 years ago?

timonoko 11y ago
Nothing of value has happened in last 30 years, since the introduction of low-powered osmosis with feedback loop. I recall hand-cranked devices came about 1985 and I also remember I bought 6 watts solar panel for 80 Australian dollars. So this is not an important piece of news at all. Sorry.
toomuchtodo 11y ago
http://cleantechnica.com/2014/09/04/solar-panel-cost-trends-10-charts/ http://cleantechnica.com/2014/09/04/solar-panel-cost-trends-...

jacobolus 11y ago

This is really fantastic. I hope they can scale out to more villages in Mexico and around the world. In such remote places, there are regular outbreaks of serious waterborne diseases like cholera and dysentary, hepatitis A is widespread, and amoebas, giardia, schistosoma, various parasitic worms, etc. are endemic. The hard part is setting up the social/institutional structures to maintain the equipment. The technological problems per se are relatively straightforward at this point. Rural peasants typically don’t have the technical knowledge, connections, or capital to set up their own water treatment facilities, and often communities are too remote and sparsely populated to be worth piping fresh water in from a long distance. I particularly appreciated how the MIT engineers trained local residents to operate and maintain the system, and they set up enough payment structure for the plant to pay for its ongoing costs. If that can be sustained indefinitely without too much need for additional external help, then the project should hopefully keep people healthy for decades, on only a small up-front investment.

IndianAstronaut 11y ago
This might have a huge impact. A lack of clean water is terrible for health and leads to a lot of deaths. It can also he a cause of cognitve decline. http://www.economist.com/node/16479286 http://www.economist.com/node/16479286

doguozkan 11y ago

I would like some more details on the deployment and maintenance costs of this system. Maintenance costs play a huge role in long-term sustainability and if the initial costs are too high, many people in need of clean water might not get the system in the first place.

Gys 11y ago
Read the article: 'She adds that the residents in La Mancalona have taken ownership of the technology, having been trained to operate it on a day-to-day basis, from changing out ultraviolet lights and filters to testing the water quality and replacing batteries. They also have a list of local suppliers for replacement parts.'

emailgregn 11y ago

I'm genuinely interested to know if the altruistic/community driven ethos of these efforts ever last? Once the NGO leaves town and the local federalè or whoever notices a nice little income stream?

Gys 11y ago
Read the article: 'At this price, the community reaps a profit of about 49,000 pesos, or $3,600, per year. The community has appointed a committee to manage the incoming funds, setting aside some money for maintenance and repair of the system, and investing the rest back into the community.'
- HiLo 11y ago
  How would this work in areas where local cartels already have control over these types of assets?