Cost efficient steam catching setup for a water source

[thdm]

TL;DR Summary

local village wants to catch steam coming out of the ground to use it as water source in an area of scarce water - setup should be cheap and very efficient

Hello everyone!

A few months ago I visited a village in Kenya where the local people had recently discovered that they could capture steam coming out of the ground and use it as a water source. However, their setup was really simple, just some PVC pipes trying to capture as much steam as possible and direct it into a water container, with a lot of steam still getting lost.
I was wondering how we could design a setup that is really low cost (like some simple PVC pipes) but able to capture as much steam as possible (highly efficient).
What are your suggestions? Feel free to share your thoughts!

Thanks in advance for your help, let's hope we find a solution we can put into practice! :)

 

[Lnewqban]

Welcome!
How would you route the steam into that apparatus?
How big is the area and what type of soil and terrain?

 

[berkeman]

Welcome to PF; I had no idea that geothermal was so active in Kenya, but a quick search seems to show that it is.

I was wondering how we could design a setup that is really low cost (like some simple PVC pipes) but able to capture as much steam as possible (highly efficient).

The disadvantage of PVC piping is that it is too much of a heat insulator. You need some material/piping that conducts heat well so that the steam can be cooled by modest runs of it. Is there any kind of metal (food grade material) pipe material available there?

 

[russ_watters]

https://en.m.wikipedia.org/wiki/Solar_still

 

[Baluncore]

I was wondering how we could design a setup that is really low cost (like some simple PVC pipes) but able to capture as much steam as possible (highly efficient).

Will the water that condenses be used for drinking?

You will need to analyse the water that condenses, to identify what other volatiles are present with the steam. Depending on the origin of the water and the geology, things like sulphur and arsenic are possible. Look at where the steam issues from the ground. Do you see chemical deposits on the surface, or deeper in the soil, or do you smell sulphur?

Hot groundwater, rising as a liquid towards the surface, is subjected to hydrostatic pressure. The water only boils to become steam when the pressure is reduced, very close to the surface. Any dissolved CO2 will escape the super-heated water first, before the place where the water boils. That CO2 will probably travel the same path, so be mixed in with the steam.

If you capture the steam before it mixes with the atmosphere, the water will be removed as the liquid condensate, leaving concentrated CO2 gas. That could be a hazard to life as it will pool in hollows, basements, and confined cavities.

There are three stages at which hot water or steam could be captured.
1. A deep well will yield super-heated water that can then be boiled under controlled conditions. That may also provide a small amount of hydrothermal power before compromising the supply.
2. A shallow surface cavity, will provide low pressure steam, plus CO2 gas concentrate. A dedicated condenser will be required, with air cooling driven by wind, or by a thermal siphon.
3. A curtain of open weave cloth, downwind of a steam vent, shaded from sunlight during the day, (a bag house), will condense water as the steam cools when mixed with the atmosphere, water will drip into a collection system. The characteristics of the cloth will be critical to efficiency.

 

[Rive]

Capturing steam is all about removing heat.

From the link @russ_watters provided:

The temperature of the ground temperature below ~ 1m is around the daily average temperature. With some tricks it can be lowered further, closing it to the daily lowest temperature.

In short: bury the pipes, and let the condensate flow to the lowest point for collection.

Since the incoming heat will slowly heat up the ground, airing the pipes (or: adding airing pipes, open only for the night) at night will help.

 

[thdm]

Thanks for the answers!
Below some pictures of the current setup they made to give a better idea of the current situation.

Very good point indeed that this water should first be tested prior to using it.
Issue here is that they're a very poor community living at a remote area (basically within an old volcano rim), so it's the only kind of water source they're having nearby (others are a day walking away).
Trying to convince them to first get the water tested and if not suitable for use stop using it at all, might be difficult but of course should be the first step to guarantee there are no health risks.
When I visited they were already using the system for over a year (they just found it out themselves) and were even drinking it...

To give some further background about the local situation: steam is found to escape from the ground at several locations within the old volcano rim (just from some cracks in the ground). According to the locals, it originates from underground rivers. Currently they built a system with PVC pipes as well as some metal pipes to try and capture as much as possible from the steam. However they only manage to catch around 10-20l per day which is not sufficient for the whole community. If the water is safe (which is the first constraint prior working out the system further), it would be a major improvement if they manage to build out an efficient system to provide the whole community with daily use water.

Let me know if you would have any further questions.
I'll see if I can assist them to get some samples of the water tested first.
I'll keep you updated!

 

[thdm]

Hi all!

As a follow-up on above, I reached out to the locals and they confirmed to me that a lab test has been performed already on the water they're capturing.
Please find the analysis report in attachment. As I'm not an expert in this matter, I'm not really sure how to interpret those results.
Could someone please advise if the results show it's safe to use the water as drinking water, or only for other use/no use at all?

If it's good for use we can look further into finding an optimal system for them.

Many thanks!

 

[256bits]

Trying to convince them to first get the water tested and if not suitable for use stop using it at all, might be difficult but of course should be the first step to guarantee there are no health risks.

Assumption that the water source a days walk away is of better quality.

Is KS Spec Limit the allowed ( recommended ) impurity in the water,
If so, most mineral items listed falls below that value.
It doesn't say which microbacterials are in the sample, except some are detectable.

 

[Baluncore]

KS = Kenyan Standard.
EAS = East African Standard.

That looks good, apart from the microbial analysis.

The zinc analysis stands out from the other metals. It suggests the metal pipes were galvanised when installed, and that they may need to be replaced regularly, or less often with plastic pipes.

There are some microbial questions. Total coliforms, E. Coli, and Staphylococcus aureus, all suggest that contamination of the collected water, by animals or people is occurring somehow. That may be a collection container, handling, or a storage problem, and should be addressed. Good hygiene and management should reduce those microbial levels to zero.

If the volume of water produced is increased, then storage should be managed to prevent microbes becoming resident in the warm-water supply. That may require some water treatment and regular analysis.