Dear fellow Stirling engine enthusiasts,
My name is Phillip Wolter and I am an 18 year old college student from Ohio. I am currently starting to design a Beta Stirling Engine for Engineers Without Borders (EWB). The purpose of this engine will be to power a pump to lift water 50 meters from a bore hole well where it will be distributed to the 5000 people who live in the village. Seeing as I have never built a Stirling Engine before I thought it would be advantageous to seek help from those who have experience in the field. As I progress with models and working my way through the EWB committee meetings I will be posting progress and questions here. Thank you in advance for your patience with my lack of knowledge and for your help.
Thanks much,
Phillip Wolter
Stirling engine to pump water in Africa
Re: Stirling engine to pump water in Africa
Hi Phillip,
I like your plan, and it's definitely a laudable aim, this is just a "back of the envelope" calculation to work out if your plan is feasible. An engine can lift water as far as you want (in theory) but lifting large volumes is a different matter.
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If we assume a usage of 2 litres per person per day, that's 10,000 litres a day. A litre weighs one kilogram, and lifting one kilogram through 50m takes 1 * 9.8 * 50 = 490 joules. To lift 10,000 litres will therefore take 490 * 10,000 = 4,900,000 joules.
If the pump was running 24/7, it would have 24 hours to do this work, so the required power is 4,900,000 divided by 24 * 60 * 60 seconds in a day.
4,900,000 / 86,400 = 56 watts. This is the continuous power required to do the work- if you want a solar powered engine, if we assume 8 hours usable sunlight per day we will need three times the power, or about 165 watts.
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You can get a decent amount of power from a high temperature stirling engine given direct sunlight and a high degree of concentration (see this video, though I think his guess of 100W is pretty optimistic), but a low temperature (ie direct solar) stirling engine producing 150 watts would have to be incredibly big. Alternatively, if the engine was going to be powered by external combustion of plant waste (rice hulls, husks, etc) achieving that much power wouldn't be a problem. There was an attempt in the eighties to produce a 5HP (many times what you need) stirling engine to run on biomass for use in India, but it never came to fruition. There is a book about the project, which you can find out more about here.
I'm not trying to put you off, just providing some figures for feasibility.
I like your plan, and it's definitely a laudable aim, this is just a "back of the envelope" calculation to work out if your plan is feasible. An engine can lift water as far as you want (in theory) but lifting large volumes is a different matter.
------------
If we assume a usage of 2 litres per person per day, that's 10,000 litres a day. A litre weighs one kilogram, and lifting one kilogram through 50m takes 1 * 9.8 * 50 = 490 joules. To lift 10,000 litres will therefore take 490 * 10,000 = 4,900,000 joules.
If the pump was running 24/7, it would have 24 hours to do this work, so the required power is 4,900,000 divided by 24 * 60 * 60 seconds in a day.
4,900,000 / 86,400 = 56 watts. This is the continuous power required to do the work- if you want a solar powered engine, if we assume 8 hours usable sunlight per day we will need three times the power, or about 165 watts.
------------
You can get a decent amount of power from a high temperature stirling engine given direct sunlight and a high degree of concentration (see this video, though I think his guess of 100W is pretty optimistic), but a low temperature (ie direct solar) stirling engine producing 150 watts would have to be incredibly big. Alternatively, if the engine was going to be powered by external combustion of plant waste (rice hulls, husks, etc) achieving that much power wouldn't be a problem. There was an attempt in the eighties to produce a 5HP (many times what you need) stirling engine to run on biomass for use in India, but it never came to fruition. There is a book about the project, which you can find out more about here.
I'm not trying to put you off, just providing some figures for feasibility.
Re: Stirling engine to pump water in Africa
Hey everyone thanks for the suggestions.
In the near future I will have to build a prototype to demonstrate the feasibility to the rest of the group. I was thinking about buying some aluminum pipe, plate, and shaft to build the thing. Due to the state of poverty in this area EWB tried to heavily discourage burning resources and therefore we would have to go with a fresnel lens type solar powered engine. I think its ok to build a slightly larger engine than seen in the videos as long as we can make it more affordable and easier to supply than solar panels. I also have been considering the idea of having the generator charging a few linked car batteries to keep the pump working even on the few cloudy days they do get.
A few quick questions:
1. Will aluminum be a viable material for a stirling engine?
2. How big would a stirling engine capable of moving a decent amount of water have to be?
3. Is there an optimal ratio of proportions for a stirling engine (cylinder length, diameter, piston length, flywheel diameter)?
4. Someone suggested we use a foam displacer. What type of foam are we talking exactly?
Edit: A little more info.
We are trying to provide most of the drinking water via this pump but we have come to the conclusion that one borehole will not be a sufficient source of water. We will also be collecting rain water from roof tops and looking into alternate water sources.
Edit #2: Here we go.
I found that this area of Tanzania (a small village called Nyambogo) gets nearly 10.5 hours of sunlight year round. A quick number crunch brings us to a slightly more manageable 128 W instead of 165W
I forgot that earlier someone was talking about airdropping it into Tanzania. This will not be necessary as we are sending a team of engineers who can assemble it there. I'm not sure exactly how we'd get it there but I wonder if we could break it into our carry on
Thanks Much
Phillip Wolter
In the near future I will have to build a prototype to demonstrate the feasibility to the rest of the group. I was thinking about buying some aluminum pipe, plate, and shaft to build the thing. Due to the state of poverty in this area EWB tried to heavily discourage burning resources and therefore we would have to go with a fresnel lens type solar powered engine. I think its ok to build a slightly larger engine than seen in the videos as long as we can make it more affordable and easier to supply than solar panels. I also have been considering the idea of having the generator charging a few linked car batteries to keep the pump working even on the few cloudy days they do get.
A few quick questions:
1. Will aluminum be a viable material for a stirling engine?
2. How big would a stirling engine capable of moving a decent amount of water have to be?
3. Is there an optimal ratio of proportions for a stirling engine (cylinder length, diameter, piston length, flywheel diameter)?
4. Someone suggested we use a foam displacer. What type of foam are we talking exactly?
Edit: A little more info.
We are trying to provide most of the drinking water via this pump but we have come to the conclusion that one borehole will not be a sufficient source of water. We will also be collecting rain water from roof tops and looking into alternate water sources.
Edit #2: Here we go.
I found that this area of Tanzania (a small village called Nyambogo) gets nearly 10.5 hours of sunlight year round. A quick number crunch brings us to a slightly more manageable 128 W instead of 165W
I forgot that earlier someone was talking about airdropping it into Tanzania. This will not be necessary as we are sending a team of engineers who can assemble it there. I'm not sure exactly how we'd get it there but I wonder if we could break it into our carry on
Thanks Much
Phillip Wolter
Re: Stirling engine to pump water in Africa
Our group have used solar panels in the past and have not been very happy with them.
Believe me, our "group of engineers" are all students and we have good leadership :)
Believe me, our "group of engineers" are all students and we have good leadership :)