Las Delicious El Salvador is a community of approximately 450-500 homes and ____ residents
The community is located approximately 20 miles from San Salvador on the side of a hill/mountain. There is a 400 ft deep well at the bottom of the hill with a 15hp submersible pump. The submersible pump feeds a small storage tank which feeds a 60hp booster pump which supplies water for the village. The lower storage tank and booster pump are located at an elevation of 1750ft above sea level (according to Google Maps). The well itself is nearly 400 ft deep, but we will estimate the static pumping water depth to be150 ft (this assumption should be verified). The well water is pumped to two upper storage tanks (Tank #1 at an elevation of 2290 ft and Tank #3 at an elevation of 2150 ft) where it is stored in for treatment and distribution. We don’t have perfect flow rate data for the two upper tanks (Tank #1 is 140ft higher then Tank #2 but the pipe going to Tank #1 is larger) for the purpose of this study I will assume each tank gets half the water. I will use the median elevation of the two tanks and assume that that is the HighLift water elevation ((2150ft+2290ft)/2= 2220ft).
All the elevations for this study were obtained using Google Maps. The elevations from Google were checked against some measurements that were obtained during our assessment trip. The numbers agree very well. At the well/booster pump the numbers were within 10 ft (1750ft by Google and 1740 ft by GPS), At the top Tank #1 the numbers were again within 10 ft (being that we weren’t comparing exact coordinates this is fairly good). We also compared the elevation of ?Pedrona? Crossing (we chose slightly different coordinates) but the numbers agreed well. There was some disagreement at Tank #3. The GPS was off by something like 100-150ft but I remember hearing (a while ago) that there was a problem collecting some height data at one of the points. Because Google Maps was almost perfectly accurate at the majority of the points I am going to assume it is the most accurate data we have presently. This study will be done from the elevations that I got off of Google Maps.
Most of the homes in the community (those who are able) pay approximately 5 dollars a month for their water utility. That gives the water utility approximately $1,800 per month operating budget. Operating and Maintenance costs make up approximately a third of the monthly budget leaving approximately $1200 for pumping (electrical) costs.
The community is unable to raise more money and the present pumping budget does not provide families with enough water. We need to make the system more efficient so that the community can get a sufficient amount of water with their present monthly ($5) utility rate.
There are a few possible options to get more efficiency out of the system.
Options:
1. Build a new well higher up the mountain side (or above the village) to minimize the amount of elevation the water needs to be pumped.
· If the well is located above the community the only pumping cost would be from the submersible well pump
· Is water available at this Height?
· What are the costs?
2. Add a second distribution tank half way up the mountain which would feed the houses below it. Then we’d only need to pump half the water to the top distribution system.
· Half of the water would only need to be pumped half way up
· Where are the majority of the houses located? Above or below the half elevation point?
· What kind of savings could we get?
3. Add VFD’s (or a smaller pump in series to the 60hp) to decrease the frictional losses that are a result of the fairly high pumping rate of this system.
· How much could we save?
· What are the costs?
4. Replace the 15hp booster and 60hp booster with one big submersible pump that would pump at a lower rate.
· How much could we save?
· What are the costs?
5. Consider alternative electrical sources (solar, etc)
· Purchase of land may be required
· Purchase and install system
· Revise Electrical System
· How Much does it cost?
· What % of our daily electrical usage could the system make? Half? 10%?
6. Consider adding rain water collection or other system
· Would all the houses get? One centralized ststem?
· Cost?
· How many extra gallons would they provide (total daily average for whole community)
Option #2 Second Distribution Tank
Before we can look at this solution we need to determine where the bulk of the community lives. The well is located below the community at about 1750ft above the sea. The community begins (lowest elevation) at the clinic which is at approximately 1830 ft.
The highest distribution tank, Tank #1, is located at 2290 ft and the other distribution tank, Tank #3, is located at 2150 ft. Both tanks fill at the same time, at similar flow rate. For this study I will assume that half the water goes into each tank, or simply said the average HighLift = 2220ft (if we determine that one of these tanks does receive more water then the other we will have to adjust this value)
The well pump lifts the water approximately 150 ft then the booster pump lifts the water a total of (2220-1750) 470 feet. The median elevation for the community is half way between the Well/Booster Pump, 1750 ft, and the HighLift height of 2220 ft or 1985 ft.
We need to determine where most of our families are living. If they all live near the top of the hill then a tank half way up won’t provide water to many houses. If they are clustered toward the bottom of the mountain a mid-mounted water tank (located half way between the well and top dist. tanks or at 1985 ft) would be able to supply more then half the village and we could save even more.
Ideal Case:
Let’s just look at the ideal case to see what kind of theoretical savings we could get. We will assume half of the homes are above 1985 ft and half of the homes are below 1985 ft. The new tank will be mounted at 1985 ft and will now feed the bottom half of the houses. I am ignoring the frictional contribution (which I think would make this solution very slightly more efficient).
New Pumping Energy Required = Lift out of well + Lift half of the water half way up the hill(235ft) + Lift half of the water all the way up the hill(470ft)
HeightEnergy = mass*gravity*height
New Pumping Energy Required = WellLift(150ft*g*Mass pumped per day) + ShortLift(235ft*g*1/2Mass pumped per day)+HighLift(470ft*g*1/2Mass pumped per day)
This is just for comparison so I don’t really care about how much water they pump I just want to know what kind of % savings we can get.
So Let: Mass pumped per day = 10lb
New Pumping Energy Required = (150ft*g*10) + (235ft*g*5lb) + (470ft*g*5lb)
New Pumping Energy Required = (1500g) + (1175g) + (2350g)
New Pumping Energy Required = 5025g
Now we want to know how much energy we used to use
Old Pumping Energy Required = Lift out of well + Lift all the water 540ft
Old Pumping Energy Required = WellLift(150ft*g*10lb) + HighLift(470ft*g*10lb)
Old Pumping Energy Required = 1500g + 4700g
Old Pumping Energy Required =6200g
Savings:
% Savings = (old– new)/old
% Savings = 100%*(6200g – 5025 g)/6200g)
% Savings = 19.0%
This % savings makes sense. The well pump has to do almost 25% of the work (150 ft out of a total 620 ft) and we can’t improve it. We then only have 75% of the lifting energy to improve on. If we started pumping all the water to a mid mounted tank (and none to the top) we could save half of the booster pump energy (or 37.5% of the total) but we still have to pump half of that water the rest of the way to the top which eats the other 18.75 % of our savings. Our % Savings of 19.0% makes sense because the well pump actually does a little less then 25% of the work (24.2%).
Actual Case:
I made a map of Las Delicious which shows population density as well as elevation. The map was made using Google Earth and the original site drawing, which was supplied to us when we started this project. The map is very unlikely to be perfect. The elevation data has been verified and it seems to agree with what we gathered, but the location of the homes has not been verified. Also the topographical lines were drawn by hand (by someone who is not the most detail oriented) and the counting of the homes is also rough. At the very minimum we should check with someone familiar with the community and see if they agree with the conclusions that I will draw from this map.
Included below is copy of the map
Population & Topography Map Las Delicious
To Make This Map
I took the old original Las delicious map off the internet and took a piece of paper and flipped over my computer monitor and I traced the map. Then I counted the houses and made circles that showed where people live. Then I found this great map that Rich had made (which was the Las Delicious imposed on GoogleMaps) and I recorded a number of elevations. Then I made lines that showed the approximate elevations and the number of people living between each elevation.
I swear non-cheating that the median population line for the community falls just below the median elevation. My map suggests that about 46% of the community lives above 2000 ft. (the calculated median elevation is 1985ft). That would suggest that a slight majority (possibly 55%) of our homes are located below the half way point, which would result in this being a better then ideal solution.
Because of the rough nature of this map I would say to the best of my abilities that that ideal situation is going to be the closest estimate we can make right now.
It may also be possible to improve our efficiency further by placing the 2nd tank higher then half way up, and having it serve even more houses. I can look at my map and make calculations, but I don’t think this map is accurate enough for such detailed work.
This solution absolutely shows potential, but we would maybe have to talk to some people and take more data before we can fully optimize this solution.