Welcome to Water and Electricity for the Navajo Nation
Our goal is to provide a sustainably powered water system for single homes in the Navajo nation. We are a group of Cal Poly San Luis Obispo students who have a passion for sustainable development and helping the world’s people. Throughout this process, we will be working closely with the non-profit organization, Dig Deep, for the Navajo Water Project.
There are approximately 174,000 people living in the Navajo Nation and 40% of these people do not have running water. Additionally, many of them do not have electricity. That is why the goal of our group is to design a cost effective system that is powered by solar energy to provide running hot and cold water, LED lights, and charging ports.
- 1200 gallon cistern per month per household- Assuming an average of 30 days/month, this equates to 40 gallons per day.
- The amount of sun the solar panel could receive a day- During the summer with maximum sunlight hours and power, the solar panels can deliver 7 kWh and during the winter months with minimum sunlight hours and power, the solar panels can deliver 4 kWh.
- The Navajo Nation gets cold enough during the winter months that water freezing in the pipes is something to keep in consideration.
- The flow rate out of the sink at 1.5 GPM
- The location of items already installed in the homes- The cistern is usually 1.5 feet away from the home on the side of the home with the pump. The sink is usually placed on this side as well
- Structural integrity of the homes- The roofs are not sturdy enough to support a load of this magnitude if we were to put a water tank on the roof for a gravity propelled system
- Water in the water heater must be kept above 140 F
- Cost- we would like to reduce the cost of the system from their current cost of around $3,291
The Navajo Nation is a Native American territory that covers 27,425 square miles and spans three states (Arizona, New Mexico, and Utah). They are considered a sovereign nation with their own government. As of 2010 the Navajo Nation population numbered roughly 174,000 people, and 40% of those families are living without running water. The poverty rate for children is around 44%, while the unemployment rate for adults is approximately 48.5%. With the lack of one of life’s basic necessities, there is a cycle of poverty that poses many threats to the future of these children. While there is an increased level of poverty, the day-to-day life of the nation’s people is not immensely different than that of the average American. As the largest reservation in the United States, the Navajo Nation and its people are incredibly diverse. The specific area that we are working with is near Smith Lake in New Mexico because that is where the well is located, from which water is being provided. On the map, the small image in the top right corner shows a perspective of where the Navajo Nation is in the United States. The portion highlighted in yellow is Smith Lake and the red is the nation’s border.
Research was conducted with regards to using a commercially available electric water heater that can be used to provide a Navajo home with heated running water. The water heater, powered by solar panels, will function at 140°F according to OSHA recommendations to prohibit microbial growth. Hot water will be mixed with cold water to achieve temperatures between 60°F and 140°F. Based on on NREL solar radiation data for the Navajo Nation region, the solar power needed is 580 W for every 10 gallons of water in the conditions least desirable for solar power generation. With only 40 usable gallons per day, half can be delivered at 100°F, which is an ideal temperature for bathing. With these goals met, target homes can have their first access to heated running water.
Throughout the design process, we ran into problems that hindered our project, but added to our learning experience. Since we learned about the value of failure in this class, please view our failure report.
Design Matrix for the Water Heater
(1) The industrial electric heater can be bought. This would be your typical electric tank water heater.
(2) The homemade electric heater would be made in shop and composed of a tank, insulation, a thermometer, and a heating element.
(3) The flat plate collector uses thermal energy from the sun and dark pipes to heat up the water. This technology would require a second loop consisting of a liquid aside from water so that it does not freeze in the pipes during the winter.
(4) The thermosyphon is another form of solar heater that uses thermal energy from the sun.
(5) The batch collector heats water in a dark tank with reflective material to concentrate the sunlight. This technology is limited by only being able to heat one “batch” or tank of water at a time.
Based on our design matrix, we chose to pursue both the industrial electric and homemade electric water heaters.
Progress Made in Shop
We constructed a homemade water heater. The materials for construction include:
-10 gallon steel drum
-32 gallon plastic trash can
-bulk heads and other pipe fittings
-DC heating element
To view our step-by-step contruction manual, please click here.
We connected the water heater to the 425 W solar panel at the student experimental farm. Pete’s Physics of Energy class assisted us with the circuitry and hardware required for the solar panel hook ups. While the water heater would run as a continuous system in reality, for testing purposes we ran the water heater as a batch system. This is different, however, from the batch collector option in the design matrix as the batch collector uses reflective material to concentrate the sunlight. We filled the tank and monitored the water heater. In 5.5 hours, the water heated up 47 F from 72.4 F to 119.4 F. We built the water heater with the heating element in the top of the tank with the thought process that a full convection would be created. Initially, the tank did not achieve the convection we were hoping for, so we stirred the tank after each measurement taken and then took measurements at the top and bottom of the tank again. Unfortunately, at 5.5 hours, the solar panels became disconnected and we had to conclude testing. A graph showing how the water heated over the course of time is shown below. The insulation provided ideal settings so the
After testing, we concluded that a homemade water heater is not ideal for the Navajo Nation. The water would take well over 6 hours to heat to 140 F. Additionally, the homemade water heater was only marginally cheaper than an industrially made water heater, but required a significant amount of construction time and effort. However, the homemade water heater has the potential to create jobs within the Navajo Nation, which considering their high local unemployment rate, may be worthwhile.
We found many ways how not to do this project, which we have summarized here in a failure report.
Recommendations for DigDeep
After building a homemade water heater, our recommendation for DigDeep is to include an industrial electric water heater in their system’s design to replace their tankless propane water heater. One of the key reasons for staying away from propane is the increased dependability of the system. There will always be solar power available (even if it is limited during cloudy days) but a system that depends on propane to power the heater is dependent upon supply. If there is a missed delivery, shortage, the family uses it too quickly or similar situtaion, they could go without hot water for an extended period of time.
A cost comparison between the current water heater system and our proposed water heater system can be found here. The industrial water heater would need to be retrofitted with a DC heating element and thermostat to properly operate with the DC photovoltaic solar panels. In addidion to the solar panels powering the system, a 12 volt DC battery will be included in the circuit to allow the LED lights, charging ports, and pump to run at night when the sun has set. With this recommendation, a diversion load charge controller should be used since it allows the 12 volt batteries to fully charge before putting power into the heating element within the water heater (see Figure 1 below). The charge controller works by sensing the voltage across (or amount of charge in) the battery, allowing the system to charge the battery when it is low or divert the power to the “diversion load” heating element when the battery does not need to be charged. A more detailed overview of the entire system circuitry is shown in Figures 2 and 3.
Figure 1: Charge Controller Placement and Circuit Overview
Figure 2: System Circuitry with Charge Controller
Figure 3: Overall System Circuitry
Other design changes to note include a new pump, 700 required watts from the solar panel compared to the 150 watts currently required, and the elimination of the necessity of propane for heating water purposes. Additionally, with the replacement of an industrially made electric water heater tank, the vents included in DigDeep’s current system are no longer necessary. A schematic of our design can be seen below in Figure 4. All other elements of our design can be seen in the Cost of our Proposed System spreadsheet. Ultimately, there are many factors that go into choosing which system design to implement.
Figure 4: Pump and Piping System
Recommendations for Further Research
Improvements to water heater prototype
After analyzing where the constructed heater prototype had its downfalls this quarter we have a few recommendations to look into for improvements and possible feasibility for application:
- research cheaper steel drums or similar containers to reduce costs of the prototype
- reduce solar panel size for more efficiency – there may be a chance of insufficient hot water supply in cold and cloudy months however
- improved insulation for better heat retention
- optimum locations of inlet, outlet and heating element for efficient and even heating
Bath Water Heater System
During this project Pete Schwartz suggested to look into a design including a water heating system that incorporated a hot water bath system.
We have designed a preliminary version of this system with basic calculations and see potential for this technology in this application.
The design will have the following features:
1. Hot water bath with thick insulation, volume and water temperature to be determined by calculation depending on client needs and power supply choices. The water in the bath will be reused and never consumed so will be chlorinated to prevent insect and disease complications from standing water.
2. Copper piping snaked through the bath, entering from the cistern and outputting into piping connected to the sink
3. Heating element and solar panel circuit system to maintain bath water at specified temperature
Basic visual of the design:
Attached is our excel file with the calculations for the theoretical model. The file is set up with constants and variables in table format to calculate the length of pipe needed inside of the hot water bath, which then will allow you to determine a reasonable size for the bath to calculate heat loss through walls.
The variables to be determined by the user:
1. Initial water temperature
2. Exit water temperature
4. Bath water temperature
5. Pipe Diameter
6. Dimensions of the water bath
Please feel free to contact any member of our team to answer any questions or for further assistance.
(left to right)
Armando Ruiz – Philosophy and Biotechnology Student firstname.lastname@example.org
Anna Laird – General Engineering Student email@example.com
Emily Miller – Environmental Engineering Student firstname.lastname@example.org
Kelly McGartland – Environmental Engineering Student email@example.com
Jessica Talbot – Civil Engineering Student firstname.lastname@example.org
Tyler Dery – Environmental Engineering Student email@example.com
Pete’s final words on website:
Great work. I Love the failure report. I should revisit this in the coming months. The DC battery is way way overkill for an LED / pump system. I think you could save $200 by getting a smaller battery and charge controller. You said it didn’t convect properly. However, it seems that it convected fine judging from the temperature (before mixing) data: There was less than 10 F difference between top and bottom. The load for electrical system is way small compred to that for heating water. … like 1/10th. Therefore, I think rather than having a diversion load charge controller, you should just run a small charge controller to a small battery in parallel with the solar panel and get solar panels that are of higher voltage than the charge controller, so the charge controller will be prioritized.
most of Pete’s comments were unintentionally deleted before they were moved down here, what is shown is only a part of the original comments
– There is little discussion of the electrical system. Can you please describe what this will look like? What kind of charge controller, battery, etc. will you use? Maybe you can have the PHYS-310 group do this? Please have a schematic of what the wiring for the electrical system and a different schematic showing the piping system, and the prices.
-Additionally, please include a consideration of the “heat exchanger” home made water heater. The other group should do a calculation as to how long the copper tubing inside the heat tank should be at the given pumping speed to deliver water that is only ~ 5 degrees colder than the water in the tank.