Grantee Research Project Results
Final Report: Water Collection, Containment, and Self Regulating Distribution System
EPA Grant Number: SU835070Title: Water Collection, Containment, and Self Regulating Distribution System
Investigators: Lilly, Brian , Ward, Thomas
Institution: University of Illinois Urbana-Champaign
EPA Project Officer: Page, Angela
Phase: II
Project Period: August 15, 2011 through August 14, 2013 (Extended to February 14, 2014)
Project Amount: $74,985
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2011) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Air Quality , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
According to the EPA, “Light-duty vehicles in the U.S. produced 1152.6 Tg CO2 Eq. in 2003, representing 77 percent of on-road vehicle GHG emissions and 62 percent of total transportation emissions.” Among these vehicles are municipal and privately owned trucks which travel up to four times weekly to water large planters scattered throughout cities, towns, hotels, airports, stadiums, office buildings, universities, etc. However, the vast majority of these planters are designed for aesthetic appeal as opposed to efficiency. In order to achieve proper growth, potted plants need to be placed over only six inches of soil, yet one would be hard-pressed to find a planter with such a depth. As a result, most horticulturists use cheap soil or even Styrofoam to fill in the additional space inside of the planter (below the six inches of premium soil). By implementing a system in this “additional space” which allows for onsite water storage with efficiently regulated on site watering, we are working to reduce planter maintenance costs and associated vehicles emissions by up to 90 percent, and reduce the amount of water used to maintain healthy plants.
Our research is focused on coming up with a cost effective system to install within the planters. More recently, the scope of our work has increased to regulating off the grid rain collection containers and building complete planter systems. This can be accomplished with solar panels, custom circuitry, moisture sensors, and pump.
Summary/Accomplishments (Outputs/Outcomes):
Objective 1:
In terms of selecting optimal equipment, the ‘individual planter’ unit was by far the most difficult. It wasn’t necessarily the electrical hardware (pumps, batteries, solar panels, etc), but the physical planter itself that proved extremely challenging. During the course of the Phase I and Phase II projects, it became increasingly clear that a universal system to be implemented in any planter would be impossible. There are simply too many different shapes, sizes, planter depths, and materials to design for. With this in mind the team began to design a custom made planter with the help of an industrial designer. The initial requirements were simply based on dimensions. It did not matter if the planter was cylindrical or square, what mattered was the internal volume of water it needed to contain. Given a required depth for certain plant life of about 6-8 inches and a desired planting area of about 450 square inches, the team estimated a required watering of approximately 5 gallons. In order to achieve the desired result of 90% savings in labor associated with planter ‘waterings’, the planter needed to have a height approximately 34 inches. With the general dimensions set, the following planter requirements were also addressed (to name a few):
- Overflow release mechanism
- Built in Solar Panel and protected electronic control housing
- Ability to fill container from outside (without dissembling)
- Ability to remove pump/electronics during winter
- Ability to prevent tipping or unit theft
- Ability to clean inside of tank
Due to other factors such as price, ease of use, weight, and durability, we decided a plastic option would be best. With the information above, we began to iterate. The final design (which can be seen in the final report) consists of an aesthetically pleasing planter built in two sections with the top being removable. The internal cavity, stabilized by double plastic walls holds over 50+ gallons of water. Coupled with the soil volume and a maximum (for most applications) required discharge per ‘watering’ of 5 gallons, the container provided a theoretical 90% reduction in maintenance. The solar panel is also built into the planter and provides protection for the electronics below.
Once the physical planter was developed it once again became down to component selection. Due to the versatility of the circuit design, the selection of all three units (large municipal applications, individual planter applications, and home use models) came down to price and performance. In terms of batteries, the decision was made to go with sealed lead-acid units due to their favorable recharging abilities, and low cost. With both batteries and solar panels, the size selected was dependent on the power necessary for the application. For pumps, brushless bilge pumps were used because of cost, durability, and their ability to move great amounts of water while consuming little electrical power. All connections were made with universal ‘plugs’ or ‘connectors’ which not only allows for easy replacement (no need to solder wires) but also gives the ability to easily change components (larger or smaller pumps, solar panels, batteries, etc). The moisture sensor used was the same for all applications but the decision making process was complex.
Objective 2:
As mentioned in the Phase 1 results, an effort was made to reduce the cost of the moisture probe circuit combination. In order to make the product commercially viable, it was of great importance to have a low cost yet reliable moisture probe. The development team tested numerous “off the shelf” low cost sensors during the initial phase of the project. Although these sensors provided a general sense of wet and dry, they were not highly accurate nor were they durable over long-term deployments. Once the Phase II grant was approved, a portion of the funds went toward developing a custom moisture probe with two objectives. First was to reduce the per-unit manufacturing cost. Second was to improve the accuracy over the probes used in Phase I. The general design included the use of two stainless steel rods (stainless steel does not corrode), approximately 5 inches in length, held together at the top and separated by approximately 1 inch of plastic material (see “Moisture Probe” image below). Once the prototype was built, weeks of testing were necessary to calibrate the probes.
The science behind the probe is relatively simple and uses measurements from both probe ends to determine the overall moisture level of the soil. A voltage (5 Volts) is sent through the first probe end. The device then measures the voltage on the second probe end. The difference in voltage between the two probe ends allows the device to determine the volumetric water content of the soil. For example, if the soil is completely dry there is no way for the electricity to travel from one probe to the next, therefor the voltage on the second probe would be around zero Volts. However, if the soil was completely wet, the electricity would be able to travel through the liquid and the voltage would be around three Volts (if they were connected by copper you would see around 5V). Finally, if the soil were somewhat moist, you would expect around two Volts. By testing the voltage on the second probe over various moisture levels, a moisture curve can be created giving an expected voltage per the soils volumetric water content.
However, there are two more variables, which affect the results. First is the salinity of the water. As more salt enters the water, electricity begins to flow easier through the liquid and therefor affects the results. Second is the density of the soil. For example, if the soil is moist and dense electricity will flow easier than if the soil is moist and loosely packed. Unfortunately it was during the testing of soil density that our team was faced an unexpected result. While we knew the composition of soil used and the salinity within the soil would affect our probe readings, the assumption was made that if the team dictated the soil to be used the readings would be somewhat consistent. While this is true in laboratory conditions it is not in real life applications. Depending on the plants used, acidity of rain, source of water, and many other factors, the salinity within the soil is simply too unreliable. Due to this fact, the team decided to revert back to the industrial probe used in early prototypes. The industrial probe has a price tag of nearly $30, but is highly accurate, extremely low power, insensitive to salts, very durable, and accepts a wide range of voltage outputs. The shift away from probe development allowed the team to focus the end product, and shifted our focus away from the home unit for the short term.
Objective 3
Without economies of scale and unexpected costs (like the probe mentioned above), the focus shifted away from the home model to the to the individual planters and the larger municipal units. In terms of the individual planter implementations, the team did not have the budget to create molds for the final product (can be seen in the final report). With that said, the project enjoyed great success in terms of individual planter prototypes. By taking the core elements of a solar panel charging a battery, and the battery powering the circuitry, moisture probe, and pump, great results were obtained. Instead of planters build off of our final designs, the team used aluminum buckets to simulate the estimated planter area. Six full prototypes were then planted side by side in Illinois.
Due to the climate in Illinois, prototypes were deployed in the summer as the region’s temperature increased. The experiment included a control planter, to be watered manually, and six other planters watered entirely by the Waterbelly systems. The planters were numbered 1 to 6 (“All systems without Control: During Installation” image can be seen in the final report). Planter numbers 2 - 6 utilized a timer (in addition to the moisture probe) to control the pump time, therefor guaranteeing five gallons per pump. The timer also prevented the pump from being activated twice within a 48-hour period to prevent overwatering. Planter 1 was controlled entirely by the moisture probe. The function of the moisture probe in all six Waterbelly systems was to measure the moisture level in relation to the “dry point.” The dry point is the level of volumetric water content at which the moisture probe signals that the pump should turn on; this value varied for planters 2 – 6. A dry point value of ‘200’ (where 0 Volts represents 0 and 5 Volts represents 1024) was chosen for planter # 1. Throughout the summer, data was collected to determine which planters were watered on which day, and how much water was used. Once the growing season was over, the plants were examined to assess health. When the season was over, data was analyzed and it was determined that a value of “186” was optimal (where 0 Volts represents 0 and 5 Volts represents 1024). This number is specific to the moisture probe used and does not have significant value outside of this perspective.
In additional to the individual planter applications, the team was able to see great implementation success in regards to the large municipal units. Through the publicity that came with EPA P3 success, a conservation district near the University of Illinois contacted the team to implement a large unit next to their new environmental educational building. The scenario was perfect. The educational building would be able to collect runoff water from the roof and funnel it into a 1000-gallon underground tank by way of the gutter system. The larger Waterbelly unit would then tap into the 1000-gallon tank and automatically water an 80-foot range of plants in from of the building. This would not only save thousands of gallons of water (using runoff instead of tap water) but it would also save thousands of dollars in labor over its lifespan (exact amount to be determined). As mentioned previously in the report, the circuit was built to scale. This allowed us to ‘plug in’ a 30 Watt solar panel, 18 amp-hour battery, and a 600 gallon per hour bilge pump (results pictured in the final report).
Conclusions:
In order to achieve positive environmental and economic impacts through reductions in water usage, carbon emissions, and maintenance costs, the Waterbelly product needs to be one that is financially viable, rigorously tested, highly accurate and durable. With the assistance of Mike Elwell, our team was able to create a visually striking planter that solved all design obstacles during the nine-month re-design period. Additionally, the design incorporates a 50+ gallon holding tank, which will reduce planter maintenance costs and associated vehicles emissions by over 90%. One of the components that allows for this technology is a highly accurate moisture probe for only $40, whose value and accuracy was confirmed through months of prototype testing. The Waterbelly system has produced healthy plants through circuit controlled water regulation. The final objective mentioned was implementations and a move toward commercialization. While this is an ongoing process, our team completed the first sale of Waterbelly technology (the large municipal unit) to a Conservation District in central Illinois in the summer of 2013. After nearly a year of testing this unit, the goal is to continue distributing the larger units to municipal workers and promote environmentally sounds product creation and usage.
Supplemental Keywords:
cost benefit, water, carbon dioxide, design for environment, moisture probe, resource recovery, solar powerRelevant Websites:
Progress and Final Reports:
Original AbstractP3 Phase I:
Solar Powered Water Collection, Containment, and Self Regulating Distribution System | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.