Grantee Research Project Results
Final Report: Solar Pasteurizer with Integral Heat Exchanger for Treating Water in Rural Areas
EPA Grant Number: SU833185Title: Solar Pasteurizer with Integral Heat Exchanger for Treating Water in Rural Areas
Investigators: Stevens, Robert , Carrano, Andres , Thorn, Brian , Bailey, Margaret
Institution: Rochester Institute of Technology
EPA Project Officer: Page, Angela
Phase: I
Project Period: August 1, 2007 through December 31, 2008
Project Amount: $10,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2006) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Safe and Sustainable Water Resources , Pollution Prevention/Sustainable Development , P3 Awards , Sustainable and Healthy Communities
Objective:
According to the WHO/UNICEF Joint Monitoring Programme for Water Supply and Sanitation there are currently 1.1 billion people without access to safe water on the planet. Every year more than five million people die from the lack of safe water and improper sanitation. Children are the primary victims, therefore cutting short their opportunity to grow-up and be productive and contributing citizens in their communities. Although there has been significant progress over the past decades to improve access to safe water in urban areas, many existing water treatment technologies are not suitable for rural applications where populations are more dispersed and electrical power supply is unpredictable or nonexistent. A range of alternative water technologies are required to fully address the needs of rural areas. The objectives of this project involve a multidisciplinary engineering capstone design team completing the following:
- enhance solar pasteurizer design with an integral heat exchanger by improving the thermal performance, manufacturability, cost, and environmental impact;
- fabricate several prototypes and have them field tested in Venezuela under a wide range of conditions and redesigning the pasteurizer units;
- develop a business implementation plan for the construction and deployment of the solar pasteurizer to increase the use of the solar pasteurizer and also generate viable businesses for local populations.
Solar pasteurization, as a means of treating water in remote rural areas without electrical power, is based on the principle of using solar energy to thermally kill pathogenic protozoan, bacteria and viruses at temperatures below the boiling point. Solar pasteurization is potentially well suited for home, school, and small health clinic applications. Pasteurization has the unique advantage over other water treatment technologies in that it does not require scarce fuel wood, a source of chlorine, high maintenance, or specialized imported system components. Early solar pasteurization technologies were based on batch systems that had marginal throughput. Higher production rates can be obtained by allowing continual flow through the system using simple flow control devices and recovering the heat from the treated water. Large flow through systems with separate, off-the-shelf solar collection and heat exchanger components have been developed, but are expensive. The novel approach taken in this project is to integrate the solar collection and heat exchanger into a single unit using materials and fabrication techniques readily available in the developing world. This approach has the potential to create a cottage industry producing water treatment technologies which will improve the health of rural populations.
Summary/Accomplishments (Outputs/Outcomes):
The solar pasteurizer multidisciplinary team was composed of seven undergraduate students from Mechanical and Industrial Engineering. Within the two-quarter (22 week) course experience, students work through a formal engineering design process to complete their projects, which is outlined in Table 1.
Table 1: Phases of the design process
During the first phase of the design project the team focused on gaining insight into the people needs by conducting research on both water issues and past work on solar pasteurizers. The team benchmarked by collecting data from existing pasteurizers and other water treatment technologies. The students also met with individuals who have extensive experience with low cost water treatment technologies in Central America and deep understand of the societal and cultural aspects of the rural population in this area. Based on interviews and research, the team developed a list of the “customers” needs. These needs were then mapped into a set of 24 engineering specifications and prioritized from which a Quality Function Deployment (QFD) matrix was developed.
During the second stage of development, the team mapped out the energy and material flow into a functional diagram to help identify the subsystems for design. During the process the team identified seven subsystems; sediment control, feedwater handling, solar collection, heat exchanger, flow/temperature regulation, air regulation, and heat loss management. The team then brainstormed possible concepts for each subsystem. They also looked at existing products and benchmarked analogous solutions. The subsystem concepts were then assessed and ranked using customer needs and specifications and ultimately narrowed to a few concepts for each subsystem.
The team then brainstormed different options for combining the subsystems into a single pasteurizer system. These concepts were discussed and assessed with the customer needs in the forefront. Out of this process, five system concepts were selected for the team to pursue further. The concepts were refined and then the team ranked each concept using a Pugh chart, ranking each concept against one another for each of the key specification/needs used as the selection criteria. The team then narrowed their scope to a three plate concept for further analysis and design. The team held a concept review where the team shared their understanding of the needs and proposed concepts with faculty and experts and solicited their input into the design.
In order to analyze and begin optimizing the selected three plate concept in phase three of the design process, the team adapted an existing engineering model previously developed by the grant principal investigator to simulate the performance of the solar pasteurizer using hourly weather data. The model allowed the team to explore the impact of key design parameters such as heat exchanger material, solar coatings, glazing materials, and dimensions of collector and heat exchanger subsystems on the overall performance as well as their environmental impact. During this phase of design and optimization, special attention was paid to the manufacturability and durability of the pasteurizer.
The team improved the thermal model by incorporating transient operation. Because solar pasteurizing is a highly transient problem, the model uses hourly solar data; however reliable, hourly solar data is not available for Venezuela. Therefore, through comparison of average solar data, the team found that hourly data available for Puerto Rico resulted in similar solar radiation monthly averages. The team then did multiple simulations where the design parameters were varied and finalized on a design that ensured that during the worst month of the year, on average the solar pasteurizer would treat 150% of their pasteurizer specification of 20 liters per day. A pasteurizer of 80 cm x 50 cm with 5 mm deep channels would ensure pasteurization of water and meet the required flow through to meet the daily needs of the users and minimize material cost.
To quantify the impact that the designed pasteurizer would have on the environment, a cradle-to-grave life cycle analysis (LCA) was conducted. For disposing of the pasteurizer, different types of disposition scenarios including land-fill, recycling and a low percentage of municipal waste disposals were selected due to the materials used for the pasteurizer. The product was evaluated according to the Eco-indicator 99(H) method for environmental impact. One thousand eco-points is the yearly environmental load of one average European inhabitant. The pasteurizer gained an overall score of 3.37 eco-points.
During phase four of the design process, the team found that the choice of materials is critical, not only to ensure optimal treated water throughput, but because of the importance of reducing the cost to the end user as well as the goal to minimize negative impact on the environment. The team used Cambridge Engineering Selector in helping narrow the material options. Aluminum was selected as the primary collector and heat exchanger material because it is readily available in Venezuela, has excellent thermal and corrosion resistance properties, while fabrication techniques are possible in most developing world shops.
The team prototyped several of the subsystem components and did tests followed by redesign of the subcomponents. Several fabrication technique were tried in order to reduce the overall complexity of fabrication to ensure the final design could be manufactured without the use of highly specialized tools.
After testing, the team developed a final design plan and then invited local engineers to review the plans and give comments during a formal design review. The team took the input from these local experts and finalized the plan. Part of the final design plan includes a testing procedure for determining whether the final system will meet the specifications the team developed earlier in the design process. The team is currently fabricating the final prototype and plan to begin testing during the months of April and May. The plan includes thermal testing of the system and biological testing to determine the log kill rate of pathogens. Both sets of tests will be conducted at Rochester Institute of Technology.
Conclusions:
The student team successfully achieved the objectives of designing a low cost solar pasteurizer for developing countries while using materials and processes that are less environmentally damaging than alternative water treatment options such as boiling water or chlorination. Plans of completing the remaining project objectives listed on page 1 will be discussed in greater detail in Proposed Phase II section of this proposal.
Proposed Phase II Objectives and Strategies
Phase I in this project addressed proof-of-concept development. It concluded with a prototype designed for rural use in developing countries. Phase II of this project proposes work in three areas:
- Track 1 - Field Testing
- Track 2 - Prototype Design Optimization
- Track 3 - Business Plan Development
As demonstrated in Phase I and in previous work, solar pasteurization has significant potential to provide a passive way of treating water, which requires no addition energy source or ongoing chemicals. Solar pasteurization also appears to be well suited for the small family or community applications for rural areas where water quality may be questionable. The novel approach of this project is to integrate the solar collection and heat exchanger of solar pasteurizers into a single unit and to focus on the choosing materials with low life cycle costs and that are easy to manufacturer using technique readily available in the developing world.
In Track 1 - Field Testing, it is proposed that the final design developed by the team during Phase I and with the improvement made during the optimization track, be produced in quantities, delivered to poor areas in a developing country, and its use monitored throughout a summer season. It is anticipated that a team of three people (two students and one faculty) will accomplish this portion. The specific objectives of Track 1 include:
- Study and quantify the utilization of the technology, rate of adoption, and other statistics on the usage,
- Document the changes in water use habits, diet, etc. due to introduction of a new technology,
- Document the end-of-life practices,
- Develop the production standards and manufacturing data for a mass production environment,
- Capture user feedback on existing design features,
- Develop a general understanding of the cultural barriers impeding wider adoption
It is anticipated that a pilot production of approximately ten solar pasteurizers will be manufactured using fabrication equipment resident in the Kate Gleason College of Engineering at RIT. In addition, approximately ten pasteurizers will be fabricated in Venezuela to get feedback from local manufacturers. Pasteurizers will be deployed at specific sites with user instruction provided. An initial trip during the first part of the summer will accomplish fabrication, education and delivery of the pasteurizers. At the end of this trip, approximately 20 families will walk away with a solar pasteurizer and the necessary instructions for its general use and maintenance. The user families and their water use habits will then be monitored at discrete points in time. Two additional trips will be made during the following year and to gather midpoint and final data.
In Track 2 - Prototype Design Optimization, a multidisciplinary engineering team will optimize the design feature and characteristics of the Phase I design. This team will work during the academic year 2007-2008 to perform a series of engineering analyses (thermodynamics, materials, etc.) aimed to improve functionality and reduce costs. Some of the design aspects to be optimized include channel thickness, insulation material and packing density, collector plate area, valve assembly, thermostat valve temperature rating, and absorber plate material. Various aspects will be contrasted and compromised with the respective cost curve. More complete experimentation should allow for the development of an effective pasteurizer within appropriate cost constraints.
During Track 3 - Business Plan Development, the team will explore how to effectively market the device. A low cost, low maintenance, point-of-use water pasteurizer will be of use to millions of people. Key variables in determining the marketability of such a device are the availability of appropriate fabrication and repair materials locally, and the cost of the device. The Phase I design team focused on reducing the costs associated with manufacturing, delivering, and servicing the devices. To the extent that cost can be reduced and durability enhanced, marketing opportunities will expand.
The final deliverable of this Phase II will be a package that includes: (1) detailed design, performance specs, and manufacturing/distribution plans for a low cost solar pasteurizer;
(2) the quantified economic, environmental, and health impacts versus number of pasteurizers adopted; (3) a proven deployment strategy; and (4) a business and marketing plan that can serve as a guide to those interested in pursuing the solar pasteurizer as an entrepreneurial opportunity. This package will be readily available for government, foundation, non-profit or even for-profit organization that might be looking for a sound opportunity to make a positive impact upon society and environment.
The proposed project represents one of the few multidisciplinary design experiences that will be evaluated against both traditional cost and productivity criteria as well as against broader sustainability criteria. Standard optimization and costing methods and metrics which ignore environmental and social externalities may not be appropriate for a project or product that is to be evaluated against broader sustainability criteria. A very important step forward in increasing the awareness of students with respect to the impacts of their designs on people, prosperity and the planet will have been made once awareness of sustainability issues has been assimilated into the standard design process.
Supplemental Keywords:
water treatment, pasteurization, solar energy, safe water,, RFA, Scientific Discipline, Sustainable Industry/Business, POLLUTION PREVENTION, Sustainable Environment, Energy, Technology for Sustainable Environment, Environmental Engineering, energy conservation, solar pasteurization, sustainable development, solar water treatment, drinking water, ecological design, environmental sustainability, heat exchanger, energy efficiency, solar energyProgress and Final Reports:
Original AbstractThe 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.