Human-Powered Potable Water Still

SYSTEM DESIGN REQUIREMENTS

TESTING PROCEDURES

SCORING

COMMITTEE COMMENTS

SYSTEM DESIGN REQUIREMENTS

For this contest, the specific device requirements and procedures will be as follows: 

1. Each team must arrive with their device and its support equipment, if any, packed into the smallest rectangular parallelepiped box it can fit into. Immediately after check-in each team must report to the judging team to have the outside dimensions of their storage box determined.  This volume will be used in the scoring of this contest.  (Smaller is better!)
2. In any event, the storage box must be small enough to meet shipping requirements, which are determined as follows:  
       a. Measure the longest dimension of the storage box.  That is the “Length”. 
       b. Measure the circumference around the box in the plane normal to the length 
           measurement. This is the “Girth”.
       c. When added, Length plus Girth must be less than or equal to 4.2 m
3. Once the storage dimensions have been determined the teams must assemble their devices and take them to the judges for weighing in the “dry” state.  All system components must be included in the weight.  This includes auxiliary equipment needed to operate the still.  For example, any separate charging aids such as funnels must be included.  This weight will also be used in the scoring.  (Light is better!)
4. Energy input can be by any convenient mechanical means driven by human effort.  Examples would be pedal systems, linkages, lever systems, cranks, etc.
5. The human mechanical energy input can be changed to any other kind of energy and as many different kinds of energy as desired in the process of heating the water.
6. The use of a vacuum in any part of the system is permitted, but the vacuum must be generated and maintained by the human operator. 
7. Two bottles of “polluted” water will be given to each team prior to the start of the timed period.  One of these bottles will contain 200 ml of “polluted” water.  The second bottle will contain a weighed and recorded quantity (approximately one liter) of “polluted” water.  All of the water will be at room temperature, as verified by measuring with a thermometer. 
8. An amount of food coloring sufficient to visibly alter the color of the water will be added to the water given to contestants..  This will simulate the salinity and other pollutants for the purposes of this contest.  Due to the nature of the distilling process, this will not carry through into the condensate.  Each team will be required to charge their still with a minimum of 200 ml of “polluted” water from the first bottle they are given.  Teams wishing to charge greater amounts of water will need to make arrangements with the judging team for proper measurement of the quantity prior to the start of the testing period.
9. Polluted water may not be added to the device once the initial charging is completed.  Water may not be added during the course of the run.
10. Aside from minor amounts of water inside connective tubing or piping, all water inside the device must be held in no more than two polluted water reservoirs or heating chambers.  All other water must show up in the calibrated output catch basin.
11. Any time the judges observe spilled “polluted” water they will require that the team clean up the spill, and the team will incur a 5% automatic decrease in the water weight value used in computing their score.
12. Each team must arrange to have the “outside temperature” bulb of a digital indoor/outdoor temperature gage (or its equivalent) in the water inside the still at all times during operation so that water temperature can be continuously monitored.  If the “input” water is held in two chambers, then the estimated quantities in each chamber and the temperatures in each chamber must be displayed, kept track of, and given to the display and scoring officials. The digital temperature readout(s) must be easily readable by judges and nearby spectators.
13. Teams must attempt to condense any steam escaping from the human-powered still.  The weight of recovered condensate will be the major factor in the scoring.
14. The final quantity of distilled water will be determined by weight to at least the nearest 0,5 gm.  Thus the collecting vessel in which any condensate will be collected must be weighed prior to the test in a dry state to determine its tare weight.  All such vessels must be clearly marked with the team name and tare weight.
15. Any waste water (e.g., concentrated “polluted water” left in the still at the end of the run) must be collected by the team in a second vessel of some sort either during or after the run.  All water issued to the team must be turned in to the judges and accounted for at the end of the run, not just the water distilled by the team.
16. The still must be empty and dry at the beginning of the test run, and as empty and dry as possible at the end of the run.

TESTING PROCEDURES

1. All contestants will be distilling at the same time.  The timed test period for all teams will be 60 minutes.  When the start signal is given teams may charge their devices with the “polluted” water and begin operating their device. 
2. Teams may split work input times among themselves in any way they see fit.  It is not required that all team members participate in this.  Any person providing the work input must be a bone-fide member of the design team, not someone recruited only for the work input part of the contest.   All teams will be required to fill out and sign a report form at the contest indicating the date at which the team was formed and started work, the dates on which each team member joined the team, and very brief descriptions of the contributions of each team member to the project.  Large variances between the team formation date and the individual team joining date, or evidence of little or no contribution to the project may be grounds for possible elimination as an operator of the device.  Such elimination will be at the discretion of the judging team, is final, and is not open to challenge.
3. A team member with a physical disability which would prevent him or her from operating the team’s device may be replaced by a substitute of “average” physical ability.  Substitutes must be approved by the judging team at the contest, and substitutes need not come from the same school as the design team.
4. Only one team member may operate the device at any one time.  Multiple simultaneous operators are not allowed.
5. As the test period proceeds roving judges will continuously record the current water temperatures each team is reaching.  Temperatures reached in each device will also will be reported on a timely basis to a central scorer for entry on a spreadsheet by volunteer (student) runners.  A student “runner” may not report values for a team from his or her own school.  Entered on the spreadsheet prior to the start of the run will be the weight of water charged into the still at the start of the heating process and information on any splits in storage location within the device.  As the run proceeds a score representing total thermal gain of and condensate collected by each team will be projected in bar-graph format in as close to real-time as possible on a large screen for everyone to see as the contest progresses. (Note that this displayed score will not include the size and weight factors, and the projected scores must be treated as provisional, not final contest scores.)
6. Any condensate from the still must be collected in a clean, clear vessel calibrated in one milliliter steps and supplied by the team.  If and when the team begins to distill water across into the receiving vessel (and the temperature of the still thus reaches a stable point) the runners will begin to report the volume of the condensate to the nearest 0.5 ml as well as the current temperature.
7. At the end of the 60 minutes and at a signal from the time-keeper the receiving containers for any distilled water will be removed and may be covered.  The containers will then be moved to the measuring location, where the quantity of any distillate will be determined by weighing. 
8. In order to be counted in the scoring, distilled water should be visually color-free.
9. Teams are also responsible for accounting for all of the water they were issued for charging their stills.  At the end of the run all teams are responsible for recovering all of the water from their device and taking it to the measuring station along with any of the water they were given that they have not used.  The judges will check the total weight of returned water.  If less than 90% of the water given to a team is present at the end of the run the score the team receives will be adjusted as follows:
   
   Adjusted Score = Raw Score  * [(1.1 * wt of water returned)/(wt of water issued)]

SCORING

At the end of the one-hour test period, the winner will be the team which maximizes the score according to:

SCORE  =  (Weight of distilled water, gm) * 10,000

                + (Wt of test water in device, gm, at end) * (Tend – Tstart, C)

                - (Dry weight of the device, gm.) / 100

                – (Volume of box in which device can be packed, cm^3) / 1000

Notes:

1. All scoring values and calculations will be rounded to the nearest integer value.
2. If the water in the test device is contained in more than one reservoir then the weights of water in each reservoir at the start will be multiplied by the difference between temperatures in that reservoir at the start and at the end of the test to determine the second scoring factor.

COMMITTEE COMMENTS

The SDC Committee has received periodic requests for a “head-to-head” type of contest.  Logistical and seeding problems have generally not made this practical.  But this year we have come up with a contest where everyone will run at the same time, and spectators will be able to watch and compare the results in nearly real time.  We think this will provide an exciting and interesting contest.

This contest differs from previous years’ contests in one other important aspect.  This time the power input to the device must come from work input by the team members.  Thus it is clearly advantageous for a team to include at least one person who is in good physical shape at the time the contest is run.  This should be kept in mind as project teams are formed to compete in this contest.  Note, however, that bringing on board a person whose only contribution to the project is physical work input violates both the spirit and the letter of the rules.  Please review the requirements set down for team members who will be operating the machine and make sure that the information asked for is available to the judges at the contest.

The SDC Committee does not believe that this contest will be won or lost primarily on the physical strength and endurance of team members.  There are too many other factors which enter into the design and competition processes.  These include the design of an effective human interface, the quality and effectiveness of the thermal insulation, the thermal mass of the device inside the insulation envelope, the effectiveness of the heat rejection/condensation process equipment, any thermodynamic energy conservation measures implemented, and effective use of team members in the competition.