Solar Water Pump Challenge
Welcome to Reiman Gardens. For the next two hours, you're going to be doing real engineering in a real botanical garden — designing, building, and testing a solar-powered water system from scratch.
Before we head outside, you're going to meet your team. For each question, walk to the corner of the room that matches your answer. You'll have about 30 seconds in each corner to introduce yourself and say why you picked it — then we move to the next question.
- Corner A: A solar-powered fountain at the entrance
- Corner B: A rainwater collection system that feeds the garden beds
- Corner C: A pollinator water station for bees and butterflies
- Corner D: An interactive water-flow garden visitors can play with
- Corner A: Follow the instructions exactly
- Corner B: Sketch a plan first, then build it
- Corner C: Dive in and adjust as you go
- Corner D: Improvise with whatever's around
- Corner A: Solar / renewable energy engineer — designing power systems
- Corner B: Water systems engineer — moving water across cities and farms
- Corner C: Agricultural engineer — irrigation, soil, growing systems
- Corner D: Environmental engineer — protecting ecosystems and resources
Notice where you ended up. Some of you are going to think like builders today. Some like planners. Some like inventors. You'll need all of it.
Solar panels turn sunlight into electricity. Pumps turn electricity into moving water. Put the two together and you can move water across a garden, a farm, or a remote village — anywhere the sun shines and water needs to flow, without plugging into anything.
Reiman Gardens is exploring renewable-energy demonstrations for visitors to the Big and Small exhibit. They want to show how solar power can move water through a garden — no batteries, no extension cords, no outlet in sight. They've asked your team to design and build a working prototype.
You're going to do this in three rounds: test your panel outside, build your first system, and iterate until you've got something that actually moves water.
- 1 small solar panel (pre-wired with red + and black − leads)
- 1 multimeter, set to DC voltage
- 2 alligator clip leads
Watch this first — it shows how to read voltage off a multimeter.
Test procedure:
- Clip one multimeter lead to the red (+) wire on your panel, the other to the black (−) wire.
- Set your multimeter to read DC voltage — the V with a straight line above it, not the wavy one.
- Take everything outside. Hold the panel flat in your hand and read the voltage.
- Now tilt the panel toward the sun. Did the reading go up or down?
- Move to a shaded spot and read again. Then back to full sun.
- Aim the panel face directly at the sun, not flat to the ground.
- Tilt it slowly while watching the multimeter — the right angle is wherever the voltage peaks.
- Even a small shadow tanks the reading. Keep the whole panel in clear sun.
- The "best" angle changes through the day as the sun moves. Find it right now.
- Highest voltage you got and where/how the panel was positioned
- Lowest voltage and what changed
- Best angle to the sun — flat, tilted, or steeply tilted?
- 1 mini submersible water pump
- ~12 inches of clear tubing (you'll attach it to the pump)
- Your solar panel and alligator clips from Part I
- Water source bucket (where the pump sits)
- 250 mL graduated cylinder (where water gets delivered — and your measurement tool)
- Plastic tray to catch leaks
- Recycled containers, tape, rubber bands, binder clips, craft sticks, skewers — for structure
- Paper towels for spills
Your pump is a DC motor. It only runs one direction. If you connect the wires the wrong way, the pump won't spin — it'll just sit there silent, looking broken.
If your pump doesn't run when the panel is in full sun: swap the alligator clips so the red lead goes to the other wire. This fixes nine out of ten "broken" pumps.
Watch this — it shows the connection.
Build procedure:
- Slide one end of the tubing onto the pump's outlet (the small nozzle). Push firmly — it should grip on its own. This is the connection that leaks first if it's loose.
- Fill your water source bucket about halfway with water. Set it on the tray.
- Drop the pump into the bucket — it has to be fully submerged to work.
- Stand your empty 250 mL graduated cylinder where you want the water delivered. Position the open end of the tubing so it points down into the cylinder.
- Connect the panel to the pump: red wire (+) to red wire, black wire (−) to black wire. Take the panel into full sun.
- If water flows: you're a working engineer. If nothing happens: swap the wires (see warning above).
- Build a structure with craft sticks, tape, and recycled materials to hold the tubing steady and the cylinder upright. Your system needs to run hands-free for 30 seconds without spilling.
Run 1 — 30 seconds:
- Bucket full of water. Graduated cylinder empty and standing under the tubing.
- Hold the panel in full sun. Start the timer the moment water starts flowing.
- After 30 seconds, disconnect the panel.
- Read the volume directly off the cylinder. That's how much your pump moved in 30 seconds.
- Convert to flow rate: volume × 2 = mL per minute. (Example: 80 mL in 30 sec = 160 mL/min.)
Pick one change, then run again:
- Shorten the tubing — less distance, more flow
- Lower the target cup — less lift, more flow
- Improve the structure — fewer wobbles, less wasted water
- Reposition the panel — find a better angle to the sun
- Seal a leak — every drop that misses the cup is wasted
Run 2 — try 60 seconds this time (you'll get better data with a longer run):
- Empty the cylinder back into the bucket. Reset.
- Run for 60 seconds in full sun — but if the cylinder gets close to 250 mL before 60 seconds, stop early and note the time.
- Calculate flow rate: volume ÷ time × 60 = mL per minute.
One last 60-second run with your best design (or shorter if the cylinder fills sooner). Lock in your final flow rate.
In peak summer, the horticulture team waters different plants differently:
- Small annual flower (marigold, pansy in display beds): ~250 mL/day
- Pollinator garden coneflower: ~500 mL/day during dry stretches
- Young rose bush in the Buck Rose Collection: ~1,500 mL/day in summer heat
- Tomato plant in the demonstration garden: ~2,500 mL/day in summer
Now the real question. If your pump runs for 30 minutes a day in full sun, how many of each plant could it actually water? Do the math:
Your flow rate × 30 minutes = daily output (mL)
Daily output ÷ plant's daily need = number of plants your pump could feed
Then walk into the gardens with your team. Find the kind of plant your pump could realistically support. What would need to change about your prototype to make it work outside, all summer, in real Iowa weather?
Renewable energy engineers and water systems engineers design these systems for a living — at scales from a single pollinator water station to a thousand-acre solar farm pumping irrigation water across rural Iowa. Right now, Iowa is one of the biggest renewable-energy producers in the country, and engineers here are figuring out how to power farms, towns, and factories without burning anything. The prototype you just built — solar panel, pump, water moving without an extension cord — uses the exact same principles as systems running in fields and feedlots today.
Each team has 90 seconds to present. Bring your 📋 Reiman Gardens Field Notebook and your prototype — your data and your design are your evidence.
- What was your final flow rate?
- What was the biggest improvement you made — and how did you know it worked?
- Where would you install your design at Reiman Gardens — and what would you have to change?
Instructions (Part III): Careers in Wind and Environmental Engineering
The work you did today connects directly to real careers:
Wind Energy Engineer — designs and tests turbine blade geometry, models power output for wind farms, and analyzes site conditions to determine where turbines should go and why. Your blade variable testing today uses the same logic at a different scale.
Environmental Scientist — monitors ecosystems and measures climate variables in the field. The micro-climate observations you made outside — wind speed, temperature variation by location — that’s real field science methodology.
Meteorologist — studies weather patterns, wind behavior, and atmospheric conditions. Understanding micro-climates in outdoor spaces like gardens is part of applied meteorology.
Electrical Engineer — designs circuits and power systems. The series vs. parallel wiring test you ran today is a fundamental concept in electrical engineering.
Landscape Architect — designs outdoor spaces with environmental performance in mind, including wind patterns, shade, and thermal comfort. Knowing where wind moves through a space like Reiman Gardens is part of their job.
Want to learn more about any of these? Ask before you leave.