In The Classroom

Water Freedom System

Survive Global Water Shortages

Get Instant Access

Dick Anderson

©2006 Dick Anderson

Over the years, things have changed in high school "shop" classes. The days of squaring up a board by hand with a jack plane are over. Today, these classes are called "technology" classes, and they had better be interesting— which means being high tech, hands on, and light on theory. Although we still are required to teach specific shop skills, these skills are taught by using practical applications.

At Darlington High School in Wisconsin, where I teach in the "technology lab," we believe that the next generation will be expected to understand and use renewable forms of energy. We are designing and developing a "working" curriculum to give students real-world, hands-on experience with renewable energy (RE) technologies. Our projects have included wind and solar-electric systems, electric vehicles, and now solar domestic hot water (SDHW) systems.

Solar Innovation
The SDHW project student engineering team—(L to R) Curtis Schulte, Andrew Skog, and Chad Allendorf—unpacks the equipment, inventories the parts, and studies the manual to become familiar with the system specifics.

Practical Application

In my classroom, I use RE systems as the bridge to teach my students basic shop skills. Complex in design and function, RE systems are useful for this purpose, and are great attention-getters. When students see other students working on a unique RE project, they ask questions. The result? The students doing the work get peer recognition, and the students asking the questions learn from their peers.

Most recently, my class put together a demonstration SDHW system. The students working on the project quickly came to understand that having basic skills, like measuring, leveling, soldering, and getting a good fit between pieces, are necessary to build a system. This teaching method also motivates students to study and learn the theories behind the skills, so they can apply them successfully to the project. And instead of relying on me for a grade, students quickly discover that their finished project is the ultimate measure of their skill mastery. Soldering water pipes, for instance, is a self-grading activity—they don't need a teacher to tell them that a joint leaks.

As the students work, and invest time and energy in a project like this, it takes on greater value to them. Their workmanship becomes a matter of pride, and they begin to see how much the wood, the pipes, and the wire are teaching them. The system and its components are demanding. "Just getting by" is not an option—it must work.

The students design the project, build it, and learn from it. I am their resource when they have questions. If they student soar

SDHW Project Challenges

• Build a stable, portable platform

• Correctly size the hot water storage tank

• Accommodate the future addition of a second hot water storage tank

• Slope the collector loop adequately for easy draining

• Provide a means for filling and sampling water from the storage tank

• Incorporate a sight gauge to show the level of water in the storage tank

• Integrate a thermometer into the system to measure the temperature of the storage tank water

• Draw a schematic to show the operation of the system

• Design a data collection sheet to record the system's performance need instruction on a specific skill, like operating a machine or soldering, I can give them a demonstration and advise them to practice until they reach a level of performance they feel will be worthy of the project. If they ask how I would solve one of the problems, I always answer, "What do you think?" Since there's usually no single answer to a problem, students work to find the "best" solutions—the project reveals if their solutions work.

System Specifics

This demonstration closed-loop SDHW system uses a counterflow, tube-within-a-tube heat exchanger to transfer heat between two separate loops of water—a solar collector loop and the storage tank loop. Each loop uses a 120 VAC pump to circulate fluid.

Sunlight strikes the 2-square-foot (0.2 m2) Mini-Gobi solar collector, and heats the water-glycol solution in the copper tubes. A pump circulates this solution through the heat exchanger, where the heat is transferred, via conduction, to the circulated storage water.

The differential temperature control and sensors are the brains of the system. For this demonstration system, a 9°F (5°C) difference between the bottom of the storage water tank and the outlet at the top of the solar collector activates the pumps to begin circulating water. When only a 4°F (2°C) difference in temperature exists, the pumps turn off. Internal dip switches in the Delta-T controller allow the installer to field-set the differential, which would normally be 18:5 for a closed-loop system.

The Helio-Pak 16 unit came with the pumps, heat exchanger, expansion tank, temperature gauges, differential controller, and pressure relief valve, all assembled together. The students' job was to first build a portable platform for the system. Then they had to attach the Helio-Pak unit to the water heater inlet and outlet fittings, and mount and connect the Mini-Gobi collector. During the process of putting the system together, one student suggested that they make the collector adjustable to accommodate sun angles during different seasons. A removable pin in the front of the collector holds the panel in place after its tilt angle is adjusted. This adaptation also required using flexible reinforced polyethylene tubing between the collector and the heat exchanger. Permanently installed systems should always use copper tubing in the collector loop because of potential high temperatures.

The demonstration SDHW system offered students plenty of activities in various skill areas. The woodworkers got involved in the design and construction of the rolling base. The planning students got to make sketches and blueprints. The electrical students puzzled through the electronics of the differential temperature controller. Someone even had to read and figure out how to test and set the controller. And although the plumbing students had a big role in this project, they had to work hand in hand with the other students.

Andrew sweat-solders copper fittings.

Andrew sweat-solders copper fittings.

student solar

Bringing RE to the Classroom

To ensure students get firsthand experience with the actual components they'd handle with in the workplace, the relationship between a classroom model and a full-size system should be as real as possible. Like this SDHW system, many demonstration models can just be slightly modified, scaled-down versions of full-sized systems.

As a learning tool, the models should be portable, so that the system can be demonstrated almost anywhere. This exposes more students to RE, and makes the technology accessible to teachers who want to integrate it into their curricula.

Hot Water Tank Copper Fittings

Chad is learning to judge how tight pipe fittings must be while keeping in mind the alignment to other fittings, like elbows and tees.

Demonstration Hot Water System

Expansion Tank

Drain Fill Valve

Pump

Valve

T&P Relief Valve

Drain Fill Valve

\ Temperature Gauge

Expansion Tank

T&P Relief Valve

Drain Fill Valve

Pump

Hydronic Fill Valve

Drain Fill Valve

\ Temperature Gauge

Valve

Hot Water Supply

Chad is learning to judge how tight pipe fittings must be while keeping in mind the alignment to other fittings, like elbows and tees.

This and other RE projects can provide learning opportunities across the curriculum. Math students can make projections on the sizes of collectors and storage tanks needed for various domestic applications. Language arts students can write up installation and maintenance instructions. Physics students can use the model to study the concepts of heat transfer, radiation, conduction, and convection. Even geography classes can get in on the fun. Using what they've learned about longitude, latitude, hemispheres, and seasonal changes, they can determine the best placement of the solar collectors and predict how seasonal changes affect hot water production. Throughout the year, students can test their predictions, and determine their accuracy.

Hot Water Supply

Demo SDHW System Costs

Was this article helpful?

0 0

Responses

  • cameron
    What a fill valve hydronic?
    8 years ago

Post a comment