Solar Thermal Technologies

Food dryersSolar OvensAir HeatersGreenhouses & cold framesSolar Water Distillers

Introduction:

This 20-image presentation is designed to provide a brief overview of the technologies learned in the solar-thermal course.

Much more material is offered than shown here. However, this presentation does give an idea of the material students are exposed to.

Dr. Dennis Scanlin in the Appropriate Technology Lab

Course Purpose:

To introduce students to technologies that make use of the sun’s free energy

Students learn that they can heat houses, water and food with solar radiation and without having to use the world’s limited fossil fuel resources

The class combines lecture and “hands-on” practical experiences developed by Dr. Scanlin over a period of two decades to convey the information

Here students demonstrate some of their newly-gained knowledge in an exam

Solar Site Analysis

A fundamental skill learned by appropriate technology students is the ability to evaluate a site for sun exposure.

Students learn to plot obstacles in the path of sun light and to determine the impact of those obstacles to sun access over the course of a year at any given latitude.

This knowledge can help students select the best sites for installing solar thermal technologies

Example of a completed solar access chart

Hot Water Heating

Solar hot water heating systems can provide 70% to 100% of the hot water needed for a residence

In the U.S.A. this can mean a savings of $200 to $300 per year

The simple payback in savings takes just a few years

The energy saved means much less pollution produced per household

Solar Hot Water Systems

Students learn how to plumb different solar hot water heating systems, particularly active-indirect systems.

Over the course of half a semester students learn about specialized plumbing parts and installation methods.

By the end of the section on solar hot water heating students are able to construct and install their own systems

Pictures of Students Building Solar Hot Water Systems

Students build complete systems on carts that can be rolled outside and tested in the sun

Installing a Hot Water System at House Near Boone

Students helped build and install a system for a couple living off the grid

Assembly and Installation

Half the system was pieced together at the ASU Appropriate Tech Lab

Assembly was completed at the Joyner House

Prevention of contamination by dirt, fecal matter, and moisture (which lead to mold & fungi growth)

Solar dryers double or triple drying speed Some dryers can shield food from sun, potentially

helping to preserve nutritional content An additional plus -no fossil fuel use

Some benefits of solar food dryers over simple open-air drying include:

Interestingly, solar food dryers have been poorly studied, although many designs have been published

Solar Food Dryers & Their Importance

Dryer being refurbished

Dryers have been tested outside (with sun) & indoors (using halogen lights).

ASU studies have evaluated: • reflectors, different glazing

materials, absorber plate materials, venting strategies and more…

Dryer Studies at ASU (Published in Home Power Magazine 1997 & 1999)

Food Processing for Drying

Apples, tomatoes etc… Sliced by hand Weighed to the nearest gram.

Weight also taken at the end of the day to determine dryer performance via moisture removal

Food-safe drying tray screen used

Direct Solar Food Dryers

Some dryers are simple to build but do let sunlight strike the food

Ryan is shown here constructing a small dryer with two drying trays

Vents on the front and back allow moist air from food to leave the dryer

Glazing for the dryer is one layer of Sun-Lite fiberglass

Example of Temperature Data Obtained in a Solar Thermal System

0

10

20

30

40

50

60

9AM5 Fri Apr 2002

12PM 3PM

Modified Dryer Experiments

De

g C

Insulated Lathe Non-Insulated Lathe

Ambient Insulated Alum. Screen

Temperature probes used for testing solar thermal technologies

Solar Ovens This important solar

technology can capture heat and build up temperatures between 200°F and 500°F –easily high enough to cook food.

With solar ovens there is no need to build a fire and burn wood on sunny days.

Also, water can be pasteurized or boiled to kill off harmful microorganisms

Oven thermometer

More Solar Ovens Built by StudentsAs can be seen here, ovens are tight well-insulated glazed boxes that have reflectors

Combination Food Dryer/Ovens-Experiments by StudentsSeveral students have tried to build units that can

cook or dry food. Both systems open vents when food drying is desired to prevent excessive heat buildup. It may be best to build systems designed for just one task.

Air/space Heaters

Space heaters can be placed in south-facing sash windows to capture heat for a room in a house

This simple technology can lower fuel use and heating bills

Here Terisangela & Stuart finish up a small air heater to be used in the apartment she is renting

Another air heater under construction

Water Distillers

Less than ½ of 1% of the worlds water is free of salt and available for drinking water. Much of that water is contaminated.

Water distillation purifies water by eliminating bacteria, pesticides, heavy metals, and dirt.

In the solar thermal technologies class students learn how to construct water distillers

Field Trip -Visiting a House With Solar Features

At times students take field trips to homes with interesting solar thermal technologies

Sun Space –Greenhouse– Used primarily as a heat

source for the house Carolina Water Stove

– Solar Panels on the roof generate hot water to heat the house

Talking with the owners, Sally & Gary after seeing the house.

The End (some comments)

Students comments about this course are very favorable

The reading and project requirements are challenging and educational

The course is fundamental for anyone interested in appropriate technology