Engineering Greenhouses

Students use their scientific knowledge about Earth’s climate and the greenhouse effect to figure out how to engineer greenhouses, using various methods to achieve the desired internal temperature range.

• Engineers are often seen as the link between scientific discoveries and how they are used in the real world. Engineers have already designed technologies to address climate-related issues.
• There are many questions that remain unanswered about how Earth is changing and what the impacts of warmer temperatures will be. Global warming leads to other changes, such as stronger hurricanes, melting glaciers, and the loss of wildlife habitats. These changes are called climate change, and they happen because Earth's air, water, and land are all related to one another and to the climate. A change in one place can lead to other changes in other places. Engineers can design solutions that solve some of these problems.
• People who live in cold climates already use technologies that apply scientific knowledge to grow plants year- round, even when temperatures get too cold outside.
• Greenhouses are designed to trap thermal energy from the sun to keep the inside at a set temperature because they house different kinds of plants, which need a specific temperature range to survive.

• Why has climate change been considered one of engineering’s grand challenges?
• What is one example of an effect of climate change and how an engineering solution might address this effect?
• Why are greenhouses different from other buildings?
• What scientific knowledge do engineers need to know to build an effective greenhouse?
• Why are greenhouses made of glass, plastic, or other transparent material?
• What kind of heat transfer does a greenhouse use to warm itself?
• How does the greenhouse stay warmer than the outside air?
• How would the temperature of a greenhouse be affected if a window or door were opened?
• What are some of the questions that engineers must think about before designing a greenhouse?
• What are some possible constraints, or limitations, that engineers might face when designing a greenhouse?

Misconception: Global warming and the greenhouse effect are the same.

Fact: The greenhouse effect is essential for life on Earth because it keeps the planet at a habitable temperature. Most scientists believe that the current global warming is caused by a dramatic increase in the number of greenhouse gasses in the atmosphere, which upsets the natural balance of the carbon cycle.

Carbon cycle : the circulation and transformation of carbon back and forth between living things and the environment

Climate change : a significant change in the average weather in a location over 30 years or more, including changes in temperature, precipitation, or wind patterns

Greenhouse gas : molecules in the atmosphere that absorb thermal energy from the sun and warm Earth’s surface and atmosphere; include carbon dioxide, water vapor, and methane

Studying Climate Change

There are many questions that remain unanswered about how Earth is changing and what the impacts of warmer temperatures will be. Global warming leads to other changes, such as stronger hurricanes, melting glaciers, and the loss of wildlife habitats.

These changes are called climate change, and they happen because Earth's air, water, and land are all related to one another and to the climate. A change in one place can lead to changes in other places. For example, as Earth gets warmer, more water evaporates from the surface, becoming water vapor, a greenhouse gas. More water vapor in the atmosphere leads to even more warming, which will lead to more evaporation, which will lead to more warming.

Scientists are still trying to understand how this feedback loop impacts global warming. Many scientists around the world are studying different aspects of climate change to try to better understand how all of Earth’s systems work together. One example of this is the researchers focusing on how warmer temperatures affect the latitude in which plants such as sugar maples are found. This is because many climate scientists are worried that climate change will significantly alter weather systems around the planet. This could make life more difficult for living things, which will have to adapt to the rapid changes or risk becoming extinct.

Designing a Greenhouse

Engineers have already designed technologies that apply scientific knowledge about heat transfer and Earth’s climate. For example, step inside a greenhouse, and one of the first things you’re likely to notice is that the temperature inside is much warmer than the temperature outside. Even on wintery days, greenhouses are usually filled with a variety of plants, including different kinds of flowers and vegetables. Behind the scenes, engineers have worked to make sure that the temperature can be maintained. If the weather outside changes dramatically, plant growers operating the greenhouse can monitor and change the amount of heat, light, and water their plants are getting.

The design of a greenhouse plays an important role in how well it is able to regulate the temperatures inside. Radiant heat from the sun enters the greenhouse through its transparent covering of glass or plastic and starts to warm the objects, soil, and plants inside. The heated surface warms the air above it. As the air heats up, it begins to rise, and through convection, cooler air fills its space. That cooler air becomes heated as well. Because the greenhouse is tightly sealed, all of the air inside remains relatively warm. If even a small window is opened, the temperature will drop. Greenhouses can also become humid because of plant transpiration, which releases water vapor into the atmosphere.

Some greenhouse owners experiment with inexpensive ways to increase heat, such as painting containers black to absorb heat and filling them with water to keep the heat. Most engineers also use location, positioning the greenhouse where it will get the most direct sunlight.

When an engineer designs a greenhouse, they research the specific needs of that particular greenhouse. For example, what kinds of plants will be grown, and what is their ideal temperature range? How many plants will be grown, and how much space do they need to grow? What is the climate of the location like, and how much sun does that location usually get? How much do the various materials cost?

In this engineering lesson, students design and build a greenhouse prototype to maximize the amount of thermal energy transferred to the structure from a heat source. Students analyze temperature data they collect during the prototype tests and calculate the total cost of materials used for each prototype. They use the data to evaluate the effectiveness of their greenhouse prototypes in meeting the minimum internal temperature requirements at a low cost.