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Passive Solar Greenhouse Design

The Challenge: Energy Costs of Greenhouses

Most greenhouses are require immense amounts of fossil fuel heating and cooling to grow year-round in most climates. This is because traditionally, greenhouses are made entirely out of glass or plastic (called glazing). Glazing materials let light in, but they also easily let heat out, making a greenhouse an incredibly in-efficient structure. Imagine if your house were made of all windows…your heating bills would skyrocket.

A New Way to Grow

At Ceres, we take a different approach to greenhouse design. Our energy efficient greenhouses combine passive solar greenhouse design with innovative strategies for storing thermal energy (heat) during the day. This allows the greenhouse to re-use vital heat collected during the day for heating at night (instead of venting it outside like most greenhouses). The result is an abundant, year-round growing environment independent on fossil-fuels, and produces nutrient-dense food and crops year-round.

[minti_testimonial author=”Steve Newman” company=”Colorado State University” img=”323″]“Many farmers are interested in greenhouses. What scares them most are the heating bills.”[/minti_testimonial]

Passive Solar Greenhouse Design Principles

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Passive Solar Greenhouse Design Principles

Passive solar greenhouse design is the practice of taking advantage of free (passive) solar energy as the main energy source, avoiding costly energy bills for year-round growing. Passive solar greenhouses can still use electricity for certain components (just as a passive solar home may still have a refrigerator or other electric appliances). Several design elements come together to create a super energy-efficient structure overall, allowing for abundant year-round growth.

For more information on energy-efficient year-round greenhouses, see The Year-Round Solar Greenhouse

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Elements of a passive solar greenhouse:

  • Orient the greenhouse towards the Sun: In the Northern hemisphere, the majority of the glazing should face South to maximize exposure to light and solar energy.
  • Insulate areas that don’t collect a lot of light: In the Northern hemisphere, the North wall of the greenhouse plays a small role in light collection. It should be insulated in order to reduce heat loss, creating a more thermally stable structure.
  • Maximize light and heat in the winter: To grow year-round without dependence on lights or heaters, it is crucial to maximize light and heat during the colder months. This is done by using proper glazing materials and angling the glazing for winter light collection…in general, using the glazing area strategically.
  • Ensure sufficient ventilation: Natural ventilation ensures a healthy plant environment and controls overheating.
  • Insulate underground: Insulating around the perimeter of the greenhouse allows the soil underneath it to stay warmer, creating a “thermal bubble” underneath the structure that helps stabilize temperature swings.
  • Reduce light and heat in the summer: Growing during the warmer months can mean challenges with overheating. Strategic shading, glazing placement and angles reduce unnecessary light and heat in the summer.
  • Use Thermal Mass (or other thermal storage techniques): Thermal mass materials are materials that store the excess heat in the greenhouse during the day, and slowly radiate it at night or when needed. This evens out temperature swings, creating a more controlled environment for growing. Almost all solar greenhouses have some mechanism to store heat, broadly called thermal storage.

Frequently Asked Questions: Passive Solar Greenhouses

In a broad sense, a passive solar greenhouse is simply one that uses passive solar design principles, and they can be electric or non-electric structures. (Just like a passive solar home is very energy-efficient, but probably still has electric appliances like a refrigerator.) In a more narrow sense, many growers use the term passive solar greenhouse to describe a greenhouse that does not have any electricity.

Our greenhouses utilize passive solar design, called ‘solar greenhouses’ for short. Passive solar greenhouses are designed to maximize heating from the sun, to create an efficient self-sustaining year-round growing environment. While they can be powered by a solar PV (solar panels), Standard models do not include solar panels (photovoltaic systems). We can help you integrate solar panels into your design to make the greenhouse completely self-powered, net-zero energy or off-grid. Please see our blog, “Integrating Solar Panels with the greenhouse” for our tips on doing this.

There are two options for an off-grid greenhouse:

  • Design a passive solar greenhouse. This is a structure that does not use electricity, and is inherently off-grid. Instead of electrical fans, a passive solar greenhouse uses passive vents and thermal storage methods. We work with people on designing passive solar greenhouses, but most of our clients add electricity to the greenhouse for greater climate control. Much more information on passive solar greenhouse design is in our book, The Year-Round Solar Greenhouse, and you can get in touch with us if this your preferred design.
  • Add solar panels to the greenhouse. The feasibility of powering the greenhouse with solar photovoltaic (solar PV) panels greatly depends on how you will be growing. With a large electric demand, solar panel systems can get quite expensive. Smaller, cost-effective DIY systems are also possible. We recommend contacting us about your project, and reading more about getting started with integrating solar panels in our blog, 5 Tips for Designing a Solar-powered Greenhouse.

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