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Passive Solar Greenhouses – another concept from MySolarPower

It seems possibly ironic to be talking about environmental issues, reducing our carbon footprint and the reduction of greenhouse gases in the same paragraph as praising the concept of a solar greenhouse, but this is what we intend.

In this section we will briefly discuss passive solar greenhouses rather than full-blown solar greenhouses which will apply far more to the serious commercial growers – where we create the option to move power and hot water from one zone to another.

Clearly the conceptual point of a greenhouse is that for those of us blessed with living in a cooler climate, a greenhouse provides a method by which we can not only extend the growing season but also grow a wider range of crops that would not otherwise survive in our temperatures. In order to achieve this it is often a requirement that a form of heating is required to keep the greenhouse free of frost (which may kill the plants) and have a controlled warmer night-time internal climate.

DIY Solar heat sink

In the BBC2 series “its not easy being green” a greenhouse heating system was put together by Dick Strawbridge, and this comprised of a 10 Watt Solar Panel, a 12V battery, a normal car battery is fine for this, although a deep cycle battery (sealed unit) is best where battery acid spills are unacceptable, a fan, a PVC waste pipe and, (believe it or not), 1 mtr cubed of crushed glass.

As with all greenhouses, the biggest problem is that they cool quickly at night but can easily overheat during the day, so the point of the solar heat sink was to stop the greenhouse from overheating during the day and from cooling too much at night.

Making the greenhouse solar heat sink system

Within the greenhouse you need a hole approximately 1 mtr cubed – insulate it with something like polystyrene and foil and then fill – in Dicks case he used glass, but you could use pea gravel, fire bricks etc.

The connected solar panel charges the battery which dives the fan24 hours a day – the fan will draw air from the greenhouse apex (the hottest point) and via the waste pipe, pump it through the heat sink. As the air rises through the heat sink, it cools itself by leaving its warmth within the heat sink and the cooler air is released into the greenhouse. The inverse occurs at night as cool air is passed through a now warmer heat sink etc.

Simple and VERY effective, this is designed to last for YEARS.

Greenhouse solar lighting

For those who wish to add solar lighting to the requirement it is often simply a matter of moving up a gear – say 18W with the solar panel – which should collect enough energy during the course of the day to power its bulb for around 9-10 hours daily. (7 hours in the winter – 10 hours for the remainder for the year).

Once installed this equipment, by adding a 150W inverter, can accommodate the charging of power tools or to run radios or lamps etc.

Complete passive Solar Greenhouse

Not only are they inexpensive and easy to install (see the video above), but the return on investment can be almost immediate.

Create you own micro-climate – perfect for your gardening ambitions.

Every greenhouse absorbs solar energy, but your passive solar greenhouse can also store collected solar energy as heat for use overnight or when it is overcast, and may also hold enough light to allow you to enjoy it, when you choose to.

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