Greenhouse

http://www.themodernhomestead.us/article/Greenhouse+Basics.html

Versions

1.0

The goal here is simple. Gain experience, get something functional. Very straight construction. 5.5' tall walls, 30° slope roof that reach a height of about 8' in the center.

Layout

It will be 7ftx15ft. Internally, there will be a vertical garden wall on the north side, 3 ft of open walk space in the center with hanging pots and 2ft of raised gardens on the south side.

Construction

Pole construction, treated lumber in concrete anchors. It takes 5 8' 2x4s to construct one section of the frame. At $5.25 per, that's $26.25 each. If these are spaced 3' apart, I need 6 of them for $157, plus there will be 7 supports that run the length, for an additional 21ft of 2x5 for another $70. The sides and roof have a perimeter length of 21', by the 15' that's 315sqft. At $0.11 per sqft of covering, it's $35, but I'll double glaze for $70. So far, that's $300. Call it $400 for the nails and concrete.

I will do two rows of cinder blocks at the base to add some rigidity and anchor the covering.

Design and Equipment

A core arduino or rasPi will log data. If a network connection if feasible I'll use that otherwise, I'll just log it.

Garden Wall

This is the first thing to go in. A vertical garden wall on the south side of the building.

Grow Bed

This is the second piece. Hydroponic grow beds on the north side. Flood and drain with bell siphons.

Temperature

Incorporate vents along the top of the roof. After it's up and running, add an air inlet from an underground pipe. When the temperature is too high, automaticlly open the vents and turn on a fan to pump air through the pipe.

A later development will be to add a solar thermal panel. This will be connected (via heat exchange) with the hydroponics system. When it is able to keep the hydroponics system at a reasonable temperature year round, I can upgrade to aquaponics.

I'll want one main temperature sensor, one external and one in the air pipe.

Water

Rain water will be collected and filtered. When the primary cache is too high, just overflow outside. When the hydroponics system gets too low, bring in additional water.

The hydroponics system will be a simple timer loop to flood the beds and the wall for 15 minutes every 30 minutes. I'll also need a way to sense the amount of nutrients in the water and add additional when it's too low.

Solar

I'll get the solar system setup and that can power the pumps.

Cost

I have not yet estimated the cost for the vertical wall, tools to aid with temperature regulation, setting up hydroponics, but let's call all that $1000.

At $1500, it needs to offset $75/year to be worth the investment.

I can iterate on this by extending it lengthwise.

Data Collection

• What does the temperature look like year round - important for upgrading to aquaponics.

2.0

This will be 14' wide (2g,3w,4g,3w,2g) by 30' long.

If the foundation approach on v1 works, I'll continue with that. If not, I will pour a foundation around the perimeter. Probably 3' deep and rising ~6" above ground. Embed a bolt about every foot and the whole thing will be bolted to this. If I'm doing this, it may also be worthwhile to add insulation.

I also want to see how the film walls hold up. I may switch over to some sort of polycarbonate here.

3.0

This should be the final revision at 21' (2g,3w,4g,3w,4g,3w,2g) x 60'.

I've always liked the idea of using part of this as living space. Specifically, doing aquaponics using a small pond to grow the tilapia with a small patio near it.

Materials

Covering can be polyethylene that needs to be replaced every few years or polycarbonate. Polyethelene is available for around $0.11/sqft, where polycarbonate is going to be around $1.70/sqft. Polycarbonate also provides better insulation.

Tuftex panels look really good.

Automation

Based on http://www.youtube.com/watch?v=KZiqUZGjGc0

The core will be an Arduino (or two) with either a wifi shield or connected to a RasPi (or something completely different - I'm not sure what will be available).

Water

The garden will be broken up into grids. Each grid will be a physical PVC grid (or manifold) with small holes to act as a direct soil sprinkler (cheaper version of drip irrigation). The size of the grid will be how large it can be while maintaining pressure. Each grid will be controlled by a solenoid. Each will have a soil-moisture detector (easy to make). When the soil moisture gets too low, it will send the central control a request. The central control will only activate one grid at a time (pressure).

Temperature

The pond should help stabilize the temperature passively. There will be a fan if it gets too hot. It would be nice to have some way to chance the thermal conductance of the pond (I'm thinking giant heat sink). I may also include heat-lamps or propane, but that would be for emergency frosts.