The geodesic dome greenhouse was originally designed for regions like Colorado in the US, with cold winters and warm summers. It allows farmers to grow and consume fresh organic food all year long, providing alimentary independence and self-sufficiency. It is produced by the company [...]]]>  

 1.1 The Growing Dome: History and Overview of Purpose

The geodesic dome greenhouse was originally designed for regions like Colorado in the US, with cold winters and warm summers. It allows farmers to grow and consume fresh organic food all year long, providing alimentary independence and self-sufficiency. It is produced by the company Growing Space (http://www.geodesic-greenhouse-kits.com/). This report describes the installation of the first greenhouse of its kind in Nova Scotia, Canada. The project was supported by the Nova Scotia department of agriculture under the Energy Pilot program. 

 1.2 Construction of the Greenhouse

The dome was built by a crew of five people in about two weeks, including the preparation of the ground and the concrete foundation, the assembly of the dome, and the filling of the beds. The local crew was prepared by watching an educational video provided by Growing Spaces Inc.. All the material was pre-cut, pre-drilled, and colour-coded.

1.3 Features of the Greenhouse

The greenhouse features following characteristics:

Illustration 1: Features of the dome in evidence

• Solar Panel: a small solar panel powers the under-soil heating system.
• Under-Soil Heating System: composed of pipes that transport air from the southern (warmer) part to the northern part of the dome. The air circulation contributes to keep the temperature constant.
• Foundation Walls Insulation: this gives a value of R 3.5 of insulation.
• Northern Wall Insulation: the northern wall of the greenhouse is insulated with reflecting panels. These have a double purpose: they insulate, and they reflect the sun back to the inside.
• Automatic Vents: the vents open automatically at a certain temperature. Normally they are placed on the top of the dome, however, we decided to place them laterally, because the temperature in Nova Scotia is never too hot, but there is plenty of wind. This placement protect the vents from strong winds and allows for better air circulation. 
• Water Tank: the water tanks offers a thermal mass that maintains the temperature stable.
• Polycarbonate Multilayer Panels: the panels that cover the dome are made of a special material that lets the sunlight enter but insulates the surface. The panels have an R factor of 3.5

1.4 Shape

The most evident characteristic of the greenhouse is its shape. It is built to enclose the most optimal volume per surface area ratio, which captures more solar radiation than any other greenhouse. This special shape also gives a sense of well being, which makes working inside more enjoyable.

The shape of the greenhouse offers three natural layers of planting space:

Illustration 2: the 3 layers of the dome

• beds: this is where the most vegetables are planted.

• center: the center of our dome is destined to host fruit trees that cannot grow outside naturally. We are considering to plant an olive tree, and then producing the first local Nova Scotian olive oil.
• walls: the vertical dimension can be used for hanging plants.

1.5 Energy Efficiency

Our greenhouse works without the use of electricity. The water tanks inside are used for the daily watering of the plants. On sunny days we fill the tanks with a pump that is powered by solar panels and wind generators. During harsh winters, heaters can be used to raise the temperature in the dome. We are considering buying a small propane heater for those circumstances.

The temperature results depend on the amount of sun outside. On a sunny winter day, with temperatures below 0 degrees Celsius outside, the climate of the greenhouse is usually 20 degrees or above. During the night, the temperature difference is still up to 15 degrees.

At the end of March, on a sunny day, with an outside temperature of 8 degrees Celsius, the temperature temperature was 30 degrees Celsius. If there are more than three cloudy days in a row, the temperatures inside the greenhouse will drop.

Illustration 3: the dome structure retain the heat of the sun

Also during the summer multiple advantages exist.

While most greenhouses are too hot during the summer the Dome has a solar system for air circulation, additionally the side windows open automatically when the temperature is over a certain degree.

During the summer 2012 we saw the difference of performance between the same vegetable growing inside and outside of the greenhouse. For example tomatoes inside were immune from the variation of temperatures, wild life and life stocks damage.

1.6 Resistance

Worldwide climate change is going impact Nova Scotia in several ways, one of the major ones being the amount of storms, especially hurricanes, increasing every year. The geodesic shape is one of the most resistant architectural structures in existence. Its “omni-triangulated” surface provides an extremely stable and strong structure. During the winter of 2012-2013 the greenhouse resisted winds of up to 120 km/h without taking any damage. The triangular side panels are made of polycarbonate multi-layered multichannel material, that resist to flying debris. The shape of the dome supports heavy snow, so there is no danger of a roof collapse. Growing Domes are expected to last for 15, or even 30 years, if maintained well. Traditional greenhouses with plastic cover do not perform nearly as well. The price for these common greenhouses is often underestimated, as the cost of maintenance is very high.

Illustration 4: the dome during the late summer 2012.

We usually use the eleven feet water tank for watering the plants. An external water pipe provides fresh water. In the water tank we planted a special kind of plant called “Sparrow Feather” that keeps the water oxygenated. Our four goldfish eat algae, larvae, and mosquitos, keeping the water clean.

1.7 experience and Production

According to the producer, a 33 feet dome should feed 8-10 people. We cannot confirm this until now, because of our late start in the 2012 season. In the year 2012/2013, we experienced a regular growth of vegetables until late December. The Winter 2012/2013 was especially rough in South West Nova Scotia with low temperatures, winter storms, and little sun, but the dome performed well. During two weeks between Christmas and mid-January, there was very little sun. In that period, some of the vegetables (eg. lettuce, spinach, brussel sprouts, Swiss chard, carrots, onions) went dormant, and the peppers, tomatoes and eggplants died. In the worse days, with a outside temperature of -15 and a wind chill of -25, the water tank developed some superficial ice.

Illustration 5: swiss chard full growth at the begin of march.

The dormant vegetables started growing again in the third week of January and were ready to harvest at the end of February. Carrots and onions started to develop around mid-March.

Illustration 6: greenhouse during the winter 2013

In the same period we began to sow the first seedlings (tomatoes, peppers, eggplant, cucumbers, herbs, broccoli, ect.). The production is completely organic, no chemical is used. Local seaweed, straw, and horse manure were used for fertilizing. During this first year the best performing vegetables were cucumber and tomatoes. We learned not to place certain plants together, such as peppers, eggplants, and tomatoes. In future we will aim to not only extend the season of certain vegetables, but to also plant vegetables that do not grow at all in Nova Scotia. At the time of this writing, the ideal vegetable has to be found. We seek in 2013 to achieve full production. A small propane heater would have helped.

Illustration 7: greenhouse in early Spring 2013

By selling the production the initial investment should be payed back in five years (depending on the market conditions). For the rest of its lifespan ( an estimated 15-30 years) the dome will produce a net return of investment.

1.8 Conclusions: Fresh Local Food

Most Canadians today are used to buying exotic vegetables coming from the USA or Mexico. Such a special greenhouse allows the growth of fruits and vegetables that are locally produced, reducing the transportation costs as well as the carbon foot print. We think that this fit very well in the general concept of the Eliopoli as eco-village and organic farm.

This is connected to a an Magnum MS-PAE Series inverter. The battery bank is composed by 16 Surette [...]]]> The System:

As maybe you remember , our hybrid system is composed by 3 wind turbines with 960 W + 6 panel with 200 W. Nominal value 4.2 KW.

This is connected to a an Magnum MS-PAE Series inverter. The battery bank is composed by 16 Surette S-600. With a capability of 44 Kw/H.

If the battery reports 24.4 V immediately after the start of the generator goes to 26.4. the Inverter display a “bulk charging” with 110 V. After 3 hours, when reach ~28 V, the inverter goes to “absorb charging”. It remain to absorb up to 28.5 . Then goes to “float charging” down to 26 Volts. If I read the voltage while the system is only charging with solar + wind it never surpass 26.8. At this point the controllers stop to charge the battery. At 24 V the controllers report that the battery bank is half full. Our original consume, reported by Nova Scotia power was between 20 and 30 KW/H per day. We reduced it to the 11 KW/H per day

 so in theory we should have 3 days of reserve without sun or wind.

The problem:

This is the problem: We have a big deal of humidity and we need to circulate the air all day long. The circulation system should consume 200W (see http://www.venmar.ca/DATA/DOCUMENT/187_3_en~v~Specification_Sheet.pdf) but really takes 1100 W (10 amps).

The dehumidifier Danby ddr 2611 is labeled with 1400 W but takes 18 amps (1980 W).

Adding the dehumidifier and the air circulation system to the equation , we need 33 Kw/H per day. I’m not sure that the system is set properly, It was installed by an electrician without experience on this field. The actual performance of the system seems to be way below the expected ones. Especially the 3 wind turbines don’t seems to produce much electricity with summer winds.

One part of the issue is that the roof, where they are installed, is separated by a ridge so that the 3 turbines perform together only with winds from north por south.

In a good day with wind and sun we come up to 26 Volts of charge. But strangely the next day we are with a very low charge also we have used no electricity at all.

Still is enough to run our home without a dehumidifier or air circulation system. What do you suggest?
would make sense to expand the solar panel array?

Eastlink TV will feature a show segment about Eliopoli late September.