Renewable Energy Greenhouse at The Secret Garden at 6 Chelsea Terrace

A Very Brief Overview

Before we get into it I would like to acknowledge Kannan Thiruvengadam, Director of Eastie Farm, Gabe Cira, architect, and Jena Tegeler, landscape architect, for their continuous, almost daily, work with me on this project for the last year. Each of them has had their hand in every aspect of the project so don’t let the titles I provided fool you. I would also like to thank Sue Butler for her many hours of consultation and continued support wherever needed on this.

Even before our acquisition of 6 Chelsea Terrace from the Department of Neighborhood Development in early 2021, we have been working toward creating a more community oriented and environmentally resilient site. The property is being wholly redeveloped, with an aim at creating spaces that allow us to continue to grow food, educate, and increase food access. Now we strive for this on all of our sites, but by creating a geothermal greenhouse here, we can plan for year round operations.

There are times that we can feel hemmed in by the seasons. Since most of what we do is outdoors, we can only safely and comfortably operate at full capacity during the growing season April through September, with the shoulder seasons serving as planning time and providing sporadic work. With indoor space, partnerships like the one we have with Boston Public Schools, can flourish now that we’re operational during the school year. We anticipate continuing our growing, our workshops, our partnerships, our CSA and anything else we can find the time and space to accomplish with this fantastic new resource.

Let’s take a look at how we got here.

When we first wrote the grant that outlined our idea for a greenhouse, we agreed that we wanted to use renewable energy. We felt that given the opportunity to create something totally from scratch with an untouched lot meant we could dream big. Convention suggests a greenhouse gets outfitted with a propane heater for the winter and a system of fans for the summer. If we could, we wanted to keep our contribution as clean and green as possible. This meant an alternative to fossil fuels. We identified three options: solar, wind, and geothermal. Given space constraints we ruled out the first two. The site, unfortunately, doesn’t receive an overabundance of sunlight and any additional obstructions, in this case solar panels, means less light reaching the plants. It’s also impractical and probably illegal to install a large wind turbine on site. Choosing geothermal made the most sense for our site.

Geothermal

Now some of you may be wondering what geothermal is. Below the frost line, about five feet down, the earth maintains a constant temperature in the mid fifties (the same temperature before plants go dormant or die). Geothermal, or ground source pumps, draws from the warmth of the earth and processes it to either warm or cool air depending on the season. In our case, we have three separate 455 foot geothermal wells that lie in an L shape on the site. They are spaced fifteen feet apart so as to not compete for the same resource with one another. Within in each well is a closed loop of piping containing glycol, a water and antifreeze solution. In winter, the well draws heat up and into the heat exchanger that then blows warm air into the space. In summer, the well draws heat down into the earth, thereby cooling the greenhouse.

The heat exchangers do, however, require electricity to run. Some of you may think, well generating electricity still requires burning fossil fuels, and you’re not wrong. Most electricity is generated by burning fossil fuels, with some provided by solar, wind, or other renewable sources. However, we don’t feel that because the solution is imperfect at the moment, that it isn’t worth investing in. For example, since we began this project, the City of Boston has created a Community Choice Energy program that allows consumers to opt into a 100% green electricity source, which we are opting into. Running on electricity also allows us to create a direct link to solar panels if space opens up, maybe on neighborhood homes, large buildings developed in the area, or on the top of a carport. Investing in geothermal affords us the option to become even greener, whereas settling for propane heaters precludes any changes.

Read more about the geothermal drilling process here (link incoming)

The Greenhouse

Moving from below ground up, we now have the greenhouse itself. When considering our options in manufacturers we factored in a few things: durability, cost, and performance, with special consideration to energy consumption. We decided on a manufacturer in the Netherlands called Gakon. They have examples of their greenhouses in New England, with our team visiting a few, namely WeGrowMicroGreens in Hyde Park and Pemberton Farms in Cambridge.

The durability of the construction is shown in the above examples, with Gakon greenhouses lasting over 40 years. This is due to the quality of steel, glass, and polycarbonate used. Once fabricated, the steel is coated and ready to assemble. This means no need for after the fact drilling that exposes the raw steel, leaving it vulnerable to rust, thus degrading the building. They avoid this by prefabricated things down to the finest detail.

Costs of everything skyrocketed during the pandemic, and although the greenhouse was above the initial grant award, we were able to raise enough funds to keep the needle moving so that we could purchase and construct (we are still fundraising for other parts this project and your donations are tax deductible and much appreciated!). We thought it was better to invest in something long lasting if we could afford it now rather than sink the money into repairs for a less durable product.

Lastly, there’s how the greenhouse performs. This means allowing us to do all that we want to do in it: grow and distribute food, host groups, and educate. The education factor is a huge part of our decision. The Gakon system is an educational piece in itself. The design is environmentally savvy and forward thinking. The gutter system allows us to harvest rain water, by turning the gutters inward to feed a large cistern that in turn provides fresh water to our plants. This alleviates flood risk for the site and diverts rainwater from overburdened storm drains. Plus, plants prefer rainwater as it doesn’t have the high concentration of chlorine found in city water. Next, the system includes two energy curtains that open horizontally over the space to insulate against heat loss through the glass roof of the greenhouse. The two open automatically once the interior reaches a certain temperature. Both have a level of transmissivity so light can pass through during the daytime and still allow for plant growth. We can then allow for the Sun’s warmth to enter and ensure it stays for longer. They also double as summer shading when the time comes. The bit that is completely unique to Gakon is their operable roof. The peak of a bay opens automatically to let heat escape and cool the space. With summer heat expected to continue to climb, it’s passive solutions like this that intrigue climate organizations like ours. Although we can still use fans to circulate air, we don’t have to rely on them so heavily with this feature available to us.

Follow the greenhouse building process here (set to begin in March!)

The Landscape

The greenhouse will only be as resilient as the land around it. That’s why we’re focusing as much time and effort into the creation of an environmentally sound landscape not only according to today’s standards but for years to come. The site rests in what’s arguably the low point of its block and just a few feet below the surface there is a thick layer of Boston blue clay. What does this mean for us? It means that water will naturally run toward our site and with the only a few feet of permeable soil available to sink stormwater, that water will likely stay on our site and muddy the soil. This could be a great opportunity, however. Since plants like and need water, how can we turn this into an advantage? As discussed previously, the greenhouse will capture, harvest, and utilize a good portion of water falling on the site. What doesn’t fall on the building will sit atop this impermeable clay. There are a few ways to address this. We can remove and replace the soil with well draining sandy loams or add in sand, gravel, and loam until the existing soil in satisfactory in its ability to sink stormwater. That’s all below ground. There are also options for above ground problem solving. Adding in New England native trees, bushes, and water loving plants into specifically crafted rain gardens can help make that rainwater productive and not just sink it. The combination of the two means that we can utilize the water on our site as well as the neighboring sites that already drain onto ours.

We want this space to be an interactive community space that shares the “grow together” model of all our Eastie Farm sites. This means storage for communal tools. We wanted to continue our green infrastructure with our shed. This will boast a green roof, with mosses and room for potted plants.

Follow the landscape restoration here (link incoming).

Timeline

This will be created soon and updated regularly. The above blog is more of an informational overview of the project and why we’re excited about it, while the timeline will be more of a blow by blow look at what steps were necessary to get here and the on the ground reality of what it looks like for a small organization to take on such a large project.

Grantors

Below is a list of funders for the project so far:

• State of Massachusetts
  • Executive Office of Energy and Environmental Affairs
• City of Boston
  • Department of Neighborhood Development
  • Community Preservation
• East Boston Foundation