Going Nuts for Clean Energy: Solar-Heated Greenhouse and Biodiesel from Hazelnuts


by Norm Erickson, Hazelnut Valley Farm • November 2011
Bermed solar-heated greenhouse at Hazelnut Valley Farm

I retired in 2010 from IBM after working for the company for more than four decades, and my wife Mary retired in 2000 from teaching family and consumer science to middle school kids for 32 years. Neither of us came from a farming background, so this has been a wholly new adventure.

While on vacation in 2003, we read a life-changing book by Richard Heinberg titled The Party’s Over. It is a book about energy. After reading more books and hundreds of articles on the topic, we decided to purchase land and grow hazelnuts for energy production. It started with planting a thousand seedlings in 2004, building a road, and starting a machine shop. Over the next three years we built a root cellar and greenhouse—all still in some stage of completion.

We chose hazelnuts because the nutritious kernels contain over 60% high quality oil, suitable for biodiesel fuel and as a gourmet food ingredient. Soybeans are currently used for biodiesel production in Minnesota but contain only 20% oil. Soybeans are annual plants that have to start with seed germination every year, whereas hazelnuts are perennial and have minimum inputs once the bushes are established. We now have over 4,200 bushes in the ground and nut production is growing—from 10 pounds in 2006 to over a ton in 2011. Our market focus has shifted from biodiesel to the edible local kernel and oil markets because product values are currently much higher there.

The greenhouse is earth bermed and has 16’ x 60’ of glazing. The glazing is 7/8” low-e insulated glass. A 14’ x 28’ office and work area and bathroom and shower are at one end of the greenhouse structure.

Several renewable energy systems are part of the design. A low-temperature energy storage system is in the berming behind the greenhouse. Recognizing the relatively high gain and loss off energy in a greenhouse, and the low specific heat and conductivity of soil, we filled 320 55-gallon polyethylene drums with water, and sealed and buried them in the storage area to increase the energy storage capacity and to speed energy flows to and from the ventilation system.

The heat exchange and distribution system uses about 2,800 feet of 4” PVC drainage pipe. Fifteen-inch double-walled PVC culverts function as manifolds and conduit from the greenhouse to storage. Seasonally, hot (or cold) air is drawn from the greenhouse and blown out into the storage system. It passes through an array of parallel pipes above the barrels of water, then makes the return trip below the barrels and re-enters the greenhouse via the lower manifold. The manifold below the floor has twelve lines that carry the warmed (or cooled) air to risers through the floor at six-foot intervals below the glazing.

During the spring, summer, and fall warm seasons, energy is carried from the greenhouse into storage to heat the soil behind, under, and around the greenhouse, cooling the greenhouse in the process. During cold weather, the system will blow cold air into storage to be warmed before it returns. The temperature will be permitted to drop to near freezing at night to conserve energy, and raised during the day in cold weather. On very sunny winter days energy will be blown into storage for freeze protection during cold nighttime hours.

A solar thermal panel collects energy to heat potable water, with electric backup for cloudy periods. An array of solar thermal panels east of the greenhouse heats a storage system that can be tapped for heating a food dehydrator 24/7 and to warm the floor in the work area.

The greenhouse also has a fan coil through which well water can be run seasonally to cool and dehumidify the growing and working areas that also provides backup winter freeze protection. An air-to-air heat exchanger provides several functions. It can exhaust moist air from a dehydrator and bring in preheated and drier air from outside, and in the winter it can exhaust moist, CO2-depleted air and replace it with preheated, dry, CO2-rich air from outside the greenhouse.

Processing our highly variable hybrid hazelnuts has been challenging because equipment designed for them was unavailable in the market, a situation which personified the “need is the mother of invention” platitude. For this reason, I have been developing machines scaled for local processing of this new crop. Some are simple and inexpensive to build on site, and some are relatively expensive because they require precision modeling, machine shop work, and testing and reengineering to arrive at useful versions. The machines include a husker, aspirator and cleaner, sorter and sizer, and nut cracker. Work continues in our efforts to develop a better husker, meet commercial food-grade processing requirements, and reduce labor inputs. Goals to get licensed as a wholesale hazelnut processing facility and to be able to provide the service to other growers should be met by 2012.

For more information about Norm and Mary Erickson’s Hazelnut Valley Farm in Lake City, Minnesota, please connect with Norm at hazelnutsource@gmail.com.

Learn about a similar renewable-energy-powered greenhouse project in Southeast Minnesota at Badgersett Farm >>

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