Novel approaches to improve energy efficiency in northern New England greenhouses
Unfavorable weather is a bane to farmers leading to financial instability. Growers are turning to greenhouse production to reduce loss due to poor weather and increase the length of the growing season. Though plastic hoop houses are inexpensive to erect, they demand large amounts of energy, especially in northern climates. This project builds on our greenhouse network in Maine, New Hampshire and Vermont, partnering with growers to increase their sustainability through improved energy conservation in hoop houses. Two innovative energy-saving devices–a bubble insulation system and an energy curtain–are being retrofitted into greenhouses at the largest greenhouse ornamentals operation in Vermont. In less than two months the grower has observed a two-fold savings in gas consumption in the house with the curtain compared to the standard control house. Work is underway to get the experimental bubble insulation system into operation. That system is expected to provide even greater savings than the curtain. Monitoring equipment is being installed to quantify the energy savings over time relative to ambient temperature. A grower survey was recently sent out to obtain baseline data on energy use in the tri-state region, and workshops to update growers on our progress are planned for January, 2011. A questionnaire was developed to select growers who will receive energy audits later in the year.
1. Assess two innovative energy-saving devices retrofitted into a greenhouse: a bubble insulation system and an energy/shade screen system.
2. Conduct comprehensive energy audits before and after retrofitting the greenhouses to quantify the benefits of both devices.
3. Determine cost of greenhouse retrofitting, energy savings and potential tax incentives from which to assess the costs and benefits of both systems compared to an unimproved greenhouse.
4. Conduct a survey to generate baseline data on current energy consumption and conservation used by greenhouse growers in the tri-state region.
5. Conduct energy audits at 9 greenhouse operations to provide quantitative information about trends in current energy consumption and identify the most significant measures that would improve conservation.
6. Conduct workshops in each state to present information on energy conservation and federal and state incentive opportunities, and host an open house to demonstrate the innovative energy conservation systems tested.
7. Produce a grower-friendly guide entitled “How to Retrofit a Greenhouse for Energy Conservation” Cost of retrofitting, energy savings and potential tax incentives will be determined from the data, from which an accurate assessment of the benefits of these systems will be made.
8. Develop a web-based program enabling growers to calculate cost savings from energy conservation activities.
Obj. 1. Options for installing an energy curtain were investigated, and a company specializing in retrofitting curtains for plastic hoop houses was identified. The energy curtain was installed, though the cost was approximately twice what we had budgeted. This additional cost was a result of the complex design required for retrofitting. It would have been much less expensive to install a similar system at the time the greenhouse was erected.
Installing the bubble insulation system has proven to be far more complicated and expensive than anticipated. This system is experimental and not available to purchase “off-the-shelf”. We were able to purchase a used system from a grower in Canada, which has been retrofitted for our experimental greenhouse. Work on the bubble system continues, and it will hopefully be in full operation by January 1, 2011.
Obj. 2. Collection of assorted energy consumption and weather data is being done by EnSave, a nationally-known company located in Vermont. They have developed a plan for data collection and have purchased and installed the equipment in the three experimental greenhouses. Data collection, on a trial basis has begun and it is anticipated to be fully operational by January 10, 2011 when the grower will once again fill the greenhouses with plants for the Easter season.
Obj. 3. Information on the cost of retrofitting the greenhouses has been collected (to date) and will be compiled when the bubble system and the thermal curtain are in full operation, These data will be used to determine the expenses associated with actual retrofitting the structures for energy conservation.
Obj. 4. A 2-page survey dealing with energy usage and conservation measures was developed and reviewed by the project cooperators. The survey was sent out to greenhouse growers in Northern New England in November along with our annual greenhouse workshop announcements. It was sent to over 2000 growers in the tri-state region on our mailing list. It has also been uploaded to our Entomology Research Laboratory website (http:/www.uvm.edu/~entlab/). Additional copies of the survey will be handed out to growers at our January workshops to encourage participation.
Obj. 5. A short questionnaire was prepared by Ensave and revised by the cooperators to select the growers who will receive energy audits. We felt it was important to identify growers in the 3 states who had sufficient greenhouse space and who would benefit most from such an audit. Several growers will be identified to receive the questionnaire, from which 3 from each state will be selected.
Obj. 6. Workshops are scheduled to take place in the ME, NH and VT on January 10-12, 2011. At each session current information about this energy conservation project and progress we have made with retrofitting the greenhouses will be presented to attending growers. Adequate time will be available for questions and slides of the conservation systems will be used.
Obj. 7. The guide is scheduled for production in year 3 of the project after compiling data from the first 2 years of work.
Obj. 8. The web-based program is scheduled for development in year 3 of the project based on data we collect in the first 2 years.
This project has been in progress for less than 6 months, and thus none of the grower-linked milestones have been met. However, in less than 2 months the commercial grower who owns the greenhouses where we are conducting the research has observed a two-fold savings in gas consumption in the house with the curtain compared to the standard control house. Of note is that completion of the retrofitting of the bubble insulation system will not be completed until 10 January 2011.
Impacts and Contributions/Outcomes
Despite the additional cost and various problems associated with retrofitting the existing greenhouses, the grower has already noticed a 2-fold reduction in gas consumption compared with the greenhouse without a curtain. Both of these greenhouses were filled with poinsettias destined for sale during the Christmas holiday. As a result of the apparent cost-savings, the grower is planning to install a thermal curtain in another greenhouse (at his own expense). In addition, for the three greenhouses that we are using for our research, on recommendations from John Bartok, he has invested in insulating the knee walls (side walls from bench height to the floor) with blue foam board backed with plywood, sunken into the soil to a depth of 2 ft. He would never have considered making this improvement if we were not conducting research there, but this improvement alone will reduce his energy use significantly even in the experimental control greenhouse.
The grower with whom we are collaborating, Mr. Chris Conant, has been an incredible cooperator. In addition to the knee wall insulation that he did independent of this project, he has assigned his personnel to assist us with various aspects of retrofitting the bubble system at no cost to us. He has been involved in all phases of the retrofitting process. He and his staff have provided critical expertise relevant to greenhouse construction that has contributed to developing an effective bubble system. He has been sharing information about the project with other growers and industry representatives. As a result, a greenhouse tomato grower in Southern Vermont has expressed interest in installing the bubble system in his greenhouses in the future. Mr. Conant has indicated to us that he is extremely pleased to be a cooperator on the project. As he put it “This is the kind of research project I want to be a part of. I would like to collaborate on more of these types of initiatives.”
We have also received excellent support from several specialists from Canada who took part in the original development of the bubble insulation system we are using. Specifically, Mr. Joey Villenueve, greenhouse engineer and president of the consulting company Environment – MJ, has provided ongoing expert support and advice to get the bubble system into operation. The thermal curtain system was efficiently retrofitted in September, 2010 into one of our experimental greenhouses by J.C. Van Der Spek Greenhouse Services, LLC, Berlin, CT.
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