Novel approaches to improve energy efficiency in northern New England greenhouses
Growers are using greenhouses more than ever to reduce loss due to poor weather and increase the length of the growing season. Hoop houses are inexpensive to erect, but require excessive energy, especially in northern New England. 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 energy conservation systems, a soap bubble insulation system developed in Canada, and a commercially-produced thermal curtain, have been retrofitted into separate gable-style 88 ft. greenhouses at the largest greenhouse ornamentals operation in Vermont. Monitoring equipment has been installed to quantify energy use and savings over time relative to ambient temperature. A greenhouse grower survey was conducted on energy use in the tri-state region. Based on responses from 53 growers, 91% spent less than $10,000 per year on electricity and 62 percent spent less than $10,000 on propane or oil for heating. Twenty-four percent of the respondents used $10,000-25,000 on fuel. When asked what actions they take to save energy, three measures were identified by over 50 percent of the respondents: adjusting their planting dates, sealing gaps around doors and vents, and checking the furnaces annually. The expense of implementing energy saving measures was identified as the most limiting factor, and providing tax incentives for energy conservation was cited as the most helpful for encouraging them to adopt energy conservation practices. Energy audits, performed by an USDA, NRCS certified TSP were completed in 4 commercial greenhouse operations in Vermont. Plans are underway to conduct audits in New Hampshire and Maine. Data gathered from audits in Vermont and the three experimental greenhouses are being compiled and analyzed to determine for growers the costs and benefits of using different energy conservation methods.
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.
Over 1,650 growers will receive information about energy conservation in greenhouses. Of the total growers receiving information, 5% (~80 growers) will implement at least one recommended tactic in one 2,000 sq ft greenhouse (total 160,000 sq ft), resulting in an annual reduction of energy cost of $500 per greenhouse grower operation. One grower per state (3 growers) will retrofit at least one greenhouse with either a bubble or thermal blanket insulation system, resulting in a yearly cost savings in fuel use of $1,000.
Obj. 1. The grower cooperating on this project complained that the thermal curtain as installed by the commercial company limited the placement of potted plants towards the outer edges of the benches in the greenhouse. We relayed this to the installer on behalf of the grower which led the installer to shorten the curtain and relocate weights to hold it down. This problem was resolved at no additional cost to the project or the grower, and made room for about 200 potted plants on the outside edges of the benches.
The bubble insulation system has had continual problems that required adjusting and fixing. This system is experimental and had never been retrofitted into a single gable-style greenhouse. The following major problems were a. foam generators were frequently knocked off by the flapping plastic, and b. leaks in the system resulted in significant loss of the soap solution. Some adjustments have been made to correct these problems: a. rubber grommets that held the foam generators on the pipe were replaced with solid brass porous tube designed by a local engineer to keep them in place; specially designed plastic lifters were installed along the ridgeline to keep the outer layer of plastic above the foam generators; b. the separate sections of aluminum gutter that carry the solution back to the tank were welded together to minimize expansion and contraction and prevent leakage of the soap solution.
Obj. 2. Collection of assorted energy consumption and weather data is being done by EnSave, a commercial company. They purchased and installed the equipment in and around the three experimental greenhouses. Based on analysis of temperature and fuel use data generated in 2011, a report was prepared by Ensave comparing energy use in the three test greenhouses. The house with the bubble insulation system used 10.7 percent more electricity than the control (unimproved) house and 23.6 percent less natural gas. The house with the curtain used 0.1 percent more electricity and 14.2 percent less gas than the control house. Whereas the thermal curtain did save on fuel use, it was not as much of a saving as expected. That may be because a gable or hoop greenhouse is relatively short and has minimal space above the curtain compared with a gutter-connected house. This reduces the benefits of the curtain and suggests that the bubble system may be better for energy conservation in hoop houses. Plans are underway to install digital thermostats in the three greenhouses and an automatic opener for the curtain. These improvements are expected to enhance energy conservation and provide more meaningful data on differences among the three treatments.
Obj. 3. Information on the cost of retrofitting the greenhouses is being compiled as the project progresses. These data will be used to determine the expenses associated with actual retrofitting the structures for energy conservation and included in final calculations relevant to cost-benefit of the systems for growers.
Obj. 4. A 2-page survey dealing with energy usage and conservation measures was developed and sent to over 2000 growers in the tri-state region. It was also placed on our Entomology Research Laboratory website (http:/www.uvm.edu/~entlab/). Additional copies of the survey were handed out to growers at our January 2011 workshops to encourage participation. Some preliminary analyses of the results have been completed. Based on responses from 53 greenhouse growers 91% spent less than $10,000 per year on electricity, and 62 percent spent less than $10,000 on heating fuel. Twenty-four percent used $10,000-25,000 on heating fuel. When asked what actions they take to save energy, three measures were identified by over 50 percent of the respondents: adjusting their planting dates, sealing gaps around doors and vents, and checking the furnaces annually. Cost was identified as the most significant factor limiting implementation of energy saving measures and providing tax incentives for energy conservation was cited as the most helpful for encouraging them to adopt energy conservation practices. Additional results will be available in the future.
Obj. 5. A short questionnaire was prepared and revised by the cooperators to select the growers who will receive energy audits through this project in New Hampshire and Maine. We felt it was important to identify growers in these states who had sufficient greenhouse space and would benefit most from such an audit. The project PIs assisted growers with completion of applications for the NRCS EQUIP program, which will allow them to receive the audit and support for implementing energy saving measures in the future. Energy audits were completed by John Bartok in 4 Vermont commercial greenhouse operations. The growers specifically requested the services of Mr. Barkok because they felt he could appreciate their energy issues. Final reports of the results and recommendations for improving energy conservation are being prepared and scheduled for distribution in January 2012.
Obj. 6. Workshops were held in ME, NH and VT in January 2011. Growers received handouts on energy conservation and a short presentation of the scope of this project was given. A short video of the bubble insulation system in operation was shown. Growers were very interested in the option. In the workshop evaluation, energy conservation was listed as a topic growers wanted to learn more about in the future. Workshops are scheduled to take place in the ME, NH and VT in January 2012. A summary of results from the grower survey will be distributed. A summary of our progress will be given at each session and time will be available for questions. The PIs prepared a short article for the Small Farmer Quarterly. http://www.smallfarms.cornell.edu/pages/quarterly/archive/fall%202011/C5.pdf
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 about one year, and thus none of the grower-linked milestones have yet been met. However, in the first 2 months of the project (fall 2010), the commercial grower who owns the greenhouses where the research is being conducted observed a two-fold savings in gas consumption in the house with the thermal curtain compared to the unimproved control house. As the project proceeded, based on data generated through this project, it was shown that 23.6 percent less gas was used in the house with the bubble insulation system and 14.2 percent less gas was used in the house with the thermal curtain than in the control house. Of note is that completion of the retrofitting and necessary improvements to the bubble insulation system is ongoing. We anticipate by January 2012 it will be in full operation with all of the technical improvements installed. In December 2011, a consultant from Israel who took part in the original design of the system in Canada, is scheduled to assist us with resolving persistent problems with leakage and controllers for the bubble system.
Impacts and Contributions/Outcomes
Despite the additional cost and various problems associated with retrofitting the greenhouses, the cooperating grower has already noticed a significant reduction in gas consumption in the greenhouse with the thermal curtain compared with the unimproved greenhouse. Both of these greenhouses were filled with poinsettias destined for sale during the holidays. As a result of the apparent cost-savings, the grower intends to install a thermal curtain in another greenhouse (at his expense). In addition, for the three test greenhouses, 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 unimproved control greenhouse. The grower plans to install digital thermostats to upgrade his temperature controls in the three experimental greenhouses and a controller to open and close the thermal curtain automatically based on daylight, which should enhance its energy saving effectiveness.
The collaborating grower, Mr. Chris Conant, has been an incredible cooperator. In addition to installing the knee wall insulation which 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 shared 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 involved in the original development of the bubble insulation system. 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. Mr. Stephen Vineberg, the owner of Sunarc, has donated soap concentrate for the early testing phase of the system. In addition, Mr. Ilan Sadon, IGOS.MN LTD., Engineering Products Management, from Israel has provided additional assistance. Adjustments to the thermal curtain were by the staff of J.C. Van Der Spek Greenhouse Services, LLC, Berlin, CT. Redesigns and adjustments to the bubble insulation system were made with assistance from Peter Skinner, engineer and owner of E2G Solar.
Four growers received an energy audit at their greenhouse operation conducted by John Bartok, who recently received certification by the Natural Resources Conservation Service as a Technical Service Provider (TSP). While other TSPs were available in the region, the growers all specifically requested that Mr. Bartok do the audit. They felt it was critical to have a person experienced in greenhouse energy issues conduct the audit so they could accompany him during the audit and ask questions as necessary to better understand the benefits of implementing suggested adaptations. All of the growers who received audits indicated that they intend to make at least some of the changes recommended by Mr. Bartok. They all are eligible to receive support from NRCS to make these changes.
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