Novel approaches to improve energy efficiency in northern New England greenhouses

Obj. 1. Assess two innovative energy-saving devices retrofitted into a greenhouse: a bubble insulation system and an energy/shade curtain system.

Options for installing an energy curtain were investigated, and J.C. van der Spek Greenhouse Services, Berlin, CT specializing in retrofitting curtains for double-poly greenhouses was identified. The energy curtain, Model Ener-Shade, using XLS 15 Firebreak – heat retention and shading cloth was installed. The cost was $10,800. The curtain as installed limited the placement of potted plants towards the outer edges of the benches. To correct this, the installer shortened the curtain and relocated weights to hold it down. This redesign made room for about 200 potted plants on the outside edges of the benches.

Installing the bubble insulation system was more complicated than anticipated. The system was not available “off-the-shelf”. We purchased a prototype system from a grower in Canada. The system as purchased was designed by Sunarc Canada and was installed in a 220 ft. gutter connected greenhouse. It required significant modifications to retrofit it into the 88 ft long greenhouse at Claussen’s Florist & Greenhouses, Colchester, VT.

Assessment. Although the bubble insulation system had continual problems that required adjustment, redesign and repair, significant data were accumulated that clearly demonstrated energy savings in the greenhouses fitted with the curtain and the soap bubble insulation systems (Table 1). Data from the winters of 2012, 2013, 2014 when averaged showed a 40% less natural gas usage in the soap bubble insulated greenhouse when compared to the unimproved greenhouse. This represented an average savings of $636 per year. This dollar savings surpasses the $500 per year savings as projected in our performance target. Data from the 2012, 2013, 2014 winters when averaged showed a 26% less natural gas usage in the thermal curtain insulated greenhouse when compared to the unimproved greenhouse. This represented an average savings of $426 per year. Using data of dollar savings and comparing the soap bubble insulated greenhouse to the thermal curtain greenhouse one saves an additional $210 by installing a soap bubble insulated system.

The 2013 winter was unusually mild, which reduced the impact of energy savings from the two energy conservation systems compared to the control house. This was true when comparing energy use the fall 2013 to the winter 2014 growing season. Energy savings increased as the outside temperatures decreased. Energy usage and savings is presented in Table 2 and Fig. 1. Data are based on the amount of natural gas used and its cost (which in 2014 averaged $1.30/ccf).

The greenhouses used for this study were heated with natural gas which is a relatively inexpensive fuel. Propane users would see about four times the savings as those stated above and fuel oil users would see twice the savings stated above.  One slight issue we’ve experienced is that the grower needed to run the three test houses at different temperatures to meet the needs of the plants in each one. This makes it harder to compare the gas use in the three greenhouses. We consulted with a greenhouse energy conservation specialist, Mr. John Bartok, and were given a formula to use to pro-rate the usage of the houses to make the data equitable for comparison. An example of the pro-rated gas usage data comparing the three greenhouses for fall 2013 and winter 2014 heating periods is shown in Fig. 2 and 3.

Key components and beneficiary actions. The following were some early problems needing constant attention in the greenhouse retrofitted with the soap bubble insulation system: a) foam generators were frequently knocked off the main aluminum tube going down the length of the greenhouse by the flapping plastic covering and b) leaks in the system, especially along the gutters that carry the solution back to the tanks, resulted in significant loss of the soap solution. We developed improvements to eliminate these problems such as: a) rubber grommets that held the foam generators on the air supply pipe were replaced with rigid brass tubes that passed through the aluminum pipe and securely held each foam generator in place, b) plastic forms were designed and manufactured which once installed along the ridgeline, held the outer layer of plastic above the foam generators to prevent them from pushing on the generators, and c) bolted unions connecting the sections of gutter were welded together to minimize expansion and contraction and prevent leakage of the soap solution from these areas. 

While it was encouraging to have corrected these earlier problems, additional problems developed: a) recurring leaks of the soap solution because of small tears in the plastic coverings; b) an O-ring in a critical valve failed due to high temperatures in the greenhouse during the summer; c) soap bubbles were of inferior quality due to dilution of the soap solution, and d) spray nozzles in the foam generators frequently clogged with debris. The following adjustments were made to correct these problems: a) the plastic covering the greenhouse was replaced and care was taken to make it tighter than in previous years to reduce flapping; b) broken valve was replaced with a heavy-duty manual one and care was taken to ensure that the greenhouse exhaust fan operated during the summer to keep internal greenhouse temperatures below damaging levels; c) special tubes were installed between the two layers of plastic to permit the unrestricted flow of the solution to the collecting tanks; d) a laboratory-based foam generator device was designed to allow for precise testing of the soap solution to determine the best soap:polyethylene glycol (carbowax, an antifreeze) ratio to maximize freeze protection while maintaining bubble quality, and e) the Hayward in-line soap solution filter was replaced with a 43-micron stainless steel element to increase its ability to filter out particulates which could clog the nozzles.

Many redesigns to the original system were made to correct flaws in the system. For example, because of cracking of the bubble generators, a new schedule 80 PVC reducer was sourced and a new sturdier generator assembly developed. A new approach would locate all of the air and solution piping, tubing, and generator assemblies under both layers of plastic rather than up and in between them. This will allow for servicing the generator nozzles and all of the piping/tubing unions without having to remove the inner plastic layer.

Objective 2. Conduct comprehensive energy audits before and after retrofitting the greenhouses to quantify the benefits of both devices.

Energy consumption, interior greenhouse conditions, and weather data were collected by EnSave, Richmond, VT, a local energy analysis company. We also recorded natural gas usage daily during the period of operation of the systems. An energy audit was conducted by EnSave in 2010, at Claussen’s Florist and Greenhouses, Colchester, VT which provided baseline data on energy consumption for this SARE project. We determined that recording daily gas usage was a simpler and more effective means of assessing the benefits of both insulation devices. Therefore, an audit after retrofitting the greenhouses was not conducted, as it would not have contributed significantly to the overall assessment of energy conservation for this project.

In 2012 digital thermostats (Model G-Stat 4, Griffin Greenhouse Supply Co.) were installed in the three greenhouses and an automatic opener and closer for the thermal curtain. These new devices provided accurate comparable control of temperatures in each greenhouse and ensured that the curtain opening and closing coincided with operation of the soap bubble system.

Objective 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.

The 2010 cost of retrofitting one 88 ft. long greenhouse with a thermal curtain by J.S. van der Spek Greenhouse Services was $10,800. The Model was an Ener-Shade with a XLS 15 Firebreak heat retention and shade cloth. It took two men two days to install it. The cost would have been less if the installation occurred at the time the greenhouse was constructed. It is not possible to present a cost for retrofitting a greenhouse with a soap bubble insulation system because (a) the entire system based on 3 years of testing requires significant improvements in design and (b) it is not commercially available.

 Although the bubble insulation system had continual problems that required adjustment, redesign and repair, significant data were accumulated that clearly demonstrated energy savings in the greenhouses fitted with the curtain and the soap bubble insulation systems (Table 2). Data from the winters of 2012, 2013, 2014 when averaged showed a 40% less natural gas usage in the soap bubble insulated greenhouse when compared to the unimproved greenhouse. This represented an average savings of $636 per year. This dollar savings surpasses the $500 per year savings as projected in our performance target. Data from the 2012, 2013, 2014 winters when averaged showed a 26% less natural gas usage in the thermal curtain insulated greenhouse when compared to the unimproved greenhouse. This represented an average savings of $426 per year. Using data of dollar savings and comparing the soap bubble insulated greenhouse to the thermal curtain greenhouse one saves $210 by installing a soap bubble insulated system.

 Energy savings are also presented in Objective 1 above. In general information on potential tax incentives was not determined because the Federal Government’s time limits on availability are often short and frequently change yearly or monthly. However, information on tax incentives for energy audits can be found in Objective 5 below.

Objective 4. Conduct a survey to generate baseline data on current energy consumption and conservation used by greenhouse growers in the tri-state region.

A survey was developed to collect information from growers on their greenhouse energy usage and conservation measures 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 several greenhouse grower workshops to encourage participation. The purpose of the survey was to learn what growers are doing currently for energy conservation in their greenhouses. Based on responses from 53 greenhouse growers 91% spent less than $10,000 per year on electricity, and 62% 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% 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.

 Key outcomes:

Responses differed significantly in the three states. Following is a summary of the most important findings:

• 56.6% of the growers surveyed were retail vegetable growers, 66% were retail ornamental growers and 52.8% were co/owners of a horticultural business
• 34.0% had 1-2 full time employees, 26.4% had over 6, 13.2% had 3-4 and 17% had none.
• Bedding plants accounted for 28.5% of revenue for the growers surveyed, 11.8% were vegetables, 11.7 were flowering potted plants, 11.3 were perennials and 9.5 were vegetable starter plants.
• About 50% of the operations had less than 10,000 ft² of greenhouse space; 26.4% had 10,000-25,000 ft².
• Across all three states, the percentage of greenhouse space used increases from January to May. Usage peaks in May to 95.3% and gradually decreases over the rest of the year
• 49.1% of the growers surveyed use oil to heat their greenhouses, 47.2% used propane gas, and 22.6% used wood fired heaters.
• 62.3% of those surveyed spent less than $10,000 on fuel annually; 5.7% used $25,000-50,000.
• To save energy 58.49% of the growers surveyed adjust their planting dates, 56.6% seal gaps around doors and vents, 51% get their boiler or furnace checked annually, 45% insulate the endwalls, 28% use bottom heat, 23% use energy efficient light bulbs. 47.2% use electronic thermostats and horizontal air flow systems, The most popular energy saving measure for all states surveyed was adjusting planting dates (of total)
• When asked what limits them from improving energy conservation, 37.7% said it was too expensive, 17% said they didn’t have time or didn’t know the cost benefits, 15% didn’t know if they qualified for tax incentives and 11% didn’t know what to do.
• When asked what would help them adopt more energy conservation measures, 51% said providing tax incentives would be the most helpful; 43% said providing free energy audits, 40% felt they needed assistance with learning what programs were available to help them.
• When asked what research information would help them adopt more energy conservation, 39.6% said cost benefit analyses would be the most helpful, 34% said learning what benefits they would receive from making changes would help, and 21% felt guidelines on what to do to reduce energy use was needed.

A complete summary of survey results and data can be found in Appendix A.

Objective 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.

Growers attending the annual Tri-state Greenhouse workshops were notified about opportunities to receive energy audits to assist them with improving their energy conservation. The project PIs interacted with several growers in the region, particularly in Vermont and New Hampshire, to assist them with linking with USDA Natural Resource Conservation Service (NRCS) offices to arrange for a federally-funded energy audit. NRCS has a program that partially funds energy audits for growers, and our goal was to assist growers with signing up for this service. Growers who have had an energy audit completed by a federally-registered technical service provider are eligible to apply for funds to implement improvements. Several issues were identified that hinder growers from taking advantage of these federal opportunities. Specifically, the application process is complicated and time-consuming; it is difficult in some states to determine what services NRCS will support (it isn’t consistent across all states); there are deadlines for submitting applications and receiving NRCS support; and lastly the services provided by the auditors vary widely (some auditors produce audits in a format that are more useful than others). Despite these barriers, energy audits were completed in nine commercial greenhouse operations, six in Vermont, and three in New Hampshire. We felt it was important to identify growers in these states who had sufficient greenhouse space and would benefit most from such an audit. All of these audits were conducted by Mr. John Bartok, Greenhouse Agricultural Engineer and Extension Professor Emeritus from the University of Connecticut. He has over 40 years of experience working on greenhouse energy conservation, and is highly respected in the greenhouse industry. We found that the growers with whom we were working specifically requested his services because of his expertise and ability to present information to them in a way they could clearly understand.

The growers receiving these audits indicated that the information was very useful. One of the growers was so enthusiastic about what he learned that he hosted a workshop to encourage other growers to arrange for audits. Another of the growers receiving an audit owns the largest greenhouse operation in Vermont. He spends over $275,000 on heating fuel and $50,000 on electricity. His experience vividly demonstrates the value of audits. He recently gave a presentation on the energy conservation from the grower’s perspective (see his complete presentation in Appendix F). As a result of the audit, he developed a 5-year plan for carrying out recommended improvements. This included replacing the boilers in six of his greenhouses because he recognizes the savings he will ultimately realize from these improvements. He also has installed digital thermostats to enhance his energy savings. He is considering installing an energy curtain in one of his greenhouses because of the energy benefits he observed in the test greenhouses at his operation.  This is what he had to say after the audit, “this program is essential to our understanding, implementation, and capital expenditures spent on energy conservation.  The Energy Audit that was conducted by John Bartok will become a “bible” for our company in the future to not only save on energy expenses, but aim to guide/improve all of our company’s production profitability projections during the planning stages of the future. We will continue to implement energy saving measures throughout the operation in the coming years to not only to work on existing equipment/projects, but determine our need for future capital improvements for energy conservation because of this energy audit conducted.  Thank you for this opportunity.”

We facilitated linkages between growers, energy audit providers, and the Federal agency providing the funding (NRCS) for the audits. Through our involvement growers received energy conservation information in a format enabling them to take positive action to implement the recommendations provided by the audits. The project PIs assisted numerous other 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.

Objective 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.

Day-long workshops were held in ME, NH and VT in January 2012, 2013, 2014, and 2015. Growers received handouts on energy conservation and presentations on the scope of this project with results and discussion. A 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 that growers wanted to learn more about in the future. Several opportunities occurred to demonstrate the bubble and curtain systems for growers and regional specialists. For example, a tour of the site 10 members of the Northeast Horticulture Inspection Society was held in mid-April 2012. People were very intrigued by it. A University of Vermont undergraduate student prepared a video describing the system for Vermont Independence Day (http://www.youtube.com/watch?v=W9lOxF_jOZE)

During 2013 we had two other opportunities to present information about energy conservation, and specifically these systems. In July, 2013 the Board of Directors of the American Floral Endowment, a leading national greenhouse/floriculture industry association received a tour of the SARE funded research site. This group of 20 leaders in the industry was fascinated with the project and impressed by the grower involvement in the project. Additionally, a presentation to 50 greenhouse growers from New Hampshire at the annual meeting of the New Hampshire Horticulture Association was given. The growers were interested in the technology, and requested an on-site demonstration in the coming year.

The “Vermont Greenhouse Energy Extravaganza” was held on Thursday, September 4^th 2014 at Claussens Florist and Greenhouse, Colchester, Vermont (see Fig. 4-6). It was a day-long conference with sessions on energy conservation and demonstrations of the soap bubble insulation system and energy curtain. Mr. John Bartok, Professor Emeritus, University of Connecticut and Mr. Chris Callahan, University of Vermont Extension gave presentations and tours of the greenhouses discussing important areas for conservation improvements. Mr. Bob Kort, USDA NRCS, presented information on government funding for energy conservation. Forty-five attendees came from throughout the Northeast. Breakout sessions and demonstrations of the soap bubble insulation and energy curtain equipped greenhouses were given. The entire program for the event can be seen in Appendix B.  In general, participants thought the workshop was very informative and stated that they learned a great deal about energy conservation in greenhouses and would likely pass on the information to other growers.  An executive summary of participant evaluations of this event is provided in Appendix B1.

Objective 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.

A seven-page guide titled “Retrofitting a Greenhouse for Energy Conservation” was produced in August, 2014. The guide was prepared for growers to assess deficiencies and make energy conservation improvements to their greenhouses. Areas addressed were: tightening up the greenhouse, insulating, windbreaks and air flow, electrical efficiency of cooling and heating systems, and lighting. At the end of the guide is a checklist for growers including all topics covered. Approximate energy cost savings are given. The guide was distributed at the September, 2014 Energy Extravaganza, at the January,2015 Tri-State Greenhouse IPM workshops in Maine, New Hampshire and Vermont, and at the Green Works Vermont Nursery and Landscape Association Winter Meeting on January 27, 2015. It is available on the UVM Entomology Research Laboratory web site (www.uvm.edu/~entlab/). The guide is also included in Appendix C.

Milestones

1.  At least 450 growers will learn new energy conservation concepts while attending workshops in ME, NH, VT (150 growers per year), of which 30% will implement one or more energy saving measures presented. The energy conservation measures presented will be based on results from quantitative energy audits performed in 9 commercial hoop houses (3 in each state [ME, VT & NH]); from which sources of energy loss will be identified and recommendations for energy conservation made.

Results. Approximately 750 growers were introduced to the soap bubble greenhouse insulation project while attending the Tri-State Greenhouse conferences in the years 2011 through 2015. The conferences were held in ME, NH and VT. Presentations were given and informational handouts distributed. The energy audits provided insight into what energy conservation practices were most lacking and helped guide the development of the “Retrofitting a Greenhouse for Energy Conservation” guide completed in August 2014. It was distributed at the September 4, 2014 Energy Extravaganza, the January 2015 Tri-State Greenhouse conferences, and at the Green Works Vermont Nursery and Landscape Association Winter Meeting on January 27, 2015. Several growers have implemented other conservation measures identified in the audits and outlined in the guide.

 2.  Over 200 growers will attend an open house demonstrating the bubble insulation system and energy/shade screen system in retrofitted hoop greenhouses, where a cost/benefit analysis will be presented comparing energy conservation in a retrofitted vs. a non-retrofitted greenhouse. At least 2-3 growers who attend will indicate their intention to investigate its use in their operation. The local press will be invited to attend.

 Results. The September 2014 Energy Extravaganza provided an opportunity for 40 growers attending the conference to see both the soap bubble insulated greenhouse and the greenhouse with the energy/thermal curtain. Both systems were demonstrated and explained and question and answer periods provided. Our personnel led the bubble greenhouse tour and questions while Hans van der Spek of J.C. van der Spek Greenhouse Services (who installed the energy curtain) led the demonstration and discussion of the energy/thermal curtain equipped greenhouse. A six-minute video of the greenhouse project was produced which clearly describes both the bubble and energy/thermal curtain greenhouses and the energy savings and costs/benefits associated with each. A link to this video can be found on the UVM Entomology Laboratory website (http://www.uvm.edu/~entlab/Bubble%20Greenhouse%202010/BubbleGreenhouse.html) or directly on YouTube (https://www.youtube.com/watch?v=yRAzv44cEJw&feature=youtu.be). This video has been shown at the 2015 Tri-State greenhouse conferences and at the January 27, 2015 Green Works conference (winter meeting) held at the University of Vermont. These showings of the video have reached 200 growers.

Five growers, two in Vermont, one in New York, and two in Quebec, Canada have expressed an interest and intention to install a soap bubble insulation system in their greenhouses.

 3.  At least 200 growers will complete a survey on energy conservation, and the results will lead to development of effective programs to encourage 30% of the growers attending the workshops to implement energy conservation measures.

Results. See Objective 4 above in Results and Discussion section. Over 700 growers received a manual entitled “Retrofitting a Greenhouse for Energy Conservation” written, peer-reviewed and published by scientists involved in this SARE project (Appendix C). It is projected that ~200 growers will adopt one or more of the energy saving measures described.

 See Objective 7 above in Results and Discussion section for additional information.

• Appendix C: “Retrofitting a Greenhouse for Energy Conservation” Guide
• Tables and Figures
• Appendix E: Greenhouse Management Magazine article
• Appendix A: Grower survey and results
• Appendix F: Grower Energy Conservation Presentation
• Appendix B1: Energy Extravaganza Executive Sunmmary of Evaluations
• Appendix B: Energy Extravaganza Program
• Appendix D: Cornell Small Farm Quarterly article