Progress 04/15/23 to 02/28/25
Outputs
Target Audience:The target audience for this effort to build a prototype of a passive solar greenhouse heated using a solar concentrator and thermal heat exchange system are the small farmers, hobby growers and community gardens located in the cold northerns states of the USA. The prototype was built in Rapid City,SD. The basic design can be further fine tuned for specific locations. Changes/Problems:Changes made to original proposed design and justifictaion was reported in the progress report. What opportunities for training and professional development has the project provided?The project provided opportunity for oneMS student enrolled at the collaborating South Dakota School of Mines and Technology to work with the PIs and learn installation, programing and applying solar concetrator to heat a greenhouse. Under the supervision,the student designed a heat exchanger, aligned solar concentrator with the sun position, downloaded the solar software to track the sun and adjusted angles through iterations,designed lumber placement, and installed sensors conncted them via software for continous data aquisition. Post project ending, PI will continue working toimprovethe heat retention capability of ERGO and make effort to cultivate tropical plants for commercial sale. How have the results been disseminated to communities of interest?The SD Mines publised a news piece on the accomplishment under this grant. The news article can be found at https://www.sdsmt.edu/news/releases/extremeweathergreenhouse.html. Local TV News station (NewsCEnter1) visited the greenhouse and televised the greenhouse prototype in their evening news on May 16th,2025. The PIs have receieved emails and phone calls from locals interested in visiting the greenhouse and learning how it works. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
1. A free standing ERGO prototype of total built area of 124 sq ft which included an "anteroom" and a 75 sq ft grow space was constructed and tested. The anteroom with a door housed a heat exchanger, oil reservoir, and an oil pump. The ERGO was equipped with a 34 sq ft compound parabolic solar trough concentrator weighing approx. 450 lbs. The collector has 97% reflectivity. It was fitted with a single axis digital tracker. The absorber tube on the solar concentrator carried Dynalene Hi-Flow thermal fluid to the oil reservoir. The oil then circulated through a maze of galvanized steel pipes placed three feet below the grow space. This was a closed loop system, and the thermal fluid was circulated by an oil pump. The solar collector and the thermal fluid heated the ERGO during the cold and sunny winter months. The unit was manually switched on sunny and partially sunny days through January 1st to February 28, 2025. The thermostat on the pump was set to approximately 65 oF. The pump was manually switched on an hour after sunrise and switched off one hour before sunset. The pump was switched off on cloudy or partially cloudy days to prevent drawing in cold thermal fluid. On cloudy days, the ERGO kept warm from the residual heat stored in the thermal fluid in pipelines under the soil, the black paint coated oil reservoir, mulch cover and twenty gallons of water in black colored barrels (thermal mass).The grow space was insulated by a wall three feet below soil and a one-foot insulated knee wall. The design allowed growing plants directly in the mulch covered soil of grow space. The ERGO is located on premises of 6446 Cog Hill Lane; latitude: 44.021686; longitude: -103.287755. The east side of ERGO faces an open field with no tall trees or any other physical object obstructing high winds. The prototype withstood the impact of hail, high winds and snow for the duration between March 2024 until the project end date of February 2025. 2.Senors (6) fromiMonnitlocated inside and outside of ERGO recorded air and soil temperature and humidity between October 2024- February 2025. The data collected at every 10-minute interval was wirelessly transferred to a personal computer. 3. Based on the sensor data, the average temperature in the two coldest months of January and February 2025 were 22.4 oF and 17.8 oF. The lowest and highest temperatures in January were 17.1 oF, 78.9 oF. The lowest and highest temperatures in February were -25.6 oF, 65.4 oF respectively. The coldest day of the winter months was February 19, when at 3.00 am the nighttime air temperature recorded outside ERGO, was -25.6 oF. At the corresponding day/time, the temperature inside ERGO was 31 oF (air) and 34.5 oF (soil). Thus, ERGO was able to maintain a difference of approximately 56 oF (air) solely with heat energy transferred from the solar collector and the thermal mass described before. However, this is much lower than the proposed target of maintaining nighttime temperatures above 50 oF. The inability to attain the target >50 oF temperature is primarily because of heat loss at night. This was despite our efforts to cover the structure with a thermal blanket. A more efficient thermal blanket should prevent rapid heat loss and greatly help to maintain an even and >50 oF temperature. Additionally, although the curved (instead of flat) polycarbonate glazing helped to maximize solar gain, it also promoted developing air gaps during the testing period. The airgaps were deemed to be caused bymisalignment between the curved sheets which was exacerbated by weather related expansion and contraction of the glazing material. There was no evidence of hail, wind or snow leading to the formation of the air gaps. The air gaps were sealed with R13 fiberglass roll insulation. However, the air gaps formed once on January 20th and again on February 5th, breached the insulation afforded by the polycarbonate glazing and caused heat loss. 4. The solar collector and heat exchanger system worked efficiently on sunny days, but on 2 or more consecutive cold and cloudy days, failed to adequately heat the greenhouse.It was on those days that supplemental heating was required. 5. Seeds of Clemson Spineless 80 varieties of okra were planted in November 2024. The plants (5) grew to a height of 4-6 inches, but later did not survive the low nighttime temperature and temperature fluctuations experienced in January 2025. Therefore, mid-January 2025, along with a second round of okra; potato, onion and sunflower were planted. The potato, onion and sunflower are less sensitive to low temperatures and survived through February 2025 and continue to grow. It is to be noted that compared with the other plants mentioned here, okra is very sensitive to low temperature and temperature fluctuation. The air temperature recorded at 3:00 am outdoors fluctuated between -11.3 oF (February 16, 2025), -25.6 oF (February 19) and +23.9 oF (February 22,2025). Correspondingly, temperature inside ERGO fluctuated between +38.48 oF (February 16, 2025), +31 oF (February 19) and +48 oF (February 22, 2025). A fan circulating the warmer air at ground level could have reduced the wide temperature fluctuation. 6. Consultant Mr.Shannon Mutschelknaus, owner of Wayward Springs thermal battery solar greenhouse located in Aurora, South Dakota provided data from their temperature and humidity sensors and okra cultivation. The air temperature recorded at 3:00 am by Wayward Springs were 44.9 oF (February 16, 2025) 45.3 oF and 44.9 oF (February 19, 2025) and 50.4 oF (February 22, 2025). A major difference is the location of soil sensors between the two greenhouses. Soil temperatures were recorded by sensors located 4 feet below ground by Wayward springs while the ERGO sensors were only 4 inches below ground. The Wayward springs greenhouse maintained a higher temperature ( >45oF) and experienced less temperature fluctuation. The okra plants performed better in this greenhouse. 7. Preliminary cost estimates were performed to scale up a greenhouse to 2000 sq. ft. Based on the fixed and variable costs, the construction cost would vary from $36.97/sq. ft to $52.02/sq. ft. For these estimates, the fixed cost was the material (lumber, concrete, polycarbonate) and equipment (solar, pump), whereas variable cost mainly comprised contractual labor.A greenhouse prototype of 124 ft2was built, and the baseline parameters, such as dimensions of the polycarbonate roof, heat exchanger capacity, heat gain by the soil and greenhouse air, thermal fluid, pump flow rate, and solar collector capacity, were evaluated. The non-toxic thermal fluid from Dynalene has a wide operating range of -100oF to +400oF which prevented oil thickening during the coldest winter months. On one of the coldest days in February, a temperature differential of 60owas established using the online soil sensors. For 2000 sq. ft, the heat gains of504,000 BTU or 147.7 kWh/day (6 hours of sunlight activity)were estimated using 0.7 BTU/hr.sq ft.°F heat transfer coefficient of polycarbonate. Assuming 6 months of fall/winter conditions, heat gains of 26,460 kWh could be estimated with the monetary value of $3,913.43 at the current rate 14.79 cents/kWh. The cumulative cash flow estimates for an initial investment of $73,940.20 (fixed+labor) yielded a breakeven 7.5 years if heat gain value was complemented with a low-end $8,000 profit/year from the produce sales.
Publications
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Progress 04/15/23 to 04/14/24
Outputs
Target Audience: During this period, Shende LLC contacted 1.Collaborator South Dakota School of Mines and Technology to facilitate providingsub-award. A student (Mr. Grant Bauer)was hired to work on a solar concentrator for the greenhouse as a part of their MS thesis project. 2.Mr. Paul Soucy, owner of Environmental Solar Systems (Envsolar)company based in Massachusetts delivered the solar concentrator viaUline to Rapid City, South Dakota. 3.Permission from the Red Rock Meadows Homeowner's association was obtained to construct the greenhouse at t6446 Cog Hill Lane, Rapid City, SD location. Permission was granted with a promise to remove the greenhouse structure after completion of the project and submission of the final report to the funding agency. 4. Material for greenhouse construction was purchased fromGreenhouse Megastore. 5.It became evident that I will need to hire a contractor to construct the structure as several items in the structure were heavy and needed a lot more experience in construction. Therefore, Bang-Up construction and Silverback plumbing were contracted to do most of the heavy construction work. 6. Shannon Mutschelnaus, owner of Wayward Springs, SD and an evaluator on this grant visited the site and evaluated the partially completed greenhouse structure. He provided valuable input on positioning of the sensors and underground. Changes/Problems:1. Thefinancial advisor budgeted in this grant moved away and the principal/owner (PI on this grant) took over the tasks of financial management and accounting. 2.Construction of ERGO involved heavy lifting and use of heavy machinery which the PI found imposible to undertake by herself. Therefore, she paid a construction company suggested by local Menards store,to perform the heavy duty tasks. 3.ERGO constuction was completed by the end of April 2024. The weather had started to warm up and it was not an ideal condition to test ERGO. Therefore, the PI requested a no-cost extension to allow testing ERGO during the cold days of winter. 4. The compound parabolic solar concentator manufactured by Environmental Solar Systems based in Massachusetts was only available in 1 size which was too large for ERGO. A custom built would have been too expensive. The delivery of the fragile solar concentrator via ULINE to Rapid City proved more expensive than anticipated. 5. The solar concentrator had to be embedded in cement flooring to stabilize against high winds and hail. This was an unexpected task and expense. 6. The PI had difficulty convinicng the Red Rocks Home Owner's Association to permit construction of ERGO at the 6446 Cog Hill Location. The HOA has permitted ERGO to remain at this location until June1st 2025 after which it will have to be removed/relocated. The PI is planning to relocate it to the commercial real estate owned by Shende LLC. However this location needs utilitiy connections. What opportunities for training and professional development has the project provided?1. The project provided training opportunity to Mr.Grant Bauer who learnt installation and operation of the compound parabolic solar concentrator and design of a double heat exchanger system for greenhouse application. The information and training beacme part of his MS thesis submitted to the South Dakota School of Mines and Technology. 2.The project allowed interaction with building contractors, homeowners assocation and students at the South Dakota Mines to learn about this project. Their collective efforts and input helped to make changes to the greenhouse design and was a great learning opportunity for the owner of Shende LLC who had no prior experience in actual construction of a solar greenhouse. How have the results been disseminated to communities of interest?During this period, only the construction of the ERGO was completed. Data collection will begin in September 2024 through the cold days of winter. Therefore, there areno results yet to share with the collaborators or the community. What do you plan to do during the next reporting period to accomplish the goals?In the next reporting period Shende LLC will 1.Collect data of daytime and nighttime temperature during the cold winter days between September 2024-Feb 2024. 2. Analyze temperature data to conclude performance of the ERGO during cloudy and sunny days. 3. Plant Okra seedling in September and make attempts to grow the plants through winter. 4. Compare performance of ERGO with the thermal battery greenhouse owned by evaluator Shannon Mutschelknaus of Wayward Springs, SD. 4. Perform techno-economic analysis for commercialization.
Impacts
What was accomplished under these goals?
Materials to construct the laboratory scale ( 10 feet X 7.5 feet ) ERGO prototype was completed with the help of MS student hired at the collaborating South Dakota School of Mines and Technology, Bang-UP construction and Silver back Plumbing. A compound parabolic solar concentrator purchased from Environmental Solar Systems, Massachussettes, was installed and conncted to the double heat exchanger system.Sensors for temperature and humidity purchased from Monnit were installed for data collection, Shannon Mutschelknaus visited the site and provided input regrading location of the sensors and improving the soil quality to cultivate okra. By the time the construction was completed, the weather had warmed up. Shende LLC with permission from the program leader, requested a no-cost extension to allow gathering data in the winter months.
Publications
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