Recipient Organization
SHENDE LLC
6446 COG HILL LN
RAPID CITY,SD 57702
Performing Department
(N/A)
Non Technical Summary
Rapid City (RC) is one of the US cities with the most unpredictable weather. The extant winter greenhouses perform poorly in the frequent high wind, hailstorms and cold winters. South Dakota (SD) farmers are restricted to few crop choices such as corn, soybean, and wheat and a short 6-7-month crop growing period. SD farmers need diversification to prevent economic collapse in an unforeseen event of crop failure. SD has seen extensive investment in high tunnels. Between 2000-2018, the USDA-NRCS has cost-shared at least 100 greenhouses in SD. These only operate between March-October and have a high dependency on fossil fuel heating. Therefore, most produce is transported all year round from other states to meet the local demand. Higher transportation costs and lengthy food miles translate to expensive and/or reduced-quality produce, especially in the remote and rural areas of SD. Produce requiring warm weather or have short shelf life (e.g., raspberries, French beans, okra) is not commonly seen in the markets and is in high demand. Therefore, there is an urgent need to innovate greenhouse structures for superior performance and durability for northern locations with extreme and unpredictable weather.Traditional greenhouses rely on fossil fuels for heating and cooling which may soon become cost prohibitive to many. In contrast, solar greenhouses use free solar energy for heating. However, current winter solar greenhouses are still reliant on ancillary fossil fuel heating and are not designed to withstand frequent high winds or hailstorms. For optimal performance efficiency, solar greenhouses have to be tailor-made taking into consideration the latitude/longitude, meteorology and topography of the location. To the best of our knowledge, no such design for an energy-efficient, wind and hail-resistant solar greenhouse is available for SD. Energy-efficient, affordable, and long-lasting heating system is one the biggest challenge in constructing an extreme winter greenhouse. Renewable energy sources such as the solar, geothermal heat and biomass energy alternatives to fossil fuels are being investigated as heat systems for winter greenhouses. Expensive and laborious deep excavation is required to harness geothermal energy or use the solar-air heat systems. These can drive up the cost significantly. Therefore, we have focused on solar energy and above ground solar-water heat transfer and storage to keep the greenhouse construction and maintenance cost low.We propose to investigate the applicability of a compound parabolic concentrator and oil heat transfer fluid system to convert solar energy to thermal energy. A heat exchanger system located inside the highly insulated greenhouse will transfer the thermal energy to water which will be circulated through the water lines placed in a rock bed. The circulating warm water will sufficiently raise the soil temperature (nighttime temperature>50 oF; daytime temperature >75 oF) to permit cultivation of warm weather crops all year around. At ATaL (average Tilt at Latitude) of RC, solar panels can receive up to 5.27 kWh/m2 /day which is comparable with some of the locations in China that have achieved great success in off-season crop cultivation with the Chinese Solar Greenhouses (CSGs). The CSGs operate all year round in the coldest locations of China without requiring supplemental heating and have successfully augmented the Chinese farmers income. A total of 3.7million hm2 were occupied with horticulture by the end of 2017. We are optimistic that the ERGO greenhouse design will perform as well as the CSGs or even better in extreme weather conditions. Additionally, ERGO will have adequate structural integrity to provide high wind and hail-resilience.Techno-economic analysis using a discounted cash flow rate of return (DCFROR) model will estimate financial performance and economic feasibility. Real-time data from the laboratory scale prototype will identify the strengths and weakness, crucial to progress to manufacturing and marketing of the ERGO product in phase II. This is particularly applicable to RC, which experiences frequently changing weather which would render data from computer simulation inadequate and unreliable. The durability and performance efficiency of ERGO will be tested over the 6-month period during which we expect hailstorms, high winds and extreme cold. Active solar greenhouses are expensive because there are very few companies in USA manufacturing the essential components: polycarbonate and solar hardware. We anticipate that the durable and energy efficient ERGO product will generate an increased demand for winter solar greenhouses which will in turn has the potential to spur more investment in local manufacturing of GH building materials and solar hardware.Parallel to the social benefits offered by a community garden, ERGO also will have the potential to bring communities together with a common goal of improving food security and eating healthy. Community greenhouses will be more productive and profit earning compared with the current community gardens. Solar generation is in infancy in SD. However, in 2020, permits were granted to construct large scale solar facilities in Oglala Lakota county and the Pennington counties in SD (https://puc.sd.gov/Publications/solarfaq.aspx). The "community solar farm" concept can be applied to operate greenhouses reducing investment burden for an ERGO owner.The proposed end users of this product are primarily the urban and small farmers of South Dakota. The letters of support (attachments to proposal) from RC farmers, hobby gardeners indicate their keen desire to supplement current income with profits from selling warm weather produce.
Animal Health Component
40%
Research Effort Categories
Basic
50%
Applied
40%
Developmental
10%
Goals / Objectives
This project designed by Shende LLC in partnership with researchers from the South Dakota School of Mines and Technology (SDSMT), Rapid City, SD will develop an EneRgy efficient extreme weather GreenhOuse (ERGO) with the overarching goal to enable South Dakota (SD) farmers to cultivate vegetables year-round and to provide the farmers much needed crop diversification for increased sustainability and profitability.The extant winter greenhouses (GH) perform poorly in the frequent, unpredictable high wind, hailstorms and cold winters of Rapid City (RC). RC urban farmers have limited crop choices and a short 6-7-month crop growing period. To meet consumer demand, most produce is imported year around from warmer states leading to higher produce prices and often inferior produce quality. Therefore, there is an urgent need to innovate an energy-efficient, hail and wind-resilient winter solar greenhouse for superior performance and durability for northern locations with extreme and unpredictable weather.The objectives to meet this goal are as follows:1. Build the laboratory scale (10 feet X 7.5 feet) ERGO prototype equipped with a compound parabolic concentrator with oil as heat transfer fluid and a double heat exchanger system to convert solar energy to thermal energy. The proposed ERGO design is modeled after the Chinese Solar GHs to enhance the structural integrity to provide superior high wind and hail-resilience.2. Maintain daytime soil temperature within 75-80oF and a minimum nighttime target temperature of 50oF with the concentrated solar power (CSP) system. An ancillary electric space heater will be used when required.3. Document hourly temperature (soil and air), and relative humidity in ERGO macro and microclimate. Record power and water consumption.4. Cultivate Clemson Spineless 80 variety of Okra. Record and evaluate plant growth.5. Perform Techno-Economic Analysis.6. Compare the performance efficiency of ERGO with the solar greenhouse at Wayward Springs Acres, Aurora, Brookings County, SD. GH is owned by Mr. Shannon Mutschelknaus (consultant on this project) who uses climate battery to heat their solar GH.
Project Methods
The project will be carried out in the steps outlined below. City utilities will be contacted to obtain permits if required. The overall goal is to build a 10x7.5x9 (LxBxH ft) laboratory scale ERGO standalone prototype on a 200 ft2 and 6-inch-thick concrete flooring available at the Shende LLC location. Materials common between the Deep Winter Greenhouse (DWG) design and ERGO will be selected from the list provided by the University of Minnesota Extension- https://extension.umn.edu/growingsystems/deep-winter-greenhouses.1. Concentrated Solar Power System consisting of one compound parabolic solar concentrator (each 2 m2 surface area) will be mounted on the GH structure. This product with oil transport receiver tube (borosilicate glass lined stainless steel, 6.5 ft length, 2-3 mm thick, and 10 cm diameter) can withstand temperatures as high as 400oC.2. Insulation: The North wall will be constructed entirely of concrete brick layers, while the East and West side walls will have one-foot-high concrete brick knee wall. Additional insulation will be provided by a thick polystyrene board nailed into the exterior of the side walls and the North wall. The concrete brick wall structure will provide insulation and wind resilience as well. The South wall will be 8 mm twin wall clear polycarbonate rated for an R-value of 1.63 and 80 % transmission. A 0.6-inch flooring of concrete bricks will serve as the first layer of insulation. A network of water lines will be laid over and covered with 0.6 inches layer of rocks followed by a soil bed held with 12 wooden frames. Two such rows of soil bed each 2 feet in height x 9 feet in length and 3 feet in width will prepared for planting providing 54 ft2 of the total 75ft2 interior for planting (72% usage). The clay bricks and rocks and the soil will trap heat during the day. Additional radiant heat from the water lines in the rock bed will keep the plant root zone warm. An additional 1-inch layer of mulch composed of wood chips and straw on the soil surface will create a warm microclimate around the plants and also provide CO2 from decomposition.3. Thermal mass: A single black painted water storage tank fitted with a water level regulator and steam release valve will be located close to the North wall. The water tank will receive water from a dual pipe heat exchanger.4. Retractable thermal blanket and hail protector: At nighttime much of the heat is lost from the glazing. A roll-up thermal Silver/Black insulated Foam Tarp 6' x 25' will double as a thermal and hail blanket. This is a durable 3/15-inch foam insulation inside reinforced polyethylene skin. The blanket can be manually deployed at sunset to cover the glazing and the side walls. If required, we will use crop row covers when lower than normal nighttime temperature is predicted for winter nights.5. Glazing: South wall at a 60-degree angle will provide the most solar gain for the RC location. Shatterproof twin-wall clear VEROLITETM polycarbonate panels (8 mm thickness; R-value 1.63, 80% light transmission) with an anti-drip coating to prevent condensation will provide the optimal solar transmission and wind and hail resistance.6. CO2 levels: Decomposing mulch on soil surface will be the primary CO2 source. We will aim to maintain CO2 levels at a minimum of 340 ppm ambient in outside air. A window installed in door on the East sidewall will be vented manually for cooling in the summer and to increase CO2 when required. The door will remain sealed during the colder months except for operator entry.7. Ancillary heating and lighting: A programmable, 5118 BTU/1500 watts electric space heater with digital summer/winter thermostat and an external sensor cable backup electric space heater supplied by Bio Green PAL 2.0/USDAT Palma and full spectrum LED grow lights mimicking sunlight will be reserved for use when required.8. Data collection: The external meteorological data for Rapid City for the project duration will be obtained from the NREL's SolarAnywhere.com for current hour GHI, DNI, DHI, wind speed and ambient temperature. Shende LLC has 3 thermo-hygrometer to record temperature and relative humidity of the interior, air quality meter (for CO2 levels), thermal images (FLIR C5 compact thermal imaging compact camera). A LI-190 R from Li-COR to measure the PAR (photosynthetically active radiation, 400 nm-700 nm) is also available with Shende LLC. PAR readings inside of the GH will be recorded at 10 min intervals. Temperature, RH, and CO2 levels at the soil level and canopy will be recorded at the 10-minute intervals. Thermal images will be captured at 9 am, noon and at sunset from 3 locations at soil level. Water meter and electricity meter (Supra electricity usage monitor) fitted on the supply lines to the ERGO will record monthly water and power consumption. All the above-mentioned recordings are automated and will be transferred from the measuring devices to the Shende LLC computer hard drive. Consultant Mr. Shannon Mutschelknaus will advise and monitor the data collection process. Similar measurements will be made by them at their climate battery GH for the project period.9. Plant growth evaluation: Okra is ready for harvest in 2 months and continues to produce for 2-3 more months. Okra thrives only in a warm weather. It requires a minimum nighttime temperature of 65oF and a daytime temperature between 75-95oF. We believe evaluating okra plant growth and yield will stringently test ERGO performance. We will germinate seeds of the Clemson Spinless 80 variety in peat pots placed inside ERGO. Later, seedlings will be planted in the plant bed. Seed supplier's water and fertilizer and harvesting instructions will be followed. Plants will be watered manually. We will record the time required for seed germination, flowering and seed pods, yield, shoot length, chlorophyll content, average fresh and dry mass of the plant. Only the yield will be compared with those from literature, seed supplier company and with okra cultivated in RC community gardens in previous years.10. Techno-economic analysis: A discounted cash flow rate of return (DCFROR) model will be used to estimate the financial performance and the economic feasibility. All capital and operating cost estimates will be adjusted to the US 2021 dollars considering the Chemical Engineering Plant CostIndices (CEPCI) and the Consumer Price Index (CPI). Using the $25/ft2 cost estimate for the Aug 2020 DWG prototype V2.2 (https://extension.umn.edu/growing-systems/deep-winter-greenhouses#design-and-construction2066621) as a guideline, we estimate a cost of $75/ft2 for the ERGO prototype. This estimate is based on the lumber price, which almost tripled in the summer of 2022 (https://www.statista.com/statistics/1239728/monthly-lumber-price-usa/), and the additional cost of the solar concentrator and the dual pipe heat exchanger systems.