Non Technical Summary
The development of large scale solar energy projects in rural areas usually means taking productive farmland out of production. This reduces the food supply in the US and eliminates agricultural jobs.This project will develop a way to produce both clean electricity and high value crops on the same land. A new type of flexible solar panel will be developed that is light weight, inexpensive and uses a light shifting pigment to increase crop production. The panel can be integrated directly into a conventional hoop house to gain both clean electricity and higher productivity with covered agriculture.Combining solar with covered agriculture can (1) generate power in agricultural zones without sacrificing productive farmland, (2) provide agricultural jobs to the community, (3) reduce water consumption with lower evaporation and (4) increase crop yields. A WIN-WIN-WIN-WIN scenario.

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
402	0120	2020	100%

Knowledge Area
402 - Engineering Systems and Equipment;

Subject Of Investigation
0120 - Land;

Field Of Science
2020 - Engineering;

Goals / Objectives
The goal of this project is to combine solar power generation with an agricultural hoop house that can (1) generate power in agricultural zones without sacrificing productive farmland, (2) provide agricultural jobs to the community and (3) reduce water consumption with increased crop yields. A WIN-WIN-WIN scenario. To achieve this goal we will develop a semi-rigid luminescent solar panel that can be integrated into a hoop house with a curved roof. The panel will need to pass durability tests for a minimum of 10 year lifetime and 100MPH wind load to be practical. To deliver on a commercially viable product we will focus on 5 deliverables. The methods used for these objectives are given in he methods section of this report.Objective 1: UV stability of semi-rigid materials set. This deliverable will test the UV stability of the current 4-layer polymer stack with and without a UV absorbing fluoropolymer coating. Deliverable 1: Extrapolate UV stability of full stack to 10 years using high intensity UV and high temperature accelerated tests.Objective 2: Mechanical durability testing. The semi-rigid panels and test frame will be subjected to a series of mechanical stress tests that includes static loads and dynamic loads that simulate winds of >100MPH winds. Deliverable 2: <10% degradation in power after static and dynamic mechanical load tests.Objective 3: Installation in test greenhouse. The existing Soliculture research greenhouse at Whiskey Hill farms will be the site for field tests. Deliverable 3: A labor cost of $0.60/sq.ft. of greenhouse space for installation of the hoop house, panels and PE covering. Full spectral transmissions measurements at ground level for all regions of the greenhouse.Objective 4: Field testing of power. Deliverable 4 Outdoor panel efficiency will be measured and demonstrated to be greater than 8% for a period of at least 6 months with no degradation.Objective 5: Crop performance Soliculture will work with Michael Loik at the University of California at Santa Cruz, David Blume with Whiskey Hill Farms and local berry growers to design crop experiments as discussed in the methods secion. Deliverable 5: Equivalent or improved crop yields under the solar panels relative to a zone with clear plastic covering.

Project Methods
Objective 1: UV stability of stack.Standard solar industry encapsulants and vacuum lamination methods are used for panel assembly. Results from the literature on similar stacks have shown excellent durability. Experiments will be performed using in-house UV Highly Accelerated Stress Test (HAST) equipment with a high intensity UV light and high temperatures to quantify UV degradation. The HAST chamber uses a metal halide lamp with roughly 4x the UV-A intensity of the sun. Samples will be aged 24/7 at elevated temperatures in the chamber. The key failure mechanisms due to UV aging of polymer films is cracking and embrittlement as measured by % elongation. The time to failure will be determined when cracks form or when % elongation drops below 50%. Objective 2: Mechanical stability of panel and mounting method.The semi-rigid panels and test frame will be subjected to a series of mechanical stress tests that includes static loads and dynamic loads that simulate winds of >100MPH. Static wind load will be tested using sand bags to apply static pressure in excess to 100MPH winds. Flexing and vibration of the panels can crack the embedded silicon solar cells and lead to power degradation. PV Evolutions Lab is in the business of testing and certifying solar panels. This company has equipment to test apparatus to vibrate the solar panels and simulate dynamic wind loads. Soliculture will work with the experienced team at this commercial laboratory toObjective 3: Installation in test greenhouse. The target cell coverage will be ~50% for high light regions such as California and Arizona. Each module is 1m x 2m and has an output of ~140W for a system efficiency of 7%, roughly half that of an array with conventional opaque panels. The existing Soliculture research greenhouse at Whiskey Hill farms will be the site for field tests. The existing gable roof will be replaced with a curved arc style roof for mounting the panels to simulate a hoop house. The width is 25' and the length is 100'. Panels will be mounted to the south facing roof only and a conventional PE film installed on the north roof. The greenhouse company Quiedan will assist with replacing the gable roof with a curved roof identical to that used in a hoop house. The semi-rigid panel mounting system developed by Soliculture greatly simplifies mounting the panels using high tension wire and wiggle wire channel. The panels will need to cover at least 30' of greenhouse length to create a uniform growing area for testing that is not impacted by the movement of shadows. Full spectral transmission of the panels will be measured in the lab before installation. Full spectral transmission will also be measured at ground level in the different greenhouse zones throughout a 12 hour period on a clear and cloudy day to capture diffuse light contributions and shading from the greenhouse structure. Previous tests have shown that diffuse light from the PE film in the north side of the greenhouse gives a substantial increase in light under the panels.Objective 5: Crop performance Soliculture will work with Michael Loik at the University of California at Santa Cruz, David Blume with Whiskey Hill Farms and local berry growers to design crop experiments. The greenhouse will be starting with bear dirt after installation of the new roof so full season growth data will not be available. The main focus will be on berries grown in pots. Berry growing in a hoop house is very common in this part of California and an increasing number of growers are starting to grow in pots where plants can be moved to a cooler in winter. The local nursery (California Tropical Fruit Tree) has a variety of mature berry plants in 15 gal. pots that can be used for this trial. The nursery recommends blueberries, blackberries and raspberries for this project. Final crop selection will depend on the time of year when 'funding becomes available. 24 plants / cultivar will be used for the tests. The berry plants will be set in a square grid in the different zones of the hoop house extending both east/west and north/south. Different cultivars will all be combined in one grid. Measurements of fruit production, photosynthesis response and chlorophyll levels will be recorded throughout the trial period.Leaf dry weight will be recorded when the plants are pruned for the winter. Environmental conditions and light levels will also be recorded throughout the trial period.