Skip to main content

Loading Events

« All Events

  • This event has passed.

ORaCEL Seminar – Eshwar Ravishankar

October 1, 2018 | 11:00 am - 12:00 pm

Title: Modeling Photocurrent and Transmittance of Semi-transparent Photovoltaic Devices for Greenhouse Integration

Abstract: Organic photovoltaics (OPVs) are an emerging solar power technology which uses a thin active layer of an organic semiconductor blend for its absorption. The active layer of OPVs are semi-transparent and by tuning the molecular structure, its absorption spectrum can be varied. With organic solar cell efficiencies now over 14%, this technology is becoming increasingly attractive for commercial implementation towards satisfying energy demand. One such application currently being explored are in greenhouses. Greenhouse crop production is employed across the globe in diverse climates to extend annual crop production and to provide a protected environment to enable cultivation of crops in demand outside of their natural growing seasons. This increases the annual yield of the crop and provides a stable source of food production across seasons. However, maintaining a climate desirable for plant growth incurs an energy demand greater than conventional farming. Integrating conventional silicon-based solar cells, while successful in offsetting this energy demand, completely cuts out light essential for plant growth thereby causing a drop in production. It is here that organic solar cells provide an opportunity for rooftop greenhouse integration. It is envisioned that the spectral absorption characteristics of the solar cell can be tuned by selecting a suitable active layer to complement the spectral demand for plant growth while generating energy to offset the demands of the greenhouse structure. A detailed analysis involves assessing the efficiency and transmittance of potential semi-transparent OPV devices which in turn impacts the ease of energy offset and light entering the greenhouse for the plants to utilize respectively. Modeling is done using a transfer matrix model. Inputs for the model include the complex refractive index, the thickness of each layer of an OPV and hourly angle of incidence of light while the transmittance and absorptance of light in each layer form the output. Absorptance in the active layer is used to find the short-circuit current which in turn is utilized to compute the annual power generation from the OPVs. One of the major parameters to assess the success of OPV integration to greenhouses is the percentage of energy offset in greenhouses. Hence, an energy model is designed and integrated with the transfer matrix model to compute the total heating and cooling demand for the greenhouse. An energy feasibility assessment is performed by modeling a greenhouse in three diverse locations like Phoenix, Arizona (hot and dry), Raleigh, North Carolina (hot and humid) and Antigo, Wisconsin (cold and humid). Two semi-transparent OPV devices are used in each of these locations with a 100 nm thick P3HT:PCBM and FTAZ:ITM active layer device with nominal efficiencies of 3.5 and 12 percent respectively. Comparing net energy demand to power generation at 12 percent efficiency, there are surplus power generation in Arizona and North Carolina locations indicating a net zero energy greenhouse and hence providing a lot of promise for further research in this area. With further optimization, it is very likely energy-wise that system operation and cost for OPV integrated greenhouses can become very attractive.


October 1, 2018
11:00 am - 12:00 pm
Event Category: