The mechanisms underlying the wavelength dependence of the quantum yield for CO 2 fixation (a) and its acclimation to the growth-light spectrum are quantitatively addressed, combining in vivo physiological and in vitro molecular methods. Cucumber (Cucumis sativus) was grown under an artificial sunlight spectrum, shade light spectrum, and blue light, and the quantum yield for photosystem I (PSI) and photosystem II (PSII) electron transport and a were simultaneously measured in vivo at 20 different wavelengths. The wavelength dependence of the photosystem excitation balance was calculated from both these in vivo data and in vitro from the photosystem composition and spectroscopic properties. Measuring wavelengths overexciting PSI produced a higher a for leaves grown under the shade light spectrum (i.e., PSI light), whereas wavelengths overexciting PSII produced a higher a for the sun and blue leaves. The shade spectrum produced the lowest PSI:PSII ratio. The photosystem excitation balance calculated from both in vivo and in vitro data was substantially similar and was shown to determine a at those wavelengths where absorption by carotenoids and nonphotosynthetic pigments is insignificant (i.e., >580 nm). We show quantitatively that leaves acclimate their photosystem composition to their growth light spectrum and how this changes the wavelength dependence of the photosystem excitation balance and quantum yield for CO2 fixation. This also proves that combining different wavelengths can enhance quantum yields substantially.

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Photosynthetic Quantum Yield Dynamics: From Photosystems to Leaves

Energy is the largest overhead cost in the production of agricultural greenhouse crops in temperate climates. Moreover, the initial cost of fossil fuels and traditional energy are dramatically increasing. The negative environmental impacts, limited sources of fossil fuels and a high consumption of energy and food have caused the increase in demand for solar energy as a green and sustainable choice. Therefore, this paper reviews the solar energy application technologies in the environmental control systems of greenhouses (cooling, heating and lighting) mainly the generated energy of photovoltaic (PV) and solar collectors, as well as the PV water pumping for irrigation. Furthermore, this paper briefly discusses the economic analyses and the challenges for this technology.

Advanced applications of solar energy in agricultural greenhouses

In this study, a comprehensive review focusing on key strategies of energy saving and climate control technologies for greenhouses is presented. Following the brief and concise assessment of existing greenhouse systems in terms of their role in total energy consumption; cost-effective, energy-efficient and environmentally friendly technologies are analyzed in detail for potential utilization in greenhouses for notable reductions in energy consumption and emission levels. The technologies considered within the scope of this research are mainly renewable and sustainable based solutions such as photovoltaic (PV) modules, solar thermal (T) collectors, hybrid PV/T collectors and systems, phase change material (PCM) and underground based heat storage techniques, energy-efficient heat pumps, alternative facade materials for better thermal insulation and power generation (heat insulation solar glass, PV glazing, aerogel and vacuum insulation panel, polycarbonate sandwich panels), innovative ventilation technologies using pre-heating and cooling (high performance windcatchers) and efficient lighting systems. The findings from the research clearly reveal that up to 80% energy saving can be achieved through appropriate retrofit of conventional greenhouses with a payback period of 4–8 years depending on climatic conditions and crop type.

Renewable and sustainable energy saving strategies for greenhouse systems: A comprehensive review

Organic photovoltaics are an emerging solar power technology which embody properties such as transparency, flexibility, and rapid, roll to roll manufacture, opening the potential for unique niche applications. We report a detailed techno-economic analysis of one such application, namely the photovoltaic greenhouse, and discuss whether the unique properties of the technology can provide advantages over conventional photovoltaics. The potential for spectral selectivity through the choice of OPV materials is evaluated for the case of a photovoltaic greenhouse. The action spectrum of typical greenhouse crops is used to determine the impact on crop growth of blocking different spectral ranges from the crops. Transfer matrix optical modelling is used to assess the efficiency and spectrally resolved transparency of a variety of commercially available semi-conducting polymer materials, in addition to a non-commercial low-band-gap material with absorption outside that required for crop growth. Economic analysis suggests there could be a huge potential for OPV greenhouses if aggressive cost targets can be met. Technical analysis shows that semi-transparent OPV devices may struggle to perform better than opaque crystalline silicon with partial coverage, however, OPV devices using the low-band-gap material PMDPP3T, as well as a high efficiency mid-band-gap polymer PCDTBT, can demonstrate improved performance in comparison to opaque, flexible thin-film modules such as CIGS. These results stress the importance of developing new, highly transparent electrode and interlayer materials, along with high efficiency active layers, if the full potential of this application is going to be realised.

Organic photovoltaic greenhouses: a unique application for semi-transparent PV?

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ese3.239

Solar power technology for electricity generation: A critical review

Performance of a concentrated photovoltaic energy system with static linear Fresnel lenses

Performance results of a solar greenhouse combining electrical and thermal energy production.

Feasibility study for combining cooling and high grade energy production in a solar greenhouse

The scope of this paper is a new greenhouse design that incorporates both a filter for rejecting near infrared radiation (NIR) and a solar cooling system. Cooled greenhouses are an important issue for the combination of high global radiation and high outdoor temperatures. As a first measure, this study prevents heat entering the greenhouse by applying a NIR-reflective cover material. The special spectral selective properties of these materials will block up to 50% of the outside solar energy from entering the greenhouse, which will reduce the cooling capacity required. The second measure is the introduction of a solar driven cooling system. When the NIR reflecting coating is designed as a parabolic or circular shaped reflector integrated in the greenhouse, the reflected solar energy received by a PV cell at the focus delivers sufficient electric energy to drive a fan and pad cooling system. The excess energy can be used for desalination and/or energy supply. Parameters related to typical climate conditions and energy flows are presented.

Piet Sonneveld

Papers

Performance of a concentrated photovoltaic energy system with static linear Fresnel lenses

Performance results of a solar greenhouse combining electrical and thermal energy production.

Feasibility study for combining cooling and high grade energy production in a solar greenhouse

Greenhouse with an Integrated NIR Filter and a Solar Cooling System

Improvement of greenhouse insulation with restricted transmission loss through zigzag covering material