Dual use of land for PV farms and agriculture literature review
Introduction[edit | edit source]
This literature review is for a project which involves using the same piece of land for setting up a PV farm and performing agriculture/livestock grazing on it. By doing this, the same piece of land can be used to generate electricity and food crops, thus, increasing land use. This setup can prove to be a as it would not only be a steady source of income for farmers but also allow a small area in the vicinity of the PV farm to become self sustaining in terms of electricity.
Initially, this topic would cover the growth of lettuce on a farm having PV panels mounted and the influence of PV panels on the growth pattern of lettuce.
This literature review supported this review article:
- Harshavardhan Dinesh, Joshua M. Pearce, The potential of agrivoltaic systems, Renewable and Sustainable Energy Reviews, 54, 299-308 (2016). DOI:10.1016/j.rser.2015.10.024, open access
This focused article on grape farm potential:
- Prannay R. Malu, Utkarsh S. Sharma, Joshua M. Pearce. Agrivoltaic potential on grape farms in India. Sustainable Energy Technologies and Assessments 23, pp. 104-110, 2017. doi: 10.1016/j.seta.2017.08.004 open access
This article discussing the views of farmers on agrivoltaics:
- Pascaris, A.S.; Schelly, C.; Pearce, J.M. A First Investigation of Agriculture Sector Perspectives on the Opportunities and Barriers for Agrivoltaics. Agronomy 2020, 10, 1885. https://doi.org/10.3390/agronomy10121885 open access
and the views of solar photovoltaic industry persceptives on agrivoltaics:
- Alexis S. Pascaris, Chelsea Schelly, Laurie Burnham, Joshua M.Pearce. Integrating solar energy with agriculture: Industry perspectives on the market, community, and socio-political dimensions of agrivoltaics Energy Research & Social Science 75, (2021), 102023. https://doi.org/10.1016/j.erss.2021.102023 open access
Literature Review Page for "Dual Use of Land for PV farms and agriculture literature review"[edit | edit source]
Selected Papers and Literature[edit | edit source]
Combining solar photovoltaic panels and food crops for optimising land use: Towards new agrivoltaic schemes [edit | edit source]
Extracting fuel from biomass was put forth as an alternative energy source to dwindling fossil fuel resources. However, this would involve the widespread use of food crops for producing biomass resulting in food shortages as the existing cultivable land on the planet cannot cope with the demand for crops used for food and biomass at the same time. A solution to this problem is an 'Agrivoltaic' system i.e. a combination of PV panels set up on an existing farmland, thus increasing land use. Simulations have shown an increase in land productivity by 60-70%.
- Optimized solar panel orientation is determined by PVsyst software to ensure maximum amount of radiation is tapped by the panels.
- Panels are mounted at a certain height over the crops to allow mechanical farming equipment to underneath the panels.
- Difficult to predict the behavior of crops under the shaded area of the PV panel.
- Experiments have shown that electricity and crop yield of a 100 hectare farm with an agrovoltaic system in place is greater than a 170 hectare farm having separate production.
Productivity and radiation use efficiency of lettuces grown in the partial shade of photovoltaic panels. European Journal of Agronomy[edit | edit source]
Abstract: Converting crop lands into PV farms would aggravate the competition for land between food and energy production. Setting up PV panels on top of crop farms shades a part of the crops. In spite of the shading effect, lettuce yields were higher by improving the Radiation Interception Efficiency. The effect of the shade on the lettuce plantation was a reduction in the number of leaves but and increase in the leaf area. This was the adaptation bought about by lettuce to thrive in the shade. A framework is defined based on the adaptive characteristics of crops that thrive in the shade to optimize agrovoltaic systems.
- Lettuce has the ability to adapt to lower light conditions by increasing its capability to harvest light.
- Similar experiments were done using cucumber, french beans and durum wheat to study the effect of crop rotation on an agrivoltaic system.
- Agrovoltaic systems can be optimized by plant breeding and making adjustments to PV panels to find the best way to co-produce electricity and food on the same piece of land.
- Report released by the BRE and National Solar Center of UK stating that PV farms can be set up on lands reserved for livestock grazing.
- PV farms gives the farmers an economic boost and at the same time does not affect his existing farming practices.
- The farmer does not need to cut down on the number of grazing animals nor does he have to adjust the grazing frequency of livestock as 95% of the grazing land is unaffected by the PV panels.
- A PV farm with an output of 4.2 MW was set up in Axminster, Devon, UK. This farm provides electricity as well as fodder for livestock.
To mix or not to mix: evidences for the unexpected high productivity of new complex agrivoltaic and agroforestry systems[edit | edit source]
Abstract: Agrivoltaic schemes are profitable, environment friendly and have high levels of production. These schemes have higher volumes of production due to higher land equivalent ratios. Land equivalent ratio(LER) determines the efficacy of a piece of land. It is calculated by the relative yields of the components on the piece of land in question. LER for an agrovoltaic(AV) systerm was the sum of the relative yield of the crop and the relative yield of electricity by the PV panels.
- LER for a 100 hectare AV farm was in the 1.3-1.6 range. Methods to optimize LER were suggested like having a North-South orientation for the crops.
- PV panels provide constant shading over crops which affect winter crops more as compared to summer crops due to the sunlight demands of such crops. However, the PV panels acts as a protective measure for the crops in the summer from excessive heat and evaporation.
- More research is needed on the PV panel density depending on the light demands of various crops.
Assessing the land equivalent ratio (LER) of two corn varieties intercropping at various nitrogen levels in Karaj, Iran.[edit | edit source]
LER is the ratio of yield of the individual crop in the intercropped land to the yield of each crop in a monocropped land. LER value of 1.0 indicates the same yield from an intercropped and monocropped land. If LER>1.0 indicates a higher yield from the intercropped land and if LER<1.0, the yield of the monocropped land is higher than that of the intercropped land.
- Experiment was conducted to study the effect of two different varieties of corn on land use efficiency with different nitrogen levels
- LER's for an intercropped land was observed to be 1.066.
- At different levels of nitrogen content in the soil, LER's were always greater than zero.
How does a shelter of solar panels influence water flows in a soil–crop system?[edit | edit source]
Crops can achieve a higher yield under the fluctuating sunlight of an Agrovoltaic system. Under dry climatic conditions, the climatic conditions below the PV panels suggest that the PV panels help in alleviating the water demand by the crops. Water use efficiency can be increased by selecting crops with a rapid soil covering which contributes to a higher amount of light being captured with decreased soil evaporation.
- Shading due to the PV panels resulted in water savings by 14-29% depending on the level of shading.
- Water demand reduction was achieved by reduction in incident radiation due to the shading effect.
- Water use efficiency was found to increase for some varieties of lettuce in the shade
Tradeoffs and Synergies between Biofuel Production and Large Solar Infrastructure in Deserts[edit | edit source]
Abstract: The paper discusses the setting up of agrivoltaic schemes in arid regions with limited water resources. It discusses about the use of land between panels for growing biofuel plants like Agave which can thrive in dry and arid climate thanks to its water efficient photosynthesis process. Monte Carlo Approach is adopted to measure the uncertainty amongst the various parameters such as variations in the number of solar modules /ha, module efficiency, overall sugar conversion efficiency for agave and number of agave plants /ha. The limited water resources can be used to clean the PV panels as well as watering the plants by directing the water onto the PV panels which would drain off on the agave plants resulting in efficient usage of limited resources. The Agave plants are used in the production of ethanol fuel.
- Revenues from the solar PV per unit of water used was 100 times greater than that of traditional crops. Combination of solar PV and agave resulted in the highest returns per cubic meter of water used.
- Competition for land for growing biofuel and food crops is reduced and the agave crops can help in reduction of dust collection on the PV panels.
Abstract: Renewable energy schemes such as PV farms require large tracts of land to capture sunlight and produce electricity in large quantities. Ideally, the best place to set up PV farms is on barren land. However, if barren land is not available, PV farms have to be set up on cultivable land used for growing food/cash crops. The land required for energy and food production depends on the demand and supply of that particular area. This paper discusses biomass as a short term renewable energy source and the long term potential of solar energy and their effects on limited land resources.
- The food and electricity yield figures obtained are very sensitive to the changes in the estimated input parameters with respect to land requirements.
- Two scenarios are considered i.e. rich and poor. In the poor scenario, land requirements fall short when biomass is used as an energy source. In the rich scenario, land requirements for food and energy production are satisfied.
- Widespread changes are to be incorporated into the existing energy infrastructure to accommodate solar PV systems such as storage batteries that store the energy from the PV panels for use at night or during low light periods.
What is the maximum efficiency with which photosynthesis can convert solar energy into biomass?[edit | edit source]
Abstract: This paper examines the efficiency of the photosynthesis process at each step in the conversion of solar radiation into biomass and to understand the factors that limit this efficiency. The efficiency of photosynthesis ranges 4.6% to 6%.
- Plants can tap solar radiation between 400-740 nm which is about 48% of the incident solar radiation on Earth.
- Reasons for losses in the photosynthesis process include reflection and transmission of solar radiation, photochemical process inefficiency, inability of plants to tap solar radiation wavelengths less than 400nm and greater than 740nm, losses due to photo-respiration.
- Photosynthesis efficiency can be improved by overcoming the photo respiration losses which is the one of the main limiting factors.
Determination of the optimal tilt angle and orientation for solar photovoltaic arrays[edit | edit source]
Abstract: The optimum tilt angle of a PV panel can be determined by maximizing the incident solar radiation on the panel subject to minimization of the variance in the power output. The most accurate solar irradiance figures can be selected from existing data for several PV models. A database is then prepared using the existing data for different tilt angles over different periods of time. Meta-models are produced to co-relate the tilt angle with the solar radiations at different times of the day using the data from the database. An optimization problem is then formulated with an objective to maximize solar irradiation on the panel.
Output energy of a photovoltaic module mounted on a single-axis tracking system[edit | edit source]
Abstract: This paper deals with the power output of a PV panel installed in Taiwan at different azimuth's and tilt angles. The gain of a single axis mounted panel was compared with that of a traditionally mounted panel. Simulation results show that the optimal tilt angle for observed radiation is flatter than that from extraterrestrial and global radiation.
- Yearly gains from extraterrestrial, global and observed radiation is 51.4%, 28.5%, 18.7% for a module installed at the yearly optimal tilt angle for over a year. Similarly, the gains for a PV panel mounted at the monthly optimal tilt angle are 45.3%, 25.9% and 17.5% respectively.
- Conversion efficiency of the PV panel mounted at the yearly optimal angle is 10.2%, 9.2% and 8.3% for extraterrestrial, global and observed solar irradiation.
- The panels can be mounted either at the optimal yearly tilt angle and changed yearly or at the monthly optimal tilt angle which would be changed on a monthly basis.
Abstract: This paper proposes a method to reconfiguration scheme to reduce the effect of shading on the PV panels. In this method, a smaller reconfigurable adaptive PV bank is connected to a larger fixed PV bank and the maximum power point(MPP) can be tracked with a single MPP tracker. During non-uniform illumination periods, the number of adaptive solar cells connected to the shaded modules depends on the area of shading. A control algorithm is designed to open and close the switches linking the adaptive and the fixed PV modules. The adaptive reconfiguration is bought about by a switching matrix defined in the control algorithm.
- A matrix of switches is used to connect an adaptive PV array to a larger fixed array with an objective to maximize output power in case of non-uniform illumination.
- An experimental prototype was built and was used to test said algorithms.
- This configuration is aimed at avoiding the local MPP of each module and focus on the central MPP of the entire array to maximize power output.
Abstract: The power output of a PV system depends on its nominal power, incoming solar radiation and the losses in the system. It also depends on the other factors such as response to low light response, temperature of modules, light spectrum range, deviation from MPP etc. The paper compares theoretical calculations with actual experiments conducted on the field.
- Theoretical calculations compared with experimental data obtained from PV farms set up at Nicosia, Cyprus and Heraklion, Greece
- Reduction in power output is due to excess photon concentration caused by overheating cells.
- Part of the experimental data used was involving PV modules made of multicrystalline modules having stable performance characteristics. For example, amorphous Silicon initially have a higher power output, but the output drops after a few months of use.
Abstract: The growth of lettuce under different light and temperature conditions was examined with special emphasis on the head of the lettuce. The number of leaves increased as light intensity and temperature increased. Leaf length and width depend on the environmental conditions i.e high light intensity can cause changes in the width of the leaves. The light intensity in turn is responsible for the temperature effect on the leaves. Similarly, variations in the leaf length are more prevalent at low light intensities i.e they elongate faster at lower light intensities. In contrast, light intensity affects the growth rate and duration of the leaf width which are reduced greatly at low light intensities.
Are species shade and drought tolerance reflected in leaf‐level structural and functional differentiation in Northern Hemisphere temperate woody flora?[edit | edit source]
Abstract: This paper explores the shade and drought tolerances of the leaves of woody species of fauna found in the Northern Hemisphere. A consolidated database was prepared combining the information regarding leaf traits and species tolerances.
- Plant species with higher drought tolerance were resource conserving species with low nitrogen and photosynthetic capacity, longer life span and higher dry leaf mass.
- Variation in shade tolerance amongst species did not significantly affect the life of the plant.
- The shade tolerance of the plant depends upon the type of foliage and also suggests a corelation between the leaf structure and the plant's tolerance to environmental conditions.
- The ability of plant species to develop tolerance against both, drought and shade is an inherent limitation of the plant species in question.
Abstract: This paper attempts to develop an approach relating efficiences of dry matter production to factors that determine growth rates. Tropical fauna examples were used to develop this approach.
- Solar energy storage efficiency is expressed as a product of factors describing the dependence of dry matter production, seasonal variation etc.
- The limitations used to predict crop growth rates are ignorance about the decrease of leaf diffusion resistance, ignorance about the relation between respiration rates and rate of photosynthesis etc.
- Another limitation for tropical fauna models is the need to do measurements instead of predictions.
Different methods for separating diffuse and direct components of solar radiation and their application in crop growth models[edit | edit source]
Abstract: This paper discusses the effect of diffused solar radiation on the dry matter production of leaves under different climatic conditions. Daily and hourly values of incoming direct and diffuse radiation are compared for incorporation into the simulation of wheat growth models.
- By comparison, accuracy of direct and diffuse components of solar radiation varies with changes in climatic conditions.
- Final yield calculation results are influenced by the methods used to calculate the incoming radiation.
- Small errors in calculating solar irradiation affects the final yield figures.
Abstract: Dwindling fossil fuel resources have pushed up biofuel production levels significantly over the past 10 years and there has been an impetus towards the intensification towards biofuel use. The life cycle analysis helps in understanding the environmental impacts of biofuel production, land requirements and its impacts on food production. Certain protocols have to be established regarding the social impacts of the biofuel production chain.
- In a nutshell, biofuel production and its supporting social and economic factors depend on the development scale of each country.
- Biofuel cannot be called as a long term replacement for fossil fuels. It can only act as an intermediate solution.
- Technological development will allow the transition from simple biofuels like bioethanol, biodiesel to cellulosic ethanol, methanol and bio-hydrogen which would alleviate the impact on food production while using large amounts of raw materials at the same time.
- The by-product obtained from ethanol production from sugarcane bagasse can be used as fodder for livestock, thus benefiting the livestock industry which in turn would reduce the burden on grazing lands and pastures.
- Regulatory framework imposes limits on land use and also to improve and safeguard the conditions of personnel involved in the biofuel production industry.
Semi-transparent PV: Thermal performance, power generation, daylight modelling and energy saving potential in a residential application[edit | edit source]
Abstract: This paper proposes the use of semi-transparent PV panels for residential applications. The characteristics of semi-transparent PV panels are obtained from field tests which give vital information regarding power output, thermal characteristics etc. Semi-transparent PV panels can also be used for daylighting indoor areas, but the saving from this is not very significant as indoor electricity demands are mostly during nights.
- A semi-transparent PV panel with 50% transmission capacity produces a 5.3% reduction in the heating and cooling energy as compared to a normal PV panel.
- Net energy savings in terms of total energy consumed would be in the range of 3-8.7% by a semi-transparent PV panel.
- The inner and outer temperatures of the semi-transparent PV panel were measured during summer and winter seasons. Outside temperatures ranged from 35-75oC in winter and summer respectively. Similarly, inner temperatures ranged from 30-40oC in the summer.
- In terms of power generation by the PV, the paper assumes poly-crystalline Silicon whose power generation capacity deteriorates after a few months.
- Optimization of PV panels corresponding to the climate and building characteristics contribute to further savings.
Operating temperature of photovoltaic modules: A survey of pertinent correlations[edit | edit source]
Abstract: This paper discusses the operating temperature for the best performance of PV panels.
- The temperature of a PV panel can be co-related to factors such as ambient temperature, wind speed, solar radiation.
- With respect to the weather, temperature rise of the PV cell is sensitive to wind speed changes and practically independent of atmospheric temperature.
- Temperature of the PV cell depends strongly on the solar radiation on the PV module.
Light distribution, photosynthetic rate and yield in a Paulownia-wheat intercropping system in China[edit | edit source]
Abstract: This paper discusses the effect of shading in a Paulownia-wheat intercropped system and its effect on the wheat yields. Factors such as photosynthetically active radiation(PAR), leaf photosynthesis, canopy leaf area index were measured to study the effects of shading on the wheat yields.
- Shading reduced the PAR by 22%, 44% and 56% during the flowering, grain filling and maturing stage.
- The amount of PAR intercepted in an intercropped system is less than that in a mono cropped system which in turn reduced the number of grains and the grain dry matter.
- Wheat yields in the intercropped system was less by 51% than that in the mono cropped system.
Abstract: STICS was a model developed by INRA in 1996. The model simulates crop growth, water balance and nitrogen balance in the soil with respect to the climatic data obtained on a daily basis. This paper discusses the STICS model concerning interractions between the soil and roots and the relation between crop management and the soil-crop system. In addition to this, specific crop species related data is provided by the experts in this field. The paper also discusses the limitations of this model
- STICS relies on well established data rather than untested assumptions.
- Adaptability to different crops.
- Professionals from various related fields can equally contribute to this model, thus evolving as more and more data is provided, making this model grow.
Partitioning solar radiation into direct and diffuse, visible and near-infrared components[edit | edit source]
Abstract: The diffuse and visible component of solar radiation were measured during the summer of 1979, 1980 and 1981. The objective was to predict the behavior of direct and diffuse radiation in the visible and infra-red spectrums with the input being the total incoming solar radiation.
- Direct component estimates for the visible and infrared spectrum were made from the experimental data and the predicted and calculated values reconciled.
- A correction term for the measurement of the diffuse component was formulated with the help of a Silicon cell pyranometer.
Which plant traits promote growth in the low-light regimes of vegetation gaps?[edit | edit source]
Abstract: An experiment was conducted on 9 types of grass species to assess their ability to grow in low light conditions. To simulate this ability, photon flux densities similar to shaded sunlight were simulated and the relative and absolute growth rates were determined keeping in mind different ecological plant attributes. It was deduced that there was no relation between some of the plant attributes and the relative growth rate.
- Species with low root mass and high net photosynthetic rates are able to grow faster in low light conditions(also in shade).
- Nitrogen content in the leaves with respect to the mass and area were not related to the growth.
Abstract: The term radiation use efficiency(RUE) is defined as the ratio of the biomass accumulated to the total solar radiation intercepted. The RUE is not significantly affected in case of diffused light or shade. High values of RUE were reported for plant species in cases where the diffused radiation component is higher in the total incident solar radiation. The paper discusses the changes in the RUE with respect to changes in the diffuse radiation component.
- RUE estimates for soyabean and wheat increased as diffuse radiation increased.
- Therefore, it can be deduced that RUE is directly proportional to the diffuse radiation component of the total incident radiation.
Light-dependent changes in biomass allocation and their importance for growth of rain forest tree species.[edit | edit source]
Abstract: This paper discusses an experiment which studied the growth of rain forest tree specimens and their response to shading. The leaves of the saplings were measured from its production to death. Low light conditions such as shading causes the leaves to increase their light interception ability by increasing their leaf area per unit plant mass. Shaded leaves have lower respiration rates.
- 17% of the saplings had negative growth rates i.e their growth rates were lesser than those saplings exposed to direct sunlight.
- Shading caused 7 of the 91 saplings to die.
- Height of the saplings is directly proportional to the light conditions, leaf area or both.
- Changes in light affect the biomass allocation in the sapling but has no relation to the shade tolerance of the plant as a whole.
Abstract: This paper discusses measures on overcoming the problem of dust collecting on the surfaces of the PV panels. The experimental setup consisted of 100 glass panels mounted at different tilt angles. The transmittance of the glass was checked at regular intervals and no physical cleaning was performed on the glass panels. They were exposed to all kinds of weather conditions.
- Dust deposition density depends on the tilt angle and the panel orientation with respect to the wind.
- Deposition density goes from 15.84 gm/cm2 at angle of 0o to 4.48 gm/cm2 at angle 90o.
- Transmittance of the glass panel reduces from 52.54-12.38% as dust collects on the surface.
A new correlation for direct beam solar radiation received by photovoltaic panel with sand dust accumulated on its surface[edit | edit source]
Abstract: This paper discusses the effect of sand collecting on the surface of PV panels. The amount of light transmitted through an uncleaned glass surface was compared to the light transmittance of clean glass which is about 90%. The transmittance reduced by 8% on an average for a tilt angle of 45o. A transmission co-efficient was formulated. In the context of sand collection on the surface of the transmittance co-efficient can be defined with respect to number of sand particles per unit area of the glazing surface, sand particle size and incident wavelength. Results from this experiment will allow designers to factor the effect of sand while developing simulation models of PV panels.
- Dust(Sand in this context) deposition density depends on the tilt angle and the panel orientation with respect to the wind.
- Sayigh performed an experiment in the Saudi Arabia desert and found a drop of 30% in the collected energy when the panel was not cleaned for a span of 25 days. The panels had a tilt angle of 30o.
- Similar experiments performed in different desert regions of the world showed similar results to Sayigh's experiment.
- A sand dust box was built to determine the amount of sand collected on the glass top over a period of time. The quantity of collected sand would help in finding out the effect of sand on the transmittance co-efficient.
Abstract: This article discusses about an experiment which involved setting up PV panels to power the climate control equipment for a Welsh greenhouse growing onion. The panel was mounted on the south facing side of the greenhouse which was constructed having an East-West orientation and the shading effect caused by the installed panel was assessed. The PV panels were mounted in 2 different configurations i.e straight line and checkered. In addition to the greenhouse with a PV array mounted, a second greenhouse was also constructed, but had no PV array installed in it. Onion was cultivated in both the greenhouses and the yields from the two greenhouses were compared to ascertain the effect of shading on the growth of onion.
- Shading significantly affected the fresh and dry weights of the onion when compared to the onion yield from the second greenhouse.
- PV arrays occupied 12.9% of the total available roof area of the greenhouse.
- The onion crop growing at different positions of the greenhouse and the shading effect caused by the 2 different mounting configurations of the PV panels are studied and compared with each other and also with the onion growing in the second greenhouse.
- Cost of electricity for the PV panels when connected to the grid was EUR 0.263/kWh.
- It was concluded that the straight line configuration proved optimal for electricity production, but caused more shading affecting crop yields.
- Checkered configuration improved crop yields but wasn't so good on the electricity production front.
Temperature gradients in a partially shaded large greenhouse equipped with evaporative cooling pads[edit | edit source]
Abstract: This paper proposes a model which predicts temperature gradients within a greenhouse caused due to the cooling pads. This model incorporates the effect of shading, ventilation and crop transpiration. The temperature gradients are set up due to the cooling pads which can affect plant growth. Experimental results showed that for a 60m long greenhouse, temperature gradients of 8oC were observed. The proposed model was used to study the effects of different ventilation rates combined with shading along the length of the greenhouse and also the effect of conditions outside the greenhouse on the cooling systems of the greenhouse.
- The proposed model is calibrated based on existing data available data from greenhouses.
- Simulations propose that fans and cooling systems can help reduce the temperature gradients by shading and fan ramping up the ventilation rates.
- This model can be used as an effective tool to calculate the optimum temperature within the greenhouse such that plant growth is not affected due to shading and temperature gradients.
Stomatal behavior and photosynthetic performance under dynamic light regimes in a seasonally dry tropical rain forest[edit | edit source]
Abstract: The photosynthesis rates of leaves of tropical shrubs were measured in sunlight and darkness. The behavior of the stomata was then observed during the bright period and the dark period and its effect on the photosynthesis rates of tropical plant species. Photosynthetic behavior of plants, especially in the dry season is also dependent on the water availability scenario wherein the plant can reduce its photosynthetic performance in case of water shortage. To quantify the effect of seasonal changes on the photosynthesis process, the carbon gain under different light conditions was simulated using the model described by Pearcy et.al 1997.
- Stomatal conductance is higher during wet season dawns prior to sunrise(increase in photon flux density) but during the afternoon stomatal conductance was less.
- Stomatal conductance was relatively higher in the wet season as compared to the dry season.
Efficiency model for photovoltaic modules and demonstration of its application to energy yield estimation[edit | edit source]
Abstract: This paper discusses a method to calculate the yield of a PV module at various sites with the help of the available local weather data. This would make it easier to select the optimum PV module having the highest yield to cost ratio ensuring maximum revenue from the PV modules taking into considerations factors such as incident radiation, PV cell temperature and relative air mass. The paper presents the yields from the modules made of monocrystalline, polycrystalline, amorhphous silicon etc. set up at a location in Jordan.
- The Wuerth CIS module has the highest yield as its efficiency is independent of the cell temperature.
- Efficiencies of the modules were in the 8-16% range at an ambient temperature of 25oC.
- This model is an effective in calculating the yield of a PV module mounted in any part of the world with the help of the local weather and sunlight data.
Abstract: This paper discusses the development of a transparent shield to protect the PV panels. The transparent shield contain embedded electronics hooked up to a single phase AC supply. When a particle of dust comes into contact with this shield, it gets charged and gets repelled by the electromagnetic field. The paper also discusses the factors determining the performance of the shield and also the self cleaning process of this shield. Charged dust particles glide over the surface of the shield in the direction of the electromagnetic field towards the end of the transparent shield, thus clearing the surface of dust.
- The panel developed had line shaped electrodes etched onto the board shaped shield. Applied voltage ranged from 0 to 10kV and frequency from 0 to 300Hz.
- 0.03" thick electrodes were spaced at a distance of 0.06" on the board. Such a configuration was selected to ascertain the cleaning effectiveness of the electrodes on the surface of the shield.
- A clearing factor was defined which is the ratio of the dust removed to the dust settling on the panel.
- Experiments proved that pulsed wave signals were the best in eliminating dust from the PV panels.
The solar greenhouse: state of the art in energy saving and sustainable energy supply[edit | edit source]
Abstract: This paper discusses about a Dutch greenhouse which was used for agriculture without involving any fossil fuels. The challenge designing the greenhouse was to increase the heat insulation of the greenhouse and maintaining high light transmission. PV panels were set up to capture light energy during the summer months, store it and utilize the energy during the winter when incident light is less and days are shorter. The total energy saving was projected to be in the 60% range.
Abstract: This paper studies the effects of shading on the V-I characteristics of a PV panel which are used for the development of models which describes the circuits of the PV arrays. Power losses due to shading are due to two types of mechanisms viz. shaded cells in series with illuminated cells blocking current flow and shaded cells in parallel with illuminated cells shunting part of the current. The paper presents basic array models which are useful in designing larger complex arrays with complex circuitry. Three models are presented for partially shaded PV modules out of which one them provides accurate results but involves large data handling. The errors in these models cannot be predicted beforehand and have to be taken up on a case by case basis as local area data plays an important role in this.
Simple optimization procedure for silicon-based solar cell interconnection in a series–parallel PV module[edit | edit source]
Abstract: This paper discusses about the optimization procedure for series-parallel interconnected PV modules. The optimization problem aims to maximize electrical power output subject to constraints like V-I characteristics and power balance. PV modules optimized to function in warmer climates have a higher number of series connected modules with the length to width ratio being greater than 1 for higher latitudes and less than 1 for lower latitudes. Two methods of optimization were discussed; the first method covered the effect of the geographical location on the optimization and the second method discussed the effect of PV cell quality on the optimization process.
Abstract: This paper discusses the points taken into consideration before publishing a paper on a crop model. The background for publishing this paper was the lack of scientific innovation in previous papers which can be a path for a scientific breakthrough. The criteria to be met prior to publishing such papers are the objective statement, well defined framework and the evaluation of the scientific breakthrough presented in the paper by the publisher. Publishers usually refer to similar journals previously published as benchmarks. By following this criteria, the journals published will possess a high degree of authenticity and the facts published in the papers are thoroughly evaluated to ascertain their scientific validity.
Abstract: The paper presents the results of a 2 year long study to ascertain the effects of a direct covering over different types of crops. Crops such as Chinese cabbage, beet, lettuce, spinach were grown under the cover of a polypropylene fabric. As a result, air temperatures were higher underneath the cloth as compared to growing the aforementioned crops in the open. As the crops passed from the growth stage to the maturing stage, the air temperature difference between open air growing and growing under cover decreased. However, this did not affect the yields and it was observed that the crops grown under cover had a larger leaf area as compared to that of open air growing. In terms of the leafy vegetables such as cabbage, growing it under cover proved to be beneficial from an economic point of view as larger leaf sizes are a desired quality in such vegetables. Installation of the polypropylene fabric cover over the crops results in a reduction of the incident light on the crops by a factor of 85-65%.
Abstract: This paper questions the fact as to whether the low efficiency of the photosynthesis process is the limiting factor for biomass production. The paper suggests that instead of focusing on improving the efficiency of the photosynthesis process, it would be better to exploit the adaptive abilities of plants to lower light conditions as plants tend to increase their leaf areas in low/diffused light conditions so as to maintain the efficiency of the photosynthesis process.
Photovoltaic Greenhouses: Comparison of Optical and Thermal Behavior for Energy Savings[edit | edit source]
Abstract: This paper compares the behavior of tomatoes grown inside 2 types of greenhouses viz. a photovoltaic greenhouse and a normal glass greenhouse. Heating and cooling systems of the existing greenhouses depend on power supply from the grid which in turn comes from power plants running on coal/gas/nuclear etc. Also, other factors such as geographical factors such as temperature, altitude, humidity etc. can increase of decrease the electricity demand by the climate control systems within the greenhouse. The idea is to get the greenhouse air conditioning systems hooked onto a PV system, thus making the greenhouse self sustaining and reducing demand on the power grid.
- Internal radiation incident on the crops was much lesser than that in the glass greenhouse.
- Savings in energy consumption in the PV greenhouse ranged from approx 10-65% with higher amount of savings recorded in late spring and early fall periods.
- Average energy savings on cooling was 30% and 11% for heating in the PV greenhouse.
Abstract: Anti-reflective coatings can aggravate the collection of dust on the surfaces of the PV panels. This paper discusses a process called non-lithographic nanostructuring of the protective glass surface as a solution to the problem of dust collection. In this process, the glass surface becomes super hydrophillic due to which the contact angle between the glass surface and a dust particle is made less than 5o. As a result, the glass surface becomes self cleaning in nature. This process also improves the light transmission capacity of the glass surface which improves the solar cell current value by 5%. The nanostructured glass covered PV panels were tested outdoors for a duration of 22 days to ascertain the effectiveness of its self cleaning properties with the results being positive.
Output variation of photovoltaic modules with environmental factors — II: seasonal variation[edit | edit source]
Abstract: The paper discusses the effect of changes in the spectral solar radiation and its effect on the output power of the PV panels. By observing the ratio of incident spectral solar radiation to the global solar radiation, it was concluded that seasonal changes affect the output of PV panels made of amorphous silicon more adversely. The paper proposes a method to calculate the conversion efficiency of the PV panels keeping in mind factors such as spectral solar radiation and cell temperature. Seasonal variation effects on the factors considered were also taken into account. As a result, the effect of seasonal changes on the PV panel output could be studies by comparing the power outputs of the panels during different seasons of the year.
Abstract: A solar farm spread over 45 acres having a power output of 4.4MW near San Antonio, TX is being used for grazing livestock like sheep. This has eliminated the need for a landscaping crew, thus saving a significant amount of money in labor charges. The free-to-roam sheep go about the farm grazing away and keeping the overgrowth which was proving to be a hindrance for PV panel technicians to work on the maintenance and upkeep of the PV panels. The layout of the PV modules is such that livestock movement is not impeded. The use of sheep on the solar farm also helps the local livestock farmers twofold i.e. the solar farm operator pays the livestock farmers for grazing his livestock on the PV farm and also the burden and in turn competition for grazing land reduces. The company intends to introduce sheep on its proposed 41MW plant spread over an area of 500 acres.
The effect of tilt angle, air pollution on performance of photovoltaic systems in Tehran[edit | edit source]
Abstract: This paper attempts to reconcile theoretically calculated figures with physical data obtained from the field with the help of an experimental PV module setup. The paper discusses the effect of air pollution on the power output of the PV module and the manner in which it affects the optimal tilt angle of the modules. In order to study the effects of air pollution on the performance of the PV modules, 5 modules were set up tilted at an angle of 0, 23, 29, 42 and 35 degrees. The module tilted at 29o delivered the highest power output throughout the year as opposed to the theoretical results which were projecting highest power outputs from the 35 and 42 deg modules. Since the modules were set up in an urban area, they were covered with bird droppings which further reduced their output. Thus, it was easy to conclude that there was a significant difference between theoretical results and experimental results as the theoretical calculations did not take into account the effect of natural events like bird droppings and dust collection on the PV module surface.
Effect of dust accumulation on solar transmittance through glass covers of plate-type collectors[edit | edit source]
Abstract: This paper discusses about an experiment performed to ascertain the effect of dust collection on PV panels mounted in Egypt. The panels were not cleaned for a duration of 1 month and the effect of dust on the transmittance of the glass panel was experimentally investigated. Panels were mounted at different angles ranging from 0-90o and the transmittance values of the glass panels were co-related with that of clean glass panels after a 30 day period. On closer examination of all the panels, it was found that the panel tilted at 90o had only fine dust particles settled on its surface and the panel mounted horizontally had coarser dust particles settled on it. It was thus found that the panels mounted at angles ≥50o were relatively less affected by dust and their glass surface transmission values were not significantly affected as compared to a panel with a lower tilt angle.
Solar radiation distribution inside a greenhouse with south-oriented photovoltaic roofs and effects on crop productivity[edit | edit source]
Abstract: This paper discusses the effects of replacing 50% of the greenhouse roof area on the crops growing within. The greenhouse in question has an E-W orientation with south facing roofs. Installing a PV system on the roof of the greenhouse caused a 64% reduction in solar radiation within. However, it was observed that the solar radiation on the plants located farthest away from the PV panels was diminished by only 18%. To compensate for the loss of sunlight, additional lighting was provided within the greenhouse which was powered by the PV panels. The best way to maximize this setup is to perform intercropping within the greenhouse with shade tolerant plants being grown in the shade of the panels and shade-intolerant plants can be grown in the unaffected areas.
Abstract: The British environment secretary decided to cut subsidies for solar farms claiming they were affecting food production. The farmers refuted this claim stating that they are using their farms for producing food as well diversifying their sources of income. Evidence from some farmers claim that installing PV panels on their farms has boosted their livestock production due to the shelter offered by the PV panels. In fact rotation of land between agriculture and grazing purposes boosts income on a three-fold as the income from agriculture, livestock grazing and revenue from the solar panels can provide continuous sustainable income to the farmers. The government and law makers have still not understood the full potential of solar farms and its minimal effect on food production. This pushes the need to educate lawmakers and incorporate changes in the current policy to make more solar friendly.
Abstract: This paper provides a comprehensive review of the developments in greenhouse technology and the effect of the physical structure of the greenhouse on crop yields. The paper first presents various greenhouse models which demonstrated the effects of ambient temperature, inside air temperature, humidity, changes in sunlight, types of greenhouse roof materials etc on the growth patterns of the crop and its final effect on crop yields. The authors then give details about the physical construction of the greenhouse and its influence on yields and also greenhouse designs for specific crops. Keeping in mind the structures of greenhouses and their structures the effects of CO2 and internal climate control systems are illustrated and how each crop requires a specific type of climate control system. Overall, this article is a complete overview of greenhouse farming and shows the immense potential that a PV system can offer if integrated within these greenhouses.
Life cycle greenhouse gas emissions of crystalline silicon photovoltaic electricity generation[edit | edit source]
Abstract: This paper analyzes the existing studies on the life cycle analysis(LCA) of greenhouse gas emissions of a PV panel with an aim to provide consistency in the existing results of experiments conducted as the existing data present has a high degree of variance due to different methods and assumptions. The authors present a harmonization methodology which would impose standard assumptions on the performance characteristics to produce a reduction in variance of the results. By doing so, the variation between existing results is reduced. The paper then goes on to highlight the differences in the assumptions in the existing data and the new 'harmonized' data which have bought about a pattern of consistency between the results of the existing models for LCA of greenhouse gas emissions of a PV panel.
A simple correlation for the operating temperature of photovoltaic modules of arbitrary mounting.[edit | edit source]
Abstract: The paper discusses the relation between the PV module operating temperature and ambient temperature,wind speed, incident solar radiation and the tilt angle. The author then goes on to illustrate the relation between the PV efficiency and the operating temperature. The operating temperature of the PV panel also depends on intrinsic factors such as releasing of heat by the semiconductors due to the incident photon energy. During steady state operation, the panel releases heat to the ground via its mounting structure which in turn is radiated back towards the panel by convection currents. The author then elaborates the aforementioned co-relations and also illustrates the effect of convection and radiation on the operating temperature of the panels. These relations are then simplified to show that the efficiency and power output depend on the PV operating temperature too.
Colocation opportunities for large solar infrastructures and agriculture in drylands.[edit | edit source]
Abstract: This paper provides a review of study carried out by authors for dual use of land for solar and aloe vera cultivation in north western part of India with an aim to explore opportunities for co-locating solar PVs and crops in order to maximize efficient use of water and land. the life cycle analyses has shown that this is economically viable in rural areas and will help in rural electrification for remote locations and eventually stimulate economic growth. In areas of water limitations, the water used for aloe vera plant annually is also used for cleaning the dust and dirt accumulated on the solar panels, hence increasing the efficiency overall and decreasing socioeconomic pressure.
Fabrication of highly transparent concentrator photovoltaic module for efficient dual land use in middle DNI region.[edit | edit source]
Abstract: This paper introduces the concept of highly transparent concentrator photovoltaic (CPV) module which allows diffused sunlight to pass through it which can be used for plant cultivation and is suitable for regions of midlle direct normal irradiance (DNI) where diffuse sunlight comprises of 40-50% of global sunlight. It is experimentally demonstrated that the CPV module has a conversion efficiency over 28% for direct sunlight and module transmittance over 70% for diffuse sunlight.
More solar farms or more bioenergy crops? Mapping and assessing potential land-use conflicts among renewable energy technologies in eastern Ontario, Canada.[edit | edit source]
Abstract: Land allocation seems to be a decisive factor for implicating the future energy sustainability. Both the technologies, Solar and Bio energy need to be more productive to avail marginal and abandoned agricultural land. The purpose of the paper is to address the issue on a regional-scale regarding the intensifying solar and bio-energy production. A GIS based approach is considered identify and mark down the potential land-use conflicts amongst solar and bio energy systems.
Abstract: The deposition of dust over PV panels is a primary factor which hinders the economic growth and generation of electricity. Only a few studies have been carried out to study the effects of deposition of dust on the PV panels such as monitoring of solar irradiation, onsite determination of dust deposition rate, and processing climatic data to obtain information about the frequency of rainfall occurrence. Dust accumulated during rainless period is calculated through the experimental studies and its effect on performance of PV panel is accounted.
Influence of Solar Panels in Distributed Photovoltaic Power Generating System above Farm Land on Field and Crops.[edit | edit source]
Abstract: Arrangement of the photovoltaic panels over the farmland can be the prime solution of the off season farming and generation of electricity through solar photovoltaic. The study shows that the method has a numerous advantage such as uniform distribution of temperature, minimizing the difference between shading and lightning area and reducing the wind resistance. The solution proves to be economically profitable to the farmers practicing farming in hot climatic and arid regions.The influence of solar panel shading on Chinese cabbage was detected by photosynthetic measurement instrument LI-6400.
Abstract: A new method has been proposed and developed for carbon sequestration in dry land agricultural process. The carbon sequestration is estimated through the water-food-energy-climate nexus. Water is the most pivotal element amongst the above four elements to assess. Certain benefits of the carbon sequestration are included in the study such as moisture feedback. Two carbon sequestration projects are analysed in terms of their water productivity and carbon sequestration potential based on the study of photovoltaic water pumping (PVPW) systems for grasslands in China.
Abstract: The notable hindrance in the production of the agricultural crop in temperate climatic region is the large estimated cost of the energy utilized. Due to the increasing nature of the fossil fuels and traditional energy cost amongst the other notable factors increases the issue to emphasize more on green and sustainable choice such as solar energy. The paper discusses the application of the photovoltaic technology in the controlled environment and its affect over the economic analysis.
Abstract: The increase in the utility-scale solar energy (USSE) in size and number over the last couple of years becomes a topic of growing interest. However, the policy of maximizing the land use efficiency of USSE is vague and ambiguous. The paper discusses the numerous methods through case study of California to increase the understanding and improving the land use efficiency of USSE which significantly improves the economic, energetic and environmental ROI.
New prospects for PV powered water desalination plants: case studies in Saudi Arabia.[edit | edit source]
Abstract: The paper discusses the concept of reverse osmosis desalination embed with the photovoltaic panels. A case study of a plant situated in Saudi Arabia has been discussed. HOMER Energy Modeling Software and the DEEP 5.0 desalination software have been used to analyze the economic and Environmental feasibility. The results of the case study are analyzed to infer the business prospects of the PV-RO plants.
Embracing new agriculture commodity through integration of Java Tea as high Value Herbal crops in solar PV farms.[edit | edit source]
Abstract: The Government of Malaysia, where major occupation is agriculture, is currently working on the numerous strategic policies to maintain their declining Gross National Income (GNI). Amongst the policy, integration of agriculture and photovoltaic panel is quite an impressive one. Herbal products such as Java Tea has been identified as one of the profitable crops to be hybrid with the photovoltaic panels. The aim of this strategy is to achieve the Internal Rate of Return (IRR) at 15.74% to be profitable and to minimize waste and pollution.
Abstract: The effect of dust fouling on PV module glass cover is studied with considering various aspects like overall plane glass transmittance, spectral transmittance of anti-reflective coated glass and characterization of properties of dust. A 20% reduction is glass transmittance is observed with a dust of 5 g/sq. m of glass cover of PV module. The reduction is transmittance is considered for different types of glasses and the anti-reflective coated glass is found to exhibit less reduction in transmittance. Similarly, the size of particle and effect of level of humidity is also considered in the study of effect of dust fouling. This study can help to maintain the PV plants and schedule a cleaning in a more precise and appropriate manner.
Detection of Fast Landscape Changes: The Case of Solar Modules on Agricultural Land.[edit | edit source]
Abstract: The fast change in land usage changes may go unnoticed by survey agencies. One such case is considered from central Italy where the focus was on expanding solar PV modules on fertile agricultural land. The growth of solar panles was exponential, causing sealing of 800 ha of land in 7 yeras. To tackle this, permissions to install solar panels has been slowed down and subsidies declined, but this may not be the best policy. The policies should be based on study or feedback from open and volunteered geo information sources.
Effect of shade on photosynthetic pigments in the tropical root crops: Yam, taro, tannia, cassava and sweet potato.[edit | edit source]
Plants of yam, taro, tannia, cassava and sweet potato were raised under shade or in full sunlight and the effect of shade on leaf chlorophyll and carotenoids (class of highly unsaturated yellow to red pigments appearing in plants) was examined to determine and compare the relative shade tolerance and adaptability of the various species. All the species were found to be shade tolerant, with changes in chlorophyll concentration, cartotenoids per unit chlorophyll and weight per unit area of leaf. The extent of the changes, however, differed between species. The tolerance level for different species is specified which can help in determining which crops can suitable to use in combination with Solar PV panels with added economic advantage.
[edit | edit source]
- Can specialty crops and solar thrive together?
- Holland GroenLeven / Baywa r.e. https://www.pv -magazine.com/2020/07/23/special-solar-panels-for-agrivoltaics/
- Vertical Bifacial Application https://www.pv -magazine.com/2020/03/30/french-german-alliance-for-vertical-pv/
- CPV Panels for agrivoltaics https://www.pv -magazine.com/2020/08/04/cpv-panels-for-agrivoltaics/
- AGPV Cattle Grazing: https://www.pv -magazine.com/2019/12/06/ambitious-1-gw-agrivoltaic-livestock-farming-project-announced-in-malaysia/
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Contributors[edit | edit source]
|Michigan Tech's Open Sustainability Technology Lab.
Wanted: Students to make a distributed future with solar-powered open-source 3-D printing and recycling.