Because fertile land is used for growing food and viticultural produce at high net-profit, the productive, fertile land at most agricultural sites is more valuable than the financial benefits that would arise from installing solar power systems on the land. Removing crops, vineyards or other plants in order to set up solar energy units on agricultural land is neither a viable nor a sustainable solution owing to the fact that farmers need all the land/space to produce as much agricultural produce as possible for their enterprises to be economically sustainable.
The fact that agricultural land is very scarce calls for new technological concepts to bring the vision of sustainable agriculture and farming activities that neutralise the carbon footprint effect closer to reality. Solar energy technologies offer access to cost-effective and environmentally-sustainable supplies and are perceived as having the potential to con-tribute to a reduction in the carbon footprint of the agricultural sector (Redón Santafé et al., 2014). Emerging technological concepts, such as solar farms, have also taken on a new meaning since the advent of the floating solar photo-voltaic system (Sahu et al., 2015).
Since environmental impact considerations support the application of renewable en-ergy technologies, floating solar enen-ergy systems over water surfaces (e.g. dams, ponds) are gaining in popularity in the agricultural sector (Smyth, 2011). Floating solar systems on agricultural land serve as cleaner environmental measures for harnessing power than the more traditional methods of generating electricity (e.g. coal-based power stations). How-ever, more importantly, such installations serve to reserve land space for food production.
A solar energy system on a farm could be in the form of a floating photovoltaic system, as earlier illustrated in Figure 1.2. Alternatively, a floating solar configuration could be generat-ing heat and power through a solar trackgenerat-ing system on a dynamic floatgenerat-ing pontoon (Seaflex, 2017). A tracking Liquid Solar Array (LSA), such as the concentrated floating photovoltaic energy plant illustrated in Figure 2.5 (Dickinson, 2011), would generate different energy output curves at different locations.
Figure 2.5: A concentrated floating solar system by Sunergy (Dickinson, 2011).
Concerning the system’s impact on the environment, an existing land-based photo-voltaic installation on a farm could be integrated with a floating solar installation. The pre-mium use of land and energy efficiency are the primary motivations for installing floating photovoltaic (PV) systems. Such a floating solar system would offer the added benefit of securing valuable agricultural land for the cultivation of crops and livestock (Redón Santafé et al., 2014). Depending on the latitudinal location of the floating solar installation, the en-ergy output profile would vary according to the latitude of the site of the installation. Such variations can be observed in the energy yield curves in the profiles shown in Figure 2.6.
Figure 2.6: Example of energy profile variations in solar systems at different locations in the USA (based on Post Office zip-codes) (Lew et al., 2010).
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Empirical research conducted in a study on the efficiency of a floating photovoltaic system on a lake in Korea as opposed to that of an overland photovoltaic system proved that the temperatures of the floating photovoltaic system were lower than those of the land-based photovoltaic system (Choi, 2014). Figure 2.7 shows the power output differences measured for 100 kW and 500 kW land-based (red) and water-based (blue) solar systems.
Figure 2.7: Comparison between average daily generating capacity for a floating solar and overland solar system for (a) 100 kW and (b) 500 kW system (Choi, 2014).
Floating solar panel outputs in Figure 2.7 shows a remarkable 11% increase in the energy output efficiency of the floating solar system as opposed to that of a land-based photovoltaic system. The improved solar efficiency for floating solar systems in Figure 2.7 could be explained relative to the lower ambient temperatures closer to the water surface in the case of the floating system.
Figure 2.7 confirms that, while solar photovoltaic power systems installed on a floating pontoon, the temperature parameter of the photovoltaic module significantly influences the efficiency of the energy conversion system and the energy outputs in a positive sense (Choi et al., 2013). This is because floatovoltaic systems inherently keep the reservoir water for irrigation purposes cooler, resulting in additional benefits that limit evaporation and help to control toxic algal growth (SPG Solar, 2010). Water and water moisture in the air keep the solar panels cool, thus making the solar panels more energy efficient with respect to sunlight-to-electricity conversion (Ho et al., 2015).
Since the carbon footprint of a floating solar system is directly proportional to the power generating output of such a system, the results in Figure 2.7 essentially highlight the fact that the environmental impact of the floating photovoltaic panels can be positively enhanced even more during the day by further cooling the solar panels through spraying them with water at regular intervals. Furthermore, it should be noted that the solar power conversion and performance ratios, as well as the related carbon-footprint implications, are dependent on other factors such as climate, weather, and cloud density. In practice, this means that locational sensitivity is typically compensated for by applying a conversion efficiency metric that is dependent on the climate of the area in question, as well as the combination of the proposed solar conversion equipment (Dierauf et al., 2013).
From an environmental impact perspective, these conversions are critical in environ-mental impact assessments and carbon footprint studies. The next section describes the environmental and carbon footprint legislative contexts, and reviews the literature on the environmental impacts on EIA approvals for floating solar renewable energy systems.