Distributed manufacturing of after market flexible floating photovoltaic modules

Simple combustion of fossil fuels is increasing atmospheric CO₂ concentrations and driving climate change [1], [2], [3], [4]. To prevent dangerous temperature increases the Intergovernmental Panel on Climate Change (IPCC) suggested that carbon budget be limited [5] and thus over 80% of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C global temperature rise [6]. Numerous studies make it clear that humanity needs to move towards clean and renewable sources of energy generation [7], [8], [9], [10], [11], [12]. Of the renewable energy sources, solar photovoltaic (PV) technology is the most widely accessible sustainable and clean source of energy that can be scaled to meet humanity's energy needs [13], [14], [15]. The scale of solar PV technology demands large surface areas on both buildings (e.g. rooftop PV or building integrated PV (BIPV) and PV farms [16], [17], [18], [19]. However, despite life cycle carbon emissions [20] PV is more land efficient than even the best carbon capture and sequestration plans for coal [21]. A substantial amount of land is still needed for PV to even replace all the current fossil fuel generated electricity and this creates competition for limited land resources between food and energy demand [22], [23]. With nearly a billion people living undernourished now further reductions in agriculture land is an unacceptable during a world food crisis [24].

One approach recently gaining traction in the literature and in test sites over the globe is the concept of floating photovoltaics or FPV [25], [26], [27], [28], [29], [30], [31]. FPV installation has many advantages. As the PV in FPV are physically positioned close to or immersed in water, the operational temperature is reduced, which raises power conversion efficiency [26], [29], [32], [33], [34], [35], [36]. In regions where water scarcity is an issue, FPV has the additional major benefit that it reduces water loss because it reduces water evaporation by 70–85% [34], [37], [38], [39], [40]. FPV systems have the potential to form agrivoltaic type systems [41] by merging with aquaculture to form aquavoltaics [42]. Finally, FPV could also be used for drying and further reduce heat use [43].

The latter flexible thin film PV for FPV concept is relatively new with the first flexible floating concept being developed at MIRARCO, Sadbury Canada [29]. This type of design is extremely simple, cost-effective and potentially better suited for challenging aquatic environments. There is thus an opportunity to develop a design incorporating commercially available flexible PV modules for use in an after-market distributed manufacturing method of FPV. In this study, design considerations for developing such an open source after-market distributed manufacturing method will be applied to large flexible panels to make FPV. Specifically, this study will consider surface floating of thin film solar FPV, mechanical and electrical connections on water, floating materials, and mooring. Three types of such thin film FPV panels are tested with three different floating materials: i) neoprene, ii) mincell, and iii) polyethylene based on their buoyancy. The PV panels are peel and stick and these foams are adhered to the panels. The systems undergo indoor tests for floatation and wave resistance. Outdoor testing is performed with temperature monitoring to test the cooling effect and resistance to algae accumulation for each foam material. The system was deployed in the Keweenaw Waterway in the upper peninsula of Michigan to simulate how these arrays could be used seasonally because of their ease of deployment. The results of the FPV system design, fabrication and testing will be discussed in terms of the viability of this approach.

Design

This study details the design for converting Uni-Solar PVL-68 modules [52] into FPV devices. This conversion is made possible by bonding foam to the back of the modules. The height, h, that the PV module rises above the water with a foam of known density was calculated using:h=ρF·AP·t+mPρf·APwhere ρ_f is fluid density, ρ_F is foam density, A_P is the area of the PV module, t is the thickness of foam, and m_P is the mass of the panel.

Table 1 was generated using Eq. (1) and densities found in the

Results

Testing the flotation in the indoor pool found that the measured height was lower than the calculated value but was the closest for the 1.2 lb PE as can be seen in Table 4.

After the testing the flotation in the pool it was deployed at the GLRC. Algal growth was clear on the tarp but not on the top surface of the modules (Fig. 6). On the underside (foam side) there was significant algal growth as shown in Fig. 7. The neoprene experienced very little algal accumulation and had mostly solids stuck

Performance and economic advantages

FPV is advantageous to land based PV system deployments. Flexible FPV like the one designed in this study are even more advantageous. Non-flexible FPV systems incorporate commercially available metal framed modules. These panels are supported by racking built into rafts. In most designs, the water would need to be pumped on to the panels to cool and clean them [29]. Flexible FPV does not needs this as its modules are in direct contact with the water allowing for continuous cooling. Als o being

Conclusions

In this study, an FPV system was designed using an open source after-market distributed manufacturing method that could be used for making small systems to power individual devices or applications like solar power for off-grid cottages. The ability to easily deploy or store such systems could make them available for partial year use in seasonal homes. The results were promising and could be developed to be applied to larger arrays of flexible PV modules in regions where ice and snow would not

CRediT authorship contribution statement

Pierce Mayville: Methodology, Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization. Neha Vijay Patil: Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Writing - review & editing, Visualization. Joshua M. Pearce: Conceptualization, Methodology, Formal analysis, Resources, Writing - original draft, Writing - review & editing, Supervision, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This research was funded by the Witte Endowment. We would like to thank the Great Lakes Research Center and the Coordinator of Marine Operations at the GLRC, Jamey Anderson, for providing us with a place to deploy the prototype FPV system and for helping us deploy it.