Electric vehicle charging potential from retail parking lot solar photovoltaic awnings
Introduction
Solar photovoltaic (PV) technology is a now well-established sustainable energy source [[1], [2], [3], [4]]. Although historically it has seen restricted deployment due to economics [5], rapid cost declines [6] have reduced the levelized cost of solar electricity [7] below those of conventional power sources [8,9]. Cost declines follow from a rapid learning curve in the PV industry [10,11] and technical improvements in conversion efficiency at the cell [12] and module levels [13]. By 2018 more than ten modules were on the market with over 20% conversion efficiency from various manufacturers [14]. Thus, PV has been a major recent driver [9,15] of higher penetration of renewable energy into the U.S. national energy market [16]. Although improved financing mechanisms [[17], [18], [19]] have enabled PV technology to be deployed to a greater fraction of the residential and small business market, the majority of PV is on the industrial/utility scale [20].
The growth of low-cost solar has been a welcome contribution to the U.S. electrical supply, as although the current COVID-19 pandemic is clouding the U.S. Energy Information Administration’s predictions in the short term [21], over the long-term electricity use is expected to increase in part because as the number of electric vehicles (EVs) is expected to skyrocket [22] there would be a transition from oil to electricity increasing electric demand [23,24]. EVs and plug-in hybrid electric vehicles (PHEV) are becoming increasingly important as the sales of EVs are rapidly increasing their share (2.2%) of the global vehicle market [25]. By 2040 the electric vehicle count in the market will increase up to 30% [26]. As solar is the fastest growing electricity source set to displace fossil fuels, a challenge is presented to identify the surface area needed to produce thousands of TWhs of electricity [27]. These demands can in part be met with aggressive building integrated PV (BIPV) and rooftop PV [[28], [29], [30], [31], [32], [33]], however, more surface area is needed [34]. One method to increase potential PV area, particularly well-suited for EVs is to utilize the stranded assets of non-productive parking lot areas as solar farms with PV canopies, enabling sustainable energy production while preserving their function to park automobiles [[35], [36], [37], [38], [39]]. There is already substantial research into the design and optimization of solar systems to charge EVs as a sustainable strategy [40] including at the workplace [[41], [42], [43]] because EVs could be integrated to the grid to solve intermittency challenges via vehicle-to-grid implementations [[44], [45], [46], [47], [48], [49], [50]]. In addition, technical studies have shown the viability of the approach [39,51,52].
To build on this previous work, this study provides a novel more-detailed investigation into the energy-related aspects of developing EV charging stations powered from solar PV canopies built on the parking infrastructure of large-scale retailers such as Walmart, Ikea, BestBuy, and Costco. These retailers have large warehouse-sized stores with larger parking areas, which have a substantial potential of raising PV canopies. Of these stores Walmart is used here as a case study because of its size. Walmart is larger than Home Depot, Kroger, Target, Sears, Costco, and K-Mart combined [53]. This is the first analysis to specifically look at the synergies of PV and EV charging stations as a general model for large-scale retail using parking lot PV canopies. A technical analysis is performed on parking lot areas located in the highest EV market coupled with charge station rates and the charge capacities of the top ten EV to determine: i) the solar energy generation potential of the most dense PV parking lot canopy (or awning) designs using standard and high-efficiency silicon-based PV; ii) the number of EV charging stations that could be supported by PV-covered parking lots using these canopies as well as the percentage of parking customers that could be served, and iii) the percent of charging capable during a range of shopping times as well as the distance the EVs could travel on that charge to determine the benefits to the customer. These results of this novel model are presented and discussed in the context of the potential benefits of retailers adopting this approach including reducing the heat island effect while increasing the comfort of their customers be shielding them from precipitation, increasing store selection due to green consumerism and EV ownership, and increasing time shopping of the latter.
Section snippets
Methods and calculations
The city of San Jose, California has been selected for study because according to the survey by the International Council of Clean Transportation, it is one of the cities with the highest number of EV as well as electric charging stations [54]. San Jose already has over 20% EV penetration in the market [22]. Electricity produced by PV canopies using the available solar flux [55] will be compared to the energy consumed by EV charging stations to estimate the number of EV that can be charged
Potential PV canopy areas for case study retail stores
Using the methods outlined in the previous section conservative estimates of PV canopy areas were determined. This is shown in Fig. 2, Fig. 3, Fig. 4 for the case study stores, where south is towards the bottom of all of the satellite images. The red areas in Fig. 2, Fig. 3, Fig. 4 show the areas selected. In addition, in Fig. 2, Fig. 3, Fig. 4 both the areas (m2) in each parking lot that could conservatively be used for PV awnings and the PV system output capacity (kWdc) of each section of the
Conclusions
The results of this study have shown that between 15 and 18% of the average Walmart parking lot could be serviced with solar energy powered EV charging stations in one of the largest EV markets in the U.S. This is possible with the lowest cost and low performance PV modules now and is only expected to increase in the future. The case study results for San Jose California were extremely promising as it is the largest EV market in the U.S. These results, however, can be applied to the rest of the
CRediT authorship contribution statement
Swaraj Sanjay Deshmukh: Methodology, Software, Validation, Formal analysis, Investigation, Data curation, Writing - original draft, Preparation, Writing - review & editing, Visualization. Joshua M. Pearce: Conceptualization, Ideas, Methodology, Resources, Writing - original draft, Preparation, 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
The authors would like to thank T. Byrnes for helpful discussion as well as the Witte Endowment for support.
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