Could Agrivoltaics Be Part of the Solution to Decarbonization in the Outermost Regions? Case Study: Gran Canaria

Abstract

Today, on the island of Gran Canaria, conventional photovoltaic installations are being implemented on the ground, with the excuse that electricity production must be decarbonized. This is located on a highly populated island, with a shortage of flat land, and a high dependence on food, in a biodiversity hot spot on the planet. We would like to point out that agrivoltaics could provide a double solution and allow the carbon footprint of this human settlement to be further reduced. In addition, it provides greater resilience to climate change, and by reducing dependence on the outside, it would minimize the effects suffered by pandemics such as SARS-CoV-2. It would also help mitigate water stress in one area facing serious water shortage problems. The reduction of local CO₂ emissions would be achieved in four ways: production of clean electricity, reduction of the transport of fuel for electricity generation, reduction of the transport of food goods from abroad, and the absorption of CO₂ together with the emission of O₂ by the planted crops. It would also lead to greater job creation, a remedy against great soil desertification, stopping agricultural abandonment, and life in rural inland areas. This study analyzes two possible agrivoltaic installation configurations of equal power in a potato field: one with a vertical bifacial (VB) configuration and another with an optimum angle (OA). The monthly production is examined and, specifically, the economic income in the event of pouring all the production into the grid. All this takes into account the reality of the chosen place, the island of Gran Canaria (Spain).

1. Introduction

European outermost regions, such as the Canary Islands, face unique challenges due to their geographical isolation, dependence on seaborne food and fuel supplies, isolated power generation systems, and lack of connection to large electricity distribution grids, which give these regions unique characteristics [1]. In these islands, the abandonment of arable land is a worrying trend, driven by the high costs and low profitability of traditional agriculture [2]. Climate change and population growth are putting significant pressure on natural resources, causing an increase in energy and water consumption, resulting in a decrease in local agricultural production, and an increase in the need to import food products from abroad, with an increase in the carbon footprint associated with imports. In this context, the combination of land use and energy production emerges as an innovative and sustainable solution [3,4]. This system allows for the coexistence of agricultural production and solar energy generation on the same land, offering an opportunity to revitalize arable land and increase the islands’ energy and food self-sufficiency [5,6]. By combining elevated solar panels with agricultural crops, it not only maximizes land use, but also provides shade [7] and protection to crops, reducing water evaporation and improving microclimatic conditions [8], providing a balance between all the factors involved. This approach creates a perfect symbiosis between agriculture and energy, sharing the same space for a common purpose, not only allowing for the joint production of food and energy, but also indirectly contributing to the much-desired decarbonization without the need to abandon productive farmland. The most common applications for this technology based on shared land use are summarized below:

Electricity and crops (agrivolts): the most common lands are those that host vegetables, fruits, and cereals, which are protected from extreme atmospheric phenomena thanks to solar panels [9,10,11].

Electricity and pastures (rangevoltaics and ecovoltaics): It is possible to generate energy and use the land under the photovoltaic panels as specific land for livestock [12,13]. The use of solar parks as pastures for livestock provides positive externalities for the community. In addition to generating employment, it promotes other sectors such as livestock, enriches the soil, and increases biodiversity [14,15]. This practice reduces the maintenance costs of the affected areas and controls the height of vegetation, helping to prevent fires. Solar panels can be installed in such a way that they allow free passage and movement of livestock.

Electricity and greenhouses (greenhousevoltaics): These places have a higher percentage of energy consumption, given the need to maintain an adequate microclimate inside. Consequently, the installation of solar panels reduces energy expenditure [16,17]. Agrivoltaic systems (PV greenhouse or ground) with cover ratio equal to or lower than 25% did not show significant effects on plant growth and quality. Damaging effects on crop growth have been observed with coverage greater than 50%, except for strawberries and spinach [18].

Electricity and water (watervoltaics): this solution is common in coastal areas, and it is possible to install photovoltaic panels to feed a desalination plant, in order to use the water for irrigation [19,20].

Previous research has shown that the combination of agriculture and photovoltaics can achieve significant increases in both sectors and have a mutual benefit, such that it is possible to obtain up to 103% of agricultural production and 83% of solar-sourced electricity on the same surface [21]. One of the main advantages of this integration is the increase in yield per photovoltaic panel when installed in a crop field. Crop transpiration helps reduce the temperature of the environment, which improves the efficiency of solar panels. This cooling effect is crucial in hot climates and can represent a considerable improvement in energy production.

Currently, many countries are promoting policies that favor this emerging technology, placing it as a priority and essential technology for a sustainable energy transition [22]. In the energy planning of the Philippines, the massive implementation of agrivoltaic plants in its crops, mainly rice fields, is contemplated as a way to decarbonize, without compromising food security [23].

Agrivoltaic installations have a good economic return, high robustness, and a low investment risk after performing a sensitivity analysis [22]. Although these installations are more expensive than conventional photovoltaic installations on uncultivated land, they can be offset over time by the generation of energy and additional income from crops [24], and are cheaper than coplanar domestic installations on roofs. It is important to positively assess that agrivoltaic installations do not excessively limit the use of occupied land, allowing agricultural activity to continue, maximizing space efficiency, enriching the primary sector through the production of natural food, preserving jobs, maintaining land in use, and contributing to the reduction of depopulation in rural areas.

Although the implementation of agrivoltaics in horticultural or fruit crops presents challenges such as the passage of agricultural machinery and the installation of irrigation systems, these can be effectively managed through proper design and the selection of compatible crops; these drawbacks can hinder normal agricultural operations and require specific adaptations to ensure the efficiency of the system. On the other hand, when agrivoltaics is combined with livestock farms (rangevoltaics) or biodiversity projects (ecovoltaics), many of these drawbacks disappear.

The focus on low-growing horticultural crops with aerial PV installations proves to be a promising solution to take full advantage of the benefits of agrivoltaics, ensuring sustainability and efficiency in both agricultural production and energy generation [25]. These types of installations can protect crops from extreme weather conditions, such as heat waves, and contribute to minimizing wind-type soil erosion. Agrivoltaic systems could increase the resilience of crops to climate change, the shade provided by solar panels can reduce water stress in crops [8,26], which is beneficial in dry climates by improving water use efficiency, decreasing irrigation needs in crops [7].

Some crops benefit from partial shade [27], in this case, potatoes; reducing incident solar radiation by less than 30% does not result in a significant decrease in total biomass, and in the partitioning of assimilates [28], the agrivoltaic installation has allowed electricity to be produced without affecting the yield of potato crops [29]. Despite the multiple studies that have been carried out on crops under this type of installation in different parts of the world [30], more research and experimentation are needed with plant species that are more conducive to shade, determining the most appropriate separation between panels, which provides an optimal balance of sunlight between both activities.

Human beings tend to standardize all solutions and constructions for ease and convenience, which can then be implemented anywhere in the world. Depending on the case in question, the optimal solution will depend greatly on the conditions of the place where it is implemented (availability of water, radiation, temperature, aridity, wind, haze, and hail) and the type of crops most suitable for compatibility with the installation of PV [31], which means that particular and specific conditions must be drawn up based on the type of crop and the conditions of the area where the agrivoltaic installation is to be carried out.

This article explores the potential of agrivoltaics as a viable solution for the Canary Islands, analyzing its benefits, challenges, and the impact it could have on agricultural land recovery and sustainable energy generation. Could agrivoltaics be the answer to the current problems of land abandonment and the need for renewable energy in the outermost regions? Through a multidisciplinary approach, the implementation of agrivoltaic systems and their capacity to transform the agricultural and energy landscape simultaneously, in addition to the contribution towards the secondary objective of decarbonizing industrial activities, is assessed. This research is especially important in isolated island systems, where land is often scarce and of high economic value. Food security and energy are probably the two essential welfare commodities for human beings globally.

Context of Gran Canaria

The Canary Islands are a Spanish archipelago located in the Atlantic Ocean, about 110 km west of the Morocco–Western Sahara and therefore at a near-tropical latitude. Due to its proximity to the Sahara desert, the Canary Islands are frequently visited by the “Calimas”, a meteorological phenomenon consisting of the abundant presence of sand and dust in suspension in the atmosphere, caused by dust storms raised by the strong winds of the deserts located in the African continent, mainly in the Sahara and the Sahel, which causes the air to become dense and acquire low visibility, covering with a thin layer of reddish-brown color the surfaces exposed to this phenomenon [32,33]. Between 2004 and 2014, an average of 101 days of haze per year were recorded in the Canary Islands, with the lowest recorded being 60 days (year 2005) and the maximum being 139 days (year 2012) [34].

For all these reasons, the Canary Islands (Spain), considered in the EU as an ultraperipheral region, complies with everything established to carry out a specific analysis. The study has been particularized on the island of Gran Canaria, which has a total area of 1560 km² and a population of 865,756 inhabitants. As a peculiarity, 42.8% of the land has been declared to be under national or international protection. In 2020, it was visited by more than 3.6 million tourists, figures that have declined after the pandemic, even though they are in recovery.

The Canary Islands have specific geographical and meteorological characteristics, both discussed in [27], with a high population density, and significant water stress, where more than 50% of the water consumed on the island comes from the desalination of brackish well water or seawater. Currently, there are more than 46 desalination plants installed [35], high dependence on the outside, in energy of 96% [36] and 80% in food, where more than 63% of agricultural land has been abandoned. With a high unemployment rate of 18.71%, data from December 2023, it is necessary to find ways to compensate the farmer to resume his agricultural work, with agrivoltaics appearing as an option to solve, in part, all these problems.

2. Methodology

This research focuses on the economic profitability of crop fields to prevent their abandonment by incorporating photovoltaic solar panel energy production systems in agricultural areas. Two different configurations are considered to favor energy production without diminishing the quality of the cultivated products. In addition, the necessary considerations for the implementation of photovoltaics on an island, and the impacts of the massive use of agrivoltaics on the electrical grid are analyzed. This symbiosis between agriculture and energy production not only makes plantations economically viable but also reduces the progressive abandonment of cultivable areas due to low economic performance, thus helping to prevent desertification of the countryside at island, regional, and ultraperipheral levels.

The methodology used in this research step by step is described below.

Step 1: General considerations

Step 2: Justification of the selected crop

Step 3: Effect of the photovoltaics on the grid, the phenomenon of duck curve in the electricity demand.

Step 4: Analysis of the use of PV using an OA and a VB installation, energy, and economic performance.

Step 5: Conclusions.

2.1. General Considerations

Although it is true that today, with the fact of abandonment of agricultural land, letting crop areas die due to high production costs, the simplest solution for owners to obtain greater profitability from the land is to rent it to create conventional photovoltaic gardens at ground level, with the disadvantages of destruction of jobs, decrease in the production of natural foods of local origin, damage to soil fertility and biodiversity, and failing to comply with the new Common Agricultural Policy of the EU (CAP 2023–2027). Agrivoltaic installations can contribute to at least 11 of the 17 the United Nations’ Sustainable Development Goals: 1, 2, 3, 4, 6, 7, 8, 9, 12, 13, and 15 [28,37].

To achieve all these objectives, soil health must be improved in the long term. In principle, farmers will be required to carry out beneficial crop rotations. However, this work is focused on potatoes, as it is the community in Spain where there is the highest per capita consumption of this crop, although it would be necessary to analyze which other crops to alternate with.

Farmers will also increase their contribution to biodiversity by dedicating in principle at least 4% of their arable land to non-productive characteristics and areas, including fallow land. Considering that the islands have 73 species of bees, of which 26 are endemic, 40 native, and 7 exotic, Canary Islands are inside a hotspot of biodiversity in the world. Therefore, this measure is important in this case, and will be completed with an ecological scheme, which will support practices related to better nutrient management, agroecology, agroforestry, carbon farming, and animal welfare.

Furthermore, the objectives of the EU directives on climate change, energy, water, air, biodiversity, and pesticide use must be taken into account.

Currently Existing Problems, for Which the Implementation of Agrivoltaics Could Produce Some Improvement

• High food dependency

The food dependency of the Canary Islands as a whole is over 80%. There is a rate of cultivated surface per inhabitant of 75 m²/inhabitant to feed the population residing on the islands. This means that the primary sector supplies less than 20% of the food needs of the Archipelago [38,39,40]. Producing electricity would provide an extra income to the farmers, and it could be considered to allow their connection to the grid under favorable conditions, in exchange for keeping the soil in production. Global development has also generated this problem worldwide. Where population growth increases the demand for agri-food products, there is a continuous degradation of the soil and increasing water scarcity, all of which is aggravated by climate change, which makes it difficult to guarantee food security for its people [41]. To achieve greater decarbonization, local production of most of the food must be considered [42].

• Abandonment of agricultural land

The abandonment of agricultural land is a global problem in the EU [43]. In the Canary Islands, in particular, the problem began 60 years ago, when construction and tourism took off with virulence, displacing labor, land, and water from agriculture to the tourism and construction sector [44]. In the Canary Islands, 66% of agricultural land has been abandoned, while this percentage reaches 63% on the island of Gran Canaria.

• Soil desertification

The Spanish Government is developing plans at a national level to counteract soil desertification. In this report, it states that 70% of the island’s soil is affected by this problem [45]. Resuming agricultural work could partially alleviate this problem, avoiding erosion and restoring the loss of soil fertility. This type of action is proposed for the island of Lanzarote [46] to avoid a pressing loss of arable and productive land. The desertification of the island’s soil is due to a continued drought, as reflected in

Table 1. Mogán weather. Data retrieved from [47].

Month	Rainfall (mm)
January	22
February	28
March	22
April	13
May	7
June	5
July	5
August	5
September	12
October	23
November	21
December	36

, in the municipality of Mogán, soils with a high drought index and a marked tendency to erosion. Furthermore, there is a highly unsustainable exploitation of underground water resources, and as an indirect consequence of the salinization of coastal aquifers, the island currently has 1876 wells and 431 galleries, and finally, a serious crisis in traditional agriculture, with the consequent abandonment of land and deterioration of the soil and structures of traditional irrigation systems. This drought situation is particularly acute in the Canary Islands, where a decrease in rainfall of 20% is expected by the year 2100 [47]. Another phenomenon to take into account is the concentration of economic activity in coastal areas as a result of urban growth; additionally, tourism exerts intense pressure on the natural resources of the coast.

• External energy dependence

According to the report made by the Government of the Canary Islands, it is reported that 96% of the primary energy consumed in the Canary Islands in 2020 was fuel derived from petroleum, imported entirely from Nigeria [48]. This consumption includes the bunkering service carried out from the island, as a maritime service station in the mid-Atlantic Ocean; this concept represents 61% of the total energy consumption of Canary Islands. Therefore, there is an enormous energy dependence on the outside, and a lack of diversity in its energy sources, where there is no coal, natural gas, nuclear, or hydroelectric. The contribution of renewable energies is low despite its high potential, with more than 1800 h/year of photovoltaic [49], and more than 4000 h/year of onshore wind [50] and 5000 h/year offshore [51].

• Abandonment of the rural population

From the interior to the coast people are looking for job opportunities, since agriculture is a lot of work and provides few economic resources [52].

• Extreme shortage of freshwater

The Canary Islands have more than 200 desalination plants, representing 50% of the water used in Gran Canaria. Some desalination plants indeed have renewable energy sources that support their electricity consumption, but most of these are supplied directly from the grid, exchanging oil for water. Consider that oil represents 83.40% of the energy used for electricity production in Gran Canaria [50], where the energy demand for desalination processes represents 9.5% of the total electricity demand [53].

2.2. Analysis of the Selected Crop: The Potato

This type of crop has been selected for several reasons. First, it is the third most consumed food in the world, after rice and cereals. Second, its water footprint has been taken into account: while rice and cereals require 2497 L/kg and 1222 L/kg of water, respectively, potatoes need only 287 L/kg for their production [54,55,56], making them the crop with the lowest water consumption. In addition, potatoes are easy to store for long periods between harvest and consumption without deteriorating their quality, and they do not require conservation in cold storage, which represents a significant saving for their marketing. The Canary Islands, one of the territories in Spain with the highest per capita consumption of this crop, highly demand this product in local trade. Potatoes can be grown at low altitudes and have a high capacity to withstand partial shade without decreasing their productive yield [57]. For all these reasons, potatoes are a strong candidate for this type of activity. Potato consumption is divided between local production and imports from abroad. Figure 1 shows how the production of the tuber is distributed in the Canary Islands, since 60% of the total consumed comes from local cultivation.

The import curve from abroad occurs at times when domestic production is lower and is explained by the date of cultivation on the islands.

Table 2. Potato growing periods in the Canary Islands. Data retrieved from [59].

Category	Sowing	Harvest	Percentage
Extra early	1 October–31 December	15 January–15 April	31.41%
Early	1 January–31 March	15 April–15 June	51.40%
Half station	1 April–30 June	15 June–30 September	4.50%
Late	1 July–30 September	30 September–15 January	12.69%

shows the dates of cultivation based on the season. The early dates of cultivation are due to two reasons: lack of potatoes from colder climates, and greater water supply from rain on the islands.

For the potatoes to reach a size that guarantees the greatest production, the crop must be irrigated for 13 weeks. The water supply needs for the crop from the moment of germination are shown in

Table 3. Need of water. Data retrieved from [58].

L/m2/Week	Week After Sprouting
28	1–4
42	5–8
35	9–11
28	12
20	13

.

Productivity Analysis

To analyze the productivity of a given farm, the equivalent land rate (LER) [60,61] is defined as an economic parameter, which assesses both agricultural and electricity yields.

Measurement of the land equivalent ratio (LER) is defined according to the Equation (1)

$$LER={\displaystyle \frac{R_{av}}{R_{ag}}}+{\displaystyle \frac{R_{av}}{R_{fv}}}$$

(1)

where

• R_ag = Yield of the farm being only agricultural;
• R_fv = Yield of the farm being only photovoltaic;
• R_av = Yield of the farm sharing both activities.

The estimated value depends on the installation site, climate conditions, crop type, and the demand for electricity or food.

Therefore, further studies are required in arid or desertification-prone regions to evaluate how the simultaneous production of food and electricity on the same land can increase LER values above 1.

Table 4 summarizes the principal benefits of agrivoltaic systems, highlighting their superior efficiency and land-use advantages compared to conventional agricultural practices.

These advantages have driven researchers to advance optimization strategies, including the evaluation of alternative photovoltaic configurations and crop management schemes tailored to specific environmental settings and local energy–food requirements [62,63,64].

Table 4. Benefits of agrivoltaic systems.

Aspect	Benefit	Source
Land equivalence ratio (LER)	1.2–2.0	Amaducci et al., 2018 [8]
Increase in agricultural and energy income	414%	Zheng et al., 2021 [24]
Reduction in water stress in crops	30–40%	Barron-Gafford et al., 2019 [65]
Reduction of CO2 emissions		Proctor et al., 2020 [66]
Increase in solar panel efficiency	3.05–3.2%	Chudinzow et al. [46], Hayibo et al. [67]
Increase in agricultural productivity	11%	Weselek et al., 2021 [68]

Table 4. Benefits of agrivoltaic systems.

Aspect	Benefit	Source
Land equivalence ratio (LER)	1.2–2.0	Amaducci et al., 2018 [8]
Increase in agricultural and energy income	414%	Zheng et al., 2021 [24]
Reduction in water stress in crops	30–40%	Barron-Gafford et al., 2019 [65]
Reduction of CO2 emissions		Proctor et al., 2020 [66]
Increase in solar panel efficiency	3.05–3.2%	Chudinzow et al. [46], Hayibo et al. [67]
Increase in agricultural productivity	11%	Weselek et al., 2021 [68]

2.3. Choice of Configuration

The choice of this type of configuration is based on the premise that the PV installation does not hinder normal agricultural tasks, produces the maximum amount of energy, and occupies the minimum surface area of cultivable land, so that sunlight reaches the cultivation area with sufficient intensity so that the plants can develop normally (without external conditions that impede their natural growth). The density and orientation of the solar panels can reduce the amount of light available for crops, affecting their growth and yield, so it is necessary to find an optimal balance between energy generation and agricultural production, since the reduction of photosynthetically active radiation under solar panels significantly affects crop yield [28].

Following the criteria of DIN SPEC 91434 [69], it distinguishes between two main categories:

Category I: Elevated systems that allow use directly beneath the modules, such as for fruit cultivation, with a maximum loss of soil for the photovoltaic installation of 10%.

Category II: Ground-level systems that allow use between rows of modules, such as for growing vegetables, forage crops, or grazing, with a soil loss of 15% permitted.

To comply with the provisions of the aforementioned standard, the support structure of the photovoltaic installation must be taller and the spacing between rows must be greater than that provided for in conventional systems, compared to the situation of not having a cultivated surface under the panels, with the consequent decrease in the surface density of PV.

In this case, the panels will be open to the sky, placed at a height of 2.10 m from their lower part, for the OA configuration with N–S orientation, to allow the passage of people without obstacles. For the second option VB, with E–W orientation, the height of the panels will be 1 m above the ground. Regardless of the configuration chosen, the panels will be arranged in rows, which will be interrupted by intermediate transit corridors; as an installation condition, it has been considered not to lose more than 15% of the shaded cultivable soil; in both cases, a 1 MWp photovoltaic installation has been studied.

To avoid damage caused by runoff water from the panels in the event of rain, a water collection system will be arranged at the bottom of the panels, which could be used for irrigation of the crop, or stored in a tank at a lower level for later use.

2.3.1. Configuration 1: OA Installation with N–S Orientation

For this OA configuration, if the rows of panels were arranged according to DIN SPEC 91434 [69], considering the normally accepted distances based on latitude, it should be 5 m between panels, but with this configuration it would mean losing 60% of the arable agricultural land, falling outside the objective of 15%, so the distance between panels has been increased to reach the maximum recommended soil loss, obtaining a distance between rows of the structure between panels of 19.7 m, as indicated in Figure 2. As a calculation premise, it has been established that the potato furrows will not be planted under the vertical shade of the panel, so by maintaining this criterion a total of 34 potato furrows have been obtained between rows of panels, separated from each other by 50 cm.

In any case, a height of the lower part of the panels of 2.1 m has been considered. In both cases, a 5 m perimeter corridor has been used, with the four corridors between rows being 3 m wide. There are five rows of 25 m in length, which will carry 2 × 25 panels in each section. With this configuration, a land area of 2.8 ha has been occupied.

2.3.2. Configuration II: VB Installation with E–W Orientation

A study conducted at the New Jersey Agricultural Experiment Station [70] analyzed different row spacings of vertical bifacial panels.

The results indicated that while the highest energy yield per hectare was achieved with a spacing of 6.1 m, the energy production per panel surface increased with larger separations

One configuration has been consulted, where it has been possible to reduce installation costs and optimize results by using a mobile vertical system, so that the wind can move the structures hanging from the top, increasing energy production by up to 12% and reducing the cost of the supporting structure by 30% compared to a fixed vertical system. This result will depend on the intensity of the wind, direction, and radiation at each location [71]. However, the application of this technology has not been considered in the analysis carried out here.

Another way to reduce installation costs, with the indirect benefit of minimizing damage to agricultural land, is to anchor the ground using helical anchors, as they are easier to install and then dismantle without making large earth movements, reducing the volume of counterweight foundations in the installation [31].

To analyze the annual radiation losses that would be lost due to shadows in the furrow closest to the structure, the amount of agricultural soil lost for four possible separation situations has been established in

Table 5. Separation of the first furrow to the structure with VB.

First Furrow	Soil Loss	Irradiation Loss	Wide
50 cm	8.34%	74.09%	6 m
150 cm	31.25%	65.94%	8 m
250 cm	45.00%	59.82%	10 m
350 cm	54.17%	53.20%	12 m

as follows: 50 cm, 150 cm, 250 cm, and 350 cm, respectively. Observing that, logically, by separating the structures from the furrows more, the losses due to shading in the first crop furrow are less, with the consequent disadvantage of leaving more land uncultivated, increasing the loss of agricultural soil. Therefore, it has been decided to use the value of 50 cm, where the first rows of crops will see their production reduced, as well as the final quality of the crop obtained [36].

There is a possibility of using another type of crop for this first furrow, so that the shade does not harm its growth. In any case, the losses caused by partial shading of the crop will vary from one year to another, depending on the weather conditions [25]. As a solution, a vertical height of 1 m above the ground of the first panel has been considered, in order to avoid projected shade of the crop on the lower panel.

To establish the same criterion of loss of cultivable soil at a value lower than 15%, the minimum separation between the first and last row of crops concerning the structure of 50 cm has been chosen. The rows between crops will have a separation of 50 cm, so a total of 11 furrows are obtained, which occupy a length of 5 m, resulting in a total of 6 m between installation rows. With this configuration, a land area of 0.94 ha has been obtained, and the configuration can be seen in Figure 3.

3. Results and Discussions

To analyze a practical case, agricultural land has been selected in the south of the island of Gran Canaria, where two rectangular plots with an area of 0.94 and 2.8 ha, respectively, have been simulated. The two proposed configurations have been studied to implement 1 MWp of photovoltaic power. The chosen coordinates are lat. 27°45′19.54″ N and lon. 15°39′08.38″ W, being at an altitude of 7.4 m.a.s.l., and a distance from the coast of 21 m (see Figure 4).

An experiment carried out in Kuwait shows that the efficiency of photovoltaic panels gradually decreases according to the amount of particulate matter deposited on their surface when they are exposed to polluted atmospheres. After 38 days of exposure to the atmosphere with 0°, 15°, 30°, and 45° tilt angles, dust-covered glass panel transmission had decreased by 64%, 48%, 30%, and 17% [72,73], which indicates that this natural phenomenon is detrimental to the performance of the panels when the tilt angles are low. In the Canary Islands, the optimal angle is 20°, but the panel will indeed remain more immune to the effect of the haze the more vertical it is [74]. The lack of rain aggravates this problem, since it is not nature that cleans the panels (see Table 1).

During the dry winter, in Kathmandu (Nepal), people suffer from high air pollution and minimum rainfall. The efficiency of dusty solar modules due to natural dust deposition phenomena decreased by 29.76% with respect to the module which was cleaned daily. The research also showed that dust accumulation is highly concentrated at the bottom of the PV modules, having a high risk of hot spots which could eventually lead to permanent module damage [75].

Another natural phenomenon, typical of these latitudes, is the so-called “donkey’s belly” [76], which is how we know the low clouds that the trade winds bring to the Canary Islands, and given the altitude of the islands, these get trapped to the north, and a photovoltaic installation can lose more than 500 h/year in productivity if it is located on the windward side of the island, or on the leeward side, so this solar resource is greater in the south of the islands than in the north.

Another aspect to consider is the temperature of the chosen location. This location is characterized by having values with little oscillation almost all year round, as shown in

Table 6. Mogán weather. Data retrieved from [77].

Month	Temp (max) °C	Temp (min) °C
January	17.5	12.4
February	17.5	12.2
March	19.1	13.0
April	19.9	13.7
May	21.5	14.9
June	23.5	16.6
July	25.4	18.1
August	26.4	19.1
September	25.2	18.8
October	23.5	17.7
November	20.5	15.5
December	18.6	13.7

. The impact on voltage drops is minimized, obtaining greater efficiency in the installation.

For an installation that guarantees optimal performance of the installation, it is necessary to carry out a study of the terrain’s orography. In the Canary Islands, the north side of the islands is generally steep and the south side flatter, so terrace cultivation is very common. This will make it more difficult to install photovoltaic panels on a massive scale, due to the large number of hours of shade that would be projected by some terraces on others, due to the deep ravines that make up the island. This situation is worse in the case of VB W–E, than in the inclined ones with their optimal angle, facing south. Therefore, it is essential, particularly in the case of the Canary Islands, to carry out a complete study of shadows, studying in detail the location and the type of installation that is intended to be carried out, in order to achieve the best possible results. The most suitable lands for this type of use are those that are on a flat surface, away from steep slopes and those facing south without strong lateral obstacles.

There is currently no agrivoltaic installation on the island, although many installations for self-consumption have been developed in buildings and industrial warehouses, because the energy that is not purchased is cheaper than what is paid for generation and dumping into the grid, in addition to the fact that the price during hours of sunshine has fallen in recent years, due to the high photovoltaic production, mostly associated with self-consumption, with which a fall in demand is observed during hours of sunshine. Today, other forms of integration are emerging, such as floating photovoltaics on water and photovoltaics integrated in vehicles [78].

In recent years, a series of photovoltaic installations have emerged directly on agricultural land, because the land is cheaper than urban land and presents fewer difficulties, and in addition, the owner of the land achieves a return, either by renting the land or by generating energy, without having to work or hire employees to operate the photovoltaic farm. However, it makes no sense on an island with a high population and little flat land to occupy all the agricultural land with conventional photovoltaic plants, killing the soil fertility, and importing food from abroad, with a significant increase in the carbon footprint of human activity on the island that this measure is causing.

With the incorporation of more photovoltaic power into the grid, mainly in self-consumption industrial facilities around the world, it causes the phenomenon known as the “duck curve effect” in the production system, which causes the need for energy storage systems in the networks, and will further increase the price difference between hours of electrical power. To counteract this harmful effect, some measures can be adopted to achieve the flattening of the duck curve [79], and the most commonly used methods are [80,81,82,83,84]:

Energy storage: Overproduction of solar power during the day can be stored during those hours. Right now, most solar systems do not have automated frequency response, but they are capable of it. Therefore, it will be necessary to maintain a large rolling reserve, or fast-response storage systems, to compensate for variations in frequency with their inertia. This phenomenon appears both in wind power and in photovoltaic plants, because large oscillations in their generation develop with very steep ramps during the production period.

This is conducted by automated frequency response systems, usually on conventional power plants. If solar starts shutting down all those plants in the middle of the day, the grid loses those resources, and with it some stability [85].

Other clean sources: Unlike solar energy, sources like nuclear, hydroelectric, and geothermal can operate continuously and fill in the demand gap. None of these technologies are available on the island of Gran Canaria.

Demand management: It is possible to try to change the distribution of electrical demand, using prices or other instruments, to shift loads or flexible consumption systems towards those hours of high generation.

Changing the orientation of the solar panels: More VB E–W photovoltaic systems can be implemented, whose production curve is quite different from the conventional one, affecting the duck curve less and increasing generation during hours of greater demand [67].

Power to X: The option of converting that non-manageable electricity into a useful energy product, such as e-fuel, or heat. The conversion systems must be flexible, to adjust to the resource, by itself, or by incorporating fast-response storage devices that cushion the fluctuations of the resource.

Another possibility, which is raised in this study as a possible solution to water scarcity, is the following:

Desalination of seawater for irrigation: using a small reverse osmosis desalination plant that meets the water needs of the plantation. With this possible alternative, a symbiotic process of income could be achieved between the sale of desalinated water and surplus electricity, and agricultural products. Obviously, the profitability of electricity is greater in the case of self-consumption, instead of pouring the energy into the grid. In the case of self-consumption, a management system is proposed to overlap desalination with the hours of maximum electricity generation and lower value in sale to the grid. It would be a flexible load system, this being desalination. Currently, modern osmosis desalination systems have an energy consumption of 2.8–3.5 kWh/m³ of desalinated water [86,87].

Taking into account that the water must be previously collected from a well on the coast and filtered, it is considered that the system will require between 3.2 and 4.0 kWh/m³ [88,89]. Pumping between the lower and upper reservoirs in this case will consume approximately 0.45–0.6 kWh/m³. Thus, the total energy consumption due to irrigation using seawater is set, in this case, at 3.7–4.6 kWh/m³ [90].

To maximize water resources, irrigation is proposed in the hours before dawn, to avoid large water losses due to evaporation, and to coincide with the crop activity hours once the day breaks, avoiding watering at night because the roots remain wet for many hours, which would cause the appearance of harmful fungi. To carry out this operation, two water tanks are proposed on the farm, both placed at different levels, the one at the lower level will store the desalinated water at the exit of the desalination plant; this point is also where all the water from rain, by the collectors placed under the photovoltaic panels arranged at an optimal angle, is accumulated. The second tank will be located at a higher level, and the hours of maximum energy production will be used to pump water from one to the other and thus be able to irrigate in the early hours of the morning, supplying water to the irrigation heads by gravity from the upper tank, without any electrical consumption.

The average annual contribution to the grid on the island of Gran Canaria during 2023, the conventional one, which in this case is only oil, since even the gas turbines operate with diesel, is 81% compared to renewables which reach 19%, of which 14.4% belongs to photovoltaics (see Figure 5).

Today, the power supplied to the grid by photovoltaics is low. Looking at the hourly demand curve for Gran Canaria, see Figure 6, obtained from REE [48], the photovoltaic production fed into the grid is analyzed exclusively, not the self-consumed one, since this causes a decrease in the demand of the associated installations. A low contribution of energy can be observed in the morning, increasing progressively until reaching the maximum injection of photovoltaics into the grid at 2:05 p.m., providing 10.91% of the total energy consumed in the grid.

A practical and simple way to avoid duck curve effect is by altering the arrangement of the panels. Using VB E–W panels instead of the OA orientation, the production is boosted at the beginning and end of the day, which will be the ones that will become more expensive, as photovoltaic installations proliferate to a greater extent [81].

To maximize the income from the production of the agrivoltaic installation, and also reduce the effect of the duck curve [79], it has been considered to make a comparison at equal power of the VB E–W installation, concerning OA N–S.

For this purpose, the European PVGIS software is used [92]. The photovoltaic performance of the two proposed configurations was simulated using the Photovoltaic Geographical Information System (PVGIS), developed by the European Commission’s Joint Research Centre (JRC). PVGIS provides site-specific solar radiation and photovoltaic performance data, combining satellite and ground radiation measurements, air temperature records, and elevation models [93].

Since its inception in 2001, PVGIS has evolved into version 5, expanding its geographic coverage and data sources; for example, the solar radiation product SARAH-Edition 2 is used in PVGIS v5.2 for long-term monthly averages (2005–2020).

Among peer-reviewed studies, performed a comparative evaluation of PVGIS, PVWatts, and RETScreen, assessing their accuracy using empirical data from PV arrays in Greece; PVGIS showed reliable performance, particularly under specific orientations and tilt angles [94].

The days of haze, or cloudy skies, where a large part of the irradiance would be diffuse, have not been considered in this study, and it is known that the horizontal surface is the one that captures the most diffuse radiation, and the one that suffers a greater reduction in efficiency due to the deposition of dust, a natural phenomenon that appears with some frequency in these latitudes [95]. Figure 7 shows the production for the months of January and July, respectively, where it is observed that the VB arrangement increases the radiation captured in the first and last hours of sunlight, while the OA orientation concentrates the maximum production in the central hours of the day.

The theoretical energy production for the different months of the year, for both configurations, are shown in

Table 7. Monthly energy generation (MWh).

Month	Optimal Angle	Bifacial	Difference (%)
January	127.762	106.473	16.7
February	131.817	118.365	10.2
March	162.135	151.454	6.6
April	166.421	162.789	2.2
May	174.175	173.514	0.4
June	166.043	163.923	1.3
July	175.213	170.256	2.8
August	169.509	163.301	3.7
September	149.204	142.425	4.5
October	139.805	126.166	9.8
November	122.305	104.661	14.4
December	123.113	100.168	18.7
MWh/year	1807.502	1683.495	6.86

, observing that the greatest difference in production between both systems is obtained in the month of December, reaching a value of 18.64%, while in the month of May, the productions are equal, with a minimum difference of 0.38%. Performing the annual calculation, it is observed that the vertical system generates 6.86% less energy per year, there being a smaller difference in summer than in winter [70]; however, this annual difference is mainly due to the position of the Canary Islands concerning the Earth’s equator, it has been studied that for values higher than the latitude of 50° the VB systems develop a greater production than the OA, although there are other studies that do not corroborate this statement [26].

In order to determine the real monetary income, depending on whether the OA or VB configuration is used, the average daily hourly prices have been calculated between the month of February 2023 and January 2024, according to the data offered by the Iberian market operator OMIE [50], and represented in Figure 8, where the average hourly monetary values by stations are shown. It can be observed that there are two well-differentiated time periods, for the four stations, where the energy produced generates greater income. The first section is in the morning between 07:00 and 10:00 a.m. and the second section is in the afternoon–evening between 04:00 and 9:30 p.m. The section where the energy reaches its minimum sale value is between 10:00 and 14:00, although to optimize the photovoltaic installations and maximize monetary income, it will be chosen to cover production between the time slots where the sale prices are higher. Although expensive, these time slots are a priority target. The periods of highest income from the sale of energy occur in the fall and summer seasons, coinciding with the maximum time slots in both.

If the energy sales data are analyzed, it can be seen that in January the income that would be obtained from the sale of generation in the case of a system with OA to the south, compared to a VB E–W, would be 13.7% higher. Despite the fact that with the bifacial installation a 16.66% lower energy generation is obtained, the hourly sale price benefits the VB configuration. For July, despite 2.83% less energy is generated with the vertical panels, 3.8% more money is earned. It is also striking that the income received between January and July is only reduced by 2.94% for the OA configuration (see

Table 8. Monthly income (€).

Month	O.A. (€)	V.B. E-W (€)	Monetary Loss (€)	% VB vs. OA
January	12,133	10,466	1667	−13.7%
July	12,500	12,977	−477	+3.8%

); the explanation is that although more electricity is generated in July, its price falls more than in January during hours of sunshine. Other studies carried out in various European countries conclude that higher economic income is obtained with a VB configuration than with OA [67].

4. Conclusions

The VB configuration has a considerably lower land occupation, avoiding the cost of high structures that allow the transit of people underneath. Maintaining the recommendation of not losing more than 15% of agricultural land according to the DIN SPEC 91434 standard, the OA option needs almost three times the arable land to install the same power; for the VB configuration it is necessary to have 0.94 ha compared to the 2.8 ha of the OA configuration.

The effect of the deposition of particulate matter of natural origin due to the recurrent episodes of haze that occur in the Canary Islands, with the loss of energy associated with this configuration aggravated by the lack of rain to clean the modules, is much lower for the VB configuration.

By changing the power generation curve from OA to VB, it does not contribute to accentuating the duck curve, overlapping the power generation peaks with the maximum daily demand, which is a benefit for the island’s electrical system, and an economical benefit for the farmer.

The VB configuration produces only 6.86% less energy per year compared to an OA installation. In January, the income obtained from the sale of generation in the case of a system with OA to the south, compared to a VB, would be 13.7% higher, with sales in the months of maximum energy production being very similar in both configurations. The current strong increase in installed photovoltaic power in Spain is putting downward pressure on prices at midday and increasing at the beginning and end of the day, which will further favor the profitability of VB installations.

With the use of photovoltaics, decarbonization is increased, reducing the carbon footprint for four reasons:

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Reduction in the burning of oil to produce electricity;

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Reduction in the need to transport oil from abroad;

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Reduction in the need to transport food products from abroad;

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Capture of CO₂ and increase in the production of O₂ in the crops grown.

The use that will be made of the electricity produced is not determined, and all production can be injected directly into the grid. It is economically more interesting to desalinate seawater when the sale value is low or even zero, and to sell energy at times of high prices. Agrivoltaic systems, which promote crop yields, the production of clean energy, and water savings, can play an important role in the relationship between energy, food, and water [8].

Although it is true that agrivoltaics make both activities more expensive, they are an urgent need on an island with little flat land. We have seen some problems in Gran Canaria, which would be improved with high implementation of this technology.

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It would stop the desertification of the soil, since the roots fix it;

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It would reduce the need for irrigation of crops, on an island with a strong lack of fresh water;

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It would reduce the abandonment of crops on a densely populated island with a high dependence on food from abroad. It would create rural wealth on an island with a strong population abandonment of the countryside;

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It would increase employment on an island with a high unemployment rate;

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It would provide better performance in the face of increasingly frequent haze episodes;

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It would reduce the island’s strong dependence on the outside, increasing its resilience;

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It improves biodiversity in an important hot spot on the planet.

Agrivoltaic installations are a viable and profitable investment that offers multiple economic and social benefits. By obtaining dual use of the land, these installations not only optimize agricultural and energy production, but also contribute to the sustainability and resilience of rural communities. Policies that favor them will be approved throughout the world.