Policy and Environmental Implications of Photovoltaic Systems in Farming in Southeast Spain: Can Greenhouses Reduce the Greenhouse Effect?

Solar photovoltaic (PV) systems have grown in popularity in the farming sector, primarily because land area and farm structures themselves, such as greenhouses, can be exploited for this purpose, and, moreover, because farms tend to be located in rural areas far from energy production plants. In Spain, despite being a country with enormous potential for this renewable energy source, little is being done to exploit it, and policies of recent years have even restricted its implementation. These factors constitute an obstacle, both for achieving environmental commitments and for socioeconomic development. This study proposes the installation of PV systems on greenhouses in southeast Spain, the location with the highest concentration of greenhouses in Europe. Following a sensitivity analysis, it is estimated that the utilization of this technology in the self-consumption scenario at farm level produces increased profitability for farms, which can range from 0.88% (worst scenario) to 52.78% (most favorable scenario). Regarding the Spanish environmental policy, the results obtained demonstrate that the impact of applying this technology mounted on greenhouses would bring the country 38% closer to reaching the 2030 greenhouse gas (GHG) target. Furthermore, it would make it possible to nearly achieve the official commitment of 20% renewable energies by 2020. Additionally, it would have considerable effects on the regional socioeconomy, with increases in job creation and contribution to gross domestic product (GDP)/R&D (Research and Development), allowing greater profitability in agrifood activities throughout the entire region

An Economic, Energy, and Environmental Analysis of PV/Micro-CHP Hybrid Systems: A Case Study of a Tertiary Building

Our present standard of living depends strongly on energy sources, with buildings being a primary focus when it comes to reducing energy consumption due to their large contribution, especially in tertiary buildings. The goal of the present study is to evaluate the performance of two different designs of hybrid systems, composed of natural gas engines and photovoltaic panels. This will be done through simulations in TRNSYS, considering a representative office building with various schedules of operation (8, 12, and 24 h), as well as different climates in Spain. The main contributions of this paper are the evaluations of primary energy-consumption, emissions, and economic analyses for each scenario. In addition, a sensitivity analysis is carried out to observe the influence of energy prices, as well as that of the costs of the micro-CHP engines and PV modules. The results show that the scenario with the conventional system and PV modules is the most profitable one currently. However, if electricity prices are increased in the future or natural gas prices are reduced, the scenario with micro-CHP engines and PV modules will become the most profitable option. Energy service engineers, regulators, and manufacturers are the most interested in these results

Innovative uses of renewable energy sources in the agricultural sector on the island of Crete, Greece

Although Crete is an island highly utilizing renewable energy sources (RES) for heat and power generation, their further applications in agriculture would result in many socioeconomic and environmental benefits. The use of renewable energies integrated in greenhouses in Crete is nowadays rather limited, and it could be increased in the future since the resources are abundant and the technologies are mature, reliable and cost-effective. Solar energy, solid and gaseous biomass, and low enthalpy geothermal energy could be used in order to provide heat, cooling and electricity to greenhouses to cover part or all of their energy needs. The positive impacts of their use include: additional income to the farmers, a reduction of greenhouse gas emissions due to energy use in them, an increase of employment in the local community and a decrease of energy dependency in Crete.The establishment of zero CO₂ emissions greenhouses due to energy use in Crete is currently feasible and cost-effective with the use of the existing renewable energies being available on the island. Unexploited renewable energy sources like landfill gas in Crete can also be used effectively for heating them. Biomass is currently used mainly for heat production in Crete, but new applications could be realized in the future including power generation and the production of biofuels. Olive kernel wood, a byproduct of the olive kernel oil producing industry, is extensively used in Crete for heat production. Besides heat generation, it could be used for the co-generation of heat and power and this process could be profitable under some conditions. Olive kernel wood could also be used as a raw material together with olive tree prunings for the manufacture of wood pellets in Crete. The work included in this thesis investigates various innovative uses and applications of sustainable energies in Crete, Greece, which could contribute to the promotion of energy sustainability in the agricultural sector of the island

Hydrogen and renewable energy sources integrated system for greenhouse heating

The environmental impact and the cost of fossil fuel system for greenhouse heating are the major limits for the development of protected horticulture. Recent researches are focusing on greenhouses optimal climate control and reduction of energy consumption. The use of suitable microclimate control systems, energy efficiency strategies and renewable energy sources could improve the environmental performance of the greenhouses. Renewable energy sources can be used to produce hydrogen by electrolysis with very high gas purity. Hydrogen can serve the purpose of storing overproduced energy after meeting the requirements of the greenhouse, and later it can be employed as fuel, achieving a stand-alone power system. Therefore a research is under development at the University of Bari in order to investigate the suitable solutions of a power system based on solar energy (photovoltaic) and hydrogen, integrated with a geothermal heat pump for powering a self sustained heated greenhouse. The tests were carried out at the experimental farm of the University of Bari sited in Valenzano, Bari, Southern Italy, latitude 41° N, where two experimental greenhouses, with the same geometric and constructive characteristics, have been realized; the distance between the two greenhouses is 12 m; therefore there is no mutual shading. One of the two greenhouses is heated using a low enthalpy heat pump combined with a vertical ground heat exchanger, in comparison with the other unheated greenhouse. The electrical energy for heat pump operation is provided by a purpose-built array of solar photovoltaic modules, which supplies also a water electrolyser system controlled by embedded pc; the generated dry hydrogen gas is conserved in suitable pressured storage tank. The hydrogen is used to produce electricity in a fuel cell in order to meet the above mentioned heat pump power demand when the photovoltaic system is inactive during winter night-time or the solar radiation level is insufficient to meet the electrical demand of the heat pump during overcast cold sky. This note reports the main elements regarding the integrated system design and building and it shows preliminary results of testing operation

Experimental tests to recover the photovoltaic power by battery system

The uncertainty and variability of the Renewable Energy Sources (RES) power plants within the power grid is an open issue. The present study focuses on the use of batteries to overcome the limitations associated with the photovoltaic inverter operation, trying to maximize the global energy produced. A set of switches, was placed between a few photovoltaic modules and a commercial inverter, capable to change configuration of the plant dynamically. Such system stores the power that the inverter is not able to let into the grid inside batteries. At the base of this optimization, there is the achievement of two main configurations in which the batteries and the photovoltaic modules are electrically connected in an appropriate manner as a function of inverter efficiency and thus solar radiation. A control board and the relative program, to change the configuration, was designed and implemented, based on the value of the measured radiation, current, batteries voltage, and calculated inverter efficiency. Finally from the cost and impact analysis we can say that, today the technology of lithium batteries, for this application, is still too expensive in comparison with lead-acid batteries

Storage systems for building-integrated photovoltaic (BIPV) and building-integrated photovoltaic/thermal (BIPVT) installations: Environmental profile and other aspects

In recent years there has been an increasing interest in Building-Integrated Photovoltaic (BIPV) and Building-Integrated Photovoltaic/Thermal (BIPVT) systems since they produce clean energy and replace conventional building envelope materials. By taking into account that storage is a key factor in the effective use of renewable energy, the present article is an overview about storage systems which are appropriate for BIPV and BIPVT applications. The literature review shows that there are multiple storage solutions, based on different kinds of materials (batteries, Phase Change Material (PCM) components, etc.). In terms of BIPV and BIPVT with batteries or PCMs or water tanks as storage systems, most of the installations are non-concentrating, façade- or roof-integrated, water- or air-based (in the case of BIPVT) and include silicon-based PV cells, lead-acid or lithium-ion batteries, paraffin- or salt-based PCMs. Regarding parameters that affect the environmental profile of storage systems, in the case of batteries critical factors such as material manufacturing, accidental release of electrolytes, inhalation toxicity, flammable elements, degradation and end-of-life management play a pivotal role. Regarding PCMs, there are some materials that are corrosive and present fire-safety issues as well as high toxicity in terms of human health and ecosystems. Concerning water storage tanks, based on certain studies about tanks with volumes of 300 L and 600 L, their impacts range from 5.9 to 11.7 GJprim and from 0.3 to 1.0 t CO2.eq. Finally, it should be noted that additional storage options such as Trombe walls, pebble beds and nanotechnologies are critically discussed. The contribution of the present article to the existing literature is associated with the fact that it presents a critical review about storage devices in the case of BIPV and BIPVT applications, by placing emphasis on the environmental profile of certain storage materials.The authors would like to thank “Ministerio de Economía y Competitividad” of Spain for the funding (grant reference ENE2016-81040-R). Furthermore, Professor Daniel Chemisana thanks “Institució Catalana de Recerca i Estudis Avançats (ICREA)” for the ICREA Acadèmia award (ICREA Acadèmia 2018)

Advanced Energy Modelling and Life Cycle Assessment of Indoor Agriculture

This thesis investigates the agricultural greenhouse sector in a cold climate, which requires a large amount of natural gas for supplying the substantial heating demands. The heating demand of these structures is calculated, and potential sustainable design methods are implemented to reduce the reliance on carbon-based fuels. Assessment of the environmental impacts of a bell pepper greenhouse in Southwestern Ontario, Canada heated by natural gas was studied. A life cycle assessment (LCA) method is employed to scrutinize the bell pepper greenhouse, pinpointing areas that need improvement. It was concluded that Global Warming (GW) is the significant environmental hazard among other environmental categories (3.87e-2 kg ??2-Eq). It should be noted, the main contributor to global warming is the natural gas being used as the heating resource (3.2e-2 kg ??2-Eq). The analysis is extended to explore the deployment of solar energy as an alternative source for heating. Solar energy is found to be a superior alternative in terms of emissions. Furthermore, in order to integrate solar energy into the energy supplying systems of the greenhouses, a hybrid Solar Thermal/Photovoltaic-Battery Energy Storage (ST/PV-BES) system is modeled. Evaluation of the best configuration of photovoltaic (PV) and solar thermal (ST) modules, and battery energy storage (BES) size to have the minimum Levelized Cost of Energy (LCOE) was conducted. It is proved that the system is economically optimized. Moreover, to improve operational efficiency and reduce the energy demand of commercial greenhouses, parametric optimization of major growing environment variables including cladding material and window to wall ratio as well as the characteristics of the solar thermal model elements such as hot water tank capacity and heat exchanger effectiveness was carried out. It is demonstrated that the best greenhouse configuration which is a system with 80% window area and 20% brick wall area in both lower nodes and upper nodes results in heating and cooling demand energy reduction without significantly compromising the solar energy absorption. This scenario leads to increasing system performance from 36% to 39%. It is also concluded that doubling the tank capacity improves system performance from 36% to 43% and changing the heat exchanger effectiveness has minor impacts on the system performance

Research Trends on Greenhouse Engineering Using a Science Mapping Approach

Horticultural protected cultivation has spread throughout the world as it has proven to be extremely effective. In recent years, the greenhouse engineering research field has become one of the main research topics within greenhouse farming. The main objectives of the current study were to identify the major research topics and their trends during the last four decades by analyzing the co-occurrence network of keywords associated with greenhouse engineering publications. A total of 3804 pertinent documents published, in 1981-2021, were analyzed and discussed. China, the United States, Spain, Italy and the Netherlands have been the most active countries with more than 36% of the relevant literature. The keyword cluster analysis suggested the presence of five principal research topics: energy management and storage; monitoring and control of greenhouse climate parameters; automation of greenhouse operations through the internet of things (IoT) and wireless sensor network (WSN) applications; greenhouse covering materials and microclimate optimization in relation to plant growth; structural and functional design for improving greenhouse stability, ventilation and microclimate. Recent research trends are focused on real-time monitoring and automatic control systems based on the IoT and WSN technologies, multi-objective optimization approaches for greenhouse climate control, efficient artificial lighting and sustainable greenhouse crop cultivation using renewable energy