• Energy Research

Experimental strategies for controlling humidity were compared in a greenhouse sited in Madrid, a continental sitein the Mediterranean region. Small roof window apertures significantly reduced the relative humidity with only alimited increase in associated energy consumption. A simplified climate model with four energy exchange terms(heating, insolation, losses through structure, and losses through windows) and three mass exchange terms(evapotranspiration, losses through structure, and losses through windows) was validated, allowing relative humidityto be predicted with an error of < 9%.

The new energy context since 2021 has led to dramatic increases in the energy bills of agribusinesses, affecting the price of foodstuffs. A considerable part of energy consumption is due to the heating of water at high temperatures. The present study analyzed the feasibility of using a Solar Water Heating System (SWHS) with an evacuated tube collector. In particular, the required sizing changes, potential savings and cost-effectiveness were analyzed. The results show that the new energy context makes the SWHS investment highly attractive: a payback of less than 4 years in most of the scenarios analyzed; energy savings of more than 60% in the scenarios with higher irradiation; a reduction in total energy expenditure of more than 50% in the favorable scenarios close to the current reality. The new context especially favors cold and temperate climates, with very sharp drops in payback compared to the previous situation. To achieve these values, it is necessary to design an optimized sizing of the SWHS, reducing the risk of future variations in the price of energy. The results of the study should serve as a reference for decision making in the agroindustrial sector to reduce the energy bill and strategic dependence on fossil fuels from third countries.

Wind power can play an interesting role in irrigation projects in different areas. A methodology can determine the feasibility of the technology and the levels of daily irrigation demand satisfied by windmills at different levels of risk, using tomato (Lycopersicon esculentum Mill) as greenhouse crop. The present work compared the feasibility of the technology and the critical factors involved in three different countries: Cuba, Spain and Pakistan. The study considered as factors the wind speed level, the energy cost, the tomato prices, the reliability and distance to the electrical grid, and the crop development dates, determining the economic feasibility for each combination of factors in each country.

The role of the agrifood industry is key to mitigating the impact of climate change, as it is one of the industrial sectors with the highest energy consumption. The optimisation of photovoltaic systems in agroindustries faces problems such as the fluctuation of energy prices or the evident seasonal nature of some producers. This paper provides a global view of the profitability and optimal sizing of photovoltaic (PV) systems in the new energy context. For this purpose, almost 4 million cases were analysed, including different consumption patterns, energy prices, etc. Some general conclusions can be drawn from the results. First, the adaptation to the new context requires adjustments in the sizing of PV systems in all industries analysed, which is also associated with changes in the return on investment. Second, seasonality strongly conditions the optimal size of PV installations, the return on the investment and the potential savings. Finally, in the face of future energy price variations, the ratio “Savings/payback” seems to be an appropriate reference for sizing, combining savings and profitability. In addition, they may justify special subsidies to seasonal industries. The conclusions of this paper should be considered to optimise the design of PVs.

The present work analyzes the feasibility of using solar water heating systems (SWHS) to supply the hot water required in the winemaking industries. The hot water demand of the sector was characterized by selecting patterns that encompass the wide range of existing casuistry. After determining the production potential of the SWHS by using an experimental system, 22500 energy simulations were carried out, combining different locations, energy prices, and prices of the necessary investment. The results demonstrate that the seasonality and irregularity of a winery’s demand pattern drastically condition the viability and profitability of SWHS. In wineries with high demand, which are relatively uniform throughout the year, the solar system with optimized design achieves energy consumption reductions between 32% (low radiation) and 52% (high radiation), with payback between 4.3 and 7.2 years. On the other hand, in wineries with highly seasonal consumption, SWHS are not profitable even in very favorable cases.

The Spanish agri-food industries face a new energy context radically different from the one existing less than a year ago. A comparable situation is occurring in other European countries. The great variability and different seasonality of the agro-industries condition the adaptation measures to be implemented. This article quantifies the impact of the new energy context on real industries with quite different consumption patterns. More than 1000 scenarios have been analysed to determine the effectiveness of adaptation measures. The study results demonstrate the critical situation to which the sector is subjected. The new tariff system affects the agri-food sector in an unequal way, benefiting industries with marked seasonality. In just one year, the electricity bill has increased between 62% and 151%. The savings generated by implementing measures such as optimising contracted power to a new hourly discrimination system (up to 6%) or shifting consumption to lower-cost periods (up to 21%) do not seem sufficient. If prices do not fall drastically, immediate installation of generation systems, such as photovoltaic panels, appears essential to maintain the viability and competitiveness of the sector.