Solar energy for a clean agri-food industry

The agri-food industry is one of the largest in volume, activity and energy consumption in the world. Therefore, seeking strategies to reduce its use of polluting energies is a very important objective in view of the need for human civilization to make the energy transition towards clean energies.

In the European Union, the agri-food industry employs 4.6 million people, generates a turnover of 1.1 trillion euros and 229 billion euros of added value. In Spain, it is the leading manufacturing branch of the industrial sector. Being one of the largest manufacturing and energy-consuming industries, its role is crucial in the transition from fossil fuels to renewable sources. But are low-temperature solar thermal systems (SST) viable in the agri-food industry? Could their regular use provide a boost to meeting the objectives of decarbonisation and reducing carbon dioxide emissions?

A team of researchers from the Polytechnic University of Madrid (UPM) in Spain has attempted to answer these and other questions and has demonstrated the potential of this type of system to achieve a more competitive and efficient industry, reducing energy dependence on third countries.

“In the European Union, the agri-food industry ranks fourth in terms of energy consumption within the industrial sector. A significant part of this consumption is attributed to heating water for multiple operations, such as blanching, smoking, washing, cleaning, etc. Most of this energy supply continues to correspond to fossil fuels, with a limited implementation of solar thermal systems,” explains Fernando R. Mazarrón, from the Higher Technical School of Agricultural, Food and Biosystems Engineering and one of the authors of this study.

With this in mind, the researchers analysed the feasibility of solar thermal systems in nearly 1,300,000 cases related to the agri-food industry, considering a wide range of consumption patterns, economic variables and locations.

The results are encouraging: The average annual energy saved by implementing this type of system varies between values ​​close to 200 kWh/m² of collector for very irregular patterns and 900 kWh/m² for the most regular pattern, with peaks reaching 1400 kWh/m² in the most favourable scenarios. This translates into an average emissions reduction capacity ranging from 28-123 kg CO2eq/m² for electricity and 58-255 kg CO2eq/m² For diesel, with peaks of 400 kg CO2eq/m² in the most favorable scenarios.

“Seasonality of demand, weekly frequency of consumption and energy prices are the factors that most influence the viability of solar thermal systems. Uniformity of daily demand, location and investment cost are also determining factors,” explain the UPM researchers.

Although a significant part of solar energy is captured without concentration, to be used, for example, to generate electricity, as in the case of this solar panel installed on a roof, there are also systems that concentrate solar radiation to generate heat intense enough to be used in processes that require high temperatures. (Photo: Amazings / NCYT)

More energy demand, more profitability

In this sense, the researchers explain, consumption patterns of just one day a week make solar thermal systems unviable in most of the scenarios analysed. However, with just three non-consecutive days, viability increases significantly and in industries with daily demand, payback can be reduced by more than 30% (compared to demand from Monday to Friday).

The type of consumption, in terms of demand hours, is also important when analysing the viability of this type of system. “Viability and profitability are penalised when demand is concentrated in a few hours. The payback in patterns with a peak in consumption in the early morning can double that of a uniform pattern,” says Mazarrón.

How does the price of energy influence the profitability of solar thermal systems? Researchers have the key. With low energy prices, such as those before 2021, low-temperature solar thermal systems would only be viable in very favourable scenarios that combine factors such as high radiation, low investment costs, uniformity of demand and/or high frequency. However, if prices are close to those of the last two years, the number of viable scenarios increases significantly, with attractive returns and significant energy savings.

For the researchers, the importance of this work, recently published in the academic journal Results in Engineering, lies in the fact that “by searching for the scenario with the most similar characteristics, it is possible to estimate the profitability and savings in the use of solar thermal systems in a given industry, as well as the possible variations when changing the assumed variables”, something of great value at a time like the present when the reduction of emissions is key in all industrial sectors. (Source: UPM)