But are low-temperature solar thermal (SST) systems viable in the agri-food industry? Could their widespread use significantly boost the achievement of decarbonization and CO2 emission reduction targets?

A team of researchers from the Polytechnic University of Madrid (UPM) has tried 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 energy consumption within the industrial sector. A significant portion of this consumption is attributed to water heating for multiple operations, such as scalding, smoking, washing, cleaning, etc. Most of this energy supply still comes from fossil fuels, with limited implementation of solar thermal systems (STS),” 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 analyzed the feasibility of SSTs 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 savings achieved by implementing these systems ranges from approximately 200 kWh/m² of collector area for highly irregular patterns to 900 kWh/m² for the most regular pattern, with peaks reaching 1400 kWh/m² in the most favorable 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.

“The seasonality of demand, the weekly frequency of consumption, and energy prices are the factors that most influence the viability of the SST. The uniformity of daily demand, location, and the cost of investment are also determining factors,” explain the UPM researchers.

The higher the energy demand, the higher the profitability

In this regard, the researchers explain that single-day-a-week consumption patterns make SSTs unfeasible in most of the scenarios analyzed. However, with just three non-consecutive days, feasibility increases significantly, and in industries with daily demand, payback can be reduced by more than 30% (compared to Monday-to-Friday demand).

The type of consumption, in terms of peak demand hours, is also important when analyzing the viability of these systems. “Viability and profitability are negatively impacted when demand is concentrated in just a few hours. The payback period for patterns with a peak consumption in the early morning can be double that of a uniform pattern,” Mazarrón explains.

How does energy price influence the profitability of solar thermal systems? Researchers have the key. With low energy prices, like those before 2021, low-temperature solar thermal systems would only be viable in very favorable scenarios that combine factors such as high radiation, low investment costs, uniform 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 Results in Engineering, lies in the fact that "by looking for the scenario with the most similar characteristics, it is possible to estimate the profitability and savings of SST 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.