Integration of Solar Energy in Small-scale Industries. Application to Microbreweries in Spain

Abstract

In the last two decades the number of small breweries and microbreweries has grown dramatically, representing more than 90% of all breweries in several countries. The brewing process requires heat, cold, and mechanical power, which are mainly provided by gas and electricity. The integration of solar energy to achieve decarbonization in the industry is still incipient. The literature reveals that most studies in this regard are made for medium and large breweries. Likewise, the few cases of solar thermal and photovoltaic integration have been in larger breweries. Therefore, the premise of this thesis is that solar energy integration can also be profitable for small-scale industries under the current market conditions. Initially, in the present thesis an economic prefeasibility study of solar thermal and photovoltaic integration for a microbrewery was carried out for Chile and Spain. Both countries with present high solar resources and differ from each other in the cost of conventional energy (fuels and electricity). The photovoltaic system was profitable for both countries under certain price and solar radiation conditions. The solar thermal system was profitable for Chile in most regions. However, in Spain it was not profitable without subsidies since the price of gas in Spain is much lower than in Chile. For these reasons, it was of interest to know in detail the consumption of a microbrewery to conduct a more detailed study of the use of photovoltaic energy. Thus, a monitoring campaign was carried out to characterize the consumption profile of a microbrewery located in southern Spain. It has been identified that the specific energy consumption per liter of beer may be five times that of a large brewery. In addition, the small-scale components for supplying cold usually operate off-design conditions, and there is no literature information regarding the performance under these conditions. Therefore, during the measurement campaign, data has been collected to adjust the performance curves of these components. Additionally, a simulation tool has been created in TRNSYS that includes the adjusted models of the components. It has been contrasted with measurement data and electricity consumption bills, resulting in a good agreement. The tool may be modified to be used for microbreweries of different sizes or with a different consumption profile. In addition, it can be used for other types of small industries that require cold, heat, and other electrical consumption. The results of the techno-economic analysis carried out in Spain reveal that in any situation a photovoltaic system would be profitable. The cost of energy could be reduced by up to 46.6% for the best solar radiation conditions and market prices. However, in a more moderate scenario where the size of the system is also limited by regulation, the reduction in the cost of energy can vary between 6.7% and 31.5%, for regions with low and high solar radiation respectively. Additionally, the payback periods are between 3.2 and 19.2 years, depending on the level of solar radiation, conventional energy prices, and the size of the PV system. Finally, the contribution of this study to the state of the art begins with the identification of gaps in the literature regarding energy use in small industries. In addition, the on-site monitoring campaign, together with the subsequent adjustment of performance curves, allows identifying the consumption in real conditions for this type of industries. On the other hand, the creation of a simulation tool whose development is explained in detail will allow it to be used and/or adapted for other industries, increasing its potential use. Finally, the economic results seek to demystify the belief that solar energy is expensive and that can only be used in large industries to be profitable. The aim is to move towards decarbonization, in order to meet the objectives of international initiatives against climate change.