## 7 The Use of Renewable Energy in the Dairy Industry
Examples of the integration of solar energy in milk processing include the testing of a low-cost solar concentrator in Amblayo (Argentina) to pasteurize goat's milk at 63 \({}^{\circ}\)C for 30 min. The system used a Fresnel-type concentrator to produce steam from sunlight, which was then injected into the pasteurization device. The condensation of steam and the consequent transfer of latent heat were used to heat the water used for the pasteurization of milk in a double-wall tank. The design of the concentrator was optimized for ease of use and the efficient manual tracking of sunlight, reducing the need for automatic systems. The experimental results indicated that such a system could pasteurize 10 L of milk per hour [58]. A parabolic trough collector was used for indirect steam production in Tunisia. It included four main components: (i) a reflector; (ii) a receiver--a vacuum tube coated with glass; (iii) a sun-tracking system, and (iv) hydraulic circuits. The incident radiation on the collector surface was reflected and concentrated onto the absorber, then the heat transfer between oil and water was conducted to attain the high temperature required for steam generation. The thermal energy efficiency varied from 22% to 32% and presented a maximum capacity of 8 kg steam/h [59]. [PERSON] and [PERSON] [60] also developed a system for HTST pasteurization based on low-pressure solar panels to be used in small villages in Tanzania, presenting a working capacity up to 1000 L milk per day. The integration of solar thermal energy in a dairy plant has also been tested in the Basque Country (Spain). The aim was to replace the use of conventional fossil fuels in processes requiring low-to-medium temperatures. The Pinch analysis was used to assess the energy demands of the dairy process and to identify opportunities for optimization, concluding that a solar thermal system could significantly reduce natural gas consumption, with potential savings of up to 27.7% [56]. These strategies align with broader environmental policies, such as the European Green Deal [61], which promotes climate neutrality by 2050 and encourages the reduction of GHG emissions across all sectors, including agriculture and food processing. They are also consistent with the objectives of the EU Farm to Fork Strategy [62] and support compliance with emerging carbon pricing frameworks. Some studies have focused on the effective utilization of renewable energy for cooling processes, where the integration of conventional vapor-compression cycles with photovoltaic panels offers an interesting solution for cooling applications. A comparative study conducted by [PERSON] et al. [63] in Pakistan aimed to create a solar-driven milk chilling unit, operating with a 2 kW photovoltaic system, and assessing its performance with different types of compressors. The energy consumption for reciprocating, rotary with capacitor, and rotary with variable refrigerant flow compressors was noted as 1.8 kW, 1.2 kW, and 0.8 kW, respectively. The findings demonstrated that cooling a 200 L batch of milk to the desired temperature (4 \({}^{\circ}\)C) needed less than 1 kW of power by extracting heat energy from the system utilizing a vapor-compression refrigeration system with variable refrigerant flow technology. Technological progress has generated efficient and cost-effective renewable energy options. Solar systems, including photovoltaic, represent a substantial fraction of renewable energy installations in the dairy sector. They are recognized as a proven technology with reasonable costs; straightforward incorporation into existing facilities; and, in some countries, with financial incentives [64]. A suitable infrastructure is crucial for the integration of renewable energies in industrial processes. However, in some sectors this can present considerable difficulties, as forming a connection might be challenging.