It has been mentioned that the technology used for the solar cooling system makes it possible to produce cooling energy in spite of a varying temperature in the solar collector loop, as long as the temperature difference between the input fluid to the absorption heat pumps and the cooling fluid remains above 50°C. For this reason the control system was set to start giving hot water to the absorption heat pumps when the temperature at solar collector output reaches 60°C and while it is above 50°C. This allows the absorption heat pump to start charging up even if at a slow rate, thus making the most of the available solar energy. Then, when fluid temperature reaches 80 to 90°C and considering that cooling water remains below 30°C the absorption process can charge normally. Once at least one out of the four absorption heat pumps installed in Almeria is fully charged, it can start delivering cool water to the cooling coils. Actually, unlike other absorption chillers, the system used in Almeria is discontinuous. That is to say the machine must first charge before being able to deliver the first cooling kWh. When the first charge cycle is completed and the machines start giving cooling energy, a second barrel charges up. This way, when the first barrel goes empty, the charged second barrel takes over and the first barrel can be charged again. This allows for continuous operation as long as the charging rate is higher than the consumption rate of course. However, the system was designed to start charging as soon as possible in the morning so that the absorption heat pump’s barrels would be fully charged by the end of the morning (between 11 and 12h) when active cooling becomes necessary to maintain adequate thermal comfort in the building. On the other hand, the solar array was designed so that charging rate would always be sufficient to ensure continuous operation of the absorption heat pumps.

5. Conclusion

A solar driven cooling system was presented here, which is one of the first attempts in Spain to integrate a full scale solar cooling system to an office building actually in use. The building is now in its launch phase, so data is not available yet on whether the system is keeping its promises or not regarding energy efficiency. The optimization phase will however be decisive in order to get the system to work to its full potential and achieve the target in terms of energy savings.