Options for solar-assisted refrigeration - trough collectors and double-effect chillers

A system often discussed in the available literature is that of a single-effect lithium bromide chiller and a fixed solar collector. An analysis of published articles showed that prototype trough and evacuated flat plate collectors can efficiently produce liquids hot enough to drive double-effect chillers. Our goal was to assess the potential of new chiller-collector combinations to substantially reduce requirements for gas-firing. We simulated systems with a collector, starting with the well-known combination of single-effect chiller and flat plate. For a scenario with a July day in Algiers, we found a 'break-even' point at a daily average of 50 kW refrigeration demand; here the gas consumption was no more favourable than that of a double-effect chiller. We simulated three more systems, with either single or double effects and either evacuated flat plate or trough collectors. Compared to double-effect chillers, potential savings were large: 39% for a combination of single-effect chiller and trough collector; 32% for double-effect chiller and flat-plate collector; 86% for double-effect chiller and trough collector. Even for locations as far north as Oslo large solar fractions of 67% were possible (double-effect chiller and trough collector).