Standard System Configurations

Aim of the project is the definition of a reduced number of system configurations, which can be promoted and applied similarly to the standardized systems for domestic hot water production, which work reasonably well in common applications‏ and are independent of the specific products considered.
An extensive campaign of numerical simulations was carried out on two basic plant configurations detected through market and technical analysis. Each industrial partner of the consortium opted for one of the plant layouts represented in figures shown below, which suites best the working features of its own chiller. Within the basic systems, a number of parameters were varied:

• Geographical location of the solar combi+ plant
• Building in which the solar combi+ plant is installed
• Chiller brand.
• Collectors’ type (flat plate, evacuated tube collectors)
• Heat rejection system’s type (wet cooling tower, dry air cooler and hybrid cooler)
• Chilled/Warm water distribution system (fan coils and chilled ceiling).
• Collectors’ area between 2 and 5 m²/kWRef. Pow. cold
• Warm water storage volume between 25 and 75 l/m² collectors’ area

For each set of variables examined, three best configurations were extracted that maximize each of the benchmarks mentioned. The analysis shows that the size of 5 m2/kW and 75 l/m2 for collectors’ field and buffer tank respectively allow the best performance in all situations considered. These sizes are slightly higher than typically found in solar cooling systems (cooling only environment), in which the area of the collectors is about a 4 m2/kW; in the case treated, in fact, the winter heating requires the use of greater proportions. Larger areas (up to 7 m2/kW) would lead to slightly better results, hardly justified because of strongly increased investment costs (+10 ÷ 15%).
In general, plants characterized by better performance are those relating to applications where high solar radiation is combined with high summer cooling loads and moderate needs for heating and production of domestic hot water. In the most profitable cases, total solar fraction of 80%, together with primary energy savings in the order of 60% were found.
The parameters that most affect system performance are the type of collectors and the heat rejection system. The vacuum tubes collectors allow higher primary energy savings than those obtained with flat plate collectors (on average +15 ÷ 30%) due to the higher temperatures achievable. This increase is paid through a substantial increase in investment costs.
More information about the Standard Configurations study can be found at XXX.