 |
Solar Combi + Newsletter
Issue 3 (February 2010)
|
 |
What is a Solar Combi plus system?
Solar combi plus systems use heat from solar thermal collectors to provide heating in winter, cooling in summer and domestic hot water all year round. The figure sketches the main components, which make up a typical system: (i) the solar thermal collector, (ii) a storage tank can either be installed on the hot side, on the cold side or on both, (iii) a domestic hot water preparation unit, (iv) the sorption chiller, (v) heat rejection at intermediate temperature (30-40°C), (vi) the cold distribution system and (vii) the heat distribution. You can find more details here.
|
 |
Standard System Configurations
Aim of the project presented 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 (see the figures). Within the basic systems, a number of parameters were varied:
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. 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. You can find more details about standard system configurations here.
|
 |
Online Tool
Standard system configurations reduce the design effort for single applications considerably, since sizes and layouts are stated. To identify and promote such configurations a user friendly online tool was developed to disseminate the main results of a number of simulated case studies selected through economical and ecological ratings, for different typical working conditions (i.e. application, climate, etc.).
The structure of the tool is divided into input values selected by the user (location, application, cold distribution system, heat rejection system, solar collector type) and output values given by the database (total solar fraction, cooling solar fraction, relative primary energy saved, specific primary energy saved, total electric efficiency, gross solar yield). No direct comparison between industry partner chillers is deliberately presented but the user through different configurations can use different chillers. The effects of different technological options are easily manageable by professionals and end users as a function of the system size. The standard configurations were the basis for the development of package solutions by the participating sorption chiller producers and system suppliers. More informatuion here.
The online tool is available under: http://wis.eurac.edu/solarcombiplus/
|
|
|
Recommendations on System Design
Large Collector Areas Perform Best
Well-sized systems have a collector size of about 4 to 5 m²/kW reference chilling capacity and a hot storage volume of 50 to 75l/m² aperture area.
Implement Optimized Control Algorithm
The control strategy influences the performance of the system considerable in terms of both solar fractions and primary energy consumption. Especially the control of pumps and the heat rejection fan must be studied.
Use Chilled Ceiling Distribution Systems
Chilled ceiling systems are more favorable compared to fan coil systems in terms of chiller performance due to a higher temperature level in the chilled water circuit.
Consider Solar Autonomous System for Cooling
To maximize primary energy savings it should always be considered to design a system without fossil backup heater for cooling in summer. Other options to reduce fossil fuel consumption are to install a biomass boiler or to use waste heat as heat backup system or an electrically driven compression chiller as cold backup. Click here for more information.
|
Industry participation
A number of producers of small-scale solar driven sorption chillers / suppliers of solar heating and cooling systems are direct partners in this project. Please check their homepages for more information on their products
For more information on the project please contact the Project Coordinator
European Academy (EURAC) www.eurac.edu
Roberto Fedrizzi
Viale Druso 1
I-39100 Bolzano
Italy
Or your local Institutional project partner