1. Introduction

The combined use of solar energy for heating and cooling has the potential to upgrade solar thermal energy from mainly DHW provider to a major building energy supplier [1, 2]. The necessary sorption chillers, however, used to be available mainly in higher power range [3], but now several new small-scale sorption chillers are being offered. They will open the market for small solar thermal systems for combined space heating, domestic hot water and space cooling (so-called solar combi plus systems).

The aim of the IEE  funded project “Solar Combi+” is to take these newly commercially available small-scale sorption chillers and identify and promote standardised solar combi plus systems for small applications (residential, catering, small commercial and office buildings, up to a cooling demand of 20 kW).

Now is the right moment to support the market entry of solar combi plus systems with reliable dimensioning and a comprehensive analysis of promising applications. In this way the market introduction solar combi plus systems can go hand in hand with the build up of important solar thermal markets e.g. in Spain, France and Italy [4]. Air conditioning systems are state of the art in office and commercial buildings not only in southern countries but all over Europe, and comfort requirements in the residential sector are growing constantly.

The participation of all European producers of small-scale solar driven sorption chillers as direct partners as well as the declaration of interest of the solar thermal industry, shows the importance of the project for a smooth and sustainable market entry solar combi plus systems.

2. Solar Combi Plus systems

Fig. 1. Example for the system components of a Solar Combi + System

Solar combi plus systems use heat from solar thermal collectors to provide heating in winter, cooling in summer and domestic hot water all the year round. Fig. 1 sketches the main components, which make up a typical system: (i) the solar thermal collector to provide the heat usually backed up by an auxiliary heat source, (ii) a storage tank can either be installed on the hot side, as shown in the figure, on the cold side or on both, (iii) a domestic hot water preparation unit, (iv) the sorption chiller is fed with hot water (70-100°C), (v) heat rejection at intermediate temperature (30-40°C) to a cooling tower (dry or wet) or another heat sink (e.g. a swimming pool), (vi) the cold distribution system (e.g. a chilled ceiling, fan-coils or air handling units) and (vii) the heat distribution (preferably a low temperature system).
All components of a system are now market available: But there are so far very few providers of system solutions, and that’s the starting point of the project

3. Addressed barriers and offered solutions

The most important barriers for a broad application of small-scale combined solar heating and cooling systems and the solutions proposed by the project to overcome them are as follows:

1. Combined solar heating and cooling needs specialised design in order to make the single components play together optimally. So far every single system is designed from scratch. This (i) leads to a financial effort, which is not feasible for small applications, as design costs become prohibitively high in relation to hardware costs and (ii) often might overstrain the solar thermal installer, who would in most cases be the provider of the system to the end-user. Today there are no design guidelines for small-scale systems and very few, yet not validated, package solutions on the market.

• Virtual case studies will overcome this gap: Promising configurations will be identified, simulated for different typical conditions (i.e. utilization, climate, building type) and finally economically and ecologically rated. Out of the large number of virtual case studies, a small number of standard system configurations, which work best under different conditions are identified. Based on these, small-scale sorption chiller and solar thermal industry will be able to provide consistent package solutions. These will enable planers and independent craftsmen to install reliable systems.
  

2. Small scale sorption chillers are expensive as production volumes are currently low.

• The economical and ecological rating of the above described virtual case studies will allow identifying the most promising markets, where systems are yet at the edge of economical breakeven point or beyond, compared to traditional solutions. Accordingly tailored promotion and market strategies will considerably trigger the application of the technology. Following economies of scale will make small-scale combined solar heating & cooling less expensive and thus viable in a broader range of applications and climates.
  

3. Small scale combined solar heating & cooling is not well known to traditional small-scale solar thermal installers, planners, architects and potential clients.

• Tailored dissemination plans include among other measures the training of solar thermal installers, targeted presentations to professionals, information of the public in most promising regions as well as advice to policy makers and promotion of pilot plant installation to public authorities.
  

4. Solar Combi + work plan

4.1. Market analysis

The market analysis provides an in depth analysis of markets for small-scale solar combi plus systems and serves as a basis for the definition of the cases to be studied. It is performed on three pillars: (i) small scale chillers, (ii) solar thermal applications and (iii) consumers. The ecologically and economically rated case studies are on the other hand the basis for a SWOT analysis, the examination of market shares and the definition of goals.

4.2. Virtual case studies

Based on the results of the market analysis and on the experience with already installed systems, promising configurations will be identified, simulated for different typical conditions (i.e. utiliza¬tion, climate, building type) and finally economically and ecologically rated.

4.3. Evaluation of virtual case studies

Out of the large number of virtual case studies, a number of standard system configurations, which work best under different conditions, is identified. Based on these, the industry partners will provide consistent package solutions. These will enable planners and independent craftsmen to install reliable systems. The economical and ecological rating of the virtual case studies will also allow identifying the most promising markets, where systems are yet at the edge of economical breakeven point or beyond. Last but not least the results of the virtual case studies will be made available online with an easy to handle web-based tool, which can query it under different aspects.

4.4. Training on package solutions

Special training courses for solar thermal installers on standard system configurations and package solutions will be prepared and 15 pilot courses will be evaluated. Target group are (solar thermal) installers, because the goal of the packaged solutions is to avoid the need of engineering.

4.5. Dissemination, communication and training

Tailored dissemination, communication and training plans were elaborated to reach the different key actors. They include besides the presentation of results at relevant conferences and trade fairs addressing a wider audience (i) the dissemination of both the elaborated brochure and the online tool to query the virtual study cases towards professional groups (HVAC planners, architects, engineers, building industry), through their interest groups and associations (e.g. ESTIF, ECTP, chambers), where possible on the occasion of annual meetings or in synergy with related national and international projects, (ii) the provision of information and advice to (national) authorities on the potential of solar combi plus systems with the aim to include it in support programs and (iii) the approach of local authorities in promising regions promoting pilot installations. Finally, information through public media in the most promising regions should give an important push to market entry. On the website all public deliverables will be available for download and most attention is given to the integration of the webpage in the existing information network on solar heating in general and specifically combined solar heating and cooling.

Fig. 2 Structure of the work plan

Bibliography

[1] European Solar Thermal Industry Federation – ESTIF (2003): Sun in Action II - A Solar Thermal Strategy for Europe, Bruxelles
[2] Initiator group of ESTTP (2006) Solar Thermal Vision 2030, Brussels
[3] Henning, H-M. (Ed.) (2004), Solar Assisted Air Conditioning in Buildings – Handbook for Planners. Springer-Verlag, Wien, New York
[4] European Solar Thermal Industry Federation – ESTIF (2005): Solar thermal markets in Europe, Trends and statistics, Bruxelles