The state-of-the-art investigation proved that a large market is not yet reached actually. This is due to the high price of the technology. The state-of-the-art has shown that the technology is not yet embedded in the most energy effective places or in the most promising buildings.

Therefore, the existing solar cooling plants show a high cost reduction potential for next generation of solar cooling plants resulting from application on most promising buildings, lower prices of the main components (chillers, solar collectors), proper system configuration, well trained designer, installer and maintenance responsible people.

3.1 Conclusions of high-potential building sectors and applications

The conclusions of the analysis of for most promising cases with absorption systems are the following:

— The EU country with most cases of low costs of primary energy savings is Spain. Esfahan has also a very promising situation. In both cases the availability of solar irradiation as well as the combination of cooling and heating demand is very favourable for a good performance of the solar cooling plants. Besides that, the case of Esfahan has the advantage of low prices of gas. Mexico has similar cases to others in Spain or Esfahan. The other EU country, ordering by criteria of the most promising opportunities for cost reduction, is France, with cases very similar to the ones in Spain, and finally, Austria, where the cost of primary energy savings mainly take the higher values.

— In spite of this general conclusion, some cases have lower costs in France than in Spain, for instance a hotel in Lyon-B3 than a office in Madrid-C1. It means that in some cases, the influence of daily and monthly profile of the demand has more influence than the solar irradiation on the performance and economic results of a solar cooling plant.

— By ordering the results from the minimum to the maximum value for costs of primary energy savings per each country, the different cases have been nearly ordered in groups by the type of building. This shows that the cases with low costs of primary energy savings are hospitals

and hotels. Those are followed by offices and trade centres. Finally, the most unfavourable cases are residential. The table 4 shows the cases with lower value of this parameter, that varies between 0.11 and 0.14 €/kWh_PE, with primary energy savings between 15 % and 25 %.

name	PE savings	Cost PE unit
ESPmalagaA1V	21%	0.11
ESPmalagaA3N	24%	0.11
WesfahanA3N	19%	0.11
E SPm adridA3N	19%	0.12
WesfahanB4N	20%	0.13
ESPbarcelonaA2M	18%	0.14
ESPmadridB4N	17%	0.14
ESPmadridA1V	15%	0.14
ESPmadridB2N	20%	0.14
FRAperpignanB3V	17%	0.14

table 4. Most promising cases for costs reduction of solar cooling systems AB+FPC

The conclusions of the analysis of for most promising cases with desiccant systems are the following:

— The level of costs of primary energy savings is much lower in the analyses cases with desiccant technology than with absorption technology, therefore the values range here from <0,04 €/kWh_PE to >0,12 €/kWh_PE.

— By ordering the results from the minimum to the maximum value for costs of primary energy savings per each country, the different cases also have been ordered nearly in groups by the type of building. This shows that the cases with low costs of primary energy savings are hospitals and hotels. Those are followed by trade centres and offices. The table 5 shows the cases with lower value of this parameter, that varies between 0.01 and 0.03 €/kWh_PE, with primary energy savings between 19 % and 40 %. The best case here is the hospital in Malaga (VEE) with 40% primary energy savings by only costs of primary energy savings of 0,01 €/kWh PE.

name	PE savings	Cost PE unit
AUgrazA1V	19%	0.01
AUviennaA1V	21%	0.01
AUgrazB4N	21%	0.02
AUgrazB3V	22%	0.02
AUviennaB4N	21%	0.02
AUviennaB3V	23%	0.02
FRperpignanB3V	33%	0.01
FRperpignanA1V	33%	0.02
FRlyonB3V	25%	0.03
FRnantesA1V	26%	0.03

ESPmadridA1V	37%	0.01
ESPmalagaA1V	40%	0.01
ESPbilbaoA1V	27%	0.02

table 5. Most promising cases for costs reduction of solar cooling systems DEC+FPC 3.3 Conclusions of RTD Gaps, Potentials and Topics

Concerning the ideal specification for components it can be concluded that there are some significant technical specification related to solar-assisted cooling which are not taken into account in the existing installations. These specifications lead to a better energy performance of the whole system and are in some cases obligatory to achieve high energy saving ratios in comparison to conventional cooling systems (e. g. cooling tower, air-conditioning devices).

The technological gaps refer besides the necessary technological improvement of each component also to the requirements for better system integration of each part of the solar — assisted cooling system. To solve the gap of reliability the focus on improved control systems as well as design and engineering will be important in the future.

The cost reduction potential of each single component of solar-assisted cooling systems ranges from 2-15% using feasible short-term and medium-term technology development scenarios. The highest influence on cost reduction of the whole system has the solar collector field with 15% by cost reduction of 30%. To get a cost-competitive situation of solar-assisted cooling systems towards conventional systems two cases would have the highest influence: increase in energy prices and subsidies.

For thermally driven chillers (absorption, adsorption) the efforts for cost reduction must be very strong in each part of the system and the frame conditions as energy prices and subsidies must improve, otherwise for short-term and medium-term a cost-competitiveness of that technology in comparison to conventional cooling can not be achieved. The cost situation of desiccant evaporative cooling systems is much better; here the generally limited field of application on air-based cooling systems and a lack of reliability due to gaps in sophisticated control systems, engineering and maintenance seem to be the main barriers for market penetration.

The expert workshops for market penetration made clear that a lot of tasks are necessary to do, not only on technology development, but also on customer-specific preparation of the whole topic by setting up information material, realisation of demonstration sites and getting package solutions. The supplier of the solar-assisted cooling plants which are mainly engineering consultants and executive companies will also need support by training, pre-selection tools, planning tools, pre-defined control strategies and monitoring data of running installations. Besides solar-assisted cooling, there are also some other sustainable cooling technologies in the market as passive cooling, geothermal usage, biomass and district cooling. It has to be evaluated in a proper way by a comparison of technologies, which positions solar-assisted cooling could have in the rapid rising cooling demand in buildings. A roadmap for solar — assisted cooling systems on national levels and on European level should be one of the next tasks in that field. The future topics in the field of solar-assisted cooling will have a very big range from technology development and demonstration sites to market implementation activities, training and dissemination.

4. Contributors

Partners in ROCOCO project are:

— ARSENAL RESEARCH, Austrian independent public research company in the field of renewable energy, www. arsenal. ac. at

AIGUASOL, planning and consultancy private company in the field of energy efficiency and particularly solar energy, www. aiguasol. com

— CONNESS, Austrian consulting and project planning company with focus on renewable energy and energy efficiency, www. conness. at

— GMI, Austrian planning and realization of building-climatic concepts company, www. teamgmi. at

— TECSOL, French technical engineering and project management office specialized in solar energy for buildings, www. tecsol. fr

— FOTOTERM, Spanish solar thermal system installer, www. fototerm. com

— HSF, French air-cooling/heating system and hydraulic equipment installation, management and maintenance company for buildings and industry, www. stihle-freres. fr

Glossary

Absorption

Adsorption

Desiccant Evaporative Cooling technology

Domestic Hot Water

Flat plate collectors

Evacuated tube collector

Flat plate collectors

Primary Energy

Reference

Research and Technology Development Solar-assisted Cooling Total Annualized Cost Technology and Market sector

References

[1] TRNSYS, Transient System Simulation Program, Solar Energy Laboratory, University of Wisconsin Madison, Version 15.09, 2001