IEA SHC Programme experts gather in Slovakia to shape future of CO2-free heat

A milestone for the Slovak Innovation and Energy Agency: for the first time, SIEA hosted a meeting of an IEA Technology Collaboration Programme. The Executive Committee (ExCo) of the IEA Solar Heating & Cooling Programme convened in Bratislava, the Slovakian capital, for a three-day session at the beginning of June. During this strategic meeting, Lucio Mesquita from Canada (first from left) was confirmed for another two-year term as Programme Chair. The ExCo also approved the launch of a new research initiative called Task 74 on Thermal Energy Storage Components. The gathering included a valuable exchange with Slovak scientists and industry representatives. The collector manufacturer and system provider Thermosolar impressed the guests with its high level of vertical integration and diverse customer groups.
Photo: IEA SHC

“The transformation of heat supply towards climate neutrality presents major challenges”, emphasized Mesquita. “Our global research network of more than 200 experts is working to develop and analyze CO2-free heat systems that combine solar technologies with storage and other renewable energy technologies.” The IEA SHC focuses on various heat user groups, including housing associations, district heating network operators and industrial customers.

A key strength of the IEA SHC Programme is its collaborative approach: scientists work across institutional and national boundaries on common topics and questions. Together, they improve quality standards, optimize planning tools, harmonize test procedures, share insights from flagship projects in different countries and evaluate performance data from existing installations.

Currently, 20 countries, the European Commission and nine international organizations are members of the IEA SHC. ExCo meetings, held twice a year, rotate between the participating countries and organizations. Slovakia has been a member since 2019 and hosted the IEA SHC ExCo meeting for the first time.

“We received strong support from SIEA in organizing the meeting,” said Dr. Eduard Jambor, who represents Slovakia in the ExCo as an expert consultant on behalf of SIEA. The agency has 360 employees and 93 international partners. Lucia Bogdány, Head of SIEA’s International Cooperation Department, presented two key SIEA initiatives during the meeting: “We monitor data from over 16,000 entities – including energy audits of large companies, inspections of heating and cooling systems, and performance results from cogeneration plants”, she explained.

Eligible technologies within the Green Households subsidy scheme administered by SIEA. The maximum capacity and grant contribution varies depending on the technology. Source: SIEA

Secondly, SIEA administers the Green Households (Zelená domácnostiam) subsidy scheme that supported the installation of more than 88,000 systems in two periods (see following table).

The subsidies cover up to 50 % of the eligible costs of small-scale renewable energy systems such as PV panels, biomass boilers, heat pumps and solar thermal collectors. SIEA has sent out vouchers for grants adding up to EUR 108 million.

In the first period from 2015 to 2023, altogether 14,516 solar water heaters were subsidized, 25 % of the total number of grants. In the second period only 4 % of all grants were allocated for solar collector systems. Jambor sees the reasons for the sharp drop in the proportion of subsidised solar thermal systems since 2023 as the great popularity of heat pumps and PV systems, which is also triggered by intensive marketing by technology providers. PV systems have become increasingly appealing due to the option of utilizing a virtual battery. This allows surplus solar energy generated during the day to be stored virtually in the grid, making it available for use later in the evening when demand is higher. This approach eliminates the need for a physical battery, reducing overall investment costs.

Number of successful applications per technology within the Green Households subsidy scheme Source: SIEA

Bogdány also mentioned two sub-programmes: EUR 28.4 million is available within the Green Solidarity programme to support low-income households, which are at risk of energy poverty. Furthermore, businesses can apply for up to EUR 50,000 within the Green Business programme. PV, solar thermal, heat pumps, wind turbines and storage are among the eligible technologies here.

Solar-assisted hot water on the roof of a dormitory building of Slovak University of Agriculture in Nitra, around one hour away from Bratislava. Photo: Solrico

Thermosolar delivers reliable solar heat for Slovak dormitories

Solar Heat Europe, the Brussels-based association for solar industrial heat, estimated that approximately 15,000 m² of collector area was installed in 2023. One key technology provider contributing to this volume is Thermosolar. In addition to serving residential buildings, the company develops solar thermal systems for businesses, dormitories, hospitals, and schools in Slovakia. Since 2022, Thermosolar has been part of the Austrian Hargassner Group, a global leader in biomass boiler technology.

The ExCo group visited a Thermosolar installation at the University of Agriculture in Nitra, where 90 m² of TS500 collectors supply heat to a 4 m³ storage tank integrated with the existing gas boiler system (see photo above). When solar energy provides temperatures above 55 °C, the heat is fed directly into the hot water distribution system of the student dormitories. During periods of lower solar input, the system preheats the water for the gas boilers. The building supervisors report high satisfaction with the solar thermal system, which has been in reliable operation since 2022.

Patented mechanical connection between the copper tube and the absorber sheet of Thermosolar collectors Photos: Thermosolar

Efficient solar-assisted heat pump system

Thermosolar manufactures its solar collectors in Ziar nad Hronom, approximately 1.5 hours east of Bratislava. During the meeting, Marián Ježo, Technical and Commercial Consultant at Thermosolar, highlighted the company’s high level of vertical integration in its production process. The facility electroplates preformed aluminium sheets in-house before bending them around copper pipes. Thermosolar employs a patented mechanical connection that ensures maximum contact—and therefore optimal heat transfer—between the pipe and the absorber (see photos above).

According to Ježo, Thermosolar sells a significant number of solar systems in combination with brine/geothermal heat pumps. In these systems, evacuated flat plate collectors serve as the heat source for a brine heat pump. The solar heat can be used directly to cover domestic hot water or space heating needs, or it can support heat pump operation by preheating the brine tank.

The heat pump, in turn, cools the brine tank, resulting in return temperatures ranging from 5 °C to 15 °C in the collector loop. These low return temperatures enhance collector efficiency and reduce the necessary input from the geothermal part to a minimum. Thanks to the evacuated space within the collectors, condensation does not occur, even at such low operating temperatures.

Websites of organizations mentioned in this news article:
IEA SHC Programme: https://www.iea-shc.org/
Slovak Innovation and Energy Agency – SIEA: https://www.siea.sk/
Green Households: https://zelenadomacnostiam.sk/
Thermosolar: https://www.thermosolar.sk/en/