Solar thermal energy generates heat for space heating, sanitary warm water production and industrial processes. With heat making up 50% of the global energy demand, solar-thermal technology plays a significant role in the future energy mix regarding heat generation and reducing carbon emissions.

However – as with other technologies – good standards in designing, constructing, and operating solar-thermal plants are key to create cost-efficient solutions and maximize the usable energy output over their long lifetime. Providing consistent high quality system performance will also increase the image and utilization of the solar-thermal technology.

Hence, this report aims to help plant designers and operators by providing checklists with critical aspects and questions for each stage of a solar-thermal plant’s lifetime (from project idea to decommissioning). The report is aimed at different actors for each phase, from project developers to plant operators.

This report, developed as part of the International Energy Agency’s (IEA) Technology Collaboration Program (TCP) Task 68 on Efficient Solar District Heating Systems, presents an expert-based analysis of cost reduction mechanisms (CRMs) for Solar District Heating (SDH) systems. The focus is on quantifying future reductions in capital expenditures (CAPEX), operational expenditures (OPEX), and the Levelised Cost of Heat (LCoH), while considering the impact from technological development, scientific development, and yield improvements across different project phases.

The target audience for this report is quite broad: all players in the energy transition should become aware of the potential role that solar thermal district heating may play. Special focus is on policy and decision makers, city planners, energy modellers, local, regional and national governments and technology specialists. One of the underlying reasons to be transparent on SDH costs is that this report is designed to be an aid to decision makers who need to make robust plans, projections and energy transition policies. It may help energy modelers in determining the competitiveness of solar thermal and to see the effect of policy measures.

Large solar heating installations can have a significant contribution to renewable heat supply in many countries. It is a renewable technology without direct CO2-emissions, which can have various basic system layouts:

1. Directly providing heat to an end-user, through residential, commercial or industrial installations.
2. Indirectly providing heat to many end-users through a solar district heating (SDH) network.
3. Indirectly providing heat through a SDH network with seasonal heat storage and a heat pump.

In all three system layouts solar thermal heat is competing with a conventional heat supply, which may require additional support for the solar option, depending on the local climate and technical configuration. As solar thermal is a renewable technology without direct CO2-emissions, countries may decide to apply generic or specific support policies.