Task 45
Task 45
SHC Task 45

Large Scale Solar Heating and Cooling Systems

Project (Task) Subtasks

The objectives shall be achieved by the participants in the following Subtasks:

The tasks of dissemination of results and market support are included in the Operating Agent's general task.

In the following the specific objectives, activities and deliverables of the subtasks are described in more detail.

Subtask A: Collectors and collector loop

The general objectives of Subtask A are to:

  • Assure use of suitable components
  • Assure proper and safe installation - including compatibility with district heating and cooling network
  • Assure the performance of the collector field

The specific objectives of Subtask A are to:

  • Improve use/accuracy of collector test results - pre-normative work
  • Propose requirements for collector loop pipes (safety, durability, heat loss) - pre-normative work. Propose test methods for pipes accordingly
  • Propose requirements for collector loop installation including precautions for safety and expansion. Propose check list for checking installation accordingly
  • Develop and validate simulation model for the thermal behaviour of solar collector fields
  • Check thermal performance of already installed solar collector fields
  • Prepare guidelines for design, control and operation of solar collector fields
  • Propose procedure for guaranteeing performance of collector field installation - incl. heat exchanger
  • Propose procedure for checking guarantee of collector field installation incl. heat exchanger accordingly
  • Improve cost /performance ratio for roof/building integrated collector fields
  • Improve cost /performance ratio for ground mounted collector fields

The activities to reach these objectives are defined below.

A1: Improve use and accuracy of collector test results

A special problem for large collector fields has shown up:

  • The test conditions used during collector tests are different from the operation conditions for the solar collectors in a solar collector field.

The volume flow rate through the collector, the collector tilt, the solar collector fluid and the wind velocity along the collector, the diffuse part of the radiation might be different during the collector test and the operation of the collector. The collector efficiency expression will therefore be different during collector operation than during the collector test. Further, the influence of changes of the mentioned conditions on the collector efficiency expression is different from collector type to collector type - for instance for flat plate collectors with one and with two covers. It is therefore proposed to investigate how the efficiency expression is influenced by the mentioned conditions for different solar collectors.

The results of these investigations can be used for corrections of test values to "real conditions" - and to improve test accuracy by restricting variability of test conditions

In this way a good basis for a more precise and fair comparison of different solar collectors can be established. The research will, if possible, be carried out in cooperation with participants of the IEA Solar Heating & Cooling Programme Task 43 project Solar Rating and Certification Procedure. Advanced Solar Thermal Testing and Characterization for Certification of Collectors and Systems.

A2: Requirements and test methods for collector loop pipes

Investigations on requirements and test methods on durability of pipes for solar collector loops will be carried out. Among other things, thermal expansion, corrosion and boiling behaviour with different solar collector fluids will be studied.

Consider EN 13941, EN 235, which changes are needed?

A3: Requirements to hydralic design of collectors and collector fields

Parallel theoretical and experimental investigations on the flow distribution for different rows of serial connected solar collectors will be carried out for differently designed solar collector fields with different piping systems and circulation pumps.


  • applicable hydraulic design of collectors
  • flow distribution in parallel absorber pipes, collectors and collector groups
  • uniform distribution of  flow rates in overall collector area with less regulation valves
  • pipe heat losses

Detailed simulation models to determine the thermal performance of solar collector fields will be developed and validated by means of measurements. The models will among other things include collector efficiency expressions for different collectors with different volume flow rates, for different collector tilts and for different solar collector fluids, heat loss from pipes, and shadows from one collector row to the next collector row. Solar collector fields consisting of different collector types will be considered. The models can be used to determine the suitability of differently designed solar collector fields and different operation strategies.

The thermal performance of existing solar collector fields will be compared to calculated thermal performances with the model.

Further, simulation models on the pressure drop for differently designed solar collector fields will be developed and validated by means of measurements. 

Based on the above-mentioned investigations and on calculations with the model guidelines for design, control and operation of solar collector fields will be worked out.

Models will focus on flat plate collectors and temperatures below 100 oC - experience exchange with future task on industrial applications focusing on high temperature applications will be organised.

A4: Precautions for safety and expansion

"Thermal expansion and stagnation behaviour and measures to handle stagnation".

The solar collector loop design will also be investigated with focus on air escape, thermal expansion of solar collector fluid.

A5: Guaranteed performance of the collector loop

A procedure for how to guarantee and check the performance of collector field and heat exchanger will be elaborated and tried out on existing plants.

A6: Cost/performance improvement

Investigations with focus on reduction of the cost/performance ratio for building integrated as well as ground mounted solar collector fields inclusive the applied control and operation strategies will be carried out

Subtask B: Storages

The Subtask B will focus on large storages (> 1 000 m3 water equivalent) in combination with solar heating and cooling systems using sensible storage materials.

It is anticipated that there is a high potential for optimisation of storage efficiency and economy in system integration.

The general objectives of Subtask B are to:

  • Improve the economy of (seasonal) storage technologies
  • Increase knowledge on durability, reliability and performance of (seasonal) storage technologies
  • Demonstrate cost effective, reliable and efficient seasonal storage of thermal energy

The specific objectives of Subtask B are to:

  • Evaluate existing storages
  • Define requirements for efficient storages and "storage sub components" - structural loads, durability, tightness, insulation, stratification, high temperature capability, safety, etc.
  • Define system requirements for efficient storages (temperature levels, hydraulics, control strategies etc)
  • Identify the needs for technical improvements
  • Define the quality measures - procedure for checking the performance of storages (heat loss, stratification, etc.)
  • Design guidelines for cost-effective storages

The activities to reach these objectives are defined below.

B1: State of the art: Evaluation of existing projects

B1.1.      Definition of selected pilot and research projects to be evaluated by national participants.

B1.2.      Evaluation based on questionnaire

B1.3.      Overview analyses of pilot projects and storage developments: main findings, constructions and materials to be recommended, problems found.

B1.4.      Cost analyses of construction technologies and materials.

B1.5.      Cost for operation and maintenance.

B1.6.      System interaction.

B2: Technical improvements

Identification of necessary developments/improvements.

Collection of possible improvements, new concepts, materials, investigations

If possible: investigations on identified technical improvements.

B3: Quality management

Definition of technical requirements and procedure(s) for checking the performance of storages (materials, thermal losses, stratification, etc.).

Definition of characteristic parameters for comparison of storages (equivalent storage volume, equivalent heat capacity, usability of stored thermal energy, etc.).

B4: Knowledge transfer/dissemination

Preparation of design guidelines for seasonal storages.

Review of design/simulation tools.

Database on seasonal storages: Gather data on all large seasonal thermal storages - present via web (cooperation with the IEA ECES IA).

Subtask C: Systems - configurations, operating strategies, financing issues

The general objectives of this subtask are to:

  • Provide decision makers and planners with a good basis for choosing the right system configuration and size
  • Give decision makers and planners confidence in system performance

The specific objectives are to:

  • Provide an overview of system configurations suited for district heating and cooling
  • See the large solar systems in the context of the surrounding regional/national energy system (competition with waste heat, integration in the free market for electricity, etc.)
  • Provide a good basis for decision makers to decide on investment in large solar systems
  • Provide state of the art of simulation tools and simulation models
  • Provide general design requirements for DH networks
  • Define parameters to identify suitable existing DH networks
  • Provide models for ESCo services (contracting)
  • Provide procedures for performance guarantee - and check
  • Provide recommendations for monitoring and checking system output
  • Define criteria to adapt solar systems to the DH networks (existing and new)
  • Conduct sensitivity analysis of SDH systems, considering different parameters such as DH distribution temperature, solar fraction, storage size, load, economics
  • Provide recommendations for operating strategies
  • Provide design guidelines for "substations units" (units controlling the in- and output of heat for buildings with collectors fields on e.g., the roof)

The main activities are:

C1. Overview

C1.1.      Overview of system categories (systematic categorisation of large solar systems with respect to applications, components, component types,

C1.2.      Detailed description of (all) existing systems with (seasonal) storage and/or heat pump by each national representative

C1.3.      Updated database for all large solar systems > 0.5 MW

C2. Analysis

C2.1.       Sensitivity analysis of solar district heating systems, considering different parameters such as DH distribution temperature, solar fraction, storage size, load, economics

C2.2.      National representatives demonstrate a large solar system fit into the surrounding regional/national energy system (competition with waste heat, integration in the free market for electricity, etc.)

C2.3.      Tools for feasibility studies: overview on calculation tools providing strong and weak points and users' categories

C2.4.      Develop a dedicated pre-feasibility tool

C2.5.      Written guidelines. Examples: Economy for realised systems

C2.6.      Case studies; different application; different countries

C2.7.      Guidelines for environmental assessment

C3. Models for ESCo services

C3.1.      Financing models, financial risks, ownership, system maintenance

C3.2.      Existing examples

C3.3.      Case studies; different application; different countries

C4. Performance check/monitoring/surveillance

C4.1.      Procedures for performance check

C4.2.      Recommendation for monitoring and verification / surveillance of systems

C5. Guidelines for planning, installation, commissioning, operation

C5.1.      Give inputs for Design Handbook

C5.2.      Give inputs for handbook  in subtask D for the overall installation, commissioning and operation of SOLAR DH

C6: Guidelines for connection of decentralised solar thermal systems

Give inputs for handbook for direct and indirect connection of decentralised solar thermal systems distributed in the district heating supply network and handling both solar production and user load (e.g. in building with a large collector field on the roof.