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:
C1.1. 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
C2.1. 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.