Solar Collectors

Flat Plate Solar Collector for Medium Temperature Applications

Within the framework of “Thermal and fluid dynamic optimization of thermal system and equipment”,
CTTC works actively on the development of flat plate solar collectors with transparent insulation materials (TIM) and ventilation channels.

The research approach is based on:

  • Optimization and design process by means of high-level simulation tools (TermoFluids, NEST)
  • Construction and detailed testing of the new prototypes in CTTC SOLAR CELL

Fig. 1: A flat plate solar collector during stagnation condition test at the CTTC SOLAR CELL

The use of transparent insulation materials (TIM)  improve the performance of  flat plate solar collectors while maintaining costs low. Within the actual research projects on solar collectors in CTTC can be mentioned:

  • Development of advanced flat plate solar collector (FPSC) with honeycomb transparent insulation materials (TIM) and overheating protection system which consists on a ventilation channel inserted at the rear top of the collector allowing to protect the collector from stagnation conditions. The collector can be considered promising as it is expected an increase in its thermal performance  and could be destined for industrial applications which require heat at a temperature level (80-120 ºC).
  • Development of Integrated Collector-Storage (ICS) systems with TIM. ICS systems are considered to be promising for increasing the economic feasibility of low temperature solar systems especially for application in locations with favorable weather conditions (temperature demand in the range of 45-60 ºC). An ICS system combines collection and storage of thermal energy in a single unit. The advantage of simplicity, both in construction and in operation, the low costs, its manufacturing does not require high technology and its installation costs is low. The use of  transparent insulation at the top of the collector reduces heat losses during night or periods of insufficient solar radiation.

Fig. 2: An ICS at the stand test of the CTTC

Fig. 3: Instantaneous temperature and velocity maps for open channel

Fig. 4: Instantaneous temperature and velocity maps for TIM and air gap.



CTTC SOLAR CELL is the experimental unit where thermal and fluid dynamic behavior of the flat plate solar collectors are tested in order to validate the high-level simulation tools developed in the CTTC.  The pressurized water collector test bank of the CTTC SOLAR CELL allows performing tests
up to 150 ºC and 8 bars. Its versatile design permits performing different types of tests:

  • Outdoor steady state efficiency test
  • Determination of the effective thermal capacity and the time constant of a collector
  • Collector incident angle modifier
  • Determination of the pressure drop across the collector
  • Heat loss coefficient test
  • Stagnation condition test

Collectors up to 10 m² of absorber area can be tested in serial or parallel configurations. The site is equipped with a Meteorological Station where temperature, pressure, humidity, liquid precipitation, total and diffuse radiation, wind velocity and direction data are registered by means of accurate sensors. 

Fig. 5: A flat plate solar collector during the steady state efficiency test at the CTTC SOLAR CELL

CTTC SOLAR CELL is regularly used as an experimental facility by the following undergraduate and graduate educational programs:

-Bachelor's degree in Mechanical Engineering (UPC)
-Master's degree in Energy Engineering (UPC)
-Master in Environmental Pathways for Sustainable Energy Systems, SELECT (coordinated by KTH)

-Master in Renewable Energy, RenE (coordinated by UPC)
-Thermal Engineering Doctorate Program (UPC)

CTTC SOLAR CELL has been used in the following financially supported research projects:

  • Research Project E00472 ref. JOR3-CT98-7002, STATIC.
    Title: "Stagnation Proof Transparently Insulated Flat Plate Solar Collector"
  • Research Project C3770.
    Title: "Simulación numérica de instalaciones de energía solar térmica con colectores planos con superficie transparente aislante y con superficies selectivas de alta eficiencia."
  • Research Project C3521.
    Title: "Desarollo de códigos numéricos para la simulación del comportamiento termo-fluídico de tanques de acumulación de energía térmica. Validación experimental. Aplicación al diseño de equipos y a la predicción de su comportamiento en condiciones reales de trabajo."
  • Research Project C3520.
    Title: "Creación de una infraestructura numérica y experimental para el diseño y optimización de colectores solares planos."
  • Research Project C3771.
    Title: "Adecuación del código AGLA de simulación de fachadas multifuncionales ventiladas a la simulación y diseño de colectores solares planos de aire integrados en las fachadas y/o techos de edificios."
  • Research Project R00472 ref. TIC99-1388-CE.
    Title: "Special action projects support STATIC, ACABMA and FATHERP."
  • Research Project E0495 ref. JOE3-CT98-7014.
    Title: "Supervision System for Solar Processes-S3."
  • Research Project J05157 ref. 1999PIRA-00189
    Title: "Equipamiento para el ensayo e investigación de sistemas solares activos y pasivos."
  • Research Project E00692 ref. CRAFT-1999-70436, ARTISC.
    Title: "Refrigeration, Heating and Air-Conditioning Using an Absorption Refrigeration System Heated by Transparently Insulated Flat Plate Solar Collectors"
  • Research Project E00694 ref. ENK6-CT-2001-30008, STATIC-2.
    Title: "Stagnation Proof Transparently Insulated Flat Plate Solar Collector-2"
  • Research Project E00752 ref. CRAFT-1999-70604, OPICS.
    Title: "Optimized Integrated Collector Storage: Low-Cost Solar Thermal Systems for Houses and Offices"
  • Research Project C05361.
    Title: "Development of high efficiency and low cost flat plate collectors for medium temperature applications (DECOSOL)."
  • Research Project E00766 ref. CRAFT-1999-72476, COMPACT.
    Title: "Low-Cost Compacts Solar Heaters Made of Plastic Materials and Composites"
  • Research Project E00765 ref. CRAFT-1999-7275, HYDRA.
    Title: "Hybrid latent/sensible compact storage Devices for combined thermal solar energy applications: Refrigeration, heating and Air-conditioning"
  • Research Project CTTV92 ref. VALTEC08-1-0018.
    Title: “Solar collectors with TIM and ventilation channels”
Fig. 6: Detail of the meteorologic station of the CTTC SOLAR CELL.           
Fig. 7: Hot and cold tanks of the pressurized water collector test bank