Objective
The main aim of this project was the monitoring of solar systems object of a Guarantee of Results ( Performance ). The project was divided in two phases which were developed independently:
Phase A: - Development of practical specifications for design and installation of solar systems. This phase included the elaboration of a manual for Water Heating Solar Systems Design.
Phase B: - Monitoring of a solar system. The methodology for monitoring included long distance transmittance of data ( telemonitoring ) allowing system follow up operation in a centralized location.
The main aim of this project was the monitoring of solar systems object of a Guarantee of Results ( Performance ). The project was divided in two phases which were developed independently:
Phase A:
Elaboration of a manual for Water Heating Solar System conception and Design.
This manual entitled ' Water Heating Solar Systems' includes an identification of the most important characteristics for the design and installation of solar thermal systems, as well as, a design method (and software) for the design of these type of systems. It is organized in three volumes:
- 'General principles for conception, design and monitoring'
- 'Guide to the design method'
- 'Programme SolTerm - User's Guide'. The Solterm Programme consists of a design calculation method for Water Heating Solar Systems. This method needs as input for calculation only average values of the local climatological parameters and it can be used not only to design the system but also as a way of verification of the measured results during monitoring.
Phase B - System telemonitoring
The solar thermal system monitored was installed in a new school building for impaired children, located in Lisbon, 15 km away from INETI. The system is a forced circulation, indirect, preheat system with a collector area of 48.4 m2 and with a solar storage volume of 2200 litter.
A complete monitoring equipment was installed. The data acquisition system is able to store data for a long period (>> 30 days). To collect this data at INETI, the system is connected to an external modem and to a telephone line. At INETI a computer with an internal modem is also connected to a telephone line. Using the data acquisition system software (Delta-T Logger, 1993) it is possible to collect the stored data and to have direct access to the measuring equipment. The data collected is then processed using a worksheet to represent graphically the different measured values and to calculate the energy collected by the solar system and the energy delivered to the load, among other quantities of interest in the evaluation of the solar system.
The system was telemonitored since the end of 1994 until December 1995. The results obtained show that the system is performing according to what is expected, although the loads observed are lower than those used for system design. A comparison of measured and calculated system performance, using the simplified method above referred, was done. The results obtained show reasonable agreement and a consistent over prediction, which can be explained by the fact that the load volume was always smaller than the storage volume (for some months of the order of a third of the expected load). In this conditions the calculation method is far from its application conditions. However, this simplified calculation method can be used as a basis for checking the 'Guarantee of Results' presented by the installer if the expected and observed load are close.
A complete definition of system parameters should be given by the installer and, using these parameters in the calculation method, comparison with measured values is possible. Analysis of the differences observed establishes whether the system is working according to the Guarantee of Results presented.
A minimum number of measurements needed to check a Solar System provided with a Guarantee of Results, was proposed. The development of lower cost equipment is found to be very important to spread out the monitoring of solar systems as support of the Guarantee of Results.
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1699 LISBOA
Portugal