Page 125 - New Trends in Green Construction

PHOTOVOLTAIC TECHNOLOGIES APPLIED TO WATER HEATING SYSTEMS
José Ramírez-Faz, Marta M. Varo-Martínez, Francisco J. Casares, Luis Cámara
Keywords: Photovoltaic, Water Heating, Sustainability 1. Introduction
Problems related to the consumption of fossil or nuclear energy have made necessary to change the energy model. In this line, in recent years the use of renewable energy is being promoted. Thus, for example, research into photovoltaic (PV) technology for the harnessing of solar radiation has led to a greater conversion efficiency in cells. As a consequence, this technology, which allows efficient and clean direct generation of electric power, has reduced its costs, achieving in 2013 parity or cost equality with conventional supply.
Regarding the systems of water heating, the scheme of a conventional solar installation is based on the use of solar thermal collectors, frequently located on roofs, to which the heat transfer fluid (commonly water) is conducted in the central hours of the day. The plumbing installation that completes the system can be complex, depending on the geometry of the building and, the more complex the installation is, the greater the maintenance needs of the system. On the other hand, in summer, solar radiation is excessive, so traditional installations must be covered to avoid damage and breakdowns.
However, in the new scenario of photovoltaic costs, the traditional system, previously described, begins to compete at a disadvantage with new water heating systems, based on photovoltaic electricity. These devices are composed of the PV solar panels, the water tank, and the heater with resistance. Specifically, the heating of the water is performed by means of a resistance and an electronic control system.
Thus, the advantages of these PV water heating systems are:
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The installation with PV panels is less complex and cheaper than traditional solar thermal installations.
The PV system would be easy to integrate into almost all the previous installations.
Contrary to conventional thermal heater systems, the elements of the installation do not need maintenance.
In this type of installations there would not be quite high temperatures that shorten the life of the installation.
The surplus of PV electricity production in summer could be used in other needs of the buildings (such as air conditioning) or could be discharged to the electricity grid in those cases in which the legal framework of the country allows it.
these reasons, architects and technicians are beginning to reconsider the traditional solar
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New Trends in Green Construction