Renewable energies are often considered as sustainable energy sources Solar thermic systems are devices that allow you to capture and store solar energy for later use in various utilizations. Solar photovoltaic means using Sun heat to produce electricity.
Solar systems are divided into: - Solar system that works at low temperatures (up to 120 C) - Solar system that works to medium temperatures (about 500 C) - Solar system that works at high temperatures (ca. 1000 C) which is used mainly in large industrial plants.
A solar thermal system usually consists of: - One or more solar collectors which supply the carrier fluid whith the heat received fromthe Sun; - A heat exchanger where it circulates the fluid used to transfer solar energy to water; - A water storage tank.
Scheme of simple hot, domestic water heating system. 1- Solar collector 2- Pump controller, measures temperture difference between 1 and 5 3- Circulating pump 4- Expansion tank 5- Water tank with two heat exchangers 6- Other heating source (boiler, heat pump etc.)
The system can have two types of movement, natural or forced. In case of natural circulation to circulate the fluid in the system takes advantage of convection. The heated fluid in the solar panel expands and floats over the colder moving, then, in the heat exchanger placed higher than the panel giving its heat to the water.
There is no electricity consumption due to the pump. The fluid used in the primary circuit is non-toxic propylene glycol (commonly known as antifreeze) mixed with water to ensure resistance to frost. The tank is positioned higher than the solar panels to which it is connected.
In case of forced circulation of the liquid, circulation occurs with the help of a pump, which is activated only when the fluid in the panels is at a higher temperature than the water contained in the tanks.
To control the movement we use electrical sensors that compare the temperatures of fluids (thermocouple). You can also incorporate an electrical resistance to heat the water in case of insufficient or absent (at night) solar radiation.
The solar panel (also called solar collector) is a device that converts solar radiation into heat energy to be transferred to the water. 1- water tap 2- insulated container 3- warm water inlet 4- solar thermal collector 5- fresh water supply It must not be confused with the photovoltaic solar panel that is used to produce electricity.
The Radiant Panels are heating systems that use the heat from pipes located behind/under the surface of the environment to be heated. They are divided into three categories: - Radiant wall panels; - Radiant ceiling panels; - Radiant floor panels.
They are based on the circulation of hot water at low temperature (usually between 30 and 40 C) in a closed circuit that covers a large surface. There are systems that use electricity, with electric heating cables which use the principle of joule.
The possible positions of the pipes are three: - Spiral, where the feed lines are parallel to the back; - Coil, where the pipes are positioned in a zigzag; - Grid, with parallel pipes between two major collectors. In houses we use only the first two systems.
Compared to traditional heating elements, the floor radiant panels have the following advantages: - Less operating costs : the system is at a low temperature, about 28-40 C (70-80 C in common radiators); - It 's possible to connect the heating systems with a solar panel system, so reducing heating costs; - The costs and fuel consumption may be reduced by connecting the system to a modern condensing boiler.
solar thermic system As for the electrical heatings, the advantage is that they do not need a boiler, a flue and distribution pipes and have no maintenance; The economic advantages are to be evaluated, though they often are advantageous compared to traditional systems.
solar thermic system The disadvantages to consider are: - Thickness of the floor: the radiant panels require an additional thickness of 7-10 cm on the floor; - High costs of implementation; - The need for careful and personalized planning: floor surface temperatures too high, are unpleasant (discomfort).