Solar hot water system can provide up to 60 % of domestic hot water using radiation from the Sun. BecauseÂ it uses indirect solar radiation, not just direct sunlight, Bosnia andÂ Herzegovina possesses considerable potential for exploiting solar energy. Figure 1. Solar domestic hot water system The solar heating system consists ofÂ four main components: Â·Â Â Â Â Â Â Â Â TheÂ collectors Â·Â Â Â Â Â Â Â Â TheÂ solar cylinder
Solar hot water system can provide up to 60 % of domestic hot water using radiation from the Sun.
BecauseÂ it uses indirect solar radiation, not just direct sunlight, Bosnia andÂ Herzegovina possesses considerable potential for exploiting solar energy.
Figure 1. Solar domestic hot water
The solar heating system consists ofÂ four main components:
Â·Â Â Â Â Â Â Â Â TheÂ collectors
Â·Â Â Â Â Â Â Â Â TheÂ solar cylinder
Â·Â Â Â Â Â Â Â Â TheÂ solar pump unit
Â·Â Â Â Â Â Â Â Â TheÂ solar controller
The other components are:
Â·Â Â Â Â Â Â Â Â HotÂ water expansion vessel
Â·Â Â Â Â Â Â Â Â SolarÂ fluid
Â·Â Â Â Â Â Â Â Â RoofÂ bracket set
Â·Â Â Â Â Â Â Â Â ThermostaticÂ mixing valve
Â·Â Â Â Â Â Â Â Â SingleÂ insulated tube
The collectorÂ converts solar energy into heatÂ and transfers the heat energy to a frost-protected solar fluid. Using the pipeÂ system, the solar pump of the solar pump unit conveys the heat from theÂ collector to the bivalent cylinder. They are classified into vacuum tube andÂ flat plate collectors. Vacuum tube collectors offer the highest operatingÂ efficiency all year round and, due to their low weight and smaller dimensions,Â offer easier installation and handling, fig. 2a. Flat plate collectors shouldÂ be used when efficiency during autumn, winter and spring is not so importantÂ and in areas where a tough collector is preferred, fig. 2b.
Figure 2. Â (a) Vacuum tube collector, (b) Flat plate
ThisÂ twin coil unvented solar cylinderÂ manufactured from stainless steel is designed for use with a boiler to provide
auxiliary hot water during periods of low solar gain. The cylinder has a twoÂ port motorised valve, fig. 3a.
The control monitors the temperature of theÂ collector and of the cylinder. When sufficient solar energy is available the control switches on the solar pump unit to charge the cylinder. If there isÂ insufficient solar energy available the control will automatically determineÂ when the auxiliary heat source is required.
Solar heating system must be equippedÂ with automatic control elements because:
Â·Â Â Â Â Â Â Â Â properÂ operation of the entire system
Â·Â Â Â Â Â Â Â Â customÂ the default conditions, fig. 3b.
The solar pump unit, which is responsible for transportingÂ the solar heat, fig. 3c.
Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Figure 3. (a) The solar cylinder, (b) The
solar controller, (c) The solar pump unit
Hot water expansionÂ vessel accumulates anÂ additional volume heat transfer medium which is formed of the same temperatureÂ expansion. The vessel requires specific performance and a special way ofÂ dimensioning, fig. 4a.
Solar fluid is a ready-mixed frost and corrosionÂ protection agent, consisting of approximately 45% propylene glycol withÂ anti-corrosion inhibitors and 55% water. Solar fluid is necessary controlledÂ every two years and if necessary to make a replacement, fig. 4b.
Figure 4. (a) Hot water expansion
vessel, (b) Solar fluid, (c) Roof bracket set
InÂ solar systems, the temperature in the storage tank can vary considerably,Â depending on the solar radiation, and can reach very high temperatures overÂ long periods. In summer, and if there is little water usage, the hot water atÂ the storage tank outlet can actually reach temperatures around 90Âº C. At theseÂ temperatures, the hot water cannot be used directly because of the danger ofÂ scalding.
The thermostatic mixingÂ valve is used inÂ systems for scald protection in the production of domestic hot water. It is
designed to maintain the set temperature of the mixed water supplied to theÂ user when there are variations in the temperature and pressure conditions ofÂ the incoming hot and cold water. It can function continuously at the high
temperatures of the incoming hot water from the solar storage tank, fig. 5.
Figure 5. Thermostatic mixing valve
Author: Mirnesa ÄŒajiÄ‡/Energis