Solar Domestic Hot Water System

Solar Domestic Hot Water System

Solar hot water system can provide up to 60 % of domestic hot water using radiation from the Sun. Because it uses indirect solar radiation, not just direct sunlight, Bosnia and Herzegovina possesses considerable potential for exploiting solar energy. Figure 1. Solar domestic hot water system The solar heating system consists of four main components: ·        The collectors ·        The solar cylinder

Solar hot water system can provide up to 60 % of domestic hot water using radiation from the Sun.

Because it uses indirect solar radiation, not just direct sunlight, Bosnia and Herzegovina possesses considerable potential for exploiting solar energy.

Figure 1. Solar domestic hot water
system

The solar heating system consists of four main components:

·        The collectors

·        The solar cylinder

·        The solar pump unit

·        The solar controller

The other components are:

·        Hot water expansion vessel

·        Solar fluid

·        Roof bracket set

·        Thermostatic mixing valve

·        Single insulated tube

The collector converts solar energy into heat and transfers the heat energy to a frost-protected solar fluid. Using the pipe system, the solar pump of the solar pump unit conveys the heat from the collector to the bivalent cylinder. They are classified into vacuum tube and flat plate collectors. Vacuum tube collectors offer the highest operating efficiency all year round and, due to their low weight and smaller dimensions, offer easier installation and handling, fig. 2a. Flat plate collectors should be used when efficiency during autumn, winter and spring is not so important and in areas where a tough collector is preferred, fig. 2b.

Figure 2.  (a) Vacuum tube collector, (b) Flat plate
collector

This twin coil unvented solar cylinder 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 two port motorised valve, fig. 3a.

The control monitors the temperature of the 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 is insufficient solar energy available the control will automatically determine when the auxiliary heat source is required.

Solar heating system must be equipped with automatic control elements because:

·        proper operation of the entire system

·        custom the default conditions, fig. 3b.

The solar pump unit, which is responsible for transporting the solar heat, fig. 3c.

                      Figure 3. (a) The solar cylinder, (b) The
solar controller, (c) The solar pump unit

Hot water expansion vessel accumulates an additional volume heat transfer medium which is formed of the same temperature expansion. The vessel requires specific performance and a special way of dimensioning, fig. 4a.

Solar fluid is a ready-mixed frost and corrosion protection agent, consisting of approximately 45% propylene glycol with anti-corrosion inhibitors and 55% water. Solar fluid is necessary controlled 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

In solar systems, the temperature in the storage tank can vary considerably, depending on the solar radiation, and can reach very high temperatures over long periods. In summer, and if there is little water usage, the hot water at the storage tank outlet can actually reach temperatures around 90º C. At these temperatures, the hot water cannot be used directly because of the danger of scalding.

The thermostatic mixing valve is used in 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 the user when there are variations in the temperature and pressure conditions of 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 Čajić/Energis

Renewable Energy Projects in Bosnia and Herzegovina

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