Renewable Energy Technology 3(2+1)

Lesson 19. Maintenance of Solar Passive Heating Devices

1. Cleaning of transmitting glass

The transparent glass or cove of the solar heating devices should be clear from dust.  So periodical cleaning of glasses are required so as to get maximum transmittance from the glass.  Monthly cleaning may be done.  The frequency of cleaning is based on the environment.  If the surrounding is dusty environment the cleaning frequency has to be increased.  Water washing gives better results.  Occasional soap water washing increases the overall performance of the gadget.

2. Checking up of leakages in fluid passages

The fluid passages such as pipes, pipe joints, bends, ducts, inlet and outlet joints etc. has to be checked periodically for leakages.  If any leakage is found immediately has to be rectified, otherwise the thermal energy loss will be very high and also, the output energy will be reduced.  This will lead to lowering of the performance of the solar thermal device.

3. Scaling removal

If the water used in the solar water heater is of salty in nature, the salt deposition has to be removed periodically using suitable acids.  The salt deposition will reduce the heat transfer coefficient of the pipe metal and there by decrease the heat transfer from the collector to circulating water. 

4. Glass damage

The damaged and broken glasses have to be removed for better transmittance of the transparent surfaces.

5. Insulation

The insulation of the solar heating device has to be checked periodically.  Damages in the insulation will cause more heat loss from the collector area.

6. Absorber coating

The paint coating of the absorber plate has significant role in the performance of the collector.  Selective coatings have higher absorptance and needs lesser maintenance.  However, the absorbers have to be painted every 1-3 years to maintain the absorptance coefficient.

7. Pump performance

If solar water heaters are used, the flow rate plays major role in deciding the performance of the solar water heater.  The flow rate will be maintained by the either natural circulation or using pumps.  If pumping systems are used, the performance of the pump in terms of out put (mass flow rate) has to be assessed to maintain the required flow of fluid in the solar collectors.

8. Blower performance

In solar hot air driers, the generated hot air quantity, heat content, temperature etc. are decided based on the flow of air through the solar collectors.  This can be optimized to harness maximum quantity of thermal energy from solar radiation.  For better performance of the hot air system, the blower has to be maintained properly so as to supply the required quantity of air to the solar collectors.